Grand County moves to alleviate Trough Road movement, settling
Grand County officials hope to a new drainage system can alleviate settling and movement on a landslide area on the Trough Road.
The section of road, approximately 3.5 miles from the State Highway 9 intersection, sits atop a hill saturated with groundwater, which causes the hill to move and the roadbed to constantly settle.
Road and Bridge Superintendent Ken Haynes said the county hopes a horizontal directional drilling project on the toe of the downhill slope of the road can drain some of that groundwater, mitigating the settling and obviating the Sisyphean task of filling the settled area with gravel year after year.
The estimated cost of the project is $50,000.
During a public hearing on the issue on Tuesday, April 28, the Grand County Board of Commissioners discussed a couple of options for addressing the settling, including a more expensive underdrain trench system suggested by County Engineer Tim Gagnon.
The horizontal directional drilling option would see a palmetto-shaped system of pipes with a common drainage installed at the toe of the hill.
The same technique has been used with success along I-70 near Vail, Haynes said.
Gagnon added that the trenching option had a higher probability of removing the water from the hill, though the cost, approximately $90,000, was much higher than drilling into the hillside.
“If either of these keep that groundwater no more than six feet from the surface, I think we’re going to really lower the amount of movement we see,” Gagnon said. “I think we will see a difference, and I think it will be fairly quickly.”
County Manager Lurline Underbrink Curran expressed reservations about installing an underdrain trench because it would require cutting into the toe of the water-filled hill.
Doing so could trigger a landslide.
In the past, the county has settled for filling in the settled area with gravel, Haynes said.
During one two-year period, the county spent around $60,000 on 200 loads of gravel to fill the area, he said.
At the Tuesday hearing, officials drew comparisons to the Granby Landfill landslide, which has continued to creep despite efforts to halt its movement.
The difference between the two is that there is a clear correlation between high ground water levels and movement at the Trough Road site, Gagnon said.
Ultimately, commissioners elected to pursue the drilling option.
“We can suck all of the water out of it, but I don’t think it’s going to stop the first year,” said Commissioner Merrit Linke. “I think it’s a process, and maybe it would never stop completely, but if we can get it down to where it’s fractions of inches that’s probably our success.”
The county will contract with Oregon-based Jensen Drilling Company and expects to complete the project this fall, Haynes said.
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The Colorado Department of Transportation has closed Colorado Highway 125 in Grand County while crews work to clear the route of mud, debris and snagged trees piled up on various bridges and guardrails.