Negotiators for Erie County Executive Chris Collins and the county’s largest union have agreed on a proposed contract granting a 15 percent raise over five years if those in the bargaining unit give back two paid holidays and work full days in the summer. Recently hired employees also would help pay for their health insurance when they retire.

The contract, which requires other concessions, would affect nearly 4,200 Erie County employees represented by Local 815, Civil Services Employees Association. The workers are spread through the government, the library system, Erie Community College, Erie County Medical Center and its Erie County Home.

In addition, the terms could apply to dozens of non-unionized appointees, the managerial confidential class, who generally follow the terms of CSEA pacts. But a spokesman for the county executive said Collins hasn’t decided how the contract should affect that group of employees. Those appointees already contribute to their health insurance premiums and forgo the “summer hours” benefit.

Members are to vote on the deal June 8, after informational meetings June 3.

The CSEA local had vocally opposed givebacks. Statewide President Danny Donohue attended a rally here months ago to support the local and to protest Collins’ practice of eliminating certain county services and the jobs for those who provide them. The union later declared it was at an impasse with the county.

But over several months, negotiators found common ground. Collins was savoring the potential accord Thursday morning, just hours after his negotiator, Labor Relations Director Chris Putrino, signed the proposal late Wednesday.

“I was not optimistic we would be here,” Collins said, referring to the early opposition from Local 815, but he added later, “I knew time would be our friend.”

Collins’ foremost challenges when taking office in 2008 included drawing up a new generation of labor agreements with the county’s unions, since all their contracts had expired.

He needed to deal with the mushrooming multimillion-dollar obligation to pay the full cost of retiree health care, a benefit awarded early in the last decade, if the unions would agree to a single health-insurance provider.

New agreements with the New York State Nurses Association and Local 1095, American Federation of State County and Municipal Employees, the blue-collar union, start eroding the benefit for newer employees. A proposal to the Teamsters union, which represents Holding Center deputies did the same, but the Teamsters rejected the agreement.

If CSEA members approve the proposal, Collins said Thursday, 85 percent of the county’s employees will be under a contract through 2015, which would be the last year of his second term if he is reelected next year.

Joan Bender, the CSEA local’s president, did not return a telephone message seeking comment, but Collins said the union leaders have taken a neutral position on the proposal.

The proposed contract establishes three tiers of employees for retiree health care, according to Collins.

Those hired before Dec. 31, 2006, still would be allowed free health care in retirement. Those hired after Dec. 31, 2006 — when the prior contract expired— would pay half of their retirement health care costs. Employees hired after the ratification of the new agreement, perhaps June 8, will not receive county health insurance in retirement.

Further, new employees will pay 15 percent of their health insurance, and current employees will pay 15 percent of their health insurance increases.

The union would surrender Columbus Day and Election Day as paid holidays, and new employees would give up two personal days, Collins said.

Summer hours, the tradition that had allowed unionized county employees to leave work a half hour early in July and August and get paid for the time, would end for all CSEA employees in 2011. The union also would agree to work with county managers to establish a dress code.

Collins agreed to let employees cash in their unused vacation time, up to 40 hours, each year. He will eliminate the cash payments that go to employees who waive the county’s health insurance because their spouse is also on the county payroll and receives family coverage.

To deal with the years that the CSEA local went without a contract, the county would give each employee $500 cash for each of 2007, 2008 and 2009. Those payments would cost around $4.2 million. Collins expects that the federal and state governments will cover half that cost as they help pay for the workers who administer state and federal programs.

He will ask the county’s state-appointed control board to cover half of the remaining $2.1 million with the efficiency grant money the board can spend. The control board, which monitored the talks with the CSEA, has helped pay the start-up costs of other labor agreements.

The medical center assigned a representative to the negotiations, as required under an agreement with county government. The library system, which has been looking for more aid from Collins, has been briefed on the terms.

“As far as affording it, we have been very conservative in our budgeting assuming that these contracts will be negotiated,” Library Director Bridget Quinn-Carey said Thursday. “That’s always in the backs of our minds.”

For this year, workers would receive a $750 addition to their base pay, which would begin at ratification. The addition would then be used when figuring their 3 percent raise next year, to be followed by annual 3 percent raises through 2015.

Collins agreed to drop his practice of placing new hires in “regular part-time” jobs, a designation that lets him work the employee up to 39 hours a week while providing half the paid leave that a full-timer receives. Nearly 300 such employees would get full-time status.