Finding ways to address the shrinking supply of affordable rental housing in Arlington County would be the County Board’s biggest priority in 2013, chairman J. Walter Tejada (D) declared in January.

Two weeks before the year ends, the board on Saturday approved new temporary rental assistance for low-income residents who find themselves being priced out of their existing apartments, loaned a nonprofit developer $8.3 million to buy and preserve 101 apartments near South Glebe Road and I-395, and adopted a set of financial tools to preserve 6,200 existing affordable apartments in the neighborhoods along Columbia Pike.

The last set of votes fulfills a promise that the County Board made in July 2012, when it s members vowed that the same number of low- and moderate-income apartments would remain along the Pike even after the anticipated streetcar-driven growth takes place in the next 20 to 30 years. The vote was hailed as a “significant milestone,” by board member Chris Zimmerman (D), who said it “completes the planning and policy work on the Columbia Pike plan begun in January 1998.”

The demand for reasonably priced housing is high; in September, more than 3,000 people applied for 122 new subsidized apartments in South Arlington. Throughout the county, the increase in rents has outpaced wages earned by residents, a study released in late September found.

“Arlington County is absolutely committed to ensuring that even as Columbia Pike transforms into a ‘Main Street’ for south Arlington, it will remain diverse and affordable,” Tejada said in prepared statement. “Adopting these innovative new tools will help us meet our goal of preserving existing affordable homes and creating more.”

Arlington is already spending about $57 million this fiscal year for affordable-housing assistance in a variety of forms. It negotiates with developers to set aside some portion of its units in new buildings for people of low or modest incomes. The county also offers grants, including federal funds that used to be known as Section 8 vouchers, to low-income households, providing an average monthly subsidy of $548 to almost 5,000 families, including people with disabilities and the elderly. None of it has been enough to stem the tide of ever-rising rents.

The board voted unanimously Saturday to create a fund for transit-oriented affordable housing in the Columbia Pike area that will allow the county to pay infrastructure costs now borne by nonprofit developers who are trying to qualify for federal Low Income Housing Tax Credits. The money for this would come from a new tax increment financing fund, or TIF, which the board also established Saturday. That TIF would set aside 25 percent of the new tax revenue growth in the area to be used for affordable-housing projects along the Pike.

County staff estimated that under a “moderate redevelopment scenario,” the TIF would raise up to $5.6 million by 2020, or $16.5 million by 2024.

Board member Libby Garvey (D) was the sole vote against that portion of the plan, asserting: “It’s not free money. That growth should go into our general fund.”

“You’re not diverting funds, you’re capturing funds that wouldn’t otherwise be there,” Zimmerman said. “Our actions will cause greater growth and value . . . taking a portion of that increased wealth and dedicating it to mitigating the problems that the growth will create.”

The board also unanimously agreed to allow transfer of development rights for certain properties along Columbia Pike, in an effort to retain several historic and relatively low-cost garden apartment complexes. But other developers could also apply to move unused development rights to or from the Columbia Pike area, as well.

“This is really a big deal,” said Zimmerman, who has worked on transforming the Pike for 18 years. “We’ve been part of a movement, a leader in a movement” to show that building transit-oriented housing and walkable urban spaces could be financially and socially successful. Wider sidewalks, new community centers and renovated schools stemmed from the county’s efforts to encourage developers to build housing along major Metrorail and bus corridors, he said.

Keeping or creating affordable housing is not limited to Columbia Pike, and the board also agreed to create a countywide standard for assistance to tenants living in committed affordable units that are being renovated or redeveloped. It applies to those who make less than 60 percent of the area median income, or households of four making less than about $64,000. If the new rents will be higher than the current rents and the tenants would pay more than 35 percent of their wages toward housing, they could be eligible for aid.

A faith-based group, Virginians Organized for Interfaith Community Engagement, also presented the board with 10,000 signatures on a petition calling for the county to use some of its own land to help developers create housing for people who make less than half of the county’s median income. It asked for a list of all county-owned land and the three most feasible parcels where housing could go up.

Tejada promised a unanimous County Board statement on the request on Tuesday.