Grand County could spend $6.6 million to halt sliding landfill
Grand County, CO Colorado
Grand County commissioners voted unanimously to spend roughly $6.6 million on a tie-back system to stop the ground from moving at the Granby Landfill, which has been out of commission since April 2010.
The decision was made after extensive analysis of seven possible solutions presented to county officials by engineers from KRW Consulting of Lakewood, Ground Engineering of Commerce City and oversight engineers from the Colorado School of Mines.
The tie-back system, deemed likely to be the most economical and successful approach, effectively locks land in place, allowing it to settle over time.
The system involves installing 500 permanent ground anchors used to stabilize the moving hillside. At the surface are three rows of 10-foot by 10-foot concrete bearing pads, each attached to a steel cable that is drilled 90 to 100 feet into the ground past the slip plane and anchored to intact material such as bedrock.
Although the three rows of bearing pads initially would be exposed, spanning the hillside about 75 feet above Coyote Creek at the old landfill site, they ultimately could be buried and the slope re-seeded to hide them from view, engineers said.
According to engineers, the tie back system does not “push the limits of technology” in spite of the 40 acres of ground that needs to be stopped from sliding.
Such a system is “fairly common throughout Colorado,” said Colorado School of Mines engineer Mike Mooney.
The Granby Landfill landslide was first addressed in 2007 with a $4 million engineered berm to stop the uphill mass of the slide. That upper portion has since remained sound, according to county officials, but a lower land mass, which includes landfill waste, is sliding as one large unit atop a slippery layer of clay material and water deep underground.
The slide has been moving at a rate of about 1 foot per month, and this spring, the slide reached a record rate of 1.5 feet per month.
County officials were assured water beneath what is hoped to be a secured land mass once the project is completed would continue to flow naturally without interruption.
The Granby Landfill has been closed to the public, but the problem of the landslide must be solved in order to gain state approval for closure of the site, at which point begins landfill monitoring and remediation for a period of 30 years as the landfill is restored to a natural state.
The next step for the county will be to seek bids and financing for the project, according to County Manager Lurline Underbrink Curran. County officials hope to seek bids as early as this fall, with construction slated for next summer.
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