Stonington — The K-12 School Building Committee has accelerated the time line of the $69 million elementary school expansion and renovation, a move that is expected to save taxpayers about $2.5 million in bonding costs.

In addition, the committee is finalizing a construction management contract with Gilbane Inc., the same firm that oversaw the $39 million renovation and expansion of the high school.

Residents overwhelmingly approved the elementary school project at a spring referendum. Committee Chairman Rob Marseglia said the initial plan was to wait for state reimbursement to be approved next June and then begin the design process. This would have meant the project would be completed in the fall of 2019.

But by beginning the design process now while the state is reviewing the town’s application, the project could be completed in the fall of 2018.

Because construction costs are expected to increase 5 percent a year, shortening the time frame will save between $2 and $3 million.

Marseglia said the project architect, DRA Associates, said there is low risk of beginning the design now because the state traditionally meets it obligations for school construction funding. He added DRA told the committee the strategy is used by many towns to save money.

“We’re trying to be smart with the money that the taxpayers entrusted us to spend,” he said. “If we can return that money to the town we will.”

Marseglia said the committee does not plan to use the savings to add additional items that were not part of the approved project.

He said DRA will soon begin collecting input from school staff as it begins detailed construction drawings.

The project, which calls for the renovation of Deans Mill and West Vine Street schools, will cost taxpayers $52.3 million after state reimbursement.

The plan also calls for closing 115-year-old West Broad Street School and moving fifth-grade students from the middle schools back to the elementary schools. The project is designed to get another 50 years of life out of the two 48-year-old buildings.

Marseglia said the committee selected Gilbane as the construction management firm from a field of nine companies in part because of the “good will that was developed with the high school project.”

“We have a level of comfort and confidence with Gilbane for delivering a good product with the high school. We expect that same competency and professionalism with this project,” he said.

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