Remediation of overlapping benzene/MTBE and MTBE-only plumes: A case study
- TolTest, Inc., Pittsburgh, PA (United States)
- Ryder Transportation Services, Lawrenceville, NJ (United States)
Two overlapping dissolved hydrocarbon plumes were identified in the shallow water-bearing zone at a commercial vehicle service and fueling facility. Plume 1 originated from a pre-1993 gasoline product line/dispenser leak. This plume contained a relatively common mix of benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl tert-butyl ether (MTBE); benzene and MTBE were identified as the Plume 1 contaminants of concern based on their detection at approximately 200 {mu}g/l each, which exceeded regulatory guidance. Plume 2, which was detected in the tank cavity during UST removal, resulted from gasoline line leaks/underground storage tank overfills. Although the majority of impacted soils in both the dispenser and tank cavity areas were removed during UST excavation, rainfall during impacted soil removal mobilized the MTBE contained in the soils to groundwater. As a result, Plume 2 contained approximately 900 {mu}g/l MTBE while BTEX compounds were non-detect. Although the impacted zone sustained an approximate yield of only 0.3 gallon per minute, Pennsylvania regulations dictate that this zone must be treated as an aquifer. The failure of remediating gasoline plumes using pump-and-treat has been predominantly due to BTEX`s tendency to adsorb onto soil, creating a residual-phase product layer which acts as a continuing source of dissolved-phase BTEX. Based on this experience, most groundwater and remediation professionals reject pump-and-treat as a viable remedial option, except in situations where controlling groundwater movement is the predominant goal.
- OSTI ID:
- 569895
- Report Number(s):
- CONF-971116--
- Country of Publication:
- United States
- Language:
- English
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