Today, the U.S. Environmental Protection Agency (EPA) announced residual designation for all three major river systems in the Greater Boston area. The designation means that the owners of non-residential properties with > 1 acre of impervious cover will be required to address the stormwater pollution coming off of their property. This new requirement will address a major gap in current stormwater regulations that to-date have only focused on municipal management and new development/construction.
Stormwater pollution occurs when rain flows over land (driveways, lawn and streets), picks up the pollutants on those surfaces and drains into the nearest storm drains and water body. These discharges are untreated. Stormwater runoff is the leading cause of nutrient pollution on the Mystic. Phosphorus pollution, in particular, can have a variety of harmful impacts on a river including toxic cyanobacteria blooms, excessive growth of invasive aquatic plants, and low dissolved oxygen in the water. In some cases, decomposing algae can make dissolved oxygen levels become so low that fish no longer survive. This event is known as a “fish kill.”
This residual designation requires one more step before it becomes impactful — the issuance of permits. Through this new permitting process, non-residential properties will be required to certify that they are taking a series of actions to address this pollution. The details of the permit are not known yet, but will likely include a mix of street cleaning, infiltration practices, and leaf-litter collection.
“The Mystic River is cleaner today than it has ever been in the past 80 years. We have seen that investments and regulation, like the Clean Water Act, can have big impacts on our urbanized watershed,” said Patrick Herron, Executive Director. “This new authority will have long-lasting impacts on water quality — especially in light of an expected increase in rainfall due to climate change.”
This positive outcome for all 3 watersheds in Greater Boston comes after petitions from the Conservation Law Foundation and Charles River Watershed Association and advocacy from the Mystic River Watershed Association. Originally, the EPA planned to only announce authority for the Charles River Watershed — leaving the Mystic and Neponset out of these needed improvement. MyRWA engaged in active conversation with EPA to ensure equity in the application of these Clean Water Act tools.
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