Collage City Studio’s plan for the McMillan Sand Filtration Plant includes an "urban beach." (Collage City Studio)

The debate over redeveloping the McMillan Sand Filtration Plant is much like other land-use disputes, with high emotions on both sides. But opponents of a city-backed scheme to build a mixed-use project on the historic property have something that most development adversaries don’t: a plan of their own.

That plan was devised by Collage City Studio, a pro bono group headed by Catholic University architecture professor Miriam Gusevich. She has been consulting since 2000 on the 25-acre parcel, whose northeastern corner borders the intersection of North Capitol Street and Michigan Avenue NW. Last year, Gusevich updated her proposal with the help of four of what she called her “best students”: Joseph Barrick, Filipe Da Silva Pereira, Peter Miles and Nina Tatic.

“The idea behind our plan was that, when the community said, ‘No, we don’t want what the city’s giving us,’ they could have something to point to and say, ‘We want something like this,’ ” Miles said.

Built to filter drinking water taken from the Potomac, the facility opened in 1905. The next year, it was designated as a memorial to Sen. James McMillan, whose “city beautiful” principles shaped 20th-century Washington with the McMillan Plan. Partially designed by celebrated landscape architect Frederick Law Olmsted, the site became a historic landmark in 1991.

The plant has been unused since 1985 and was sold to the city in 1987. What remains on the site appears to be mostly open land, aside from two sets of silos once used for storing sand. Actually, Gusevich said, it’s “one of the country’s largest and oldest green roofs.” Underneath are 20 vaulted cells whose interiors Gusevich compared to “the mosque in Cordoba. It’s just phenomenal. The quality of the space is incredible.”

All but two of the underground cells and much of the greenery would vanish under the plan favored by the city’s Office of the Deputy Mayor for Planning and Economic Development. It has signed an exclusive rights agreement with Vision McMillan Partners, a consortium of Trammell Crow Company, Jair Lynch Development Partners and EYA.

There are still two potential obstacles to that group’s design: The D.C. Council must vote to declare the land surplus, and the Historic Preservation Review Board must approve the proposed alterations.

“The city has yet to make a case why all the vaults have to be torn down,” Gusevich said. “In fact, they are using vaults to hold water right now for the water department. You can’t have it both ways. Either the structure is so damaged that it cannot be used for anything, or, if it’s still viable to be used for water, that means it’s in good enough condition to be used for something else.”

The professor concedes that the southeast corner of the plant has been undermined by the action of a submerged creek. Collage City Studio’s plan would demolish that section of the vaults, remove an earthen berm and make a new entrance to the subterranean structure.

“It’s like a split-level house,” Gusevich said. “You can enter from the upper level; you can enter from the lower level.”

To take advantage of the low-level southeastern section, Collage City Studio would create an “urban beach.” That part of the design was later incorporated into Vision McMillan Partners’ plan.

D.C. Council member Kenyan McDuffie (Ward 5), who represents the neighborhoods east of the site, could not immediately be reached for comment.

Although the proposal advanced by Gusevich and her students would include a larger community center and more open space, it would not forgo development. Both plans contain medical office buildings to serve nearby hospitals, including Washington Hospital Center and Children’s Hospital. But Collage City Studio proposes erecting some structures on the north side of Michigan Avenue, on current parking lots.

“We’ve tried to develop this sort of in tandem with [Vision McMillan Partners’] plan, as a counterpart,” Miles said. “So we can say, ‘This is roughly equivalent to what they’re proposing; we just think it’s done a lot better.’ ”