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Sheri Caseau
Water Resources Planner
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Wastewater and Stormwater Management

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Wastewater

Wastewater is the largest locally controlled source of nitrogen pollution affecting our ground and surface waters. Coastal salt ponds are more sensitive to nitrogen than people, so we need additional measures to limit nitrogen pollution beyond the requirements for human health. Wastewater leaving a conventional septic tank contains about 35 parts per million of nitrogen.

One approach to removing nitrogen in groundwater before it reaches a pond is to install a permeable reactive barrier (PRB) – an underground layer of organic material that intercepts nitrogen at a key location. A PRB that the MVC helped install near Lagoon Pond in 2020 has proven highly effective, with downgradient testing showing more than a 90% reduction. In December 2021 Tisbury Waterworks Inc. and the MVC hosted Jessica Thompson of the UMass Dartmouth School for Marine Science and Technology to discuss the project. You can see the recorded zoom meeting here. Thomson discusses what PRBs are, how they can benefit a nutrient-rich ecosystem, and why others might be interested in installing one themselves.

The MVC is currently working to install a second PRB on the Oak Bluffs side of the Lagoon, with funding through the Southeast New England Program (SNEP) Network.

Photo: Installing a PRB near Lagoon Pond in 2020.

Learn More about Wastewater Solutions

Learn More about Wastewater

Wastewater Management treatment plant

Treating wastewater properly is essential to both human and environmental health. The average household produces about 60,000-65,000 gallons of wastewater each year, or about 170-180 gallons per day. This includes regulated pollutants such as nitrogen and pathogens (viruses and bacteria), and an increasingly complex cocktail of pharmaceuticals, personal care products, and hazardous chemicals that are flushed into the system.

Wastewater from each residence with a Title 5 septic system on the Island annually releases about 13.5 pounds of nitrogen into the groundwater, which ends up in downgradient ponds unless we act to reduce or intercept it first.

The MA Department of Environmental Protection regulates wastewater treatment, setting standards for the installation and operation of facilities at all scales, with a focus on public health. Local boards of health may adopt regulations that are more restrictive than the state regulations.

Treating Wastewater on the Island

There are four basic approaches to treating wastewater, all of which meet state health protection requirements but have very different levels of effectiveness when it comes to removing nitrogen.

Centralized wastewater treatment facilities fed by sewage collection systems are most suitable for higher-density areas and can remove about 95-97% of the nitrogen.
Innovative/Advanced (I/A) systems are capable of removing about 90% of the nitrogen in wastewater.
- Approved I/A technologies
- Massachusetts Alternative Septic System Technology Center (MASSTC)
Satellite treatment plants are most suitable for outlying, higher-density areas and remove at least 75% of the nitrogen.
Cluster treatment facilities, for groups of homes, typically remove about 50% of the nitrogen, but with additional advanced treatment will remove about 75-90%.
Individual on-site treatment systems, as regulated by boards of health under Title 5 (the State Sanitary Code), remove about 40-90% of the nitrogen through biological treatment.

Wastewater from many properties (about 2,450 as of 2023) is treated in one of the Island's five wastewater treatment plants (Edgartown, Oak Bluffs, Tisbury, MVY Airport, and Wampanoag Tribal Housing), but the vast majority of properties (more than 90%) have onsite treatment in the form of cesspools, older septic systems, newer Title 5 systems, and Innovative/Alternative systems.

Town boards of health enforce Title 5 to ensure wastewater disposal by septic systems protects human health, although Title 5 does not focus on surface-water impacts.

Wastewater regulations often serve to limit the number of buildings, or at least the number of bedrooms, allowed in certain areas. A major concern with improving wastewater treatment is that it could open up these areas to additional development. We must carefully consider the need for wastewater treatment to be “growth-neutral,” and for zoning regulations to prevent inappropriate development.

When reviewing proposed Developments of Regional Impact, the MVC carefully examines each proposal with respect to its impact on nitrogen-sensitive watersheds. The MVC also works with Island towns to evaluate the need to expand or upgrade their sewage treatment systems.

Innovative Alternative (I/A) Septic Systems

These are septic systems designed or constructed outside the typical parameters of Title 5. A conventional system has a septic tank, a distribution box or dosing mechanism, a soil-absorption system, and a reserve area. Some examples of I/A systems are recirculating sand filters, aerobic treatment units, peat filters, humus/composting toilets, and intermittent sand filters. Some I/A technologies are used to reduce nitrogen in nitrogen sensitive areas. (See links above for more info.)

Further Mitigation

There are many other ways to mitigate nitrogen before it gets to a coastal pond or to reduce it once it is in the pond.

Shellfishing
Phytoremediation
Constructed Wetlands
Permeable Reactive Barrier
Floating Islands
Inlet Openings

Photo: The Edgartown Wastewater Treatment Facility.

MVC Innovative/Alternative Conference (2016)

The MVC hosted an Innovative/Alternative Conference in May 2016. The goal was to bring together industry professionals, scientists, policymakers, and local stakeholders to discuss the issue of nutrient pollution in our ponds and estuaries, and to explore various technologies and solutions.

Presentations

Morning Session Presentation

Michael Giggey, Cleaning up Our Waters
Dr. Brian Howes, MEP Process and findings
George Heufelder, Alternative Septic System Test Center

Afternoon Session Presentation

Rob Zimmerman, Kohler CLASS
Gary Rubenstein, Permeable Reactive Barriers
Dave Thompson, Traditional Sewers
Mike Moreau, FAST I/A Systems
Rick Karney, Shellfish Aquaculture
Mollie Caliri and Andrew McBrearty, Amphidrome
Dave Grunden, Inlet Opening and Constructed Wetlands
Michael Loberg, Tisbury Board of Health Regulations

Stormwater

Stormwater is the water generated from impervious surfaces when it rains. Unless it is mitigated, stormwater carries silt, organic matter, bacteria, nutrients, metals, and petroleum products into nearby fresh and coastal waters. This may contribute to water quality impairment via nutrient and bacterial contamination, along with other impacts. Stormwater is a visible, often easily corrected source of water pollution.

Stormwater impacts can be eliminated or at least reduced by having rain and runoff infiltrate directly into the ground (rather than over the surface), where it is filtered and treated, and replenishes groundwater resources.

Low Impact Development (LID) is an innovative stormwater management approach that avoids costly conventional techniques to pipe, treat, and dispose of stormwater. Instead, it replicates the pre-development hydrology of the site by using design techniques modeled after nature to filter, store, evaporate, and detain runoff close to its source. Techniques include porous pavers, pervious asphalt, bioretention swales, grassed infiltration areas, and rain gardens. LID guidelines should be incorporated into permitting and project approvals at town and MVC levels to minimize the generation of stormwater.

The MVC has partnered with the UNH Stormwater Center to implement stormwater mitigation solutions at several sites on the Island.

Documents and Links

Native Plants in Buffer Strips: Also for use in residential or low-maintenance landscapes. See also the Plant Local MV webpage, and the Polly Hill Plant Selection Guide below.
Water Table Data (2008): Summarizes the data collected from an Islandwide network of nine monitoring wells in 1992-2008.
MVC Water Quality Policy: Outlines the standards that the MVC uses to evaluate the proposed wastewater systems for Developments of Regional Impact.
Polly Hill Arboretum Plant Selection Guide: A resource intended to guide municipalities, landscape architects, and others toward plants with excellent horticultural, ecological and adaptive characteristics that are suitable for landscape uses on the Vineyard.
Coastal Stormwater Management through Green Infrastructure: A handbook to help coastal communities in the Massachusetts Bays Program (MassBays) area incorporate green infrastructure into their stormwater management planning.
University of New Hampshire Stormwater Center: Information on cutting-edge research on stormwater management, as well as resources for the stormwater management community.
MA Department of Environmental Protection: Information about on-site wastewater disposal systems, treatment plants, water reuse, and how stormwater affects water resources.
MA Alternative Septic System Technology Center: Evaluates the performance and costs of Innovative/Alternative (I/A) wastewater disposal technologies.

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