State keeping close eye on Sterling Highway erosion

Posted: Friday, January 14, 2011

There's a spectacular view of Cook Inlet and the mountains to the west near Mile 153 of the Sterling Highway, between Happy Valley and Anchor Point. If the bluff gets much closer, there also will be an excellent view of the beach, hundreds of feet below.

"There's a slow, fairly steady migration toward the road," Carl High, Kenai Peninsula superintendent for the Alaska Department of Transportation and Public Facilities, said of erosion in that area. "We've been watching it for the last couple of years."

Information currently being gathered at that site by department personnel will be used to assess the stability of the 56-foot strip of land between the edge of the pavement and the bluff, and decide whether the bluff can be stabilized or a new route for the highway is needed.

At the current rate of erosion, a 10-15 year buffer exists before the highway would be threatened, according to DOTPF Planner Rick Feller of Anchorage.

"Of course, we don't count on that rate being consistent. There could be a mass wasting event, a sudden loss by erosion of the bank that could push us into a quick reaction and an ultimate fix," said Feller. "But as it stands right now, it looks like the historical rate of erosion is more or less continuing through the years."

The lack of certainty concerning the erosion rate is the driving force behind the current geotechnical profiling, which involves drilling holes to find out what conditions exist underneath the bank where erosion is occurring.

"Our geotechnical information might come back and say soil conditions are adequate or supportive of a bank stabilization effort that could leave everything in place, stabilize the bank and protect it from further erosion, or it could come back and say there's no way to stabilize it and we really should be looking more at relocating the road," said Feller.

"In between there are variables and that's what we're trying to figure out now with what we have to work with."

Crews from the Ninilchik DOTPF station do monthly measurements to track coastal erosion and the impacts of a spring that has developed in the bluff. That and the information now being gathered will help department personnel assess the situation and develop a plan for the future.

"We've started some preliminary planning in case we do have to move (the highway), but it's all very preliminary at this point until we get this assessment," said High.

The department's budget includes $200,000 for reconnaissance work currently being undertaken, with $1.5 million budgeted in 2012 for preliminary designs to battle erosion of the highway system including this area at Mile 153.

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