DURHAM — After working three years without a contract, the town and the union representing public works employees has reached their fourth tentative agreement, which still must be agreed upon by both parties.

The proposed agreement would increase the work week from four to five days, increasing salaries beginning next year while increasing insurance premiums with a new health plan, according to a release by the town.

The previous collective bargaining agreement between the town and Local 863 of the American Federation of State, County and Municipal Employees, which represents members of the public works department, expired Dec. 31, 2009.

Since that time, three tentative agreements have been reached, but were all voted down — twice by AFSCME members and once by the Durham Town Council. After an impasse earlier this year, the two sides agreed to enter into mediation, according to the release.

The latest agreement, which is a result of a lengthy mediation session held Sept. 10, will be brought before the AFSCME members Tuesday. If ratified, the agreement will be presented to the Town Council for a ratification vote, scheduled for Oct. 15, according to the release. If approved, the agreement would result in no pay increase for the last three years, but would rise by 2 percent, each year from 2013 to 2015. Additionally, union members would receive a one-time signing bonus of $750 upon ratification, according to the release.

The agreement would also change health plans from Anthem to Cigna Insurance, which would become effective Jan. 1. While the Cigna plan is less costly, employees would see increases in premium contributions.

Beginning Jan. 1, all DPW employees would be on a five-day work week, which is a change for the many members who work four days. The town feels this will help “optimizing efficiencies within the department,” according to the release.