OURAY – Local resources on both sides of Red Mountain Pass have mobilized this week in a massive coordinated effort to reopen US 550. The windy, mountainous route connecting the communities of Silverton and Ouray has been closed since Monday, Jan. 13 due to a significant rockfall incident at mile marker 90, two miles south of Ouray. It is the longest closure of the highway in recent history.
The release point for the rockfall was 900 feet above the highway, in an area locally known as the Ruby Walls, where the highway cuts into sheer cliffs hundreds of feet high.
Rigging for Rescue, a Ouray-based company owned by Mike Gibbs, set up a series of hand lines over the weekend so that rockfall specialists from the Colorado Department of Transportation and Yenter Companies can safely reach the rockfall area on foot, rather than being delivered there by helicopter.
Workers from Silverton Mountain, an extreme ski area near Silverton, have also been enlisted by CDOT to help expedite the re-opening of US 550. Ski area owners Jen and Aaron Brill offered the services of their helicopter starting on Monday this week to deliver large pieces of wire mesh to stabilize huge piles of talus that remain perched on 40-degree slopes, hundreds of feet above the highway.
“There will be 46 nets placed on the site to hold the rocks in place, stabilizing the slope,” Silverton Mountain stated in a release earlier this week. Once the debris field is covered with the netting, Yenter can proceed more safely with the work of releasing boulders from the lower reaches of the talus slope.
Ski area blasting specialists will also be assisting in explosive work on the cliffs as part of the mitigation effort, according to the release.
CDOT geologist Bob Group was at the rockfall site all of last week. He described the episode as occurring in two stages. The main slide initiated from a near-vertical rock slope 900 feet above mile marker 90 that buried a 200-foot section of the highway with piles of rubble up to eight feet deep.
“In addition, a lot of material remained up on top of the more shallow part of the slope,” Group said. “That’s what gives us problems now, as it is slowly working its way down.”
Rockfall mitigation specialists with Yenter initially tried to access the target area with rock scalers to remove loose rock, but this effort proved unsafe as rubble continued to rain down from above.
“Plan B”, involving the installation of the wire mesh, is considered a short-term solution for the problem. “We are looking into potential long-term solution, involving a fence to catch material,” Group said. “But we will see how the mesh behaves.”
According to Group, rockfall is a common problem for CDOT throughout the state, “but this is significantly larger than most rockfall events in Colorado,” he said. “Most road closure events entail 10-15 cubic yards of rock. This is a couple orders of magnitude larger than what we typically see.”
Group estimated that between 5,000 and 10,000 cubic yards have come down so far.
The last large rock fall incident CDOT responded to happened on Highway 50 between Salida and Canon City. “It was a third the size [of the current incident on Red Mountain Pass] and the highway was closed for a week,” Group said.
The most challenging aspect of dealing with the rockslide on US 550 is that smaller pieces of material “keep raining down, and will cover a 200 foot section of the highway every day,” Group said.
The material is coming down slowly enough that the highway can be safely cleared at the end of every day, however, with the aid of spotters.
There is still no estimate for a reopening of US 550. Group said on Tuesday that it will take at least three days to install the wire mesh, after which Yenter Companies rockfall mitigation specialists will still have considerable hand scaling to do before the highway will be safe for travel.
Red Mountain Pass has been closed in both directions between Silverton and Ouray since the afternoon of Monday, Jan. 13, necessitating a roughly 200-mile detour over Dallas Divide and Lizard Head Pass for those who must travel between the two communities.
The actual closure points are at mile marker 92 just south of Ouray, and at mile marker 87 at Ironton Park, about 17 miles north of Silverton.
Silverton Postmaster Becky Rhoades said that the mail is still getting delivered to town via the alternate route. “It’s just getting here late,” she said, adding that local Silvertonians are coping quite well with the road closure. “When you live in a place like this, you’d better be prepared for things like this to happen,” she said.
In addition to shutting down the highway, the rockfall event also took out a historic power line belonging to San Miguel Power Association that dates back to the 1920s, and provides a backup power supply to the Ouray and Ridgway region.
SMPA crews spent last Wednesday removing the damaged infrastructure. SMPA Operations Superintendent Paul Enstrom reported that two large structures were damaged by the slide. One structure lost its crossarm and another was completely wiped out.
According to SMPA spokeswoman Becky Mashburn, repairs will not be made to the line until spring. “It will involve helicopter work,” she said. “We can’t just pull up a bucket truck to the site. It involves scrambling and hiking on sheer cliffs.”
Until repairs are conducted, Ouray and Ridgway will continue to be supplied with power via the main power line, with no backup supply. This could leave the area vulnerable to longer power outages if something happens to the main line.
“We are now in a holding pattern discussing our options,” Mashburn said.
ALTERNATE ROUTE: From Ouray to Durango (a distance of 70 miles using US 550) motorists will instead use SH 62 from Ridgway over Dallas Divide, SH 145 over Lizard Head Pass, then US 160, for a trip of about 154 miles.
For information on other CDOT projects, call 511 or log onto CDOT’s traveler information web site at www.cotrip.org. Sign up to receive email and/or text messages by going to CDOT’s web site atwww.coloradodot.info and choosing the green phone icon in the upper right corner.
email@example.com or Tweet @iamsamwright