Nature of Activity: The Town of Acton needs sewers and a wastewater treatment plant to replace failing septic systems in portions of the town, however, new discharges into the Assabet River are prohibited because of high phosphorus levels. A plan has been proposed that would allow a new point source to discharge into the river if the municipality were to obtain offsets via nonpoint source reductions.

Environmental Problem: Eutrophication in the Assabet River.

Pollutant(s) / Pollution Type(s): Phosphorus.

Trade Types: Point/nonpoint. The Town is evaluating a broad range of possible offset sources, including road sanding, landscaping and more traditional BMPs. Notably, the reduction in septic system loads that will result if households are connected to a new POTW will not be counted as offsets, as the regulatory authorities have determined that offsets must derive from entirely unrelated sources.

Stage of Implementation: The town currently has no POTW and proposals to build one have surfaced regularly for decades. The current modeling and monitoring efforts have been ongoing since 1998. The Town hopes to have an EPA-approved plan by late 2000.

Relation to TMDL: Portions of the Assabet River, including the segment from Acton to the confluence downstream with the Sudbury and Concord Rivers, do not attain water quality standards for nutrients, organic enrichment / DO, and pathogens. A TMDL is under development.

Number of Potential Participants: The Town of Acton, US EPA, Massachusetts EPA and multiple nonpoint sources.

Trading Ratios: A preliminary target of 3:1 has been proposed.

Estimated Cost Savings: Because it will offset all of its phosphorus discharge, the planned POTW may be authorized to achieve a phosphorus effluent limit of 0.2 mg/ L as opposed to 0.1 mg/ L, which will result in significant O&M savings. The offset activities are expected to cost the town $100,000 - $200,000 annually. The POTW is expected to obviate the need for approximately 150 septic tank reconstructions annually, at an estimated cost of $15,000 per home, thus residents can be expected to save $2.25 million annually. Capital and operating costs for the $7 million POTW will be financed entirely by user fees.

Available Written Information: Various studies have been published and more are underway. Several studies and reports are available from the Acton Public Health Department.

Innovative Aspects: The Town is using a very detailed GIS to pinpoint the sources of phosphorus loadings within the watershed that have the greatest impact on water quality. Additionally, the Organization for the Assabet recruited 150 volunteers to take part in a survey of 25 miles of the river’s shoreline conditions. The volunteers identified areas where BMPs could be implemented. Title V of the Massachusetts’ Environmental Code has stringent requirements regarding sale of homes with faulty septic systems. Sewerage is thus likely to increase the value of many homes.

Obstacles: The project has had difficulty in identifying sufficient nonpoint sources to offset the entire planned discharge from the new POTW. EPA insists that the offsets must be additional, i.e., that they would not have happened anyway in the absence of the trading program. Establishing what constitutes "additionality" has been a point of some debate. It is unclear whether and to what extent the reduced phosphorus loads when failing septic systems are replaced by sewers and a POTW will count toward the offsets.

Web Sites: Concord: http://www.epa.gov/surf2/hucs/01070005/

Contacts: Jane Downing, EPA Region 1. (617)918-1571, downing.jane@epa.gov

Doug Halley, Acton Public Health Department, (978) 264-9634, dhalley@net1plus.com