Washington D.C. Sewer System Showing High Bacteria Counts

Nov. 7, 2018

Combined sewer system in Washington D.C. mixes stormwater and sewage in the same pipes

In Washington D.C., DC Water has recently completed a new sewer tunnel. According to Wamu, the Anacostia River was supposed to get a lot cleaner after the new addition. Instead, water testing in the areas showed bacteria counts were higher in the summer of 2018 then in 2017. According to Wamu, the major issue was rain.

The combined sewer system in D.C. mixes stormwater and sewage in the same pipes. The system is designed to overflow into the Anacostia and Potomac Rivers and Rock Creek, according to Wamu.

The water utility is currently under a consent decree with the Environmental Protection Agency to stop dumping into the waterways, according to the talk station.

The new tunnel system has captured and treated 3.3 billion gal of combined sewage and stormwater, thus far. According to Wamu, the tunnel is performing better than expected, preventing 89% of overflows.

“We’re pretty happy with the performance of the tunnel so far,” said John Cassidy, program manager with DC Water’s Clean Rivers Project, to Wamu.

This year has been Washington's second, next to 1889, in the most rain on record. The rain has come in bursts, overwhelming the drainage system and causing the overflows. About 300 to 400 million gal spilled into Anacostia despite the new system.

According to Jeff Saeltzer, associate director for water quality with the District Department of Energy and Environment, the water testing over the summer has showed conflicting results.

“We know without a doubt that these tunnels are reducing a tremendous volume of bacteria that would have otherwise gone into the river,” said Seltzer to Wamu. “It is hard to directly correlate the data we’re seeing to what the impact of those tunnels are, since there’s such large variations in rainfall, especially over the last year.”

The water is being tested at three sites every week along the river throughout the warmer months of the year, according to the talk station. Two of the sites showed higher average bacteria counts this year, 65% higher and 37% higher. The third site showed levels that were 44% lower than that of 2017.