Many of EPA’s recent stormwater efforts have revolved around the Chesapeake Bay—cleaning it up and protecting it from further pollution—and the Bay has also been a test bed of sorts for measures EPA might eventually undertake elsewhere. In 2010 EPA established the Chesapeake Bay TMDL to reduce nitrogen, phosphorus, and sediment reaching the Bay, setting what it called “aggressive targets” for pollutant reduction. Part of the Chesapeake Bay’s problem is that it receives runoff from so many different jurisdictions: parts of Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia, and all of Washington DC.
Focusing on one part of the equation, last week EPA issued a new MS4 permit for Washington DC. Runoff from DC flows to the Potomac and Anacostia rivers and to Rock Creek, ultimately discharging to the Chesapeake Bay. The new permit emphasizes the use of green infrastructure. All development projects of 5,000 square feet or more must retain 1.2 inches of stormwater onsite for a 24-hour storm. And the District must develop a retrofit plan for existing development. Many of these measures are similar to those expected in EPA’s nationwide stormwater rule, a draft of which is now expected in December.
Among other green infrastructure measures, the new permit calls for a very specific amount of green roof space: 350,000 square feet at a minimum. Some have questioned the cost effectiveness of this particular requirement, as green roofs are one of the more expensive options for retaining runoff.
You can read the entire permit here or see the details in a 38-page EPA Fact Sheet.