ANCHORAGE — Avalanche conditions remain too unstable to clear a highway into the Alaska city of Valdez, state transportation officials said Tuesday.
Two major avalanches and 10 or so smaller ones dumped snow Friday along 27 miles of the Richardson Highway, the only road access to the city at the end of the trans-Alaska pipeline.
One avalanche blocked a river and created a half-mile lake that covers the highway.
The pipeline buried in the area wasn’t affected. Likewise, city residents have been mostly unaffected unless they had plans to drive elsewhere in Alaska. Valdez is accessible by aircraft, ferry and barge and the city received a shipment of groceries in containers Monday.
The highway Tuesday remained closed from Mile 12 to Mile 42.
The Alaska Department of Transportation announced crews had begun removing snow from a major slide at Mile 39. Once debris is cleared from the area, the department said, crews will focus on smaller slides that may have affected single lanes of the highway in Thompson Pass, the 2,800-foot passageway through the Chugach Mountains.
The more serious problem remained at the site of the other major slide at Mile 12.
Tons of snow fell onto the highway in Keystone Canyon, a 300-foot-wide choke point where the highway runs parallel to the Lowe River. DOT spokeswoman Hannah Blankenship said snow 40 feet deep and 1,000 to 1,500 feet long covered the highway.
The avalanche dammed the Lowe River and backed up water, creating the half-mile long lake that’s 5 to 10 feet deep on the north end away from the blockage.
Water has been draining underneath the avalanche and through a nearby railroad tunnel.
“It’s dropping at the same rate as we estimated before, which is 5 inches per hour,” Blankenship said.
About 500 feet of roadway has been exposed since the lake formed. However, conditions remain too dangerous to clear the avalanche. The snow cannot be reached by heavy equipment on the water side and digging from the south side could collapse the snow dam and trigger a surge of water that put work crews in danger.
Highway officials plan to resume using explosives Wednesday to bring down loose snow in avalanche zones, Blankenship said.
The department uses both a 105mm howitzer and explosives in 50-pound bags dropped from helicopters to trigger controlled avalanches.