State plans to reduce rockfall hazards along highway

The state Transportation Department is asking for public comments on its plan to reduce the hazards along a stretch of Wrangell's Zimovia Highway frequently hit by rocks coming down from the hillside.

A rockfall last August at 8-mile Zimovia Highway "drew our attention" to the stretch of roadway, state Transportation Department officials said last week. Talking with the department's Wrangell crew, they learned there had been 36 rockfalls between 2007 and 2019 along just a few miles of the highway.

The department wants to get ahead of the problem with preventative work next year to take down some rock, said Nathan Purves, highway safety improvement manager for the region, and Tyler Riberio, an environmental impact analyst.

No one has been injured in any of the rockfalls, they said.

The department has identified three specific areas for the rock work between 5.5-mile and 8.5-mile, "to reduce the frequency and severity of rockfalls," the department's public notice said.

Work could start August 2022 and finish by the end of summer, Purves and Riberio said.

The total cost for the project analysis, engineering, design and actual site work is about $930,000, they said, of which federal funds would cover 90%.

The plan is to seek bids and issue a work contract for a set amount, accompanied by a list in priority order, with the contractor getting as far down the work list as funds will allow, the officials said.

Plans include breaking off lose rocks from the hillside, using either pry bars or maybe inflatable air bags that would be wedged into tight spaces and expanded to dislodge loose rock, Purves and Riberio explained. No blasting is planned, for fear it would further destabilize the rock slope, they said.

Rock bolting is part of the plan, too - literally bolting rocks together, to hold them in place.

Vegetation clearing also is part of the work list. The roots of trees and shrubs can open up crevices, allowing water to seep into the rock and, after freezing and expanding, loosening and breaking apart the rock above the highway. Besides, a falling tree from the slope can cause as much damage as falling rocks, they said.

All of the work is planned within the state right of way. Rocks knocked down from the hillside will be hauled to the Transportation Department yard and stockpiled for use later.

Public comments on the work plan are due to Riberio by April 25 at tyler.riberio@alaska.gov, or by fax 907-465-4414.