WALLA WALLA - On Wednesday, City Council members will again discuss whether they should award a $1.5 million contract to Boss Construction Inc. or consider that company's bid as insufficient and pay $100,000 more for the next highest bidder.
But even at $1.6 million, the cost of closure is still millions of dollars less that what City Utility Engineer Frank Nicholson was expecting to meet Washington State Department of Ecology requirements.
"Originally the engineers came in and said you are going to have to put a plastic lining on it at around $4 million," Nicholson said.
The "it" that Nicholson refers to is a 20-acre mountain of Walla Walla's trash, the highest point at Sudbury Landfill. And directly under the peak of Area Six is 100 feet of compacted refuse with a cap of two feet of top soil.
"We said that's crazy. We can't afford $4 million. And we talked to Ecology and they said we are approving you for a brand new process," Nicholson said.
The original plan for Area Six was to cover the mountain of refuse with a plastic liner to keep rain and snow runoff from leaching through the contaminated refuse and into the water table. But a relatively new process to Washington state will replace the need for a liner by utilizing the natural process of evapotranspiration - the evaporation of ground water from soil and plants up into the atmosphere rather than down into the ground.
According to Nicholson, the upper few feet of soil in the region's arid climate acts like a sponge; precipitation is absorbed only a few feet down into the loess and over the drier months is evaporated into the atmosphere without ever seeping to the water table.
"If you talk to the wheat farmers, and I have talked to a couple of them, if you dig down about five feet the soil is actually dry, and that is what you find over at the landfill," Nicholson said.
The plan now is to forgo the liner and add three additional feet of top soil to the current two feet. To help save money, the landfill crews will use dirt from trench excavation work on Landfill Area Seven.
"It is a win-win situation because we are going to have to move out that soil to finish building the existing pit (of Area Seven)," Nicholson said.
The majority of the roughly $1.5 million for the project will be used to build up the topsoil on Area Six to a minimum of five feet. But about a third of the cost will go toward remediation of harmful gases, work that could take decades to complete.
Landfills tend to be a source of methane because as refuse decomposes gases are released. The Department of Ecology now requires landfill operators to drill wells in closed landfills to collect methane and burn it. The wells are made of PVC pipes that is perforated toward the lower end and kept at negative pressure, thus allowing methane to be sucked from the soil.
Though this process could take a decade, it could also one day be a long-term source of energy and income.
Nicholson said once the methane wells are in place, the city will look at ways to use the gases to generate energy and income, and the city will also receive carbon credits for the methane it burns, which it can also sell for income.
"Methane causes 20 times the greenhouse effect of just carbon dioxide ... and we would love to turn that gas to energy," Nicholson said.
As for the cost of the Area Six closure project, ratepayers are already paying for it and have been since the first of the year.
This year's annual rate increase saw a 15 percent hike in tonnage fees due to inflation, less tonnage being collected, meeting the requirements of unfunded mandates, the ongoing environmental remediation of the prior Sudbury Landfill Area Five and the projected costs of the Area Six closure project, according to city documents.
The end result of all those factors was that on Jan. 1, residential and commercial curbside collection rates went up 11 percent.
The Area Six closure project is expected to begin this summer and is expected to take about three months to complete.
Once the project is finished, Nicholson noted it will take generations for the land to ever be used again, due in part to the slow deterioration rate of the area's low-moisture soil.
"It will probably be a couple hundred years ... maybe they will mine it. But it will be held in the public interest," Nicholson said.