Why the technology was selected:
Bioremediation was thought to be the safest and most effective short- & long-term remedy for both soil and groundwater.

Date implemented:
April 2002 (pilot test for enhanced bioremediation)

Final remediation design:
The remedial design consisted of twelve 4" injection wells and eight 2" pilot test monitoring wells installed to a depth of 18-ft. One injection well was placed in the source area with five others placed parallel to the plume width, just upgradient of the source area end, at a 10-ft spacing. The remaining six wells were placed throughout the plume length, near or offset from the plume centerline. These wells were spaced between 20-30 ft apart. The eight pilot test monitoring wells were placed along the length of the plume downgradient of the upgradient injection wells and cross-gradient to the plume length injection wells. A baseline sampling event was conducted in April 2002 to establish pre-injection conditions. In May 1002, the wells were injected with a solution of corn syrup, simple green, and vegetable oil. This was continued on a two-week schedule until August with a one-time injection of emulsified soybean oil taking place in December. Effectiveness sampling was conducted in August 2002 and March 2003. Excavation of soil within the source area occurred in December 2004. Approximate area of excavation, 22ftx22ftx12ft. Sodium lactate (Wilclear) was added to the excavation.

Other technologies used:
Excavation of soil within the source area occurred in December 2004. Approximate area of excavation, 22ftx22ftx12ft.

Results to date:
The wells with the greatest PCE impact (PCE baseline concentration greater than 4-orders of magnitude higher than the PCE MCL) indicated a 85-95% decrease by August 2002. The March 2003 data indicated that one of these wells, which is located within the source area, maintained a concentration similar to the August 2002 level. The other well, located slightly downgradient of the source area, indicated a rebound to baseline concentrations. Another well, located slightly outside the centerline between these wells, indicated a rebound to greater than baseline concentrations. The baseline concentration for this well was about 2-orders of magnitude higher than the MCL. Wells located about midway along the plume and up to the leading edge, indicated no PCE detections. Baseline concentrations for these wells ranged from MCL levels up to about 2-orders of magnitude.

Next Steps:
Activities planned at the site include nutrient injections over the next two years with periodic effectiveness monitoring. In addition, sampling is planned in the future to assess the remedy effectiveness.