EPA Requires Permits for Previously Unregulated Stormwater Discharges in Massachusetts

September 20, 2022

The US Environmental Protection Agency (EPA) announced on September 14 that it will require new permit coverage for previously unregulated stormwater discharges in Massachusetts. Specifically, EPA intends to issue general permits covering discharges from commercial, industrial, and institutional (CII) properties with one or more acres of impervious surfaces—hard surfaces like roofs, parking lots, roadways, and areas covered with artificial turf—in the Charles, Neponset, and Mystic River watersheds.

While EPA’s National Pollution Discharge Elimination System (NPDES) program previously regulated stormwater discharges associated with industrial and construction activities, this is the first time that EPA has exercised its residual designation authority under the Clean Water Act (CWA) on such a broad scale to regulate stormwater from other types of property uses, including office parks, shopping malls, hospitals, and private colleges and universities.

Once the new permits are issued, affected CII properties in nearly 60 communities in the Boston metropolitan area will be required to seek permit coverage. Together, the Charles, Neponset, and Mystic River watersheds cover a wide geographic area, ranging from Woburn and Reading to Foxborough and Sharon, and from Hopkinton and Milford to Boston, Cambridge, and Quincy. According to EPA, an estimated 1,776 CII properties in the Charles River watershed alone will be required to satisfy the new requirements. The impacted communities are highlighted in yellow in this map image.

Mass GIS map of watersheds

Source: MassGIS

EPA’s announcement is consistent with a growing trend toward increased enforcement. It is a direct response to petitions filed by the Conservation Law Foundation (CLF) in 2019 and 2020 asking EPA to use its residual designation authority to address excess nutrients and bacteria in all three watersheds, impairments that, together with climate change, have led to an increase in harmful algae blooms in recent years. Read CLF’s Charles River Watershed RDA Petition, Mystic River Watershed RDA Petition, and Neponset River Watershed RDA Petition.

CLF’s petitions are similar to recent petitions filed in Baltimore and Los Angeles, both of which were initially denied by EPA, but were reversed on appeal. The courts interpreted the Clean Water Act to require EPA to regulate stormwater discharges following a determination that the discharges contribute to a violation of water quality standards.

EPA has not yet provided a timeframe for the release of a draft of the general permits in Massachusetts. There will be public comment periods both on the draft general permits and on EPA’s decision to exercise its residual designation authority.

EPA anticipates that the general permits will specify best management practices (BMPs) for reducing stormwater pollution. These BMPs may be structural and/or operational and may include housekeeping and general landscape maintenance to reduce trash and leaf litter, sweeping parking lots to reduce pollutants, installing rain gardens and other green stormwater infrastructure, and reducing pavement or utilizing pervious pavement. Permittees may be required to demonstrate compliance through routine sampling and inspections.


If you have any questions or would like more information on the issues discussed in this LawFlash, please contact any of the following:

Emily J. Dupraz (Boston)
Washington, DC
Los Angeles