The view of an artificial turf field built atop a new addition to the Alexandria Wastewater Treatment plant in Virginia. (Linda Davidson/The Washington Post)

Eighteen million gallons of sewage swirl in storage tanks beneath the new athletic field and bike trail in Alexandria’s Carlyle-Eisenhower East neighborhood, awaiting treatment so it can be released into a tributary of the Chesapeake Bay watershed.

But athletes who are slated to use the field starting this winter will not smell anything — except perhaps their own sweat — promised officials with Alexandria Renew Enterprises, the Virginia public utility that owns the field and the tanks below it.

“No smell” was a condition of the city government’s approval of the utility’s plan to build the six holding tanks, which slow the flow of wastewater so the biological treatment plant can process it more efficiently.

Karen Pallansch, Alexandria Renew’s chief executive for the past 10 years, said that keeping the air odor-free is also part of the organization’s mission.

Unlike Washington’s much larger Blue Plains Advanced Wastewater Treatment Plant, which periodically bathes Old Town Alexandria in a malodorous scent, Alexandria Renew uses microorganisms to absorb the nitrogen and other elements that can cause a foul smell.

The new headquarters for Alexandria Renew Enterprises, which stands next to an artificial turf field built atop six wastewater treatment tanks. (Linda Davidson/The Washington Post)

The utility spent $11 million to launch that process in 1999, expecting that the land surrounding its facility would one day be home to offices, residences and people who might recoil at the smell of sewage.

“It takes several 100-degree days in a row, or an unanticipated facility failure, to smell us,” Pallansch said Friday during a tour of the 33-acre site. “When it does smell, it smells like your grandma’s closet — sort of musty.”

The idea of placing an artificial-turf field on top of a wastewater treatment facility is apparently unprecedented, Pallansch and others who work in the industry said, even though athletic and recreational facilities have been built atop school, office and residential buildings in space-starved areas across the country for years.

In the case of Alexandria Renew, city planners and elected officials wanted to lessen the industrial feel of the neighborhood, which is visible from the adjacent Capital Beltway, close to Route 1 and home to the city jail.

They also were eager for new recreational space.

“We have a shortage of athletic fields and a fairly large unmet need for adult community sports because so many of our fields go to children and youth,” said James Spengler, the city’s parks director.

The field is regulation size for soccer, with a grassy hillside for spectators in the northwest corner. It will be used for adult league games starting in February, when the next season begins.

Alexandria Renew Enterprises chief executive Karen Pallansch stands next to odor filter tanks. (Linda Davidson/The Washington Post)

The city and the utility are co-hosting a family festival at the site, in the 1800 block of Limerick Street, from 11 a.m. to 4 p.m. Saturday.

Some Alexandria residents sought to move high school football games there from T.C. Williams High School’s Parker-Gray Field, where neighbors had objected to field lights. But city planners said the Alexandria Renew site did not have enough room for bleachers, locker rooms, goal posts, scoreboards and concessions.

Ambulances and firetrucks are too heavy to drive onto the field in case of an emergency, officials said. There is no bus parking, and other nearby parking is limited.

The storage tanks are in a building that is mostly underground but rises about one story above the surrounding land.

The tanks isolate liquids for four to eight hours before they are transferred into biological reactor basins, where microorganisms gobble up excess nitrogen that would be harmful to the bay.

“The cost of the nutrient management facility for treatment purposes is $92 million,” Pallansch said, adding that the field and its accessories cost less than $1.5 million. “Those costs were offset through the transfer of development rights and sale of property with our development partner, Carlyle Partners.”

Although Pallansch said the tank-field project was the most complex that she has worked on, she also described it as the most rewarding.

“Our industry is 99 percent invisible. Nobody knows us, and when they do, they think we’re yucky,” she said. “Now we really have the chance to be a more visible part of the community.”