Grand County aims to save ailing landfill cover
April 30, 2015
Grand County officials hope that adding dirt to the Granby Landfill can temporarily save a cover installed last year to slow a landslide at the site.
The cover was installed with the hope that it would prevent runoff from entering the slide area and exacerbating the slide, but settling beneath the cover has caused it to sink, thus allowing water to pool on top rather than run off.
Additionally, the continued movement of the landslide caused one of the cover's seams to drip.
"It's pretty apparent to me that if we let this thing sit and don't put anything underneath it, and particularly if we let it go through the winter, we're going to end up with a ruined membrane next year," Tim Gagnon, grand county engineer, said during a Tuesday, April 28, workshop on the subject
The cover cost around $150,000, and the dirt put underneath it around $350,000.
Filling it with dirt this year would cost around $150,000, Gagnon said.
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Officials discussed a number of options to fill the space below the cover, with ideas ranging from adding woodchips, foam blocks or spray foam to giant airbags.
Woodchips weren't realistic because they could puncture the membrane among other issues, Gagnon said.
Using foam blocks would cost approximately $500,000 per year, with yearly additions necessary as the space continued to fill, with spray foam being even more expensive.
Gagnon said he preferred the airbag option.
The giant spheres could be gradually filled to accommodate settling beneath the cover, extending their life to three or four years. That project would require around 200 bags and would cost around $350,000, though Gagnon said he wasn't sure whether it would work.
Some expressed concern that filling the space would be a temporary fix and wouldn't address the continued movement of the landslide.
The section of earth currently breaking away has moved around half a foot in April 2015 alone, Gagnon said. He added that that could be due to normal spring movement coming earlier this year.
But Commissioner Merritt Linke said the cover was originally meant to slow the movement, and setbacks mean it hadn't really been given the chance to prove itself.
"The truth is we haven't actually tested this design to its fullest extent," Linke said.
Commissioners seemed to agree that adding dirt would be the best temporary fix to rebuild the crown beneath the tarp, asking that additional options be explored further.
Landslide still moving
If the membrane fails to slow movement of the landslide, the county has few options to keep the landfill compliant with Colorado Department of Public Health and Environment.
Possibilities discussed Tuesday included installing a previously discussed cylinder pile wall and relocating all of the trash.
Previous quotes for the cylinder pile wall, which would entail installing large reinforced concrete retainer walls, were around $14 million, though Gagnon said that, with the additional movement, the project could cost around $20 million.
Considering the cost, time for completion and probability of success, Gagnon said the cylinder pile wall was the most appealing option for completely stopping the movement.
Moving the trash to another location would be an even more monumental project, with a timeframe of up to 11 years and a possible cost of $60 million, said Ken Haynes with Grand County Road and Bridge.
Commissioner Kris Manguso pointed out that movement might stop before all of the trash is removed, lowering the cost.
The board of commissioners asked for more information on the cost of moving the trash as well as the option of adding airbags below the cover.
The county has spent approximately $7 million on the landfill since 2007.