Following a marathon 13-hour negotiating session, the county and its largest union compromised late Tuesday on a two-year tentative contract that gives a pay raise to county workers.

Formal approval of the agreement hinges on the votes of union members, which could come in mid-August, but union leaders said their negotiators are recommending approval of the contract.

“Definitely both sides of the table had to do some give and take,” said Carlos Rivera, a spokesman for Service Employee International Union 1021.

Details of the deal include:

• A 3.2 percent wage increase this year, including an evenly distributed amount of retroactive wage increases dating back to June 30 — to be distributed in one lump sum.

• Probation officers and juvenile hall counselors eligible for state safety retirement will receive a safety premium pay of 5 percent.

• The county and union workers will share in paying for increased health care costs in 2008 for workers with dependents.

• The county will increase its uniform allowances for specific classes of county workersto between $500 and $700.

The move follows a series of rallies over the last month and a half by union workers who contemplated a strike if the county didn’t provide concessions to their demands, which included a 4.2 percent cost of living increase and safety retirement for probation officers and juvenile hall counselors. An impasse led to negotiations helped along by a state mediator on Tuesday.

In a statement, County Executive Officer Nancy Watt said the deal was fair.

“I am very pleased that we were able to arrive at a package that everyone agrees is fair,” she said. “This agreement demonstrates mutual respect and teamwork, and allows us to continue our collective mission of serving Napa County residents in a fiscally responsible way.”

While union leaders say they are satisfied with the deal, Rivera added that many union workers were dismayed at the way County Supervisors handled the process. Rivera noted there were two supervisorial seats — Mark Luce’s and Harold Moskowite’s — that were going to be in a competitive election in 2008.

“Our members are seriously considering the options when it comes to those two seats,” he said.