Earthen dam failures of high hazard dams are expected to cause downstream human life loss and economic and environment loss. Of the three most prevalent failure modes for earthen dams, seepage (or piping) failures account for approximately 40 percent. All earthen dams seep and it is not uncommon to observe some seepage on the downstream toe, but the flow rate of uncontrolled seepage should be negligible. In general, seepage occurs through the dam and/or its foundation. The cross section of the dam is designed to force the waterside head (pressure) to drop as the water flows through the cross section to the downstream toe. Uncontrolled or unexpected seepage can promote soil movement (i.e. piping) and cause a pipe or a cavity to develop within the earthen structure which can lead to a complete failure of the embankment. At present there are over 84,000 earthen dams throughout the United States many of which depend on the US Army Corps of Engineers for inspection, monitoring, maintenance, and repair. Recently a multi-method geophysical investigation, was performed at a site where a suspected seep outflow had increased ten-fold, warranting further investigation. Because the seep presented in a historically dry stream channel in the karst bedrock adjacent to the dam abutment there was some question as to whether the origin of the seep was indeed a result of piping or due to a naturally occurring seasonal spring. Electromagnetic induction measurements of terrain conductivity, as well as electrical resistivity tomography and mise-a-la-masse surveys were performed in an attempt to delineate the source water of the seep. The geophysical methods identified potential flow paths from the impoundment to the seep; however, a geochemical analysis of the seep outflow was compared to the same analysis of the impoundment water on the upstream side of the dam and found to be statistically different.

Everchanging arctic climate conditions continue to negatively impact the habitat of the polar bear. The changes cause them to search for food outside of their traditional hunting grounds and potentially encounter humans in locations where interactions weren’t previously documented. One such occurrence in 2018 found a female polar bear at Summit Science Station near the center of the Greenland Ice Sheet (GIS) which is over 300 km from the closest traditional food source. In an attempt to mitigate the safety concern posed by potential interactions, the U. S. National Science Foundation-Office of Polar Programs-Arctic Sciences-Research Support and Logistics Program (NSF-OPP-ARC-RSL) has sponsored an effort to evaluate new technologies for use as a perimeter monitoring tool around remote arctic research camps. Distributed acoustic sensing (DAS), a technology often used for perimeter detection in high security areas, uses fiber optic technology to sense mechanical vibrations due to seismic or acoustic sources, including foot-steps. The systems are typically very sensitive and can not only be used to detect an intrusion, but often characterize the type of intrusion. Sensor ground coupling in soil is well understood for these systems; however, use in arctic conditions with direct snow coupling is not. A range of human foot pressures was used to simulate foot pressures of various sized polar bears. The very large surface area of the polar bear foot when considered over three points of contact for a walking quadruped, results in a similar foot pressure when compared to the single point of contact of a walking human. Using polar bear analogues, we demonstrate DAS performance in direct snow coupling, evaluate the loss in system sensitivity due to increasing snow pack and assess the effects of extreme cold on fiber optic sensors down to -70 degrees Celsius.