Ministry monitoring highways after recent rock slide

Highway 22A and Seven Mile Dam Road are open after an overnight rockslide temporarily closed both roadways on Friday.

Highway 22A and Seven Mile Dam Road are open after an overnight rockslide temporarily closed both roadways on Friday.

The highway to the U.S. border was opened at 11 a.m. on Friday after two large boulders were taken away in pieces. Seven Mile Dam Road was opened the next day, Saturday, by 4 p.m.

The Ministry of Transportation and Infrastructure is looking at ways to prevent another road closure.  After the slide, the ministry sent out a geotechnical engineer to assess the site.

“Based on our site investigation and the low level of risk to the traveling public, we feel the best way to keep the public safe is to ensure we have a clean, deep ditch adjacent to Seven Mile Dam Road,” said Robert Adam, government communications and public relations for the Ministry of Transportation and Infrastructure.

Some areas, like Paulson, have nets and cables on the rock face to prevent slides, but Adam says that all sites are different. The nets may not be an option for the Lower Columbia region.

“Generally speaking, the ministry process to deal with roads passing through hazard areas is to assess the site for any immediate safety concerns, implement any site-specific improvements and/or repairs to restore the site, then post the site with the appropriate, permanent warning signage.”

Adam says it was a combination of warm and wet weather, with a bit of frost, that may have caused the rocks and boulders to lose their grip on the rock face.

“The rock fall was likely caused by a combination of the wet weather and the freeze/thaw cycles at the upper elevations,” he said. “The mild, wet weather is causing water to seep into any available joint or fracture within all exposed rock faces. The natural freeze/thaw cycle of the air temperatures, combined with frost moving up, out of the ground, is causing the water in the rock joints to expand and contract, which in turn, can make some rocks unstable.”

Seeing large rocks on the highway is something that is usually reserved for thawing season in the spring, Adam says it is not unusual to see a slide in the fall.

He says that drivers should take note of any signage warning of a potential rockslide area and drive according to the road conditions to avoid injuries and collisions.