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R603 UPDATE-19 8/24/93 GROUND WATER QUARTERLY SAMPLING • Ground water samples were collected on June 14 1993 1 . These samples were collected b a WEGEgeologist see Table y of Custody" delivered on ice toa state certified testing laboratory (SUPERIOR PRECISION ANALYTICAL, INC DHS#1332) for chemical analyses . These samples were analyzed for TPH and BTEX concentrations using EPA Methods 8015 and 602 respectively. Since diesel has never shown up in the sample results, the samples obtained on 11/27/90 and later were analyzed using EPA methods 5030 and 602 for Total Fuel Hydrocarbons and BTEX The next quarterly sampling will occur in September, 1993 . 3 . 0 RESULTS GROUND WATER SAMPLE RESULTS Ground water samples were obtained from all of the monitoring wells on June 14, 1993 The latest sample results showed a decline in contaminant levels associated with the ground water at MW1 and MW3 . Of the other wells that have some degree of ground water contamination (MW2 , MW8 , MW10 and MW12) showed slight increases, see Table 1 The increase in contaminant concentrations found at MW2 and MW10 is thought to be associated with the vacuum extraction at these wells, concentrating the contaminant from adjacent areas to the source of the vacuum, see Table 1 The increase in contaminant concentrations found at MW8 and MW12 is associated with the rise in the ground water to near the 50 foot depth This depth is where the highest levels of gasoline range hydrocarbons have been detected in soil samples from the exploration and well borings VAPOR RECOVERY OPERATIONS AND RESULTS Presently (July 19, 1993) the REMOX units have operated for a total of 10283 hours out of a total of 14922 hours (68 9°s) The new replacement unit has operated 6281 hours out of 8041 . 5 hours (78°s) , removing and destroying and estimated 70155 pounds of gasoline range hydrocarbons (July 19, 1993) and an estimated 63240 pounds of oxidized gasoline range hydrocarbons as CO2 (Average 200 cfm flow rate X average CO211 (1 25) x 10283 hours operated x 60 min/hour x pound CO2 conversion 0 00041 lb/cf/o) for a total of 133395 pounds of gasoline range hydrocarbons removed from the subsurface, see Tables 2, and 3 and Appendix C- Air Monitoring Report . Since February 18, 1993 the vapor recovery/destruction has been declining from an average above 200 pounds per day of gasoline range hydrocarbons to below 50 pounds per day of gasoline range hydrocarbons, see Table 2 and concentration charts Figures 5A and 5B These charts indicate that the lighter compounds of gasoline range hydrocarbons (benzene, toluene, etc ) have been greatly reduced with a moderate reduction of the heavier compounds PAGE 2