The concentration of E. coli in the Potomac River near where a wastewater pipe collapsed is dropping by the day.

But many Montgomery County residents fear long-term damage to the river and the shoreline, they said Thursday at a packed community meeting hosted by DC Water at Bethesda’s Walt Whitman High School.

Vicki Judson, president of the Sycamore Island Canoe Club, was one of about 200 people in attendance. She said she doesn’t have enough information to keep her members safe, considering DC Water hasn’t tested the Potomac near her island.

“The county has told us we shouldn’t do things in an impacted area,” she said. “Without testing, we don’t know if we’re an impacted area.”

DC Water’s tests for E. coli on Wednesday — the last day for which data was available — showed the lowest levels of the bacteria in the Potomac since the agency began testing Jan. 29.

Among the agency’s eight testing sites, only the one closest to the collapse site showed levels considered unsafe under federal standards — though the concentration has been well within levels typical for the Potomac since Saturday.

But DC Water and public health officials have said E. coli levels will continue to fluctuate. Levels of the bacteria in the Potomac have historically ranged from about 10 mpn to 5,000 mpn per 100 milliliters.

The break on Jan. 19 of the Potomac Interceptor, a pipe 6 feet in diameter, resulted in one of the largest wastewater spills in modern U.S. history. Over the ensuing weeks, the broken pipe released hundreds of millions of gallons of untreated sewage onto National Park Service land and into the Potomac River.

DC Water leaders, who held a similar meeting at the agency’s District headquarters Wednesday, said they understand the public’s frustration over pollution of the river.

“Restoring public confidence requires more than technical fixes,” DC Water CEO David Gadis said. “It requires listening, learning and continuous improvement. And that is why my team and I are here tonight.”

Avoiding another break

Since the collapse, the agency has inspected 22 “high-priority” areas along the pipeline, which runs 54 miles from Dulles, Virginia, to a wastewater treatment facility in the District, said Matthew Brown, the agency’s chief operating officer.

The agency hasn’t discovered anything requiring an emergency response, Brown said.

He and other agency leaders said DC Water plans to examine the full length of the pipeline to make sure it’s structurally sound.

Some at the meeting questioned how the agency would rehabilitate plants, soil and waterways around the collapse site.

The agency plans to focus its cleanup on a drainage channel along the Clara Barton Parkway, where backed-up sewage bubbled out of a manhole cover after the pipe collapsed.

Crews will clean the C&O Canal, which for weeks has been used as a bypass to carry sewage around the broken pipe. They will also tend to a tributary that carries wastewater to the Potomac.

Agency leaders said crews will clear these areas with mini excavators and by hand or with rakes to protect vegetation. Crews will then replant and reseed.

It took more than a month to reach the damaged section of the pipe. Crews on Thursday finished excavating 45 feet of rocks and debris that were blocking access.

DC Water can soon begin the repair of the Interceptor.

Crews will pressure wash the pipe and coat it with layers of geopolymer — a spray-on cement resistant to corrosive sewer gases. That will prepare the pipe to again handle tens of millions of gallons of wastewater per day.

Agency leaders said they expect these repairs to be completed by mid-March.

They also praised their agency’s response to the collapse. Gadis applauded DC Water’s “Herculean” efforts to install a bypass system to stem the sewage overflow and clear the rocky dam. Workers long weathered subfreezing temperatures, he said.

Water quality

DC Water officials said they have prevented wastewater from escaping the broken pipeline and the canal bypass since Feb. 8, and water quality has improved in the vicinity of the collapse.

The Environmental Protection Agency deems E. coli levels beyond 410 mpn per 100 milliliters unsafe. Concentrations near the collapse site had registered at hundreds and more than 1,000 times that in recent weeks.

Health advisories remain in place in Montgomery, Prince George’s and Charles counties in Maryland.

As bacteria levels have dropped, jurisdictions have reconsidered their warnings.

District officials said Wednesday they plan to lift an advisory against using the Potomac River on March 2. The District’s health director, Dr. Ayanna Bennett, said she expects the river in D.C. to be safe for local paddlers and crew teams by that time.

As a precaution after the collapse, the Maryland Department of the Environment closed a portion of the Potomac used for shellfish harvesting. The agency announced Thursday it plans to reopen that section of the river March 10.