For years, D.C. leaders’ quest to develop a 25-acre property in Northwest Washington has been stymied by activists whose legal maneuvers have mired the project in lengthy court challenges.

But Mayor Muriel E. Bowser (D), eager to add hundreds of housing units to the city’s supply, has attempted a maneuver of her own as she pushes to transform the McMillan Sand Filtration Site, among the city’s largest undeveloped tracts of land.

An appeals court late last month cleared the way for demolition to begin on the landmarked property after the D.C. Council — at the mayor’s behest — passed legislation requiring that the project “proceed expeditiously and without further delay.”

“The revitalization of McMillan is underway!” John Falcicchio, the deputy mayor for planning and economic development, crowed after the ruling in a tweet that included photos of what appeared to be demolition work at the fenced-off site.

The D.C. Court of Appeals decision prompted criticism from the project’s opponents, as well as a leading preservationist, who contend that the mayor and council, by enacting the law, influenced the court and allowed demolition to begin on a historic property without subjecting the developer to required scrutiny.

“While this may be legal, it certainly appears unethical,” Kirby Vining, an opponent who lives near the site, wrote in a letter to the council, demanding that it rescind the legislation.

Falcicchio, when asked, declined to respond to the criticism, citing an upcoming court hearing on whether the city issued the demolition permits properly. But Council Chairman Phil Mendelson (D), who supported the legislation to push the development forward, said it needs to progress after seven years of reviews and litigation that “is about stalling, obstructing, delaying the project.”

“Enough is enough,” he said in an interview. “We’re making a statement that going forward with this development is in the public interest.”

A debate over development

Bowser’s advocacy on behalf of McMillan is part of her campaign to encourage the building of 36,000 residential units citywide by 2025. She has touted the goal as necessary to expand the housing supply in a city where home prices have soared in recent years.

At the intersection of Michigan Avenue and North Capitol Street NW, McMillan once hosted the city’s main water filtration system, a network of 22 vast catacombs beneath acres of grass and 20 concrete silos that still exist on the property.

The parcel, which has been referred to as McMillan Park, is at the center of a neighborhood largely defined by four hospitals, streets lined with rowhouses, the adjoining McMillan Reservoir and its sloping grounds designed by the son of the famed 19th-century landscape architect Frederick Law Olmsted.

Under the $720 million plan approved by the city, the development team — Jair Lynch, Trammell Crow and EYA — would build 655 residential units, including 134 subsidized apartments, offices, retail, and a supermarket. There would also be an eight-acre park and a 17,000-square-foot community center with an indoor pool.

Two grass-roots groups opposing the plan, Friends of McMillan Park and the Save McMillan Action Coalition, have long argued that the development would overwhelm the area with traffic and pollution, and would raise home prices and property taxes for neighbors already facing mounting economic pressures.

Since the council passed the McMillan bill, Friends of McMillan Park sent a mass email to thousands of the group’s supporters urging them to petition Congress, including Republicans who oversee D.C. legislation, to “reverse this monstrous law that is demolishing our park!”

The project’s opponents, including Chris Otten, an activist who has organized opposition to numerous development plans across the city, staged a protest on Monday outside Mendelson’s house that drew a dozen demonstrators.

“McMillan is another tool that will promote displacement,” said Lark Yasmin, 38, a tenants’ rights activist who joined the protest. “A lot of my neighbors and people I know have been pushed out of the city.”

But others, including D.C. Council member Kenyan R. McDuffie (D-Ward 5), whose district encompasses the McMillan site, view the project as delivering long-sought necessities to a neighborhood with no supermarket or restaurants.

“We’re paying all this tax money and we don’t have nothing,” said Alice Thompson, 75, a neighborhood resident, as she walked her poodle around the perimeter of the McMillan property. “I want everything they’re talking about putting in here.”

Cheryl Cort, policy director for the Coalition for Smarter Growth, a group that advocates for high-density development, described the McMillan project as “terrific” and said it is essential for adding needed housing to the city’s supply.

“We need to build more housing and affordable housing,” Cort said. “Reducing future housing options is not going to help us.”

But Parisa Norouzi, executive director of Empower DC, a nonprofit that advocates for low-income families, said not enough of the affordable units in the McMillan plan are for the city’s poorest residents.

Of the 134 affordable units, 11 are for households earning 30 percent of the area median income — or about $38,700 for a family of four. The remainder of the units are for households earning at least 50 percent of the area income, or about $64,500 for a family of four.

“We’re not building for the people who need it the most,” she said.

Court battles

When it opened in 1905, after three years of construction, the McMillan site was regarded as a marvel of late 19th-century public works design, creating a filtration system for water that arrived from the Potomac River before reaching homes across the city, including the White House.

After a new filtration system forced McMillan’s closing in 1985, D.C. officials and a variety of groups considered a multitude of possibilities for the property, including housing and a park. One group sought to have a memorial placed on the site for dogs that died in wars.

In 1991, the city’s Historic Preservation Review Board designated the entire parcel a landmark, adding another layer of review that would be required for a proposed development.

In 2014, eight years after the administration of then-Mayor Anthony Williams chose a development team, the D.C. Zoning Commission approved the plan for McMillan that remains in place.

In 2016, Bowser and McDuffie hosted a groundbreaking at the site, predicting that the project itself, as well as the development, would generate more than 6,000 jobs.

But the next day, D.C.’s highest court, responding to an appeal filed by the project’s opponents, blocked the development from proceeding. The court ruled that zoning officials had approved the plan without adequately considering whether it would potentially contribute to displacement in the neighborhood.

Three years later, after zoning officials approved the project a second time, the court ruled that it could proceed.

But opponents raised another point of contention, arguing that the city had issued demolition permits without adequately reviewing whether the development team had the finances to complete the project — a requirement on landmarked properties.

After an administrative law judge ruled in the city’s favor on that argument, the project’s opponents turned to the appeals court, which has scheduled a hearing for Oct. 26. But the court lifted an injunction last month that had blocked demolition on the property at the request of city attorneys who cited the council’s McMillan legislation.

Rebecca Miller, executive director of the D.C. Preservation League, said the “last-minute maneuvering” by Bowser and the council showed they are “willing to usurp the public process to achieve their desired result.”

“This action disregards long-standing rules and regulations that are in place to ensure that communities who lose historic properties will receive the promised development,” she said. “This precedent puts all landmarks at risk in the District of Columbia.”

Mendelson said he would appreciate the concern if “we were talking about a small-time developer or a homeowner where the existence of a landmark is in jeopardy and ensuring the financial wherewithal to complete the project make sense.”

“Here, it doesn’t make sense,” he said, “because the developers behind this are large and well-resourced.”