Fairfax County officials, faced with record volumes of building plans to review, have proposed hiring engineers from Bechtel Group Inc., one of the largest engineering firms in the country, to help handle the work.

The county plan to hire 10 Bechtel engineers for six months goes to the Fairfax County Board of Supervisors tomorrow. The board is expected to approve the $385,000 contract.

Fairfax, which has 15 of its own plan reviewers, has never before turned to the private sector for help in evaluating subdivison and site applications submitted by developers. But the county is in the midst of one of the most dramatic building surges in its history and has a large backlog of plans awaiting review.

On Friday, Director of Environmental Management Claude G. Cooper reported that the backlog had reached 338 plans. If no other plans were submitted, it would take the county more than 14 weeks to review those already submitted, Cooper said.

"The plan reviewers are under tremendous pressure," he said.

Under state law, the county has two months to approve or deny building plan submissions. But of the applications now pending in Fairfax, Cooper said, more than 100 were submitted more than two months ago, and a handful are four to five months old.

County officials said the extra engineers from Bechtel would help reduce the backlog, but they acknowledged it would take some time before they learned the county's review procedures.

"It's a help, not an overall solution," said Denton U. Kent, deputy county executive for planning and development.

Cooper said it would take three to four months before the Bechtel engineers, who would work in county offices, would be as effective as their county-employed counterparts. He said he expects that the Bechtel engineers will help reduce the county backlog of plans to a manageable level by early next year.

Developers say they are worried that the jam in the county's plan-reviewing process could delay construction and cost money in some cases. But county officials say they do not think the backlog has caused actual delays yet.

The county has relaxed its procedures for issuing clearing and grading permits, allowing developers to launch some building projects that have not yet been fully approved, Cooper said.

Although the contract with Bechtel is worth $385,000, county policy calls for recovering 85 percent of that expense from the developers in fees. The net cost to the county would come to about $55,000.

County officials have been reluctant to hire more full-time plan reviewers because of fears they would be idle when the building boom eased. "The development game is very . . . feast or famine," said Kent.

County officials said they are not sure who would be liable for a mishap connected with work done by Bechtel engineers.

"Nobody knows the liability issues," said Cooper. "There have been some things that made the lawyers a little bit nervous on this."