By Katherine Landergan, Town Correspondent                                                                                                                                                                                                                          

Harvard University reached tentative agreement on a contract with the Harvard Union of Clerical and Technical Workers Monday morning calling for an pay increase over the next three years.

On April 2, the approximately 4,600 union members will vote on whether to ratify the agreement, according to a letter written by the clerical and technical workers union. If ratified, the deal will be made retroactively effective July 1, 2012 through Sept. 30, 2015.

The tentative agreement came after roughly a year of negotiations.

“This is the most protracted and difficult negotiations we’ve had in 25 years together,” Bill Jaeger, director of the union, said Monday in a telephone interview. “It’s a big relief and a happy day.”

Jaeger said the union consists of non-faculty staff in office, laboratory, and library positions. He also said the agreement is “likely to be ratified by a lot” on April 2.

“Every idea and concern has been addressed,” he said. “I’m pretty confident that it will be a popular agreement among our members.”

According to the union, the deal includes a first-year salary increase, which provides a 3.4 percent raise for a union member who has worked at Harvard for a minimum of a year and receives an average full-time salary of $51,000.

If ratified, members of the union will receive two additional pay increases for 2013 and 2014 at the same rate, on Aug. 15, 2013 and Oct. 1, 2014 respectively.

All members of the union will be granted three “Option Days” – two for 2013 and one for 2014. An Option Day can either be taken as a personal day, or as a lump-sum payment equal to 75 percent of one day’s pay.

There are also a number of unresolved issues including healthcare coverage will be referred to the HUCTW-Harvard Health Care Negotiating Group, whose members will meet regularly.

The previous contract expired in June 2012, Jaeger said, and at the time he expected the negotiations to only take a few months.

“It’s been a long wait and uncertainty for our members,” he said.

In a joint statement issued by Harvard and the union, Marilyn Hausammann, Vice President for Human Resources at Harvard said that the university is pleased to have reached an agreement that is fair for both parties.

“We value and recognize the important role that HUCTW members play every day at Harvard, and we look forward to moving ahead together with the work of the University,” she said in the statement.

Jaeger expressed a similar sentiment. “It’s a good solid outcome for Harvard staff and very workable for the university,” he said.

Katherine Landergan can be reached at klandergan@globe.com. For campus news updates, follow her on Twitter @klandergan.