The concrete structure channels snow over US Highway 550 from one of the most active avalanche paths on on the Million Dollar Highway. The Riverside Slide is responsible for all of the avalanche-related fatalities near Red Mountain Pass.
The Riverside Slide plays an important role in Red Mountain Pass. Built to channel avalanches over the highway, the tunnel also has an emergency phone installed. According to the Durango Herald, the highway was closed in 2019 due to a particulrly large avalanche.
From the Herald: "Red Mountain Pass was closed for 19 days in March after heavy snow blanketed the highway in 3 to 4 feet of snow and triggered numerous avalanches that crossed the road.
U.S. Highway 550 between Silverton and Ouray closed shortly before midnight March 3 and reopened March 22. The Colorado Department of Transportation flew the length of the pass, which is part of the San Juan Skyway (scenic byway), on March 15, capturing this video.
Avalanches covered the road in 10 to 30 feet of snow in numerous locations, and the snow was 60 feet deep near the West Riverside slide path on the north side of the pass...
Two crews with four or five people on each crew worked 12-hour shifts on each side of the pass.“It was surreal,” said Lisa Schwantes, CDOT spokeswoman who took the video. “Truly, truly bigger than life. For someone who is familiar with Red Mountain Pass and having driven that many, many times in my lifetime, I was very familiar with some of the twists and turns, but it was just amazing to see the massive amount of snow that was on the pass and the roadway.”