DOT&PF works to solve Sterling Highway erosion problem

Construction at Milepost 153.3 slated for spring
The edge of the bluff encroaches on the Sterling Highway at Milepost 153.3. The edge is within 50 feet of the highway. Photo provided by the Alaska Department of Transportation and Public Facilities

The Sterling Highway, which serves as the Southern Kenai Peninsula’s road connection to the rest of the state, is inching closer to the edge of the bluff as soil falls away at a rate of about 1 foot annually.

While Alaska Department of Transportation and Public Facilities spokesperson Jill Reese said the erosion at Milepost 153.3, between Happy Valley and Anchor Point, doesn’t pose as an immediate threat, DOT&PF plans to begin construction as early as spring 2014 keep the highway out of jeopardy.

“Erosion can go as slow or as fast as water erodes (land) away, so there’s no real timeline,” Reese said. “That’s why (DOT&PF is) getting on it now is because (it wants) to go ahead and make sure it doesn’t get any closer to the highway.”

Reese said there’s about 50 feet of land between the highway and the edge of the bluff at the narrowest point. The land between the road and the edge of the bluff widens in both directions from that point creating a crater-like sloped semicircle.

“It’s quite an impressive hole,” Reese said.

DOT&PF became aware of the erosion issue about four years ago and initiated the Sterling Highway Erosion Response Milepost 150 – 157 project to stop the hole at Milepost 153.3 from becoming even more “impressive.” The agency is in the process of purchasing the privately owned property between the highway and the bluff, Reese said.

After DOT&PF owns the property, likely by early December, Reese said, DOT&PF expects estimates and project specifications to be complete by January or February 2014. The project will then go out for bid, and Reese said DOT should have a contract in place by March or April 2014. Then construction will begin, she said.

The construction process has five steps:

■ Removing trees and other vegetation form the eroding area,

■ Removing soil near the base to 8 feet below the original surface,

■ Laying riprap or large rocks to allow for drainage,

■ Constructing an embankment to stabilize the slope,

■ Planting vegetation to ensure stability.

“(DOT&PF is) hoping that that’s going to work,” Reese said.

The price tag of the project, which includes the purchase of land, comes in at $4.8 million, Reese said.

“So it’s an expensive little job,” Reese said.

Reese said the erosion is caused by a combination of sandy soil and groundwater running under the highway down the bluff and washing away the sandy soil.

Reese said DOT&PF did consider other options to alleviate the erosion issue.

“(DOT&PF) did consider moving the highway further, but that’s just sort of chasing your tail, (DOT&PF needs) to fix the problem.”

Kaylee Osowski can be reached at kaylee.osowski@peninsulaclarion.com.

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