FROM 1905 to 1985, D.C. residents drank water that was drawn from the Potomac River and filtered through sand in underground chambers at the McMillan Slow Sand Filtration Plant, a 25-acre site in Northwest Washington. In 1985, the Army Corps of Engineers constructed a chemical plant across the street to replace McMillan, and the federal government, which owned and operated the plant, designated it as surplus. In 1987 the District purchased the site for $9.3 million.

The city planned to develop it, but a debate between those seeking to preserve McMillan and those aiming to repurpose the land has kept the grounds chained-off, disused and deteriorating. Remaining are 20 underground filtration cells built with unreinforced concrete, surface-level cylindrical buildings that were used to store clean sand, some 100 manholes with exposed or rusted covers and a number of other wooden and brick structures. The industrial jungle is vine-covered and in varying states of disrepair. In 2000, the cost of preserving and reinforcing all 20 cells was estimated at $45 million.

The city proposes to convey much of the site to a commercial partnership that would develop the land for mixed use. There would be a park with a community center; townhouses and apartments (with 10 percent of units set aside for affordable housing); a 50,000-square-foot grocery, and office and retail spaces to support the nearby hospital complexes. (Children’s National Medical Center, the VA Medical Center and Washington Hospital Center are across the street.) Two of the underground cells would be preserved, and about eight acres would be devoted to public space. The package comes with a 2025 estimated completion date, though the District projects that certain buildings would “come online” by late 2016.

Opponents of the plan want to keep more of the old infrastructure; one suggestion would preserve five or six of the cells for use in restaurants, shops and offices. Preservationists are right that the structures are unusual and evocative. But the alternative plans are short on practicality and funding. It’s been seven years since the District solicited proposals and six since it awarded development rights to Vision McMillan Partners. They’ve come up with a reasonable combination of useful development and respect for the past and for open space. It’s time to get moving.