Massachusetts Agency Seeks Comment on Plans to Clean Up Nantucket, Polpis Harbors

The Massachusetts Department of Environmental Protection (DEP) will hold a public meeting on Oct. 9 to seek comment on a draft document identifying the need to limit and reduce the nutrient nitrogen in the coastal waters of Nantucket and Polpis Harbors on the Island of Nantucket.

The embayment restoration plan for these estuaries, formulated by DEP and the University of Massachusetts/Dartmouth School for Marine Science and Technology (SMAST), is proposed as part of a comprehensive six-year, collaborative project intended to improve estuarine water quality in 89 embayments along the southeastern Massachusetts coastline.

Nantucket and Polpis harbors are currently impaired by excess nutrients, mainly nitrogen. These embayments are listed on the 2004 Massachusetts Integrated List of Waters as impaired by nutrients and pathogens.

Steady population growth and increased land use development, particularly during the last several decades in southeastern Massachusetts, has created an overabundance of nitrogen in the region's harbors, bays and estuaries. The primary controllable source of nitrogen is stormwater and wastewater discharged from septic systems. Leaching lawn fertilizers, discharges from agricultural land uses, nutrient-rich sediments, and atmospheric deposition also contribute varying quantities of nitrogen.

At the public meeting, DEP staff will present a draft Total Maximum Daily Load (TMDL) for limiting nitrogen to the amounts that the water bodies can absorb without violating water quality standards and impairing uses such as fishing and recreational activities. The plan calls for reducing watershed sources of nitrogen by up to 57 percent. Most of the reductions will be from better treatment and handling of runoff and wastewater, but nitrogen from fertilizer use should also be controlled wherever possible.

"This cleanup plan charts a new path for enhancing recreational opportunities and restoring ecological health on Nantucket," DEP Commissioner Laurie Burt said. "Nantucket officials have shown great initiative and commitment by providing the leadership necessary to improve future water quality on the island."

The major components of this effort included several years of chemical, physical and biological studies within the Nantucket Harbor System, and the use of a dynamic water quality model that linked the watersheds and embayments to determine the present sources of nitrogen and the loading rates from each, the nitrogen concentrations in each embayment, the nitrogen concentrations that will result in the restoration and protection of the embayments, and the target nitrogen loading rates that will achieve those protective concentrations. This watershed modeling and TMDL analysis will serve as a planning tool for communities to implement new comprehensive wastewater management strategies in order to improve estuarine water quality.