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The Potomac River around Washington, D.C., is again considered safe for recreation following more than five weeks of water-quality warnings caused by a spill of over 200 million gallons of raw sewage.
Recreational activities, including rowing practices, may resume after the March 2 lifting of the advisory. Officials said drinking water was not affected because Fairfax Water’s intake is several miles upstream from the spill site.
The discharge began after a six-foot-wide Potomac interceptor ruptured Jan. 19. The 54-mile pipe normally carries 60 million gallons of untreated sewage each day from Dulles Airport to the Blue Plains treatment plant in Southeast Washington.
Officials said the damaged interceptor has not leaked since Feb. 8. A temporary bypass reroutes wastewater using pumps and part of the C&O Canal while repairs continue, with completion expected by mid-March.
Bacteria levels decline
Water-quality monitoring has focused largely on E. coli, a group of bacteria commonly found in the intestines of people and animals. Tests indicate concentrations have been steadily declining, although levels in the Potomac can naturally vary considerably.
Historical measurements have ranged from 10 to 5,000 most probable number, or MPN, per 100 milliliters. Swimming is discouraged when E. coli exceeds 410 MPN per 100 milliliters. Drinking water, by comparison, should contain no detectable E. coli.
Virginia’s Department of Environmental Quality sampled 25 locations along roughly 49 miles of the river on Feb. 17 at the request of state Sens. Scott Surovell and Richard Stuart and Del. Paul Krizek.
Results included 313 MPN per 100 milliliters at Hunting Creek and the Potomac River, 31 at Jones Point, 158 at Belle Haven Marina, 10 across from Fort Washington, 85 at Little Hunting Creek and the Potomac, and 20 at Gunston Hall. A Feb. 25 test at National Harbor measured 105.
Virginia health officials had issued an advisory Feb. 13 covering 72.5 miles between the American Legion Memorial Bridge in Fairfax County and the Harry W. Nice Memorial Bridge in King George County. Residents and their pets were urged to avoid swimming, wading, canoeing, kayaking and other recreational contact with the water.
Fairfax County Deputy County Executive Jennifer Miller said bacterial monitoring showed no continuing effects downstream. She said long-term impacts were not expected now that the spill had been contained.
Early tests found extreme contamination
University of Maryland testing found E. coli at the spill site reached thousands of times the recreational safety threshold on Jan. 21, Jan. 28 and Feb. 3. Levels remained more than 100 times the contact limit on Feb. 12, while a Jan. 28 sample taken 10 miles downstream also exceeded the threshold.
Researchers detected Staphylococcus aureus at the spill site and nine miles downstream on Jan. 21 and Jan. 28. Overall, the pathogen appeared at 33% of sampled locations. MRSA, an antibiotic-resistant form of the bacteria capable of causing infections, was also identified at the spill site.
Dean Naujoks of the Potomac Riverkeeper Network has been collecting samples at numerous locations to evaluate conditions across the river.
Dr. Joan Rose, a Michigan State University water microbiology expert, said untreated wastewater can contain as many as 100 types of pathogens in varying concentrations. Even when most organisms die after entering the environment, enough may remain to cause illness.
Rose said roughly 1% to 3% of E. coli strains are pathogenic. Sewage can also carry salmonella, hepatitis A and norovirus. Some pathogens can persist for months in sediment, while nitrogen and phosphorus from wastewater can intensify hazardous algal blooms, including varieties that produce respiratory toxins.
She also cited a three-year study by University of Illinois researcher Sam Dorevitch involving 11,297 people. It found an increased risk of gastrointestinal illness from limited-contact activities such as boating, canoeing and fishing, both in effluent-dominated waterways and waters designated for general use.
Environmental and economic questions remain
The spill’s ecological effects may depend on whether pathogens and organic material accumulate along shorelines or islands, Rose said. Pooled water with heavy organic loads can lose oxygen, harming bottom-dwelling organisms and other aquatic life. A single spill may have only temporary effects, but repeated nutrient pollution can disrupt ecosystems.
Sewage solids can smother habitat, while bacteria, viruses and chemicals can infect or poison plants and animals. Fish and wildlife surveys beginning in the spring, with some work planned as early as late February, are expected to help determine whether the spill caused broader damage.
Naujoks has urged officials to monitor areas south of the Woodrow Wilson Bridge and assist watermen whose livelihoods depend on the Potomac. His organization supports daily testing, warning that uncertainty about contamination could undermine public confidence in the river.
Blue catfish season begins in March, and Naujoks said about 3.4 million tons are harvested from the Potomac annually. He questioned whether consumers would remain willing to buy and eat the fish and said federal assistance should be directed toward communities and workers affected by the spill.
Rep. Don Beyer has also drawn attention to vulnerabilities in the sewage system, which is more than 60 years old. Beyer and 10 other Washington-area members of Congress are seeking money to repair and modernize the interceptor. They have also asked the U.S. Army Corps of Engineers to identify a backup water supply for the Washington region, which currently has no secondary source.