A massive excavation project will take place this summer at the Flathead County landfill.

Bids are due Tuesday for the first phase of the multimillion-dollar project, which involves digging a six-acre hole in the ground and removing about 400,000 cubic yards of dirt, or roughly 40,000 dump-truck loads.

The hole will be located on the northwest side of the existing garbage hill.

Landfill Director Dave Prunty said the job will be completed next summer, when the hole is covered with a multi-layered plastic liner designed to contain any potential contaminants and protect groundwater resources.

"We're extending the bathtub," Prunty said. "The old days of digging a hole and throwing in the garbage are over. This is what it takes to function under today's rules."

The landfill currently has about nine acres of liner in place, he said. This latest project will extend that by another six acres.

There's room for one more 8- to 10-acre extension after that; then the existing hill will be full and garbage dumping will shift to a new, 30-acre site immediately to the south.

The two "bathtub extensions" should give the landfill another 10 to 20 years of capacity, depending on how fast the valley grows, Prunty said.

Last year, more than 111,000 tons of garbage were received - up 15.7 percent from 2003.

"That's phenomenal. Two percent is a normal growth number," he said. "And we're on track to hit at least 111,000 this year, so 2004 wasn't just a big blip."

To stay ahead of demand, the landfill is seeking a license from the Montana Department of Environmental Quality for the expansion area.

If approved, the project will give the landfill another 50 to 75 years of capacity. Prunty expects a public hearing to be held on that proposal sometime this fall.

Reporter Bill Spence may be reached at 758-4459 or by e-mail at bspence@dailyinterlake.com