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MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Marstons Mills River Bogs Ecological
Restoration Project, Barnstable, MA
Basis of Design Report – 75% Completion, REVISED
SUBMITTED TO
Barnstable Clean Water Coalition
P.O. Box 215
Osterville, MA 02655
August 2025
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Table of Contents
1. Executive Summary ................................................................................................................... iv
2. Introduction ...............................................................................................................................1
2.1 Project Goals ................................................................................................................................. 1
2.2 Project Partners ............................................................................................................................ 2
3. Existing Conditions .....................................................................................................................3
3.1 Site Context ................................................................................................................................... 3
3.2 Cell Descriptions ............................................................................................................................ 6 Cells A, B, C and D .......................................................................................................... 6 Cell 1 (Big Coombs) ........................................................................................................ 8 Reservoirs 1 & 2 ............................................................................................................. 8 Cell 3 (Winnies) .............................................................................................................. 9 Cell 4 (Cook House) ...................................................................................................... 10 Cell 6 (Abandoned bog) ............................................................................................... 11
3.3 Sand and Peat Characterization .................................................................................................. 12
3.4 Wetlands and Ecology ................................................................................................................. 12
3.5 Water Quality .............................................................................................................................. 13 Nitrogen Attenuation .................................................................................................. 14 Permeable Reactive Barriers ....................................................................................... 15
3.6 Infrastructure and Utilities .......................................................................................................... 16
3.7 Recreation ................................................................................................................................... 16
3.8 Historical/Cultural Resources ...................................................................................................... 16
3.9 Site Constraints ........................................................................................................................... 17
3.10 Property Line Survey ................................................................................................................... 17
3.11 Surface water and Groundwater monitoring ............................................................................. 18
3.12 Surface water Hydrology Analyses ............................................................................................. 19 FEMA Mapping ............................................................................................................ 19 Locally-collected Streamflow Data .............................................................................. 21 Development of Flood Flow Estimates ........................................................................ 23
4. Surface Water Hydraulic Model ................................................................................................ 25
4.1 Terrain ......................................................................................................................................... 25
4.2 Computational domain ............................................................................................................... 25
4.3 Infrastructure .............................................................................................................................. 26
4.4 Boundary Conditions ................................................................................................................... 26
4.5 Roughness Coefficients ............................................................................................................... 27
4.6 Proposed Conditions – wetted area ........................................................................................... 27
4.7 proposed conditions – residence Time ....................................................................................... 30
5. Groundwater Hydraulic Model .................................................................................................. 31
5.1 Groundwater Model Construction .............................................................................................. 31
5.2 Groundwater Modeling analyses ................................................................................................ 32
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6. Project Design .......................................................................................................................... 34
6.1 Cells A, B, C, and D ...................................................................................................................... 34
6.2 Cell 1 ............................................................................................................................................ 35
6.3 Cell 3 ............................................................................................................................................ 36
6.4 Cell 4 ............................................................................................................................................ 36
6.5 Cell 6 ............................................................................................................................................ 37
6.6 Site-Wide Design Elements ......................................................................................................... 37 Topographic Complexity.............................................................................................. 37 Large Wood Slash Installation ..................................................................................... 38 Vegetation ................................................................................................................... 38 Recreation ................................................................................................................... 39
6.7 Water Quality considerations ..................................................................................................... 39 Permeable Reactive Barriers ....................................................................................... 39
6.8 Recommended Construction Sequence ...................................................................................... 45
7. Engineer’s Opinion of Probable Costs ........................................................................................ 46
8. References ............................................................................................................................... 47
Appendix A – 75% Preliminary Design Drawings ...................................................................................... A-1
Appendix B - Historical maps and aerial photographs ............................................................................... B-2
Appendix C - Site Information .................................................................................................................... C-3
Appendix D – Cranberry Bog Restoration and Management: Nutrient Removal Pilot Update within the
Hamblin Bog System (SMAST 2022) .......................................................................................................... D-4
Appendix E – Figures developed by Horsley Witten referenced in the Basis of Design Memo ................ E-5
Appendix F – HydroCAD Report for the Marstons Mills River at the outlet of the project area ............... F-6
Appendix G – Onsite Soil Investigation for Hamblin Bogs, Marstons Mills (USDA NRCS 2021) ............... G-7
Appendix H – RSI report regarding the GPR survey of Marstons Mills River Bogs (2021) ........................ H-8
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1. Executive Summary
The purpose of this report is to document the studies completed and describe the designs proposed
for the restoration of the Marstons Mills River Bogs in Marstons Mills, a village within the town of
Barnstable, Massachusetts. This Basis of Design Report (75% Complete Design, Revised) builds upon
the Hamblin Bogs Concept Designs prepared by Inter-Fluve in March 2022 and is a revision of the
75% Complete Basis of Design Memo submitted in June 2023 as the designs have since changed
substantially. In the sections below, we describe our understanding of the site conditions, review the
existing data, describe the methods for field studies completed, and describe the proposed restored
conditions that are informed by these findings. We summarize the design methodologies displayed
in the accompanying 75% drawings and discuss the estimate of construction costs associated with
the proposed restoration activities. This document is not meant to be used by the construction
contractor to construct the work. This document may be used, in whole or in part, to facilitate
regulatory review of the restoration project.
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2. Introduction
Located on Cape Cod in the village of Marstons Mills, the Marstons Mills River Bogs are a wetland
complex that have been heavily modified for over 100 years for commercial cranberry production
(Figure 1). The Barnstable Clean Water Coalition (BCWC) initiated the Marstons Mills River Bogs
Restoration Project (the Project) to restore 62 acres of cranberry bogs (the Site) to more naturally-
functioning streams and wetlands with the associated goal of reducing nitrogen levels, a widespread
issue impacting water quality throughout the region.
The bogs exhibit the typical legacy impacts of cranberry cultivation, including physical and
biological simplification, over-drainage by a network of ditches, an anthropogenic sand layer
overlying native wetland soils, along with flow barriers such as earthen berms and flow control
structures. These impacts have inhibited biodiversity, impaired fish passage, reduced nutrient
uptake and limited the resiliency of the system to the changes in climate experienced in this region.
The BCWC contracted Inter-Fluve, Horsley Witten, and the Mashpee Wampanoag Tribe (the Team)
to complete 75% designs, building upon the concept designs that Inter-Fluve completed in 2022. In
the fall of 2022 and spring of 2023, the Team conducted supplemental site assessments, hydrologic
and hydraulic analyses, and developed 75% engineering restoration designs. After June 2023,
opportunities arose to consider a design change that removed the proposed channel and includes
removal of sand placed during farming. Additional field data were collected in the spring of 2024 to
evaluate the sand and peat thicknesses in bog Cells A-D. This report synthesizes the data collection
efforts, describes the current site conditions, summarizes the hydrologic and hydraulic methods and
results, and describes the proposed restoration designs at the 75% design level.
2.1 PROJECT GOALS
The mission of BCWC is to ‘restore and preserve clean water.’ As retired cranberry bogs are being
restored to more naturally-functioning stream and wetland ecosystems throughout the region,
BCWC saw an opportunity to improve water quality and restore ecosystem functions at the
Marstons Mills River Bogs. BCWC, in collaboration with state and federal partners, developed the
following goals for this project:
• Healthy, self-sustaining, and dynamic wetlands;
• Improved hydrologic and aquatic habitat connectivity;
• Improved water quality (including reduced nitrogen export); and
• Passive recreation in permanently protected public open space.
Throughout the design process, the Team has used these goals to guide the designs through various
decision points. At times, it was necessary to weigh one goal over another; however, the Team has
developed a design that works to fulfill as many of these goals as possible.
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2.2 PROJECT PARTNERS
BCWC has partnered with the following organizations to complete this project: Massachusetts
Division of Ecological Restoration (DER), Natural Resources Conservation District (USDA NRCS),
The Nature Conservancy (TNC), the U.S. Environmental Protection Agency (EPA), and the current
farm property owners.
Figure 1. Marstons Mills River Bog Complex in Marstons Mills, MA. The river exits the Site to the southeast, flowing towards
Nantucket Sound. The solid blue line represents the centerline of the Marstons Mills River and the dotted red line represents
the boundaries of the cranberry bogs selected for restoration.
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3. Existing Conditions
3.1 SITE CONTEXT
While there is limited documentation of what the Project Site (the Site) looked like prior to its
agricultural use, a topographic map from the 1890s shows the Marstons Mills River beginning to
form within a wetland just upstream of what is now Bog Road and then meandering downstream
through wetlands and flowing into a small pond where it joined streams coming from Middle Pond
and Crocker Pond (Figure 2). The Mashpee Wampanoag Tribe and the Native Land Conservancy,
our design teaming partners during the current design phase and conceptual design phases
respectively, refer to the Marstons Mills area as the Cummaquid area. The Wampanoag people likely
called the project area Wompashq, meaning wetlands or marshy land. Wetlands were, and still are,
vital ecosystems for the Wampanoag people, whose livelihood revolved around foraging,
harvesting, building, hunting, and accessing clean water. They used springs as sources of drinking
water, foraged wild cranberries, hunted animals such as deer and raccoons, and harvested Atlantic
white cedar for use in building their homes and in ceremonies.
Farming at the Marstons Mills River Bogs likely began in the late 1800s or early 1900s. To convey
water more efficiently, the sinuous channel was straightened and widened. Lateral and perimeter
ditches were created to drain the wetland and move water around the bogs as the farmers needed.
Flow control structures were installed to manipulate flows for cranberry cultivation, harvesting
(flooding for the wet harvest), and frost protection (flooding over the winter). Subsequent channel
maintenance through the life of the farm included channel dredging. In addition, sand has been
placed incrementally on the underlying peatland surface to stimulate cranberry plant growth and
suppress weeds, resulting in a thickness of 1 to 3 feet of anthropogenic sand spread across the Site.
The earliest known aerial imagery is from 1938, which shows the land extensively developed into
cranberry bogs (Figure 3). While much of the Site currently appears similar to the conditions in 1938,
the area to the northwest of the Site, which was once cultivated for cranberry, has since been
abandoned. This abandoned area is now forested wetlands and is where the Marstons Mills River
begins.
Over the several decades, Cape Cod has seen a decline of the cranberry bog industry and an increase
in residential and commercial development. The population has increased, and with it, the demand
for housing and infrastructure. The surge of tourism has also resulted in the loss of undeveloped
land to hotels, restaurants, and shops. There is growing concern over the impact of development on
Cape Cod’s fragile ecosystem, particularly on the region's water quality.
The BCWC is working with the current farmers of the Marstons Mills River Bogs to restore and
conserve the land to improve water quality and create a resilient wetland ecosystem. For more
historical maps and aerial photographs see Appendix B.
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Figure 2. United States Geological Survey topographic map from the 1890's.
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Figure 3. Aerial photograph from 1938. The blue polygons indicate the areas of proposed restoration.
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3.2 CELL DESCRIPTIONS
The Site consists of nine former cranberry bog cells, with approximately 8,000 linear feet of river
channel flowing through them. The river channel enters the Site via a ditch from the wetlands in the
headwaters upstream of the Site boundaries. The channel remains ditched as it flows through the
bog complex. Refer to Figure 1 to locate the cells on the project map.
Cells A, B, C and D
Located upstream of Bog Road, Cells A through D encompass four bogs covering an area of
approximately 8 acres. The Marstons Mills River flows from the headwaters into Cell A (Figure 4). It
then flows northeast in a straightened ditch through Cells A, B, C, and D. At the downstream end of
Cell B, there is a small holding pond with an adjacent pump house for irrigation. The river leaves
Cell D and flows through a series of cranberry bogs that are actively farmed and outside the scope of
the project. The river then passes under Bog Road and continues through the rest of the Marstons
Mills River Bogs included in the Site. The bog surfaces of Cells A through D are relatively flat with
cranberries still present. Sphagnum moss grows within the ditches and poison ivy is prevalent. The
sand placed for farming is approximately 2 to 2.5 feet in thickness. Underlying peat ranges from 10
to 20 feet in thickness within the central portions of Cells A and B and the downstream area of Cell
D. Elsewhere, the peat is less than 10 feet thick and thins out at the edges of the bog cells. Earthen
berms separate the bog cells and associated water control structures delineate the flow between the
bog cells.
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Figure 4. Cell A looking downstream.
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Cell 1 (Big Coombs)
The first bog downstream of Bog Road is Cell 1, which consists of a primary bog and four smaller
bogs, each separated by a berm. The bog is actively farmed, and therefore, mostly covered in
cranberry mat, though poison ivy and other vegetation is beginning to grow. The sand thickness is
approximately 1 foot along the edges and 2 to 2.5 feet in the middle. Underlying the sand is peat,
which is thicker towards the center of Cell 1 and tapers off towards the edges. Sphagnum moss is
found through the bog surface and throughout the ditches. More native graminoids are found in the
wet areas along the northern edge of Cell 1. The main channel, featuring a few meander bends,
conveys the majority of flow, while lateral and perimeter ditches move water throughout the bogs
during the wetter times of the year. The channel and ditches intercept groundwater coming into Cell
1 primarily from the north and west. The channel bottom is sandy and soft. Flow control structures
are used to flood the bogs multiple times a year for harvesting and frost protection. The lack of
geomorphic complexity has resulted in limited aquatic habitat.
Figure 5. Main channel of Cell 1 looking downstream.
Reservoirs 1 & 2
Reservoirs 1 & 2 are used to store water so the farmers can irrigate and transfer water throughout
the bogs. These two ponds, which are separated by flow control structures, have a total surface area
of approximately 1 acre. The water depth in both reservoirs varies based on the season and farming
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practices, but is estimated to range from approximately 4 to 6 feet in depth. A pump, pumphouse,
and gas tank for each reservoir are located on the western edge of Reservoir 1 and the northeast
corner of Reservoir 2. The ponds contain aquatic vegetation and algae; saplings line the edge of the
southern reservoir; the invasive plant, Phragmites spp. or common reed, is present on the northern
edge of Reservoir 2.
Figure 6. Reservoirs 1 & 2 are separated by a berm and flow control structure. Note the invasive plant, Phragmites, in the
middle of the photo.
Cell 3 (Winnies)
Cell 3 is an active cranberry bog separated into two parts by an earthen berm, creating a smaller
eastern cell and a larger western cell. The vegetation primarily consists of cranberry mat with
Sphagnum spp. (sphagnum moss) in the ditches. The sand thickness is variable, with bog edges
having 1 to 1.5 feet, the interior having 2 to 2.5 feet, and the east side of the western cell having 3+
feet. The peat is deep throughout the larger western cell but minimal in the smaller eastern cell. The
main channel flows from the northeast to southwest with lateral and perimeter ditches contributing
flow. Additionally, there is a small irrigation pond connected to the channel on the south side with a
pump house.
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Figure 7. Looking northwest along the earthen berm separating the two parts of Cell 3. This photo was taken when the bogs
were flooded for frost protection during the winter.
Cell 4 (Cook House)
After leaving Cell 3, the main channel flows along the western edge of Cell 4 and is separated from
the rest of the cell by a berm. Cell 4 was retired from cranberry production more than a decade ago
due to it being too wet and too hard to maintain a level bog surface in the middle of the bog where
the sand sank into the underlying peat. A large pond has formed in the middle, approximately 3 feet
deep. While Cell 4’s appearance as a typical cranberry bog has been altered due to the wetness and
lack of farming, the perimeter and lateral ditches are still discernable. The vegetation present
consists of shrubs and a few samplings around the edges. In the wetter areas, there is a lot of
sphagnum moss and a variety of graminoids. The sand thickness is similar to the other bog cells,
around 1 to 2 feet. The peat thickness in the middle of the cell is 10 to 15 feet. There is also a flow
control structure to let water into the primary channel on the west side.
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Figure 8. Looking southeast at the pond in Cell 4.
Cell 6 (Abandoned bog)
Cell 6 was abandoned in the early 2000s and is currently inactive. The vegetation on the bog surface
consists mostly of pine saplings with a diameter at breast height of about 4 inches. The sand
thickness in this area is approximately 1 to 2 feet, and the underlying peat thickness is
approximately 3 feet. Drainage ditches are present around the perimeter of the bog cell. There are
also flow control structures in place to connect this bog to Reservoir 1.
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Figure 9. Pitch pine saplings growing in the abandoned bog. Looking north.
3.3 SAND AND PEAT CHARACTERIZATION
The Site and surrounding watershed consist of sand and gravel, with areas of variable depths of
organic peat that developed over thousands of years since ice blocks from the last ice age melted.
Following ice melt, residual depressional areas, or kettles, filled with water and eventually organic
material that developed into peat.
The Natural Resources Conservation Service (NRCS) conducted an onsite soil investigation in 2021
for the Site, collecting borings at nine locations using a spade and a 16-foot tile probe (Appendix G).
The surface conditions were characterized as a sanded surface over deep organic soil material, with
an average measured depth of sand of approximately 20 inches. The soils in the project area are
mapped as Freetown coarse sand, which is classified as very poorly drained organic material with 0
to 3 percent slopes and a sanded surface, identified by map symbol 55A. The thickness of the peat
layer ranged from 4 feet to 16 feet, with the deepest areas of peat found in the center of Cells 1 and 3.
All areas contained organic soil, indicating the historical presence of peatlands prior to the
construction of cranberry farms in the area.
A ground-penetrating radar survey conducted by Radar Solutions Inc. (RSI) confirmed similar
findings to the NRCS investigation (Appendix H). The survey found the sand thickness ranges from
1.5 to 2.5 feet on average, with a maximum thickness of 4 to 5 feet in the center of Cell 3. In some
locations, the peat is over 16 feet thick, with an intermediate layer that appears to have some sand
mixed with the peat.
3.4 WETLANDS AND ECOLOGY
The Marstons Mills River Bogs consist of wetlands that are classified as Cranberry Bog, Shrub
Swamp, Shallow Marsh Meadow, and Freshwater/Forested Shrub Wetland according to the
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MassDEP Wetlands Dataset 1. Although no state-listed plants or animals are present in the project
area, the USFWS Information for Planning and Conservation (IPaC) identifies the Northern long-
eared bat (Myotis septentrionalis), Monarch butterfly (Danaus plexippus), and American chaffseed
(Schwalbea americana) as federally-listed species of concern that may have suitable habitat in the area
(Appendix C). Herring currently migrate to Middle Pond through a fish ladder downstream of the
Site. Project partners are currently working with the farmers to redesign a fish passage channel east
of Cell 5 to connect the Marstons Mills River with a tributary that would connect with Middle Pond
and provide improved flow and fish passage opportunities.
The proposed work area is not within Estimated or Priority habitats of rare species and wildlife as
defined by the Natural Heritage Endangered Species Program (NHESP). It is also not within an Area
of Critical Environmental Concern or Outstanding Resource Waters, both regulated resource areas
identified and defined by MassDEP.
3.5 WATER QUALITY
The Three Bays estuary, downriver from the Site, has a Total Maximum Daily Load (TMDL) for
Total Nitrogen. A TMDL establishes the maximum loadings that a waterbody can receive and still
meet and maintain its water quality standards and designated uses. The Total Nitrogen TMDL for
the Three Bays estuary is 25,643 kg N per year while its current attenuated watershed load,
according to the Town of Barnstable’s Section 208 Compliance Report, is 46,221 kg N per year. This
means that the Three Bays estuary requires a reduction of 20,578 kg N per year in order to meet its
TMDL. According to a study completed at the Site by the University of Massachusetts Dartmouth
School for Marine Science and Technology (SMAST) in combination with data collected by BCWC, it
is estimated that over 7,500 kg N exits the Site via the Marstons Mills River on an annual basis. This
presents an opportunity to use a restoration at the Site to improve water quality in the Three Bays
estuary.
Nitrogen as a pollutant is significant for estuarine systems because it is commonly the limiting
nutrient for algal growth in those environments. Excess nitrogen fuels excess algal growth
(eutrophication) which then limits light availability during the algal growth stage and consumes
oxygen from the water column as dying algae decays and is consumed through microbial processes
– all to the detriment of ecology and habitat in these affected estuaries.
Nitrogen occurs in various forms in the environment and can transform between those forms
through oxidation and reduction processes in what is commonly referred to as the nitrogen cycle. In
developed areas like Cape Cod, most available nitrogen to aquatic systems is introduced to the
environment anthropogenically through wastewater disposal, fertilizers, and other less significant
sources. On Cape Cod, the addition of nitrogen to groundwater through on-site septic systems is
frequently cited as the most significant source of nitrogen contributing to impacted estuaries.
Nitrogen from septic systems originates primarily from human urine and quickly cycles through the
urea and ammonium forms during the aerobic and anoxic phases of the septic system treatment
process before entering groundwater primarily as nitrate-nitrogen. In the typically well oxygenated
1 http://maps.massgis.state.ma.us/map_ol/oliver.php accessed April 30, 2021
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Cape Cod Aquifer, nitrate remains relatively unaltered and unimpeded as it travels along with
groundwater flow prior to discharge to coastal systems where it is available to fuel the above-
referenced eutrophication process. An additional anoxic denitrification stage is necessary to
ultimately convert nitrate nitrogen to nitrogen gas in order to limit the eutrophication impacts from
excessive nitrate contributions.
Nitrogen Attenuation
Completion of the denitrification stage of the nitrogen cycle is referred to as nitrogen attenuation, or
a reduction of the amount of nitrogen in water. Nitrogen attenuation in wetlands occurs through one
of three processes: biological uptake, physical settlement, and bacterial denitrification. In uptake
nitrate is absorbed by wetland plants through roots and foliage during the spring and summer
months and utilized for growth. This nitrogen attenuation is seasonal and when vegetation dies back
each year much of this nitrogen is re-released back into the wetlands during the decomposition
process. In physical settlement, nitrogen contained in some of that biological material can settle to
the bottom and be buried. Some of that settled nitrogen can likewise be recycled back into the water
column. Neither biological uptake nor settlement are considered significant sources of long term or
permanent nitrogen attenuation.
Therefore, the primary source of long-term nitrogen attenuation within wetlands is bacterial
denitrification. In this process denitrifying bacteria respirate nitrate in the water and convert it to
nitrogen gas that is released to the atmosphere. This occurs via the successive reduction of nitrogen
compounds: nitrate to nitrite to nitric oxide to nitrous oxide to nitrogen gas. There are a couple of
key components to the success of this nitrogen attenuation process. First are anoxic conditions.
Denitrifying bacteria will only respirate nitrate in the absence of oxygen – if oxygen is available, they
will preferentially use it instead of nitrogen. The second key component is the amount of labile
organic matter in the ecosystem. Labile organic matter, primarily made up of carbon, is organic
matter that serves as an energy source for denitrifying bacteria. It also acts as an electron donor for
the reduction process of nitrate-nitrogen to nitrogen gas. This bacterial denitrification process is
most active in organic rich sediments at pond and wetland bottoms and edges.
Review of nitrogen attenuation literature indicates that the nitrogen attenuation of natural aquatic
systems varies significantly. This holds true when comparing one system type to another and when
comparing within system types. Another recent literature review focused on the New England area
was conducted by Horsley Witten and the Woods Hole Group in 2017 as part of another Cape Cod
retired cranberry bog restoration project. That study found that, while there was uncertainty
surrounding nitrogen attenuation of specific natural systems, there are certain key factors known to
maximize nitrogen attenuation. These factors include:
• A long retention time for water in the aquatic system in order to maximize the time available
for biochemical nitrogen species transformations and to facilitate anoxic conditions.
• A good supply of labile organic matter in order to provide the electron donor component of
the oxidation/ reduction process for the transfer of nitrate-nitrogen to nitrogen gas and to
serve as an energy source for microbial metabolism.
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• Anoxic conditions in order to favor the reduction of nitrate-nitrogen to nitrogen gas.
• Relatively warm temperature to accelerate the rate of biochemical nitrogen species
transformations.
• Neutral to slightly acidic pH to enhance the conditions under which microbial denitrification
can occur.
In addition, a relatively high nitrate loading rate input to any subject aquatic system will allow for
greater overall mass of nitrogen to be attenuated within the constraints of the attenuation capacity of
the system.
Further, that 2017 study found that despite the heavy emphasis the Massachusetts Estuaries
Program (MEP) places on ponds for nitrogen attenuation, wetlands of all types are likely to have
similar nitrogen attenuation capacities to ponds. As a result, the study concluded that a variety of
wetlands elements can be implemented in ecological restoration projects in order to achieve
conducive conditions for denitrification.
For this project the Team explored MEP studies conducted by SMAST since 2017 to search for recent
site-specific information for comparable climates and looked at literature related to water quality
impacts from permeable reactive barriers. MEP reports published since the 2017 nitrogen
attenuation literature review were for Barnstable Great Marshes-Bass Hole Estuarine System,
Menemsha Pond, Plymouth Harbor, and Wellfleet Harbor. Review of these studies revealed that no
ponds or wetlands had site specific nitrogen attenuation information. Several creeks and streams
had site specific data, which ranged from 3% to 60% nitrogen attenuation in the Barnstable Great
Marshes-Bass Hole Estuarine System Report (Howes et al., June 2017), 0% to 64% in the Menemsha
Pond Report (Howes et al., June 2017), 22% to 60% in the Plymouth Harbor Report (Howes et al.,
December 2017), and 0% to 8% in the Wellfleet Harbor Report (Howes et al., March 2017). This
indicates that, as previous literature reviews have found, nitrogen attenuation varies widely among
and within system types, even in the same geographic area.
Permeable Reactive Barriers
Permeable reactive barriers (also known as PRBs) have been used throughout the country as a
method of treating contaminated groundwater since the mid-1990s. In general, they work by
intercepting contaminated groundwater with a reactive media that allows for groundwater to flow
through while the contamination is treated. For nitrogen attenuation, PRBs can be used to intercept
and remediate nitrogen in groundwater by artificially enhancing the anoxic, denitrification phase of
the nitrogen cycle described above. Requiring groundwater to flow through a carbon-rich media,
typically a woodchip-based media or emulsified vegetable oil, enables denitrifying bacteria to
respirate nitrate-nitrogen in the groundwater and convert it to nitrogen gas. The carbon media
serves as a food source to support the population of denitrifying bacteria.
Literature review indicates that nitrogen attenuation for permeable reactive barriers and other
carbon-based filter systems such as bioreactors varies. While studies agree that these systems
provide nitrogen attenuation, there is disagreement over how much treatment such systems
provide. Factors influencing nitrogen attenuation in permeable reactive barriers are similar to those
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discussed above for natural aquatic systems and include hydraulic residence time, water
temperature, media composition, and incoming nitrate concentrations.
Recent studies have examined whether incorporating biochar into woodchip permeable reactive
barriers leads to additional water quality improvements. A 2019 study found that biochar
amendments significantly improved nitrate removal with high influent nitrate concentrations (16
mg/l), but that nitrate removal was not enhanced under low influent nitrate concentrations (4.5 mg/l)
(Coleman et al., 2019). This same study found that biochar amended systems were significantly
worse at phosphorus removal than woodchip only systems. A more recent study found that while it
is possible to improve nitrate removal by constructing a permeable reactive barrier made out of a
mixture of 20% biochar and 80% woodchips, it can lead to large releases of phosphorus
(Vismontiene and Povilatis, 2021).
3.6 INFRASTRUCTURE AND UTILITIES
Within the Site, there are stream crossings, flow control structures, pump houses and pipes used for
cranberry production. No overhead utilities were observed on the Site. BCWC is coordinating with
the farmers to move pump houses still in use to alternative locations that will better facilitate water
transfer for farming. Unused pump houses will be removed during construction. Unused irrigation
pipes and associated infrastructure exhumed within the restoration footprint during restoration
construction will be removed and disposed of by the contractor. Many of the berms and flow control
structures will be removed. The culvert under Bog Road will not be impacted during construction.
Dirt road access for farm vehicles will be maintained around the southern portion of Cell 4.
3.7 RECREATION
The Site is currently used by the public for walking and wildlife viewing. The trails are located along
the earthen berms created during cranberry farming to separate the bog cells.
• The Site is currently owned by the BCWC, with adjacent active bogs owned by farmers, so
recreation is at the permission of the landowners.
• Recreational opportunities are all passive. The dirt roads surrounding the bogs are used by
residents from adjacent neighborhoods for walking, dog-walking, running, and bird-
watching.
• Following restoration, recreation will not be permitted south of Cell 4 or within the adjacent
actively farmed bogs.
3.8 HISTORICAL/CULTURAL RESOURCES
The Mashpee Tribe of the Wampanoag Nation have lived in the Marstons Mills River watershed for
thousands of years, harvesting migratory herring and many other animal species and native plants.
Wampanoag people foraged the wild cranberries and hunted wildlife such as frogs, eels, rabbit,
deer, and raccoon. They relied on the wetlands for the springs, which they used as drinking water,
and Atlantic White Cedars, which they harvested to build their homes.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Beginning in the 17th century, European colonizers began to harness the Marstons Mills River to
power grist mills. In the late 1800s, wetland buffers along the Marstons River and many other rivers
on Cape Cod were modified for cranberry cultivation. Cranberry cultivation led to damming, sand
application, and ditching along the Marstons Mills River for the next nearly 150 years. No state-
listed historical sites are known to exist within the study area 2. However, the project will be
reviewed by the Massachusetts Historical Commission during the permitting process, which will
determine the need for further assessment of historical and archaeological resources.
3.9 SITE CONSTRAINTS
Based on the data collected, the site assessments and other surveys, we evaluated the constraints on
the proposed ecological restoration efforts. Construction staging and access can be a constraint on
many restoration projects, but this site has ample staging and access points. The former farm roads
that surround the bogs allow for construction vehicle access to the locations where work is
proposed.
While the bogs on the Site are mostly retired, the bogs between Cell D and Bog Road, as well as
south of Cell 4, are still actively farmed and have historically relied on water delivered from the
Marstons Mills River. Because farming will continue in bogs that rely on the river, some of the flow
control structures will need to remain in place and portions of the restored bogs will be impacted by
the flooding that occurs during the fall for harvesting and winter for frost protection.
3.10 PROPERTY LINE SURVEY
A property line survey was conducted at those parcels surrounding and abutting the Site with
potential to have property lines encroaching on the proposed restoration area (Appendix E, Figure
HW2). Properties included in this survey were located on the following roads:
• Bog Road;
• Waters Edge Road;
• Berry Hollow Drive;
• Whistleberry Drive; and
• Turtleback Road.
Prior to conducting field survey work, target properties were researched at both the Town of
Barnstable Assessors Office and the Barnstable County Registry of Deeds to identify target property
monuments and bounds to locate in the field. The property line survey was completed following
methods provided by the Massachusetts Board of Registration of Professional Engineers and Land
Surveyors (250 CMR 6.00: Land Surveying Procedures and Standards). The totality of researched
property information and field-surveyed boundary locations were evaluated following referenced
survey standards to identify the locations of those adjacent property boundaries in close proximity
to the Site restoration area.
2 https://maps.massgis.digital.mass.gov/MassMapper/MassMapper.html accessed May 28, 2021
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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3.11 SURFACE WATER AND GROUNDWATER MONITORING
Site hydrologic conditions were monitored through the installation and use of 3 groundwater
monitoring wells and 6 surface water monitoring stations. Monitoring wells were installed in
boreholes dug using a hand auger. All monitoring wells are 2 inches in diameter and consist of 5 feet
of slotted PVC underneath 5 feet of solid PVC riser. The wells were all installed to the maximum
depth below the water table practical (generally approximately 2 feet) and the PVC riser was cut to
allow a finish stick up height of 1 to 2 feet above the bog surface. The locations of each monitoring
well are shown on Figure HW1 (Appendix E). The following summarizes the monitoring well
locations:
• MW-1 was originally installed in the Big Coombs Cell 1 on August 17th, 2022, at the
northern tip of the Site. However, the well had to be removed to allow for cranberry harvest
in the cell and was re-installed close to its original location on December 6th, 2022.
Groundwater was encountered approximately 9 inches below ground surface (BGS).
• MW-2 was installed on August 17th, 2022, in Abandoned Bog Cell 6, approximately 1400 feet
SSE of MW-1. This abandoned bog cell has a dry loose sand layer at the surface about 2.5 feet
thick that results in a deeper depth to groundwater than at MW-1. Groundwater was
encountered here at approximately 4.5 feet BGS.
• MW-3 was originally installed in Winnies Cell 3 on August 17th, 2022, at the western half of
the Site. However, like MW-1, the well had to be removed for the fall cranberry harvest and
was re-installed on December 6th, 2022. It is located about 1300 feet SW of MW-2.
Groundwater was encountered approximately 10 inches BGS.
Staff gauges or water level reference stakes were used as surface water monitoring locations (SG).
The locations of each SG are also shown on Figure HW1 (Appendix E). The following summarizes
the SG locations:
• SG-1 was installed in a drainage ditch on the NW tip of Big Coombs Cell 1, only a few feet
east of Bog Road. It consists of a wooden stake.
• SG-2 was installed in a reservoir between Big Coombs Cell 1 and Winnies Cell 3. It consists
of a wooden plank affixed to a metal rod in water a few feet from the edge of the reservoir
and is located about 260 feet WSW of MW-2.
• SW-3 was installed in a channel leading into the pond of Cook House Cell 4. Like SG-2, it
consists of a wooden plank affixed to a metal rod. SG-2 is located approximately 660 feet S of
SG-2.
• SG-4 is a wooden stake installed in Outlet Channel Cell 7. It is approximately 1500 feet SSE
from SG-3.
• SG-5 was installed in the northern drainage ditch of Swamp Cell 5. It is a green metal fence
post located roughly 740 feet south of SG-3.
• SG-6 is a replacement for SG-1 (which was found to be at too high of an elevation for low
water periods) and was installed approximately 57 feet away from SG-1 in deeper water near
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the mouth of the culvert at the NW tip of Big Coombs Cell 1. SG-6 consists of a PVC
standpipe 2 inches wide in diameter. Both SG-1 and SG-6 remain in place.
Depth-to-water (DTW) measurements were taken from the tops of the well casings at each MW.
DTW measurements were taken from the top of the wooden stake at SG-1 and SG-4, top of the
wooden plank at SG-2 and SG-3, top of the post at SG-5, and top of casing at SG-6.
On December 6th and 7th, 2022, Van Essen Instruments brand TD-Diver automated water level
loggers were placed in wells MW-1, MW-2, MW-3, and at SG-2, SG-3, and SG-6. A separate logger to
record barometric pressure (for compensation of the collected water level data for changes in
atmospheric pressure) was attached to a tree in the uplands along the southwest edge of Cell 3B. The
loggers were programmed to take readings every hour. Data was downloaded on March 15th, 2023,
but all loggers remain on site collecting data. Manual depth to water measurements were taken at all
monitoring locations on December 9th, 2022, and March 15th, 2023.
3.12 SURFACE WATER HYDROLOGY ANALYSES
Flow estimates for the Marstons Mills River through the Site were based on field data collection and
desktop analyses. This section of the report describes the various approaches for evaluating the
hydrology of the Marstons Mills River.
FEMA Mapping
The Site is mapped as Zone X according to the National Flood Hazard Layer dataset (Figure 10).
Zone X is defined as the area of minimal flood hazard between the limits of the base flood and the
0.2-percent-annual-chance (or 500-year) flood.
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Figure 10. FEMA National Flood Hazard Layer Firmette. Project Site mapped as Zone X.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Locally-collected Streamflow Data
USGS Stream Gage
The EPA and USGS collaborated to install a stream gage on the Marstons Mills River downstream of
the cranberry bogs in 2021. The gage data covers a period starting beginning on June 1, 2021 (Figure
11). The data shows that the discharge drops below 1 cubic foot per second (cfs) during January and
has a quick spike up above 30 cfs at the end of February. This is reflective of when the farmers use
stoplogs to flood the bogs for frost protection over the winter. Once the stoplogs are removed, there
is a sudden increase in discharge as the bogs are drained. In the summer months, the farmer
irrigates the fields when needed, pumping from the Marstons Mills River. The discharge from June
through September typically ranges between 2 and 5 cfs. In the fall, the farmers flood the bogs once
again to harvest the cranberries. Other changes in discharge are due to levels of precipitation,
groundwater inputs, groundwater well withdrawals from nearby houses, and any other
manipulations the farmers might make for cranberry production.
Figure 11. Discharge measurements of the Marstons Mills River gage (0110588332) at the downstream outlet of the
Marstons Mills Bogs.
SMAST Stream Flow Assessment
SMAST measured stream flow at nine locations within the Site from mid-2018 to mid-2019.
Monitoring locations were placed to understand water movement throughout the Site (Appendix
D). The report shows annual flow into the Site as 1.3 cfs and flow leaving the Site as 6 cfs. From
monitoring at the upstream and downstream ends of the bogs, they found that the streamflow
entering the Site doubles in Cell 1. Overall, the assessment found that groundwater inputs are the
dominant contribution to streamflow, as it increases steadily as flow moves in the downstream
direction through the project area.
051015202530354045
6/13/2021 9/21/2021 12/30/2021 4/9/2022 7/18/2022 10/26/2022 2/3/2023 5/14/2023Discharge (cu. ft/s)Date
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Surface Water and Groundwater Data Collected by Horsley Witten
Data collected from water level loggers at monitoring wells and staff gages was compiled for
analysis to determine water elevations throughout the bog complex. Logger data was compensated
for barometric pressure variations and then converted to elevations based on surveyed reference
elevations at each monitoring well and staff gauge in order to create a record of water elevations
through time across the Site. Figure 12 depicts that record of water elevations for all logger locations
across the Site from December of 2022 (after removed monitoring wells were replaced post
cranberry harvest) through March of 2023 (the date of the last data download prior to this report).
All loggers currently remain on Site collecting data. Figure 12 also depicts a record of precipitation
for the same monitoring period with data obtained from nearby Weather Underground Station
KMAMARST7 Santuit-Newtown.
Figure 12. Water Elevations December 2022 - March 2023
Figure 12 shows several water level response features common in the Cape Cod Aquifer:
• Groundwater and surface water levels move similarly to each other in both timing and
magnitude.
• Rapid spikes in groundwater and surface water levels can be seen in response to larger
precipitation events and proportional to the size of the event.
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But the larger and most obvious water level fluctuations are due to human water level management
for cranberry farming. In particular, it appears that on February 7th water was backed up in Cell 1
before being let out again on February 14th. This is a common practice in cranberry farming for frost
protection.
Figure HW4 (Appendix E) is a water table map depicting the contoured height of the water table
based on measurements taken from our most recent site visit on March 15, 2023. This visit coincided
with the installation of new monitoring wells and staff gauges upstream of Bog Road not mentioned
above as part of this current phase of the project. However, the incorporation of these additional
monitoring points allows for a more complete picture of the water table in the Site area. Data from
these additional monitoring points will be more widely used for all forthcoming project phases.
The water table map depicts typical water table conditions for a gaining stream in the permeable
Cape Cod Aquifer. There is a general gradient from upstream to downstream as would be expected
as well as a general focusing of groundwater from both sides of the river corridor into the river itself
(note the “V” or convex shape of the contours pointing upstream). The timing of these contoured
water table data from mid-March is outside of the main windows of active water management for
cranberry farming – harvest, winter frost protection, and growing season irrigation. As such, this
map likely depicts a time with as natural as possible hydrologic conditions for this actively farmed
setting. Note that at the mid-March time of this water table map the many water control structures
on Site still had some boards in them backing up water between many bog cells, but the setting of
these boards and water management on Site in general is likely as inactive at the time of this map as
commonly occurs.
Development of Flood Flow Estimates
The Natural Resources Conservation Service (NRCS) Technical Release 55, Urban Hydrology of
Small Watersheds (TR-55) rainfall-runoff analysis method is an industry standard method for
estimating discharge-frequency curves. However, it assumes that peak flows in surface waters are
driven by surface runoff, not by groundwater baseflow. We therefore adapted some of the
procedures in TR-55 to better represent conditions and processes in the watershed. More detail is
provided below. We used HydroCAD software to simulate runoff hydrographs for a suite of design
events ranging from the 2- to 500-year average return period events (Appendix F).
Watershed Characteristics
We delineated the contributing area for the watershed using the USGS dataset “Groundwater
Contributing Areas for Cape Cod and the Plymouth Carver Regions of Massachusetts” in
combination with LiDAR data and a series of ArcGIS tools. The contributing groundwater
watershed used in the analysis was 8.8 square miles. We used the 2016 MassGIS Landuse/Land
Cover Dataset to determine the primary land uses within the watershed. The watershed
surrounding the Site is characterized by forest and single-family residential areas.
We used the USDA NRCS Soil Survey Geographic Database (SSURGO) dataset to determine the
primary hydrologic soil groups within the study watershed. The surface geology of Cape Cod is
primarily highly permeable sandy material, which is reflected in Marston’s Mills River watershed.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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We defined our precipitation events for the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year average
return periods using the information published in the National Oceanic and Atmospheric
Administration (NOAA) Atlas 14 Volume 106.
Runoff Curve Number
We calculated a single area-weighted runoff curve number (RCN) of 51 for the watershed. The data
used in the RCN analysis is based on data from the following sources:
• NRCS SSURGO dataset;
• 2016 land use dataset from MassGIS data;
• Watershed delineations by Inter-Fluve, as described above; and
• RCNs available in TR-55.
We assigned an RCN to each area with a unique hydrologic soil group and land use combination
and then calculated the area-weighted RCN for the watershed.
Time of Concentration
We calculated a time of concentration (TC) for the watershed in the study area using a novel method
that considers the unique geology of Cape Cod. Most of the rainfall on Cape Cod quickly infiltrates
to groundwater due to the glacial gravel and sand deposits. The drainage basin has the capacity to
absorb a tremendous amount of rainfall largely muting the flood hydrology. For this application, we
developed a TC flow path in a GIS environment using the USGS groundwater contributing areas,
and assumed a travel velocity commensurate with the hydraulic conductivity of a gravel/clean sand
aquifer 3. For this application, we assumed a subsurface flow rate of 3.7 feet per minute.
Results
Table 1 presents the results from the HydroCAD simulations.
Table 1. Discharge frequency estimates for Marston’s Mills River
Average Return
Period (Years)
Annual Exceedance
Probability (%)
Discharge
(cfs)
2 50 8
5 20 18
10 10 29
25 5 46
50 2 62
100 1 78
200 0.5 99
500 0.2 129
While other peak flow estimation methodologies were evaluated, they were considered substantially
less reliable for the Cape Cod region where data is sparse, flow has historically been highly affected
by regulation, diversions, or cranberry bogs, and regression equations developed using data from
other areas generally do not apply. This is attributable to the low-lying topography and regional
3 Allen Freeze and John A Cherry. Groundwater. Prentice-Hall, Inc. (1979)
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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geologic patterns that include lithology of coarse-grained stratified drift, which complicate
delineation of contributing areas and groundwater patterns and complicate attempts to model
rainfall-runoff processes.
4. Surface Water Hydraulic Model
We built a two-dimensional, unsteady flow hydraulic model using the U.S. Army Corps of
Engineers Hydraulic Engineering Center River Analysis System (HEC-RAS) software version 6.5.
The model extends from the upstream end of Cell A to the outlet of Cell 4. The typical flows
observed from the monitoring efforts as well as the 2- and 100-year flood recurrence intervals were
analyzed in the model. The primary purpose of the analysis was to assess changes in retention time,
wetted area, and flood profiles associated with the proposed project under various hydrologic
conditions.
4.1 TERRAIN
Inter-Fluve developed the existing conditions terrain using the field survey data collected in April
2021, August 2021, and March 2023. The topographic and bathymetric data were collected by Inter-
Fluve using RTK GPS equipment. We supplemented this data with high-resolution LiDAR data
from a 2021 USGS dataset. The terrain is referenced to the National American Vertical Datum of
1988 (NAVD88) and the National American Datum of 1983 (NAD83) State Plane Massachusetts –
horizontal coordinate system. The horizontal and vertical units are in feet.
Inter-Fluve manipulated the existing conditions surface using AutoCAD Civil3D software to
develop a terrain model, which represents the proposed condition, reflecting the dispersed flow
alternative. The proposed terrain has the topographic complexity built into the surface as well as the
proposed ponds, cut berms, filled ditches, and lowered bog surface.
4.2 COMPUTATIONAL DOMAIN
The computational mesh was developed over the composite digital elevation model of the channel
bathymetry and overland topography (Figure 13). The mesh consists of cells with dimensions
ranging from 2 to 25 feet with the smallest grid cells utilized along topographical breaks to capture
small discrete variations in elevation which could impact inundation timing and extent.
Additionally, smaller cells were utilized within the narrow channel to provide higher resolution
results. Breaklines were used to align cell faces along prominent high ground features such as roads
and berms, to prevent flow from artificially “leaking” between cells. In large, relatively flat
floodplains, especially those developed from LiDAR data, some disconnected inundated areas are to
be expected, as small depressions are filled with water from adjacent cells. However, the relative
volume transferred between these areas is small, and the effects on the overall hydraulic patterns of
the system are considered negligible. Breaklines were also used along channel alignments to orient
computational cells perpendicular to flow.
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Figure 13. Existing conditions 2D model domain for Marstons Mills River bogs. Boundary condition locations are shown as
blue lines.
4.3 INFRASTRUCTURE
Numerous crossings and flow control structures are present in the existing conditions model. All of
these structures were surveyed by Inter-Fluve and represented in the model where appropriate.
Culvert geometry, calculation coefficients, and roughness values were based on field observations,
surveyed data, and HEC-RAS hydraulic reference tables. In the proposed conditions model, culverts
were removed as shown on the design drawings.
4.4 BOUNDARY CONDITIONS
Boundary conditions consist of an inflow hydrograph at the upstream end of the model domain and
normal depth at the downstream end of the model domain. The inflow hydrograph consists of a
quasi-steady state hydrograph, which gradually ramps up to a discharge of interest and remains
constant for a period of time long enough to allow the model to reach a steady-state condition
(Figure 14). This approach generally provides conservative results with respect to floodplain
inundation by underrepresenting floodplain storage. An initial water surface elevation was set to 41
feet to help stabilize the model. The modeled flows include a low flow (2 cfs), a daily average flow (4
cfs), a frequent flood similar to the 2-year flood event (8 cfs), the 10-year flood event (29 cfs) and the
100-year flood event (78 cfs). Normal depth boundaries are based on the approximate slope of the
channel or floodplain at the respective boundary locations.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Figure 14. Inflow quasi-steady state hydrograph used as the upstream boundary condition in the 2D model.
4.5 ROUGHNESS COEFFICIENTS
We assigned Manning’s “n” values based on observed channel substrate and floodplain vegetation
conditions. Table 2 summarizes the Manning’s “n” values used in the existing model. In the
proposed model, the bog surface was increased to a roughness value of 0.2.
Table 2. Manning’s “n” values used in the 2D hydraulic model
Location Manning’s “n”
Bog Surface 0.04
Wood Wetlands 0.06
Water 0.035
Mixed Forest 0.1
Dirt Roads 0.04
4.6 PROPOSED CONDITIONS – WETTED AREA
During the design process, the dispersed flow alternative was chosen over the channel alternative.
Initially, the modeling results for the dispersed flow alternative showed that removing the channel
in Cell 1 caused the water surface elevation upstream of Bog Road to exceed the bog surface,
impacting the active cranberry cultivation. To mitigate the increased water elevation upstream, sand
was removed in the proposed conditions downstream of Bog Road to lower the bog surface in Cell 1
to an elevation of 42.5 feet. In Cell 3, the bog surface was lowered to 42 feet. Removing the sand
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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achieves the goal of wetting and spreading water across the bog surface throughout the Site, while
mitigating the flooding concerns upstream of Bog Road.
In Figure 15, at 2 cfs, the proposed design condition shows water dispersed across the bog surfaces,
while the existing condition shows water contained within the channel. The proposed water depth is
approximately 2-4 inches on the bog surface and 1 to 1.5 feet in the depressions of the topographic
complexity. The increased wetted area at this low flow event highlights the benefits of sand removal
and dispersing the flow across the bogs.
Figure 15. Inundation extents of the existing (pink) and proposed (blue) conditions model at the 2 cfs (low flow).
In Figure 16, at 4 cfs, the proposed design condition shows water dispersed across the bog surfaces,
while the existing condition shows water contained within the channel. The proposed water depth is
approximately 4-5 inches on the bog surface and 1.5 to 2 feet in the depressions of the topographic
complexity. There is slightly more wetted area in the proposed condition under 4 cfs than under 2
cfs, specifically in Cells A-D and Cell 3.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Figure 16. Inundation extents of the existing (pink) and proposed (blue) conditions model at the 4 cfs (average daily flow).
In Figure 17, at 8 cfs, the proposed design condition shows water dispersed across the bog surfaces,
while the existing condition shows water contained within the channel. The proposed water depth is
approximately 6-7 inches on the bog surface and 2 to 2.2 feet in the depressions of the topographic
complexity. There is slightly more wetted area in the proposed condition under 8 cfs than under 4
cfs, specifically in Cells A-D and Cell 3.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Figure 17. Inundation extents of the existing (pink) and proposed (blue) conditions model at the 8 cfs (2-year flow).
The 100-year event was also modeled to assess changes in flooding to the surrounding area. In both
the existing and proposed conditions, the water is contained within the berms that surround the
bogs. The removal of the inner berms and flow control structures lowers the water surface elevation
for the 100-year event in the proposed condition. There is no difference in the existing and proposed
water surface elevations in the downstream channel outside of the Site.
4.7 PROPOSED CONDITIONS – RESIDENCE TIME
In addition to the increased wetted area, the proposed condition also increases the retention time, or
the amount of time the water takes to move through the system. Because water is dispersed
throughout the bogs and higher roughness values in the channel and bog surface, the retention time
increases by 1.5 days in the proposed condition for the 2-year flood event. The total amount of time
the surface water takes to flow through the Site is two days. The incoming groundwater will likely
take longer to get through the system as it works its way through the topographic complexity;
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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however, HEC-RAS is limited to modeling surface water. Figure 18 shows the lag that occurs as flow
enters and leaves the Site. The lag for the proposed outflow is greater than the existing condition for
each flow event.
Figure 18. Inflow vs. Outflow at a range of flows for the existing and proposed conditions.
5. Groundwater Hydraulic Model
Groundwater modeling was performed to evaluate the movement of groundwater, including gains
and losses within the stream channel, in the project area. Numerical groundwater modeling uses a 3-
dimensional grid of model cells to represent aquifer properties throughout a project area. Thousands
of simultaneous finite-difference equations representing the groundwater flow conditions between
each of the thousands of model cells are solved to estimate groundwater conditions within the
modeled area based on these gridded properties. Model calculations are performed using the United
States Geological Survey (USGS) MODFLOW 2005 model program which is graphically
manipulated and interpreted by the project team using Groundwater Vistas 8 (Environmental
Simulations, Inc) graphical user interface (GUI). Groundwater Vistas was also utilized as the GUI to
interact with the separate USGS MODPATH particle tracking model used to track the fate and
transport of water molecules (particles) through aquifer space and time.
5.1 GROUNDWATER MODEL CONSTRUCTION
For the subject Site we are fortunate that the existing USGS regional groundwater model for the
Sagamore Lens (“Simulated Water Source and Effects of Pumping on Surface and Ground Water,
Sagamore and Monomoy Flow Lenses, Cape Cod, Massachusetts”, Walter and Whealon, 2004),
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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contains the project Site. The steady-state version (i.e. representing average, long-term groundwater
conditions) of this USGS model was acquired by Horsley Witten and then modified to better
represent Site-specific conditions. The USGS regional model was developed in the NGVD29 vertical
datum whereas survey data for this project was collected in the newer NAVD88 datum. NOAA’s
NGS Coordinate Conversion and Transformation tool was utilized to determine that throughout the
subject area NGVD29 elevations are 1.05 feet higher than equivalent NAVD88 elevations. As such,
elevations reported in model results are 1.05 feet higher than their equivalent NAVD88 values.
Cells in the original USGS regional model have 400-foot lengths in the x and y horizontal directions.
Cell resolution was refined to 100-foot horizontal length cells in the vicinity of the subject area in
order to provide better accuracy and resolution for project purposes. Vertical resolution in the
original USGS model consists of twenty 10-foot thick, level, layers and was not refined for this
project as that vertical resolution is suitable for project analyses.
The Marstons Mills River is present in the USGS regional model but was also better refined for this
project to improve its utility for project analyses. Rivers in the model utilize the Stream Package of
MODFLOW, which calculates gains and losses in a stream by comparing the adjacent groundwater
cells heads to the stream bottom elevation within each stream cell, and then multiplying this
potential by a conductance value. Conductance is calculated based on stream parameters including
length, width, streambed thickness, and streambed conductivity. Stream bottom elevations were set
in the model based on the lowest stream channel elevation points obtained by survey, converted into
NGVD29 elevations. Conductance in the stream was altered iteratively to obtain groundwater
outflows (gains to the stream) equal to the long-term average flow condition of the USGS Marstons
Mills River downstream outlet of bog flow gage (USGS 0110588332). Along with streamflow
calibration, hydraulic heads calculated by the regional model were compared to in situ observations
of groundwater levels (Appendix E) and were found to be in agreement.
The domain of the original USGS Sagamore Lens model, as well as the refinements made for this
subject project analysis are shown below in Figure HW5 (Appendix E).
5.2 GROUNDWATER MODELING ANALYSES
The groundwater contributing area for subject area was determined in the model using reverse
particle tracking (Figure HW6, Appendix E). Particles represent infinitesimally small units of water
in the aquifer which are tracked throughout the model over time. Particles can run forward or
backwards, either calculating where a particle released at a specific point would go, or where a
particle must be coming from in order to arrive at the specific point. Particles which arrive in the
vicinity of the bog system originate to the northwest.
Once the overall groundwater capture area for the Site was determined, further particle tracking
analyses were conducted to better inform the three-dimensional movement of groundwater. Land
areas with high nitrogen loads were identified using the Cape Cod Commission’s Watershed Multi-
Variant Planner (MVP) tool to estimate nitrogen loads from specific neighborhoods within model-
identified groundwater contributing areas. In this way those contributing areas likely to contain
maximum nitrogen concentration were identified for priority targeting of PRB interception.
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Watershed MVP provides estimates of the number of parcels, nitrogen load per year, and
wastewater volume discharged within a given area.
Forward tracking was used to identify how groundwater from these MVP-identified priority land
areas moved towards the Site in three dimensions in order to identify where PRBs could most
practically be located to intercept high nitrogen load inflow. Forward particles were placed
throughout and slightly beyond the extent of the groundwater contributing area. These particles ran
forwards to determine their path through the subject area and determine their position as they
transit the subject area and their ultimate fate. The use of forward particle tracking and a figure
depicting that analysis is included in the PRB design section of this report below.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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6. Project Design
The project scope of work includes filling the ditches, creating a topographically-complex ground
surface, and removing and/or replacing barriers to flow and aquatic organism passage throughout
the former bogs within the Project Site. Other elements of work include creating new pond and
maintaining pedestrian access.
6.1 CELLS A, B, C, AND D (COMPREHENSIVE STUDY AREA)
Cells A through D are in the headwaters of the Marstons Mills River upstream of active cranberry
farming and road infrastructure. The design goals for this area have been shifting through the
design process. In the paragraphs below, we describe what is shown on the design drawings.
However, the BCWC has identified these bogs as the Comprehensive Study Area (CSA), an area that
would allow for the monitoring and comparison of a variety of restoration design methods. The
design of this CSA will be refined in a later design phase. Possible restoration actions to be studied
could include:
• The original design goal for this area of the project was to disperse surface and groundwater
flows across a wetland surface of complex topography to increase the residence time of the
water flowing through the bogs, increase the surface area contact between the water and the
wetland ground surface, and provide a range of plant and animal habitat features through
varying topography and proximity to the water elevation.
• The perimeter and lateral ditches, as well as the mainstem channel ditch of Cells A through
D could be filled with soil to remove the drainage network and restore the hydrologic
connectivity important to wetland development and functionality. Two open water areas
within the existing stream alignment could remain as small ponds for aquatic habitat and
additional nitrogen attenuation. These open water areas are immediately upstream of the
existing berms at the downstream ends of Cells B and D.
• A permeable reactive barrier (PRB) is proposed in a portion of the ditch on the south side of
Cells A and B.
• Topographic complexity grading could be completed across the bog surfaces of Cells A
through D.
• Large wood slash, including branches and small trees or saplings, could be installed in
clusters throughout the bog surface of Cells A through D to provide habitat for a variety of
wetland animal species.
The earthen berms and flow control structures in the CSA will be maintained for access and to
provide control over the water for the proposed studies.
Two upland areas on the north side of Cell A were used historically by farmers as a source of sand
for the cranberry bogs. Excess excavated sand and soil will be placed in these former borrow pits,
called ‘sand reuse areas’ on the design drawings, during construction.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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6.2 CELL 1
Cell 1 is located downstream of Bog Road and is divided into four bog cells, each separated from
each other by earthen berms and flow control structures: Cell 1A is the larger main portion of the
cell where the active stream currently flows; Cell 1B is a smaller cell in the northwest corner that
receives groundwater inputs; Cell 1C is a smaller cell in the northeast corner that receives
groundwater inputs; Cell 1D is between Cell 1A to the north and two irrigation ponds to the south.
The design goal for Cell 1 is to disperse surface and groundwater flows across a wetland surface of
complex topography while not increasing water levels to an extent that would be detrimental to the
active farming upstream of Bog Road. The water dispersal across the bog surface will increase the
residence time of the water flowing through the bogs, increase the surface area contact between the
water and the wetland ground surface, and provide a range of plant and animal habitat features
through varying topography and proximity to the water elevation.
To achieve broad water dispersal, the proposed designs include filling the main stream channel and
perimeter and lateral ditches, removing a portion of the sand, and constructing a range of
topographic features that will provide varying topography through the site. Under proposed
conditions, the Marstons Mills River will flow under Bog Road into Cell 1 and then disperse
throughout the bog. The bog surface is proposed to be lowered to elevation 42.5’, which matches the
existing top of bank in Cell 1 and is roughly 0.5-foot above groundwater levels observed in Cell 1.
Without a stream channel and by removing sand in the outer areas of Cell 1, the flow reaches areas
of the cell that are now largely dry. Slash, including saplings, logs, logs with rootwads, and vertical
timber piles will be installed throughout the bog surface to provide aquatic habitat and roughness
that will aid in dispersing water onto the wetland surfaces.
Five earthen berms and their flow control structures will be removed: a small berm just downstream
of Bog Road; the berm separating Cell 1A and Cell 1B; the berm separating Cell 1A and Cell 1C; the
berm separating Cells 1A and 1D; and the berm downstream of Cell 1D. The earthen berm and flow
control structure downstream of Cell D will remain in place and will not be altered.
The perimeter and lateral ditches will be filled with soil to remove the drainage network and restore
the hydrologic connectivity important to wetland development and functionality. Two open water
areas along the western and northern edges of the bogs will be constructed as small ponds for
aquatic habitat and additional nitrogen attenuation. These open water areas will be approximately
1.5 feet in depth and are placed in areas of known groundwater inputs. Earthen berms
approximately 1.5 feet high will be built around the bog edge of these ponds to increase the holding
time of the water, thus increasing the opportunities for nitrogen attenuation.
Topographic complexity grading will be completed, and large wood slash will be installed, across
the bog surfaces.
Cell 1B is a proposed vegetation experimental study zone. The study design is currently being
developed but is likely to focus on climate resiliency of plants through the comparison of the
survival and growth of Atlantic white cedar trees sourced from different states along the east coast
of the United States.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Cell 1C is higher in elevation than the adjacent portion of Cell 1A, resulting in a drier ground
surface. Inter-Fluve proposes removing 2.5 feet of sand from the bog surface of Cell 1C to reduce the
ground elevation and increase the hydrologic connectivity. The same topographic complexity and
slash design elements described above are proposed for this cell after the sand removal. Cell 1C is a
second proposed experimental study zone. The study design is currently being developed but is
likely to focus on plants of significant importance to the local Indigenous communities.
Downstream of Cell 1D are two irrigation ponds between 5 and 7 feet deep. Inter-Fluve proposes
removing the earthen berms at the upstream and downstream ends of these ponds as well as the
earthen berm diving the two ponds. The designs include partial filling of this larger pond so the
proposed depth is approximately 1.5 feet to improve nitrogen attenuation opportunities and provide
a reuse area for excavated sand. The Marstons Mills River will continue to flow through this pond to
Cell 3 downstream.
6.3 CELL 3
Cell 3 is located downstream of the irrigation ponds. The design goal for Cell 3 is to disperse surface
and groundwater flows across a wetland surface of complex topography. The increased water
dispersal across the bog surface will increase the residence time of the water flowing through the
bogs, increase the surface area contact between the water and the wetland ground surface, and
provide a range of plant and animal habitat features through varying topography and proximity to
the water elevation.
Water will flow into Cell 3 under a vehicle crossing at the south end of a shallow pond, constructed
by joining the two irrigation ponds currently at this location. As the water flows under the vehicle
crossing, the water will then spread out across Cell 3 around the topographic features. With no
distinct channel to follow, water will flow in different locations depending on topography, plant
growth, wind, and other factors.
The earthen berms and flow control structures at the up and downstream ends of Cell 3, as well as
the earthen berm and flow control structure dividing Cell 3 will be removed. The perimeter and
lateral ditches, as well as the existing straightened stream channel, will be filled with soil to remove
the drainage network and restore the hydrologic connectivity important to wetland development
and functionality. Topographic complexity grading will be completed, and large wood slash will be
installed across the bog surfaces.
6.4 CELL 4
Cell 4 is located downstream of Cell 3 and is characterized as currently not being farmed because of
the challenges of keeping the bog dry. The bog currently has a large, shallow pond in the middle
with mostly native wetland vegetation growing around the pond. The design goal for Cell 4 is to
disperse surface and groundwater flows across the wetland surface. The increased water dispersal
across the bog surface will increase the residence time of the water flowing through the bogs and
increase the surface area contact between the water and the wetland ground surface.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Water will flow into Cell 4 through the topographic features created in Cell 3 and in the area where
the earthen berm that is currently between Cells 3 and 4 will be removed. Water will flow into the
pond in Cell 4 and then exit Cell 4 through a meandering channel that will gradually drop the water
elevation to meet the elevation of the ditch that conveys water out of Cell 4 and into Cell 5. The
channel will have a slope of approximately 0.1 feet/feet, a bottom width of 2 feet, and banks that are
1 foot in height at a 2(H):1(V) slope.
The earthen berms and flow control structures at the upstream end of Cell 4 will be removed. The
berm at the downstream end of Cell 4 will remain to maintain farmer access and water control
within the downstream bogs.
The perimeter and lateral ditches will be filled with soil to remove the drainage network and restore
the hydrologic connectivity important to wetland development and functionality. The existing pond
will not be altered through construction. On the western side of the bog, the northern portion of the
existing stream channel will be filled to match the adjacent bog surface, while the channel will
remain open adjacent to, and downstream of, the entrance of the proposed channel coming out of
the pond in Cell 4.
Large wood slash will be installed across the bog surface and along the perimeter of the pond.
6.5 CELL 6
Cell 6 is a small isolated bog east of the two existing irrigation ponds. It has been abandoned for
more than 20 years and, because of the sand placed on top of the underlying peat, pitch pine
saplings currently grow on the dry sandy surface. The designs include the removal of 1 foot of sand,
filling the ditches, the completion of topographic complexity, and the installation of slash.
6.6 SITE-WIDE DESIGN ELEMENTS
Topographic Complexity
Similar past projects, including those at Eel River, Tidmarsh Farms, Foothills Preserve,
Coonamessett River, and the Childs River show that topographic complexity grading produced a
diverse natural revegetation (Figure 19). Topographic complexity grading helps to create small
standing water pools providing valuable habitat for herptiles and other flora and fauna. Hummocks
and hills provide varied wetness that helps to ensure a diverse plant assemblage. Active topographic
complexity grading on a large scale can be accomplished using modified plowing, tilling and/or
harrowing equipment, or a traditional excavator bucket.
At the Marstons Mills River Site, topographic complexity will consist of a mix of microtopographic
and macrotopographic features. Microtopographic features include small hummocks and pools that
are approximately 1.5 feet higher and lower than the average bog surface respectively.
Macrotopographic features are larger constructed mounds of various shapes but up to 30 feet in
diameter. These features will also be approximately 1.5 feet higher than the average bog surface and
the material will come from bog, thus creating larger low areas well. This complexity of topography
mimics what has been observed in mature Atlantic white cedar swamps elsewhere around Cape
Cod and southeastern Massachusetts.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Figure 19. Topographic complexity constructed at Eel River (top) and Tidmarsh Farms (bottom) during construction (left) and
several years after construction (right).
Large Wood Slash Installation
Slash is defined as woody material less than 12 inches in diameter at chest height and may include
logs and logs with rootwads from smaller trees and saplings as well as branches. Slash will be
placed on the wetland surface and edges of open water ponds to provide additional aquatic and
terrestrial habitat and cover as well as topographic complexity. As these pieces of wood degrade
over time, they will develop into microtopography upon which sphagnum moss, shrubs, and trees
will grow.
Vegetation
Channel and floodplain elevations and the habitats they will harbor were designed to be resilient to
climate change and periods of saturation as well as drought. While the exact species and quantities
will be finalized during the development of the final designs, the following planting zones are
proposed: Atlantic white cedar swamp, deciduous forested wetland, upland pollinator meadow,
and experimental vegetation plots.
• Atlantic white cedar swamp – this ecosystem is being proposed for Cells A-D as well as Cells
1A, 1D, and 6. These are areas where the topographic complexity being proposed will
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
39
provide ground surfaces 1 to 2 feet above the average water surface, allowing Atlantic white
cedars to thrive on these mounds with shrubs, forbs, and sphagnum moss growing between
the trees and in other portions of the topographic complexity zones. We propose installing
up to 30,000 Atlantic white cedar seedlings, thousands of 1-gallon potted cedar trees, as well
as hundreds of 5-gallon potted cedar trees. This will allow multiple cedar trees to be
installed on all of the topographic mounds with more mature cedar trees growing above
other vegetation and dropping seeds within 1 to 2 years of installation. We anticipate up to
50% mortality for the seedlings, thus the large number of proposed individuals.
• Deciduous forested swamp – Cells 3 and 4 are proposed as deciduous forested swamp
because the active farming south of, and adjacent to, these bogs will result in extended
flooding of the proposed wetland surfaces in late fall for the cranberry harvest season as well
as for multiple months over the winter. While this flooding occurs during the dormant
periods, Atlantic white cedar trees likely would not survive this extended inundation. Other
species, however, are more able to survive this inundation and provide a healthy forested
wetland. Species likely to be included in this planting list include tupelo, swamp oak,
huckleberry, elderberry, and gooseberry.
• Upland pollinator meadow – Upland pollinator meadow is being proposed for the staging
and stockpile areas. These will be seeded with native pollinator species with no tree or shrub
plantings.
• Experimental planting zones – Cells 1B and 1C will be experimental planting zones. The
study design is still being developed, but the studies are likely to focus on the following
elements:
o Evaluating growth and success of Atlantic white cedars sourced and propagated
from various states and climate zones along the east coast of the United States. This
would be a long-term study designed to evaluate the survivability of plants in a
changing climate.
o Culturally-significant plants for Indigenous communities – this study would be done
in collaboration with the Mashpee Wampanoag Tribe and could include evaluation
of traditional planting methods, sustainable harvest, or other areas of interest to the
Tribe.
Recreation
Current recreation within the Project Site includes walking and wildlife viewing. The Project aims to
maintain the recreation opportunities by maintaining the condition of existing walking paths around
the perimeter of the bogs. Improved wildlife viewing can also be expected as a result of the habitat
restoration.
6.7 WATER QUALITY CONSIDERATIONS
Permeable Reactive Barriers
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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PRBs have been used throughout the country as a method of treating contaminated groundwater
since the mid-1990s. In general, they work by intercepting contaminated groundwater with a
reactive media that allows for groundwater to flow through while the contamination is treated
(Figure 20).
Figure 20. Permeable Reactive Barrier Diagram (courtesy of Federal Remediation Technologies Roundtable)
Throughout the region, PRBs have been used in order to intercept and remediate nitrogen in
groundwater. Requiring groundwater to flow through a carbon media, typically a wood-chip based
media or emulsified vegetable oil, enables denitrifying bacteria to respirate nitrate in the water and
convert it to nitrogen gas. The carbon media serves as a food source to support the population of
denitrifying bacteria. Examples of installed wood-chip based PRBs include at the Waquoit Bay
National Estuarine Research Reserve and along the Childs River in Falmouth. See Figure 21 for an
image of the installation of the wood-chip based PRB at the Waquoit Bay National Estuarine
Research Reserve. The key to the success of a PRB installation is ensuring the interception of
nitrogen laden-groundwater.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Figure 21. PRB Installation at Waquoit Bay (Image Courtesy of Waquoit Bay National Estuarine Research Reserve)
Site PRB Location Prioritization
In 2023, the design team proposed the installation of PRBs in select areas along the edges of the
former bog cells in order to intercept and pre-treat nitrogen in groundwater before it enters the
wetlands. The reason for this is two-fold: 1) A significant portion of the shallow groundwater inflow
(and the shallow component is what can be practically intercepted) to the restored wetlands is likely
to occur from along the edges; and 2) Taking advantage of existing perimeter bog ditches reduces
the digging required for installation, thereby lowering costs. The use of retired cranberry bogs as
wetlands/ riparian restoration projects presents a nearly ideal opportunity for enhanced nitrogen
attenuation through the use of PRBs in a cost-effective manner.
Results of the groundwater modeling analyses were used to assess the relative benefits of potential
PRB locations throughout the subject area in several ways.
• First, PRBs should be optimally sited to intercept groundwater with a maximum nitrogen
load. MODPATH particle tracking was used to evaluate the three-dimensional transport of
groundwater from source areas with high observed developed density to the periphery of
the bog complex. Figure HW6 (Appendix E) depicts the estimated groundwater capture
areas to the Site based on particle tracking results.
• Second, groundwater must be flowing near the surface in order to be intercepted by a
perimeter trench PRB. Groundwater depth was estimated by subtracting modeled particle
elevations from ground surface elevations. Particle tracking model results were utilized to
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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identify areas where shallow groundwater bound for the Marstons Mills River enters the
subject area. As groundwater flows through the aquifer additional recharge enters the water
table from the top, meaning that the water nearest the surface entered the aquifer at a
location closer than the point at which water lower in the aquifer entered. The shallowest
groundwater most likely to be intercepted by a PRB most likely originated relatively close to
the PRB in an upgradient direction.
• Third, particle tracking was also used to evaluate the local direction of groundwater flow
proximal to potential PRB locations. Optimized PRB locations extend perpendicular to the
groundwater flow direction in order to maximize the amount of water encountering the
vertical cross section of the barrier. The general hydraulic gradient surrounding the subject
area is east-southeast. The Marstons Mills River and subject area bog system influences this
general gradient by draining the immediate area, resulting in a local southwest gradient east
of the river. On the western side of the bog system, this influence results in an easterly
gradient. Areas of the perimeter which were not perpendicular, or nearly perpendicular, to
the local flow of groundwater were not prioritized for PRB placement.
• Fourth, the Cape Cod Commission’s Watershed MVP tool was utilized to estimate nitrogen
loads from specific neighborhoods within model-identified groundwater contributing areas.
In this way those contributing areas likely to contain maximum nitrogen concentration were
identified for priority targeting of PRB interception. Watershed MVP provides estimates of
the number of parcels, nitrogen load per year, and wastewater volume discharged within a
given area. We drew polygons for MVP nitrogen load analysis based on visual observation
of discrete areas of similar development density and land use. The largest nitrogen load from
those discrete polygons was identified to be for the homes bounded by Race Lane, Santuit-
Newtown Road, and School Street/Old Mill Road, just north of the subject area (Figure HW9,
Appendix E). This 340± acre area has 929 parcels and produces an estimated 9,349 kg of
nitrogen load annually, sourced primarily from the residential wastewater discharge. The
nitrogen load per acre for this neighborhood was more the double that of other
neighborhoods surrounding the groundwater contributing area. The MVP polygon
containing the Ridge Club and Holly Ridge Golf Club does not have nearly as high an MVP-
estimated nitrogen load but, due to the significant concentration of managed turf in this
polygon it was also selected as a target area for nitrogen attenuation. Figure HW9 (Appendix
E) depicts the MVP predicted target nitrogen areas.
• Fifth, forward particle tracks which encountered potential PRB locations at appropriately
shallow depths were selected and their origins identified in order to further ensure that PRB
locations intercept groundwater originating from high nitrogen load land use areas. Figure
HW10 (Appendix E) depicts identified potential PRB locations and the land areas
contributing groundwater flow likely to be intercepted by those PRB locations.
As described above, the ideal PRB location would be three-dimensionally placed in the path of
groundwater with the highest incoming concentration of nitrogen and perpendicular to the local
flow of groundwater so as to contact the highest quantity of incoming nitrogen. Based on the MVP-
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
43
based, neighborhood-scale analysis of nitrogen contributions to groundwater, the groundwater with
the highest nitrogen concentrations entering the Marstons Mills River within the Site area likely
originates between Race Lane, School Street, and Newtown Road, north of the Site (Figure HW9,
Appendix E). A PRB placed in the northwest perimeter ditch of bog Cell 1A would intercept a large
portion of the groundwater originating in this area (Figure HW10, Appendix E). Another PRB
location on the northern edge of the eastern lobe of Cell 1A would also intercept groundwater
originating from this area (Figure HW10, Appendix E). Additional nitrogen-rich recharge from this
neighborhood enters the subject area along the western edge of Cells 4 and 5 as well as the eastern
edge of Cell 3 and the reservoirs (Figure HW9, Appendix E). Perimeter ditches in these areas are not
oriented perpendicular to groundwater flow, as are the higher priority ditches in Cell 1A however,
so these are less ideal PRB locations than those in Cell 1A.
The second highest contributing area for nitrogen is the neighborhood containing the Ridge Club
and Holly Ridge golf courses, bounded by Meiggs-Backus, Newtown, Boardley, and Cotuit Roads.
Water from this source area enters the subject area in Cells 3A, 3B, and 5 (Figure HW9, Appendix E).
A PRB in Cell 5 would intercept groundwater perpendicular to the flow direction, however the
upgradient area to the potential Cell 5 location also includes lower nitrogen contributing areas south
of Newtown Road, potentially diluting the nitrogen load intercepted by a PRB at his location (Figure
HW10, Appendix E). Potential PRBs located along the western and northwestern edges of Cell 3B
(closer to Newtown Road) would intercept water originating from an area which likely contributes
more overall nitrogen (Figure HW10, Appendix E). A potential PRB along the northwest side of Cell
3A would be approximately perpendicular to local groundwater flow and is also a good candidate
for PRB installation.
Note that no priority PRB locations are shown on Figure HW10 (Appendix E) along the eastern side
of the Site. This is because the groundwater flow paths from higher nitrogen load land uses are
longer to reach the eastern side and, therefore, the highest nitrogen concentrations along those
eastern flow paths are likely to be at depths below which they could be easily be intercepted by
shallow PRBs. The shape of the existing bog perimeter ditches along the eastern side of the Site is
also more variable such that maintaining perpendicular orientation to higher nitrogen load
incoming groundwater is more difficult. This does not mean that PRBs would not potentially be
useful along the eastern border, just that they are lower priority locations than those discussed
above along the western border.
Table 3 below lists the priority PRB locations discussed above and shown on Figure HW10
(Appendix E) and includes anticipated PRB section length and refined prioritization.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Table 3. Priority PRB Locations
Priority PRB Location PRB Length (ft)
1 1A North 700
2 3B West 430
3 3B North 560
4 1A East 420
5 3A North 500
6 5 West 620
7 1B North 340
8 4 West 360
In 2024, BCWC decided to shift away from the widespread use of the PRBs as discussed above, and
focus the location of a single section of PRB on the south side of Cell A and B. The goal for this shift
was to focus funding on the other elements of the design that may serve similar functions to the
PRBs, as well as attempt to intercept nitrogen and nutrient-laden ground water entering the site
from adjacent properties to the south of Cells A and B.
Site PRB Design Discussion
The existing cranberry bog perimeter ditches can be taken advantage of in order to efficiently install
the PRBs. To install the PRBs, ditches will be over excavated in order to remove existing fine organic
materials and achieve optimal groundwater interception depth. Actual PRB dimensions will be
location specific but, conceptually, will be approximately 5 feet wide and 5 feet deep beneath
existing trench bottoms. While means and methods is traditionally left to the contractor, we
anticipate that a trench box will be used to hold the over excavated ditch open as screened
woodchips are placed in the ditch. Plates on the ends of the trench box would be placed and the
interior dewatered to facilitate woodchip placement. Screened woodchips will run from the bottom
of the ditch to at least 1 foot above the groundwater table. Filter fabric will be installed on top of the
woodchips separating them from the native or clean fill and planting soil that will overlay the PRB.
The overlying soil fill will hold the wood chips in place and prevent buoyancy after dewatering is
complete. In order to account for settling the soil will be mounded by approximately 1 foot. Figure
20 below depicts a typical cross section of PRB installation in cranberry bog perimeter ditch.
We anticipate that two crews would operate together to excavate and install each segment of PRB.
The first crew would excavate the first section of PRB trench and install the trench box to depth.
While the second crew dewatered the first segment, installed the wood chips, and covered over with
filter fabric and backfill, the first crew would simultaneously be excavating the second segment. And
so on as the process moved along each segment of PRB.
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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Figure 22. Typical section for PRB installation
6.8 RECOMMENDED CONSTRUCTION SEQUENCE
While the selected contractor will be required to develop and submit an approved work plan that
outlines their preferred sequencing for coordinating the various elements of construction, we
provide a suggested sequencing that could be followed.
• Install traffic control signs and permit signs
• Install sediment and erosion control measures
• Install water control measures
• Complete work in Cells A-D
• Complete work in Cells 1, 3, 4, and 6
• Remove water control measures
• Complete planting and seeding
• Install crossings
• Remove erosion and sediment controls once soils have become stable
• Remove traffic controls
MARSTONS MILLS RIVER BOGS ECOLOGICAL RESTORATION
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7. Engineer’s Opinion of Probable Costs
The engineer’s opinion of probable cost (EOPC) associated with the proposed designs is based on
the 75% design drawings. The cost opinion has been developed based on review of construction
costs for similar items in past projects and applicable reference cost data. The actual costs of
implementation of the project may vary from the cost opinion due to heavy construction market
fluctuations and other unforeseen factors. In particular, recent bid results (2019-2022) have seen
substantial escalation and volatility in bid pricing, which also predated the onset of COVID 19, but
accelerated once the pandemic began. The volatility has subsided somewhat in the last couple of
years, but uncertainty remains. The construction contingency partially accounts for potential
variation caused by these factors and also uncertainties regarding the design that will be resolved in
future project phases.
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8. References
Coleman, B. S., Easton, Z. M., & Bock, E. (2019). Biochar fails to enhance nutrient removal in
woodchip bioreactor columns following saturation. Journal of Environmental Management, 232,
490–498. https://doi.org/10.1016/j.jenvman.2018.11.074
Federal Emergency Management Agency [FEMA], 2014. Flood Insurance Study, Barnstable County,
Massachusetts. FIS No. 25001CV000A. Effective July 16, 2014.
Howes B.L, E.M. Eichner, R.I. Samimy, H.E. Ruthven, D.R. Schlezinger, J.S. Ramsey, (March, 2017).
Linked Watershed-Embayment Model to Determine the Critical Nitrogen Loading Thresholds for
the Wellfleet Harbor Embayment System, Town of Wellfleet, Massachusetts. SMAST/DEP
Massachusetts Estuaries Project, Massachusetts Department of Environmental Protection. Boston,
MA.
Howes B.L, E.M. Eichner, R.I. Samimy, H.E. Ruthven, D.R. Schlezinger, J.S. Ramsey, (June, 2017).
Linked Watershed-Embayment Model to Determine the Critical Nitrogen Loading Thresholds for
the Menemsha-Squibnocket Pond Embayment System, Chilmark/Aquinnah, Massachusetts.
SMAST/DEP Massachusetts Estuaries Project, Massachusetts Department of Environmental
Protection. Boston, MA.
Howes B.L, E.M. Eichner, R.I. Samimy, H.E. Ruthven, D.R. Schlezinger, J.S. Ramsey, (June, 2017).
Linked Watershed-Embayment Model to Determine the Critical Nitrogen Loading Thresholds for
the Barnstable Great Marshes-Bass Hole Estuarine System, Towns of Barnstable and Dennis,
Massachusetts. SMAST/DEP Massachusetts Estuaries Project, Massachusetts Department of
Environmental Protection. Boston, MA.
Howes B.L, E.M. Eichner, R.I. Samimy, H.E. Ruthven, D.R. Schlezinger, J.S. Ramsey, (December,
2017). Linked Watershed-Embayment Model to Determine the Critical Nitrogen Loading Thresholds
for the Plymouth Harbor, Kingston Bay and Duxbury Bay Estuarine System, Towns of Plymouth,
Kingston, and Duxbury, Massachusetts. SMAST/DEP Massachusetts Estuaries Project,
Massachusetts Department of Environmental Protection. Boston, MA.
OCM Partners, 2023: 2021 USGS Lidar: Central Eastern Massachusetts from 2010-06-15 to 2010-08-15.
NOAA National Centers for Environmental Information,
https://www.fisheries.noaa.gov/inport/item/69417.
Vismontienė, R., & Povilaitis, A. (2021). Effect of Biochar Amendment in Woodchip Denitrifying
Bioreactors for Nitrate and Phosphate Removal in Tile Drainage Flow. Water, 13(20),
2883. https://doi.org/10.3390/w13202883
A-1
Appendix A – 75% Preliminary Design Drawings
B-2
Appendix B - Historical maps and aerial photographs
C-3
Appendix C - Site Information
D-4
Appendix D – Cranberry Bog Restoration and Management:
Nutrient Removal Pilot Update within the Hamblin Bog System
(SMAST 2022)
E-5
Appendix E – Figures developed by Horsley Witten referenced
in the Basis of Design Memo
F-6
Appendix F – HydroCAD Report for the Marstons Mills River at
the outlet of the project area
G-7
Appendix G – Onsite Soil Investigation for Hamblin Bogs,
Marstons Mills (USDA NRCS 2021)
H-8
Appendix H – RSI report regarding the GPR survey of Marstons
Mills River Bogs (2021)