HAMPDEN – The state’s largest waste management corporation has offered to cease future expansion at its Pine Tree Landfill and limit the amount of out-of-state waste it brings into Maine.

In exchange, Vermont-based Casella Waste Systems Inc. wants the state to give it the green light on three projects it has in the works, including an already proposed expansion at Pine Tree.

Casella made the offer in an application filed this month with the state Department of Environmental Protection. The application, which seeks to demonstrate the landfill’s benefit to the public, was required by the DEP as part of Casella’s plan to increase capacity at Pine Tree by nearly 50 percent.

If approved, the increase would be the last at the Hampden landfill, even though the site could accommodate much more growth, Don Meagher, Casella’s manager for planning and development, said Tuesday.

The offer is a good-faith effort by Casella to demonstrate that the corporation recognizes concerns about waste coming to Maine from out of state, Meagher said.

“We’re willing to walk halfway across the stream as long as people are willing to meet us halfway,” he said. “We are leaving a lot of capacity and a lot of business on the table.”

The DEP has until mid-January to issue a decision on the public benefit application. DEP project manager Cyndi Darling said Tuesday it’s too early to comment on the application, except to say that the public benefit of the proposed increase at Pine Tree, dubbed “Phase 9,” must be established before moving forward.

“We felt that it was appropriate to revise the public benefit determination prior to the Phase 9 application itself,” she said.

In addition to the Pine Tree project, Casella’s offer also hinges on DEP approval of an expansion at the West Old Town Landfill and its pending contract with the city of Lewiston to operate its landfill.

In return, Casella would freeze the amount out-of-state waste it accepts in Maine to the current rate, or just under 500,000 tons per year.

Waste from out of state now is accepted at Pine Tree, a commercial landfill situated along Interstate 95 and Coldbrook Road, and the Maine Energy Recovery Co. in Biddeford, also owned by Casella.

The 500,000-ton limit would exclude any construction and demolition debris brought to Maine to be processed for wood fuel, Meagher said. As part of its deal with the state to operate the West Old Town Landfill, Casella agreed to provide the Georgia-Pacific paper mill – now being sold to Koch Industries Inc. of Wichita, Kan. – with 100,00 tons of wood fuel annually, he said.

Limiting some of Casella’s operations in Maine is a generous offer but one Casella didn’t have to make, Meagher said. The corporation continues to oppose the DEP’s decision to require a public benefit application in the first place.

DEP and Casella officials agree that the proposed growth at Pine Tree is not technically an “expansion” by the state’s definition, meaning neither the footprint nor the total elevation of the landfill would increase.

Casella argues that because it’s not an expansion, the project avoids the usual requirement for a public benefit determination. But the DEP says the law is silent on the issue, and the project is significant enough to warrant proof that it would benefit the public.

Casella also objects to the DEP’s requirement that it provide information on disposal rates for out-of-state waste at Pine Tree, Meagher said. The commercial facility is protected by interstate commerce rules that prohibit such regulation, he said.

The amount of out-of-state waste accepted at Pine Tree, however, is key to understanding how the facility serves Maine’s waste disposal needs, the DEP has argued.

As evidenced by several footnotes included in the application, Casella is keeping its legal rights in mind while extending the offer to reduce some operations. The corporation is “being cooperative but reserving the right to be uncooperative,” as Town Manager Susan Lessard put it Tuesday.

Lessard said she fears comments from the community to the DEP on the public benefit application could be lost in the mix if a legal challenge ensues.

“All those footnotes mean that there’s more to come,” she said.