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State unveils plan for shoring up bluff to protect highway

Posted: November 1, 2012 - 10:22am

This aerial photo shows how erosion is threatening the Sterling Highway at Mile 153.3. 
Public comments are requested on a plan being developed by the Alaska Department of Transporation and Public Facilities to address the problem.  Photo provided
Photo provided
This aerial photo shows how erosion is threatening the Sterling Highway at Mile 153.3. Public comments are requested on a plan being developed by the Alaska Department of Transporation and Public Facilities to address the problem.

How important is the Sterling Highway to the southern Kenai Peninsula? To answer, area residents have only to recall the

 flood of 2002.

Traffic came to a sudden halt when heavy rain and flooding destroyed bridges across Stariski and Deep creeks and caused other areas of the highway to become impassable. Groceries flown in by Northern Air Cargo’s DC-6 quickly disappeared from shelves. Worried shoppers hurried to buy the basics, causing grocery store owners to institute a two-gallons-of-milk-per-customer limit. People stranded by the rising water called for help. Helicopters were summoned for medical emergencies.

Now, erosion at mile 153.3 is threatening the Sterling Highway. The narrowing distance between the highway and the bluff hints at what is going on below. Aerial photos displayed at the Alaska Department of Transportation and Public Facilities’ open house last week reawakened a sense of vulnerability and dependence on the highway.

“What happens if that highway gets compromised?” asked Monte Davis, executive director of the Homer Chamber of Commerce and Visitor Center. “It would be bad enough if it happened during the winter, but we are Alaskans and we could hunker down and probably be just fine. But if it happened during the summer, I don’t even know how to put a figure on it.”

Davis was among those at the open house as Gerry Welsh, DOT project manager, and other DOT representatives, explained an erosion response project on which the department is seeking public comments. 

Erosion, happening at an average rate of
1.1 feet per year, is caused by the gradual movement of sandy material saturated by the groundwater. A conceptual design for repair has been developed, but the formal design process has yet to begin.

The project seeks to preserve highway safety and sustainability by:

• Excavating saturated material form the bottom of the erosion feature;

• Constructing a riprap layer to stabilize the slop and provide a course for groundwater flow; and

• Placement of topsoil and revegetation. 

“The distance between the bluff and the highway is somewhere between 45-50 feet,” said Welsh the current margin of safety.

Funded with federal dollars, the project is in its environmental phase, “identifying which permits are necessary and what impacts there would be to the environment,” said Welsh. Once that is complete, the next step is to obtain authorization from the federal government to enter the design phase. Also to be addressed is authorization to acquire any property rights needed to do the work.

“The design phase concludes with a plan which we use to go out to bid to contractors,” said Welsh.

The bids are evaluated and “at that point the work will commence depending upon the schedule determined in the design phase,” said Welsh.

Welsh is confident the project can be completed during 2013. He does not believe the work will require closure of the Sterling Highway.

“We are not affecting any changes to the highway, just stabilizing the slope adjacent to the highway,” said Welsh. “It’s a spot repair.”

Very familiar with the area, local geologist Ed Berg said in addition to erosion, there also is the possibility of “liquefaction” at the site in the event of an earthquake.
“You have this water-saturated sand layer sitting on top of an impermeable concrete-like glacial till. An earthquake lifts up the ground and would take the pressure off the sand grains so they are essentially floating in water,” said Berg. “Something like that would take out hundreds of yards of the bluff. There really isn’t much you can do about that.”  
Berg pointed to examples of such massive slumps along the bluff between Diamond Creek and Anchor Point, some of them occurring within the last several decades.
“Most of them have either a coal layer at the bottom or a glacial till layer and then sand overhead and wetlands providing a steady supply of groundwater. It’s very well set up for liquefaction,” said Berg.

Davis said he is “very excited” about the state’s plan to address the erosion.

“I’ve queried them and they’ve done things like this in other parts of the state and its worked relatively well, it’s inexpensive, but more importantly, it’s quick. So, I’m thrilled,” said Davis. “We’ve chosen to live at the end of the road, but we’re still on the road and vulnerable to that. It’s one of our lifelines. No question about it.”

Derotha Ferraro, spokesperson for South Peninsula Hospital, noted multiple ways the Sterling Highway serves the wellbeing of area residents. For one thing, numerous employees live north of Anchor Point, Stariski, Happy Valley and Ninilchik. The highway also allows daily delivery of food, medical supplies, equipment and office supplies.

“Without the road, we would be forced to consider other, more expensive or time-consuming methods of receiving our goods,” said Ferraro. 

In addition, the hospital’s service area extends beyond mile 153.3.

“An estimated 1,500 residents reside between north of Anchor Point and Ninilchik,” said Ferraro. “They contribute to the hospital through their property taxes and they rely on the highway to have easy, direct access to the hospital.”

For additional information on the state’s erosion response for mile 153.3, contact Welsh at (907) 269-0500 or Matt Dietrick, environmental impact an analyst, at (907) 269-0531. Written comments on the Sterling Highway Erosion Response Project No. 52472/NH-0211(55) are to be provided by Nov. 19 to Brian Elliott, Regional Environmental Manager, DOT&PF Preliminary Design and Environmental, P.O. Box 196900, Anchorage, AK 99519-6900.

McKibben Jackinsky can be reached at mckibben.jackinskyA@Homernews.com.

 

 

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