Wastewater and Advocacy

The recent history of the Assabet River and of OARS' advocacy for the river is intertwined with the history of wastewater treatment. The four municipal wastewater (sewage) treatment plants that discharge to the Assabet River are: Westborough (also serves Shrewsbury), Marlborough Westerly (also serves Northborough), Hudson, and Maynard. Discharges from wastewater treatment plants are governed under the Clean Water Act, through NPDES (National Pollutant Discharge Elimination System) Permits, issued by the federal EPA and the state DEP. OARS advocates for wastewater treatment levels that will allow the river to meet its Class B "fishable and swimmable" designation.

There are wastewater discharges to the Sudbury River and Concord River as well. The Marlborough Easterly wastewater treatment plant discharges to Hop Brook, a tributary of the Sudbury River, and the Town of Wayland has a municipal plant that discharges directly to the river. The towns of Concord and Billerica both have municipal wastewater treatment plants that discharge directly to the Concord River.

Recent milestones for the Assabet
2004: After a six-year process, a major study of the river, the Assabet River Total Maximum Daily Load (TMDL) for Total Phosphorus, was completed. The TMDL found that the four municipal wastewater treatment plants are the major contributors of nutrients (phosphorus and nitrogen) and that phosphorus is likely the limiting nutrient and hence the main target of regulation.

2005: Based on this study, the EPA and the state DEP issued new permits for the four major wastewater treatment plants calling for phased reductions in phosphorus discharge concentration. OARS commented on these permits and, in 2005, appealed the permits for Westborough, Marlborough and Maynard to ensure that they would meet water quality standards. These appeals were resolved and the municipalities moved forward to up-grade their treatment plants to meet stringent pollutant discharge standards contained in the Phase 1 permits. All the municipal facilities that discharge to the Assabet River are now required to meet a new seasonal phosphorus limit of 0.1 mg/L beginning in 2010/2011. This is a tremendous win of national significance for the Assabet River.

2009: The discharge permit for the Marlborough Westerly treatment plant, which also serves Northborough, was modified in November 2009 to allow a 44% increase in its wastewater discharge to the Assabet River. OARS appealed the permit modification to the state DEP and the U.S. EPA's Environmental Appeals Board, and on February 22, 2010 the EPA withdrew its approval of the City of Marlborough's increase in wastewater discharge. With this appeal resolved, all the wastewater treatment plants were ready to move forward with upgrades. (About this appeal).

2012: State-of-the-art phosphorus removal technologies had been installed in all four plants and the aging plant equipment and buildings had been upgraded. By spring of 2012 all four plants were meeting the discharge limits required in their 2005 NPDES permits: 1.0 mg/L Total Phosphorus in the winter and 0.1 mg/L Total Phosphorus in the growing season. This is a major achievement, and OARS' water quality and biomass monitoring program will track the expected improvements in the river. For a description of treatment plant upgrades, read the articles from past OARS newsletters: July 2006, June 2007

The Future: While the science tells us that in order to achieve a truly healthy river, wastewater facilities will need to reduce their phosphorus discharge to levels of 0.05 mg/L or less-- these upgrades are big step forward. Click here to read the letter from EPA and DEP regarding future (Phase 2) permit limits. Although the Assabet is among those in the forefront of the trend toward low phosphorus discharges, we believe it is indeed a trend. As the cost of technologies for meeting very low phosphorus limits comes down, and the users of these technologies establish successful track records, the agencies will be more willing to impose phosphorus limits sufficient to achieve water quality standards in receiving waters. A facility in Syracuse, New York that discharges to a lake was scheduled to meet a very low phosphorus limit-- 0.02 mg/L-- beginning in 2012.

The role of dams
Unfortunately stringent discharge limits may not solve the problem on their own. The TMDL stated that in addition to reducing phosphorus in treatment plant effluent, the recycling of phosphorus from the river' sediments would need to be reduced by 90%. The Assabet behaves along much of its length more like a string of lakes than a river. Home to "pond" fish species that don't require flowing water, the Assabet is dammed in nine places. The areas behind the dams, known as impoundments, resemble long ponds. For example, the portion of the river impounded by the Ben Smith dam in Maynard stretches for some 5 miles through part of Maynard and most of Stow. As a result, the Assabet moves very slowly, warms up in the summer, and is unable to efficiently flush pollutants such as phosphorus.

This human-made hydrology makes the river extremely sensitive to small amounts of nutrient pollution, resulting in the growth of noxious aquatic plants more often associated with small, stagnant bodies of water. The heavy phosphorus discharges of the past have settled in the sediments of these impoundments, and every year supply phosphorus to the aquatic vegetation. It's like a dose of Miracle Grow™ each spring. A Sediment and Dam Removal Feasibility Study by the Army Corps of Engineers was completed in 2010. More about dams on the Assabet.

Next door
There is hope for Hop Brook in the Sudbury watershed as well. In addition to accepting its Westerly permit for the Assabet, the City of Marlborough is upgrading its Easterly facility to meet the same phosphorus standard. The Easterly facility discharges to Hop Brook, a tributary of the Sudbury River that flows through the town of Sudbury (past the Grist Mill). Like the Assabet, Hop Brook and its ponds become overgrown with algae and other aquatic plants in the summer, a result of excessive nutrient pollution from the Marlborough Easterly facility. The Hop Brook Protection Association and the Town of Sudbury have fought for many years to get this stream cleaned up. A June 2005 decision of the EPA appellate board in Washington, D.C. validated Sudbury's contention that the Easterly permit did not comply with the federal Clean Water Act. As a result, the EPA had to issue a new, more stringent permit.

OARS' 2005 appeals
OARS' 2007 comments on the Comprehensive Wastewater Management Plans for each community
NPDES permits