OLD TOWN, Maine — Juniper Ridge Landfill in Old Town is expected to fill in less than seven years at the current rate of disposal, which is prompting Casella Waste Systems — the company hired to operate it — to prepare an expansion plan.

“Literally since 2005, we’ve been at this,” Don Meagher, Casella’s manager of planning and development, said on Thursday at the company’s fourth and final “Milestone Meeting” in advance of filing their expansion plans in 2015.

The state acquired the former Georgia-Pacific Corp. landfill in May 2003 to help keep the Old Town mill operating and selected Casella to operate the facility. It was renamed Juniper Ridge Landfill in 2005, after the state and Casella acquired a permit to increase its capacity from a 3 million cubic yard landfill to one that could handle 10 million cubic yards of trash.

In January 2012, Casella and the state received partial approval from the state DEP to pursue an essentially doubling of Juniper Ridge’s capacity by adding 9.35 million cubic yards at the landfill, according to Meagher.

The Maine Department of Environmental Protection estimates Juniper Ridge will reach existing landfill capacity in 2019, at current fill rates of 675,000 tons annually. Based on this usage, the DEP projects that the 9.35 million cubic yard expansion would extend the landfill’s life by eight or 10 years.

“Now we’re starting to prepare the [expansion] paperwork,” he said, adding the milestone meetings are being held to get feedback from interested parties, including Old Town and Alton community leaders, representatives from DEP, engineering and other support companies working with Casella and the state, and active concerned residents.

“The plan is to file the [expansion] application in July,” Meagher said.

The topics of Thursday’s meeting was the liner planned for the expansion at the 64-acre property located near exit 199 on Interstate-95, and Casella’s plans for collecting gas that escapes from the landfill.

Input from the previous milestone meetings has led to changes in monitoring and noise, including changing the backup alarms on the heavy equipment to ones with a different frequency that “doesn’t carry to nearby homes,” Meagher said.

Mike Booth, of Sevee & Maher Engineering of Cumberland Center, explained to the group about the design for the multi-layer landfill liner. The design has six cells, and each cell last for about 2 years, Booth said.

“We’ve come up with two different liner systems — one [regular] liner and one augmented,” the engineer said. “In the areas where we don’t have as much soil we’re going to augment the liner.”

The liner will have 12 inches of soil, an geocomposite net, a foot of special expandable clay, and geosynthetic layer that cover a leak monitoring layer, and a leachate collection system.

Unlike previous systems, “this system is seamless,” Booth said. “The liners are welded together.”

Because “leachate is a great conductor” detecting leaks will be done using a device that uses conductivity, Booth said.

“That is something that can be done monthly, weekly or daily,” he said of the testing. “We usually do it monthly.”

After Booth finished his presentation, two representatives from Sandborn Head, a technical consulting firm from Concord, New Hampshire, gave a presentation about collecting gases produced at the landfill, 40 percent of which are methane.

Resident Ed Spencer, who has opposed the expansion, asked if gasses would be monitored after the landfill is closed. He worried about methane explosions years down the road.

Cynthia Darling, who handles solid waste issues for the DEP for the Bangor region, answered, saying there is a 30-year monitoring program for closed landfills.

After the application is filed, the landfill expansion will undergo a lengthy DEP review before going to the federal government and city of Old Town for approval. Public meetings, hearings and a public comment period will be held.