The oxidation, or evaporation pond historically received waste from CSSA's bluing operation performed in Building 90-2, reportedly from 1975 to 1984 (Parsons ES, 1993). Investigations performed to date on SWMU O-1 identified the chlorinated solvent PCE, and the metals, cadmium and chromium above background levels. The Texas Natural Resource Conservation Commission (TNRCC) risk reduction standard (RRS) 1 was identified as the goal for closure of SWMU O-1. This standard is a clean closure where soils are remediated to pre-existing background conditions.

Parsons ES, AFCEE, and CSSA identified potential technologies which would remediate solvents and metals at SWMU O-1. These technologies include low temperature thermal desorption; stabilization/solidification; soil vapor extraction; soil roasting/washing/leaching; and landfilling. CSSA's requirements for remediation included a minimum was off-site disposal and a treatment technology not involving a treatment train. Electrokinetic remediation, an emerging and innovative remedial technology, was chosen for its ability to remediate both chlorinated solvents and heavy metals from contaminated soils. Electrokinetic remediation comprises the application of an electric field between the electrode wells positioned in the soil and utilization of the electrokinetic phenomena induced in the soil for removal of contaminants. An additional process, the SULCHEM^TM process, was also identified; however, the technology vendor no longer provides the service.

The primary tasks performed as part of the electrokinetic treatability study are briefly outlined below.

1. Initial efforts were made to identify an acceptable location for the field pilot study area and to provide soil from the chosen area for a laboratory benchscale test. Soil samples were collected to assess the contaminant levels from three potential areas within SWMU O-1.

2. SWMU O-1 soil from the chosen area of the field pilot study was collected for a laboratory benchscale test. Tests included batch tests for determining the optimum extractant for removing chromium from SWMU O-1 soils, a determination of the valence state of chromium after removal, and tests to control soil swelling.

3. Soil samples collected during the construction of the pilot scale field test unit in July 1997 were used to establish baseline conditions of the chosen area.

4. Construction of the field test unit was completed 15 August 1997. The field test operations began with an effort to acidify the soils within the area using a mixture of citric and hydrochloric acid.

5. Initial operations for contaminant removal commenced 26 September 1997. Soil samples were collected to provide data on contaminant levels present in "control zones" between the anode and cathode wells.

6. Periodic monitoring and testing of the system was coordinated by Lynntech, Inc., with results discussed in this report and presented in Appendix A.

7. The system operation was shut down 23 December 1997 and soil samples were collected to assess the operation of the unit. The electrokinetic field test unit was operated for 89 days.

The limitations of the study include a shortened electrokinetic operation schedule, limited valid PCE analytical data, and no data regarding complexation of metals with citric and hydrochloric acids used in acidifying the surface soils at SWMU O-1.

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