New dock may be vulnerable to quakes

Posted: Sunday, November 26, 2000

WASILLA (AP) -- The new Matanuska-Susitna Borough port at Point MacKenzie may not be able to withstand an earthquake, according to a preliminary review by the Army Corps of Engineers.

The review, presented to borough officials in a teleconference last week, indicated that pilings protecting the 500-foot-long dock from tides could shake loose in an earthquake because of an unstable layer of silt underneath.

Borough officials say they're certain the dock will hold up.

''I'm confident there's not a problem,'' said port director Marc Van Dongen.

At issue is the stability of the several hundred 70-foot-long pilings that surround the dock. The pilings, driven into the Cook Inlet silt, hold 350,000 cubic yards of gravel in place.

Van Dongen said he's confident of the dock's stability in part because of how hard it was to drive the pilings. Some pilings were sheered off, and crews had to use a high-powered impact hammer to push others into the silty bed.

Only two of the three test holes drilled for the corps turned up a potentially weak layer, he said, and those two holes were 10 feet apart. So it could be just a localized problem, he said.

Two other holes drilled last year showed no signs of weakness in the soil, according to Van Dongen.

Still, the borough plans to drill more test holes to ensure the dock is stable, he said. He hoped to have that work completed by early December.

Corps officials reached in Mississippi would not comment on the review until it was final, which won't happen for at least a month.

State Department of Transportation officials originally requested the review because of concerns about the stability of the gravel dock and lack of data about the silt underlying it, Van Dongen said.

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