WWTP Permits

Major Milestone for the Assabet: Marlborough wastewater treatment plant permit in effect

On April 6th, 2006, Marlborough joined Hudson, Maynard, and Westborough/Shrewsbury in making a commitment to upgrading its wastewater treatment facilities to meet, among other requirements, an effluent phosphorus concentration limit less than one-seventh of its current 0.75 mg/L limit. The municipal facilities will be required to meet the new phosphorus limit of 0.1 mg/L beginning in 2010. This is a tremendous win of national significance for the Assabet River. A scant handful of publicly-operated wastewater treatment facilities (POTWs) around the country have been required to meet phosphorus limits this low or lower.

On March 27, the OAR Board of Directors voted to accept the City of Marlborough’s offer to withdraw its appeal of the Westerly Wastewater Treatment Facility’s NPDES permit, provided OAR did the same. This facility, which serves portions of both Marlborough and Northborough, discharges to the Assabet River. On April 6th, OAR and the City withdrew their appeals, and the permit is now in effect.

There is hope for Hop Brook in the Sudbury watershed as well. In addition to accepting its Westerly permit, the City of Marlborough has agreed to upgrade 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 (and strengthened our case on the Assabet as well). As a result, the Hop Brook permit was remanded back to EPA Region 1, which meant the EPA had to issue a new, more stringent permit. Because the EPA decided to wait to issue the new Hop Brook permit until the Assabet permits were settled, the agency essentially held that permit – and Hop Brook itself – hostage to a settlement of the Marlborough Westerly permit. In addition to moving the Assabet cleanup a giant step forward, OAR’s and Marlborough’s settlement rescued the Hop Brook permit from remand purgatory.

The few publicly-operated POTWs around the country that have been required to meet phosphorus limits this low or lower are mainly facilities that discharge to lakes or ponds. Facilities that discharge to the Chesapeake Bay in Maryland must meet a 0.3 mg/L phosphorus limit. A large facility that serves an entire county in Georgia and discharges to the Chattahoochee River must meet 0.08; but this facility discharges to a lake that serves as a public water supply. A facility in Syracuse, New York that also discharges to a lake is scheduled to meet a very low phosphorus limit - 0.02 mg/L - beginning in 2012.

Although the Assabet is among those in the forefront of this trend, 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.

The Assabet behaves along much of its length more like a lake 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. The portion of the river impounded by the Ben Smith dam in Maynard stretches for almost seven 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 man-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.

OAR advocated for the studies that demonstrated that permits at least this strict were necessary to meet the terms of the Clean Water Act. While we did not get the phased permits that we sought – 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 – we are pleased with this big step forward. We hope and expect that the Assabet’s sewered communities will invest in scalable technology, capable of meeting these lower limits in the future. We are delighted to see these permits accepted by the communities, and we look forward to seeing a healthier Assabet beginning in 2010.