The Regional Waste Systems Board of Directors approved expanding the Scarborough ashfill and opting out of its contract with Casella Waste Systems next year during its meeting last week.

The move will save about $3.4 million over the next seven years and nearly $6 million over 25 years, according to General Manager Kevin Roche.

The major cost savings is trucking the material from Portland to Scarborough versus trucking material from Portland to other areas in the state such as Old Town with Casella.

“To transport waste ash to facilities not close by can be expensive,” Roche said.

Operating the expanded landfill will cost $26.7 million through 2014, but will not require an increase in fees since most of the money had previously been bonded. Additional sources include money remaining from other bonds as well as a budget surplus.

The RWS board tabled the issue last year to review all of its disposal options. The numbers for expanding the landfill were more favorable today than in the past because RWS decided to stop contracting with LR Higgins to operate the landfill, which saved the organization about $700,000 a year, Roche said.

Construction is expected to begin next month and RWS officials are in the process of finalizing the contract with SE Sergeant, of Stillwater, Maine, which was the low bidder. The maximum amount the construction will cost is a little more than $6.8 million. The expansion will entail a double lining to prevent leaking chemicals.

It will be completed by next January, at the same time when the contract with Casella expires.

The decision was unanimous, although only 22 of the board’s 29 members were present. The board members represent every town and city participating in RWS, including Scarborough, Cape Elizabeth and South Portland.