The U.S. Environmental Protection Agency today announced new actions under the Clean Water Act to control currently unregulated stormwater pollution from entering the watersheds of the Charles, Mystic and Neponset rivers.

The EPA will use its “residual designation authority” under the Clean Water Act to require permit coverage for stormwater discharges from currently unregulated and uncontrolled sources of stormwater pollution in the Boston-area watersheds.

Certain commercial, industrial and institutional properties with one or more acres of impervious area (hard surfaces such as parking lots, roofs and roadways) will be required to obtain coverage under an EPA Clean Water Act permit. Once permits are issued, property owners will be required to take steps to reduce pollutants in stormwater.

The EPA says the effort is expected to dramatically improve water quality throughout the watersheds, as well as reduce localized flooding and increase recreational opportunities through healthier river systems in historically disadvantaged neighborhoods.

“It is clear that the nature and scale of the problem requires urgent action on this pressing environmental justice concern,” said EPA New England Regional Administrator David Cash. “With a warming climate, there is no time to waste to reduce bacterial and nutrient pollution in stormwater and the resulting water quality degradation, including harmful algae blooms experienced yearly in all three watersheds.”

Beginning in 1995 with the Clean Charles River Initiative, the EPA has worked with state government, local communities, other organizations and individual citizens to restore water quality in the three major Boston-area urban rivers. The efforts “have yielded significant water quality improvements in portions of all three watersheds,” according to the EPA, especially by reducing bacterial contamination. Stormwater pollution, however, continues to be the largest uncontrolled source of phosphorus, nitrogen and bacteria, which is harming water quality in each of the three river watersheds. Nitrogen and phosphorus also lead to toxic algal blooms in hot weather events.

The EPA anticipates issuing one or more general permits specifying the activities that property owners must implement to reduce stormwater pollution from their properties. Privately owned commercial, industrial and institutional properties with 1 acre or greater of impervious cover will need to seek coverage under one of these permits (or an individual permit if they prefer) and take the actions spelled out in the permits.

The general permits will be released in draft form for public comment.

The EPA says the new permit will likely rely on easily implemented “best management practices” — including leaf litter pickup, parking lot sweeping, installing rain gardens or other infiltration practices, planting trees, reducing pavement or using pervious pavement — to reduce stormwater discharges into waterways and increase infiltration of stormwater back into the ground.

Municipal governments in the Charles, Mystic and Neponset river watershed are already subject to EPA permits that require them to take steps to reduce pollution in stormwater, and they have made significant investments to do so. Much of the pollution comes from commercial, industrial and institutional sources, however, such as office parks, industrial parks, shopping centers, private colleges and universities, and hospitals.

Large impervious areas are one of the last major unregulated sources of water pollution, according to the EPA. Extensive impervious cover also aggravates the severity of flooding because those areas diminish the amount of land that can naturally soak up and filter rainwater.

Stormwater controls such as those envisioned by EPA to comply with this future permit have the added benefit of mitigating the potential for flooding during major precipitation events.

EPA Region 1 – Commercial, Industrial, & Institutional Sites Residual Designation
EPA’s Clean Charles River website
EPA’s Neponset River website
EPA’s Mystic River website