Work on Owl Creek Road stops the slip toward the Sinclair Divide
Road maintenance to install underground support system wraps this week
If you’ve ever traveled on the paved Owl Creek Trail heading toward Aspen from the Tom Blake Trailhead, you know that the hillside between the path and the road above is steep.
A little too steep, it turns out. The soil that the road was built on has been shifting, slipping and ever-so-slightly sloughing toward the Sinclair Divide, causing a dip in the road above that would have kept on dipping were it not for the subterranean work that has reduced the two-lane road to one lane for most of the past month, according to Pitkin County engineer G. R. Fielding.
The work had mostly wrapped up Oct. 26, with a few more days ahead for crews to clear out before it’s back to business as usual on the section of roadway located just outside of Snowmass Village town limits. Road work began around the last week of September, with Harrison Western as the contractor and SGM Engineering taking the lead on design beforehand.
Overall, “it’s gone really smooth,” Fielding said, albeit with some minor hitches to be expected from a project that deals with natural materials that haven’t seen the light of day.
“We had a couple of hiccups — any time you open up the ground to see what you’re going to see, it gets a little bit harder because there’s a little less planning that you can do,” Fielding said.
Still, the project will finish on time and on budget, according to Fielding.
Once the site is cleaned up — Fielding expects that to take place over the next few days — passerby won’t be able to see what it is that’s keeping that section of Owl Creek Road from slowly dipping toward the Sinclair Divide.
The work is all underground, where a battered micropile wall now helps hold the soil in place and keep it from sliding, then backfilling, then sliding and backfilling again.
Crews dug 25-foot-deep holes, half of them vertical and half at a 20-degree angle, and then filled half of them with steel pipes and grout and the other half with rebar and grout. The goal there was “cohesion” deep into the soil. To decide just how deep the holes should go during the design process, a geotechnical engineer put an inclinometer in the road to measure how and where the land was moving.
Once the holes and steel were in their places, all of the micropiles got connected on top with a concrete beam. The whole thing is now buried underground, and it’s unlikely to budge much.
“The whole idea is that, you know, if you get a little bit of movement here or there, it’s all connected now, and it won’t move back,” Fielding said.
It works a bit like wood skewers keeping the middle of a lofty layer cake from slipping out between all the frosting, or several toothpicks holding together a stacked club sandwich, but it’s far more permanent, stable and, well, drilled 25 feet into the ground under a roadway. (Grout is not a recommended condiment for most lunches, either.)
The county has been making minor fixes to that spot in the road for at least as long as Fielding has been working for the county — almost 15 years, he said.
But the new micropile wall will last a whole lot longer and ideally keep that site stable for decades to come without the need to keep propping it up with shorter-term fixes.
“We’re hoping that no one’s going to have to touch this exact location for, you know, 70, 80 years down the road,” Fielding said.
The key word there is “exact location.” Though this particular spot is now long-term stable, that doesn’t mean there aren’t other parts of the hillside road that won’t see the same.
“There’s always a caveat to that. … With as steep as the topography is around here everything is always moving more than you would like if you’re a civil engineer that is responsible for roads,” he added. “And so I can’t say that another part of Sinclair Divide won’t need to be fixed at some point in time, because there’s a lot of steep slopes right there, but … this should be a — hopefully — a one-and-done deal.”
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