Why the technology was selected:
The Regenesis HRC® technology was selected because studies estimated the cost would be lower in comparison with other in situ bioremediation and in situ chemical oxidation technologies.

Date implemented:
April 2002

Final remediation design:
The HRC application (glycerol tripolylactate) was conducted April 22-26, 2002. Prior to the application, eight groundwater monitoring wells, which delineated the plume extent, were sampled to quantify baseline groundwater contaminant concentrations. In the source area, where the highest soil contaminant concentrations were detected at 4-6 ft, a directional drill rig was used to inject a total of 1,080 lbs of HRC into 4, 40-ft horizontal borings beneath the Cleaners, at depths ranging from 7-9 ft below the floor surface. Outside the source area, a Power Probe with an expendable carbon-steel point and a Geoprobe grout pump were used to complete 105 vertical injections. At eight locations, 100 lbs of HRC was injected into each boring along the fire-main trench located outside the Cleaners (upgradient and adjacent to MW-12), from a depth of 3-13 ft bgs (total 800 lbs). At 97 locations, approximately 21 lbs of HRC were injected into each boring in the contaminant plume, from a depth of 3-9 ft bgs (total of 2,120 lbs).

Other technologies used:
A passive soil-gas survey (EMFLUX®)was utilized to delineate the contaminant plume before groundwater monitoring wells or DPT soil sampling was conducted. This was helpful in pinpointing contaminant hot spots.

Results to date:
The eight ground water monitoring wells are being sampled quarterly to monitor contaminant and bioenvironmental conditions. To date, seven quarters of monitoring data is available. Baseline sampling indicated that the most significantly impacted monitoring well (MW-12) had PCE and TCE concentrations of 1,790 1 µg/l and 1,758 µg/l respectively, prior to HRC application. These concentrations are 90% less than the highest detected. The latest quarter of data indicates a decline in PCE with respect to baseline concentrations. This decline is about 40% for the most impacted well and as much as 90% in other source area wells. PCE shows a consistent pattern of decline for all quarterly data from the source area samples. The most impacted well, and the wells immediately downgradient, however, exhibit some fluctuation within the downward trend. TCE concentrations at the most impacted well have also fluctuated above and below baseline levels with the latest quarter of data, indicating an increase above baseline conditions but an 86% decrease below the highest detected at the site. Downgradient wells indicate slightly fluctuating-to-steady TCE concentrations. Source area wells indicate an overall decline in TCE. Other degradation by-products (DCE and VC) have indicated a flucuating trend above and below baseline limits with the largest degradation by-product concentration occurring at the most impacted well. There were no indications that contaminant plumes have migrated or advanced beyond previously defined boundaries. It is not certain if the noted decline in parent product, when compared to baseline concentrations, is a result of the HRC remedy. In the most impacted well, the largest reduction in contaminant concentration (from NAPL) to dissolved phase concentrations) occurred prior to HRC injection. The cause of the decline is unknown; however, potential lab result discrepancies have been identified with some of the reported data. In addition, favorable reductive groundwater conditions are not supported by the geochemical data although a slight increase of respiration by-products (CO2) and degradation by-products (cl-) during some quarters seem to indicate active biodegradation.

Next Steps:
1. Comprehensive review of site analytical and geochemical data along with collection and analysis methods. 2. Considering ISCO application to reach cleanup goals.

Cost to Design and Implement:
$124,524