Felsic metavolcanic and metasedimentary rocks underlie the site. A high-angle reverse fault crosses the center of the site and separates the two rock types. Differential weathering of rocks on either side of the fault is indicated by variable thicknesses of a saprolite-bedrock transition zone.
Targeted Environmental Media:
 Fractured Bedrock
The major contaminants at this site are chlorinated ethenes and ethanes. The ground-water contamination is mostly restricted to the fractured bedrock, at a depth of up to approximately 100 feet, because of extensive dewatering of the overlying saprolite and weathered rock (transition) zone due to ground-water extraction. Bedrock ground-water flow is oriented parallel to the fault strike in the vicinity of the fault and ground-water contaminants have been diverted in a direction parallel to the fault strike for approximately 1000 feet at a nearly right angle to the topographic slope.
Major Contaminants and Maximum Concentrations:
- Trichloroethene (var)
- Vertical Chemical Profiling
- Cluster Wells
- Multi-sampling port
- Coring
- Pump and Treat
- Multi Phase Extraction
Comments:
The plume's parameter appears to be decreasing as a result of continued groundwater extraction.
The use of in-situ chemical oxidation to enhance subsurface VOC removal has been discussed for enhancement to the groundwater remediation. A pilot-scale trial has been suggested although no formally proposed.
The dual phase (groundwater and soil vapor) extraction wells in the contaminant source areas are enhancing recovery of VOCs by soil vapor extraction (150 pounds of total VOCs removed by soil vapor extraction (SVE) in 2001 with the dual-phase wells operating versus ~ 25 pounds of VOCs removed by SVE in 2000. Speculation suggests the enhanced source area SVE upgradient of the near-source ground-water recovery wells is responsible for the dramatic concentration decreases of the recovery wells.
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