How much E. coli can an urban waterway contain and still be considered “clean”?A tray of water taken from the Potomac River south of the District of Columbia this summer is analyzed for the presence of E. coli by one of several nonprofits now monitoring bacteria levels in local waters. (Whitney Pipkin)

A federal court ruled in August that the limits the District of Columbia set for E. coli in its waterways didn’t adequately answer that question.

E. coli is a type of bacteria often found in fecal matter that can indicate the presence of other pathogens. Some strains of E. coli infection can cause abdominal cramps, diarrhea, fever and vomiting.

The decision from the U.S. District Court for the District of Columbia gives regulators about a year to craft new limits for the Anacostia and Potomac river systems running through the nation’s capital.

The decision was a response to a lawsuit filed in 2016 by Earthjustice on behalf of three environmental groups — the Anacostia Riverkeeper, Kingman Park Civic Association and Potomac Riverkeeper Network — against the U.S. Environmental Protection Agency for its approval of the District’s E. coli limits in 2014.

Earthjustice contended that the EPA violated the Clean Water Act because the limits, formally known as total maximum daily loads or TMDLs, did not set daily discharge maximums. Instead, the TMDLs were based in part on equations that allowed the waterways to exceed the numeric daily standard in a 24-hour period as long as certain averages were maintained over a 30-day period. The document said this approach allowed for more variability, but the plaintiffs disagreed.

“A TMDL, on the face of it, should represent the maximum total amount of a pollutant that can be added to a waterbody on a given day and still have it comply with water quality standards,” Earthjustice attorney Seth Johnson said.

The court largely agreed, though it did not side with the plaintiffs on other technical arguments.

TMDL calculations, one of several criteria used to achieve water quality, are the basis for permits issued to regulated dischargers stating how much of a pollutant can be present in their wastewater.

One of those regulated dischargers, DC Water, runs the world’s largest advanced water treatment facility on the banks of the Potomac River at Blue Plains. It interceded as a defendant on the case, arguing on the EPA’s side.

DC Water had sued the EPA in 2015 over an earlier version of the E. coli TMDLs, contending that the limits were too stringent. The EPA then issued a revised rationale for the limits, and DC Water dropped its suit.

DC Water officials said they are still reviewing the court’s most recent ruling, which will result in the E. coli TMDLs being reworked once again.

“Our efforts thus far have resulted in significant improvements in the Anacostia River’s water quality, and we will continue our active engagement to bring tangible, measurable benefits to the District’s waterways,” DC Water spokesman Vincent Morris said.

The statement also said that such an effort will require “sound science and data-based approaches spanning multiple generations and coordinated efforts” between government agencies and the public.

To help reduce the amount of E. coli entering the city’s rivers, DC Water is in the midst of a $2.7-billion Clean Rivers Project required by the EPA to curtail the city’s long legacy of combined sewer overflows. Those overflows have routinely gushed sewage-laden stormwater into nearby rivers during heavy rains.

The project involves 18 miles of large underground tunnels designed to capture polluted runoff and steer it toward the wastewater treatment plant. The first stretch came online in spring 2018. When the second phase is completed in a few years, officials predict it will end approximately 98% of all polluted overflows to the Anacostia.

Contamination from E. coli is one of the many challenges in an ongoing effort to make the Anacostia River swimmable by 2025. A secondary issue with a TMDL that allows for average rather than daily E. coli limits is that it could leave future swimmers vulnerable to the bacteria on some days.

Though it is still illegal to swim in District waters, the Anacostia Riverkeeper now operates a sizable citizen monitoring program that allows the public to track the river’s real-time progress toward that goal. The results of weekly tests are posted on the Swim Guide website, which, despite its name, includes the reminder in capitalized letters that swimming is still prohibited regardless of the status.

“We cannot disclaim that enough,” said Trey Sherard, Anacostia Riverkeeper’s outreach coordinator and biologist. He emphasized that the E. coli TMDL lawsuit and the citizen monitoring effort are different facets of the same approach toward cleaner water.

“This is just one more piece in the puzzle to keep it moving in the right direction,” he said.

The District also is in the process of rewriting its so-called trash TMDL for the Anacostia River after the Natural Resources Defense Council successfully argued in a lawsuit that the TMDL, which detailed how much trash must be removed from the river, falls short of establishing a maximum for how much trash can enter the river in the first place. Until then, trash is still being removed from the river in accordance with the previous TMDL.