The Fairfax County Board of Supervisors on Tuesday asked Northern Virginia’s congressional delegation to spare transportation and social safety net programs from potential budget cuts of as much as 62 percent.

Chairman Sharon S. Bulova (D), in a letter Tuesday to Democratic Sens. Mark Warner and Jim Webb, along with Reps. James P. Moran (D), Gerald E. Connolly (D) and Frank R. Wolf (R), said proposed cuts could be particularly damaging this far along in the county’s fiscal year--and especially the deeper reductions already adopted by the Republican-controlled House of Representatives.

Not that the delegation needed any reminding , but Bulova also put in a word about how reliant Northern Virginia is on federal jobs and spending.

In particular, Bulova expressed concern that a plan to cut community development block grants could reduce Fairfax’ share by $4 million, or 62 percent, of its $6.5 million in block grants now. The money has allowed the county to provide affordable housing, repairs for elderly homeowners and other services, she said. Bulova also sounded a warning about the House plan to cut Head Start by $1.1 billion, saying it would mean a $1.1 million cut for Fairfax and more children added to the waiting list of 1,326.

The board also urged reconsideration of a proposal that would eliminate funding from the Workforce Investment Act that helps jobless people find work. The blow to the county would be $2.5 million.

Though some Northern Virginia officials have expressed doubt about whether Congress could slash so deeply, Bulova said she she is taking no chances.

“The loss of this funding — if we should lose as much as is on the chopping block — could be very, very serious,” Bulova said in an interview Tuesday evening. She said each dollar in federal funding helps to leverage many dollars more in state, county and nonprofit funding.

Although Fairfax is one of the wealthiest jurisdictions in the region, its caseloads for federal and state programs for low-income families, such as welfare, housing assistance, Medicaid and food stamps, have skyrocketed. Citing a study by the Weldon Cooper Center, Bulova’s letter says the average Virginia family needs to earn twice the federal poverty level in order to be self-sufficient. In Fairfax County, that means nearly 142,000 people do not earn enough to make ends meet. The county also has served 3,076 homeless in the past fiscal year — and this is only part of the human dimension that can be lost in abstract discussions of budget-cutting, Bulova said.

“It’s important that these are not just line items on a budget document,” Bulova said.

As for transportation, the board renewed its concern about the House’s elimination of $150 million for Metro. If the federal cut stands, Virginia, Maryland and the District are liable to hold back on matching funds, creating a “catastrophic” $300 million blow to the region’s subway.

The board also urged continued funding for Dulles Rail and highway improvements to accommodate some 19,000 workers who will be relocated to Fort Belvoir as part of the federal government’s base-closing program.