HAMPDEN – The company that runs one of Maine’s biggest landfills is preparing to ask permission to increase its 6 million-cubic-yard capacity by nearly half, boosting its life span by 10 to 12 years.

If trash keeps coming in at its current rate, the Pine Tree Landfill next to Interstate 95 and Coldbrook Road will be full in about two years, according to Casella Waste Systems Inc., which owns the landfill.

“It’s a fair amount of tonnage,” said Donald Meagher, Casella’s manager of planning and development.

Meagher confirmed Friday that Casella is preparing to apply to the state Department of Environmental Protection to license an additional 2.5 million cubic feet of capacity.

The entire landfill, including closed portions, holds about 6 million cubic yards, he said.

If approved, the extra capacity would be added through a system of “mechanically stabilized earth berms,” nearly vertical structures that are similar to retaining walls, Meagher said.

The technique “just allows you to get more use out of the same space,” he said.

The berms would retain waste that essentially would be packed onto the landfill’s sides. The technique, first used in Maine for waste management at a landfill in Norridgewock, would increase neither Pine Tree’s total elevation nor what environmental specialists call its “footprint.”

“We would be adding material to the side slope of the current landfill,” Meagher said.

Some cover material at the landfill would be removed during the construction, but working in stages would reduce the smell from waste, he said.

“We take it off a little at a time,” Meagher said, adding that some odors could result from temporary shutdowns to the landfill’s gas management system.

The same types of waste would be accepted with the approval of more capacity, and truck traffic would not increase, Meagher said.

If approved, the added capacity would boost the landfill’s expected useful life by 10 to 12 years, Meagher said.

The application would prompt review of the host community agreement Hampden has with Pine Tree, under which the town earns nearly $500,000 a year in waste disposal fees.

Hampden’s relationship with the landfill was buffeted during a two-year legal battle to prevent Casella from expanding Pine Tree several years ago. In 2000, Penobscot County Superior Court approved the expansion of 3.3 million cubic yards, declaring the landfill critical to the state’s solid waste disposal infrastructure.

Pine Tree is expected to meet capacity within two years, even though 350,000 tons – 60 percent of the landfill’s annual tonnage – will be diverted annually to the West Old Town Landfill, Meagher said.

The state took ownership of the West Old Town Landfill in February 2004. The deal among the state, Georgia-Pacific Corp. and Casella was designed to keep G-P’s Old Town paper mill open while addressing the state’s waste disposal problem.

The state bought the landfill site from G-P for $26 million and chose Casella to operate it.

Pine Tree’s plans come as no surprise to town officials, who had hoped the relief provided by the West Old Town Landfill would delay the need for more space in Hampden, according to Town Manager Susan Lessard.

“The landfill has been upfront about the fact that they were filling faster than they initially anticipated,” Lessard said Friday. “I had hoped that more time would elapse.”

After the town receives an application from Pine Tree, it will be forwarded to the town’s landfill oversight committee, which will then report to the Town Council, Lessard said.

“We will thoroughly review anything that comes to us,” she said.

Meagher said he plans to attend Monday’s Town Council meeting to answer questions about the proposed application.

“I know landfills are always a controversial topic,” Meagher said.