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Project Narrative
Long Pond Marstons Mills Floating Treatment Wetland Pilot Study
Prepared By: The Town of Barnstable Department of Public Works
June 2023
1.0 INTRODUCTION
The Town of Barnstable Department of Public Works is requesting approval to perform a Floating
Treatment Wetland Pilot Study in Long Pond Marstons Mills for the purposes of evaluating the their
effectiveness on phosphorus removal. Floating Treatment Wetlands are an innovative technology for
nutrient removal and therefore, we are requesting this project be permitted under the guidelines for
310 CMR 10.05(11) Permitting of Test Projects. According to the Mass Mapper, Long Pond MM does not
have Rare and Endangered Species Habitat or Potential Habitat (Figure 1) and is not within salt marsh or
seagrass beds. Herewithin is a narrative describing the technology, installation, monitoring, and removal
plan.
Project Site
Long Pond is located in Marstons Mills, MA with coordinates 41.67132° N, -70.44638° W. Long Pond is a
Great Pond and accessed by the public via the Town of Barnstable Conservation Area located at 425
Santuit-Newtown Road, Marstons Mills, Massachusetts.
2.0 PROJECT DESCRIPTION
Background
Long Pond in Marstons Mills is a 50-acre Great Pond with a maximum depth of 7.4-meters. This pond
has experienced cyanobacteria blooms each year from 2018-2022, often resulting in use restrictions that
last through the majority of July and August. The Department of Public Works (DPW) retained the
Coastal Systems Program at UMass Dartmouth School for Marine Science and Technology (SMAST) to
conduct a nutrient diagnostic assessment of Long Pond and develop a management plan to address
water quality issues (Attachment A). This study found that Long Pond is impaired due to excess
phosphorus loading from leaching septic systems in the contributing watershed. In order to improve
water quality in Long Pond, a phosphorus reduction in the amount of 6-9 kg P/year (depending on
groundwater levels) is necessary to reach a target phosphorus concentration of 10 ug/L in the pond.
The Town has planned to provide sewer service to these homes in Phase 3 of the Comprehensive
Wastewater Management Plan (CWMP, 2041 – 2050). In the interim of sewer being available, the Town
plans to pilot 500 square feet of Floating Treatment Wetlands to assess the effectiveness of Floating
Treatment Wetlands on phosphorus removal in Long Pond Marstons Mills.
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Floating Treatment Wetlands Background
Floating Treatment Wetlands (FTWs) have been documented to remove phosphorus from waterbodies
at varying rates, ranging from 0.02 kg/100sq-ft/year1 up to 16 kg/100-sq-ft/year2. The estimates of
phosphorus removal by FTWs varies substantially and largely depends on the environmental conditions
of the location they are deployed. Factors that influence phosphorus removal by FTWs:
Available phosphorus in the water column
Length of growing season
Water flow
Type of plants
On the Princeton Hydro website, they indicate that 250 ft2 FTWs can remove up to 15-lbs (6.8-kg) of
phosphorus per year. Therefore, a 500-ft2 FTW may be able to remove up to 13.6-kg, if ideal conditions
exist. Note, Princeton Hydro did not provide information on the “ideal conditions” to achieve the
reported level of phosphorus removal, so it is unclear if these results could be achieved in Long Pond.
A more robust study on phosphorus removal in FTWs was conducted in the Charles River Lake Basin,
Boston, MA by Northeastern University. The findings of this study found that these FTWs were able to
remove 2-7 grams of phosphorus per m2 of FTW per year (2-7g P/m2 FTW/year). The background
conditions of the Charles River were:
60-ug/L Total Phosphorus;
Minimal flow in this area of the Charles River lower basin;
FTWs deployed year round for two years, with the bulk of the growing season between May –
September.
Based on the research completed by Rome McNamara at Northeastern University, a 500-ft2 FTW in Long
Pond may be able to remove between 0.1 to 0.35 kg of phosphorus per year, if similar conditions exist.
Given the variance in the results of research as noted above, the Town felt that by piloting 500-ft2 FTW
in the Long Pond Marstons Mills the Town will be able to evaluate FTW performance in Long Pond for
the purposes of determining if FTWs can effectively reduce the phosphorus available for cyanobacteria.
Deployment Description
Floating Treatment Wetlands are available from several vendors and in various sizes and shapes. The
media is typically made of recycled plastic that floats and can be planted with local native plants and
deployed in the pond at a desired location. Literature indicates the media will last at least 10 years and
up to 20 years, depending on local weather conditions. The FTW media would be delivered to the Long
Pond Farms Association Beach, where it would be planted with plants listed in Table 1. Once fully
planted, it would be towed by boat to the North end of the pond using a boat and anchored at the
1 McNamara, Rome. PhD Dissertation, 2022. Northeastern University.
2 Princeton Hydro Webpage Accessed Nov. 28, 2022.
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corners using cinder blocks in the locations indicated by Figure 2, which are at least 4-feet deep up to 7-
feet deep. Approximately 276-sqft of FTW will be deployed in location 1 and ~184 sq-ft of FTW
deployed in location 2. An additional ~42sq-ft of unplanted FTW media will be deployed in either
location 1 or 2 to serve as a control. The two locations have been selected to evaluate how well the
FTWs stay in place. Location 1 more out of the way of homeowners and boaters, but is more exposed to
southern winds, whereas location 2 is more protected. The water quality conditions of these two
locations are anticipated to be similar.
Considering the information available in the Long Pond Management Plan and annual cyanobacteria
monitoring program, it is recommended the Floating Treatment Wetlands be deployed in the northern
portion of the pond (Figure 2). This area of Long Pond experience inputs of phosphorus from the
adjacent watershed and has higher levels of phosphorus compared to the southern end of Long Pond.
Table1. Anticipated plantings for the Floating Treatment Wetlands, subject to availability.
Common Name Latin Name
Common Rush Juncus effusus
Rose Mallow Hibiscus moscheutus
Blue Vervain Verbena hastata
Sweet Flag Acorus Americanus
Soft Stem Bullrush Schoenoplectus tabernaemontani
Lurid Sedge Carex lurida
Pickerelweed Pontederia cordata
Mountain Holly Ilex mucronata
Environmental Monitoring
It is assumed that it will take two full growing seasons for the Floating Treatment Wetlands to reach full
grow out on the media. At which point, the plants biomass would be harvested, thereby removing
phosphorus from Long Pond. To determine the phosphorus removed by the FTWs, the FTWs will be
monitored at the beginning and end of each growing season for two growing seasons for the
phosphorus content and subsequently phosphorus mass contained in the plant shoots, plant roots, soil,
and matrix. Sample collection for the plant shoots, plant roots, soil, and raft matrix will occur:
1. prior to the installation of the floating wetland (spring – YR1),
2. after one growing season (fall – YR1),
3. at the beginning of YR2 growing season (spring – YR2), and
4. after YR2 growing season (fall – YR2).
Post-installation sampling will be based on collection of 5 samples collected from 0.1-m2 quadrants
placed to be representative of plant growth on the raft. During the growing season there will be periodic
observations made for plant survival and growth. At the end of year two a summary of the floating
treatment wetland phosphorus removal will be provided and the feasibility of scaling up the FTWs will
be discussed.
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Post-Pilot Study Removal and Restoration
If at any point during the pilot study, it is determined that the Floating Treatment Wetlands need to be
removed, they can be removed by using a 12-ft jon boat with a 3 horsepower motor, or similar, and at
least two people. The cinder blocks anchoring the wetlands would have to be pulled from the bottom
and placed on the boat and the FTW towed back to the Long Pond Farms Association Beach, where the
plants could be harvested and placed in a truck bed and floating media dewatered and placed on a
trailer or truck bed to be hauled off site. This process would then be repeated for each individual
module deployed, until all FTWs have been removed. No additional restoration will be required since
there will not be significant disturbance to the land under water or buffer zone areas.
3.0 APPLICABLE REGULATIONS REQUIRING NOI
Long Pond Marstons Mills is subject to the Wetlands Project Act Massachusetts General Law Chapter
131 Section 40 and Chapter 237 of the Town of Barnstable General Ordinance, requiring an Order of
Conditions from the Barnstable Conservation Commission. Floating Treatment Wetlands are an
innovative technology for nutrient removal and therefore, we are requesting this project be permitted
under the guidelines for 310 CMR 10.05(11) Permitting of Test Projects.
This project does not include the creation of a dock, pier, or expansion of any structure within Long
Pond and will not include work within the 100-foot buffer zone to Long Pond. Therefore, is not subject
to Chapters 703 and 704 of the Town of Barnstable General Ordinances. However, the project does
deploy water dependent Floating Treatment Wetlands that will float on the pond surface.
This project does not impact Priority or Estimated Areas of Rare Habitat as listed on the current National
Heritage Endangered Species Map (NHESP) or anadromous fish runs.
4.0 ASSESSMENT OF RESOURCE AREA IMPACTS
This project will result in a temporary conversion of approximately 500-sqft of open water to Floating
Treatment Wetlands (Figure 2) for the purposes of piloting the innovative technology to determine
phosphorus removal of Floating Treatment Wetlands. It is anticipated the FTWs will remove phosphorus
from the water, thereby improving water quality in Long Pond.
References
J-Tech, an Alliance between Jacobs Engineering and Tetra Tech, Inc. C-43 West Basin Storage Reservoir
Water Quality Feasibility Study. Prepared for South Florida Water Management District. April 3, 2020.
McNamara Buck Rome. Dissertation: From Water Quality to River Health. Northeastern University.
December 2022.
Tom Schueler, Cecilia Lane, and David Wood. Recommendations of the Expert Panel to Define Removal
Rates for Floating Treatment Wetlands in Existing Wet Ponds. July 26, 2016.
Long Pond MM Floating Treatment Wetland Pilot Study
DEP Seagrass
Tidelands Jurisdiction Chapter 91 Marsh
Boundary - seaward
NHESP Priority Habitats of Rare Species
NHESP Estimated Habitats of Rare
Wildlife
Property Tax Parcels
1,000.00
This map is for illustration purposes only. It is not
adequate for legal boundary determination or
regulatory interpretation. This map does not represent
an on-the-ground survey. It may be generalized, may not
reflect current conditions, and may contain
cartographic errors or omissions.
Parcel lines shown on this map are only graphic
representations of Assessor’s tax parcels. They are
not true property boundaries and do not represent
accurate relationships to physical objects on the map
such as building locations.
167083
Feet
feetApprox. Scale: 1 inch =83
Legend
Town of Barnstable GIS Unit
367 Main Street, Hyannis, MA 02601
508-862-4624
gis@town.barnstable.ma.us
Map printed on:4/21/2023
Road Names