2. Environmental Geotechnology Presentation Site OT-16B, Shaw Air Force Base, South Carolina, USA By Oliver Edwards And Alaric Shenton

3. Introduction Located 7 miles west of Sumter, SC Home to the 9 th Air Force and 20 th Fighter Wing Land use: Operational Air Base Since 1941 Maintenance Ground Conditions Upper Black Creek Aquifer Clays, Silts, Silty Sand and Clayey Sand

4. Contamination Contaminant spill in early 1995 Consisted of two plumes aquifer: Plume 1 = TCE and PCE Plume 2 = TCE alone TCE = Trichloroethylene PCE = Tetrachloroethylene No immediate risk to population

5. PCE And TCE Organic halogenic solvents Mainly used to de-grease metal Most common GW contaminant Acceptable Level in USA = 5ppb Recorded levels up to 90ppb Health Problems: –Liver, Kidney, nervous system, and immune system damage –Linked to cancer

6. PCE And TCE Structure: Cl Cl C C C C Cl Cl H Cl C C C C Cl Cl Tetrachloroethylene Trichloroethylene Dense Non-Aqueous Phase Liquid (DNAPL) Highly Volatile Partition Coefficients, K oc = 2 – 2.7 Highly mobile in soil Biodegradation = Vinyl Chloride (anaerobic) Doesn’t build up significantly in plants

7. Alternative Solutions considered Mass Removal of Contaminants - Very large site - Not cost effective

8. Other Possible Solutions Irrigation Volatilisation Bio-Remediation Soil Vapour Extraction

9. Interim Action System Achieved through Active Pumping - Pumping of contaminated water - Treated - Returned to the ground One recovery well System installed to provide hydraulic containment

10. Interim Action System 40.5 gallons of TCE and PCE removed 22 months to complete Containment system cost $1.96M Cumulative pumping cost $50K

11. Remedial Action Began in January 1998 Three extraction wells installed Located within and at edge of groundwater plume Fully cleaned by 2001