Case Study: Nitrogen Reduction Action Planning in Stonington2019-11-14T20:53:18+00:00

Case Study: Nitrogen Reduction Action Planning in Stonington


Stonington’s clean and healthy coastal waters support tourism, boating, fishing and arguably, the world’s best oysters. But nitrogen pollution from wastewater, fertilizers and the atmosphere, threatens the health of rivers, harbors and bays and puts community well-being at risk. Despite great progress upgrading sewage treatment plants, many of Connecticut’s coastal water ways are suffering from hypoxia, harmful algal blooms, nuisance seaweeds and devastating loss of seagrass habitat. But there is hope!

In May 2019, Approximately thirty stakeholders – including scientists, state and regional water resource managers, local citizens, business owners and elected officials – met at Mystic Seaport for a one-day workshop to share information about nitrogen pollution loads, sources and impacts in Mystic River, Stonington Harbor and Little Narragansett Bay; and to review approaches to community-based planning for cleaner coastal waters. The May 2019 workshop summary can be found here. In October 2019, approximately thirty-five stakeholders met at Mystic Aquarium to review outcomes and key recommendations of the first workshop; as well as review nitrogen reducing technology and practice options, discuss benefits and barriers to each practice, and identified potential opportunities to address water quality challenges within the subwatershed areas of Pawcatuck River, Stonington Harbor and Mystic River embayments. The October 2019 workshop summary can be found here.

The Southeastern Connecticut Clean Coastal Harbors and Bays Workshops, co-hosted by The Nature Conservancy (TNC), Clean Up Sound and Harbors (CUSH) and Mystic Aquarium, was funded in part by a grant from the Long Island Sound Futures Fund. Objectives of the grant are to 1) develop a nitrogen reduction action plan that reflects specific community needs and 2) prioritize a set of pollution mitigation projects that help restore healthy conditions in coastal waters.

Local Monitoring and Nutrient Impacts

Clean Up Sound and Harbors (CUSH) is dedicated to eliminating nitrogen pollution, bacterial contamination and plastic waste in local waters. CUSH was founded in 2007 to promote awareness about water health and began water quality monitoring in 2008 with guidance and support from University of Rhode Island Watershed Watch (URIWW). Sampling conducted in Stonington Harbor, Wequetequock Cove, Pequotsepos Cove and the Mystic River assesses dissolved oxygen, chlorophyll-A and nitrogen as indicators of eutrophication and ecological health. Data results from the first six years of monitoring were published in 2013 followed by a second report in 2014, showing thatof eleven sites, four were considered poor, five were fair and only two – in well-flushed areas- were determined to be in good health.
The 2014 report garnered a good deal of attention and CUSH was invited by Save The Sound to participate in the Unified Water Study to collect data for the LIS Report Card. In recent years, high nitrogen loads, and poor flushing have contributed to explosive growth of Cladophora macroalgae. In Little Narragansett Bay this has impacted other aquatic life, contributing to a 43% decline of eelgrass between 20132017 (Bradley, 2018).
Despite these challenges there is good news. The Stonington/Mystic area is fortunate to have citizens and municipal leaders that believe healthy water is vital for the economy and quality of life. The Town of Stonington approved funding for a study of inflow and infiltration impacting the Mystic wastewater facility and diversions to Stonington for increased efficiency. And we know from experience in Groton, Conn., recovery is possible. Until 1987, more than 3 million gallons of sewage per day was discharged into Mumford Cove from an old Navy housing facility, creating water conditions described as “pea soup” green (University of Connecticut et al 2007). Following years of appeals after a 1971 lawsuit brought by the Mumford Cove Association, the Town of Groton redirected the wastewater away from Mumford Cove in 1987. The following year, Ulva seaweed in the cove declined by 88% and fifteen years later in 2002, clean coastal water was restored enabling natural eelgrass to rebound and flourish.

From Chris Freeman, President of Clean Up Sound & Harbors (CUSH), with Remarks from First Selectman Rob Simmons

Nitrogen Loads and Sources

The Long Island Sound Nitrogen Loading Model (LIS NLM) developed by Dr. Jamie Vaudrey (2016) and supported by the Long Island Sound Study, employs land use data coupled with embayment characteristics to estimate nitrogen loads from human activities and identify the LIS harbors and bays at greatest risk for exhibiting symptoms of eutrophication such as low dissolved oxygen, harmful algal blooms, macro algae and eelgrass loss. Vaudrey’ s research indicates coastal embayment watersheds contribute about 20% of the total nitrogen load to LIS. While this represents a fraction of the overall nitrogen load to LIS, eutrophication impacts in restricted harbors, bays and rivers can be significant due to limited flushing. Additionally, the sources and relative contributions of nitrogen pollution from wastewater, fertilizer and atmospheric deposition (rain and dust) entering harbors and bays varies widely between watersheds, which underscores the importance of using a variety of tools and options to help communities target pollution with effective solutions.
The LIS NLM indicates about half of the nitrogen from human activities in both the Pawcatuck and Mystic River watersheds comes from wastewater, but the total loads are significantly different. In the Pawcatuck River watershed, roughly 30% or 70,000 kg N/yr is discharged from sewage treatment plants, while the calculated load from septic systems is about 48,000 kg N/yr. In the Mystic River watershed, wastewater from sewage treatment represents 26% or 8,000 kg N/yr and septic systems about 25% or 7,800 kg N/yr.
The LIS NLM can be used to develop scenario maps that estimate potential nitrogen load reductions associated with various actions such as reducing fertilizer applications and upgrading wastewater technologies. Scenario maps are useful for helping people visualize where different actions might be feasible and have an impact.

From Dr. Jamie Vaudrey, Associate Professor of Marine Science, University of Connecticut

Critical Steps for Nitrogen Management

Telephone surveys conducted by TNC in Stonington, Mystic, Groton and Pawcatuck in 2017 indicate residents depend upon clean coastal waters for recreation, tourism, boating, fishing and plentiful seafood. Additionally, they are willing to take or support actions that protect and restore healthy water quality – such as reducing fertilizer use and requiring wastewater technology upgrades for new and redevelopment.
Critical steps in developing a Nitrogen Action Plan include assessing current pollution loads and setting nitrogen limits – or endpoints – that protect ecological health in coastal rivers, harbors and bays. Building the plan requires engaging and communicating with stakeholders to ensure there is support for technology and practice solutions. By identifying the sources of land-based nitrogen pollution from
human activity, community members and leaders can apply solutions where they will be most effective. Additionally, the plan should identify the cost of solutions and establish mechanisms to advance action – such as policies, incentives and finance methods. Tracking reduction progress and monitoring water quality conditions allows the plan to be adjusted, updated and improved to restore and sustain waters, now and for future generations.

From Holly Drinkuth, Director of Outreach and Watershed Projects, The Nature Conservancy 

Nitrogen Loading Maps

Nitrogen loading maps estimate total anthropogenic nitrogen load by subwatershed and indicate relative contribution from atmospheric deposition, fertilizers and wastewater.

By Kevin Ruddock, GIS Manager at The Nature Conservancy in Rhode Island

Potential Solutions

Representatives within the subwatershed areas of Pawcatuck River, Stonington Harbor and Mystic River embaymentss convened to learn about emerging nitrogen pollution science and management approaches, clarify data and research needs, and identify action steps for implementing nitrogen reduction strategies.