GEOPHYSICAL INVESTIGATION OF A SUPERFUND SITE IN NEW HAVEN, MISSOURI

The UMR fall 2002 field geophysics class conducted an integrated ground penetrating radar (GPR), magnetic (M), electromagnetic (EM), electrical resistivity (ER) geophysical study of Operable Unit 2 (the Kellwood Site) at the New Haven Superfund site, New Haven, MO. Contamination at the site consists of a shallow (~15-50 ft) tetrachloroethene (PCE) plume. Objectives for the study were: 1) locate abandoned sewer pipes near the point of release (i.e., potential conduits for transporting PCE off-site), 2) map the bedrock at the point of PCE release, and 3) map the bedrock down-gradient from the point of release. Students were responsible for survey setup, data acquisition, and data processing as the main project for this field geophysics methods class.

GPR, M, and EM methods were unable to locate the abandoned clay-tile sewer pipes near the point of PCE release because of signal degradation in the highly conductive soil covering the pipes and the non-metallic composition of the pipes. The presence of this highly conductive soil layer also inhibited the ability of these techniques to map the soil-bedrock contact at the point of PCE release.

Results of previous drilling down-gradient from the point of release indicated a rapid, unexplained change in bedrock depth over a narrow interval. The base of regolith within this deeper interval is composed of cobbles different from the bedrock. ER was highly successful in imaging a trough in the bedrock that, in conjunction with drilling data, is interpreted as a paleo stream channel. This channel has the potential to control the direction of contaminant migration. Thus, based on these results, further geophysical investigation at the site is warranted and, indeed, planned for the near future.