Locating LNAPL contamination in the field using GPR velocity anomalies: examples from Hill AFB,Utah, USA

摘要

A large scale single offset ground-penetrating radar survey at Hill AFB, Utah, USA, produced a detailed map of the surface of a clay aquitard beneath a NAPL contaminated, unconfined sand and gravel aquifer. Analysis of these data led to identification of several reflectivity and topographic anomalies thought likely to indicate the presence of NAPL. Targeted continuous multi-fold GPR acquisition coupled with reflection tomography and prestack depth migration, showed that these reflectivity anomalies were associated with elevated radar propagation velocity; this response is consistent with NAPL contamination. Subsequent laser induced fluorescence and chemical analysis of borehole samples verified this interpretation.