It was hard to hear Jorge Bogantes Montero above the din of traffic helicopters circling over Washington, DC, as he described the handful of muddy shells he and a small team had just dug from the mucky bottom of the Anacostia River.

In a couple hours of combing through the thick mud exposed at low tide, they’d found the shells of two Eastern floaters, a paper pondshell and a nonnative Asian clam — not much, perhaps, but something for an urban river that many still think of as containing little life, let alone mussels.

Taking cover from a sudden downpour under the footbridge that connects the river’s Kingman and Heritage islands, Montero explained why he and others from the Anacostia Watershed Society were on this wild mussel chase in the first place, seeking specimens dead or alive.

In the so-called “forgotten river,” Montero said, “there are so many things happening now.”

As the Anacostia’s advocates wait for a tide of ongoing cleanup efforts to amount to a cleaner waterway, they’re counting mussels to get a baseline of the populations that were once plentiful here — and that they hope will begin to flourish anew.

A Smithsonian Institution exhibit suggests how far the river has to go by showing what has been lost. On display are the shells of mussels that were abundant in this stretch of the river near Benning Road around the turn of the 20th century and into the 1950s; some have yet to turn up in Montero’s search.

Mussels are not only filter feeders that can help clean the waters in which they live, but they also are gauges of the health of their habitats, because they can’t move to cleaner waters as pollution increases.

The watershed group’s surveys didn’t find that many — a couple dozen in all. An increase in those numbers over time could speak volumes about the efficacy of the cleanup efforts under way or planned.

“Mussels would be good indicators of those changes,” Montero said. And their filter-feeding capacity” will help us clean the river, along with everything else we do.”

The watershed society, which employs Montero as a stewardship specialist, has been restoring underwater grasses and marsh areas along this beleaguered stretch of the river and fighting against the intrusion of invasive plant species and overabundant geese.

Elsewhere in the watershed, efforts are under way to curtail the largest sources of pollution.

The District’s wastewater treatment plant is being expanded at a cost of $2.6 billion. When the project is finished around 2022, officials hope it will nearly eliminate sewage overflows into the river that occur routinely during heavy rains.

If done by that date, the expansion would be in place a few years ahead of a deadline set by the Environmental Protection Agency. Federal regulators recently modified their consent decree with the District to let the wastewater utility scale back construction of costly underground tunnels for storing sewage-laced stormwater. Instead, the city hopes to keep some runoff out of the sewers with less expensive “green infrastructure” measures, such as rain gardens.

On another front, in March, the District Department of Energy & Environment released a study that describes in detail about a dozen “toxic hot spots” along the river where an industrial past has left a legacy of pollution in the river’s sediment. The report also revealed that hazardous chemicals continue to wash into the river, adding to the longstanding contamination that already makes it unsafe for residents to swim or wade in some places or eat fish caught from its waters.

The 200-page report is the first step toward developing a cleanup plan for toxic contamination in a 9-mile stretch of the Anacostia because studies show that residents continue to consume fish from the river despite warnings that they are unsafe to eat.

Lori Baranoff, a policy associate with the watershed society, called the study “really solid,” but added, “This river has been studied over and over again. It’s time to get it dealt with.”

After releasing the study by the consulting firm Tetra Tech, Wesley Rosenfeld, DOEE’s assistant general counsel, said more study is needed to determine how to stop the continuing contamination that he said was “unanticipated.”

“Something is happening basically as we speak,” Rosenfeld said in mid-March. “We can’t clean up the river without eliminating an ongoing source of contamination.”

Baranoff said her organization wasn’t surprised to learn that industrial pollution of the river continues. But she said she was concerned that dealing with it could lengthen the timeline for cleaning up what’s already there.

“We need to target ongoing sources as well,” she said, “but we think they can still move forward and not do things step by step.”

The District Council passed a law in 2014 that commits the city and other government and nonprofit partners to produce a cleanup plan by 2018.

While the District is leading the effort, the National Park Service owns the affected stretch of river bottom. Other branches of the federal government could also be pulled in, as some of the lingering pollution may have come from the Washington Navy Yard and two other military bases in the watershed.

Based on more than 900 samples collected over the last two years, the Tetra Tech sediment study lays out a roadmap for the cleanup, which could require parties responsible for the contamination to share in the remediation cost.

About a dozen places along the river are likely to be targeted because of historical contamination of groundwater or river sediment from them. Among those sites are the recently demolished Pepco plant on Benning Road and the federal Bureau of Engraving and Printing.

Of the contaminants identified, two groups are particularly problematic:  polycyclic aromatic hydrocarbons (PAHs), compounds associated with the incomplete burning of fossil fuels or other organic materials; and polychlorinated biphenyls (PCBs), now-banned chemicals once widely used as coolants or insulators in electrical equipment. Both are known or probable carcinogens.

The report also found high levels of contaminants, indicating ongoing contamination, near outfalls on either side of the 11th Street Bridge — by the Washington Gas Light Company’s former coal-gasification plant and by the Washington Navy Yard. A spike was also found near the former Steuart Petroleum terminal just downriver from the South Capitol Street Bridge.

While planning is under way to clean up PCB contamination at the old Pepco plant site, a recently filed lawsuit contends that authorities are overlooking ongoing pollution there.

In a federal court case filed in late March, the Anacostia Riverkeeper contends that according to Pepco’s own discharge reports, hundreds of pounds of toxic heavy metals have continued to wash into the river from the site for at least the last five years, with no action from regulators. The group is seeking a court order to have the EPA investigate and require a cleanup, and the court has granted its request to intervene.

Pepco officials said the company continues to work with the EPA to ensure compliance and that they used “a carefully controlled process” to demolish the power plant, which they contend “significantly reduced the metals concentrations in stormwater discharges to the Anacostia River.”

The Anacostia is widely recognized as one of three toxic “hot spots” in the Chesapeake Bay, along with Baltimore Harbor and the Elizabeth River in Norfolk, VA, where industrial and urban contaminants have accumulated in the sediments for decades.

While little has been done to date about the tainted bottom of Baltimore Harbor, remediation efforts seem to have paid off in a once-toxic stretch of the Elizabeth River. New marshes replaced polluted sediment near Money Point, and the area now teems with wildlife after a $6 million cleanup, according to the Elizabeth River Project.

Some of the same options are on the table for dealing with the Anacostia: dredging and removing toxic sediments, or capping them in place with a clay layer to prevent them from being stirred back into the water or picked up by the bottom-dwelling organisms on which some fish feed.

While efforts continue to reduce litter and stormwater degrading the river, advocates say dealing with sediment contamination is essential if the river is to be made swimmable and fishable by 2032 — the District’s restoration goal.

“The legacy pollution is really the last major effort that hasn’t had something in motion already,” Baranoff said. “We finally have the momentum to get it tackled, so it’s our No. 1 focus.”

In the meantime, Montero’s mussel-finding project is a way to generate data about the river’s current state and to gauge its progress toward that future goal.

Matt Ashton, a biologist at the Maryland Department of Natural Resources who’s been helping conduct the mussel survey, said he was surprised to learn they existed in the Anacostia.

The Smithsonian exhibit and historical sources indicate they were once abundant in the river. Ashton said Native Americans used crushed mussel shells from these areas to make pottery and occasionally consumed their meat as protein sources.

But because filter feeders are liable to pick up toxic contaminants, they are indicators of environmental degradation; mussel populations have declined here and elsewhere as rivers have become more polluted.

To date, the watershed society survey has found a total of six mussel species in the Kingman Lake portion of the river. The survivors include live Eastern floaters and paper pondshells, and the shell of a tidewater mucket.

“We got more tires than mussels in the main stem,” Montero said, after two days of dredging turned up just three live ones.

But the survey leader suggested that areas near Kingman and Heritage islands could be fertile ground for trying to rebuild the bivalve population. The society has restored wetlands there, and is now weighing whether to try propagating more of the mussels it’s found so far, or shoot for introducing some of the lost species.

“Nobody has really cared about mussels,” Montero said, “but they are really one of the most endangered animals in the world… And there used to be more of them here.”

(This post originally misnamed Jorge Bogantes Montero and the chemical name for PAHs. The Bay Journal regrets the errors.)