Signs warn about city sewage where it enters the Potomac River at the Oronoco outfall. (Bill O’Leary/The Washington Post)

Virtually every time it rains in Old Town Alexandria, the city’s aged sewers spew raw sewage into the Potomac River — about 11.3 million gallons a year.

The city, under orders from state and federal authorities, is launching an expensive effort to capture and contain overflows in three locations, which should fix much of the problem. But the plan does not include the biggest outfall of all, one that dumps sewage directly into Oronoco Bay, accounting for nearly half of all the overflow into the river.

City officials say the Oronoco area was not included in a 2010 federal order to reduce pollution from sewage outflows. They note that the land around the site is slated for major redevelopment in coming years that will include infrastructure improvements — paid for by the city and by developers — that should address much of the problem.

But critics say the phased approach will leave Oronoco Bay clogged with algae and human waste multiple times each month, even as the other areas improve. They argue that the wealthy riverfront city could easily fund the entire project, and they fault the local government for waiting until now to act.

“If Alexandria wants to revitalize its waterfront and encourage recreation and tourism like Georgetown, they must eliminate the discharge,” said Dean Naujoks, who works for the Potomac Riverkeeper Network, a nonprofit group. “You can’t call yourself an eco-city and have it both ways.”

State Sen. Scott Surovell (D-Fairfax), whose district sits just downstream from the overflow areas, accused the city government of “not wanting to prioritize raw sewage over other infrastructure projects, like soccer fields or intersection widening.”

About 800 communities around the nation have combined storm water and sewer pipes, including older cities such as Chicago, Philadelphia and the District, which is building a 13-mile tunnel to store sewage and rainwater en route to the Blue Plains wastewater treatment plant.

Officials say Washington will have reduced 96 percent of its sewer overflow when its $2.6 billion project is completed in 2022at least a decade before Alexandria finishes work on three of its four outfalls, and begins to consider what to do with the fourth.

Sewage in the river can lead to dangerous levels of bacteria such as E. coli, which is a threat to human health and has been found in elevated levels along the part of the river that borders Alexandria. Sewage is also a source of nitrogen and phosphorus pollution, harmful to fish and other aquatic life.

In 2010, as part of an effort to boost compliance with the federal Clean Water Act, the state imposed a new limit on how much E. coli can come from the three sewer outflows just south of the Capital Beltway. That change led to the updating of the long-term control plan, which the city finished in August.

David McGuigan, the regional Environmental Protection Agency official who oversees water quality permits, said the agency is keeping an eye on the Alexandria project, even though direct responsibility for approving the long-term control plan and enforcing permits falls to the state Department of Environmental Quality.

“I wouldn’t say Alexandria proposes to do nothing [at Oronoco Bay], but it lacks specificity and clear timing,” McGuigan said of the city’s current blueprint. “We need to talk with Virginia to come to an understanding of what expectations are for that plan.”

Alexandria’s combined storm-water and sewer system covers 540 acres in Old Town. On dry days, both runoff and sewage flow through a single pipe to the city’s wastewater treatment plant, which treats the effluent until it is clean enough to release. But 40 to 70 times a year, enough rain falls that the combined pipe is overwhelmed, forcing the release of both rain runoff and untreated sewage into public waterways.

The city plans to build a 1.6 million gallon storage tunnel and a 3 million gallon holding tank for the three outlets south of the Beltway, so that overflow during and after rainstorms would be isolated and later sent to the treatment plant.

The project is expected to cost $125 million to $188 million and will be funded through bonds, which will add $10 to $15 per month to local sewer bills that now average $48 per month. The city will also seek money from Virginia; both Lynchburg and Richmond won grants recently for similar projects. In 2014, Gov. Terry McAuliffe (D) attempted to award Alexandria $1 million for its combined-sewer project, but the House of Delegates struck it from the budget.

The Oronoco Bay site, at the foot of Pendleton Street, is next to the now-closed Robinson Terminal North warehouse, which is slated to become a residential, retail and office complex.

William Skrabak, deputy director of environmental services for Alexandria, stands on a spot overlooking where city sewage enters the Potomac River at the Oronoco Bay outfall. “We’ve been trying to solve the problem. If it was a simple solution that was inexpensive, it would have been done years ago,” he said. (Bill O’Leary/The Washington Post)

William Skrabak, Alexandria’s deputy director of environmental services, said the city is not ignoring the runoff there. Any development projects will have to create separate wastewater and sewage systems, and put in green infrastructure where it’s cost-effective. The city will improve its storm-water controls by encouraging the installation of permeable pavement, green roofs and more trees.

By these methods, Skrabak said, the city hopes to considerably reduce storm-water runoff. Officials plan to assess the impact of those changes after the construction at the other sites is finished, probably in 2032. A tunnel and tank project for the Oronoco site, Skrabak said, would cost another $70 million to $100 million.

The citizens advisory committee that studied the issue for about a year endorsed the city’s phased approach. But committee member Jack Sullivan submitted a minority report in which he labeled the Oronoco decision “unacceptable.”

“Politicians kicked the can down the road for 15 years, and now the chickens are coming home to roost,” Sullivan said.

Ernie Lehman, an Old Town retiree who lives three blocks from Oronoco Bay, also criticized the city. “They have an active pollution site, and the city is not taking any real action on it,” he said.

In mid-September, Surovell triggered a small social-media firestorm, tweeting that Alexandria “is still regularly dumping untreated sewage into the Potomac.”

Alexandria City Council members Justin Wilson and John Taylor Chapman, and former council member and delegate Rob Krupicka fired back, asking on Twitter and Facebook what Surovell had done to help fix the problem.

Wilson said that the council voluntarily added provisions to the long-term control plan that direct the city’s environmental services staff members to look for faster ways to reduce overflows at Oronoco.

Surovell, in turn, pointed out high home values in Old Town, a shorthand way of suggesting that a small increase in property taxes could fund more complete sewer repairs. “They can’t afford a working sewer like everyone else?” his tweet said.

The men, all Democrats, accused each other of grandstanding. Eventually, the argument dribbled to a close.

“Obviously, we’re all concerned about the environment,” Skrabak said in an interview. “We’ve been trying to solve the problem. If it was a simple solution that was inexpensive, it would have been done years ago.”