The Andrew Adkins public housing apartments in Alexandria are scheduled to be redeveloped. (Patricia Sullivan/The Washington Post)

The escalating cost of construction and dramatic changes in how affordable housing is ­financed are leading Alexandria officials to consider modifying a requirement to replace any of its 1,150 public housing units that are redeveloped with equally priced apartments.

A change is necessary, proponents say, because local housing authorities such as the Alexandria Redevelopment Housing Authority can no longer afford to simply replace an apartment priced for the poorest residents — those who make less than 30 percent of the area’s median income, or $26,500 for a two-person household — with another unit priced for the same income level.

Instead, ARHA proposes to either build more housing for people higher on the income ladder to subsidize the rents of the poorest tenants or to get substantial additional financial support from local, state or federal governments.

“We need a broader spread of [household incomes] if we are to do the job without deep subsidies,” Roy Priest, ARHA’s chief executive, told the City Council last week.

Priest, who is retiring at the end of this month, said the long erosion of federal housing subsidies, which is expected to worsen under President Trump’s administration, as well as the emergence of independent affordable housing organizations, has boosted competition for scarce federal tax credits, which support almost all affordable housing development in the nation.

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Changing Alexandria’s 36-year-old promise to preserve the number of housing units for its poorest families at affordable rents would break a social compact, affordable housing advocates say.

“At the time this law was passed, it was never envisioned that public housing authorities would be losing their funding from the federal government,” said Michelle Krocker, executive director of the Northern Virginia Affordable Housing Alliance. “We need to be sure any solution provides housing in perpetuity for these extremely low-income people, because we know these are the hardest populations to serve.”

While existing tenants would be protected from losing their housing even if the policy is changed, the supply of housing for the poorest residents would undoubtedly dwindle, even as population growth and income trends in the region guarantee that the need will increase.

Krocker said the proof will be in the details of whatever is proposed and whether the cash-strapped city can persuade other entities — and offer subsidies — to build housing that’s needed when the existing 1,150 units are not enough.

Alexandria and the greater Washington region are not alone in grappling with the increasing cost and declining federal support for affordable housing.

“It is going on all over the country, particularly in urban and suburban markets experiencing growth,” said Stephen Glaude, president and chief executive of the Coalition for Nonprofit Housing and Economic Development.

A low-income housing project requires five to seven different types of subsidies to get off the ground or “the math doesn’t work,” Glaude said.

Unique to Alexandria, the local law known as Resolution 830 has guaranteed that this small city would always replace, on a one-for-one basis, any of its lowest-income apartments lost through decay or demolition. Far larger Fairfax County, the only other Northern Virginia community with a public housing authority, provides 1,060 low-income rentals and makes no promise similar to Alexandria’s.

Most communities in the region, including Alexandria and Fairfax, support affordable housing projects with grants or loans. Those projects are usually financed in the expectation of having tenants whose incomes range from 40 to 80 percent of the area’s median income, or up to $88,300 for a two-person household. Apartments at the high end of that range are often called “workforce” housing, because tenants with full-time jobs can qualify.

Much rarer are the developments that offer apartments for those who make less. The federal government provides housing vouchers, previously known as “Section 8” vouchers, but they are hard to get, and it’s up to tenants to find landlords willing to take them — an exceedingly difficult hunt in an area where rental costs are rising.

While it will be at least the end of the year before any changes are proposed for Resolution 830, ­Alexandria Housing Director ­Helen McIlvaine said the issue is coming up now because officials are trying to avoid the tempest that erupted in late 2015 and early 2016, when ARHA’s plan to re­develop the 15-unit Ramsey Homes public housing project ran into a buzz saw of neighborhood and political opposition.

That brouhaha delayed the agency’s application for federal tax credits by a year. After multiple meetings, the city and the housing authority agreed to a “no surprises” rule in the future.

ARHA wants the City Council in the fall to approve a redevelopment of the 48-year-old Andrew Adkins apartments just east of the Braddock Road Metro station. The housing authority plans to sell the two blocks of land beneath the apartments to a private developer, who wants to build 500 market-rate units in seven-story buildings, with ground-level retail.

The developer would also build a new public housing tower, to be run by ARHA, but only 60 of the current 90 units would be replaced. ARHA officials said they would use the money they earned from the land sale to buy or rent housing elsewhere for the remaining 30 tenants.

The East Braddock area is rapidly gentrifying and has acquired the nickname of Old Town West. New apartment and condominium towers have gone up amid older, low-income apartments, and several middle-to-high-end restaurants have opened nearby.

While public housing residents sat outside one recent evening barbecuing on a tiny grill, with laundry drying on their clotheslines, more affluent neighbors two blocks away played bocce ball and outdoor ping-pong under strings of lights.

That idea of modifying Resolution 830 did not go over well with City Council members who were briefed on it at a workshop last week.

Mayor Allison Silberberg (D) objected to both the possible abandonment of the resolution and to the reduction of public housing units at Andrew Adkins. Council member Willie Bailey (D) said the four plots of green space at the site should be sacrificed to add more housing.

“They’re going to build 500-plus homes, and all we’re getting out of it is 60 units?” Bailey asked. “I know we like to talk about open space, but people can’t live in open space.”

Canek Aguirre, president of the board of Tenant and Workers United, said his organization opposes the proposal for Andrew Adkins but has a “wait-and-see” attitude toward the idea of changing Resolution 830, because it’s still in preliminary stages and community reaction will be solicited before anything happens.

Vice Mayor Justin Wilson (D) told the council that if it wants to retain the one-for-one replacement of the lowest-income apartments, “someone . . . has to show up with a lot of money.”

“This is our choice. This is our decision,” Wilson warned. “We could have [fewer] units with deeper affordability or more units with less affordability. . . . That is the brutal math.”