The proposal strengthens a permit proposed by the agency last August for the Blue Plains wastewater treatment plant in southwest Washington.
Blue Plains is the largest advanced wastewater treatment plant in the world. Covering 150 acres, it has a capacity of 370 million gallons per day, and a peak capacity of 1.076 billion gallons per day.
In comments filed on behalf of Friends of the Earth and Sierra Club, the nonprofit, public interest law firm Earthjustice challenged the legality of the weaker permit.
The new proposal, issued late last week, sets tighter caps on nitrogen, a pollutant that contributes to oxygen depletion that leads to summertime dead zones in Chesapeake Bay.
'This action is a welcome step toward cleaner water and a healthier future for the Chesapeake Bay,' said Earthjustice attorney David Baron. 'The prior proposal violated legal requirements for cleaning up the bay. We called for stronger protections and EPA finally listened.'
Blue Plains is the largest single point source of nitrogen in the Potomac basin. The revised permit proposal would limit nitrogen discharges from the plant to 4.689 million pounds per year, a reduction from the nearly 8.5 million pounds allowed under the previous proposal.
Nitrogen pollution leads to huge blooms of algae in the bay. When the algae die and begin decomposing, oxygen levels fall, threatening fish and other aquatic life.
During summer months, low dissolved oxygen levels in the Chesapeake lead to dead zones that stretch for miles.
In July 2003, one of the largest dead zones since monitoring began 20 years ago occurred, affecting 40 percent of the bay's main stem near Baltimore, and extending for more than 100 miles south.
The Chesapeake Bay Agreement commits the District of Columbia and states in the bay region to achieve cleanup goals for the Bay by 2010. Nitrogen caps on sewage plants like Blue Plains are part of the cleanup strategy.