Grand County opts for $8 million landfill fix
GRANBY – In the latest attempt to stop the guts of the Grand County Landfill from sliding into Coyote Creek, Grand County commissioners have opted for a highly technical dewatering project.Commissioners reviewed engineering alternatives on Tuesday to address the landfill landslide that has plagued the county since 2007.After a $4 million investment in 2007 to create a large buttress that stabilized the slide, it was determined there are actually two sections of earth sliding as part of a greater landslide. In fixing the upper northeast portion of the active slide area, commissioners had thought they were stabilizing all of it at the time, said Commissioner James Newberry. The buttress worked; the upper portion has remained in place. But about 30 acres of the lower land mass, which includes solid waste, is inching toward Coyote Creek in a southwest direction as one unit atop a slippery layer of clay material and deep groundwater.The “toe” of the slide is about 56 feet from the creek, enough distance to deem the waterway not threatened at this time, said Grand County Manager Lurline Underbrink Curran. That gives county officials time to implement a solution. Last July, county officials learned the site was a strong candidate for a tieback system involving 500 permanent anchors used to stabilize the landslide. But after engineers “got into the nuts and bolts of it,” officials learned the system would actually require double the amount of tiebacks at an estimated price of $17 million. Since that number of tiebacks would push the envelope in technology for the size of the slide in question, the approach has been abandoned, according to county officials.At the county commissioner meeting on Feb. 21, a panel of engineers from KRW Consulting of Lakewood, Ground Engineering of Commerce City, Shannon & Wilson Inc. of Denver, and oversight engineer from the Colorado School of Mines, Dr. Paul Santi, presented to county commissioners a new set of alternatives to fix the landfill site, ranging from $8 million to $37.7 million.Relocating the landfill refuse to the Kremmling Landfill is the most expensive option.Commissioners instead settled on a dewatering option that would serve to possibly slow the landslide and stop a portion of the landslide mass within months of completion, according to engineers.The process would involve digging a series of 75- to 200-foot deep wells and pumping water from the slide plane, at a total cost of about $8 million. Engineers recommended the project be approached in incremental stages since the probability of success starts at 50 percent in the first phase of installing only a few wells above the active landslide. If that phase is deemed successful through close monitoring and modeling, phase two would kick in, which has an estimated 75 percent success rate and would entail drilling more wells. If that is successful, the project would progress to phase three, at a success rate of about 90 percent, during which wells would be located within the landslide active area where there is refuse.The county would invest $240,000 for the first phase, and if successful, enter phase two at a cost of about $400,000. If that succeeds, phase three would mean another investment of $7.3 million. The water extracted from the site, if tested safe, would be transferred to a Grand County-owned field away from the landfill to be returned as groundwater, Underbrink Curran said. If tested unsafe, it would be treated, she said. The county would first use $1 million it has set aside for landfill closure to pay for the first phase of the project, Underbrink Curran said. It’s expected the first phase could be completed in the first half of summer 2012, and the second phase in the second half of the summer, with the completion of the project by the end of 2013.If dewatering failsIf any of those phases are unsuccessful, a back-up solution has been identified at a cost of $14.7 million. The back-up solution, when completed, would look like three separate 5- to 6-foot high concrete walls anchored into the ground, like large retaining walls. The solution would involve massive amounts of concrete and steel. The walls would be anchored by 78- to 114-foot deep reinforced-concrete columns in the ground, using about 78 yards of concrete for each -about $4 million-worth. The technology used is similar to that used to anchor bridges in bays, according to Ken Haynes of Grand County Road and Bridge.It’s projected the “anchored cylinder pile wall” solution could be completed in a year. 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 continued landfill monitoring and remediation for a period of 30 years would begin as the landfill is restored to a natural state. If the dewatering plan is successful, pumping would continue at the site indefinitely, according to engineers. No matter what solution proves effective, maintenance of the site will start in 2012, costing the county about $100,000 for building an uphill berm in order to divert snowmelt and rainwater from a large crack in the slide, and attempts will be made to fill the crack. Also, grass seed will be spread above the refuse mass to deter weed growth.- Tonya Bina can be reached at 970-887-3334 ext. 19603
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