Completed Project
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| Contaminants Treated: | TCE, TCA, DCE, DNAPL |
| Starting Contaminant Levels: | Avg. TCE 38,000 ug/l; TCA 37,000 ug/l; DCE 18,000 ug/l |
| Treatment Depth: | 25 feet bgs |
| Treatment Volume: | 32,000 cubic yds |
| Cleanup Levels Achieved: | Yes, Exceeded Goals Ahead of Schedule; Achieved > avg. 99% reduction in contaminants; TCE 97 ug/l; TCA 23 ug/l; DCE 300 ug/l |
| Has Rebound Occurred: | No. In fact, the groundwater concentrations declined by an average 23% one year after the project was completed. |
| Geology: | Heterogeneous silty sands with clay lenses |
| Hydrology: | Groundwater between 3-7 feet bgs |
| Remediation Time Period: | June 6, 1998 - April 30, 1999 |
| Project Manager: | Mr. Greg Beyke |
| Remediation Design Engineer: | Mr. Greg Beyke |
| Operations Manager: | Mr. Jerry Wolf |
| Percentage of the Work Performed by Personnel now Working for TRS: | |
| Design: | 100% |
| Installation Oversight: | 100% |
| Installation: | >90% |
| Operation Oversight | 100% |
| Operations: | >90% |
ENSR had been working to remove chlorinated solvents at a former manufacturing facility located in Skokie, Illinois since 1991 by combining steam injection and soil vapor extraction with bioremediation and groundwater extraction. After seven years, these technologies had reduced overall site impact, but left behind three large hot spot areas. ERH was chosen in 1998 to remediate Trichloroethylene (TCE) and 1,1,1-Trichloroethane (TCA) in the areas which contained DNAPL in tight heterogeneous soil. Once ERH was started, the cleanup objectives were reached, representing an average of 99.8% reduction in contaminant concentrations in ground water in less than five months of operations.
Site lithology consisted of heterogeneous clayey silts to 20 feet below ground surface (bgs) and a dense silty clay till from 20 to 25 feet bgs. Groundwater was encountered between 3 and 7 feet bgs and hydraulic conductivity throughout the remediation zone ranged from10-4 to 10-8 cm/sec. To treat beneath a warehouse, 85 electrodes were constructed through the floor of the building and 22 electrodes were installed outside the building. The electrodes actively heated the depth interval from 5 to 24 feet bgs. Chlorinated solvent vapors were collected by a network of 37 soil vapor extraction wells screened to 5 feet bgs.
Heating began on June 4, 1998. Within 60 days, temperatures throughout the entire 23,100 cubic yards treatment volume had reached the boiling point of water. With another 70 days of heating using ERH, separate phase DNAPL had been removed and groundwater concentrations of TCE/TCA were reduced to below the risk based target cleanup levels. The client was so pleased with the initial results he expanded the ERH treatment area to include an additional 8,500 cubic yards of impacted soil. With another ninety days of heating, including the new impact area, the cleanup objectives were exceeded on over 95% of the total impacted area. Cleanup results are shown below. The final total treatment volume was 31,600 cubic yards.
| Table 1. Summary of Groundwater Cleanup Results | ||||
| Well | Compound | Mar '98 (ug/l) | Nov '98 (ug/l) | Reduction (%) |
| B-3 | TCE TCA |
34,000 82,000 |
120 31 |
99.6 99.9 |
| Fa2 | TCE TCA |
22,000 24,000 |
70 24 |
99.7 99.9 |
| C4 | TCE TCA |
76,000 11,000 |
100 15 |
99.9 99.9 |
One year following ERH remediation operations groundwater concentrations continued to decline by an average 23%. The Illinois EPA issued a letter of No Further Action (NFA) in 2000. This site has been closed and redeveloped into a mixed-use shopping mall, cinema, and office building.
Figure 1. Contaminant Concentrations in Groundwater Before and After ERH Operations
Contaminant concentrations in groundwater over time are presented in Figure 1 above. The ERH remediation exceeded expectations and the cleanup goals for each of the contaminants of concern. In the seven most contaminated wells groundwater concentrations of TCE, TCA and DCE were reduced by an average 99.7%, 99.9%, and 98.3%, respectively.