Geophysical Investigations at a Buried Disposal Site on Fort Richardson, Alaska

摘要

The Poleline Road Disposal Area, located on Fort Richardson, Alaska, was a U.S.Army dump in the early 1950s. In 1990 it was identified as an area potentially contaminated with volatile organic compounds. CRREL conducted extensive geophysical investigations that delineated anomalous responses in many areas of burial within glacial outwash deposits. Ground penetrating radar and electromagnetic induction surveys were used prior and subsequent to excavation. Geophysical data collected on a 5-m grid defined locations for several anomalous areas containing both dispersed and large, discrete targets. Radar defined anomalous areas by the concentration of strong diffractions. The induction survey differentiated metallic from nonmetallic contaminations. The interpreted maximum depth of debris was 4 m. Uncontaminated areas were generally defined by continuous, horizontal radar reflections, suggesting undisturbed or compacted soil horizons. The anomaly maps produced from these surveys guided an excavation that removed hazardous material. The removed material included munitions, mustard gas cylinders, medical waste, steel drums, and other trash. The radar and electromagnetic surveys were repeated using a more closely spaced grid to verify that the excavated areas were clean and to define more precisely anomalies in the areas not excavated. That survey shows many targets of potential or present contamination that should be removed.