HomeMy WebLinkAbout111825MassAudubonNarrative (2) (1)Notice of Intent November 18, 2025
Barnstable Great Marsh Sanctuary
Salt Marsh Restoration
Applicant:
Mass Audubon
137 Bartlett Road
Plymouth MA 02360
Prepared by:
Rimmer Environmental Consulting, LLC EA Engineering, Science, &
57 Boston Road Technology, Inc.
Newbury, MA 01951 301 Metro Center Blvd., Suite 102
Warwick, RI 02886
Northeast Wetland Restoration
17 Keay Road
Berwick, ME 03901
Table of Contents
Distribution List .............................................................................................................................................................. 4
1.0 Executive Summary ........................................................................................................................................... 7
2.0 Review Process .................................................................................................................................................. 8
3.0 Introduction and Project Purpose .................................................................................................................... 10
4.0 Background and Need ..................................................................................................................................... 10
5.0 Marsh Changes ................................................................................................................................................ 11
6.0 Existing Conditions .......................................................................................................................................... 16
6.1 Hydrology ........................................................................................................................................................ 17
6.2 Vegetation ....................................................................................................................................................... 18
6.3 Sediment Supply .............................................................................................................................................. 20
6.4 Pannes and Pools............................................................................................................................................. 20
6.5 Crab Burrow Density........................................................................................................................................ 21
6.6 Rare Species .................................................................................................................................................... 22
6.7 Area of Critical Environmental Concern ........................................................................................................... 23
7.0 Sea Level Rise, Metonic Cycle and need for Accelerated Restoration .............................................................. 24
8.0 Restoration Design Process .............................................................................................................................. 25
9.0 Restoration Methods ....................................................................................................................................... 25
9.1 Addressing Oxidation Subsidence through Ditch Remediation: ............................................................................. 26
9.2 Addressing Waterlogged Subsidence through Runnels .......................................................................................... 29
9.3 Restoring Rare Species Habitat through Structured Micro-topography ................................................................. 33
10. Project Impacts ................................................................................................................................................ 37
10.1 Quantification of treatments .................................................................................................................................. 37
10.2 Ditch Remediation Impacts .......................................................................................................................................... 37
10.3 Runnel Impacts ...................................................................................................................................................... 38
10.4 Microtopography Mounds Impacts .......................................................................................................................... 38
10.5 Hydrologic Changes ................................................................................................................................................ 39
10.6 Vegetation Changes ................................................................................................................................................ 39
10.7 Effects on Permanent Pools and Submerged Aquatic Vegetation .......................................................................... 40
10.8 Rare species impacts............................................................................................................................................... 40
11. Best Management Practices ............................................................................................................................ 42
12. Alternatives Analysis ........................................................................................................................................ 43
12.1 Alternative 1 – Proposed Action ............................................................................................................................. 43
12.2 Alternative 2 –Ditch Remediation Only Alternative ........................................................................................... 43
12.3 Alternative 3 –No Microtopography Alternative ................................................................................................... 43
12.4 Alternative 4 - No Action Alternative ...................................................................................................................... 44
13. Pre and Post Restoration Data Collection and Monitoring ................................................................................ 45
13.1 Baseline and Post-Construction Monitoring ........................................................................................................... 45
13.2 Construction Period Monitoring ............................................................................................................................. 48
13.3 Saltmarsh Sparrow Monitoring ................................................................................................................................ 48
14. Corrective Action Plan .................................................................................................................................... 49
15. Proposed Priority 2 Pilot Program ........................................................................................................................ 52
16. Proposed Contracting and Restoration Timeline and Logistics .......................................................................... 57
17. Quality Control and Assurance of Contracted Work .......................................................................................... 62
18. Compliance with MassDEP Salt Marsh Restoration Guidance .......................................................................... 62
References.................................................................................................................................................................... 72
Appendix 1 Oxidation Subsidence and Water-logged Subsidence Trajectories ....................................................... 77
Appendix 2 APCC Monitoring Report .................................................................................................................... 77
Appendix 3 EA Technical Memorandum ................................................................................................................ 77
Appendix 4 SMARTeam Restoration Design Steps ................................................................................................. 77
Distribution List
DEP Southeast Regional Office edep filing and
20 Riverside Dr SERO_NOI@mass.gov
Lakeville, MA 02347
Natural Heritage and Endangered Species Program mesareview@mass.gov
Division of Fisheries and Wildlife
1 Rabbit Hill Road
Westborough MA
Division of Marine Fisheries – South Shore DMF.EnvReview-South@mass.gov
Attn.: Env Reviewer
836 South Rodney French Blvd
New Bedford MA 02744
Town of Barnstable Conservation Division Office Kimberly.Cavanaugh@town.barnstable.ma.us
230 South Street Edwin.Hoopes@town.barnstable.ma.us
Hyannis MA 02601
Town of Barnstable Shellfish Biologist shellfishNOI@town.barnstable.ma.us
c/o Town of Barnstable Natural Resources conservationprojects@town.barnstable.ma.us
1189 Phinney’s Ln
Centerville, MA 02632
Abutters within 100 feet of project site
See attached list
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1.0 Executive Summary
The project involves the ecological restoration of approximately 76.5 acres of salt marsh owned and
stewarded by Mass Audubon as part of the Barnstable Great Marsh Sanctuary. The salt marsh is
damaged from on-going stressors such as accelerating sea level rise, and degraded from chronic, legacy
impacts of prior agricultural activities. Ecological restoration is required to address past impacts,
establish a positive healing trajectory, and build resilience against increasing climate change impacts.
Specific restoration actions proposed include ditch remediation, construction of runnels and creation of
marsh habitat mounds – all designed and proposed to be performed according to state technical
guidance for these activities.
Mass Audubon received funding for this project from the Mass Department of Fish and Game (“DFG”),
as sponsor of an in-lieu fee program (“ILFP”) for mitigation required by the US Army Corps of Engineers
(“USACE”). The need for this work was identified in 2020 following a vulnerability assessment of its
coastal properties conducted by Mass Audubon. The assessment indicated the site provides some
resilience against sea-level rise due to elevation capital and high salt marsh migration potential but also
exhibits signs of stress including pool formation and vegetation loss. As with nearly all salt marshes in
the Northeast, the project site contains evidence of an agricultural legacy including embankments and
ditches as well as mosquito control practices which have impacted the natural hydrology of the marsh.
In 2022, EA Engineering, Science and Technology, Inc. (“EA”) prepared a restoration reconnaissance
report for the site which identified ditch remediation and runnels as key techniques to restore hydrology
and improve marsh function. An initial design for the restoration of primary tidal hydrology for this site
was completed in 2023 by Northeast Wetland Restoration (“NWR”) which included identifying an
extensive network of early and late period agricultural embankments, ditching infrastructure and
existing tidal network as well as identifying the proposed locations of runnels and ditch remediation.
Using state-approved restoration methods, the project aims to restore single channel tidal hydrology to
avoid loss of marsh peat due to subsidence and to boost biomass production, reverse vegetation loss,
preserve high marsh vegetation, and increase accretion rates. It also addresses conservation needs for
at-risk species like saltmarsh sparrows, which are a species of Special Concern under the Massachusetts
Endangered Species Act (MESA) and only nest in high marsh habitats.
The primary nature-based restoration techniques involve ditch remediation, construction of runnels,
and beneficial re-use of excavated material to construct micro-topography habitat mounds. These
techniques are similar to that proposed by U.S. Fish and Wildlife Service (USFWS) for their 1450-acre
project in Newbury, Ipswich and Rowley, currently underway (see EOEEA # 16714), The Trustees of
Reservations (“The Trustees”) have also proposed and utilized these techniques for their Phase III
projects in Essex, and Ipswich covering 1,006 acres in final permitting (See EEOEA #16838), and their
Phase II in Newbury, Ipswich and Essex covering 385 acres (EOEEA #16033) and nearing completion.
The process of ditch remediation involves the identification of ditches within the larger existing ditch
network that are determined to be non-essential and interfere with maintaining primary marsh
hydrology (also referred to as primary channel hydrology). The elimination of ditches serves to minimize
peat oxidation caused by excess drainage and exposure of ditch banks, which leads to harmful
subsidence adjacent to ditches. Once these ditches have been identified, the ditch treatment involves
hand-mowing a 20-foot wide swath of salt marsh grasses parallel to the treatment ditches, and then
placement of this “hay” into the ditch bottoms. The hay is placed in layers throughout the ditch at an
include with the headwater end of the ditch being the highest elevation. The mowed “hay” is then
secured with twine and wood stakes to the ditch bottom. The hay slows tidal flow within the ditch,
allowing sediment to settle out of the tidal water column and over time raise the ditch bottom, creating
a substrate for establishment of native salt marsh vegetation. Ensuring an incline throughout the treated
ditch ensures consistent drainage as the ditch is restoring and improves sediment distribution. Four to
five treatments of hay spaced 6-months apart may be required for the ditch bottom to gain enough
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elevation to revegetate and stop peat oxidation by raising groundwater elevations. Successfully healed
ditches revegetate and contain a ditch bottom within 8-9 inches (20 cm) of the marsh surface.
The process of runnel construction addresses areas experiencing water-logged subsidence due to loss of
vegetation occurring from over saturation of the root zone. This technique involves construction of
shallow swales, 30-36 inches wide and 8-12 inches deep. These swales are carefully located within the
existing tidal channel framework to connect to existing primary channels so that primary channel
hydrology can be restored. The process lowers groundwater 6-8 inches below the surface in the vicinity
of the runnel to provide optimum growing conditions for salt marsh plants. The runnels also provide an
opportunity for the area to naturally flood and drain in response to tidal flow rather than water
remaining on the marsh surface between tide cycles. Material excavated during runnel construction is
then beneficially re-used to create structured micro- topography and high marsh habitat for the benefit
of state-listed salt marsh sparrow (Ammospiza caudacuta) a species which nests exclusively in high
marsh and is particularly at risk due to sea level rise.
The runnels and ditch remediation techniques work in concert to restore a hydrological channel network
that is in equilibrium with the volume of flooding and ebbing tides that move through each channel
network. This tiered hydrological network is adaptable to increasing inundation and storm impacts,
increasing the resiliency of the salt marsh to future worsening climate change stressors.
The project proposes a total of 15,072 linear feet of ditch remediation and 3,384 linear feet of runnels,
with an estimated 2,000 square feet (150 cy) of constructed high marsh micro-habitat mounds.
Short-term, temporary impacts to marsh are avoided and minimized during restoration activities
through the use of low ground pressure equipment and construction mats, operating primarily during
neap tide cycles, timing activities according to any restrictions established by regulating agencies, and
minimizing staging and equipment use on the marsh.
Pre-restoration monitoring of the site has been conducted by the Association to Preserve Cape Cod
(“APCC”) in 2023 and 2024, and included surface and groundwater monitoring, vegetation community
mapping, and studies of marsh elevation and accretion rates (Mora et al. 2024). EA also conducted re-
restoration data collection pursuant to state guidance which included a LiDAR survey of the project area
to assist in the development of the attached site plans to identify the locations of pannes and pools,
best suited locations for additional vegetation surveys and a limited on-the-ground field survey of a
limited number of proposed runnel locations. Post-restoration monitoring will be conducted by Mass
Audubon and project partners using similar methods for five years following initial restoration and
following the newly developed MassMarsh Monitoring Standard Operations Procedures (“SOPs”).
Project success will be evaluated based upon specific vegetative, hydrologic and elevational success
criteria described in Section 15 below. A Corrective Action Plan in Section 15 describes recommended
steps for adaptive management and addressing possible unintended outcomes.
2.0 Review Process
At the time of filing, the project is still completing MEPA review. In addition to MEPA the following
approvals are required for this project:
• Order of Conditions under the Mass. Wetlands Protection Act from the Town of Barnstable
Conservation Commission. As recommended by MassDEP, it will be filed as an Ecological
Restoration Limited Project, as described in 310 CMR 10.24(4).
• Town of Barnstable Order of Conditions under local bylaw
• MassDEP 401 Water Quality Certificate
• MassDEP Chapter 91 Waterways License (Water Dependent Use)
• MESA review by Massachusetts Division of Fisheries and Wildlife – (“Mass Wildlife”) NHESP
• Massachusetts Division of Marine Fisheries Review
• Section 404 USACE Pre-Construction Notification
• Massachusetts Coastal Zone Management Consistency Review
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In addition, Mass Audubon will submit a mitigation project plan including a long-term management plan
for review by USACE and the ILFP Interagency Review Team to meet the requirements of the ILFP funding
award from the Massachusetts Division of Fish and Game.
The project is subject to the June 18, 2024, Wetlands Program Guidelines under the Mass. Wetlands
Protection Act and Water Quality Certification for Salt Marsh Restoration Techniques prepared by
MassDEP 2024-08-20_GuidanceSaltMarshRestoration-Runnels.pdf. The project has been designed in
compliance with this guidance as described in Section 17 below.
The project has been filed as an Ecological Restoration Limited Project under 310 CMR 10.24 (8)(e) (3) as
recommended by DEP for other similar projects recently permitted. Work is located entirely within Salt
Marsh resources. Section 10 below provides a detailed description of temporary impacts required for
the completion of this work. Section 11 describes mitigation measures to minimize the potential for
unintended impacts during restoration activities. Equipment and material access is proposed via the
existing trail system and all equipment and materials will be stored in upland areas when not in use.
The project is within Priority Habitat as determined by the Mass. Natural Heritage and Endangered
Species Program. Early review by NHESP under the MEPA process indicates that the project will not be
subject to the Mass. Endangered Species Act (MESA) provided an approved Habitat Management Plan is
received describing measures to mitigate potential impacts to rare species during implementation of
restoration methods. This habitat management plan is currently being prepared by Mass Audubon.
As work is proposed within tidal waters, this NOI is also being filed with the Mass. Division of Marine
Fisheries for review and comment.
As required by the Town of Barnstable Conservation Commission, copies of this NOI are also being filed
with the Town Shellfish Biologist.
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3.0 Introduction and Project Purpose
From 2014 to the present, scientists and restoration experts from Mass Audubon, USFWS and other
partnering organizations have researched, implemented and tested various restoration techniques to
address specific symptoms of salt marsh degradation which have led to loss of vegetation and marsh
elevation, believed to be caused by legacy agricultural and mosquito control infrastructure, which is now
being exacerbated by sea level rise. Various projects were piloted at a smaller scale to better
understand the underlying cause of the changes and to test innovative, low-cost, low-impact, nature-
based techniques to restore marsh surface hydrology. These various techniques have included
runneling, ditch plug removal, creation of microtopography islands, and ditch remediation.
These integrated restoration techniques have been applied or are currently being implemented in other
New England marshes since 2019 or earlier. Although these restoration methods are relatively recent,
they are already demonstrating improvements to vegetative productivity of the treated marshes with
minimal if any adverse effects. This project closely mirrors and learns from restoration conducted at these
other locations.
Mass Audubon and its partners propose to expand upon these earlier efforts by applying the same
restoration techniques to 76.5 acres of salt marsh within Mass Audubon’s Barnstable Great Marsh
(“BGM”) Wildlife Sanctuary in the Town of Barnstable. Like the other Massachusetts restoration sites,
this site is located within an Area of Critical Environmental Concern (“ACEC”). The goals are similar: to
address the historically human-altered marsh hydrology by restoring a more natural ebb and flood cycle
to the marsh, enhancing its ability to adjust to increasing flooding due to storms and sea level rise.
Specifically, the project aims to maintain and encourage existing high marsh, reduce conversion of high
marsh to low marsh, promote revegetation in areas with vegetation dieback, avoid loss of marsh peat
due to subsidence, and increase accretion rates to build marsh surface elevation. An additional project
purpose is to address critical conservation needs for at-risk species like saltmarsh sparrows, which nest
exclusively in high marsh habitat (Atlantic Coast Joint Venture, 2019; Greenlaw et al., 2020; Meiman &
Elphick, 2012). BGM is identified as Priority Habitat for this species (ACJV, 2022). As such, this project is
both a tidal restoration and rare species habitat restoration.
4.0 Background and Need
More than half the salt marsh habitat in the U.S. has been lost, primarily to human alteration (Kennish,
2001). The remainder was also subject to human alteration and degradation through filling, ditching,
diking, or draining for development, agriculture, and mosquito control, which continues to affect current
hydrology (Atlantic Coast Joint Venture, 2019). In the 1600s and 1700s, farmers developed networks of
narrow ditches to increase drainage and enhance production of Spartina patens (S. patens) otherwise
known as “salt marsh hay,” as well as other agricultural products. Salt marsh farming practices also
included construction of low embankments, designed to limit the amount of tidal flooding on the marsh
platform and further increase crop production (Smith et al., 1989), (Adamowicz et al., 2020). The 1900s
ushered in the era of mosquito control which included more extensive, high-density ditching intended to
drain the marsh at a faster rate to limit mosquito breeding.
Marsh alteration was particularly extensive in the northeastern U.S., where 90% of salt marshes were
ditched by 1940 (Tonjes, 2013). In recent years, sea level rise has increased the frequency and extent of
tidal flooding in salt marshes (Hill & Anisfeld, 2015). Legacy ditches and embankments have
compounded the issue by retaining excess water on the marsh surface, thereby causing vegetation
dieback and reducing accretion rates (Adamowicz et al., 2020). Accretion is critical for salt marshes to
keep pace with sea level rise (“SLR”), but sediment is also a limited commodity (Langston et al., 2020,
Raposa et al., 2017). The Saltmarsh Sparrow (Ammospiza caudacuta), listed as “Special Concern” in
Massachusetts, is an example of a species that relies on the ability of salt marshes to accrete and
maintain habitat. The population of these birds has declined more than 80% over 15 years to less than
30,000 individuals. This decline has been linked to the degradation of high marsh habitat, an issue that
will be exacerbated by SLR. To prevent extinction and stabilize the population, the Atlantic Coast Joint
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Venture (ACJV)and partners have determined that by 2030, a minimum of 1,203 acres of high-quality
high habitat is needed in Massachusetts. The project site has been identified by ACJV as a priority site
for the saltmarsh sparrow and will be an important component to this species’ recovery.
5.0 Marsh Changes
As stated above, over the past decade, researchers and land managers have observed accelerating
changes in the northeast marshes. These include expanding pools and pannes (water-retaining
depressions), vegetation dieback, extensive loss of the marsh platform, and rapid conversion of high
marsh vegetation to low form Spartina alterniflora (S. alterniflora). Collaborators discussed these
changes and their underlying causes at a workshop held at Parker River NWR in 2017 (USFWS, 2017).
Below is a summary of some of the observations and concepts discussed during the workshop.
The Great Marsh Salt Marsh Adaptation and Resliency Team (“SMARTeam”) developed conceptual
drawings (Figures 5.1-5.5). This conceptual understanding is the basis of the proposed restoration
project. The process is sometimes referred to as secondary succession (secondary to the original
disturbance from agricultural alterations).
Unaltered salt marshes contain numerous natural, sinuous tidal creeks. As high tide overtops the creeks,
it floods the surface of the adjacent marsh. As the tide recedes, the ebbing water drains into the lowest
order creeks, maintaining the channel geomorphology. In between these creek networks are higher
elevation points. These high points make up the boundaries of individual sub-tidesheds, a concept
similar to a sub-watershed in an inland setting.
Fig. 5.1: Unaltered marsh tidal network
The construction of agricultural ditches and embankments disrupted and replaced natural
creek hydrology. Man-made ditches were constructed at higher density than natural
creeks, causing extensive aeration of root zone and leading to loss of elevation through
accelerated decomposition along the marsh adjacent to the ditches. Although marsh
grasses such as S. patens may persist at these lower elevations, these artificially oxidized
marshes cannot keep up with SLR and significant vegetation changes are occurring.
5.2: Agricultural ditches constructed
The pattern of marsh elevation subsidence due to aeration or oxidation of root zones
within the peat occurs when the sides of the ditches are exposed to air. This process is
referred to as the Oxidation Subsidence Trajectory (see Appendix 1). Wright (2012) found
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that high density ditched marshes are 20-25 cm lower in elevation compared to low
density ditch areas. This finding is collaborated through monitoring pilot studies (Burdick
et al. 2017, Dinunzio et al. 2023).
Fig. 5.3: Clogging of human-made ditches from lack maintenance
.
Fig. 5.4: Mega-pool formation
With the cessation of farming and ditch network maintenance, many ditches have begun to revegetate
naturally over time, but they do so unevenly, which causes clogs to form, which in turn impedes tidal
flows. Clogging that occurs in the middle of the ditch forms obstructions and causes water to impound
on the marsh surface, preventing it from draining on the ebbing tide as it should naturally. The lack of
ditch maintenance in the last 50+ years has resulted in a pattern of ditch clogging and accelerated pool
formation behind the clogs. This pattern of pool development expands and eventually results in
interconnected mega-pool complexes, leading to overall wetter marshes and a cycle of water-logged
subsidence due to sustained inundation and saturation causing vegetation loss. This cycle of pool
development and subsequent breaching of the pool once sufficient water is ponded behind the
obstruction is referred to as the Water-logged Subsidence Trajectory (see Appendix 1 for details).
Fig. 5.5: Mega-pool breach
In some systems, the enlarging pool eventually intersects with an existing creek or ditch, resulting in a
breached pool that slowly revegetates, beginning around its edges, while smaller pools remain in the
interior. While this progression of pool formation and breaching occurs naturally in areas where the legacy
agricultural infrastructure combined with climate-related flooding accelerates the pool formation and
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expansion, the resulting subsidence occurs on a much faster timetable, faster than the system may be
able to respond.
In some areas, researchers have observed that entire marsh platforms are collapsing, resulting in
extensive open water, with the only remaining vegetated marsh located along ditches. Marsh collapse
results in loss of marsh elevation, meaning the marsh will be unable to maintain its elevation and adjust
to increasing seal levels and flooding.
The following images (Figures 5.6-5.9) developed by the SMARTeam provide another way of visualizing
the process and approximate timeframe of salt marsh secondary succession from initial decline through
subsidence, the breach phase, and then a new phase of accretion where the marsh recovers. However,
with impacts from historic farming and rising sea level factored in, there is now believed to be a period
of regression where marshes never reach the accretion phase or it is significantly delayed, during which
time there is a loss of overall marsh elevation. The restoration techniques proposed, especially runnels,
serve to accelerate the breach phase so that the accretion phase can begin.
Fig. 5.6 Timeline of Succession
Fig . 5.7 Succession Stages
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Fig. 5.8 Subsidence Stage
Fig. 5.9 Breach and Recovery Stage
The specific changes to current marsh conditions currently being observed include: 1) a shift of high
marsh habitat (S. patens) to low marsh habitat (S. alterniflora), 2) increased inundation of significant
portions of marsh driven by wind and tides, 3) enlarging of salt pools, 4) more algal mat growth in pools
and mudflats, 5) draining of some pool 6) ponding of marsh surface in between ditches. After some
investigation with conservation partners and academics, salt marsh restoration practitioners concluded
that the rate of SLR and other anthropogenic alterations are compromising the natural resilience of this
system.
Figure 5.10. (Left) Marsh in Essex, MA, example of waffle-pattern of mega pool formation. (Right) Hamlin
Reservation in Ipswich, MA, example of mega-pool formation.
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Figures 5.11 and 5.12 Examples of current marsh conditions indicating a need for restoration. At
left, clogging ditches or ditch plugs are causing poor drainage, leading to vegetation dieback and
creation of ponded areas. Depending on the cause, ditch remediation or runnels can improve tidal
hydrology and restore these areas to vegetated marsh. At right, Open Marsh Water Management
(“OMWM”) plugs are keeping water on the marsh at all tide levels, converting high marsh
vegetation to Spartina alterniflora. This area is a good candidate for shallow runnel to allow flood
tide to ebb, restoring drainage in the root zone to allow high marsh plants to reestablish.
Any proposed reversal or restoration of these effects must take into account that salt marsh hydrology
operates on a pair of paradoxes:
1) Salt marshes need to be regularly flooded (once a month for high marsh) in order to
maintain the salinity and sediment needed to maintain the marsh. However, too much
flooding converts high marsh to low marsh. Eventually, SLR can drown the marsh if it
outpaces marsh elevation gain through accretion.
2) Salt marsh vegetation requires periodic aeration of root zones to survive, but too much
aeration (such as from excessive exposure of peat from ditching) causes loss of
elevation, leading to increased flooding and loss of vegetation.
The innovative restoration techniques implemented since 2014 by USFWS and 2019 by The Trustees
were designed to make small adjustments in the trajectories described above to restore the natural
flooding and ebbing hydrology that is essential for the health of the marsh. The techniques and findings
of these pilot projects are described in more detail under Restoration Methods in Section 10.0 below
and summarized in Burdick et al. 2017 and Pau 2021.
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6.0 Existing Conditions
The restoration proposed for this project is located within the 9,125-acre Sandy Neck Barrier Beach
System ACEC established in 1978. Sandy Neck Beach extends eastward approximately seven miles and
shelters Barnstable Harbor and its extensive salt marshes. A portion of those marshes are included
within Mass Audubon’s BGM Wildlife Sanctuary in the Town of Barnstable. The project site is
approximately 77 acres, including an approximately 0.5-acre upland island, therefore the total salt
marsh proposed for restoration is 76.5 acres.
Mass. Audubon collaborated with APCC, EA, and NWR to collect data on existing marsh conditions
within the project area. This includes conducting baseline vegetation surveys, vegetative community
mapping and hydrological monitoring.
The specific site conditions for this marsh differ slightly from Massachusetts’ North Shore marshes which
have utilized the proposed restoration techniques. The extent and configuration of historic agricultural
use is different, resulting in a denser ditching pattern and several layers of ditching. The ditches are also
deeper and wider with larger embankment structures than the North Shore projects. As a result, the
BGM is more excessively drained and has fewer areas of water-logged subsidence compared with North
Shore marshes but has higher oxidation subsidence from peat exposure along the deeper ditches.
Existing pools tend to be smaller and many have already entered the breach phase. The BGM contains a
distinct pattern of small pools alongside embankments where they intersect ditches from an earlier
agricultural era, resulting in what appear on aerial photos as lollipop-shaped ponding areas (see Figures
6.1 and 6.2).
Fig. 6.1: Pattern of lollipop-shaped ponding areas through old embankments
Fig. 6.2 Photo by EA of marsh panne at low tide
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6.1 Hydrology
The project area receives tidal flow from the western portion of Barnstable Harbor known as Broad
Sound and specifically via an unnamed creek along the east side of Jules Island which connects with
Brickyard Creek to the north (see Figure 1 Site Locus). According to the National Oceanic and
Atmospheric Administration (“NOAA”) tide station in Boston (Sta ID# 8443970), mean higher high water
(“MHHW”) is 8.59 based on mean lower low water (“MLLW”) datum, and mean high water (“MHW”) is
8.20 (MLLW datum). This converts to an approximate NAVD88 elevation of 4.32 feet at MHW, with
MHHW at 4.7 feet.
The various tidal creeks and interior embankments divide the project site into 10 separate tidesheds
ranging in size from 2.77 to 20.58 acres. The approximate acreage of each tideshed is indicated in Figure
6.3 below. The area of proposed runnels and ditch remediation occur within a subset of these
subtidesheds, or micro-tidesheds with a typical size of less than 1 acre.
TIDESHED 1 2 3 4 5 6 7 8 9 10
ACRES 5.59 3.45 2.77 9.0 12.08 3.56 2.92 20.51 6.35 16.29
Fig 6.3
To establish site-specific baseline surface and groundwater conditions, the APCC conducted hydrologic
monitoring during one lunar cycle (30 days) from late October to early December 2023. This baseline
monitoring protocol, described in detail in Section 14, was developed to be consistent with criteria
established by MassDEP in its “Wetlands Program Guidelines on Massachusetts Wetlands Protection Act
and Water Quality Certifcation Provisions Regarding Salt Marsh Restoration Techniques, including Ditch
Remediation, Runnels and Marsh Habitat Mounds, June 18, 2024” (the “Guidance”) as well as
SMARTeams protocols established for previous restoration projects using similar techniques.
Monitoring stations were located in proximity to proposed ditch remediation and runnels within the
treatment areas and also in a control area located on a separate town-owned parcel to the west. A total
of seven water level loggers were deployed: two measuring groundwater elevation and one measuring
surface water elevation in the control area, and two measuring groundwater elevation and two
measuring surface water elevation in the restoration area. Full baseline monitoring results are included
in Appendix 2, but in summary, the data indicate the groundwater table is lower during all ebb tides
around the proposed ditch remediation areas compared to the proposed runnel areas, and the
percentage time flooded in areas near runnels is greater than areas near ditches, as expected. At both
proposed runnel and ditch treatment sites, the soil was found to be saturated 100% of the time at
approximately 10-inches (25 cm) soil depth, even at the lowest point in the tide.
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6.2 Vegetation
Vegetative species composition and density data can provide important information on overall marsh
health, as they are indicators of flooding regimes and salinity concentrations. APCC and EA collected
data on site vegetation using both desktop evaluation from remote public sources and direct field
investigations, including vegetative and elevation transects to provide a detailed baseline assessment of
vegetative communities within both the proposed treatment areas and the control area. Full details
from these efforts are included in Appendices 2 and 3. In the APCC study, 24 transects across the site
were established and evaluated in August 2023. Results demonstrated that S. alterniflora was the most
prevalent species observed throughout all transects. Transects near ditches showed more variability and
generally had a higher percentage of S. patens. This is expected since S. patens is a high marsh species
that benefits from better drained conditions. Transects near proposed runnels had a greater
percentages of short-form S. alterniflora with little variation across or within transects. These results are
consistent with observations from other salt marshes experiencing water-logging where S. patens is
being replaced with short form S. alterniflora.
EA expanded on this information during the spring of 2025 by establishing 6 additional elevation
transects across the site to assist in mapping expected vegetative communities by elevation. This data is
provided in detail in Appendix 3. Data was collected using Real-time Kinematic (RTK) Global Positioning
System (GPS)/Global Navigation Satellite System (GNSS) survey equipment (RTK rover and base station
or virtual reference station) to record the horizontal location and ground elevation at points along
transects where the vegetative community transitions from one type to another.
From the transect elevation data, EA developed the GIS-based Figure 6.4 that plots elevation contours
associated with the mean sea level (“MSL”), (MHW), (MHHW), and highest astronomical tide (“HAT”)
tidal datums based on publicly available local tide data from NOAA, Boston tide gage. These tidal datum
elevations served as a proxy for estimating the extent of various vegetative communities, including high
marsh, low marsh, mudflats, and subtidal areas throughout the site. Table 6.1 identifies the portion of
the project site within each tidal inundation zone by vegetative community.
Fig. 6.4
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Table 6.1. Area of Project Site within Tidal Inundation Zones
Zone
Elevation Range
(feet, NAVD88) *
Acres of Project
Site
Percent of
Project Site
Typical Vegetative Community
< MSL < -0.3 4.07 5.4% Mudflats/
Subtidal
MSL to MHW -0.3 to 4.3 24.42 32.1% Low Marsh
MHW to MHHW 4.3 to 4.7 25.45 33.5% High Marsh
MHHW to HAT 4.7 to 6.8 21.40 28.2% High Marsh/
Salt Shrub
> HAT > 6.8 0.62 0.82% Uplands
*NAVD88 = North American Vertical Datum of 1988
The elevation ranges for typical vegetative communities in the above table were calculated by adapting
a rapid assessment method (Kutcher 2022). It is understood that the hydrological impacts from historic
ditches and embankments can result in variations, such that S. patens may grow in lower elevations that
are excessively drained due to ditching and S. alterniflora may grow in higher elevations due to presence
of recent standing water or excessive saturation.
To provide more specific vegetation data, transects and in field observations were made as described in
Table 6.2 below.
Table 6.2. Vegetative Community Transect Results
Community
Type
Percent of Transect Length
A B C D E F Cumulative
Creek 3.1% 9.4% 17.3% 0.7% 3.0% 1.6% 6.5%
Ditch 9.9% 0.8% 0.0% 0.0% 3.6% 3.9% 3.3%
High Marsh 63.9% 63.1% 53.3% 63.9% 49.1% 40.9% 57.5%
Low Marsh 16.6% 22.7% 24.5% 22.3% 39.3% 44.6% 26.2%
Panne 5.4% 0.0% 2.6% 2.0% 3.6% 4.2% 2.8%
Phragmites 1.2% 1.8% 2.3% 0.0% 0.0% 0.0% 1.1%
Pool 0.0% 0.0% 0.0% 0.8% 0.7% 0.0% 0.2%
Unvegetated 0.0% 2.2% 0.0% 10.3% 0.8% 4.9% 2.3%
While the data collected by transects was limited to a relatively small segment of the marsh, these
results provide a high-level assessment of the relative abundance of each community type within the
project site.
In addition to the elevation and transect data to assess species and vegetative community composition,
the relative density of vegetation throughout the site was assessed by calculating the Unvegetated to
Vegetated Ratio (“UVVR”) using publicly available aerial imagery. The UVVR has been shown to be an
indicator of marsh vulnerability to sea-level rise as this metric is highly correlated with a marsh’s net
sediment budget (Ganju et al. 2017). A sediment supply may result in vertical expansion of a marsh
while a deficit will likely result in subsidence. Ganju determined that marshes with a UVVR greater than
0.1 can be considered unstable and that this value represents a tipping point to salt marsh drowning
and/or lateral contraction. Figure 6.5 shows the UVVR data for the project site (2014-1018) (Coubillion
et al. 2022). This data indicates and displays the ratio of unvegetated to vegetated area at each pixel
(approximately a 30-meter by 30-meter rectangle) as calculated from Landsat 8 satellite imagery. The
UVVR data for the project site indicate that approximately 42 acres (55 %) of the project site have a
UVVR of greater than 0.1.
20
Fig. 7.5
6.3 Sediment Supply
Sediment supply to the marsh may affect the overall success of the project and has implications for the
ability of the marsh to keep pace with SLR. APCC applied horizon markers in four randomly selected
monitoring stations, including ditch remediation and runnel sites and control areas (32 total locations)
to measure baseline sediment accretion over approximately one year from June/July 2023 to
July/August 2024 at the project site. The full study is included as Appendix 2. The markers consisted of
feldspar powder inside 0.25-meter plots, and accretion was measured using cores in each plot. Plots
were located in ditches where remediation is proposed and at the locations of proposed runnels, as well
as in control plots. The average accretion measured in each plot type was 5.3 millimeters per year
(mm/year) in the action ditches, 4.0 mm/year in the action runnels, 6.2 mm/year in the control ditches
and 3.8 mm/year in the control runnels (Mora et al. 2024). The average accretion rate at the site was
determined to be 4.77 mm/year (Mora et al. 2024). Accretion will continue to be tracked during the
post-restoration monitoring period as described in Section 14 below.
Accretion rates were then compared to relative SLR (“RSLR”) projections for Boston, where the monthly
mean sea level data from 1921 to 2024 indicates an increase of approximately 3 mm/year (National
Oceanic and Atmospheric Administration [NOAA] 2024). The Interagency Task Force 2100 RSLR value
from the low emissions scenario yields a RSLR estimated rate of 4.91 mm/year between 1992 and 2100.
The deficit between accretion rates and SLR becomes more exacerbated under higher (and more likely)
emission scenarios. These results demonstrate that even under the lowest RSLR projections, it is unlikely
that natural sediment accretion and biomass expansion alone will allow the marshes at the project area
to entirely keep pace with increased water surface elevations, and therefore additional intervention is
likely to be needed to preserve salt marsh habitat at this location.
6.4 Pannes and Pools
The EA evaluation also resulted in the identification of water features, including 314 pannes and pools
within the project site. While pannes and pools are a natural marsh feature and provide essential fish
and wildlife habitat, excessive or rapidly expanding shallow intertidal standing water with irregular
boundaries can be an indicator of marsh subsidence due to SLR. These water features can eventually
expand to form “mega-pools” as described in Section 6 above, causing rapid loss of marsh vegetation.
To identify baseline presence of pannes and pools, EA reviewed aerial imagery from 2023,
21
supplemented by direct field observations of 54% of the pools and pannes identified remotely. The
field- confirmed pannes and pools were then measured to assess size and depth relative to the adjacent
marsh platform. Observations were also made of the presence and extent of vegetation, especially
submerged aquatic vegetation such as Ruppia maritima. Results from this study are included in
Appendix 3.
The project has been designed to avoid deep pools and pannes believed to be relatively stable. We note
that only a few pools contained aquatic vegetation and none are in the vicinity of proposed runnels.
Fig. 6.6
6.5 Crab Burrow Density
High density of purple marsh crabs (Sesarma reticulatum) has been shown to reduce underground
biomass of S. patens in high marsh communities of New England (Szura et al. 2017), which can be used
as an indicator of overall marsh health (Turner et al. 2004). Crab burrow density was documented by EA
along the established transects described above. It is hoped that understanding the density and spatial
extent of crab burrow activity at the site will inform whether the proposed restoration efforts have any
effect on crab populations or their activities.
Crab burrow density was evaluated while traversing each transect and was limited to the area of the
marsh visible from the transect. As transects were traversed, EA indicated crab burrow density on a map
of the site using the following rankings:
• 0=no crab burrows observed,
• 1=low density of crab burrows,
• 2=moderate density of crab burrows,
• 3=high density of crab burrows.
Best professional judgement and experience at similar sites was used to assign a rank to each area. The
results are presented in Appendix 3. The locations within the project site where crab burrow density was
determined to be high are displayed in Figure 8 of this Appendix. In general, these areas were restricted
to the banks of creeks and ditches as well as some pannes. Some areas of bank sloughing, primarily
along major creeks, were noted in the field and attributed at least in part to crab burrowing activity.
Several purple marsh crabs were observed during the course of field data collection activities. A pattern
22
of marsh peat degradation along the upland edge of the marsh was also noted; however, it was unclear
whether this was related to crab burrow activity. Crab burrow density throughout most of the site was
low to moderate.
Fig. 6.7 EA Photo of crab burrows on the marsh platform edge of the main channel
6.6 Rare Species
The project site is located within Priority Habitat for Rare Wildlife as determined by the Mass Wildlife–
Natural Heritage and Endangered Species Program (“NHESP”). A Rare Species Information Request was
filed and NHESP reported the following species are listed for the project site:
Name Status
Northern Diamond-backed Terrapin/Malaclemys terrapin Threatened
Roseate Tern/Sterna dougallii Endangered
Common Tern/Sterna Hirundo Special Concern
While Northern Diamond-backed Terrapin is listed as present in the Barnstable Great Marsh ACEC marsh
system, it is not known to be present within the Barnstable Great Marsh Wildlife Sanctuary. NHESP
does not list Saltmarsh Sparrow as being present at the site, however they have been noted in point
counts conducted by Mass Audubon staff.
23
Fig. 6.8 MassMapper Priority Habitat
6.7 Area of Critical Environmental Concern
The entire project area is within the Sandy Neck Barrier Beach System ACEC, designated in
1978. The ACEC boundary generally follows the 100-year floodplain elevation on the
landward side and mean low water on the seaward side of the harbor. It includes the 7-
mile-long Sandy Neck Barrier Beach, Barnstable Harbor and an extensive salt marsh. As an
ACEC the wetland resources within the project site also qualify as Outstanding Resource
Waters (ORWs) under the Massachusetts Water Quality Regulations. The site is also a
Coastal Zone Management Sentinel Site.
Fig. 6.9 MassMapper ACEC Boundary
24
7.0 Sea Level Rise, Metonic Cycle and need for Accelerated
Restoration
Sea level rise, coupled with an increase in storm frequency and intensity are leading to increased storm
surge amplitude and occurrence (Murdukhayeva et al. 2013). Boston's mean sea level has risen greater
than 2.5 cm between 1950 and 2022 (NOAA 2022a) (Figure 7.1). According to NOAA relative sea level
trends, Boston is expected to experience 2.97mm/year with a 95% confidence interval of +/-
0.15mm/year based upon monthly MSL data from 1921 to 2024. This is equivalent to a change of 0.97
feet in 100 years. Mean sea level is a way to track change over long periods, and typically calculated by
averaging the MSL across 19 years of the last Metonic cycle. Because of this, reported MSL can be 20-30
years behind current MSL.
In addition to SLR, water levels are influenced by the 19-year Metonic Cycle, which is based upon the
relative position of the Earth, moon, and sun. The gravitational pull of these celestial bodies changes
throughout this cycle, affecting the tidal amplitude on Earth. Since the moon primarily influences ocean
tides, this cycle causes tides to be higher or lower, depending on where the moon is in the cycle
(Szabados 2008). Figure 2-10 represents the observed tide data from the NOAA Boston tide gauge from
1984 to 2020 showing the interaction of SLR and variations in tidal amplitude due to the Metonic cycle.
The years 2005 to 2017 show a period of increasing tidal amplitude, and 2017 to approximately 2025 is a
period of decreasing tidal amplitude. We are just finishing the “down phase” of a 19-year tidal pattern .
FIG. 7 .1 OBSERVED TIDES FROM NOAA BOSTON TIDE GAUGE FROM IDEALIZED TIDES COMBINING PREDICTED SEA LEVEL RISE
1984 TO 2020.
Note: Observed tides from NOAA Boston tide gauge from 1984 to 2020, compiled by Jim Morris,
University of South Carolina. The blue line indicates predicted tides based on the 19 -year
Metonic cycle; 2007-2016 was a period of increasing flooding due to higher lunar gravity. Red
dots are actual observed tides. Notice the increased tides from 2009 to 2019. The next period of
increased tides starts in 2026, peaking in 2035.
When SLR is added to the normal variations in the tidal amplitude due to the Metonic Cycle, actual sea
level would be even higher than the current linear projections. In the graph above to the right note the
observed tidal amplitude from 2009 to 2014 is significantly higher than predicted by linear SLR. This
period coincided with observations of lower saltmarsh sparrow productivity in southern New England,
and drastic signs of marsh degradation including loss of vegetation and marsh elevation that prompted
the New England salt marsh researchers to investigate its causes. The increasing tidal amplitude starting
in 2026 is expected to result in additional and accelerated marsh changes. Without intervention to
restore tidal hydrology that is in balance with natural marsh processes, additional loss of vegetation can
be expected.
25
8.0 Restoration Design Process
The conceptual design of this project was developed by Geoff Wilson of NWR, in coordination with Mass
Audubon and the Salt Marsh Adaptation and Resiliency Team (“SMARTeam”) which includes various
federal and state agencies representatives and academic partners as well as private and non-profit
marsh managers. The final design was adopted by Mass Audubon’s coastal management staff, in
consultation with other regional salt marsh scientists with extensive marsh restoration experience
within East Coast marshes.
The design approach is intended to restore primary marsh hydrology within a mosaic marsh platform at
varying stages in the secondary succession process (secondary to the initial disturbance from agricultural
use). This fractured mosaic within each sub-tideshed to be restored has disrupted the parallel trajectory
between sea level elevation and marsh platform elevation. In a “healthy” system, the elevation
trajectory of the marsh platform should correlate positively with SLR. The design addresses each
secondary successional stage within the mosaic with appropriate restoration techniques to stabilize
marsh platform hydrology that restores connectivity of each sub-tideshed.
The SMARTeam tiered design process is described in detail in Appendix 4. In summary the steps involve
the following:
1. Review of historic and current aerial photography and other remote sources to assess the extent
and nature of previous agricultural activities and other disturbances.
2. Conduct baseline vegetation mapping to assess current conditions using current aerial
photography.
3. Inventory and map historic agricultural infrastructure such as ditches and embankments or
other man-made structures.
4. Field verify all collected data and identify ditches to serve as primary hydrology for each
subtideshed. Identify areas of waterlogged subsidence for potential runnels.
5. Develop tailored design for the site working with the existing specific ditch network and extent
of subsidence occurring in each subtideshed. Design the type and location of runnels and
ditches needed to restore single channel hydrology.
6. Categorize ditches based upon extent of clogging to calculate linear feet of treatment needed
and categorize runnels based upon the stage of secondary marsh succession that is occurring.
9.0 Restoration Methods
Through previous projects completed, a deeper understanding of marsh restoration techniques and
their interactions with natural processes has been gained. The specific nature-based restoration
techniques included in this design are intended to operate in synergy to reestablish proper expression of
ecosystem processes, boost resilience to increased flooding, and establish a marsh-sustaining trajectory.
This Section describes restoration methods. Please refer to Concept Design Plans prepared by EA
included as an attachment for detailed design for the project area.
In general, the techniques serve to lower the zone of saturation in areas proposed to contain runnels to
improve growing conditions in the root zone and to raise it in areas proposed for ditch remediation to
eliminate excess oxidation of peat as indicated below in Figure 9.1 provided by the SMARTeam.
26
FIG. 9.1: WHILE PAST HUMAN ALTERATIONS MANIFEST IN 2 DIFFERENT TYPES OF SUBSIDENCE TRAJECTORIES (WATERLOGGED
AND OXIDIZATION), RUNNELS AND DITCH REMEDIATION TECHNIQUES ARE BOTH TRYING TO RESTORE TO A SINGLE DENDRITIC
CHANNEL HYDROLOGY.
9.1 Addressing Oxidation Subsidence through Ditch Remediation:
To address the subsidence between ditches in a densely ditched marsh caused by oxidation of peat on
ditch banks, the project proposes the gradual transition of selected ditches determined to be auxiliary or
not needed to re-establish tideshed equilibrium, back to salt marsh peat using the ditch remediation
technique. The auxiliary ditches are determined by careful examination and mapping of the tidal
dynamics within each portion of marsh. By restoring multiple auxiliary ditches to vegetated marsh and
maintaining a single primary channel, the tideshed can be restored to or approach single-channel
hydrology that is similar to the natural hydrology of undisturbed marshes, which will in turn assist with
addressing subsidence.
Ditches selected for treatment are typically smaller and shallower, allowing larger untreated ditches to
convert or be maintained as primary tidal channels. On average, the treatment ditches are 60- inches
wide and 48-inches deep. Once auxiliary ditches are identified for restoration, the treatment process
begins with harvesting salt marsh hay parallel to the identified treatment ditch by mowing a swath of
vegetation up to 20 feet in width using a walk-behind, self-propelled mower. The mowed hay is then
collected and placed into auxiliary ditches either with backpack blowers or hay rake. To prevent the hay
from washing away at the first high tide, it is secured to the bottom of the ditch with a biodegradable
sisal baler twine (59kg tensile strength) tied to 1 inch by 1-inch wood stakes. The hay is placed on an
incline with deeper depths at the upstream end to allow for continued drainage while the ditch is being
restored and to prevent clogging from uneven sediment distribution. With tidal exposure, hay is
compressed to depths of 6 inches on average. The hay serves to slow water flow and encourages the
natural deposition of sediment from the water column during incoming tides. A typical ditch treatment
is illustrated in Figure 9.2 below. Once the ditch floor reaches an elevation that is about 8-inches below
marsh surface, S. alterniflora is expected to become established which will further bind the new peat
layers to the surrounding marsh. Some ditch bottoms may become fully revegetated within a single
growing season, while deeper ditches will require follow-up treatment spaced at least 6 months apart
for up to 4-5 treatments. It will also be necessary to ensure that the newly vegetated and healed ditches
develop evenly without blockages which would trap water between tides. Monitoring will be conducted
to ensure no blockages occur.
27
Fig. 9.2 Typical Marsh Cross Section
It is expected that upon completion of each year of treatment, normal daily tidal flow into the treated
ditches within each sub-tideshed will gradually be reduced and redirected to the untreated ditches,
reinforcing these as primary channels. While the overall volume of flow entering and draining the sub-
tideshed will remain unchanged, the rate of flow through the primary channels on the incoming and
outgoing tide is expected to increase over time as the treated ditches no longer accept flow. The
increased rate of flow in the primary ditches will serve to maintain the channel open and free of clogs,
bringing the site closer to single-channel hydrology of a healthy, resilient salt marsh. Reducing the
density of ditches will also restore groundwater to pre-ditching levels, which will alleviate the subsidence
caused by oxidization.
The initial indicator of successful treatment is continued sediment accumulation and the revegetation in
the auxiliary ditch bottom with S. alterniflora or other endemic marsh species. The implementation
methods for this restoration technique are very low impact since they require only natural on-site
materials and avoid the use of heavy equipment except for walk behind mowers. Because the ensuing
restoration process is gradual, it allows managers to observe results and make any adjustments as
necessary to achieve full restoration potential.
When applied as test projects at the Parker River NWR and The Trustees’ Old Town Hill Reservation, the
ditch treatment resulted in substantial gains in percent cover and stem density within the treated
ditches (Burdick 2020, Burdick 2023). This low-impact technique does result in some cutting of marsh
grass. Buchsbaum et al (2006) report that haying is still practiced on 400 ha of marsh in this area of
Massachusetts and their field study found no impacts to end-of-year standing biomass or plant species
density from marsh haying but species composition differences favoring S. patens over S. alterniflora
were found in areas subject to 2-year haying rotation compared to controls. Most of the project areas
where ditches are proposed to be treated will require only 2-4 passes to harvest sufficient grass for ditch
remediation.
The typical implementation season may be limited by any time-of-year restrictions established by
MassWildlife NHESP.
28
Figure 9.3. Treated vs Untreated ditches demonstrating recolonization by marsh grasses.
Parker River NWR original pilot project (Photo Credit: D. Burdick).
29
Metrics of Success: Within 3-5 years of starting treatment, the ditch will be vegetated with endemic
marsh species. The elevation of a remediated ditch will be at or slightly below approximately 8-inches
(<20cm) the marsh surface. There should be no water impounding in the marsh panels in between
remediated ditches after remediation is complete. In the interim, water may inundate the marsh panels
before a natural drainage path forms, but this is not anticipated to lead to dieback or open water. On a
landscape scale, the remaining open ditches should be self-sustaining and at equilibrium with the sub-
tidesheds.
9.2 Addressing Waterlogged Subsidence through Runnels
Waterlogged subsidence occurs from inadequate drainage during the ebb tide, resulting in
drowning and loss of emergent plants. Without the continual belowground production of roots and
rhizomes supporting the peat volume and integrity, over-saturated peat subsides and loses
elevation (Nyman et al. 1995, Day et al. 2011, Mariotti et al. 2020). In New England, one of the
leading causes is attributed to past agricultural activities (Adamowicz et al. 2020). Over saturation
often occurs in areas where historic agricultural embankments prevent normal tidal exchange, or
where former agricultural ditches have become clogged and no longer provide sufficient tidal
exchange. Waterlogging subsidence from these agricultural legacies are exacerbated by
acceleration of SLR over the past 20 years (Nichols and Cazenave, 2010, Goddard et al. 2015).
Without intervention, the Mega-pool Breach Cycle would naturally occur in intervals of about 10-100
years, based on past SLR rates (Wilson et al. 2014). However, SLR has increased from 1-2
mm/year to over 4 mm/year (Massachusetts Coastal Flood Risk Model) and we expect that rate to
double in the next 10 years. During that time, substantial additional subsidence is expected to occur
which would significantly and potentially irreversibly impair the ability of the marsh to keep up
with rising sea levels and in turn its ability to provide its natural flood control and storm damage
protection functions and its value as wildlife habitat.
To address this waterlogged subsidence, shallow runnels may be constructed to improve drainage
within prescribed areas that are experiencing degradation from an altered and non- beneficial
hydrology from legacy infrastructure. The runnels convey ebbing tides to existing channels,
allowing the monthly tidal fluctuation in groundwater of inundated marsh areas to be restored (see
Figure 9.4 below). This technique can address all successional stages of the waterlogging trajectory
including the earliest stages of decline, where seemingly healthy high marsh grasses persist but lack
thatch (healthy high marsh has 2-3 years of dead growth), to more advanced stages of Late Decline
where vegetation is converting to S. alterniflora, to the well advanced stage of Early Megapool
where areas experience vegetation dieback and standing water that combine to form mega pools.
As runnels are shallow, they will not drain deeper and natural pools on ebb tide cycles leaving these
important habitats for wildlife.
30
Fig. 9.4 Typical Runnel Detail and Profile
Experience from previous projects has advanced our understanding of runnel function and
terminology. Runnels may be constructed as Headward Extension Runnels which are intended
improve drainage in areas beyond where ditches end where drainage does not extend to the full
reach of the micro-tideshed. Runnels may also be used to promote lateral flow, such as laterally
between ditches and a primary channel and are especially useful as treated ditches are healing.
Due to the deep and dense pattern of ditching at this site, no lateral runnels are proposed, and all
the runnels qualify as headward extension runnels.
Runnels may also be classified based upon the current stage of secondary succession the runnel is
intended to address. Priority 1 runnels are proposed in areas of advanced subsidence while Priority 2
runnels are proposed in areas of early-stage subsidence. Approximately 2/3 of the proposed runnels are
located within Priority 1 areas. Priority 2 runnels are located primarily along the project’s southern
boundary nearest the upland. These areas are experiencing early vegetative changes and potentially
some vegetation loss but are not yet experiencing major vegetation loss and are not yet fully saturated.
However, it is expected that without treatment the area will continue to proceed toward advanced
subsidence conditions. All Priority 2 runnels at the site qualify as headward extension. There are no
31
Lateral Expansion runnels proposed for this project.
The range of dimensions and shape for the currently proposed runnel design has been adapted
based on monitoring of previous efforts. Past experiences have demonstrated that channels
constructed with a deep V-shape later incised to create deeper channels over time, while
simultaneously clogging due to vegetation growth from the bank. Channels that are constructed
wider and only deep enough to reach below the root zone will more naturally adapt over time to
accommodate the volume of water in the new channel without clogging. The volume and energy of
tidal water flooding and ebbing through these channels maintains the channel configuration. None
of the 11 runnels in The Trustees Phase II project constructed in this way have clogged since being
installed. The oldest runnels have been in place since March 2021.
EA surveyed a representative sample of 46 proposed runnel locations to collect baseline cross-section
elevation data. This effort included representative runnels from each tideshed, with data collected at
start and end points. This information will be used to compare post-restoration conditions during
monitoring (see Section 14 below). A permanent survey benchmark was installed for reference during
future monitoring. Topographic data was also gathered by EA at the start and end of each of the sample
runnels.WR
Runnels for this project will be constructed using a small excavator equipped with a 2 -inch tooth
that allows for construction of a small low- flow channel to minimize potential for clogging. The
runnels are constructed 30-inches wide by 8-inches deep at the headward end, gradually tapering
to 36-inches wide by 10-inches deep at the downstream end where it connects to a receiving
channel. Occasionally runnels will be constructed with hand tools (shovels). Methods to reduce
marsh impacts while using heavy equipment are described under Section 11 Best Management
Practices and include use of low ground-pressure equipment and construction mats. The
customized bucket allows peat to be cut precisely according to the dimensions described above
with no excessive digging. Material excavated can then be efficiently re-used on the marsh surface
to construct structured microtopography for the purpose of creating habitat for at-risk wildlife as
described in Section 9.3 below. Prior to excavating the runnels, the contractor will confirm the
location and elevation of the microtopography mounds (described in the following section) to be
created near that site so that the mounds to be do not exceed MHHW or the maximum surrounding
marsh elevation.
There are areas of the marsh that contain historic ditches that may contain vegetation growing
across the top of the ditch, obscuring them from view, but a void remains within the substrate in
the footprint of the ditch. These subterranean ditch voids must be identified during project design
and confirmed by soil probe prior to excavation to avoid the potential for runnels to intersect with them
and potentially cause over draining of the marsh substrate. They can sometimes be identified
through aerial photography or even review of historic farmer’s literature where the ditch network is
laid out. The proposed design anticipates this issue and locates the runnels entirely within the
existing historic ditch network, allowing selected segments of the existing ditching infrastructure to
be restored in a configuration that restores the single channel hydrology network across the entire
sub-tideshed without intersecting subterranean ditch voids.
32
Figure 9 .5 : Examples of Subsurface Ditch Voids
Upon completion of each runnel, GPS coordinates will be obtained at the start and end. Width and depth
relative to the marsh surface will be obtained to assist in tracking channel changes over time.
Metrics of success: Hydroperiod in breached pools and marsh areas adjacent to runnels and ditch
remediation treatments will be assessed to determine if hydrological restoration goals are met.
Channels should ebb and flood with minimal tidal lag or restriction. Channel geomorphology may
change to accommodate restored tidal flow and should not clog over time. The marsh areas drained by
the runnel should have lowered ground water levels (ideally reduction of 80% of root zone flooding).
Adaptative Management (aka Corrective Action) as described in Section 14 below, will be
implemented if monitoring data and reconnaissance surveys indicate that the above metrics are not
met.
33
9.3 Restoring Rare Species Habitat through Structured Micro-topography
While NHESP doesn’t list Saltmarsh Sparrow within the project site, point counts conducted by Mass
Audubon staff have noted their presence. The site is also listed as a Priority Site by the Atlantic Coast
Joint Venture (ACJV) for this species. The Saltmarsh Sparrow relies entirely on high marsh areas for
nesting, building nests in the grass just above the mean high tide line. With rising sea levels, the
availability of this habitat is in steep decline. When SLR is paired with the marsh-wide legacy of ditching
and embankments, a clear urgency for restoration becomes apparent.
According to the ACJV, at its current rate of 9% decline a year, this species could be functionally extinct
by 2030 if there is no intervention to reverse the trend. The ACJV conservation goal for the saltmarsh
sparrow is to halt the steep population decline and sustain the population above 25,000 breeding birds,
2,588 in Massachusetts, by restoring and enhancing existing salt marsh patches to provide high-quality
nesting habitat, to protect adjacent inland areas that buffer existing salt marsh patches and to provide
corridors to allow marsh migration in the future, as sea level rises. The Massachusetts goal is to obtain
7,596 acres of habitat (Saltmarsh Sparrow Conservation Plan 2020). However, given the limited
opportunity for the salt marsh to migrate inland due to steep topography at the upland margins in much
of the project area, restoration interventions that allow the marsh to gain elevation become the logical
focus for marsh managers.
This project proposes to improve nesting habitat using ACJV recommended strategies of ditch
remediation and restoration of tidal hydrology to minimize marsh subsidence and the creation of
microtopography to create new nesting habitat and to reduce nest flooding.
The proposed restoration methods involve the relocation of sediment and marsh sod excavated during
the construction of the runnels to nearby high marsh habitat areas to create small areas of structured
micro-topography suitable for saltmarsh sparrow nesting. The relocated material creates small,
mounded areas 80-140 square feet in size. Final microtopography islands will not exceed the mean
highest annual tide (HAT) of 6.82 or the highest point of the naturally vegetated marsh, whichever is
lower. For this project the mounds are proposed at 5.25 with a survey tolerance of .25 feet. (for
reference, MHHW is 4.77 feet). Revegetation of the mounds will rely on germination of existing seed
stock and preservation of plants within the excavated material as much as possible. If sufficient
revegetation is not achieved within 2 years, these areas will be planted with high marsh plugs.
The restoration is proposed to occur during a neap tide cycle. Equipment used is the same as
equipment used for micro-runnel construction and includes a low ground -pressure mini excavator
operating on timber mats. The enhanced habitat will be near the runnel, thereby minimizing
equipment movement in the marsh and potential disturbance. Marsh islands are to be staggered in
location to minimize detection by predators and located 10-12 feet from the center of the runnel
on both sides of the runnel. No stockpiling of material directly on the marsh will occur. All material
collected for this purpose will be relocated directly to its destination, typically within the same day
it is excavated but in no case longer than 24 hours.
34
The size and height of the microtopography islands will be confirmed by laser level tied to a
preselected biological benchmark when first beginning work at a site to ensure it is constructed
within the size limits described above and not above the tidal range for high marsh vegetation in
that unit. Every effort will be made during the transport of marsh substrate from the runnel to
preserve the existing vegetation and rootstock within the excavated material to minimize any
temporary loss of vegetative cover. All islands constructed will be secured to the underlying
substrate with wooden stakes until vegetation is re-rooted.
Careful smoothing of the mound edges will be necessary to ensure it is fully integrated with the
surrounding grade and there are no exposed edges that could cause drying out of roots. There may
be temporary transplant shock, but revegetation is expected within the same growing season or
immediately after, depending on placement timing.
The number of distinct mounds created is directly related to the length of the runnel to be
constructed. Based on runnel dimensions, approximately 1.5 cubic feet of material per linear foot
of runnel creation is assumed. Since some compaction occurs during excavation and transport, the
volumes proposed to establish the proposed micro -topography include a compaction factor of
approximately 30% based on previous experience. The plans do not specifically identify the
locations of microtopography as the exact location and dimensions will be based on the amount of
material removed during runneling, the density of sod excavated and the existing topography of
the marsh to receive the material but will be located within the reach of the excavator without
having to relocate construction mats. Material excavated to create runnels in highly saturated
substrate may not easily form micro- topography islands and in such cases will be thinly spread
over the marsh surface adjacent to the runnel. In this way none of the valuable marsh substrate is
lost from the system. Thinly broadcast sediment will not exceed 2 inches in depth and will be at
least 10 feet from creeks, ditches, or channels.
At microtopography islands constructed for The Trustees Phase II project and USFWS Parker River
NWR, depending on date of construction, nesting islands typically revegetated in 1 full growing
season and are largely indistinguishable from the surrounding marsh landscape indicating this
technique has tremendous promise and does not appear to have any adverse impacts to marsh
habitat.
All the marsh units include use of runnel material to create microtopography islands because
restoration of wildlife habitat is also a primary goal of salt marsh restoration efforts. The technique
offers an opportunity to provide for beneficial re-use of the runnel material to support marsh
accretion as well as providing an opportunity to further improve habitat for a declining species.
35
Fig. 9.6 Completed Nesting Islands
Nesting Island 1A at William Forward Wildlife Smaller islands at Old Pond Reservation
Management Area Maine Cost Heritage Trust, Hancock ME
Photo by Adam Clark 9-27-22
FIG.9.7: N EWLY CONSTRUCTED NEST
I SLAND AT PARKER RIVER NATIONAL
WILDLIFE REFUGE 2019 – PHOTO
COURTESY USFWS
36
F IGURE 9.8 N ESTING ISLAND AT
USFWS PARKER R IVER WILDLIFE
REFUGE CREATED IN MAY 2019
THREE MONTHS AFTER CONSTRUCTION
Upon completion, the mounds will be located by GPS, and the size and maximum
elevation will be recorded to assist in future monitoring.
Metrics of Success: Microtopography islands should be more than 75% vegetated with
native salt marsh plants by year 3 of monitoring. No invasive or upland species should
grow on these islands. If they do, islands will be assessed for probable cause and
corrective action taken which could include removal of plants (e.g., hand pulling,
selective herbicide control) or island elevation will be lowered to provide proper
flooding. Growing conditions during the first years of establishment can influence how
the islands vegetate, such as colonization by brackish species in high precipitation years.
If this occurs, adjustments should be made to the mound to allow water to ebb. If at
least 30% revegetation is not established with appropriate native marsh species by the
first fall following construction and 75% by the end of year 3 for all islands monitored,
supplemental plantings of marsh species may be installed to ensure a minimum of 75%
native marsh vegetative cover upon project completion.
**MARSH HABITAT MOUND FILL VOLUME IS EQUAL TO THE RUNNEL CREATION CUT VOLUME. MARSH HABITAT MOUND
CREATION WILL BE
DIAMETER LIMITED BY THE VOLUME OF MATERIAL EXCAVATED TO CREATE RUNNELS. VERIFY DIMENSIONS IN FIELD
(VIF).
Fig 9.9 Marsh Habitat Mound Detail
37
10.Project Impacts
10.1 Quantification of treatments
The project proposes to enhance wetland function, especially its ability to adapt to increased storm
frequency and intensity, and the accelerated rate of SLR, thereby improving its capacity to provide
essential public benefits such as storm damage prevention and flood control functions. It does not result
in any temporary or permanent loss or alteration of any marsh functions during any phase of treatment.
There will be some temporary effects during implementation due to the need for equipment to access
the restoration areas, as well as converting from open water, mudflat or ditch to vegetated marsh
platform.
For purposes of calculating impacts, we have identified the anticipated areas of direct and indirect
impact. Direct impacts include the footprint of ditches, runnels, and microtopography islands. Indirect
impacts are temporary and include areas of mowing. Measures to mitigate all impacts are discussed in
Mitigation Measures in Section 7.0 below. The anticipated extent of impact associated with each
restoration method is presented in Table 11.1 below.
Table 11.1 Areas of Marsh Impact
10.2 Ditch Remediation Impacts
A total combined 15,072 linear feet of ditches are proposed to be remediated either completely or
partially (point treatment). Ditches average 60-inches wide and 48-inches deep, for a treatment area of
approximately 75,360 square feet or 1.73 acres. The area of potential restoration or enhancement is the
entire project area of 76.5 acres.
It is expected that upon completion of each ditch remediation treatment, normal daily tidal flow into the
treated ditches within each tideshed will gradually be reduced. Flow will continue to be directed to the
untreated ditches, identified as primary channels. While the overall volume of flow entering the
tideshed will remain unchanged, the rate of flow through the primary channels is expected to increase
over time. The increased rate of flow will maintain the channel in a more open condition that is most
similar to original marsh conditions prior to ditching. There is not expected to be any adverse effect such
as excess sedimentation or erosion from this process as the changes occur gradually over many tide
cycles.
There are not expected to be any adverse impacts associated with mowing, as this activity continues to
be conducted in areas of the marsh for collection of salt hay without significant adverse effect.
According to research conducted by Robert Buchsbaum (2008), hayed marshes were no different from
adjacent reference marshes in plant species density and end-of-year aboveground biomass but did differ
in species composition, with S. patens being more abundant in hayed marshes. These grasses will re-
38
grow to their mature height during the same growing season, or if late season application occurs, during
the next spring growing season.
10.3 Runnel Impacts
The total length of the runnels proposed at this site is 3,384 linear feet. Runnel width ranges from
30 inches at the headwater end to 36 inches at the tailwater end and depth ranges from 8 -10
inches at the headwater end to 10 inches at the tailwater end For purposes of estimating
maximum total impacts, we have assumed 2.8 feet wide by 0.8 feet deep for a total work area of
9,475 sf and a total cut of 150 cy which includes a 30% compaction factor.
The contractor will employ only low-ground pressure equipment (< 2 lbs. psi) and will operate on
temporary timber mats to further lower weight displacement of equipment and to minimize
potential compression of peat and disturbance to vegetation. The mat sizes will be constructed to
allow for easy transport and placement with the excavator head. Two or three mats are expected to
be used, which will be leap-frogged to allow equipment to move throughout the marsh. All machinery
will use non-toxic fluids except for petroleum grease and will maintain spill kits on site.
Creation of runnels is expected to result in short -term and long-term changes to the vegetative
communities within the immediate sub-tideshed, decreasing the UVVR which has been
demonstrated to correlate with the resiliency and life span of a marsh unit (Ganju et al. 2020).
Runnels are used to reconnect marsh areas that are artificially isolated due to the presence of
historical infrastructure or ditch clogs. They allow flooding tides and sediment crucial to marsh
growth to be distributed on the flood tide and drain on the ebb tide, increasing the ability of these
marsh areas to keep up with SLR.
At no point during runnel construction is salt marsh function lost or diminished. During the first 1-2
tidal cycles following runnel construction there may be some turbidity until the channel stabilizes.
This does not represent an adverse impact as sediment deposition is a natural and beneficial
function within the marsh. For example, USFWS observed that a runnel created through an OMWM
ditch plug in 2015 enabled the deposition of a large amount of sediment upstream of an obstruction
during the 2018 Grayson storm, resulting in natural conversion of open pool to high marsh within 6
years.
Creation of runnels will improve salt marsh function by restoring the groundwater hydroperiod in
the root zone of the marsh vegetation. Runnels also restore the natural fluctuation in groundwater
level within a lunar cycle, lowering the zone of saturation to below the root zone during ebb tides,
and optimizing productivity for S. patens (Morris et al. 2002)
10.4 Microtopography Mounds Impacts
The construction of the runnels results in a transplantation of sod and/or sediment carefully cut
from the runnel site to the proposed microtopography island site. Upon completion, full
restoration of vegetation is expected in as little as 1 growing season, depending on time of year
constructed, and the microtopography islands will provide additional potential habitat for Saltmarsh
sparrow, a state-listed Species of Special Concern.
The number of proposed microtopography islands constructed will depend on several factors,
including the construction methods of the selected contractor, runnel length, average elevation of
marsh in the project area, and the maximum island elevation that will continue to support salt
marsh vegetation.
Negative impacts such as alteration of hydrology causing impoundment of water surrounding the
island and alteration of biogeochemical processes are not expected due to the small size and
orientation of the islands (DiNunzio et al. 2023). Average mound size is expected to range
from 80-140 square feet spaced every 10-30 feet alongside both sides of the runnel, no less
than 5 feet from the runnel center and no more than the reach of the excavator arm from the
runnel to minimize the need for equipment movement on the marsh. The mounds are spaced and
sized in a randomized way to minimize pattern recognition by sparrow predators.
Care will be taken when working in areas that are wetter with less stable soil conditions. If signs of
marsh compression or vegetation impacts are observed from transport of sediment to create larger
39
islands; design will be adjusted to place smaller islands closer to the location of source material. If
conducted correctly, there should be little to no evidence of equipment on the marsh following 1 -2
tidal cycles.
10.5 Hydrologic Changes
It is anticipated that, upon completion of ditch remediation, the usual tidal flow into the treated ditches
will gradually decrease. Flow will continue to be directed towards untreated ditches identified as
primary channels. While the overall tidal volume entering the tideshed will remain consistent, the flow
rate through these primary channels is expected to steadily increase.
The proposed placement of runnels is generally within areas where tidal water has been obstructed by
clogs and embankments. By constructing these runnels, these regions are likely to regain typical tidal
flow, enabling trapped upstream channel water to ebb but also to enhance tidal flow from incoming
tides, allowing the marsh to receive sediment essential for its growth.
Importantly, the groundwater in the previously inundated marsh will shift towards a healthy cyclic
pattern linked to lunar tides. This will result in an oxidized root zone (20-30 cm below the marsh surface)
during ebb tide and flooding close to or over the marsh during flooding tides. Such conditions are
expected to boost the growth of marsh vegetation and expedite vertical accretion processes.
The channel dimensions of the untreated ditches (primary channels) will be in equilibrium with the
increased flow and will be able to maintain the channels’ openess and prevent clogging. The ability of
this restoration project to incorporate tiered, dendritic channel design will allow these channels to
absorb and adapt to changing tidal conditions expected under SLR and storm conditions. There is not
expected to be any adverse effect such as excess sedimentation or erosion from this process as the
branching dendritic channel design diffuses tidal energy and any changes in channel geomorphology are
expected to occur gradually over many tide cycles. Ultimately, the restoration of the dendritic channel
network is expected to provide an opportunity to deliver more sediment to the marsh surface since less
will be sequestered in ditch bottoms. This should allow for an increase in accretion potential.
During the first 1-2 tidal cycles there may be some turbidity until the channel stabilizes. This does not
represent an adverse impact as sediment deposition is a natural and beneficial function within the
marsh. Excessive erosion, should it unexpectedly occur, will be addressed with adaptive management
(corrective action) strategies as described in Section 15, which might include construction of a sill or
small berm to slow flow until the runnel area is fully stabilized. The adjustments to marsh hydrology
created by this treatment are intentionally modest. The restoration technique relies upon the ability of
the marsh to largely restore its own equilibrium. It does not seek to artificially influence tidal hydrology
more than necessary to accelerate the natural progression toward a sustainable and resilient tidal
hydrology. The intervention proposed is necessary to facilitate and accelerate the natural restoration of
the marsh surface, as the current rate of natural restoration is not sufficient to keep up with rising sea
levels and storm impacts.
10.6 Vegetation Changes
There are not expected to be any adverse impacts associated with mowing, as this activity continues to
be conducted in other salt marshes for collection of salt hay without significant adverse effect.
According to research conducted by Robert Buchsbaum (2006), hayed marshes were no different from
adjacent reference marshes in plant species density and end-of-year aboveground biomass but did differ
in species composition, with Spartina patens being more abundant in hayed marshes. Pilot ditch
remediation projects at the Parker River National Wildlife Refuge and on Trustees’ properties found
rapid rebound of vegetation within a month of mowing and development of thatch layer, where
present, within a growing season.
The construction of the runnels results in a transplantation of sod from the runnel site to the proposed
microtopography locations. Full restoration of vegetation on microtopography islands can occur within a
single growing season if work is conducted early in the season. While the technique involves some
displacement of vegetation, the work is intended to increase overall stem density and overall vegetative
cover by reducing saturation and subsidence over a larger area, resulting in an increase in vegetated
platform. Upon completion, the microtopography islands will provide additional potential habitat for
Saltmarsh sparrow. At no point during the restoration process is salt marsh function lost or diminished.
Access to the runnel sites and nesting locations will be selected based upon the shortest route with the
most stable surface conditions. Use of timber mats will ensure that there will be no vegetation impacts
from use of heavy equipment. Additional constraints and Best Management Practices will ensure that
any activity that impacts vegetation is stopped immediately. If conducted correctly, there should be little
to no evidence of equipment on the marsh following 1-2 tidal cycles.
10.7 Effects on Permanent Pools and Submerged Aquatic Vegetation
In this project, the primary intent of runnels is to restore normal tidal flow to all parts of the marsh
within the project limits. It should be noted that while natural pools and pannes exist in some areas of
the marsh, many were eliminated by farming practices. Natural pools often occur as deeper pools
embedded in expanding mega-pool complexes. Natural pools in unfarmed areas tended to be in the
tideshed margins associated with the lowest order tidal channels at higher elevations (Millette et al.
2010). Natural pools are typically small, rounded pools with a well-defined edge marked by a vertical
drop in elevation (even if only a few inches) and have a soft bottom of organic muck. These are distinctly
different from mega-pools formed from waterlogged subsidence which are characterized by an uneven
edge of more sparse vegetation, contain a firm bottom, and are only a few inches deep (S. Adamowicz
pers comm).
Ruppia is a submerged aquatic plant with a broad habitat range, including freshwater and low-moderate
salinity pools. It is an important food source for waterfowl as well as food and cover for a variety of
invertebrates. It typically occurs in pools approximately 4-24 inches in depth, with decreasing density
above or below that range according to David Burdick, Ph.D., Coastal Ecologist at the University of New
Hampshire, and Great Marsh SMARTeam member.
EA identified 314 pools and pannes on site (see Appendix 3) using remote desktop sources,
supplemented by field inspections of a subset of the features identified remotely. Very few were found
to be vegetated. No runnels are proposed in the vicinity of these vegetated pannes or pools. Past
projects have not shown impacts to permanent pools containing Ruppia.
10.8 Rare species impacts
The project site is a potential foraging habitat for federally listed Roseate Terns. It is also listed for
Diamond-backed terrapin (threatened) and common tern (special concern). While Saltmarsh Sparrow is
not listed for the site, the project improves potential habitat for this species. Mass Audubon is in the
process of consulting with MassWildlife – NHESP on any potential concerns for the protection of these
species during or following restoration.
The Atlantic Coast Joint Venture (“ACJV”) conservation goal for the Saltmarsh Sparrow is to halt the
steep population decline and recover their population to 25,000 birds by restoring and enhancing
existing salt marsh patches to provide high-quality nesting habitat and to protect adjacent, inland areas
that buffer existing salt marsh patches and provide corridors to allow marsh migration in the future, as
sea level rises (Saltmarsh Sparrow Conservation Plan 2020). This proposal does this by applying the
three innovative ACJV recommended strategies—ditch remediation, addressing waterlogging through
construction of micro-runnels to improve and expand high marsh habitat, and creation of
microtopography to create potential nest sites that will reduce one of the primary drivers of population
decline – nest site flooding.
The Saltmarsh Sparrow Habitat Prioritization Tool indicates that while there are very few marshes in the
saltmarsh sparrow breeding range that provide high quality habitat to support population growth, the salt
marsh tracts in the proposed project area are above or well above average for resilience when compared
to other sites under the scenario of SLR increasing by 6 feet. This tool recommends focusing management
efforts on the top 20% of ranked patches as these are most likely to provide the greatest benefit to
Saltmarsh Sparrow over the long term.
The dire combination of sea-level rise and the marsh-wide legacy of ditching and embankment points to
a clear urgency for enhancement and restoration of habitat. Interventions must begin now and at a
landscape scale if efforts to save the species from extirpation are to succeed.
11. Best Management Practices
The most important best management practice is to proceed slowly with adequate monitoring during
construction to anticipate and adapt in order to avoid any unintended adverse effects.
1. Timing and Schedule
• All restoration measures will occur during neap tide cycles to ensure the marsh plain is not
flooded.
• Work will comply with time-of-year (TOY) restrictions as determined through consultation with
the MassWildlife – NHESP.
2. Use of Equipment and Materials
• Temporary timber mats will be used to minimize peat compression and vegetation disturbance.
Mats will reduce equipment ground pressure to below 2 psi and will be leap-frogged as needed.
• Mats will not remain on the marsh overnight
• Care will be taken to minimize trampling of vegetation by all personnel during implementation
and monitoring phases.
• Material or equipment staging will not occur on the marsh except as necessary for constructing
micro-topography islands.
3. Monitoring and Adaptive Management
• Pre- and post-implementation monitoring will be conducted. Adaptive management plans will
be implemented if unintended conditions arise.
4. Equipment Refueling
• Refueling will occur in high-elevation areas with no standing water, at least 10 feet away from
pools, ditches, or creeks.
• Fuel must be pre-mixed outside wetland resource areas and stored in 5-gallon Type 2 Safety fuel
cans.
• Only two 5-gallon containers are allowed in the marsh at a time, stored in a contained sled or
container with a spill kit.
• Absorbent pads will be used under fueling tanks to mitigate potential spills.
5. Invasive Species Management
• All materials and equipment will be inspected before entering the marsh to avoid introducing
invasive species.
• Invasive species will be removed manually, bagged properly, and disposed of off-site to prevent
further colonization.
6. Compliance and Funding
• Adequate funding will be ensured for successful implementation, monitoring, and addressing
unforeseen conditions.
• The project will comply with all permit conditions, approvals, and authorizations.
12. Alternatives Analysis
Several alternative project designs were evaluated as required by MEPA which are described below.
12.1 Alternative 1 – Proposed Action
The Proposed Action is part of an accelerated pace of statewide salt marsh restoration to assist
marshes in adapting to increased flooding and inundation expected with the next Metonic peak cycle
(2030 to 2040). Nine years of monitoring data from USFWS and three years of monitoring from The
Trustees sites provides strong evidence that proposed restoration techniques will work in
conjunction with natural marsh processes, providing tidal flooding and sedimentation needed to
assist the marsh in keeping up with SLR. The restoration will reduce or eliminate the clogging of
ditches and impounding of water currently occurring with legacy marsh management infrastructure
in place; restoring a channel network that is in equilibrium with the marsh area being flooded and
drained, and a flooding and ebbing hydrology that will sustain S. patens and S. alterniflora and
accelerated marsh accretion. It is expected that high marsh communities (S. patens, Juncus gerardii,
Distichlis spicata) will dominate for the next 20 to 30 years under this alternative. Under the
Proposed Action, we also expect to see a significant benefit to salt marsh peat. The peat within the
treatment areas will be returned to more natural inundation cycles, reducing the oxidation
subsidence currently occurring along exposed accessory ditches and allowing it to grow in elevation
This restoration project will also contribute significantly to the viability of the Saltmarsh Sparrow
population, which is expected to reach a critical threshold by 2030. Marsh restoration efforts will
increase potential habitat to sustain this imperiled species, giving it more time to adapt to changing
habitat conditions.
The increased pace of salt marsh restoration will maintain the vegetated marsh platform for more
decades than under the No Action Alternative. At some point, the rate of SLR rise may outpace the
ability of the marsh plants to trap sediment and increase biomass production, but restoration is
intended to delay that threshold for several decades.
The Massachusetts Healthy Soils Action Plan (2023) identifies restoring natural hydrology to promote
vegetation development and sediment trapping as a key priority for the State’s restoration efforts in
coastal wetland ecosystems.
12.2 Alternative 2 –Ditch Remediation Only Alternative
Elimination of runnels from the suite of restoration measures proposed would result in a significant
reduction in the ability of the project to address subsidence due to excess inundation, referred to as
WST described in Section 6 and Appendix 1. Without runnels, it would not be possible to restore a
hydrological network that is in equilibrium with the tideshed, and there is likely to be increased
inundation and marsh loss in the next decade or two as marsh area becomes wetter as ditches are
remediated without a pathway for the excess water to ebb.
The proposed construction of runnels results in a total of 0.21 acres of temporary alteration of marsh
surface, but it has the potential to directly enhance and restore a much larger area. For example, the
USFWS Ditch Plug Removal pilot demonstrated that removing 12 square feet of peat for construction
of two runnels resulted in restoration of 32,670 square feet of healthy marsh platform (DiNunzio et al.
2023, page 9).
Without the runnels, the project also loses the opportunity to support and enhance rare species
habitat through the construction of nest islands for a population experiencing precipitous decline.
12.3 Alternative 3 –No Microtopography Alternative
Alternatives to microtopography mounds include:
• Spreading the sediment across the marsh surface in thin-layer applications rather than
as mounds. It may be useful in areas where excavated runnel sediment is particularly
wet and unconsolidated and not well vegetated. This approach does result in a small
increase in marsh elevation and potential high marsh, but not enough to result in the
creation of suitable nesting habitat for saltmarsh sparrow.
• Constructing nesting islands in upland locations, which is not compatible with the
upland soil material (mainly sand). The salt marsh sparrow is dependent entirely on salt
marsh for nesting, so this solution does not provide suitable habitat.
• Eliminating the microtopography component of the project, which would require the
removal of material excavated from the marsh during runnel construction, resulting in a
net loss of sediment, and greater potential for impacts due to the significant additional
movement of material and equipment across the marsh. Sediment critically needed to
support a marsh losing elevation in the face of sea level rise would be removed from
the system. Elimination of this technique would hinder marsh resiliency goals and the
ACJV conservation goal of recovering the Saltmarsh Sparrow population to 25,000 birds.
However, thinly spreading some sediment under the proposed alternative may offer
flexibility in achieving project objectives.
12.4 Alternative 4 - No Action Alternative
The “No Action” Alternative simply allows the existing trajectory of subsidence to continue with
expanded areas of marsh transitioning to unvegetated or thinly vegetated mudflats and the
continued development of open water. This condition has already begun to adversely impact
the marsh’s ability to provide resiliency from coastal storms and rising sea level.
Marsh loss from soil waterlogging subsidence (associated with agricultural legacies interacting
with accelerated sea level rise) is an indirect human impact that, if not addressed, will soon
become the largest cause of salt marsh loss in the Commonwealth. There is a short amount of
time to implement measures to stem the losses given that the next upswing in astronomical
tides begins in 2026. As observed in the last Metonic peak (see above discussion on Metonic
Cycle), accelerated marsh changes are expected from 2030-2040, and without proposed
intervention to restore tidal hydrology in balance with marsh processes, it is likely marshes will
lose a significant portion of their vegetated platform, resulting not only in losses in biological
and ecological values, but an increase in the vulnerability of roads and infrastructure in
neighboring communities due to storm damage. Without action, other more invasive and
expensive restoration methods may become necessary, such as direct sediment placement,
which would have greater impacts on all wetland functions and values.
Recent investigations have determined that much of the saltmarsh hydrology has been altered
by past agricultural (salt marsh haying) practices (Adamowicz et al. 2020) and mosquito control
practices. Ditches and embankments created by past farming practices and mosquito control
districts either drained or inundated the upper root zones, has led to decomposition or
vegetation dieback, and subsidence of wetland soils.
Without comprehensive tidal restoration to most of the marsh, we expect to see multiple areas
of vegetation dieback and peat subsidence under this Alternative, particularly coupled with
increased flooding with peaks in the Metonic cycle.
13.Pre and Post Restoration Data Collection and Monitoring
The monitoring protocol for this project is based on lessons learned from previous projects,
comments and feedback from agency review of previous projects, monitoring expectations for in-lieu
fee mitigation projects, and MassDEP guidance. Monitoring is divided into three general categories:
1) Baseline Conditions Pre-implementation Data Collection Plan
This focuses on establishing benchmarks of existing conditions to assess marsh response from
restoration activities in the future. It includes hydrologic, vegetative, elevation and accretion
measurements at locations proposed for both ditch remediation and runnels, as well as a no
treatment or reference area located directly to the west and owned by the Town of Barnstable.
2) Construction Period Monitoring
This focuses on maintaining quality control and compliance with permit conditions. It
anticipates that construction activities will be monitored weekly during active stages of
restoration by an approved monitor with experience in salt marsh ecology and specifically the
restoration techniques proposed by this project with reporting to agencies as required by
permits.
3) Post Construction Monitoring
The focus of this effort is to not only continue to evaluate whether the project continues to meet
permit requirements and established success criteria, but to assess longer term marsh response
to restoration techniques. The post-construction monitoring plan proposes to employ the same
methods as Baseline Monitoring each year for at least 5 consecutive years following initial
implementation.
4) Priority 2 Pilot Monitoring
This effort involves specific monitoring of Priority 2 area pilot runnels as described in Section 15
below.
13.1 Baseline and Post-Construction Monitoring
Baseline monitoring was described briefly in Section 7 Existing Conditions above and was conducted
primarily by APCC and EA in 2023-2025. The following is a summary of proposed monitoring methods.
For the complete report on baseline monitoring, including results and discussion, please refer to
Appendix 2.
The Monitoring Plan was developed based on key metrics and criteria established by regulatory agencies
including MassDEP, CZM, and USACE and techniques employed at previous SMARTeams restoration
sites. The following components are included:
Hydrology: Hydrologic monitoring of water levels in the project area was conducted to establish baseline
surface water and groundwater levels for an entire lunar cycle from October 25-December 1, 2023. Water
level monitoring stations were selected based on proximity to proposed ditch remediation and runneling
locations with no other proposed restoration treatments within roughly 100 ft and a ditch that drained in
only one direction. The stations in the control area of the marsh were chosen to be similar to the
restoration sites in elevation, ditch size, and proximity to both the upland edge and main channels.
Seven water level loggers (Solinst Levelogger 5, Model 3001) were deployed: two measuring groundwater
elevation and one measuring surface water elevation in the control area, and two measuring groundwater
elevation and two measuring surface water elevation in the restoration area. Because of the proximity of
the transects in the control area, only one surface water station was deemed necessary to record full tidal
fluctuations and flooding in the ditch and on the marsh platform. The surface water stations were affixed
to metal stakes that were driven ~2 ft deep into the sediment bed. The groundwater wells (or piezometers)
were designed to prevent clogging and encourage drainage. They were screened by drilling 1/8- and 1/4-
inch holes roughly 1/2 - to 1-inch apart throughout the lower 60cm of the 1-meter PVC. The holes were
covered with garden mesh fabric, and they were installed roughly 60cm deep and 1 meter from the edge
of the ditch and within 5 m of a transect.
Figure 13.1: Photos of the groundwater well (or piezometer) design (A – mesh
fabric not shown), placement of control-ditch groundwater well (B), and
installation of surface water logger in ditch during ebb tide (C). Photos from
APCC
A barometric pressure logger (Solinst Barologger, Model 3001) was deployed during the same
period as the water level loggers to convert absolute pressure collected by the water level loggers
to water depth that’s corrected for atmospheric pressure. The elevation of the groundwater wells
and creek stakes was surveyed using a Trimble Geo7x and antenna attachment with centimeter
accuracy (NAVD88 ± 3cm). Further adjustment to improve relative accuracy was necessary using
the high-water maximum from the respective surface water logger dataset.
Vegetation: Transects were established perpendicular to the proposed restoration treatment
(i.e., across ditches and proposed runnels). Placement of transect replicates (6 per treatment type,
in the action and control marsh for a total of 24) were determined with input from SMARTeam
members, Mass Audubon staff, and other project partners (Figures 14.2 and 14.3).
Figure 13.2: Map of the Action marsh where the Phase 1 restoration plan will be implemented. (APCC)
Figure 13.3: Map of the Control marsh meant to act as a no-action reference for comparing restoration effects
in the Phase 1 restoration, or Action, area.(APCC)
Control transects were located where the drainage conditions (i.e., vegetation), channels widths
and spacing, and elevation gradient were comparable to those within the restoration area. The
two ends of each transect were marked with wooden stakes. Each transect was 20 m long, with
the center point at 10 m. The center plot was either over the middle of the ditch or over the
approximate runneling location. One end of the transect was designated as “0 m” and flagged to
orient individuals. The “walking side” and “plot side” of each transect was determined when the
transects were initially established to avoid disturbance of monitored plots. The transects were
labeled for their intervention type and replicate number. For example, D-A-5 is “Ditch Action –
Replicate 5” and R-C-2 is “Runnel Control – Replicate 2”.
Teams of APCC staff, Mass Audubon staff, and volunteers assembled to characterize vegetation
cover types at nine (9) half-meter-square (0.5 m2) plots along each transect (placed at 0m, 5m, 8m,
9.5m, 10m, 10.5m, 12m, 15m, and 20m) in August 2023 (total = 216 plots).
Each team recorded percent cover by species (including other cover types such as bare sediment,
dead, standing water, wrack, and macroalgae) and the height of the five tallest stems of S.
alterniflora in each plot. Percent covers were determined at each plot to the nearest 1% (0.5% in
cases of trace covers). Photos were taken of each individual vegetation plot and of the entire
transect from the 0 m stake and perpendicular to the transect.
Elevation: Cross-section elevation measurements were collected along all transects in the action
and control areas. High accuracy (<1mm) relative elevation measurements were collected with a
Leica digital level and tied to the North American Vertical Datum (NAVD88) using reference
benchmarks surveyed with a Trimble Geo7x and Zephyr 2 antenna (± 3cm). The GPS coordinates
(x,y) of each plot and marker horizon were also collected with the Trimble Geo7x device. Elevation
measurements were collected along each transect at 0, 5, 8, 8.5, 9.5, 10, 10.5, 11.5, 12, 15, and 20
meters to correspond with the placing of vegetation plots and marker horizons. For transects that
crossed ditches, measurements were also collected at additional locations where there were
significant slope or elevation changes. The goals of precise elevation measurements were to
establish a baseline of each plot’s vertical position which will be used to track changes expected
over time and assess the effect of the respective restoration treatment.
APCC also collected horizontal measurements (width and length) of depressions, defined as
pooled areas where there was significant standing water during low tide, which were within 10m
of the transect. Elevation and GPS measurements of the ditches provided dimensions of each
control and action ditch replicate. These baseline data will be used to measure change in these
feature dimensions over time.
Accretion: Marker horizons, used to measure sediment accretion over time, were placed at four
randomly selected ditch remediation and runnel transects in the action and control areas (32
total). These marker horizons were installed by evenly spreading 1L of feldspar powder inside a
0.25 m2 plot on opposite sides of the transect center (1.35 m from the center). To measure marsh
accretion, sediment cores can be sampled at the location of the marker horizon, and the contrast
of the white feldspar against the dark, organic-rich peat provides a reference to measure the
accumulated organic matter and sediments using calipers.
In 2024, APCC returned to the marker horizon plots on July 25th (action plots) and August 8th
(control plots). The 0.25 m2 quadrat was positioned between the two wooden stakes placed at
diagonal corners at each plot. Teams of two estimated percent cover by plant species and other
cover types (i.e., bare sediment, dead plants, and wrack) and measured the heights of the three
tallest S. alterniflora stems within the quadrat. To measure sediment accretion, a small (~2- inches
in width and 3-4-inches in length), conical sediment core was cut with a serrated knife and
extracted with a trowel from the right corner of the plot closest to the transect, unless a notable
disturbance was present, like a crab burrow. The core was placed on a hard surface and split down
the middle using a sharp, non-serrated knife. The marker horizon was identified by the appearance
of a line of feldspar. Accretion was measured using traceable digital calipers to record the distance
between the upper limit of the feldspar line and the surface of the sediment. Three measurements
were collected from each core and later averaged to calculate a single accretion rate (mm/year) per
plot. The three measurements were collected where there were clean (undisturbed) edges of
feldspar and sediment.
Dimensional Monitoring: The depth of treatment ditches and the potential formation of clogs will
be monitored and addressed during the monitoring period. Runnels will be monitored to
determine the extent of any channel dimension changes. The size and height of microtopography
mounds will also be measured to ensure that they stay within design parameters. The entire
project area, but especially the microtopography mounds will be monitored for presence of
invasive species.
13.2 Construction Period Monitoring
As recommended by MassDEP guidance, Mass Audubon will employ an on-site monitor with the
recommended minimum 5 years of coastal wetland ecology experience to oversee the site
contractor and monitor compliance with permit conditions. Monitoring will include site visits to
ensure construction is occurring as designed and to identify any deviations from the original design,
contractor mishaps, problems occurring from severe weather events or other unforeseen scenarios.
Width and depth of runnels constructed and depth of hay placement in ditches will be noted. Any
changes in downstream morphology will also be noted. Bi-weekly monitoring reports shall be
prepared during periods of active construction activities and shall include photos of site conditions,
and recommendations for any corrective actions and measures to prevent the need for corrective
actions in the future. Monitoring reports will be provided to permitting authorities until the
completion of work and site stabilization has occurred according to project objectives.
13.3 Saltmarsh Sparrow Monitoring
Point counts were conducted by Mass Audubon in 2024 and 2025 with previous point counts by
SHARP. These counts will continue throughout the monitoring period. In addition, observations will
be made prior to construction to avoid impacting these species and time of year restrictions will be
maintained as required by NHESP.
14. Corrective Action Plan
Successful implementation of the proposed restoration will result in a hydrological network in
equilibrium with the tideshed with minimal clogging of channels and the beginnings of natural sinuosity
developing in the newly established channels. Lessons learned from past projects will minimize the need
for on-going maintenance, such as the need to remove clogs. The construction monitoring reporting
from the Environmental Monitor and the post-construction monitoring plan will identify whether
corrective actions are needed. The Success Criteria Table below identifies when thresholds being
monitored require consideration of corrective action and what those actions should be. Corrective
actions may be necessary due to inadvertent impacts such as those unforeseen or a result of contractor
error or may be necessary because of natural marsh processes such as coastal storms. MassDEP’s
guidance for marsh restoration classify these as Category 1 and Category 2 corrective actions. The
project proposes the following framework for corrective actions:
Category 1: These may include impacts from unintentional construction impacts or changes in design
above established thresholds in the Success Criteria Table and require additional review and
consultation by the reviewing agencies.
Category 2: These are actions that include anticipated maintenance such as unclogging of runnels,
extension of runnels to adjust for site specific conditions between design and implementation, addition
of hay to treatment ditches, maintenance of marsh habitat mounds. These actions should be reported
to agencies as part of the normal construction and post-construction monitoring reports but are not
recommended for further regulatory review.
The following specific potential Category 2 corrective actions are proposed for each restoration method.
14.1 Runnel Implementation
Aspects of runnel implementation proposed to be monitored include hydroperiod, vegetation, and
channel morphology as described in the proposed Monitoring Plan in Section 9 above. The monitoring is
to ensure that the ditches, pools, and marsh platform surrounding the runnel areas maintain the
following characteristics:
• Ebb and flow with minimal tidal lag or restriction
• Absence of clogging or uneven sediment deposition that leads to clogging
• Groundwater drained to 15-25 cm below the surface at all but spring tides
• Vegetation cover increasing with corresponding decrease in unvegetated areas.
To ensure runnel dimensions are constructed according to design specifications, as-built dimensions will
be collected by a qualified person either at time of construction or within the same growing season.
Lessons from past projects have identified measures which will minimize the need for ongoing
maintenance, such as the need to remove sediment deposition or clogs. Longer runnels or runnels with
more bends and turns prior to discharging will receive particular attention to assess for potential
clogging. The placement of runnels within historical ditch channels and correctly sizing the runnels
prevents these occurrences. In a case where clogging occurs, the channel dimensions will be reviewed
first to determine if further tidal flow will naturally release the obstruction. If that is not likely to occur,
obstructions are proposed to be removed using hand tools. Post-construction monitoring will identify
whether any corrective action is needed.
The project is designed to allow runnel channel dimensions to adapt over time to accommodate the new
tidal flow, as occurs naturally when pools breach into intersecting channels. To assess channel evolution
of constructed runnels, the Monitoring Plan incorporates monitoring of dimensions at the time of
construction, then again during years 1,2 and 3 post-construction. Measurement of channel dimensions
extends to second and third order channels downstream of runnels only where the subtideshed to the
runnel exceeds 2.47 acres, consistent with the Mass DEP 2024 guidance document on salt marsh
restoration. The corrective actions for excessive scouring can include installing a sill at the head of the
runnel using material from the channel or an adjacent embankment up to but not higher than MHHW
to reduce flow, installing a weir using natural material such as sticks and plant debris along the sides of
the channel to slow down flow and encourage sinuosity, planting the channel with S. alterniflora to slow
flow, or investigating whether an additional runnel is needed to provide an additional or alternative
drainage path. Correctly sizing the runnels minimizes the potential for clogging and post-
construction maintenance. However, in a case where clogging occurs, the channel dimensions will
be reviewed first to determine if further tidal flow will naturally release the obstruction. If that is
not likely to occur, obstructions are proposed to be removed using hand tools. The project is
designed such that runnel dimensions may change over time to accommodate the new tidal flow.
This channel evolution has been observed in channels intersecting naturally breached pool s. To
assess channel evolution of constructed runnels, the Monitoring Plan incorporates monitoring of
as-built dimensions, then years 1 through 5 of post- implementation monitoring. The corrective
actions for excessive scouring may include installing a sill at the head of the runnel using material
from the channel or an adjacent embankment up to but not higher than MHHW to reduce flow,
installing a weir using natural material such as sticks and plant debris along the sides of the channel
to slow down flow and encourage sinuosity, planning the channel with S. alterniflora to slow flow,
or investigating whether an additional runnel is needed to provide an additional or alternative
drainage pathway.
14.2 Ditch Remediation
This project incorporates many lessons learned from past pilots to prevent need for corrective action.
Examples include sloping the hay such that sedimentation does not cause clogs in the middle of the
ditch, capping the maximum depth of treatment to ensure solid formation of peat through the ditch,
and staggering treatments by at least six months to allow sediment to accumulate prior to installing
additional hay. Should clogs develop, corrective actions include re-arranging and re-staking the salt hay
by hand to eliminate obstructions. Ditch dimensions pre and post-treatment will be monitored as part
of the post-construction monitoring, allowing for an understanding of accretion rates between
treatments. A treated ditch is considered successful when there is >50% colonization by salt marsh
plants. Data loggers described in Section 9 above will provide an opportunity to assess inundation,
groundwater hydroperiod and the potential formation of lateral hydrology.
14.3 Microtopography Mounds
These islands, created with material excavated from runnel excavation, must be constructed so that
they continue to function as high marsh. Elevations too high will result in colonization by non-salt marsh
species and increase risk of introduction of invasive species. During construction, contractors will
establish the highest elevation point of the salt marsh that contains native salt marsh vegetation, and
construct the island elevation to be below that reference point generally at or near MHHW elevation. In
case of colonization by non-native or non-salt marsh species, mound height can be adjusted using hand
tools and excess material spread around the base of the mound. Any invasive species present on the
mounds will be treated using mechanical or chemical means. The success criteria included in Table 14.1
anticipates >75% vegetative cover with native salt marsh plants. If an island does not revegetate within
two growing seasons, the flooding regime will be investigated and adjusted as needed.
Other construction techniques to minimize the potential for corrective actions include carefully shaping
and blending the mounds to the marsh surface to avoid the potential for movement during winter
flooding prior to full re-establishment of vegetation. Occasionally it may be necessary to stake the
mounds to prevent migration during the first season if they are not well vegetated going into the first
winter season.
51
15. Proposed Priority 2 Pilot Program
Concerns were raised by agencies during the MEPA process regarding the proposed earlier intervention
of runnels proposed in Priority 2 areas. To review, Priority 2 areas are those located in areas of the
marsh which have not yet experienced advanced subsidence but are experiencing early-stage
subsidence (refer to Appendix 1 for a description of the Oxidation Subsidence and Waterlogged
Subsidence Trajectories). These areas exhibit evidence of marsh decline such as loss of thatch, changes
in vegetation density or vegetation composition (such changes from S. patens to short form S.
alterniflora) indicating more frequent or sustained inundation but not yet permanent ponding. Based
upon the current marsh trajectory, scientists anticipate the further degradation to Priority 1 status could
occur within 5-15 years.
Mass Audubon proposed including Priority 2 runnels in the initial construction phase to reduce the time
needed to provide maximum stabilization of marsh surface hydrology. The intention of implementing
these runnels together with the runnels in Priority 1 areas was to maximize the potential marsh
response to the restored hydrology within each individual subtideshed of the project site. Intervening in
this earlier stage was proposed to minimize the potential for future further subsidence by allowing full
tidal exchange and sediment transport to the restoration area.
Elimination of all Priority 2 runnels was initially suggested by Mass CZM and Mass DEP until the point
where marsh conditions degrade to the point where they meet the Priority 1 definition. However,
waiting for further degradation is the opposite of the trend this project is intended to address. Earlier
intervention in the subsidence trajectory is intended to prevent this additional subsidence and provide
the marsh with the best opportunity to continue to accrete.
As a result of these discussions, Mass Audubon proposed construction of only a portion of the Priority 2
runnels in the initial phase of restoration, and continuing to monitor to determine the need for
completing the remaining Priority 2 area runnels or other corrective actions.
The current design proposes 23 runnels within Priority 2 areas, which is approximately 1/3 of the 70
total proposed runnels and represents 1,341 linear feet or runnel compared with 2,043 linear feet of
Priority 1 runnels. The total watershed area proposed to be influenced by Priority 2 runnels is
approximately 5.7 acres (7.4%) of the 76.5 acre project site.
To address agency concerns that Priority 2 runnels may result in temporary construction related impacts
that may not be off-set by restoration goals or that this technique may result in additional or
unnecessary marsh impacts, Mass Audubon proposes that 50% (12) of these Priority 2 runnels, as
shown on the attached annotated site plan, with Pilot and Delayed runnels highlighted in dark blue and
light blue respectively. The Pilot runnels, proposed to be installed in the initial phase of project
construction, include 2 lateral expansion runnels and 10 headward extension runnels. The remaining 11
Delayed runnels are proposed to be installed only after at least two years of monitoring and only as
monitoring demonstrates additional decline meeting Priority 1 requirements in the area of the proposed
runnel and the Pilot Runnels to not exhibit. Construction of these remaining runnels would be
conducted as part of the Corrective Action Plan as described in section 14 of the EENF, with agency
notification to DEP and CZM as required by the Category 1 adaptive management measures.
The Construction Sequence Timeline (Table 16.1) below has been modified to recognize this approach.
his timeline addresses agency concerns by slowing implementation of Priority 2 area runnels to allow for
collection of additional data on this approach but still allows the project proponent to complete most of
the work proposed to be contracted in a single effort.
A monitoring protocol and success criteria have been developed to specifically monitor
Priority 2 area runnel locations in Section as described below. The site plans have been
modified to depict the location of the proposed pilot runnels.
1. Proposed Monitoring of Implemented and Unimplemented Priority 2 Runnels
Monitoring of the ground and surface water elevations at the 12 proposed Priority 2 runnel treatment
sites and the 11 delayed or untreated Priority 2 sites would be conducted by installing monitoring wells
equipped with water level recorders (WLRs) within 6-8 feet of 3 of the Pilot Runnels and 3 of the
uninstalled (control) runnels. Data will be collected for a minimum of one lunar cycle in addition to the
baseline monitoring already conducted for this project. Post implementation field monitoring of these
sites will be conducted for general observation of marsh response, with specific hydrologic and
vegetative data collected at all of the Pilot and control runnel sites. In addition, the following additional
monitoring will be conducted to allow for assessment of success criteria that will determine the future
scope of work.
1. Transect Surveys: In the 2 locations where Priority 2 runnels are proposed perpendicular to ditch
remediation (i.e., lateral runnels) ditch bottom elevation from the marsh surface will be
measured at several locations within 100 feet of the runnel. Runnel width and depth will be
recorded at multiple locations along the Priority 2 lateral runnels both following installation and
during each successive year of monitoring to track runnel stabilization.
2. In the 10 locations where Priority 2 runnels are proposed as headward extension runnels, runnel
width and depth will be recorded at multiple locations along the runnel following installation
and during each successive year of monitoring to track stabilization.
3. Groundwater monitoring: WLRs will be installed at 3 locations within the Pilot Runnel and 3
locations at the Untreated (control) Priority 2 runnel sites. Post-implementation water levels
will be recorded annually for 5 years in addition to the other groundwater monitoring proposed
for the Priority 1 areas.
4. Stem Count Plots: Survey plots will be established in 5 Priority 2 areas where a Pilot Runnel is
proposed and 5 locations at the Untreated runnel sites. Baseline stem counts will be taken for
comparison. Vegetation will be characterized in each plot with density monitored through stem
counts.
5. Walking Surveys: A walking survey will be performed at each Priority 2 location where a runnel
is proposed. These surveys will focus on identifying any adverse effects. (e.g, runnel blockages,
erosion, etc.).
6. Photo Monitoring: Photos will be taken from the same location each year of monitoring
(including baseline) at all selected monitoring sites. Photo-monitoring will focus on identifying
changes over time, with specific emphasis on Priority 2 areas.
Success Criteria for Runnels Associated with Ditch Remediation (Lateral Expansion Runnels
The success criteria for runnels associated with ditch remediation predict that groundwater will initially
rise to the elevation of the runnel within two to three years following ditch remediation, then stabilize
where root zone flooding will be at less than 80%. The bottom elevation of the remediated ditch should
also rise at a rate faster than areas without Priority 2 area runnels such that the bottom elevation of
remediated ditches is <20 centimeters (cm) below the marsh surface in Year 3 rather than Year 5, and
vegetation has responded accordingly.
Runnels Not Associated with Ditch Remediation (Headward Extension)
The success criteria for Priority 2 area runnels not directly associated with ditch remediation will follow
the same general success criteria as Priority 1 runnels. However, since these areas are in early-stage
decline and have not yet reached water-logging conditions, hydrologic changes are expected to be more
subtle. The Year 1 target for percentage of time where flooding is observed is anticipated to be zero
rather than the 10% anticipated in Priority 1 areas, and the 80% root zone flooding target is anticipated
to be achieved in Year 2 in Priority 2 areas as opposed to Year 3. Vegetation cover is also anticipated to
increase by 10% by Year 2 rather than Year 3.
16. Proposed Contracting and Restoration Timeline and Logistics
Mass Audubon expects restoration to be implemented from March 2026 to November 2027,
assuming final approvals are obtained before then. Follow-up ditch remediation treatments may
extend into 2028. No mowing or work using heavy equipment will occur during any time of year
restrictions established by NHESP. To maximize marsh response and minimize impacts, the
restoration techniques will be implemented as follows.
In general, ditch remediation will be conducted first, prior to installation of runnels. Depending on
the depth of ditches to be remediated, it can take 4-5 treatments to reach final design elevation.
Where multiple treatments are required, they will be spaced at least six months apart to provide
sufficient opportunity for sediment capture within each treatment layer.
Microtopography creation will always be done at the same time as runneling to avoid stockpiling of
material. Sediment will be placed directly by the excavator. If signs of peat compression or
vegetation impact are observed, equipment used to transport sediment is to cease immediately,
and size and location of planned islands will be adjusted accordingly.
Access paths are selected for the least impact to the marsh (most direct path over firmest marsh
area, one way route whenever feasible). Staging areas for materials and equipment will be outside
of the salt marsh on the uplands owned by Mass Audubon. These areas will be used to stockpile
materials (stakes, baler twine, mats, fuel etc.) and to bring equipment out of the marsh every day
at the conclusion of work. Access to the staging area will be through the BBGM Wildlife Sanctuary
entrance off of Cranberry Highway (Route 6A). An existing access path from the sanctuary entrance
to the project area will be available for use by the construction contractor. Some minor pruning of
low-hanging branches may be needed along this access route.
Assessments will be made during and following construction to determine the need for any
adaptive management measures (aka corrective actions). These are described in Section 15 above.
The following construction and monitoring schedule is based upon obtaining all required
permits by March 2026.
TABLE 1 6 .1. CONSTRUCTION SEQUENCE TIMELINE W I TH P IL O T R U N NE LS
Contract
Administration
and
Mobilization
Priority 1 Runnels
&
microtopography
And 50% Priority 2
Runnels
Ditch
Remediation
Monitoring Priority 1
Monitoring Priority 2
Spring 2026
X
X
X
Pre-restoration monitoring completed,
quality control and rapid assessment
Baseline transect surveys, stem count plots and
water level recording
Summer 2026 X X Quality control and rapid assessment Quality control and rapid assessment
Fall/Winter 2026
X
X
Quality control and rapid assessment
Quality control and rapid assessment
Spring 2027
X
Year 1 Post Monitoring for areas
completed in 2026
Year 1 post monitoring for areas completed in 2026
Summer 2027
X
Quality control and rapid assessment
Quality control and rapid assessment
Fall/Winter 2027
X
Quality control and rapid assessment
Quality control and rapid assessment
Spring 2028
X
Year 2 Post Monitoring for areas
completed in 2026 and year 1
monitoring for areas completed in 2027
Implementation of Additional Priority 2 runnels if
warranted. Year 2 Post Monitoring for areas
completed in 2026
Summer 2028
X
Quality control and rapid assessment Quality control and rapid assessment
Fall/Winter 2028
X
Quality control and rapid assessment
Quality control and rapid assessment
Spring 2029
X
Year 3 post monitoring for areas
completed in 2026, Year 2 for areas
completed in 2027 and Year 1 for areas
completed in 2028.
Implementation of Additional Priority 2 runnels if
conditions warranted. Year 3 Post monitoring for
areas completed in 2026, Year 2 for areas
completed in 2027 and Year one for areas
completed in 2028
Summer 2029 X Quality control and rapid assessment Quality control and rapid assessment
Fall/Winter 2029 X Quality control and rapid assessment Quality control and rapid assessment
Spring 2030 X Year 4 post monitoring for areas
completed in 2026, Year 3 for 2027, Year
2 for any units completed in 2028 and
Year 1 for any units completed in 2029.
Year 4 post monitoring for areas
completed in 2026, Year 3 for 2027, Year
2 for any units completed in 2028 and
Year 1 for any units completed in 2029.
Spring 2031 X Additional monitoring to reach 3 years
for all areas as needed.
Additional monitoring to reach 3 years
for all areas as needed.
Contract Administration
and Mobilization
Runnels &
microtopography
Ditch
Remediation
Monitoring
Spring 2026
X
X
X
Pre-restoration monitoring completed, quality control and rapid
assessment
Summer 2026 X X Quality control and rapid assessment
Fall/Winter 2026
X
X
Quality control and rapid assessment
Spring 2027
X
Year 1 Post Monitoring for areas completed in 2026
Summer 2027
X
Quality control and rapid assessment
Fall/Winter 2027
X
Quality control and rapid assessment
Spring 2028
X
Year 2 Post Monitoring for areas completed in 2026 and year 1
monitoring for areas completed in 2027
Summer 2028
X
Quality Control and rapid assessment
Fall/Winter 2028
X
Quality Control and rapid assessment
Spring 2029
Year 3 post monitoring for areas completed in 2026, Year 2 for areas
completed in 2027 and Year 1 for areas completed in 2028.
Summer 2029 X Quality Control and rapid assessment
Fall/Winter 2029 X Quality Control and rapid assessment
Spring 2030 X Year 4 post monitoring for areas completed in 2026, Year 3 for 2027, Year
2 for any units completed in 2028 and Year 1 for any units completed in
2029.
Spring 2031 X Additional monitoring to reach 3 years for all areas as needed.
17. Quality Control and Assurance of Contracted Work
This project was designed by Geoff Wilson, principal of NWR and Mass Audubon staff. The construction
contractor is expected to be selected through a bid process. Priority will be given to contractors who
have completed the SMARTeams restoration training or can demonstrate experience operating on salt
marshes with the equipment necessary to complete this work. Implementation may also be conducted
by a trained field team with expertise in these restoration techniques.
A restoration coordinator will be identified by Mass Audubon to oversee project implementation and
monitoring and will provide weekly and monthly reporting to agencies as may be required by permits.
Mass Audubon will seek to retain EA to assist with construction oversight services for the project due
to their familiarity with the project site and restoration design. Other entities who have knowledge and
experience pertaining to the construction of salt marsh restoration projects may be considered as an
alternative. Similarly, Mass Audubon will seek to engage APCC or a similarly qualified entity to assist
with post-construction monitoring services for the project. Additionally, Mass Audubon's Ecological
Restoration Program will provide a project manager experienced in coastal ecology to coordinate
between project contractors ,project partners, and local stewardship staff for the project site.
18. Compliance with MassDEP Salt Marsh Restoration Guidance
The following are excerpts (in italics) from MassDEPs June 18, 2024, Wetlands Program Guidelines under the Mass.
Wetlands Protection Act and Water Quality Certification for Salt Marsh Restoration Techniques. Measures
proposed to comply with these recommendations are listed below each topic.
VI. Notice of Intent and Water Quality Certification Application Submission
1. A General Project Description that clearly states the need for the proposed project activities. Proposed
project alterations (temporary and permanent) should be described and quantified by wetland Resource
Area. The applicant must show that the project qua lifies as an Ecological Restoration Limited Project as
defined in 310 CMR 10.00 (future regulation changes may include a permitting pathway as an Ecological
Restoration Project). If a project is within a mapped polygon on the most recent Estimated Habitat Maps
of State-listed Rare Wetlands Wildlife published by the MA Natural Heritage and Endangered Species
Program (MNHESP), then MNHESP shall be consulted in accordance with 310 CMR 10.57 .
The EENF includes a detailed project description including a description of the restoration design process
(see Appendix 4) and the restoration methods (see Section 9). Alterations to resources are described (see
Section10) and summarized in Table 10.1. The project is similar to the Trustees Phase III project and will
be filed as an Ecological Restoration Limited Project Under 310 CMR 10.24(8)(e)(1). The entire project site
is within Estimated Habitat and NHESP will be contacted for comments regarding this project.
2. A Map depicting the project area and the proposed activities. The map should clearly depict the different
activities and areas requiring restoration. Proposed project phasing should be clearly shown on the map, if
applicable.
The EENF includes a USGS topographic quadrangle locus map (Figure 1) as well as site plans depicting the
entire project design. These plans show the locations of all ditches to be treated and runnels to be
created. The project is not intended to be phased but to be completed as one project. See Table 16.1 for
an estimated project timeline.
Construction timing is also influenced by time-of-year restrictions required by NHESP, as well as tide
cycles.
3. A Project Plan Set depicting the proposed project activities, including, as appropriate:
a. Existing and proposed elevation data [MassGIS Light Detection and Ranging (LiDAR) is sufficient but
some proposed work may benefit from more precise elevation data to ensure positive drainage].
Proposed elevation data can be provided as a typical detail fo r each type of restoration feature
proposed (e.g., cross-sections).
EA prepared design maps based on 2021 USGS LiDAR: Central Eastern Massachusetts data set which
represents the best quality LiDAR data in the vicinity of the project site. In addition, a subset of
proposed runnels was field surveyed by instrument survey. Typical runnel and ditch details are
included on Sheet C-501 of the project site plans.
b. Reach1 sub-basin (i.e., drainage area) delineations associated with runnel and ditch remediation
locations (USGS marsh units are acceptable, if appropriate, however, designs may rely on smaller
subbasins
Subtideshed boundaries established using CMUs identified by USGS have been provided in Figure 7.1.
These CMUs were also used to assist in developing UVVR as they rely upon analysis of surface
elevation slope derived from Digital Elevation Models (DEMs) and therefore are useful in preliminary
delineation of drainage areas as well as identifying typical plant communities (high marsh, low marsh
and unvegetated areas). There is some degree of error with this method as the boundaries of any
specific subtideshed can be difficult to identify remotely, particularly in areas of advanced
subsidence. For this project site, the CMUs appear to generally coincide with field identified
subtideshed boundaries.
The design maintains all existing subtideshed boundaries. Runnels are proposed in headwater areas
within the subtideshed, extending or restoring the reach of existing ditches to improve tidal
exchange. Because there may be several runnels proposed within the same subtideshed, these
individual runnels improve tidal exchange to a subset of the subtideshed, or a micro-tideshed.
Section IV.3 of the DEP Guidance recommends using 2.47 acres as a typical subtideshed size which
supports a tidal channel. Recent publication from J.G. McKown and D. Burdick (2024) indicates that
following monitoring of 17 marshes in Maine, Massachusetts and Rhode Island between 2010-2021
using public aerial imagery to document changes to the UVVR these sites had an average subtideshed
size of 2.12 ha (+/- .18) or 5.24 acres (see attachment for full article). The subtidesheds for this site
range from 3-20 acres. The larger subtideshed in the Guidance corresponds more accurately to the
average subtideshed area for what is defined as a “tidal channel”. According to the guidance, a tidal
creek restoration is defined as being created by constructing an undersized pilot channel, or where
flow from an existing ditch or tidal course is consolidated (such as through ditch remediation),
resulting in increasing the existing ditch or tidal course upgradient subtideshed.
In response to this comment, the runnels proposed for this project are headward extension runnels
which serve to extend the drainage throughout the subtideshed. They are not proposed as pilot
channels or “tidal channels.” They are intended to reconnect flow from micro-tidesheds into existing
primary channels in areas that have become isolated from the primary channel due to marsh
subsidence. There will be no change to subtideshed boundaries. This design allows both the
incoming tide to bring in sediment to the upper reaches of the subtideshed and to facilitate more
complete drainage on the outgoing tide within the same subtideshed. For this project, runnels are
are typically proposed within a micro-tideshed of 1-2 acres. In addition, proposing ditch remediation
to consolidate flow into an existing primary channel in combination with runnels within the same
subtideshed does not result in a significant increase in discharge to the downstream tidal channel
due to the fact that the restoration proposes to remove deep ditches (2-3’ +/-) through ditch
remediation, which are currently intersecting both surface flow and groundwater flow, to shallow
runnels (<1’), which are primarily intersecting surface flow.
For these reasons, we do not believe that the runnels proposed at this site qualify as tidal channel
restoration according to the guidance. Therefore no further evaluation of downstream channels is
indicated.
c. Proposed runnel depth and width in feet, runnel sub -basin size in acres, ditch remediation location and
length, approximate number and size of marsh habitat mounds, and quantity of sediment for reuse with
estimated cut / fill quantities. Exact locations of marsh habitat mounds and sediment placement areas can
be reported in the construction period monitoring report and the as built plan.
All runnels are proposed at 30-36 inches wide, and 8-10 inches deep (not including 2” thalweg) and are
located on the attached project plans. The number of treated ditches and runnels, total lengths and
approximate number of and size of marsh habitat mounds are shown in Table 3 of the ENF narrative .
Survey location of the start and end locations of 55 of the 70 proposed runnels has already been provided
as part of the pre-construction baseline documentation. Additional GPS location of remaining runnel
locations will be provided prior to construction. Following construction, restoration features will also be
documented, including: locations of the start, end and bottom elevation relative to the marsh surface for
all runnels, and the location, size and elevation of marsh habitat mounds. This information will be
provided as part of the construction period monitoring reports.
d. Proposed runnel categorization (e.g., temporary vs. permanent, various design sizes).
All runnels for this project are proposed to be permanent and are constructed to the same range
indicated in the Typical Runnel Detail (30-36” wide and 8-10” deep with a 2-inch thalweg). The runnels
begin at their upstream end at the smaller end of the range and broaden/deepen at the downstream end
to the maximum extent of the range to ensure a positive slope. Dimensions have been designed to be
consistent with a custom trapezoidal bucket on an excavator such as that employed by Northeast
Restoration to improve consistency in runnel dimensions. The deeper and wider range of the runnel is
automatically accommodated by the flare in the bucket.
In addition, runnels may be proposed in areas identified as Priority 1 which are experiencing late decline
or early waterlogging, or Priority 2, which are in early decline. Priority 2 runnels occur primarily as
headward extension runnels along the southern portion of the site extending toward the upland . No
lateral runnels for facilitation of ditch remediation are proposed at this site as the treatment ditches
appear to contain adequate lateral drainage.
e. Embankment (soil berm) locations from historic alterations (e.g., agricultural embankments, mosquito
control, etc.) to the extent feasible.
All embankment locations have been mapped as part of the preliminary design process. They are not
specifically located on the site plans, though some features are apparent by changes in topography
detected by the LiDAR based plan.
f. Field-verified subterranean ditch voids (see Appendix A) to the extent feasible, including ditches that will
not be remediated.
The presence of subterranean ditch voids was estimated first by review of recent and historic aerial
photography and again by field probing at the time of project design. In this way, the historic ditch
network could be mostly reconstructed. However, not all voids are visible in aerial photography, and it is
not feasible to probe all areas of the 76.5-acre project site to map them all. To avoid inadvertently
intersecting these voids, the design carefully avoids the ditch voids during runnel constructio n by
orienting ALL runnels to follow the present and historic ditch network rather than crossing ditch patterns.
Prior to runnel construction, the locations are probed again to re-confirm that the runnel will not intersect
a void. If a void is present, the runnel will not be constructed in that location and the corrective measures
described in Section 15 will be employed. Mass Audubon understands the potential for unintended
additional subsurface drainage should one be intersected. In the event this sho uld occur, mitigative
measures are described under the proposed Corrective Actions in Section 15 of the ENF, which includes
discontinuing the runnel construction, backfilling with the same material excavated and if necessary,
treating with hay similar to ditch remediation to raise the bottom elevation. Such events would also be
reported as part of the monitoring protocol described in Section 14 of the EENF.
g. Any mapped habitat by MNHESP including existing Saltmarsh Sparrow habitat as mapped or otherwise
provided by MNHESP.
Since the entire project site is within Estimated and Priority Habitat this has not been indicated separately
on the plans. However, NHESP has been provided copies of the EENF for comment. Mass Audubon
proposes to conduct further saltmarsh sparrow monitoring and work with NHESP to adjust time of year
restrictions in areas of the project site that do not support sparrow habitat and where sparrows have not
been observed.
h. Property boundaries - a separate plan sheet may be required for sites that include a number of smaller
lots.
The entire project area consists of portions of 2 lots, 2452 Main Street and 89 Shepherds Way, both
owned by Mass Audubon and identified as the BGM Wildlife Sanctuary. These are not field surveyed
property boundaries, but those taken from publicly available GIS.
i. Proposed temporary impacts associated with the restoration project (i.e., staging areas, pathways,
mowing sites, etc.).
The locations of proposed staging and access are indicated on the site plans and described in Section 16
above.
4. An Analysis demonstrating that the proposed project activities have been designed to incorporate all
feasible measures to avoid or minimize adverse impacts to wetland resource areas and the interests of the
Wetlands Protection Act to the maximum extent feasible.
See Section 12 of the EENF, Best Management Practices for typical measures to avoid and minimize
adverse impacts. Examples include conducting work only during neap tide cycles, complying with time-of-
year restrictions, use of temporary timber mats to support equipment, use of low ground pressure
equipment, minimizing re-fueling in the marsh, etc.
5. A Baseline Conditions Data Collection Plan:
At a minimum, site-specific baseline data should be collected over at least one or two monthly tidal
cycle(s). Other baseline metrics (e.g., target hydroperiods for vegetation, accretion rates, etc.) may cite
peer reviewed literature if applicable. Site-specific baseline condition data may be collected prior to filing
the NOI or as part of the proposed project work, however the need for the project must be justified.
Baseline data may include but is not limited to some or all of the following:
a. Descriptions of plant communities (such as species type and density) hydrology, groundwater
measurements, and soil characteristics.
Baseline vegetation mapping has been completed and is included with the ENF (See Appendices 2 and 3).
As described in Section 14 of the EENF, baseline monitoring was conducted by the Association to Preserve
Cape Cod (APCC) during 2023. This effort includes conducting pre-construction vegetation transects. EA
also provided vegetative community mapping based upon marsh elevation and USGS UVVR mapping for
the project site.
A total of 7 water level recorders were deployed within the marsh platform to establish baseline water
levels for a complete lunar cycle. Deployments will be made at runnel and ditch treatment areas selected
to evaluate changes following restoration.
Salt marsh accretion will also be measured using elevation surveys along 40-80 m transects and employing
feldspar marker horizons.
b. An evaluation of historic and existing conditions, including nearby less -disturbed areas or previously
restored areas as reference wetlands if available, as it relates to the extent and severity of the
impairment(s).
Historic aerial photography has been extensively reviewed in the pre-design phase of this project and
compared with current aerial images to identify marsh changes. Review of the literature on agricultural
practices was also conducted to reveal the extent of farming which occurred within the project site.
Numerous techniques were historically used to alter hydrology and salinity to benefit crops, especially hay
crops, such as ditches to drain areas of the marsh, embankments to surround ditches and isolate areas
from tidal flow, and sluice box valves to manage tidal flow. There are very few reference marshes within
or near the project site that were not part of these agricultural practices, but some were less disturbed,
partly due to their inaccessibility. The marsh subsidence that has been occurring is also gradually
revealing some of this historic agricultural infrastructure, including the gradual exposure of ditches that
had revegetated across their surface (ditch voids). The cessation of agricultural activities and
abandonment of the ditch and embankment network that has resulted in underdrainage and over
drainage of areas of the marsh, contributes to the inability of the marsh to accrete at a pace that can
maintain its elevation as sea level rises.
c. Existing extent of natural resource areas (i.e., salt marsh, open water, tidal creeks etc.) to the extent
that historic topographic maps, aerial photos, and other evidence are available and are necessary to
define project limits.
EA provided mapping of pannes and pools within the project site, as well as vegetative community
mapping based upon elevation, which included mudflats and unvegetated areas. Refer to Section 7.4
Existing Conditions above.
d. Existing anthropogenic impacts including mosquito ditches, agricultural embankments, agricultural
ditches, areas of fill, and flood control devices such as sluice gates and weirs.
These anthropogenic impacts occur at a scale that makes it difficult to map using aerial photography.
However, they have been mapped by GPS and factored into the overall project design. There are no
known remaining flood control devices within the project site. All existing visible ditches within the
project area have been located and are shown on the site plans. All embankments were also located and
are shown on Sheet C-101 of the site plans.
e. Evidence of subsidence, water pooling, over-saturation, or over-draining of the marsh platform, and/or
stressed vegetation to the extent that aerial imagery, previously collected data, and other evidence are
available.
Evidence of subsidence has been collected through comparison of historic and current aerial photography
as well as direct field observation and can be readily observed. Section 6 above describes the vegetative
and marsh platform changes that have occurred within the project site. According to USGS UVVR, the
project site contains 45 acres (55% of the site) that is above .1 UVVR indicating a marsh in decline.
e. Subterranean ditch void (see Appendix A) locations. Evidence suggests that runnel designs should
minimize the intersecting of these ditches to prevent their reanimation / drainage potentially
contributing to further marsh collapse. By ensuring that each runnel or channel segment falls within
an existing ditching pathway, the probability of inadvertently intersecting an open void is greatly
reduced.
See response to section 3f above.
f. Existing naturally formed pools and pannes in the proposed impact areas to the extent that aerial
imagery, previously collected data, and other evidence are available. Natural pools developed from
natural processes play an important role in aquatic habitat for plants, fish and waterbirds and shoul d
be preserved as part of restoration efforts.
Naturally formed pools tend to be smaller, deeper and contain more well-defined boundaries than
the shallower, amorphous pools formed through the subsidence process (S.C. Adamowicz and C.T.
Roman, 2005). These were mapped and avoided by the project design. See Section 7.4.
h. Existing tidal range for the site with estimated elevations provided for Mean Lower Low Water, Mean
High Water and Mean Higher High Water
Water level recorders were deployed during the fall of 2023 to establish baseline tidal range, as described
in Sections 7.1 and 14 of the EENF. Nearby NOAA tide gauges in Boston were used to establish MLLW,
MHW and MHHW.
i. Existing groundwater data and hydroperiods for representative areas of the salt marsh within the project
area including healthy marsh, oversaturated marsh, and undersaturated marsh. To avoid cost -prohibitive
data collection, hydroperiods can be developed for representative areas in the marsh and then applied to
remaining marsh areas if applicable. The data collected from these representative areas will be used to
characterize and understand the groundwater dynamics in other areas of the project. If this approach is
used, the categorization of representative areas should allow for project-wide demarcations of healthy
marsh, oversaturated marsh, and undersaturated marsh with representative locations supported by field-
derived hydroperiods and aerial photos.
Groundwater data was collected at 7 locations and these sites will continue to be monitored throughout
the post-restoration monitoring phase. See section 14 of the EENF.
j. Existing vegetation data including dominant plant communities (such as short -form and long-form S.
alterniflora, and S. patens) and the presence of Ruppia maritima in representative existing natural pools
and pannes within the project impact area. Transects or other established methods may be used.
Existing baseline vegetation data has been collected as described in Section 7 above. Natural pool/
pannes and pools with Ruppia are not targeted by this restoration and will remain unaffected. They tend
to be deeper and do not typically occur as part of a subsidence basin. See Appendix 2 for details.
k. Discussion of how impacts to Saltmarsh Sparrow habitat or other important species habitat may be limited
by conducting early consultation with NHESP, implementing Time of Year restrictions, and limiting removal
(mowing) within any one growing season.
NHESP typically requires a time of year restriction limiting work in the marsh during July and August for
the protection of breeding salt marsh sparrow. Mass Audubon may elect to obtain an approved habitat
management plan that includes monitors prior to and during construction in areas without sparrows
present so that limited work can occur during this time period if needed, as was recently approved for
The Trustees.
6. Project Objectives (desired post-construction conditions of the site) should outline an intended restoration
trajectory and progression from the Baseline Conditions for areas of the marsh with identified degradation
(e.g., undersaturation, oversaturation, etc.). Specific in dicators collected in the Baseline Conditions Data
Collection Plan will be the same indicators with restoration target values. The Project Objectives also serve
to interpret the Post-Construction Monitoring results in which progress is measured. Any deviations from
the intended successional trajectory should be captured in the Corrective Action Plan in order to redirect
the project trajectory back towards the Project Objectives. For example, a Project Objective may be to
decrease the hydroperiod at the root zone by reducing water levels at mean low tide by 10 cm; which
would be compared against the Baseline Conditions Data Collection Plan that includes groundwater
monitoring collected over at least one or two monthly tidal cycle(s); or to drain pools that ar e causing
marsh dieback and subsidence, which would be measured by documenting pre - and post-project size of the
pool, and progress on regrowth of vegetation in the drained area.
A detailed Success Criteria Table (Table 15.1) of the EENF outlines specific objectives and successional
trajectory for each restoration method and includes the Corrective Action Plan is included describing
measures to take should the project not meet objectives.
7. A Construction and Post-Construction Period Monitoring Plan that includes:
a. A Wetland scientist(s) who will serve as the project’s Environmental Monitor(s) (EM). This person or
persons should have a minimum of 5 years of experience and be competent in coastal wetland
ecology, and salt marsh species and their habitats (rare species consultation with MNHESP may be
required). Experience with salt marsh restoration is desirable.
Either in-house staff or contracted consultant will serve as the EM and credentials for the EM will be
submitted for approval prior to commencement of work.
b. A construction schedule and EM’s oversight schedule along with relevant phasing details, if
appropriate. The construction schedule should reflect Saltmarsh Sparrow presence from mid -May
through September and their active nesting period between late May an d early August so activities
should be restricted during this timeframe, and an acknowledgement should be included stating that
no existing or previous nesting areas will be impacted (i.e., no transference of existing well -developed
thick thatch layer to new areas). For projects installing habitat mounds, an overall project goal should
be a net increase in overall suitable nesting area within 1 year of treatment.
A proposed Construction Schedule is included in Section 16 of the EENF. The timeline may need to
be adjusted based upon completion of permitting and final project phasing. Section 14 of the ENF
describes Construction Period Monitoring and Post Construction period monitoring. Time-of-year
restrictions established by NHESP will be followed.
c. All responsible roles/parties should be listed in the Plan with assurances that all equipment operators
and site contractors will be trained in site methodologies and competent to perform the work. Specific
names and contact information should be provided to the Issuing Authority prior to construction.
A partial list of parties involved in design and implementation is included in Section 17 of the ENF. A final
list of parties will be provided to permitting authorities prior to commencement of work.
d. A description of how visual and photographic inspections will occur and be documented to determine
if changes have occurred that require corrective action such as clogging of ditches or over draining.
Construction and post-construction monitoring and reporting is described in Section 14 of the EENF,
including details and scheduling of reporting by the EM. Bi-weekly reports are proposed to be
submitted by the EM until stabilization of the site to the satisfaction of the permitting agencies.
Following the completion of construction period monitoring, Mass Audubon and APCC will conduct
post construction follow-up monitoring.
Corrective action measures are described in Section 15 of the EENF and include both Category 1
actions, which include responses to unintentional construction impacts or changes in design above
the established thresholds in the Success Criteria Table. These actions require additional review and
consultation by the reviewing agencies. Photographs of site conditions and recommendations for
corrective actions will be provided.
Category 2 corrective actions include anticipated maintenance, such as unclogging of runnels, adding
hay beyond plans provided in permit applications or maintenance of marsh island mounds to adjust
heights or remove invasive species. These activities will be reported to agencies as part of the usual
monitoring reports but are suggested not to require further regulatory review. Examples include
management of invasive species, management of runnels such as removing clogs and adding hay to
treatment ditches.
e. A plan for assessing project performance using objectives (e.g., post -construction conditions of the site
compared with baseline and objectives) which, at a minimum, includes annual submittals for the first
three years. Collected datasets should be used to show Project Objectives are being met or identifying
deviations from the Project Objectives. Communication with the issuing authority should be
established following the first three years to determine compliance with Project Objectives and/or to
assess corrective actions needed. In accordance with 310 CMR 10.05(6)(d), the issuing authority may
issue an Order for up to five years where special circumstances such as monitoring salt marsh
restoration projects are set forth in the Order of Conditions.
Again, refer to Table 15.1 Success Criteria Table in Section 15. We note that the year of
implementation is considered year 0 in terms of monitoring.
8. A Corrective Action Plan that includes:
a. Measures to reestablish healthy marsh condition following unintended outcomes such as clogging of
runnels resulting in ponding, inadequate hay in ditch remediation areas, deterioration of or lack of
appropriate vegetation on marsh mounds, observation of po nded water in unexpected locations,
temporary impacts persisting, etc.
See Table 15.1, Success Criteria Table.
b. A schedule with thresholds at which monitored metrics trigger corrective activities upon detection .
See Table 5, Success Criteria Table.
c. Activities should be categorized into inadvertent adverse impacts (typically unforeseen or not a
natural outcome of dynamic marsh process) or maintenance (resulting from natural dynamic
processes) so that the Issuing Authority can better review which activities should be considered for
further review or approved with minimal review. Additional information on the Corrective Action Plan
is in the following section.
Section 15 of the EENF contains the Corrective Action Plan and identifies how corrective actions are classified, with
Category 1 actions including unintentional construction impacts or changes in the design above the thresholds
established in the Success Criteria Table (Updated Table 5). These measures require further agency review.
Category 2 includes actions such as anticipated maintenance, installation of small runnels with a tideshed less than
0.8 acres, minor extension of runnels to adjust for site specific conditions between design and implementation,
adding additional hay to treatment ditches, maintenance of marsh habitat mounds to adjust heights or remove
invasive species. These actions do not require further agency review but will be included in regular monitoring
reports. Table 15.1 of the EENF identifies Category 1 and Category 2 corrective actions. Any activity not
specifically listed would require prior consultation with regulatory authorities
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Newburyport, MA. https://ecos.fws.gov/ServCat/Reference/Profile/154076 .
Tonjes D.J. 2013. Impacts from ditching salt marshes in the mid-Atlantic and northeastern United
States.Environmental Review 21:116-126. https://doi.org/10.1139/er-2013-0003.
Walsh J, Kovach A.I., Babbitt K.J., O'Brien K.M. 2012. Fine-scale population structure and asymmetrical dispersal
in anobligate salt-marsh passerine, the Saltmarsh Sparrow (Ammodramus caudacutus). The Auk 129:247-258.
DOI: 10.1525/auk.2012.11153.
Wright S.C. 2012. Understanding the mechanisms behind surface elevation loss in ditched marshes. OpenBU.
https://hdl.handle.net/2144/12682.
Wilson, C.A., Huthes, Z. J., FitzGerald, D.M., Hopkinson, C.S., Valentine, V., Kolker, A.S. 2014. Saltmarsh pool and
tidalcreek morphodynamics: dynamic equilibrium of northern latitude saltmarshes. Geomorphology 213, 99-115.
https://doi.org/10.1016/j.geomorph.2014.01.002.
USFWS. 2017. Addressing Impaired Hydrology for Salt Marsh Resiliency Workshop Notes. U.S. Fish and
WildlifeService. Hadley, MA. https://ecos.fws.gov/ServCat/Reference/Profile/143359.
USFWS. 2019. Recovery outline for the Rufa Red Knot (Calidris canutus rufa). U.S. Fish and Wildlife Service.
Hadley,MA.
https://ecos.fws.gov/docs/recovery_plan/20190409%20Red%20Knot%20Recovery%20Outline%20final%2signe
d.pdf.
Zaltzberg-Drezdahl K, Gutwein S.B., Lawlor G, Krok-Horton L, Lindsay R, Newman J, Johnson I, Toensmeier E,
Roszell C,Dagoberto M. 2023. The Massachusetts Healthy Soils Action Plan. Executive Office of Energy
andEnvironmental Affairs. https://www.mass.gov/doc/healthy-soils-action-plan-2023/download.
Appendix 1 Oxidation Subsidence and Water-logged Subsidence
Trajectories
Appendix 2 APCC Monitoring Report
Appendix 3 EA Technical Memorandum
Appendix 4 SMARTeam Restoration Design Steps
Appendix 1: Oxidation Subsidence and Waterlogged
Subsidence Trajectories
Oxidation Subsidence Trajectory
In addition to fighting SLR salt marshes must also respond to direct subsidence of the marsh substrate
due to exposure of the peat from the numerous man-made ditches within the marsh.
Salt marsh soils are a mixture of organic matter and mineral sediments, referred to as salt marsh peat.
The organic content in salt marsh soils is mostly supplied by the marsh’s perennial grasses. At the end of
each growing season, the senescent above ground biomass mat together to form a thatch layer or
detach and drift to a new location in the marsh as wrack. Season by season, layers of mineral sediments
and organic matter build-up in a process called salt marsh accretion. Belowground, roots and rhizomes
of the marsh plants constitute over 80 percent of the peat.
When peat soil is saturated, the voids between the soil particles are filled with water resulting in low
oxygen conditions that limit the amount of organic matter that can be decomposed by soil microbes.
Lignin, the portions of the organic matter that are more resistant to decomposition then build-up in the
soil layer. When salt marsh elevation rises above tidal flooding and sediment voids no longer fill with
water, aerobic decomposition can begin, which allows soil microbes to break down the organic matter.
Under these conditions, air filled voids in the upper soil horizon supply the microbes with enough
oxygen to consume all the organic matter in the soils. The process of soil saturation leading to
anaerobic respiration of soil microbes, organic matter accumulation, rise of surface elevation, soil
surface drying and then aerobic respiration leading to increased decomposition and elevation loss
creates a balance with the surface of the marsh and sea level.
Farmer’s ditches upset this balance by draining the water out of the pore spaces deep in the soil column.
When the water drains from the soil, void spaces then are filled with oxygen which allows the soil
microbes to switch to aerobic respiration and begin decomposition of the organic matter in parts of the
soil column that were previously sustained in the saturated condition. When decomposition occurs at a
rate greater than can be supported by new vegetative growth, subsidence of the marsh surface occurs
through a process described herein as the Oxidation Subsidence Trajectory (OST).
Due to the extensive ditching which has occurred in eastern marshes, the impacts from OST can be
significant. Figure 1 below provides Lidar data of a densely ditched area of marsh at the Parker River
National Wildlife Refuge depicting changes in marsh elevation adjacent to ditches. LeMay (2007) found
that ditched marshes had consistently lower elevations than unditched marshes and that increasing
ditch density was correlated with decreasing elevation. Burdick et al. (2019) found a measurable
increase in subsidence with greater effects near the ditches at a study site in Rowley, MA. Burdick
conservatively estimated an average of 9 cm of subsidence midway between ditches that averaged 14 m
apart over the last 80-year period. Addressing the subsidence which occurs from oxidation of peat
along ditches is the primary focus of the ditch remediation restoration measures.
FIGURE 1: LIDAR MAP OF DITCHED MARSH AT PARKER RIVER WILDLIFE REFUGE SHOWING AREAS OF SUBSIDENCE IN THE
VICINITY OF DITCHES (IMAGE COURTESY OF SAM WRIGHT BOSTON UNIVERSITY)
Wright S.C. 2012. Understanding the mechanisms behind surface elevation loss in ditched marshes. OpenBU.
HTTPS://HDL.HANDLE.NET/2144/12682
Waterlogged Subsidence Trajectory
The term Waterlogged Subsidence Trajectory (WST) describes the cycle of coastal
processes involved in the creation of subsidence basins and mega-pools as a result of
anthropogenic alterations of the salt marsh due primarily to historic farming practices. The
term and its stages have been developed by the Salt Marsh Adaptation and Resiliency
Team (SMARTeam), a collection of regional private, federal, state and local government
scientists, land owners, land managers, planners and contractors dedicated to salt marsh
restoration.1 The various stages of WST described below have been well-recognized and
observed by scientists and salt marsh managers. However, the identification of a specific
sequence of stages has not previously been described. The identification and description
of these stages has become necessary to communicate the design development and
restoration goals for projects such as this which specifically target the long-term impacts
associated with broadscale changes to tidal hydrology resulting from historic agricultural
use and alteration of salt marshes.
While there are other causes for subsidence of marsh peat, including OST described
above, WST describes the subsidence occuring as a result of the entrapment of water
behind the low embankments and other relic historic structures which form individual
tidesheds, preventing full tidal exchange, especially draining of tidal flow. This
accumulation of water behind the embankment structure causes changes to soil
chemistry and soil structure which results in loss of vertical marsh elevation (subsidence).
The combined subsidence and inundated conditions result in first a shift towards plant
species tolerant of the new conditions, then a gradual loss of vegetation as conditions
become unsuitable for all marsh plants. The progression of this over-saturation also
results in a rise in the local groundwater table and ultimately the development of a series
of unvegetated pools. If unchecked, the processes continue to accelerate to the widening
and deepening of the pools until they intersect and create large mega-pools. The mega-
pools will persist until sufficient hydraulic head is created to allow a breach to incise a low
point in the basin, allowing the pool to begin to drain and the process of revegetation to
begin. The breach will gradually expand to accommodate the new tidal flow of the basin.
Often, the breach is created in the location of an historic tidal channel which had been
filled or altered for farming purposes.
Ten stages of WST have been identified and are described below with examples of areas of
the Great Marsh currently within each stage.
1 The SMARTeam consists of project partners including the US Fish and Wildlife Service, UNH Jackson
Estuarine Laboratory, Northeast Wetland Restoration, Mass. Division of Ecological Restoration,
MassBays Program, The Trustees, Mass Wildlife, Bear Creek Wildlife Sanctuary and other New England
partners. The team was established to develop management strategies to address the most common
sources of salt marsh subsidence and to improve the most vital habitats for tidal marsh dependent
species identified as At-Risk by the US Fish and Wildlife Service.
WST1: Early Decline
South of Kent’s Island, Newbury Ma
42*45’36.50”N 70*52’31.50”W
Google Earth image date May 4th, 2018
The Early Decline in the WST occurs due to an alteration of normal tidal exchange, typically
from an embankment or clogged ditch, which leads to water retention behind or
upgradient of the blockage. The saturation eventually raises the surrounding ground water
table. When ground water reaches the surface and plant roots are saturated for long
periods of time, typical high marsh species cannot tolerate the change in hydroperiod.
Species such as spartina patens are replaced by spartina alterniflora which can tolerate
wetter growing conditions (replacement by short-form spartina alterniflora is common due
to saturated growing conditions that “stunt” plant growth as this species prefers daily tidal
flooding and draining and not extended saturation). As the saturation continues even the
spartina alterniflora is unable to survive resulting in an overall decrease in plant density
and vegetative cover and an increase in unvegetated areas.
According to the aerial image record, it is estimated the subsidence areas depicted above
entered into the early decline stage in approximately 2003.
WST2: Late Decline
South of Kent’s Island, Newbury Ma
42*45’37.00”N 70*52’22.00”W
Google Earth image date May 4th, 2018
The Late Decline stage of the WST is defined by broad scale loss of vegetative cover with an
increase in the development of unvegetated panne and pool habitats. This process can
occur rapidly as root mass is lost due to plants dying causing peat to collapse resulting in
significant elevation loss locally of as much as 8 inches or more. Depending on the nature
of the historic agricultural structures present, some areas of marsh can become stalled in
this stage, such as areas with large or particularly solid embankment structures.
According to the aerial image record, the area depicted above entered into the late decline
stage in approximately 2005.
WST3: Early Mega-pool Cycle
South of Kent’s Island, Newbury Ma
42*45’33.00”N 70*52’08.00”W
Google Earth image date May 4th, 2018
The Early Mega-pool Cycle of WST is defined by a near total loss of vegetative cover with an
increase of amorphous and patterned pool signatures. The forming subsidence basin
remains irregular with the varied age of individual panne and pool forming the mega-pool
basin. According to the aerial image record, the area depicted above entered into the early
Mega-pool Cycle stage in approximately 2001.
WST4: Late Mega-pool Stage
South of Kent’s Island, Newbury Ma
42*45’24.00”N 70*52’24.00”W
Google Earth image date May 4th, 2018
The Late Mega-pool stage of WST is defined by a total loss of vegetative cover with near
total loss of amorphous and patterned pool signatures as the subsidence basin becomes
nearly uniform. According to the aerial image record, the area depicted above entered into
the late Mega-pool Cycle stage in approximately 1978.
WST5: Early Mega-pool Breach Stage
East of the Parker River Railroad Bridge
42*45’33.00”N 70*51’33.00”W
Google Earth image date May 4th, 2018
The Early Mega-pool Breach stage of the WST is defined by a new and partial creek incision
through the confining berm. The subsidence basin shows signatures of tidal exchange and
vegetation begins to recolonize areas of the subsidence basin. According to the aerial
image record, the area depicted above entered into the early Mega-pool Breach stage
between 1995- 2001.
WST6: Middle Mega-pool Breach Cycle of the WST
Parker River National Wildlife Refuge, Newbury Ma
42*45’60.00”N 70*51’33.00”W
Google Earth image date May 4th, 2018
The Middle Mega-pool Breach stage of the WST is defined by a nearly complete creek
incision and draining of the mega-pool subsidence basin. The subsidence basin shows
evident signatures of tidal exchange and abundant vegetation recolonization. According to
the aerial image record, the area depicted above entered into the middle Mega-pool
Breach stage in approximately 2010.
WST7 Late Mega-pool Breach Stage of the WST
Parker River National Wildlife Refuge, Newbury Ma
42*45’46.00”N 70*49’36.00”W
Google Earth image date May 4th, 2018
The Late Mega-pool Breach stage of the WST is defined by a complete creek incision and
near draining of the mega-pool subsidence basin. The subsidence basin shows nearly
complete vegetation recolonization with increasing plant community diversification.
According to the aerial image record, the area depicted above entered into the late Mega-
pool Breach stage in approximately 2014.
WST8: Early Single Channel Recovery Stage
Former J.H. Sanborn Marsh, Hampton NH
42*55’15.00”N 70*51’00.00”W
Google Earth image date May 4th, 2018
The Early Single Channel Recovery stage of the WST is defined by a complete creek incision
and establishment of a tidal channel hierarchy. Most evidence of anthropomorphic
structures within the mega-pool subsidence basin are strongly naturalized. The
subsidence basin shows nearly complete vegetation recolonization with increasing plant
community diversification throughout the subsidence basin. According to the aerial image
record, the area depicted above entered into the early single channel recovery stage in
approximately 2010.
WST9: Middle Single Channel Recovery Stage
Former Dodge Marsh, Hampton NH
42*54’52.00”N 70*51’06.00”W
Google Earth image date May 4th, 2018
The Middle Single Channel Recovery stage of the WST is defined by a complete
establishment of a tidal channel hierarchy. Most evidence of anthropomorphic structures
within the mega-pool subsidence basin are strongly naturalized. The subsidence basin
shows complete vegetation recolonization with abundant plant community diversification
throughout the subsidence basin. According to the aerial image record, the area depicted
above entered into Middle Single Channel Recovery in approximately 2003.
Appendix 2: APCC Monitoring Report
Barnstable Great Marsh
2024 Pre-Restoration Salt Marsh Monitoring
FINAL REPORT
Report prepared by:
Jordan Mora, Eliza Fitzgerald, and Molly Autery, Association to Preserve Cape Cod
under contract with Mass Audubon
Work funded by the Department of Fish and Game In-Lieu Fee Program
INTRODUCTION:
The Barnstable Great Marsh encompasses roughly 1,100 acres of salt marsh located on the
northern shore of Cape Cod near Barnstable Harbor. Due to its size and valuable habitat, the site
is designated as an area of critical environmental concern (ACEC) by the U.S. Department of the
Interior Bureau of Land Management and has been identified as a priority marsh by the U.S. Fish
and Wildlife Service (USFWS) Atlantic Coast Joint Venture and the USFWS Massachusetts Salt
Marsh Restoration Priorities. The salt marsh supports threatened species (including the Salt Marsh
Sparrow and Diamondback Terrapin) as well as many other environmental and cultural resources
significant to the history and economy of Cape Cod. In addition to the fish and wildlife benefits,
the Town of Barnstable has recognized the importance of the salt marsh in protecting homes and
businesses by buffering impacts from storms and sea level rise in their Municipal Vulnerability
Preparedness (MVP) plan.
Although there is consensus across local, regional, and national government entities that the
Barnstable Great Marsh contains salt marsh habitat that’s crucial to maintaining native fish and
wildlife populations and a sustainable coastal economy, managers and scientists also recognize
that New England salt marshes are not effectively keeping up with accelerated rates of sea level
rise due to subsidence trajectories caused by human land use practices (Adamowicz et al. 2020).
Embankments and ditching in the marsh are two of several practices that have manipulated the
hydrology of the marsh, changing the soil chemistry and microbial processes which allow it to
adjust to rising sea levels.
To protect this high-priority salt marsh from sea level rise impacts, Mass Audubon has partnered
with the USFWS Salt Marsh Adaptation and Resiliency Teams (SMARTeams) to develop and
implement a restoration plan to improve the salt marsh’s resilience using two innovative restoration
strategies. First, runneling is the creation of small grooves in the marsh (generally ≤ 30 cm wide
and deep) to drain standing water on the marsh surface (Perry et al. 2021). They are normally
constructed through hand-digging and/or low ground pressure excavators. Studies show that by
implementing runnels, the vegetation recovers in previously waterlogged areas within 3-5 years
(Perry et al. 2021, Watson et al. 2022). Second, ditch remediation is a method of removing ditches
using natural salt marsh processes to restore groundwater table depths and reduce decomposition
(Burdick et al. 2020). Practitioners mow salt marsh perennial grasses from one or both sides of the
treatment ditch at the end of the growing season and place a 15–20 cm “hay” layer in the ditch.
The native grasses act as a filter, trapping particulates which accumulate over time, and research
shows that plants will revegetate these areas within 3 years (Burdick et al. 2020).
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 2
By creating runnels and encouraging ditch removal through remediation, the salt marsh’s natural
accretion mechanisms are rejuvenated, and the subsidence trajectories are reversed. Above- and
belowground primary production increases and decomposition slows resulting in greater
accumulation of organic matter, and thus elevation gain, on the marsh surface. As sea level rises,
the healthy plants continue to filter and trap particulates from the flood tide and the rate of
sedimentation also increases. The combined effect of these environmental forces and restored
processes should result in a robust marsh system that will be more resilient to future climate change
impacts.
METHODS:
Phase 1 of the Restoration Plan
involves roughly 80 acres of
Mass Audubon’s property in the
Barnstable Great Marsh. The
Association to Preserve Cape
Cod (APCC) was contracted by
Mass Audubon to provide pre-
restoration monitoring of ditch
remediation and runneling in
2023. The monitoring design
consists of hydrologic,
vegetation, elevation, and
accretion measurements of both
treatments (ditch remediation and
runneling) in the proposed Phase
1 restoration area, or “action”
area, and a reference area located
directly to the west and owned by
the Town of Barnstable, referred
to as the “control” area (Figure 1).
The monitoring plan was
developed based on key metrics
and criteria requested by
regulatory agencies, including the
Figure 1: Map of the “action” and “control” sections of the Barnstable Great
Marsh. Tideshed layers were downloaded from United States Geological
Survey (Ackerman et al. 2021). Restoration plan provided by Geoff Wilson,
member of SMARTeams.
Department of Environmental Protection and the MA Office of Coastal Zone Management (CZM),
as well as monitoring techniques employed at previous SMARTeams restoration sites, such as Old
Town Hill Marsh in Newbury, MA.
Hydrology: Hydrologic monitoring of water levels in the Barnstable Great Marsh was conducted
in late fall of 2023. The goal of this monitoring was to establish baseline surface water and
groundwater levels for an entire lunar cycle (30 days). In the restoration area, water level
monitoring stations were selected based on proximity to proposed ditch remediation and runneling
locations with no other proposed restoration treatments within roughly 100 ft and a ditch that
drained in only one direction. The stations in the control area of the marsh were chosen to be
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 3
A B C
similar to the restoration sites in elevation, ditch size, and proximity to both the upland edge and
main channels.
Seven water level loggers (Solinst Levelogger 5, Model 3001) were deployed in PVC housings for
one lunar cycle (October 25, 2023 to December 1, 2023): two measuring groundwater elevation
and one measuring surface water elevation in the control area, and two measuring groundwater
elevation and two measuring surface water elevation in the restoration area. Because of the
proximity of the transects in the control area, only one surface water station was deemed necessary
to record full tidal fluctuations and flooding in the ditch and on the marsh platform. The surface
water stations were affixed to metal stakes that were driven ~2 ft deep into the sediment bed (Figure
2C). The groundwater wells (or piezometers) were designed to prevent clogging and encourage
drainage. They were screened by drilling 1/8- and 1/4-inch holes roughly 1/2 - to 1-inch apart
throughout the lower 60cm of the 1-meter PVC (Figure 2A). The holes were covered with garden
mesh fabric, and they were installed roughly 60cm deep and 1 meter from the edge of the ditch
and within 5 m of a transect (Figure 2B).
Figure 2: Photos of the groundwater well (or piezometer) design (A – mesh fabric not
shown), placement of control-ditch groundwater well (B), and installation of surface water
logger in ditch during ebb tide (C).
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 4
A barometric pressure logger (Solinst Barologger, Model 3001) was deployed during the same
period as the water level loggers (from October 25, 2023 to December 1, 2023) in a tree at the
upland edge of the action marsh, placed roughly 1.5 meters above the marsh to minimize the
chance of flooding damage. Barometric pressure data was used to convert absolute pressure
collected by the water level loggers to water depth that’s corrected for atmospheric pressure. The
elevation of the groundwater wells and creek stakes was surveyed using a Trimble Geo7x and
antenna attachment with centimeter accuracy (NAVD88 ± 3cm). Further adjustment to improve
relative accuracy was necessary using the high-water maximum from the respective surface water
logger dataset.
Vegetation: Vegetation growth in salt marshes can be used as an indicator of marsh integrity
because each salt marsh plant species has evolved to tolerate specific flooding regimes and salinity
concentrations across the elevation gradient. In other words, the composition and distribution of
different plant species provides information regarding the flooding patterns and salinity in that area
of the marsh. To establish baseline vegetation characteristics in the control and action areas of the
Barnstable Great Marsh, vegetation transects were set up and monitored during the summer of
2023. Transects were oriented perpendicular to the proposed restoration treatment (i.e., across
ditches and proposed runnels). Placement of transect replicates (6 per treatment type, ditch
remediation and runnels, in the action and control marsh: 24 transects total) were determined with
input from SMARTeam members, Mass Audubon staff, and other project partners (Figures 3 and
4).
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 5
Figure 3: Map of the Action marsh where the Phase 1 restoration plan will be implemented.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 6
Figure 4: Map of the Control marsh meant to act as a no-action reference for comparing restoration effects in the Phase
1 restoration, or Action, area.
Control transects were located where the drainage conditions (i.e., vegetation), channels widths
and spacing, and elevation gradient were comparable to those within the restoration area. The two
ends of each transect were permanently marked using 2-in. x 2-in. x 42-in. wooden stakes
(pressure-treated balusters). Each transect was 20 m long, with the center point at 10 m. The center
plot was either over the middle of the ditch or over the approximate runneling location. One end
of the transect was designated as “0 m” and flagged to orient individuals, see Figure 5. The
“walking side” and “plot side” of each transect was determined when the transects were initially
established to avoid disturbance of monitored plots. The transects were labeled for their
intervention type and replicate number. For example, D-A-5 is “Ditch Action – Replicate 5” and
R-C-2 is “Runnel Control – Replicate 2”.
After the transects were staked, labeled, flagged, and their locations mapped in June and July 2023,
teams of APCC staff, Mass Audubon staff, and volunteers assembled to characterize vegetation
cover types at nine (9) half-meter-square (0.5 m2) plots along each transect (placed at 0m, 5m, 8m,
9.5m, 10m, 10.5m, 12m, 15m, and 20m) in August 2023 (total = 216 plots). From the perspective
of the walking side of the transect, plots located at 0-9.5 m were aligned with respect to the bottom
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 7
right corner, the plot at 10 m was aligned at the center, and plots at 10.5-20 were aligned with
respect to the bottom left corner (Figure 5). Each team recorded percent cover by species (including
other cover types such as bare sediment, dead, standing water, wrack, and macroalgae) and the
height of the five tallest stems of Spartina alterniflora in each plot. Percent covers were determined
at each plot to the nearest 1% (0.5% in cases of trace covers) in teams of two people. Square cut-
outs representing 1, 5, and 10% were used as visual aids. Photos were taken of each individual
vegetation plot and of the entire transect from the 0 m stake and perpendicular to the transect
(Figure 5).
Figure 5: Diagram of the transect layout indicating the spacing and placement of vegetation plots and marker horizons.
Footprints show which side of the transect was intended for walking such that the plots were not trampled during
monitoring efforts. Cameras and blue cones indicate photo perspectives.
Elevation: Cross-section elevation measurements were collected along all transects in the action
and control areas. High accuracy (<1mm) relative elevation measurements were collected with a
Leica digital level and tied to the North American Vertical Datum (NAVD88) using reference
benchmarks surveyed with a Trimble Geo7x and Zephyr 2 antenna (± 3cm). The GPS coordinates
(x,y) of each plot and marker horizon were also collected with the Trimble Geo7x device. Elevation
measurements were collected along each transect at 0, 5, 8, 8.5, 9.5, 10, 10.5, 11.5, 12, 15, and 20
meters to correspond with the placing of vegetation plots and marker horizons. For transects that
crossed ditches, measurements were also collected at additional locations where there were
significant slope or elevation changes (see Appendix A for all elevation cross-sections). The goals
of precise elevation measurements were to establish a baseline of each plot’s vertical position
which will be used to track changes expected over time and assess the effect of the respective
restoration treatment.
APCC also collected horizontal measurements (width and length) of depressions, defined as
pooled areas where there was significant standing water during low tide, which were within 10m
of the transect. Elevation and GPS measurements of the ditches provided dimensions of each
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 8
control and action ditch replicate. These baseline data will be used to measure change in these
feature dimensions over time.
Accretion: Marker horizons, used to measure sediment accretion over time, were placed at four
randomly selected ditch remediation and runnel transects in the action and control areas (32 total;
Figures 3 and 4) in June and July 2023. See Table 1 for a list of the transects where the marker
horizons were installed.
Table 1: List of the transects where the marker horizons were installed in July 2023 at the Barnstable Great Marsh.
Refer to Figures 3 and 4 for a map of the labelled transects. Treatment Type Action Control
Ditch Remediation D-A-1, D-A-2, D-A-3, D-A-5 D-C-2, D-C-3, D-C-4, D-C-5
Runnel R-A-1, R-A-2, R-A-4, R-A-6 R-C-1, R-C-2, R-C-3, R-C-5
These marker horizons were installed by evenly spreading 1L of feldspar powder, a very fine-
grained white substrate, inside a 0.25 m2 plot on opposite sides of the transect center (1.35 m from
the center). To avoid future disturbance, the marker horizons were established in line with the
vegetation plots (Figure 5). Two wooden stakes at opposite diagonal corners permanently mark the
marker horizon locations. To measure marsh accretion, sediment cores can be sampled at the
location of the marker horizon, and the contrast of the white feldspar against the dark, organic-rich
peat provides a reference to measure the accumulated organic matter and sediments using calipers.
Due to limitations on seasonal timing, expense, and availability, APCC did not measure accretion
at the marker horizons at the end of the growing season in 2023.
In 2024, APCC returned to the marker horizon plots on July 25th (action plots) and August 8th
(control plots). The 0.25 m2 quadrat was positioned between the two wooden stakes placed at
diagonal corners at each plot. Teams of two estimated percent cover by plant species and other
cover types (i.e., bare sediment, dead plants, and wrack) and measured the heights of the three
tallest Spartina alterniflora stems within the quadrat. To measure sediment accretion, a small (~2-
inches in width and 3-4-inches in length), conical sediment core was cut with a serrated knife and
extracted with a trowel from the right corner of the plot closest to the transect, unless a notable
disturbance was present, like a crab burrow. The core was placed on a hard surface and split down
the middle using a sharp, non-serrated knife. The marker horizon was identified by the appearance
of a line of feldspar. Accretion was measured using traceable digital calipers to record the distance
between the upper limit of the feldspar line and the surface of the sediment. Three measurements
were collected from each core and later averaged to calculate a single accretion rate (mm/year) per
plot. The three measurements were collected where there were clean (undisturbed) edges of
feldspar and sediment.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 9
RESULTS:
Hydrology: The seven continuous water level loggers deployed at the Barnstable Great Marsh
from October 25, 2023, to December 1, 2023, collected data throughout a full lunar cycle (30 days)
capturing the range of two complete sets of spring and neap tides. However, the second set of neap
tides, starting on or around the 19th of November, was higher than predicted due to a low-pressure
system and strong northwestern winds which forced the tides higher and skewed the average water
levels for that week. Additionally, nighttime temperatures dropped to below freezing on November
12th and it appears that some of the groundwater wells may have shifted slightly due to very cold
weather (~1-2 centimeters). For these reasons, APCC chose to calculate and compare the average
depth to groundwater table from the first two weeks of deployment (spring tides: October 26
through November 2; neap tides: November 4 through November 11) (Table 2).
Table 2: Average depth to groundwater (in meters) calculated as the marsh
surface elevation minus the seven-day average of daily minimum
groundwater level.
Treatment Action Control
Neap Spring Neap Spring
Ditch 0.19 0.07 0.26 0.08
Runnel 0.08 0.02 0.12 0.02
The control – ditch remediation water level loggers (surface water and groundwater) were
deployed at transect D-C-4 and the action – ditch remediation water level loggers were deployed
at transect D-A-6 (Figure 6). The ditch at D-A-6 is shallower than the ditch in the control section,
but both ditches drain completely at low tide (minimum level not shown for surface water).
Additionally, the marsh surface elevation is higher at the logger station in the control section by 5
cm. Groundwater levels behaved similarly during the ebb tide in the control and action areas with
lower groundwater levels during neap tides, especially when the tides did not flood the marsh
surface. During the ebb tides in the third and fourth weeks of the deployment, there was more
drainage in the control groundwater well than in the action groundwater well. This may be due to
a combination of factors including the difference in hydraulic pressure from the marsh surface
elevation, the lower peak in the nighttime tide, and the deeper control ditch.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 10
Figure 6: Continuous water level data (6-min interval) collected near one control (a) and one action (b) ditch
remediation site at Barnstable Great Marsh in 2023. Groundwater wells, or piezometers, were placed 1m from the
ditch edge. Surface water loggers were placed downgradient in the corresponding ditch. Brackets indicate spring and
neap tides throughout deployment period.
The control-runnel groundwater logger was deployed at transect R-C-5 and the action-runnel
groundwater logger was deployed at transect R-A-5 (Figure 7). The surface water loggers were
placed in the nearest ditch. Contrary to the ditch treatments, the marsh surface at the control logger
was lower in elevation than the marsh surface at the action logger with a difference of roughly 11
cm. The two ditches were similar in depth; the bottom of the action ditch was about 10cm lower
in elevation (not shown). Even with the difference in marsh elevation, the groundwater levels
behaved similarly between the control and action areas of marsh with almost no drainage during
spring ebb tides (2 cm) and only reaching about 7 or 8 cm in depth during neap ebb tides.
a) Spring Neap Spring Neap
2.2 Control
2.0
1.8
1.6
1.4
1.2
1.0
0.8
10/25 10/30 11/4 11/9 11/14 11/19 11/24 11/29
b) 2.2
2.0
Marsh Surface
Groundwater Level
Surface Water Level
Action
1.8
1.6
1.4
1.2
1.0
0.8
10/25 10/30 11/4 11/9 11/14 11/19 11/24 11/29 Water Level/Elevation (NAVD88 in m) Water Level/Elevation (NAVD88 in m)
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 11
Figure 7: Continuous water level data (6-min interval) collected near one control (a) and one action (b) runnel site at
Barnstable Great Marsh in 2023. Groundwater “wells,” or piezometers, were placed 1m from the center line of the
proposed runnel. Surface water loggers were placed downgradient in the nearest ditch. Brackets indicate spring and
neap tides throughout deployment period.
It is clear that the groundwater table is much lower during all ebb tides around the ditches
compared to the proposed runnel areas (Figure 6 and 7). Based on preliminary calculations
completed in Microsoft Excel of the total time points flooded divided by the total time points
recorded, the runnel groundwater sites (control and action) show greater percent time flooded than
the ditched groundwater sites throughout the root zone depth (~30cm belowground; Figure 8;
Lynch, personal communications). The difference is especially prominent at the 10 and 15 cm
depths where the time flooded is roughly 20% greater at the runnel locations. At the runnel and
ditch logger sites, the soil is flooded 100% of the time at the 25 cm soil depth, meaning even at the
lowest point in the tide, this depth is fully saturated at all monitored locations.
a) Spring Neap Spring Neap Control 2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
10/25 10/30 11/4 11/9 11/14 11/19 11/24 11/29
b)
2.2 Marsh Surface
Groundwater Level
Action
2.0
1.8
1.6
1.4
1.2
1.0
0.8
10/25 10/30 11/4 11/9 11/14 11/19 11/24 11/29 Water Level/Elevation (NAVD88 in m) Water Level/Elevation (NAVD88 in m)
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 12
Figure 8: Line graph showing the relationship between percent time flooded and marsh soil depth at the ditch and
runnel groundwater wells installed in the action and control marsh sections at the Barnstable Great Marsh (D-A: Ditch-
Action; D-C: Ditch-Control; R-A: Runnel-Action; R-C: Runnel-Control).
Elevation: Figure 9 shows the average elevation of the ditch remediation and runneling transects
in cross-section for the control and action marsh areas. For individual cross-sections plots for each
transect, see Appendix A.
The control ditches are generally deeper and narrower, on average, than the action ditches. Also,
the average marsh elevation on either side of the ditch is higher in the control than the average
marsh elevation in the action section. However, this difference in elevation does not appear
significant as there is more variability in the marsh elevation of the action ditches. The proposed
runnel areas show very little variability in elevation within and across the transects and are
comparable between the control and action marsh sections.
There were only four transects with pools: R-A-4 (5.3 m2), R-A-6 (8.1 m2), R-C-4 (0.4 m2), and
D-A-3 (4.4 m2).
D-A D-C R-A R-C
120
100
80
60
40
20
0
0 -5 -10 -15
Marsh Soil Depth (cm)
-20 -25 -30 Percent Time Flooded (%)
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 13
Figure 9: Plots showing the average cross-sectional elevation of the four monitoring transect types in the Barnstable Great Marsh: control - ditch remediation (a), control
runnel (b), action - ditch remediation (c), and action - runnel (d). Data was collected in August 2023 using a Leica digital level. Error bars represent one standard deviation
from the mean. Note that the 10m distance along the transects is also the center of the transect and the 8.5m and 11.5m mark the marker horizons (only four out of six of
each transect type received marker horizons).
a) 2.0 Control: Ditch (n=6)
1.5
1.0
0.5
0.0
0 5 10
Distance along transect (m)
15 20
d) 2.0 Action: Runnel (n=6)
1.5
1.0
0.5
0.0
0 5 10
Distance along transect (m)
15 20
c) 2.0 Action: Ditch (n = 6)
1.5
1.0
0.5
0.0
0 5 10
Distance along transect (m)
15 20
b)2.0 Control: Runnel (n=6)
1.5
1.0
0.5
0.0
0 5 10
Distance along transect (m)
15 20 Average Elevation (NAVD88 in m) Elevation (NAVD88 in m) Elevation (NAVD88 in m) Elevation (NAVD88 in m)
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 14
Accretion: Except for elevation, no additional data were collected from the marker horizon plots
in 2023. The feldspar remained visible at the marker horizon plots over the course of the 2023 field
season indicating that the feldspar had set effectively. The depth to the feldspar layer was measured
in all 32 established marker horizon plots in July and August 2024 to collect baseline accretion
rates prior to restoration.
Figures 10 and 11 show control and action marker horizon plots categorized by anticipated
treatment type (i.e., ditch or runnel). The data indicate that lower accretion rates generally occur
in plots near the upland edge, a trend particularly visible in the action marker horizon plots, and
higher accretion rates generally occur in plots near tidal channels and/or located further seaward
(Figures 10 and 11).
Figure 10: A map of the control marker horizon plots deployed at Great Barnstable Marsh. Each plot is represented by
a circle and the color indicates the anticipated restoration treatment (blue for ditch and orange for runnel). The size of
the circles corresponds to accretion rate (mm/year). Plot labels include transect (or replicate) number and distance
along transect.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 15
Figure 11: A map of the action marker horizon plots deployed at Great Barnstable Marsh. Each plot is represented by
a circle and the color indicates the anticipated restoration treatment (blue for ditch and orange for runnel). The size of
the circles corresponds to accretion rate (mm/year). Plot labels include transect (or replicate) number and distance
along transect.
Accretion is generally higher in the ditch plots than in the runnel plots (Figure 12). Average
accretion is greater in the ditch plots in both the action and control sections of the marsh (Action
– Ditch average = 5.3 mm/year; Action – Runnel average = 4.0 mm/year; Control - Ditch average
= 6.2 mm/year; Control - Runnel average = 3.8 mm/year) (Figure 12).
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 16
Figure 12: A bar plot showing accretion rate (mm/year) for each marker horizon plot deployed at Great Barnstable
Marsh along transect types: Action – Ditch (solid blue), Action – Runnel (solid orange), Control – Ditch (thatched
blue), and Control – Runnel (thatched orange). The star symbol indicates a marker horizon plot on a transect near a
pool.
For the marker horizon plots, runnel plots are higher in elevation than ditch plots (average runnel
plot elevation = 1.6 m; average ditch plot elevation = 1.4 m), except for one ditch plot (Control –
Ditch plot: D-C-2-8.5) with an elevation of 1.56 m (Figure 13). There is a weak but present
relationship between accretion and elevation, with higher elevation plots generally having lower
accretion rates and vice versa, although plots D-C-5-8.5 and D-A-3-8.5 have anomalously high
accretion rates at higher elevations (Figure 13). There is also a weak but present relationship
between accretion rate and average S. alterniflora stem height, with greater accretion generally
occurring in plots with greater average S. alterniflora stem heights (Figure 14). This relationship
is opposite to the relationship between accretion and elevation (Figures 13 and 14). The runnel
plots in the control and action sections of the marsh have consistently shorter S. alterniflora stem
heights than the ditch plots, indicating the presence of short-form S. alterniflora in runnels and
tall-form S. alterniflora at ditches.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 17
Figure 13: Accretion Rate (mm/year) vs. Elevation (m) for ditch (blue) and runnel (orange) marker horizon plots
deployed at Great Marsh in the action (triangles) and control (circle) sections. The equation represents the best
linear fit for all the data. The R2 value represents the goodness of fit for the linear model.
Figure 14: Accretion (mm/year) vs. Average Spartina alterniflora stem height (cm) for all ditch (blue) and runnel
(orange) marker horizon plots deployed at Great Marsh in the action (circle) and control (triangle) sections of
the marsh. The equation represents the best linear fit for all data. The R2 value represents the goodness of fit for
the linear model.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 18
Figures 15 and 16 show accretion rate versus the ratio of S. alterniflora cover (Sa) to S. patens
cover (Sp) and the ratio of unvegetated cover (Un) to vegetated cover (Vg), respectively. The S.
alterniflora to S. patens ratio is calculated as: Sa / (Sa + Sp + 1). The unvegetated cover to
vegetated cover ratio is calculated as: Un / (Un + Vg + 1), where unvegetated cover includes bare
areas, dead vegetation, and wrack, and vegetated cover includes all live plants.
There is a clustering of data points around an S. alterniflora to S. patens ratio of 1, with most
marker horizon plots having an S. alt to S. pat ratio of 0.8 or greater (Figure 15). These marker
horizon plots have accretion rates ranging between 2 mm/year and 8 mm/year (Figure 15). Below
an S. alt to S. pat ratio of 0.6, the data points become more scattered, with accretion rates ranging
from less than 2 mm/year to slightly greater than 12 mm/year across varying S. alt to S. pat ratios
(Figure 15). The average S. alt to S. pat ratio is greater in the runnel treated plots (0.82) than in the
ditch treated plots (0.62).
The relationship between accretion and the unvegetated to vegetated ratio (Un:Vg) is less clear
(Figure 16). Accretion rates vary greatly across Un:Vg values. In other words, both higher and
lower rates of accretion were measured in plots with a wide range of unvegetated percent cover.
However, there appears to be a slight clustering of data points at Un:Vg values less than 0.4,
indicating that more plots have greater vegetated cover than unvegetated cover (Figure 16).
Average Un:Vg is slightly greater in the ditch plots (0.34) than in the runnel plots (0.24). Runnel
plots generally had higher percentages of vegetated cover compared to the ditch plots (Figure 16).
Figure 15: Accretion rate (mm/year) vs. the ratio of S. alterniflora percent cover to S. patens percent cover for
all ditch (blue) and runnel (orange) marker horizon plots deployed at Great Marsh in the action (circle) and
control (triangle) sections of the marsh.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 19
Figure 16: Accretion rate (mm/year) vs. the ratio of unvegetated percent cover to vegetated percent cover for all
ditch (blue) and runnel (orange) marker horizon plots deployed at Great Marsh in the action (circle) and control
(triangle) sections of the marsh.
Average accretion rates were calculated for marker horizon plots along transects with pools (n=6)
and without pools (n=26) (Figure 17). The average accretion rate for marker horizon plots near
pools (Average = 6.06 mm/year) was higher than those along transects without pools (Average =
4.47 mm/year).
Figure 17: Average accretion rate (mm/year) for marker horizon plots along transects near pools and transects
without pools (‘No Pools’). Error bars represent one standard deviation from the mean.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 20
Vegetation: Figures 18 through 20 show results from the vegetation surveys conducted at the
Barnstable Great Marsh in August 2023. Spartina alterniflora was the most prevalent species
observed across all twenty-four transects. Ditches showed more variability of species composition
along transects than the runnels. The ditch transects generally had greater percentages of Spartina
patens species than the runnel sites. S. patens appears to be most successful at least two meters
from the ditch center. However, the ratio of S. alterniflora to S. patens generally declines again 10
meters from the ditch center. S. patens is more prevalent in the control marsh than the action marsh.
In both marsh areas, the ditch center is mainly composed of unvegetated bare sediment. S.
alterniflora grew tallest at the ditch edge (i.e., 0.5 m from the ditch center; Figure 18).
The runnels were dominated by short-form S. alterniflora (Figures 19 and 20) with very little
variation across or within a transect type. The percent cover of S. alterniflora was higher in the
control plots than in the action plots although this difference does not appear statistically
significant. Stem heights were comparable across all runnel plots. The runnel plots were similar in
composition and stem height compared to the 0 and 20m ditch plots (i.e., plots located 10m from
center of ditch). Distichlis spicata was more abundant in the action – runnel plots than any other
transect type.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 21
Discussion: a) b)
c) d)
Figure 10: Bar plots depicting average percent cover of major plant species and other cover types observed in 0.5 m2 plots along the four monitoring transect types in
the Barnstable Great Marsh (August 2023): control - ditch remediation (a), control - runnel (b), action - ditch remediation (c), and action - runnel (d). Error bars
represent one standard deviation of the mean.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 22
a) b)
c) d)
Figure 11: Bar plots depicting average ratios of unvegetated to vegetated cover and Spartina alterniflora to Spartina patens in 0.5 m2 plots along the four monitoring
transect types in the Barnstable Great Marsh (August 2023): control - ditch remediation (a), control - runnel (b), action - ditch remediation (c), and action - runnel (d).
Error bars represent one standard deviation of the mean.
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 23
Figure 2012: Bar plot showing average height of five tallest Spartina alterniflora stems in 0.5m2 plot. Data collected
at six replicates of each transect type in the Barnstable Great Marsh in August 2023 (D – A: ditch remediation -
action; D – C: ditch remediation - control; R – A: runnel - action; R – C: runnel – control). Error bars represent one
standard deviation of the mean.
DISCUSSION:
Collecting accurate baseline hydrologic data is critical for tracking changes to the flooding and
drainage patterns within the marsh that result from implementing restoration techniques, such as
ditch remediation and runneling. Elevation and vegetation measurements along each transect were
also important elements for this study because they are likely to change in response to the
restoration activities and by evaluating this change, managers can assess the effectiveness of the
project and adjust management strategies as needed for areas that do not meet restoration targets.
The fact that the action and control plots were so comparable and fairly uniform (marsh platform
elevations vary by less than 10 cm) is important for comparable post-restoration data comparisons.
Although successful water level data collection was delayed due to ineffective drainage in the first
iterations of the groundwater well design, APCC is satisfied with the final set of water level data
collected from October 25 through December 1. The second set of neap tides was impacted by
high winds, but the full period of data collection included two spring and two neap tides showing
the average range of the tide and drainage conditions during these two lunar phases near the
proposed runnel and ditch remediation treatments.
The surface water data at the control and action areas for the two restoration treatments provides
the full range of the tide over an average lunar cycle (30 days) including the extent of drainage in
the creeks during low tide; all ditches completely drained at low tide and the ditch at D-A-6 (where
the ditch remediation-action logger was located) was much shallower than the other ditches
monitored. During the first neap tide (unimpacted by storms), the marsh only 1m from the ditch
edge rarely floods. In contrast, during spring tides the marsh floods at least once or, more often,
twice a day. Since the control area of the marsh is slightly higher in elevation, the marsh platform
140
120
100
80
60
40
20
0
N = 6
D - A
D - C
R - A
R - C
0 5 8 9.5 10
(center)
Plot ID
10.5 12 15 20 S. alterniflora Stem Heights (cm)
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 24
at the control site floods less frequently than the marsh at the action station. This difference in
flooding may explain why Spartina patens cover is higher in the plots at the control site as S.
patens is a less flood-tolerant species than Spartina alterniflora.
The groundwater data collected at the four stations (control – ditch, control – runnel, action – ditch,
and action – runnel) shows the time flooded during high tide as well as the level of drainage during
low tides. The low tide depth-to-groundwater is lower during neap tides than the spring tides – a
relationship that holds true for all areas surveyed. However, the major finding from the
groundwater datasets is the difference in relative groundwater table depth between the proposed
runnel areas and the ditches. The marsh near the ditches drains to a groundwater depth that is
roughly twice that of the runnel sites. During spring tides, the marsh surface at runnel sites barely
drains at all. The presence of short-form S. alterniflora at the runnel sites further corroborates this
finding of poor drainage as S. alterniflora does not grow as tall in saturated soils due to the reduced
oxygen available to the roots.
The lack of effective drainage in the root zone justifies the need for runneling. Runneling improves
drainage to these waterlogged areas on the marsh providing better habitat for robust vegetation
growth. Note that there were very few pools of standing water near the transects indicating that
the marsh is in the early phases of the waterlogged trajectory. After the creation of runnels as part
of the restoration activities, water level loggers will be redeployed in these areas to assess whether
the implementation of a runnel has increased the groundwater depth at low tides as intended. Future
vegetation survey results should demonstrate better drainage through higher percent cover of S.
patens and/or taller S. alterniflora stems.
One other key finding from the runnel monitoring effort was the lower percent cover of S.
alterniflora and greater coverage of high marsh species, including S. patens and Distichlis spicata,
in the runnel-action plots as compared to the runnel – control plots. High marsh species are
generally better competitors than S. alterniflora at higher elevations where flooding is more
infrequent. These small differences in plant community composition between the control and
action area will be important to keep in mind when comparing and tracking changes from the
restoration.
Comparatively, more drainage was seen in the groundwater wells near the ditches. This finding is
concerning because where ditches are relatively deep, such as the one monitored in the control
marsh, and densely spaced (≤ 25m apart), the groundwater table can get too low during neap tides
causing decomposition of the organic matter in the soil and subsidence of the marsh elevation
across a large area. By carefully removing unnecessary ditches through a natural remediation
process, the groundwater depth can be restored to prevent accelerated decomposition rates.
The average accretion rate at Barnstable Great Marsh (4.77 mm/year) is within the range of
accretion rates measured at several restored and natural marshes on Cape Cod (Eagle et al. 2022).
At Bass Creek, geographically adjacent to Barnstable Great Marsh, historic (pre-2000) and recent
(post-2000) accretion in the marsh (4.3 ± 2.6 mm/year and 3.8 ± 0.8 mm/year, respectively; Eagle
et al. 2022) are comparable to average accretion at Barnstable Great Marsh. While the methods
used by Eagle et al. (2022) to measure accretion are not directly comparable to accretion measured
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 25
via marker horizons (due to the difference in the time over which accretion is calculated), the
similarity in accretion rates gives credibility to the measurements collected at the Barnstable Great
Marsh. Based on this review, the Barnstable Great Marsh also shows an average accretion rate
robust enough to maintain vertical elevation gain with future sea level rise.
The first year of marker horizon data clearly shows higher accretion rates, on average, at the lower
elevation of the ditches than at the runnel sites irrespective of placement in the marsh (i.e., control
vs. action). Also, the average accretion rate was higher near pools, where elevations are generally
lower. Based on the data analysis, this negative correlation with elevation could be related to a
combination of several key accretion drivers. First, the reduced flooding at the runnel sites during
neap tides (as seen in the water level data) likely limits the sediment supply to those higher plots.
Second, although S. alterniflora was denser at the runnel locations (as seen in the unvegetated to
vegetated cover results), the greater cross-sectional area of the taller S. alterniflora stems at the
ditch sites may increase the rate of sediment deposition by trapping more suspended particles
during tidal flooding. The fact that areas at lower elevations experience a higher accretion rate is
promising as it means these areas will rebound relatively quickly once a more natural groundwater
table depth is restored through ditch remediation and runneling.
In summary, the 2023 and 2024 monitoring efforts were successful in capturing the pre-restoration
hydrology, vegetation, accretion, and elevation conditions in two areas of the Barnstable Great
Marsh. By collecting similar information in the action area, where Phase 1 restoration is proposed,
and in a control area, where restoration actions will not be implemented in the near-term, Mass
Audubon and partners can evaluate restoration success and adapt management strategies as
necessary if certain restoration targets (e.g., lowering the groundwater table in the runnel sections
and raising the groundwater table near the ditches) are not met.
LITERATURE CITED:
Ackerman, K.V., Defne, Z., and Ganju, N.K., 2021, Geospatial Characterization of Salt Marshes
for Massachusetts: U.S. Geological Survey data release, https://doi.org/10.5066/P97E086F.
Adamowicz, S.C., G. Wilson, D.M. Burdick, W. Ferguson, and R. Hopping. 2020. Farmers in the
marsh: Lessons from history and case studies for the future. Wetland Science & Practice: 183-195.
Burdick, D.M., G.E. Moore, S.C. Adamowicz, G.M. Wilson, and C.R. Peter. 2020. Mitigating the
legacy effects of ditching in a New England salt marsh. Estuaries and Coasts 43:1672–1679/
Meagan J. Eagle, Kevin D. Kroeger, Amanda C. Spivak, Faming Wang, Jianwu Tang, Omar I.
Abdul-Aziz, Khandker S. Ishtiaq, Jennifer O'Keefe Suttles, Adrian G. Mann. 2022. Soil carbon
consequences of historic hydrologic impairment and recent restoration in coastal wetlands. Science
of The Total Environment. Volume 848. 157682. ISSN 0048-9697.
Lynch, J. Personal communications circa 2018. Inundation Data – Flooding Tool Excel Macro.
Northeast Coastal & Barrier Network. National Park Service. james_lynch@nps.gov
A s s o c i a t i o n t o P r e s e r v e C a p e C o d | 26
Perry, D.C., W. Ferguson, C.S. Thornber. 2021. Salt marsh climate change adaptation: Using
runnels to adapt to accelerating sea level rise within a drowning New England salt marsh.
Restoration Ecology 30 (1): 13466.
Watson, E.B., W. Ferguson, L.K. Champlin, J.D. White, N. Ernst, H.A. Sylla, B.P. Wilburn and C.
Wigand. 2022. Runnels mitigate marsh drowning in microtidal salt marshes. Front. Environ. Sci.
10:987246.
Appendix 3: EA Technical Memorandum
301 Metro Center Boulevard, Suite 102
Warwick, Rhode Island 02886
Telephone: 401-287-0369
www.eaest.com
Barnstable Great Marsh Wildlife Sanctuary Technical Memorandum for
Barnstable, Massachusetts Design Narrative for Barnstable Great Marsh Restoration Project
June 26, 2025
TECHNICAL MEMORANDUM
TO: Sara Grady, Ph.D. – Mass Audubon Senior Coastal Ecologist
FROM: Alex Patterson, CERP, AWB – EA Senior Ecologist and Project Manager
SUBJECT: Design Narrative for Barnstable Great Marsh Salt Marsh Restoration Project
Barnstable Great Marsh Wildlife Sanctuary, Barnstable, Massachusetts
EA Engineering, Science, and Technology, Inc., PBC (EA) has been contracted by Mass
Audubon to prepare permit-level engineering design documentation and complete associated
data collection and analysis for the proposed salt marsh restoration project at Mass Audubon’s
Barnstable Great Marsh Wildlife Sanctuary located in Barnstable, Massachusetts. This design
narrative provides a summary of the project background and the work completed by EA to date.
Funding for this phase of the project has been provided by the Massachusetts Department of Fish
and Game In-Lieu Fee Program. Project partners also include Northeast Wetland Restoration,
Rimmer Environmental Consulting, and the Association to Preserve Cape Cod (APCC).
1. PROJECT AREA DESCRIPTION
The project area is an approximately 77-acre portion of the approximately 3,800-acre Sandy
Neck salt marsh and barrier beach system located on the north shore of Cape Cod (Figure 1). The
project area consists entirely of a tidally influenced salt marsh and associated tidal creek system,
with the exception of one small (< 0.5 acre) upland island. Mass Audubon owns the project area
in its entirety. The project area is located entirely within the Sandy Neck Barrier Beach System
Area of Critical Environmental Concern, is mapped by the Massachusetts Natural Heritage and
Endangered Species Program as Priority Habitats of Rare Species (PH 892) and Estimated
Habitats of Rare Wildlife (EH 697), and has been identified as a priority site for saltmarsh
sparrow (Ammodramus caudacutus) by the Atlantic Coast Joint Venture. The project area is also
located entirely within the Old King’s Highway Regional Historic District. The closest
Environmental Justice Population to the project area is located approximately 1 mile
south/southeast and is designated based on the minority and income criteria (block group 1,
census tract 153).
2. PROJECT BACKGROUND
The need for restoration at this site was identified by Mass Audubon in 2020 following a
vulnerability assessment of the project site. This assessment indicated some resilience against sea
level rise (SLR) impacts due to elevation capital and high salt marsh migration potential, but also
early signs of stress including pool formation and vegetation loss. As with nearly all salt marshes
in the Northeast, the project site has evidence of an agricultural legacy including embankments
and ditching that have impacted the hydrology of the marsh and left some parts over-drained and
Page 2
EA Engineering, Science, and Technology, Inc., PBC June 26, 2025
Barnstable Great Marsh Wildlife Sanctuary Technical Memorandum for
Barnstable, Massachusetts Design Narrative for Barnstable Great Marsh Restoration Project
others under-drained. Under a separate contract with Mass Audubon in 2022, EA developed a
restoration reconnaissance report for the project site which identified ditch remediation and
runneling as key techniques to restore marsh functions. An initial design for ditch remediation
and runneling at the project site was completed by Northeast Wetland Restoration (NWR) in
2023 which included identifying the locations of early period and late period embankments,
ditching infrastructure within a subset of the project site, and the existing tidal channel network,
as well as the proposed locations of runneling and ditch remediation. The overall goal of
undertaking the proposed work is to reverse the subsidence trajectory of the project site by
restoring a more natural pattern of sediment deposition and biomass expansion processes of the
marsh, thereby enhancing the ability of the marsh to sustain itself in the face of SLR and other
stressors.
Pre-restoration monitoring of the site has been conducted by APCC and included an evaluation
of surface water and groundwater hydrology, vegetation communities, marsh elevations, and
accretion rates (Mora et al. 2024). Since the completion of the initial design in 2023, the
Massachusetts Department of Environmental Protection (MassDEP) has released a regulatory
guidance document entitled Wetlands Program Guidance on Massachusetts Wetlands Protection
Act and Water Quality Certification Provisions Regarding Salt Marsh Restoration Techniques,
including Ditch Remediation, Runnels, and Marsh Habitat Mounds (18 June 2024), also known
as the Trio Guidance. Based on this guidance, Mass Audubon determined that additional data
collection and analysis was necessary to support project permitting. EA was contracted by Mass
Audubon in January 2025 to complete the additional data collection required by the MassDEP
guidance and prepare permit-level engineering designs and associated documentation for the
proposed project.
3. DATA COLLECTION AND ANALYSIS
As discussed above, EA was contracted by Mass Audubon to complete a specific set of data
collection and analysis tasks for the project site in accordance with the Trio Guidance. To
support these tasks, EA prepared a field study plan for the project which was finalized on 10
April 2025. Tideshed mapping data available from U.S. Geological Survey (USGS) (Figure 2)
was used to subdivide the project site for the purposes of field and desktop data collection and
analysis. The 2021 USGS LiDAR: Central Eastern Massachusetts data set represents the latest
and best quality LiDAR data in the vicinity of the project site (Commonwealth of Massachusetts
2023) and was used for all figures and drawings that display topographic contours. It has a listed
vertical accuracy of 1.5 inches (in.) (3.7 centimeters [cm]), horizontal accuracy of 4.3 in. (11 cm)
with a point spacing of 7.9 in. (20 cm) (USGS 2021). The following section provides a summary
of the methods and results of the data collection and analysis tasks completed by EA under this
contract.
3.1 DESKTOP DATA ACQUISITION
3.1.1 Locations of Pannes and Pools
Data collection related to pannes and pools within the project area involved both desktop
evaluation and field observations. The objective of the desktop evaluation was to determine the
locations of pannes and pools within the project area based on a review of recent aerial imagery.
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This evaluation was performed on a preliminary basis and was confirmed through field
observations, as discussed below. To determine the locations of pannes and pools within the
project area, publicly available aerial imagery for the project site from 2023 (the most recent
high-quality aerial imagery collected at the lower end of the tidal cycle) was manually reviewed
in geographic information system (GIS) and the locations of apparent pannes and pools were
marked.
The desktop evaluation resulted in the identification of 314 pannes and pools within the project
site. The distribution of these features as assessed through the desktop analysis is displayed on
Figure 3.
To evaluate the degradation of the marsh, the unvegetated – vegetated ratio (UVVR) was
assessed using publicly available aerial imagery. The UVVR of a marsh has been shown to be an
indicator of its vulnerability to SLR as this metric is highly correlated with a marsh’s net
sediment budget (Ganju et al. 2017). A sediment surplus may result in vertical expansion of a
marsh while a deficit will likely result in subsidence. Ganju et al. (2017) determined that marshes
with a UVVR greater than 0.1 are unstable and that this value represents a tipping point to
drowning and/or lateral contraction.
Figure 4 shows the UVVR data product for the project site (2014-2018) (Couvillion et al. 2022).
This data layer includes coastal areas of the contiguous United States and displays the ratio of
unvegetated to vegetated area at each pixel (approximately a 30-meter by 30-meter rectangle) as
calculated from Landsat 8 satellite imagery. The UVVR data for the project site indicate that
approximately 42 acres (55 percent [%]) of the project site have a UVVR of greater than 0.1.
3.1.2 Sediment Supply
Sediment supply to the marsh may affect the overall success of the project and has implications
for the ability of the marsh to keep pace with SLR. EA reviewed the results of APCC’s sediment
accretion study to assess the status of sediment supply at the project site.
APCC used horizontal markers to measure sediment accretion over approximately one year
(June/July 2023 to July/August 2024) at the project site (Mora et al. 2024). The markers
consisted of feldspar powder inside 0.25-meter plots, and accretion was measured using cores in
each plot. Plots were conducted in ditches where remediation is proposed and at the locations of
proposed runnels, as well as in control plots. The average accretion measured in each plot type
was 5.3 millimeters per year (mm/year) in the action ditches, 4.0 mm/year in the action runnels,
6.2 mm/year in the control ditches and 3.8 mm/year in the control runnels (Mora et al. 2024).
The average accretion rate at the site was determined to be 4.77 mm/year (Mora et al. 2024).
Relative SLR (RSLR) projections for Boston are expected to be applicable to the project site.
Based on monthly mean sea level data from 1921 to 2024, the RSLR trend has been roughly
3 mm/year (National Oceanic and Atmospheric Administration [NOAA] 2024). The Interagency
Task Force 2100 RSLR value from the low emissions scenario yields a RSLR estimated rate of
4.91 mm/year between 1992 and 2100. The deficit becomes more exacerbated under higher (and
more likely) emission scenarios. These results demonstrate that even under the lowest RSLR
projections, it is unlikely that natural sediment accretion and biomass expansion alone will allow
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the marshes at the project area to keep pace with increased water surface elevations, and that
additional intervention is likely to be needed to preserve salt marsh habitat at this location.
3.1.3 Vegetative Community Mapping
To assist in mapping the general extents of vegetative communities at the site, EA developed a
GIS-based figure that plots the locations of the elevation contours associated with the mean sea
level (MSL), mean high water (MHW), mean higher high water (MHHW), and highest
astronomical tide (HAT) tidal datums based on publicly available local tide data from the NOAA
(Figure 5). These tidal datum elevations can serve as a proxy for estimating the locations of high
marsh, low marsh, mudflats, and subtidal areas throughout the site. The elevation contours
associated with mean low water (MLW) and mean lower low water (MLLW) are located
seaward of the project site boundary. Table 1 identifies the portion of the project site within each
tidal inundation zone.
Table 1. Area of Project Site within Tidal Inundation Zones
Zone
Elevation Range
(feet, NAVD88)
Acres of
Project Site
Percent of
Project Site
Typical Vegetative
Community
< MSL < -0.3 4.07 5.4% Mudflats/
Subtidal
MSL to MHW -0.3 to 4.3 24.42 32.1% Low Marsh
MHW to MHHW 4.3 to 4.7 25.45 33.5% High Marsh
MHHW to HAT 4.7 to 6.8 21.40 28.2% High Marsh/
Salt Shrub
> HAT > 6.8 0.62 0.82% Uplands
NAVD88 = North American Vertical Datum of 1988
It should be noted that the National Tidal Datum Epoch (NTDE) covers the period from 1983 to
2001 and is tied to a baseline year (mid-point) of 1992. The NTDE covers a 19-year period to
ensure that an 18.6-year astronomical cycle that includes all significant variations in the
distances from Earth to the moon and sun, which produce slowly varying changes in the tidal
range, is accounted for in the epoch (Sweet et al. 2022). The current NTDE is more than 20 years
old, and it is NOAA’s policy to consider revising the NTDE every 20 to 25 years. The NTDE
needs to be regularly revised to account for changes in tidal constituents, SLR, and vertical land
movement. As a result, tidal datum elevations referenced to the NTDE for the period of 1983 to
2001 are likely an underestimate of current water levels since they have not taken recent SLR
into account.
3.2 FIELD DATA ACQUISITION
Field data acquisition was completed by two EA personnel over the course of 3 field days in
late April 2025. Prior to field collection, Alpha Survey Group installed a permanent survey
benchmark at the site for calibration of field equipment and future project implementation
(Attachment A). All elevation data collected were tied to this survey benchmark and referenced
to the NAVD88. EA used Real-Time Kinematic (RTK) Global Positioning System (GPS) survey
equipment (RTK rover with virtual reference station network) to record the horizontal location
and ground elevation at points in the field. Specifications for the Trimble R980 are provided in
Attachment B. A photographic log is included as Attachment C.
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3.2.1 Vegetative Community Mapping
On-site vegetative community mapping was completed to characterize the distribution of plant
community types throughout the project area. The schedule for data collection (late April)
limited the ability to perform a detailed characterization of plant communities in the field;
however, the primary objective was to establish the extents of high marsh, low marsh, and
unvegetated areas.
Vegetation community mapping occurred along the transects displayed on Figure 6. While
traversing each transect, EA used RTK GPS survey equipment to record the horizontal location
and ground elevation at points along the transect where the vegetative community transitions
from one community type to another. The marsh community type definitions provided in Table 2
(adapted from Kutcher 2022) were used for this process to the greatest extent practicable;
however, as discussed previously, completing this work outside the growing season limited the
specificity that could be achieved.
Table 2. Salt Marsh Community Cover Types
Marsh Habitat Description
Salt Shrub Infrequently flooded shrub community (>30% shrub cover) located at higher elevations on the
marsh platform and at the upland interface; typically dominated by Iva frutescens, Baccharis
halimifolia
Brackish Marsh
Native
Emergent community where freshwater from the watershed dilutes infrequent flooding by
seawater; typically dominated by non-halophytic, salt tolerant vegetation such as Typha
angustifolia, Schoenoplectus robustus, Spartina pectinata
Phragmites Areas where the invasive common reed Phragmites australis cover > 30%
Meadow High
Marsh
Irregularly flooded emergent high marsh community dominated by any combination of
Spartina patens, Juncus gerardii, Distichlis spicata; S. alterniflora absent
Mixed High
Marsh
Irregularly flooded emergent high marsh community comprised of any combination of S.
patens, Juncus
Spartina
alterniflora
High Marsh
Irregularly flooded emergent high marsh; typically, monoculture of S. alterniflora, although
Salicornia sp. may be present
Dieoff Bare
Depression
Shallow gradual depression on marsh platform, irregularly flooded by tides but typically
remaining flooded or saturated to the surface throughout the tide cycle; <30% vascular
vegetation cover, or bare decomposing organic soil, typically with remnant roots of emergent
vegetation; may have algal mat, filamentous algae, wrack, or flocculent matter present
Low Marsh Regularly flooded, typically sloping emergent community located at the tidal edges of the
marsh and dominated by tall-form S. alterniflora
Dieback
Denuded Peat
Typically non-depressional marsh platform feature; marsh peat is exposed (vegetation < 30%)
and perforated from grazing, crab burrowing, and erosion; typically at or near tidal edge
Natural Panne Shallow steep-sided depression on marsh platform with clearly defined edge; irregularly
flooded, typically dry at low tide; species may include any cover of Plantago maritima, Sueda
maritima, Salicornia sp., J. gerardii, Aster sp.
Natural Pool Shallow steep-sided depression on marsh platform with clearly defined edge; irregularly
flooded by tides but typically remaining flooded throughout the tide cycle; organic or sandy
substrate lacking emergent vegetation and roots but may support Ruppia maritima
Natural Creek Narrow, natural, unvegetated, regularly flooded or subtidal feature cutting into the marsh
surface; typically sinuous
Ditch Manmade ditches and associated spoils on the marsh surface; typically linear
Bare Sediments Irregularly or infrequently flooded; sandy or gravelly sediments on the marsh surface with
< 30% vegetation cover; typically from recent washover event or elevation enhancement
project
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The locations of the vegetative communities identified along the transects were plotted in GIS
and are displayed on Figure 7. Table 3 summarizes the results of this assessment.
Table 3. Vegetative Community Transect Results
Community
Type
Percent of Transect Length
A B C D E F Cumulative
Creek 3.1% 9.4% 17.3% 0.7% 3.0% 1.6% 6.5%
Ditch 9.9% 0.8% 0.0% 0.0% 3.6% 3.9% 3.3%
High Marsh 63.9% 63.1% 53.3% 63.9% 49.1% 40.9% 57.5%
Low Marsh 16.6% 22.7% 24.5% 22.3% 39.3% 44.6% 26.2%
Panne 5.4% 0.0% 2.6% 2.0% 3.6% 4.2% 2.8%
Phragmites 1.2% 1.8% 2.3% 0.0% 0.0% 0.0% 1.1%
Pool 0.0% 0.0% 0.0% 0.8% 0.7% 0.0% 0.2%
Unvegetated 0.0% 2.2% 0.0% 10.3% 0.8% 4.9% 2.3%
While the data collection for vegetative communities was limited to a relatively small segment of
the marsh, these results provide a high-level assessment of the relative abundance of each
community type within the project site. Exhibit 1 displays the cumulative results of the
vegetative community field mapping completed for the project.
Exhibit 1. Cumulative Results of Vegetative Community Field Mapping
3.2.2 Crab Burrow Density
Crab burrow density was documented along the transects displayed on Figure 6. Crab burrow
density was evaluated while traversing each transect and was limited to the area of the marsh
visible from the transect. As transects were traversed, EA indicated crab burrow density on a
map of the site using the following rankings:
• 0 = no crab burrows observed
• 1 = low density of crab burrows
• 2 = moderate density of crab burrows
• 3 = high density of crab burrows
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Best professional judgement and experience at similar sites was used to assign a rank to each
area.
The locations within the project site where crab burrow density was determined to be high are
displayed on Figure 8. In general, these areas were restricted to the banks of creeks and ditches
as well as some pannes. Some areas of bank sloughing, primarily along major creeks, were noted
in the field and attributed at least in part to crab burrowing activity. Several purple marsh crabs
(Sesarma reticulatum) were observed during the course of field data collection activities. A
pattern of marsh peat degradation along the upland edge of the marsh was also noted; however, it
was unclear whether this was related to crab burrow activity. Crab burrow density throughout
most of the site was low to moderate.
3.2.3 Panne and Pool Observations
Stable pannes and pools provide valuable resources including overwintering habitat for fish
(Smith and Able 1994); protection from predators to promote fish growth and reproduction rates
(MacKenzie and Dionne 2008); and nesting, foraging and roosting habitat for shorebirds (Bolduc
and Afton 2004; Sripanomyom et al. 2011). Conversely, unstable pannes and pools are subject to
mass expansion, creating large swaths of unvegetated areas more susceptible to the impacts of
sea level rise within the marsh interior (McKown et al. 2023). These areas, especially those
intermediate in size, can merge with adjacent depressions further expediting their dominance
across a marsh (Himmelstein et al. 2021). By identifying expanding and newly forming
depressions, runnel locations can be prioritized to encourage drainage without disturbing the
pannes and pools that support important ecological functions.
EA visited the locations of pannes and pools identified through desktop mapping to determine
that the feature was present and determine whether the feature appeared to be stable or recently
formed. The following data were collected at each feature visited in the field:
• The approximate dimensions and depth relative to the adjacent marsh platform of the
feature was estimated in the field. The diameter of each pool was measured along the
longest dimension.
• Observations of vegetation were noted as: 1) well-vegetated, 2) dieback (reduced
vegetation, < 30% cover), or 3) bare mudflat (0% vegetation) (adapted from Kutcher
2022). Special attention was paid to the presence of widgeon grass (Ruppia maritima).
Given the size of the project area and the number of pannes and pools, visiting each feature was
infeasible. EA attempted to visit as many features as practicable, including at least some features
within each project area tideshed. A total of 171 pannes and pools were visited in the field; of
these, 118 (69%) were identified in the desktop mapping and 53 (31%) were identified only
through field observations (Figure 9). Each panne/pool visited in the field was
photo-documented. The results of the field observations of pannes and pools are summarized in
Attachment D.
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The range of values for both the approximate depth and diameter of pools and pannes varied
significantly. The average depth of these features was 1.9 feet (range 0.3 feet to 6.0 feet, standard
deviation 1.1 feet) while the average diameter was 16.1 feet (range 1.5 to 82.0 feet, standard
deviation 12.6 feet). The median feature depth was 1.7 feet and the median feature diameter was
13.3 feet. Vegetation was absent in nearly every feature observed in the field; however given the
time of year during which the work occurred this result is likely not significant.
3.2.4 Topographic Data Collection at Proposed Runnels
EA visited runnel locations proposed by Mass Audubon to collect baseline cross-section
elevation data. Elevation data at proposed runnel locations will be used to appropriately size
runnels to encourage positive drainage of the marsh. Given the number of runnels proposed
(approximately 70), visiting each location was infeasible within the budgeted field schedule. EA
visited 46 proposed runnel locations, including at least some runnels in each of the project area
tidesheds.
Using the RTK GPS, the EA field team collected one elevation cross-section at the start and end
of each proposed runnel (total of two cross-sections per runnel). Each cross-section included one
elevation spot shot at the proposed thalweg and lateral spot shots 2-5 feet adjacent on either side
of the proposed runnel (Exhibit 2).
Exhibit 2. Elevation data collection approach at proposed runnels
These data are provided electronically in the computer-aided design (CAD) file for the design
drawings and can be used during project implementation to refine the proposed runnel widths
and depths to achieve the desired drainage outcome.
4. PROPOSED PROJECT DESCRIPTION
As discussed above, through a prior planning and conceptual design phase of the project, Mass
Audubon has identified ditch remediation and runneling as the preferred approach to addressing
legacy hydrologic modifications and vegetation loss within the project site marsh. The creation
of marsh habitat mounds is also proposed to beneficially reuse sediment generated through
runnel creation. These three techniques are addressed in the MassDEP Trio Guidance. EA was
contracted by Mass Audubon to prepare permit-level engineering design drawings and associated
documentation for the implementation of these techniques at the project site. The design
drawings prepared by EA depict the conceptual design prepared by NWR. Validation of NWR’s
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design was not included in EA’s project scope. The following section describes the primary
components of the proposed work including key design criteria and constraints.
4.1 ACCESS AND STAGING
Access and staging of equipment will be required to complete the proposed work described
herein. Access to the site will be coordinated by the contractor with the site owner, Mass
Audubon. The site can be accessed via the sanctuary entrance driveway off of Cranberry
Highway (Route 6A). An existing access path from the sanctuary entrance to the project area will
be available for use by the construction contractor (see drawing C-105). Some minor pruning of
low-hanging branches may be needed along this access route.
An approximately 600 square foot upland staging area is proposed to be located in the vicinity of
the viewing platform to store materials and equipment on a short-term basis (see drawing C-
105). The staging area is the former location of a small building which has recently been
removed and generally lacks woody vegetation. The contractor shall monitor the weather and
perform work during periods of low water when the marsh is not flooded. Erosion and sediment
controls as described in the following section should be used to protect the marsh during project
implementation.
4.2 EROSION AND SEDIMENTATION CONTROLS
Disturbance of existing soil surfaces is regulated by state law and local ordinances. Erosion and
sediment controls have been designed using the latest edition of the Massachusetts Erosion and
Sediment Control Guidelines for Urban and Suburban Areas as a guide (MassDEP 2003) and
will be updated at later design stages to accommodate permit conditions as necessary.
Erosion and sedimentation controls include:
• Straw wattle or approved alternative around the access and staging area to protect the
nearby marsh from silt and runoff.
• Wash area for equipment to reduce the tracking of sediment onto surrounding roadways.
• Use of low-pressure equipment (2 pounds per square inch or less) to minimize impacts to
the marsh. Marsh protection matting may be used to provide access over soft/wet areas
with prior approval from Mass Audubon and the Engineer.
• Performing dust control utilizing water and crushed stone or coarse gravel.
• Storing potential sources of pollution such as gasoline, diesel fuel, hydraulic oil, etc. in a
storage trailer or covered location outside of wetlands and properly disposed of offsite.
• Maintaining good housekeeping to minimize exposure of construction debris.
• Perform site stabilization as described in Section 4.6 of this report.
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The contractor will be required to install and maintain erosion control devices throughout the
project. These items are to be inspected daily, after each storm event, prolonged rainfall,
overwash events, and high tide events which result in flooding within the project area, and shall
be replaced when needed.
4.3 DITCH REMEDIATION
Ditch remediation is a relatively low-impact salt marsh restoration technique that entails placing
mowed salt hay in legacy agricultural and/or mosquito control ditches to facilitate sediment
accretion and regrowth of native vegetation within the ditch. The goals of this technique are to
restore primary marsh hydrology in the salt marsh and prevent undersaturation of the root zone
and subsidence of marsh peat from oxidation (MassDEP 2024). Ditch remediation is conducted
to reduce excessive drainage and help to establish vegetation within the ditches, and over time
restore the ditch to a vegetated marsh platform. Additional benefits from ditch remediation may
include an increase in groundwater levels as well as an increase in marsh elevation through
sediment accretion (MassDEP 2024).
Ditch remediation is proposed in the locations shown in the design drawings (Sheets C-103 to
C-106) consistent with the conceptual design for the project site. A total of approximately 15,072
linear feet of ditch remediation is proposed at the project site. Ditch remediation will be
completed by mowing a swath of marsh directly adjacent and parallel to the ditch and placing a
6-inch to 9-inch-deep bundle of the mowed salt hay into the ditch. The width of the mowed
swath will not exceed 20 feet on either side of the ditch in order to minimize impacts to potential
saltmarsh sparrow nesting habitat. The mowed salt hay will be secured in the ditch using jute
twine. The depth of ditches varies across the project site, but ditches are generally about 4 feet
deep relative to the adjacent marsh surface. As each lift will entail filling the ditch with up to 9
inches of mowed salt hay, multiple lifts are anticipated to be needed to achieve remediation.
Each treatment will occur at least 6 months following the previous treatment to allow time for
regrowth of the salt marsh vegetation used for remediation. As anticipated compaction rates of
salt hay vary significantly, remediation may require as little as 2 years or up to 4 years to be
achieved. Remediation is defined as a finished surface within the ditch that is within 8 inches of
the adjacent marsh surface and which is robustly vegetated with native salt marsh vegetation.
Based on the estimated dimensions (length, width, and depth) of ditches to be remediated, EA
estimates that approximately 7,260 cubic yards of salt hay will be necessary to complete the
proposed ditch remediation at the project site. This value is based on an assumed final
remediated ditch surface within 8 inches of the ditch bank and a 33% compaction rate as
recommended by project partners. Based on the approximate length and width of ditches
proposed for remediation, approximately 1.7 acres of vegetated marsh are anticipated to be
created through the implementation of this technique.
4.4 RUNNEL CREATION
Runnels are a shallow channel excavation used to allow water held within a subsidence basin on
the marsh platform to drain and improve natural marsh processes (e.g., movement of sediment,
increased primary productivity). Runneling may involve extending the primary channel the full
extent of the reach sub-basin (e.g., headward extension) or centralizing flow patterns to the
primary channel with a perpendicular reach (e.g., lateral extension). Runneling may also be used
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to remove a blockage in an existing tidal creek or serve as the start of a constructed channel that
is allowed to transform to dimensions more suitable for its associated drainage area and position
in the marsh for the establishment of a tidal creek (MassDEP 2024). The conceptual design for
the project site proposes both headward extension and lateral extension runnels, as shown in the
design drawings (Sheets C-103 to C-106).
Runnel creation will be accomplished through the excavation of small channels that act as
drainage paths for water. Runnels will be pitched to drain towards an existing primary channel;
given that the horizontal and vertical distance between the subsidence basin and the receiving
channel varies across each proposed runnel location, the proposed slope of each runnel will vary
but is typically at least 1%. Runnels will be excavated to the minimum dimensions necessary to
generate positive flow and allow upstream drainage to reconfigure the runnel as needed
(generally up to 3 feet wide and 1 foot deep) while minimizing the adverse impacts to the marsh
associated with larger anthropogenic ditches (described above). While runnel excavation can be
completed using hand tools, a low-ground-pressure construction vehicle outfitted with specially
designed blade that provides the appropriate dimensions and cross-sectional shape for the
intended feature is anticipated to be used for this project.
4.5 MARSH HABITAT MOUNDS
The Trio Guidance states that any clean sediment generated through runneling should be
beneficially reused in the local marsh to increase microtopographic features. Marsh habitat
mounds are small features intended to provide vegetated and elevated areas above the elevation
of daily tidal inundation with the intent to promote nesting primarily by saltmarsh sparrow
(MassDEP 2024). Marsh habitat mounds will be constructed with the material excavated from
runnel creation.
Based on the proposed runnel dimensions, approximately 1.5 cubic feet of material per linear
foot of runnel creation is assumed, resulting in a total volume of sediment generated through
runnel creation of 150 cubic yards. Individual runnels will range in size from 80 to 140 square
feet. According to the Trio Guidance, marsh habitat mounds should be designed not to extend
above the elevation of the HAT, which at the project site is 6.8 feet NAVD88. Based on the
observed elevations of high marsh vegetation at the project site, a target elevation of 5.25 feet
NAVD88 with a tolerance of ±0.25 feet is proposed for the marsh habitat mounds, yielding a
not-to-exceed elevation of 5.5 feet NAVD88. This elevation is anticipated to be appropriate
relative to local tidal datums to function as irregularly flooded marsh that is supportive of
saltmarsh sparrow nesting, while avoiding the potential for colonization by invasive common
reed (Phragmites australis) or upland plant species. Revegetation of marsh habitat mounds will
rely on germination from the native seed bank contained within the excavated sediments;
however, if sufficient revegetation is not achieved within 2 years, these areas will be planted
with Spartina patens plugs.
While the design specifies a maximum target elevation and acceptable tolerance for marsh
habitat mounds, the intent is that the surface area and shape of these features will vary
significantly across the project site. This variability will allow these features to blend into the
surrounding marsh, thus providing a more naturalistic appearance and decreasing the risk of nest
predation by avoiding repetitive, artificial shapes that could attract predators.
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4.6 SITE STABILIZATION
During construction, it is anticipated that the contractor will make reasonable efforts to minimize
the impacts and damage to the existing vegetation and marsh surface and that they will install
erosion and sedimentation controls as described in the section above. Trees along the upland
access points and marsh edge will be protected to the maximum extent practicable. To avoid
runoff from leaks or spills, the contractor will be responsible for providing the engineer and
owner with a spill prevention and response plan prior to the start of work.
Following construction, the contractor will be responsible for restoring the site and replacing any
areas damaged during construction. Areas damaged during construction will be reseeded using
an appropriate native seed mixture and/or otherwise restored to their original condition.
5. IMPACT AVOIDANCE AND MINIMIZATION MEASURES
In addition to the erosion and sedimentation controls discussed above, specific impact avoidance
and minimization measures will be necessary to ensure that implementation of the proposed
restoration work does not adversely impact saltmarsh sparrow or other sensitive species within
the marsh. The primary method proposed to avoid impacts to breeding saltmarsh sparrows is to
conduct the proposed work outside of the critical period for nesting (May to August). As ditch
remediation relies on mowing salt hay, this work would likely occur in late summer following
the completion of the annual breeding cycle. Runneling and marsh mound creation would occur
outside the growing season, generally between October and March. Impacts to potentially
suitable saltmarsh sparrow nesting habitat will be minimized in the implementation of ditch
remediation by limiting the width of the mowed swath adjacent to each ditch to no more than 20
feet on either side of the ditch.
To protect existing marsh, heavy equipment will only be operated on the marsh during neap tide
cycles. As noted in Section 4.2, all equipment shall be low-pressure, and if needed, the contractor
may use marsh protection when moving equipment on the marsh over soft and wet areas with
approval from Mass Audubon and the Engineer. Additionally, to prevent the introduction of
invasive species, marsh habitat mound elevations have been designed not to exceed the highest
elevation of high marsh within the project area.
As the project site is located within mapped Priority and Estimated Habitats of state-listed
species, regulatory approval from the Massachusetts Natural Heritage and Endangered Species
Program (NHESP) will be required. Future coordination with NHESP should assist in
determining whether additional measures are necessary to ensure the protection of rare,
threatened, or endangered species during project implementation.
6. CONSTRUCTION COST ESTIMATE
An opinion of probable cost was developed for implementation of the proposed project. It is
noted that the costs provided herein are based on reference material, including RSMeans Heavy
Construction Cost Data, past similar construction projects, and weighted average unit prices. The
preparer of these costs has no control over the future availability of labor, equipment, materials,
Page 13
EA Engineering, Science, and Technology, Inc., PBC June 26, 2025
Barnstable Great Marsh Wildlife Sanctuary Technical Memorandum for
Barnstable, Massachusetts Design Narrative for Barnstable Great Marsh Restoration Project
market conditions, and other unforeseen circumstances. The construction cost estimate is
included as Attachment E.
7. REFERENCES
Bolduc, F., and A.D. Afton. 2004. Relationships between wintering waterbirds and invertebrates,
sediments and hydrology of coastal marsh ponds. Waterbirds. 27(3): 333-341.
Correll, M., J. Watson, and B. Wilson. 2024. Coastal marsh restoration: an ecosystem approach
for the Mid-Atlantic. Jointly authored by National Oceanic and Atmospheric
Administration (NOAA), U.S. Fish and Wildlife Service (USFWS). acjv.org
Couvillion, B., Ganju, N.K., Defne, Z. 2022. An Unvegetated to Vegetated Ratio (UVVR) for
coastal wetlands of the Conterminous United States (2014-2018).
https://www.usgs.gov/data/unvegetated-vegetated-ratio-uvvr-coastal-wetlands-
conterminous-united-states-2014-2018. Accessed March 2025.
Ganju, N. K., Z. Defne, M. L. Kirwan, S. Fagherazzi, A. D’Alpaos, and L. Carniello. 2017.
Spatially integrative metrics reveal hidden vulnerability of microtidal salt marshes. Nature
Communications 8:14156.
Himmelstein, J., O.D. Vinent, S. Temmerman, and M.L. Kirwan, 2021. Mechanisms of pond
expansion in a rapidly submerging marsh. Frontiers in Marine Science. 8:704768.
Accessed March 2025.
Kutcher, T.E., K.B. Raposa, and C.T. Roman. 2022. A rapid method to assess salt marsh
condition and guide management decisions. Ecological Indicators. 138:108841.
MacKenzie, R. A., and M. Dionne. 2008. Habitat heterogeneity: importance of salt marsh pools
and high marsh surfaces to fish production in two Gulf of Maine salt marshes. Marine
Ecology Progress Series. 368:217–230. http://www.jstor.org/stable/24872761. Accessed
February 2025.
Massachusetts Department of Environmental Protection (MassDEP). 2003. Massachusetts
Erosion and Sediment Control Guidelines for Urban and Suburban Areas. Franklin,
Hampden, Hampshire Conservation Districts.
———. 2024. Wetlands Program Guidelines on Massachusetts Wetlands Protection Act and
Water Quality Certification Provisions Regarding Salt Marsh Restoration Techniques,
including Ditch Remediation, Runnels, and Marsh Habitat Mounds. DWW Guidelines
2024-01. Executive Office of Energy & Environmental Affairs, Boston, MA.18 June.
McKown, J. G., D.M. Burdick, G.E. Moore, C.R. Peter, A.R. Payne, and J.L. Gibson. 2023.
Runnels reverse mega-pool expansion and improve marsh resiliency in the Great Marsh,
Massachusetts (USA). Wetlands. 43(4): 35. Accessed February 2025.
Page 14
EA Engineering, Science, and Technology, Inc., PBC June 26, 2025
Barnstable Great Marsh Wildlife Sanctuary Technical Memorandum for
Barnstable, Massachusetts Design Narrative for Barnstable Great Marsh Restoration Project
Mora, J., Fitzgerald, E., Autery, A., Association to Preserve Cape Cod. 2024. Barnstable Great
Marsh 2024 Pre-Restoration Salt Marsh Monitoring.
Smith, K. J., and K.W. Able. 1994. Salt-Marsh Tide Pools as Winter Refuges for the
Mummichog, Fundulus heteroclitus, in New Jersey. Estuaries. 17(1):226–234.
https://doi.org/10.2307/1352572. Accessed February 2025.
Sripanomyom, S., P.D. Round, T. Savini, Y. Trisurat, and G.A. Gale. 2011. Traditional salt-pans
hold major concentrations of overwintering shorebirds in Southeast Asia. Biological
Conservation. 144(1): 526-537.
Sweet, W.V., B.D. Hamlington, R.E. Kopp, C.P. Weaver, P.L. Barnard, D. Bekaert, W. Brooks,
M. Craghan, G. Dusek, T. Frederikse, G. Garner, A.S. Genz, J.P. Krasting, E. Larour, D.
Marcy, J.J. Marra, J. Obeysekera, M. Osler, M. Pendleton, D. Roman, L. Schmied, W.
Veatch, K.D. White, and C. Zuzak. 2022. Global and Regional Sea Level Rise Scenarios
for the United States: Updated Mean Projections and Extreme Water Level Probabilities
Along U.S. Coastlines. NOAA Technical Report NOS 01. National Oceanic and
Atmospheric Administration, National Ocean Service, Silver Spring, Maryland. 111 pp.
https://oceanservice.noaa.gov/hazards/sealevelrise/noaa-nos-techrpt01-global-regional-
SLR-scenarios-US.pdf
Figures
Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 3/3/2025 | omihokI02000
Feet
Legend
Project Boundary (76.7 acres)
Figure 1
Site Locus
Mass Audubon
Barnstable Great
Marsh Restoration
Barnstable, Massachusetts
Sources: ESRI 2025
ShepherdsWayHinckley
Pond
Main StScudder LnPath: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 6/20/2025 | jmorrisseyI0500
Feet
Legend
Project Boundary
Tide Sheds
Mean High Water (4.32 ft NAVD88)
Tidal Channel Network
Figure 2
Tide Sheds
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023, NOAA 2021, USGS CMUs 2022
ShepherdsWayHinckley
Pond
Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 6/20/2025 | jmorrisseyI0500
Feet
Legend
Project Boundary
Tide Sheds
Pannes and Pools
Figure 3
Pannes and Pools
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023, NOAA 2021, USGS CMUs 2022
Hinckley
Pond
Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 5/8/2025 | omihokI0500
Feet
Legend
Project Boundary
USGS Unvegetated to Vegetated Ratio
≤ 0.001
≤ 0.025
≤ 0.05
≤ 0.1
≤ 0.15
≤ 0.25
≤ 0.5
≤ 1.0
≤ 1.5
1.5 - 2
> 2
Figure 4
Unvegetated to Vegetated
Ratio
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023, USGS 2023
Hinckley
Pond
Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 5/8/2025 | omihokI0500
Feet
Legend
Project Boundary
< MSL
MSL to MHW
MHW to MHHW
MHHW to HAT
> HAT
Figure 5
Tidal Inundation Zones
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023, NOAA 2021
Datum Elevation (ft, NAVD88)
MSL -0.30
MHW 4.32
MHHW 4.77
HAT 6.8
Elevations from NOAA Boston
Gauge Station
ShepherdsWayHinckley
Pond
Transect A
(1808 feet)
Transect B
(2239 feet)
Transect C
(1235 feet)
Transect D
(986 feet)
Transect E
(1197 feet)Transect F
(761 feet)Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 6/20/2025 | jmorrisseyI0500
Feet
Legend
Project Boundary
Tide Sheds
Survey Transects
Tidal Channel Network
Figure 6
Survey Transects
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023, USGS CMUs 2022
Hinckley
Pond
Transect A
(1808 feet)
Transect B
(2239 feet)
Transect C
(1235 feet)
Transect D
(986 feet)
Transect E
(1197 feet)Transect F
(761 feet)Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 5/8/2025 | omihokI0500
Feet
Legend
Project Boundary
Marsh Community Type
Creek
Ditch
High Marsh
Low Marsh
Panne
Pool
Unvegetated
Phragmites
Figure 7
Field Evaluated Vegetative
Communities
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023
ShepherdsWayHinckley
Pond
Transect A
(1808 feet)
Transect B
(2239 feet)
Transect C
(1235 feet)
Transect D
(986 feet)
Transect E
(1197 feet)Transect F
(761 feet)Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 6/20/2025 | jmorrisseyI0500
Feet
Legend
Project Boundary
Tide Sheds
Tidal Channel Network
Survey Transects
High Density of Crab Burrows
Figure 8
Crab Burrow Density
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023, USGS CMUs 2022
ShepherdsWayHinckley
Pond
Transect A
(1808 feet)
Transect B
(2239 feet)
Transect C
(1235 feet)
Transect D
(986 feet)
Transect E
(1197 feet)Transect F
(761 feet)Path: \\warwickfp\Warwickfp\GIS_Warwick\StateandLocal\Northeast\Massachusetts\1653701_BarnstableGreatMarsh\PROJECTS\1653701_BarnstableGreatMarshRestoration\1653701_BarnstableGreatMarshRestoration.aprx | 6/20/2025 | jmorrisseyI0500
Feet
Legend
Project Boundary
Tide Sheds
Survey Transects
Pannes and Pools Visited in the Field not Identified in Desktop Mapping
Inspected Pannes and Pools
Figure 9
Inspected Pannes and
Pools
Mass Audubon Barnstable
Great Marsh Restoration
Barnstable, Massachusetts
Sources: MassGIS 2023, USGS CMUs 2022
Attachment A
Survey Benchmark Documentation
Z:\2025\25103 EA ‐ BM Barnstable\Bench Mark Data\BM 2025.docx
BENCHMARK EXHIBIT
MASS AUDUBON’S
BARNSTABLE GREAT MARSH WILDLIFE SANCTUARY
BARNSTABLE, MA
ALPHA SURVEY GROUP, LLC
Job # 25103
Designation N/A
Elevation 41.06 FT (12.515 M) – SEE NOTE #2
Datum NAVD88 (GEOID18)
Description DRILL HOLE SET IN STONE
Location 2444 MAIN STREET – BARNSTABLE, MA
Date Set MARCH 27, 2025
Field JORGE DESOUSA, PAUL PIERSON, BRODY RICHARDS
Northing 2718728.46 (2001 MA US FT) – 828670.092 SPC (2001 MA M)
Easting 976174.45 (2001 MA US FT) – 297538.567 SPC (2001 MA M)
NOTES:
1.) THE ABOVE COORDINATES (NORTHING & EASTING) ARE BASED ON REDUNDANT GPS (RTK)
OBSERVATIONS UTILIZING A CARLSON BRX7 GPS RECIEVER.
2.) THE ABOVE ELEVATION IS BASED ON A CLOSED LOOP LEVEL RUN FROM OPUS POINT #1 AS SHOWN ON
THE ATTACHED OPUS SOLUTION, FIELD DATA COLLECTED 3/27/2025. METRIC VALUES WERE
CONVERTED TO U.S. SURVEY FEET USING A CONVERSION FACTOR OF 1 METER = 3.280833333 FT.
Reference is made to the following informaƟon:
hƩps://www.ngs.noaa.gov/OPUS/about.jsp#accuracy
Z:\2025\25103 EA ‐ BM Barnstable\Bench Mark Data\BM 2025.docx
NGS OPUS SOLUTION REPORT (POINT #1)
========================
All computed coordinate accuracies are listed as peak‐to‐peak values.
For addiƟonal informaƟon: hƩps://www.ngs.noaa.gov/OPUS/about.jsp#accuracy
USER: jorge.desousa@alphals.com DATE: April 11, 2025
RINEX FILE: 2510086n.25o TIME: 13:57:56 UTC
SOFTWARE: page5 2008.25 master241.pl 160321 START: 2025/03/27 13:05:00
EPHEMERIS: igs23594.eph [precise] STOP: 2025/03/27 19:06:00
NAV FILE: brdc0860.25n OBS USED: 11460 / 13344 : 86%
ANT NAME: HEMA631 NONE # FIXED AMB: 73 / 79 : 92%
ARP HEIGHT: 1.393 OVERALL RMS: 0.016(m)
REF FRAME: NAD_83(2011)(EPOCH:2010.0000) ITRF2014 (EPOCH:2025.2347)
X: 1605513.562(m) 0.019(m) 1605512.551(m) 0.019(m)
Y: ‐4490743.487(m) 0.021(m) ‐4490742.059(m) 0.021(m)
Z: 4220890.937(m) 0.010(m) 4220890.962(m) 0.010(m)
LAT: 41 42 5.10822 0.018(m) 41 42 5.14519 0.018(m)
E LON: 289 40 22.05538 0.010(m) 289 40 22.03500 0.010(m)
W LON: 70 19 37.94462 0.010(m) 70 19 37.96500 0.010(m)
EL HGT: ‐14.879(m) 0.025(m) ‐16.121(m) 0.025(m)
ORTHO HGT: 13.216(m) 0.059(m) [NAVD88 (Computed using GEOID18)]
UTM COORDINATES STATE PLANE COORDINATES
UTM (Zone 19) SPC (2001 MA M)
Northing (Y) [meters] 4617476.914 828577.405
EasƟng (X) [meters] 389570.398 297616.859
Convergence [degrees] ‐0.88301111 0.78780000
Point Scale 0.99975006 1.00000227
Combined Factor 0.99975239 1.00000460
US NATIONAL GRID DESIGNATOR: 19TCG8957017477(NAD 83)
BASE STATIONS USED
PID DESIGNATION LATITUDE LONGITUDE DISTANCE(m)
DR1358 MACM MACM CHATHAM CORS ARP N414128.688 W0695801.532 29998.1
DS1980 MAMV MAMV MARTHASVINRD CORS GRP N412100.414 W0704549.650 53386.1
DO9475 MATU TRURO CORS ARP N415851.708 W0700236.891 38979.8
NEAREST NGS PUBLISHED CONTROL POINT
LW4011 BARNSTABLE 1846 N414148.607 W0701823.767 1789.1
This posiƟon and the above vector components were computed without any knowledge by the NaƟonal
GeodeƟc Survey regarding the equipment or field operaƟng procedures used.
Attachment B
Field Equipment Specifications
Attachment C
Photographic Log
Photograph No. 2:
Marsh platform during low tide taken near upland edge.
Photograph No. 1:
View of Barnstable Great Marsh from Mass Audubon's
observation deck.
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photograph No. 4:
Phragmites patch on upland edge of Transect B.
Photograph No. 3:
Marsh platform during high tide taken near upland edge.
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photograph No. 6:
Marsh ditch feature during high tide.
Photograph No. 5:
Marsh ditch feature during low tide.
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photograph No. 8:
Marsh channel feature during high tide.
Photograph No. 7:
Marsh channel feature during low tide.
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photograph No. 10:
Marsh panne feature during high tide.
Photograph No. 9:
Marsh panne feature during low tide.
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photograph No. 12:
Newly formed marsh pool features located on marsh platform.
Photograph No. 11:
Marsh pool feature during high tide.
Photograph No. 14:
Evidence of crab burrow density on the marsh platform edge of
the main channel.
Photograph No. 13:
Degradation of marsh platform on the edge of the main channel.
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photographic Log
Barnstable Great Marsh
Barnstable, Massachusetts
Date of Photographs: April 22, 23, & 24, 2025
Photo No.Latitude Longitude
1 41.702861 -70.331506
2 41.706672 -70.335258
3 41.704578 -70.330169
4 41.702611 -70.332717
5 41.704900 -70.334672
6 41.706825 -70.328081
7 41.706569 -70.335503
8 41.704822 -70.331756
9 41.705053 -70.332328
10 41.705106 -70.329167
11 41.707919 -70.335817
12 41.705294 -70.329003
13 41.707386 -70.330200
14 41.706589 -70.331047
Photograph Coordinates
Attachment D
Panne and Pool Summary Data
Pools and
Pannes ID
Approximate
Depth (ft)
Approximate
Diameter (ft)
Vegetation
Cover
Class
Northing (MA
State Plane ft)
Easting (MA
State Plane ft)
Proposed
Runnel
Papo-103 1.5 6.0 3 2719548.578 974551.124 Y
Papo-107 2.0 7.3 3 2719612.289 974520.222
Papo-125 2.0 18.8 3 2719614.679 974925.751 Y
Papo-126 2.5 11.1 3 2719643.146 974913.831
Papo-129 1.8 16.2 3 2719731.928 975025.066 Y
Papo-130 2.6 9.4 3 2719766.364 974984.096
Papo-133 2.3 26.0 3 2719827.333 974992.312
Papo-140 2.0 10.8 3 2719971.313 974966.579
Papo-142 1.6 20.6 3 2719919.614 974815.817
Papo-143 3.5 22.7 3 2719977.538 974752.469
Papo-144 2.3 26.0 3 2720019.417 974861.595
Papo-151 5.0 29.3 3 2720085.441 974844.577
Papo-153 2.2 12.5 3 2720040.921 974768.644 Y
Papo-154 1.2 16.5 3 2720029.152 974746.471
Papo-155 1.3 6.5 3 2720129.317 974772.786
Papo-156 2.3 19.7 3 2720153.694 974783.36
Papo-157 2.2 7.7 3 2720214.315 974796.99
Papo-158 2.0 12.0 3 2720175.05 974797.256
Papo-16 1.0 8.7 3 2720761.558 974039.142
Papo-160 4.0 57.1 3 2720216.406 974980.675 Y
Papo-161 2.5 17.0 3 2720311.321 974979.445
Papo-162 3.0 16.0 3 2720359.425 974916.667
Papo-163 1.5 22.7 3 2720281.422 974742.339
Papo-164 1.0 9.0 3 2720163.085 974704.949 Y
Papo-165 1.8 53.7 3 2720225.064 974697.497
Papo-166 2.3 32.2 3 2720236.127 974721.3
Papo-167 2.5 32.7 3 2720261.759 974684.924
Papo-173 5.0 27.2 3 2720316.546 974714.359
Papo-174 1.3 19.3 3 2720283.066 974771.682
Papo-175 1.5 7.8 2 2720430.871 974879.068
Papo-178 2.5 14.1 3 2720354.996 974561.201
Papo-179 1.2 14.4 3 2720448.022 974575.655
Papo-180 2.5 11.1 3 2720477.497 974585.501
Papo-19 0.8 13.3 3 2720690.017 974013.321
Papo-194 1.2 8.0 3 2720684.343 974455.751
Papo-195 0.3 7.4 3 2720744.188 974442.317
Papo-199 1.1 5.3 3 2720835.091 974385.26
Papo-204 3.3 19.0 3 2720301.482 975194.872
Papo-205 1.8 8.9 3 2720291.186 975131.505
Papo-206 2.5 27.5 3 2720286.011 975481.46
Pools and
Pannes ID
Approximate
Depth (ft)
Approximate
Diameter (ft)
Vegetation
Cover
Class
Northing (MA
State Plane ft)
Easting (MA
State Plane ft)
Proposed
Runnel
Papo-207 2.0 34.3 3 2720163.934 975255.968
Papo-208 5.0 26.7 3 2720140.167 975335.831
Papo-209 5.0 21.7 3 2720142.536 975311.692
Papo-21 2.5 23.0 3 2720659.551 974075.661
Papo-210 2.5 24.2 3 2720124.643 975308.933
Papo-211 4.0 23.8 3 2720104.065 975266.3
Papo-212 1.7 21.7 3 2720094.163 975310.718
Papo-213 2.3 15.8 3 2720076.957 975289.307
Papo-214 1.5 15.3 3 2720050.749 975298.101
Papo-215 1.8 8.8 3 2720006.507 975293.192
Papo-216 1.2 23.5 2 2720151.283 975474.466
Papo-217 1.5 12.5 3 2720139.064 975497.962
Papo-218 2.2 10.8 3 2720089.408 975513.893
Papo-219 1.8 12.2 3 2720127.573 975575.015
Papo-220 1.0 4.5 2 2720084.471 975591.514
Papo-221 1.0 11.4 3 2720115.502 975647.976
Papo-222 2.6 21.3 3 2720000.252 975682.354
Papo-223 2.8 12.3 3 2720021.858 975706.485
Papo-224 1.7 32.0 1 2720093.547 975769.572
Papo-226 2.7 23.3 3 2719950.781 975594.682
Papo-227 1.9 23.3 3 2720108.497 975805.608
Papo-229 1.7 9.6 3 2720023.993 975775.995
Papo-230 1.3 8.6 3 2720034.956 975809.36
Papo-232 1.1 6.5 3 2719964.187 975872.854
Papo-233 1.5 11.3 3 2719979.098 975915.35
Papo-234 1.2 6.3 3 2719924.747 975903.29
Papo-235 1.3 16.8 3 2719938.311 975948.053
Papo-237 1.0 12.0 3 2719833.374 975937.992
Papo-238 1.3 19.2 3 2719819.197 975917.456
Papo-239 3.0 33.8 3 2719784.385 975835.569
Papo-240 1.0 11.0 3 2719827.579 975783.342
Papo-241 0.7 6.5 3 2719838.905 975798.57
Papo-243 1.5 14.7 3 2719837.781 975722.427
Papo-244 2.3 17.5 3 2719931.385 975684.306
Papo-245 1.7 13.0 3 2719779.874 975648.533
Papo-25 2.7 18.3 3 2720627.389 974097.212
Papo-250 2.7 20.4 3 2719732.926 975474.208
Papo-253 2.5 16.7 3 2719821.165 975435.583
Papo-254 1.2 15.8 3 2719883.761 975410.889
Papo-255 2.9 18.3 3 2719845.738 975383.739
Pools and
Pannes ID
Approximate
Depth (ft)
Approximate
Diameter (ft)
Vegetation
Cover
Class
Northing (MA
State Plane ft)
Easting (MA
State Plane ft)
Proposed
Runnel
Papo-256 1.0 11.9 3 2719939.291 975393.65
Papo-258 1.3 18.0 3 2719872.282 975272.106
Papo-259 0.8 29.8 3 2719855.312 975306.693
Papo-260 1.7 21.0 3 2719927.221 975304.729
Papo-261 3.8 21.3 3 2719957.802 975298.109
Papo-275 2.2 12.2 1 2720546.035 975595.732
Papo-276 2.0 27.7 3 2720520.571 975671.496
Papo282 3.0 18.6 3 2720484 975762.279
Papo-287 1.7 8.3 3 2720416.704 975871.556
Papo-288 3.0 23.3 3 2720351.336 975894.613
Papo-289 5.0 82.0 3 2720291.216 975903.157
Papo-29 2.8 16.7 3 2720587.202 974123.966
Papo-291 4.0 23.0 3 2720202.081 976001.67
Papo-292 3.0 26.0 3 2720253.694 976020.255
Papo-298 1.3 7.1 3 2720435.818 976047.393
Papo-299 1.2 13.3 3 2720482.207 976021.503
Papo-30 1.2 9.2 3 2720532.525 976007.452
Papo-300 3.0 55.7 3 2720469.868 976051.022
Papo-301 2.0 18.8 3 2720516.975 974083.396
Papo-302 1.8 11.5 3 2720368.565 976073.885
Papo-303 3.0 59.9 3 2720423.153 976091.828 Y
Papo-304 2.2 27.8 3 2720338.938 976101.027
Papo-305 2.5 9.5 3 2720443.185 976108.503 Y
Papo-306 4.0 30.5 3 2720550.752 976125.961
Papo-307 4.0 37.8 3 2720482.005 976155.805
Papo-308 2.0 16.6 3 2720472.622 976228.989
Papo-309 4.0 26.8 3 2720443.983 976177.933
Papo-31 1.1 16.2 3 2720502.843 974094.829
Papo-310 4.0 36.5 3 2720329.616 976218.433
Papo-311 1.3 8.6 3 2720255.081 976295.363
Papo-312 1.8 15.5 3 2720271.431 976308.783
Papo-314 3.0 14.0 3 2720085.661 976188.651
Papo-39 2.0 10.8 3 2720507.946 974208.596
Papo-47 1.4 13.8 3 2720337.267 974152.652
Papo-48 1.2 4.3 3 2720267.171 974119.04
papo-67 2.5 21.4 3 2719866.783 974547.079
Papo-68 1.7 14.6 3 2720014.926 974385.559 Y
Papo-7 1.5 16.8 3 2720794.619 973970.947
Papo-72 2.8 48.0 3 2719906.835 974426.07
Papo-73 1.0 8.5 3 2720046.738 974303.824
Pools and
Pannes ID
Approximate
Depth (ft)
Approximate
Diameter (ft)
Vegetation
Cover
Class
Northing (MA
State Plane ft)
Easting (MA
State Plane ft)
Proposed
Runnel
Papo-74 1.7 13.5 3 2720034.848 974321.263
Papo-8 0.7 13.8 3 2720776.635 973987.836
Papo-new-1 1.2 2.8 3 2720519.223 974105.811
Papo-new-10 2.5 6.3 3 2720296.253 975353.932
Papo-new-11 1.3 9.4 3 2719789.69 975006.284
Papo-new-12 0.8 5.1 3 2719554.952 975034.738
Papo-new-13 3.0 1.5 3 2719281.205 975173.811
Papo-new-14 1.3 4.5 3 2720112.224 975553.133
Papo-new-15 0.8 4.0 3 2720119.069 975557.883
Papo-new-16 0.7 2.4 2 2720116.116 975626.506
Papo-new-17 1.2 10.3 3 2720133.11 975661.59
Papo-new-18 0.6 2.5 3 2720093.981 975652.75
Papo-new-19 0.8 6.0 2 2720006.442 975666.941
Papo-new-2 0.7 3.4 3 2720002.719 974386.593
Papo-new-20 0.8 7.0 3 2720031.66 975685.862
Papo-new-21 2.7 10.6 2 2720048.659 975694.366
Papo-new-22 0.8 6.3 3 2719870.23 975291.17
Papo-new-23 0.6 4.9 3 2719818.408 975365.749
Papo-new-24 6.0 52.8 3 2720190.722 975822.537
Papo-new-25 2.0 26.7 2 2719932.518 975756.142
Papo-new-26 0.5 4.0 2 2719825.125 975926.987
Papo-new-27 0.8 8.3 3 2719863.733 975899.816
Papo-new-28 0.9 2.5 3 2719927.658 975910.862
Papo-new-29 1.2 7.0 3 2720545.647 976053.88
Papo-new-3 0.7 5.0 2 2719163.572 975206.077
Papo-new-30 0.5 5.4 3 2720468.312 976021.904
Papo-new-31 0.8 5.5 3 2720463.747 976043.297
Papo-new-32 3.0 7.0 3 2720429.061 976069.842
Papo-new-33 0.8 12.6 3 2720378.54 976094.786
Papo-new-34 2.1 14.5 3 2720590.562 976127.252
Papo-new-35 1.8 2.9 3 2720546.28 976109.113
Papo-new-36 1.5 1.7 3 2720542.815 976108.111
Papo-new-37 2.5 14.5 3 2720529.444 976160.231
Papo-new-38 0.6 2.3 3 2720520.726 976162.375
Papo-new-39 0.7 3.9 3 2720519.686 976165.844
Papo-new-4 1.0 4.2 3 2720647.481 974437.702 Y
Papo-new-40 0.6 3.5 3 2720516.492 976164.936
Papo-new-41 0.6 1.9 3 2720513.772 976167.971
Papo-new-42 1.7 8.8 3 2720504.07 976144.508
Papo-new-43 0.8 5.5 3 2720495.532 976183.567
Pools and
Pannes ID
Approximate
Depth (ft)
Approximate
Diameter (ft)
Vegetation
Cover
Class
Northing (MA
State Plane ft)
Easting (MA
State Plane ft)
Proposed
Runnel
Papo-new-44 0.4 5.8 3 2720473.295 976202.191
Papo-new-45 0.8 6.0 3 2720411.482 976193.603
Papo-new-46 1.0 6.0 3 2720323.684 976285.443
Papo-new-47 0.8 8.0 3 2720240.481 976319.306
Papo-new-48 1.8 3.3 3 2720678.53 975699.395
Papo-new-49 2.2 20.0 3 2720650.185 975710.25
Papo-new-5 0.8 6.8 3 2720364.244 974856.897
Papo-new-50 4.0 41.5 3 2720579.651 975695.547
Papo-new-51 1.5 5.5 3 2720509.083 975716.723
Papo-new-52 4.0 51.0 3 2720356.004 975793.548 Y
Papo-new-53 0.8 5.3 3 2720250.417 976078.787
Papo-new-6 1.7 5.1 3 2720302.626 974759.423 Y
Papo-new-7 3.3 26.4 3 2720302.882 975004.406
Papo-new-8 2.5 17.8 3 2720258.737 975026.635
Papo-new-9 2.8 14.5 3 2720213.445 975024.441
Attachment E
Construction Cost Estimate
EA Engineering, Science, and Technology Inc., PBC EA Project No. 16512-01
Pre-Final Cost Estimate
May 10, 2025
0001 Mobilization and Demobilization 1 LS $57,240 $57,240
0002 Erosion and Sediment Control Measures 1 LS $350.09 $350
0003 Proposed Ditch Remediation 45,222 LF $2.53 $114,604
0004 Proposed Runnel and Marsh Habitat Mound Creation 3,384 LF $33.69 $114,006
$286,300
25% -$71,600
$357,900
$ Total CostUnit Price
Construction Cost Estimate
Massachusetts Audubon Society
Barnstable Great Marsh - Saltmarsh Restoration Project
EA Project No. 16537-01-00
CONSTRUCTION TOTAL WITH CONTINGENCY
CONSTRUCTION TOTAL
Estimated
Quantity Unit
Contingency
Payment Item
Number Description
1 OF 1
26
Appendix 4: SMARTeam Design Steps
The conceptual design of this project was developed by Geoff Wilson of NWR, in coordination with
MassAudubon and the Salt Marsh Adaptation and Resliency Team (“SMARTeam”) which includes various
federal and state agencies representatives and academic partners as well as private and non-profit
marsh managers. The final design was adopted by Mass Audubon’s coastal management staff, in
consultation with other regional salt marsh scientists with extensive marsh restoration experience
within East Coast marshes.
The design approach is intended to restore primary marsh hydrology within a mosaic marsh platform at
varying stages in the secondary succession process (secondary to the initial disturbance from agricultural
use). This fractured mosaic within each sub-tideshed to be restored has disrupted the parallel trajectory
between sea level elevation and marsh platform elevation. In a “healthy” system, the elevation
trajectory of the marsh platform should correlate positively with SLR. The design addresses each
secondary successional stage within the mosaic with appropriate restoration techniques to stabilize
marsh platform hydrology that restores connectivity of each sub-tideshed.
The SMARTeam has developed the following tiered design process for sites which have been altered by
past agricultural practices and show signs of subsidence, which includes virtually all areas of salt marsh
in New England. This process has evolved and adapted from earlier designs, based on monitoring data
from previous projects in Massachusetts, Maine and New Hampshire. Figures 1-5 below describe the
SMARTeam Tiered Design Process.
FIGURE 1. DESIGN STEP 1 – 1938 AERIAL OF PINE ISLAND SOUTH, NEWBURY, SHOWING LEGACY INFRASTRUCTURE
Step 1 Preliminary Site Investigation
Step 1 in the SMARTeam Tiered Design Process is to conduct a thorough preliminary site investigation
which includes compiling collateral data including but not limited to, current and historic land-use
practices, current and historic imagery, and current and historic monitoring information.
27
Step 2 Vegetation Delineation
Step 2 is to prepare baseline vegetation maps of the dominant plant communities as defined by growing
conditions. Understanding of vegetation patterns is important for monitoring the success of treatment
measures, since changes in species composition is a good indicator of altered hydrologic conditions.
Vegetative monitoring before and following restoration can capture and evaluate vegetation changes
that may be attributable to the restoration measures.
Step 3 Inventory Land-Use Infrastructure through Current and Historic Aerial Imagery
This step involves evaluating available imagery acquired in Step 1 to identify historical land-use
infrastructure. Historic land use forms the backbone of the design process as it is the driver for current
subsidence and vegetation patterns. Many times, the current legacy effects of the historic land-use are
the unseen drivers for site hydrology and plant community composition. In the image below, the
location of historic embankments is shown in red. The location of historic ditches is also mapped during
this step (see Step 4). It is helpful to have a good background in historic agricultural practices to be able
to identify and appreciate the significance of these features. Good references on early agricultural
practices include Fessenden, T.G. and Sheppard, T.W. (1823) and Clift, W (1862).
It is recommended that the oldest and highest quality available imagery is used to identify historical
land-use infrastructure as some features might be obscured by the current site conditions. These
images also offer an opportunity to compare vegetation patterns with current conditions.
28
FIGURE 3 DESIGN STEP 3 -EMBANKMENTS IDENTIFIED FROM FIELD INVESTIGATION AND AERIAL PHOTOGRAPHS
Step 4 Field Verification
The next step is to field-verify all sources of collateral data, vegetation delineations and historical land-
use infrastructure, as well as to observe the current tidal regime. Observations of current tidal regime
should be performed multiple times during different tidal periods including extreme flood tide and neap
tide periods during both the growing and non-growing seasons for an accurate identification of primary
and secondary hydrology and indicators of salt marsh secondary succession trajectory such as areas of
subsidence for all locations within the project area. Observation of tidal regime includes direct
observation of flow within individual tidesheds to determine primary ditches and auxiliary ditch
hierarchy and in collecting baseline tidal elevations using data loggers can inform the design. Field
verification requires visual monitoring of multiple ditches at a time during a particular tide. While
channel hierarchy is typically observable in the field from observations during 1-2 tidal cycles, in some
areas where the existing channel networks have clogged in a uniform manner, the identification of
primary channels can be more difficult and will require multiple observations of flood and ebb patterns
at various locations within the tideshed. Correct identification of primary channels is often complicated
by unique ditching patterns, land use history, soil drainage conditions, upland influences and other
factors and requires extensive empirical knowledge of salt marsh hydrology in general and site-specific
conditions in particular as tidal flow may not follow a regular pattern. It should not be attempted by
unqualified individuals as restoration actions attempted with incorrect hydrology will lead to poor
restoration results.
Tideshed boundaries, like watershed boundaries, can be identified at various scales, with small sub-
basins contained within larger and larger basins. Functional tideshed boundaries will vary depending on
the height of the tide. During high flood tides, portions of these boundaries are obscured as the entire
marsh plain is flooded. This design is focused on re-establishing functional sub-tideshed boundaries
which are the areas of the marsh that flood and drain toward a primary or permanent channel, whether
existing or established by a runnel to recreate hydrologic equilibrium. These sub-tidesheds are often
bounded by low historic agricultural embankments, upland slopes, structures such as roads, or other
creeks or channels. Understanding how each tideshed functions will provide the basis for selection of
restoration techniques. One tool for delineating sub-tideshed boundaries remotely are the Conceptual
Marsh Units (CPUs) developed by USGS based upon digital elevation model Defne and Ganju (2018).
Note that there is sometimes a difference between remotely generated data and field delineation of
29
tidesheds. This generally occurs in areas that are experiencing advanced stages of water-logged
succession where subsidence may obscure sub-tideshed boundaries. In the event that field delineated
sub-tideshed boundaries differ from remote delineation methods, field observations should be
presumed to be more accurate. Where existing ditches cross these tidesheds, ditch remediation is used
to restore the tideshed divide.
Fig. 4 – Example of Conceptual Marsh Units developed by USGS
Step 5: Design Development
The project design incorporates all the data collected in steps 1-4. Once the vegetative communities are
mapped, historic land uses have been inventoried, individual sub-tideshed boundaries have been
identified, and primary tidal hydrology established, the areas of actual or potential subsidence can be
identified and the proposed management measures can be developed to minimize further subsidence.
It is important to identify within each proposed treatment area the primary subsidence driver. The
primary drivers addressed by this project are the Oxidation Subsidence Trajectory (OST) caused by
extensive ditching lowering the groundwater elevation or zone of saturation within the peat soil column
and the Waterlogged Subsidence Trajectory (WST) resulting in standing water or surface saturation
caused by the extended inundation of the marsh surface from clogged or altered drainage infrastructure
of past agricultural practices. Because both these conditions are caused by the infrastructure left behind
from past land-use activities, in some cases, there are areas of the marsh in proximity which are
experiencing both subsidence effects. One process is the result of over oxygenation and the other
results in over saturation (anerobic conditions), so the proposed treatment strategies differ, but both
attempt to restore similar hydrological conditions (see Figure 5). Within each area of subsidence, an
effort is also made to assess the stage of the WST a particular area of the marsh is experiencing (see
section __ for stages of Water-logged Subsidence Trajectory) so that restoration efforts can be
prioritized to maximize potential restoration.
Step 6: Categorizing runnels and ditch remediations
The SMARTeam design incorporates the use of runnels, which are shallow, often vegetated swales that
direct tidewater from remediating ditches and subsidence areas to adjacent open ditches. Runnels have
been employed by practitioners for a variety of purposes. For this project, they will be employed to
serve as primary channels within a subtideshed to address WST. The location of runnels is based upon
tideshed delineations (see Step 7 below) and current marsh inundation. Aerial signatures were field
verified by the design team (Geoff Wilson,) to establish consistent interpretation.
30
Similarly, ditches selected for remediation fall into two categories: those that are mainly open to flowing
water and are mostly unvegetated, and those already in the process of healing (revegetating) or
clogging. In the latter case, much of the ditch may have healed on its own, and only spot treatments of
cut hay are required to achieve desired results.
Step 7: Restoring primary tidal channel dendritic network and tidesheds
As described earlier, this project is based in part upon the concept of restoring tideshed equilibrium
where channel size and distribution is in balance with the marsh surface which it serves. While natural
processes may be expected to eventually fill the ditches and restore primary channel hydrology over
many decades or even centuries, the delay in restoration of hydrology occurs at the expense of
considerable additional subsidence and marsh loss, which the marsh cannot afford and still maintain
resiliency.
The proposed runnels and ditch remediation techniques work in concert to encourage restoration of a
channel network that is in equilibrium with the volume of flooding and ebbing tides that move through
each channel network. Where possible, the design proposes to restore a tiered dendritic channel
network so that smaller creeks (1st order) converge into medium sized creek (2nd order), which then
converge into primary creeks (3rd order). Note that the creek order is reversed from convention used by
freshwater creeks for ease of tracking. All proposed runnels in this design are 1st order creeks and will
be constructed to similar width and depth ranges. The creek order can influence the long-term runnel
dimensions based upon the volume of flow they ultimately convey, allowing natural channel forming
processes to fine tune the runnel size and shape. The design works within these tiered dendritic channel
networks and their associated sub-tidesheds.
9.0 Restoration Methods
Through previous projects completed, a deeper understanding of marsh restoration techniques and
their interactions with natural processes has been gained. The specific nature-based restoration
techniques included in this design are intended to operate in synergy to reestablish proper expression of
ecosystem processes, boost resilience to increased flooding, and establish a marsh-sustaining trajectory.
This Section describes restoration methods. Please refer to Concept Design Plans prepared by EA
included as an attachment for detailed design for the project area.
In general, the techniques serve to lower the zone of saturation in areas proposed to contain runnels to
improve growing conditions in the root zone and to raise it in areas proposed for ditch remediation to
eliminate excess oxidation of peat as indicated below in the figure provided by the SMARTeam.
FIG. 9.1: WHILE PAST HUMAN ALTERATIONS MANIFEST IN 2 DIFFERENT TYPES OF SUBSIDENCE TRAJECTORIES (WATERLOGGED
AND OXIDIZATION), RUNNELS AND DITCH REMEDIATION TECHNIQUES ARE BOTH TRYING TO RESTORE TO A SINGLE DENDRITIC
CHANNEL HYDROLOGY.