Final Draft West and East Monponsett Pond System Total Maximum Daily Loads for Total Phosphorus

Final Draft West and East Monponsett Pond System Total Maximum Daily Loads For Total Phosphorus (CN 446.1) COMMONWEALTH OF MASSACHUSETTS EXECUTIVE OFFICE OF ENVIRONMENTAL AFFAIRS KATHLEEN A. THEOHARIDES, SECRETARY MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL PROTECTION MARTIN SUUBERG, COMMISSIONER BUREAU OF WATER RESOURCES KATHLEEN BASKIN, ASSISTANT COMMISSIONER January 2021 This information is available in alternate format. Contact Michelle Waters-Ekanem, Director of Diversity/Civil Rights at 617-292-5751. TTY# MassRelay Service 1-800-439-2370 MassDEP Website: www.mass.gov/dep Printed on Recycled Paper Final Draft West and East Monponsett Ponds, Stetson Pond and White Oak Reservoir Total Maximum Daily Loads for Total Phosphorus MassDEP DWM TMDL Report CN 446.1 Key Features: Total Phosphorus TMDL for West Monponsett Pond (Segment ID #MA62182), and East Monponsett Pond (MA62218), Stetson Pond (MA62182) and White Oak Reservoir (MA62157) in Halifax, Hanson, and Pembroke MA Data Sources: MassDEP data, MassGIS landuse, Data Mechanism: Massachusetts Surface Water Quality Standards, Ambient Data, Landuse, and LLRM suite of Models Control Measures: Cranberry Bog BMPs, Septic System Upgrades, Stormwater Management, Aluminum Treatment. Massachusetts Department of Environmental Protection Division of Watershed Management 8 New Bond Street Worcester, MA 01606 http://www.mass.gov/dep/water/resources/tmdls.htm. DISCLAIMER References to trade names, commercial products, manufacturers, or distributors in this report constituted neither endorsement nor recommendations for use by the Division of Watershed Management. Map this page made via ggmap, courtesy Kahle and H. Wickham 2013 Cover photo credit: Police Chief Ted Broderick, Halifax, August 20, 2015. 2 Executive Summary The Massachusetts Department of Environmental Protection (MassDEP) is responsible for monitoring the waters of the Commonwealth, identifying those waters that are impaired, and developing a plan to bring them back into compliance with the Massachusetts Surface Water Quality Standards. The list of impaired waters also referred to as Category 5 of the State Integrated List of Waters or the “303d list” identifies river, lake, and coastal waters and the cause for impairment. All impaired waters listed in Category 5 require the development of a Total Maximum Daily Load (TMDL) report. Once a water body is identified as impaired, MassDEP is required by the federal Clean Water Act (CWA) to essentially develop a “pollution budget” designed to restore the health of the impaired body of water. The process of developing this budget, generally referred to as a TMDL, includes identifying the source(s) of the pollutant from direct discharges (point sources) and indirect discharges (non-point sources), determining the maximum amount of the pollutant that can be discharged to a specific water body to meet water quality standards, and developing a plan to meet that goal. This report develops total phosphorus TMDLs for an interconnected set of four waterbodies (West and East Monponsett Pond, Stetson Pond and White Oak Reservoir) in the towns of Hanson, Halifax, and Pembroke Massachusetts. East and West Monponsett Pond, Stetson Pond, and White Oak Reservoir are listed as impaired (Category 5), on the "Massachusetts 2016 Integrated List of Waters" for nutrient related impairments (MassDEP, 2019). East Monponsett Pond (Segment MA62218) is listed as impaired for Chlorophyll-a and Harmful Algal Blooms. West Monponsett (Segment MA62119) is listed as impaired for Chlorophyll-a, Harmful Algal Blooms, Total Phosphorus and Transparency/Clarity. Stetson Pond (Segment MA62182) is listed as impaired for Dissolved Oxygen (DO), Harmful Algal Blooms, and Total Phosphorus (TP). White Oak Reservoir (Segment MA62157) is listed as impaired for Nutrient/Eutrophication Biological Indicators. Stetson Pond and White Oak Reservoir were determined to be impaired by excess algal growth and nuisance aquatic plants (duckweed), respectively, based on data analyzed in this report. Some of the ponds are listed for other non-pollutant related impairments (TMDL not required) and these include Stetson Pond which is listed for non-native aquatic plants; East Monponsett Pond listed for non-native aquatic plants and has a completed TMDL for Mercury in Fish Tissue (EPA#33880); West Monponsett Pond MA62119 is listed for non-native aquatic plants. This report will satisfy the requirement of a phosphorus TMDL for each of the above waterbodies. In order to prevent further degradation in water quality and to ensure that each lake meets state water quality standards, the TMDL establishes phosphorus limits for the lakes and outlines actions to achieve that goal. All four waterbodies covered in this TMDL are classified as Class A waterbodies as well as having been designated Public Water Supply and Outstanding Resource Waters (ORWs) (MassDEP 2007). The four waterbodies flow, via an underground pipe, from East Monponsett to Silver Lake (Pembroke, MA) which is the surface water supply for the City of Brockton. During diversions (mainly in October through May) water flows regularly in the reverse direction and 3 flows backward from West Monponsett to East Monponsett, potentially drawing the cyanobacteria and nutrients into Silver Lake. Action is being taken to address the cyanobacterial blooms observed in West and East Monponsett Ponds and the upstream waterbodies that are tributary to those ponds. The Lake Loading Response Model (LLRM) suite of lake models was used for this TMDL. The LLRM is a spreadsheet based model which uses an annual steady state suite of models to estimate nutrient loadings. These estimated nutrient loadings along with pond morphometric and physical characteristics are then used to predict in-pond nutrient concentrations using a suite of well accepted lake models for phosphorus predictions. The successful calibration of the model was based on relatively high nutrient export rates from specific landuses that discharge directly to surface waters (cranberry bogs, stormwater and natural forested wetlands), combined with estimates of export from septic systems and internal sediment recycling of phosphorus. These estimates for each waterbody were simultaneously adjusted with the Lake Loading Response Model (LLRM) suite of lake models until they approximated the observed in-lake surface concentrations in each lake. The major sources of phosphorus to the lakes were cranberry bogs, runoff from developed areas, internal release from sediments, and natural wetlands. Ignoring sediment sources, the largest controllable watershed sources of phosphorous are cranberry bog inputs and runoff associated with residential development. In the case of West Monponsett Pond, internal loading or recycling of phosphorus from lake sediments is a major source of phosphorus during the summer growing season. Implementation is already underway to address the cranberry bog inputs. The large commercial bogs north of Stetson Pond were retired in 2008 and that pond already shows a reduction in TP concentrations. The Morse Brothers Winebrook bogs and “bog #19” near West Monponsett Pond and White Oak Reservoir have implemented reduced phosphorus fertilizer rates as recommended by the University of Massachusetts (UMass) Cranberry Experiment Station. West Monponsett Pond has also shown significant reductions in TP concentrations coincident with the fertilizer reductions. In addition, a Section 319 grant (#12-02/319) was previously awarded in 2012 to assist in implementation and monitoring of new experimental filters for cranberry bog discharge waters, with monitoring being conducted by the UMass Cranberry Station. Funding support to aid implementation of this TMDL is available on a competitive basis under various state programs including the U.S. Environmental Protection Agency (EPA) Section 319 Grant Program administered by MassDEP. It is recommended to first reduce external loads to the extent possible before addressing the internal loads, but due to health concerns regarding the potentially toxic cyanobacterial blooms in West Monponsett, the Town of Halifax funded treatments with a light dose of aluminum in 2013, 2015, and 2016. With 319 funding, the Town of Halifax applied aluminum doses in 2017, 2018 and 2019. Light aluminum doses were applied in small amounts over the summer months to avoid potential impacts to the rare state listed freshwater mussels in the pond. The sediment source of phosphorus is presumably due to historic inputs of phosphorus, largely from anthropogenic sources. Implementation will include continued effort to reach out to remaining cranberry growers to use the most current recommended practices on their bogs. Implementation can be achieved by a combination of best management practices (BMPs) including reducing the phosphorus fertilizer 4 rates, reducing volumes of discharge water and reducing concentrations of total phosphorus in the discharge water. Further implementation of stormwater and septic system upgrades are encouraged. Aluminum treatment of West Monponsett Pond totals an applied dose of 50 g/m2. Treatment of the other ponds in the system is also encouraged with potential funding through the Section 319 Grant Program. The Town of Halifax received a Section 319 grant in 2017 to help fund alum treatment of West Monponsett through 2019. Additionally, a substantial reduction in TP loads (50% - 60%) from stormwater will be required for Stetson Pond, East Monponsett, White Oak Reservoir, and West Monponsett Pond watersheds

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