A Second Foundation Review of Ahtna Corporation Glennallen Facility, Alaska, USA

In the spring of 1975 a geotechnical investigation was accomplished at the proposed building site and included six test holes drilled to a depth of 10.7 meters into warm permafrost. Ground temperature measurements were taken in January 1976 at each test hole. Based on this investigation the decision was made to support the elevated structure on modified H-piles driven to a depth of 9.1 meters. Details of the installation of the foundation piles and a subsequent limited monitoring effort are presented in a prior 2004 technical report by the authors. The primary interest in monitoring the foundation ground temperatures has been to again observe temperature change below the relatively undisturbed ground surface. On July 23, 2020, some 45 years later, the authors had the opportunity to again revisit the site and obtain current ground temperatures at limited accessible pile locations. Although some ground cooling was observed in 2004, it appears that (while still frozen) some slight warming is now occurring. Ideally, evaluation of conditions should be made in the fall in order to better assess full summer warming impacts. Unfortunately, access to most pile locations was limited by “hoar frost” accumulation or other obstructions in the pile angle openings that equipment was not available to allow us to penetrate. Also, the observed past desiccation of the undisturbed thin surface organic mat must have had some influence on reducing ground warming at this site. An assessment of long ago design concerns, as related to current climate warming impacts, are also reviewed.