Contractor scientists for the U.S. Department of Energy Office of Legacy Management (LM) traveled to the Amchitka, Alaska, Site in late August to assess the damage caused by a recent earthquake. The 7.9 magnitude event occurred approximately 20 miles north of the island on June 23, 2014. Amchitka Island, near the western end of the Aleutian Islands, is approximately 1,300 miles southwest of Anchorage, Alaska.

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Amchitka mud pit cap sites.
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Before 2014 earthquake—
the Rifle Range Site (June 2011).
After 2014 earthquake—a crack in an access
road at the Rifle Range Site is identified
(August 2014).

The scientists were joined by personnel from the U.S. Fish and Wildlife Service (FWS) and the U.S. Geological Survey (USGS). Two USGS scientists traveled to Amchitka to upgrade the seismic monitoring equipment and to monitor existing geodetic survey stations across the island.

Three underground nuclear tests were conducted on Amchitka Island between 1965 and 1971. The FWS scientist assisted the LM contractors on their inspection of seven test-associated areas on the island where drill cuttings contaminated with diesel fuel are contained in earthen disposal cells. These areas are known as the mud pit cap sites.

Of the seven mud pit caps inspected, two showed no signs of damage, two had minor cracks along the edge of the mud pit caps, and three had moderate damage. Moderate damage occurred on one of the mud pit caps where the soil cover had slumped away from its side, exposing the geomembrane fabric that covers the drilling mud. Another cap with moderate damage had a prominent crack along its uphill side, and the land surface down-slope of the cap had slumped away. The mud pit cap was still intact; however, native soils up-slope and down-slope of the site have either cracked or slumped.

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Left: Before 2014 earthquake—the Long Shot Site (June 2011).
Right: After 2014 earthquake—a crack along the northeast side of cap at the Long Shot Site
is documented (August 2014).

“Although there was shaking-induced ground failure at the surface, primarily in areas with soft, wet sediments and fill, [we] don’t suspect any damage occurred in the test cavities,” said Mark Kautsky, LM site manager. “The test cavities are in dense rock, several thousand meters below the surface and the earthquake occurred at a depth of 70 miles below the surface, so it is unlikely there was any damage to the underground test cavities; however, we will continue monitoring the region very closely.”

LM is currently assessing the best way to repair the damage that occurred to the mud pit caps and is scheduled to conduct biological monitoring of the Amchitka site in 2016.