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• Mr Don Rodgers Project 2613-100 003 <br /> August 18, 1998 <br /> Page 2 <br /> Between September 17 and October 11, 1996, Pinnacle observed the drilling of six soil borings <br /> (B-1R through B-6R) One soil boring was converted to monitoring well MW-1R, three soil <br /> borings were converted to dual completion vapor extraction wells VW-1 through VW-3, and one <br /> soil boring was converted to a single vapor extraction well VW-4 (EMCON, Preliminary <br /> Investigation and Evaluation Report, February 5, 1997) The results of this investigation <br /> indicated the following <br /> • The majority of residual hydrocarbons were detected in the vicinity of the former USTs <br /> and dispenser islands With the exception of soil samples collected from boring B-6R, <br /> residual hydrocarbons were detected in each boring The highest concentrations were <br /> detected approximately 10 feet below ground surface (bgs) near the former USTs Total <br /> oil and grease was detected in the soil sample collected near the former UST cavity <br /> (located near the building) at a concentration of 10,000 parts per million <br /> PolychIonnated bi-phenyls, TPHD, and chlorinated hydrocarbons were below <br /> laboratory detection limits in all soil samples analyzed from soil borings B-2R <br /> and B-6R <br /> • Groundwater was encountered at approximately 31 to 38 feet bgs On <br /> September 30, 1996, static groundwater was measured at 26 44 feet bgs in monitoring <br /> well MW-1R Groundwater elevation is consistent with groundwater elevations <br /> measured at adjacent properties <br /> • TPHG, benzene, toluene, ethylbenzene, and total xylene (BTEX) isomers, and methyl <br /> tert-butyl ether (MTBE) compounds were detected in monitoring well MW-1R TPHG <br /> and benzene were detected at concentrations of 33,000 parts per billion (ppb) and <br /> 1,400 ppb, respectively, MTBE was detected at a concentration of 550 ppb <br /> GROUNDWATER MONITORING: SECOND QUARTER 1998 <br /> On May 21, 1998, a Pinnacle technician was on site to measure depth to groundwater and collect a <br /> groundwater sample from well MW-1R for subjective and laboratory analyses Floating product <br /> was not observed in groundwater monitoring well MW-1R (see Table 1 and Appendix A) Pinnacle <br /> used these data to evaluate changes in concentrations of dissolved gasoline hydrocarbons in the <br /> groundwater Pinnacle's sampling and analysis procedures are presented in Appendix B <br /> The groundwater sample collected from monitoring well MW-1R was analyzed at Sequoia <br /> Analytical in Sacramento, California The groundwater sample was analyzed for TPHG using <br /> U S Environmental Protection Agency (USEPA) Modified Method 8015 and for BTEX and <br /> . MTBE using USEPA Method 8020 In addition, per the California Regional Water Quality <br /> Control Board, Central Valley Region, requirements, the groundwater sample was analyzed for <br /> SAC1A\RODGERS OM2-981mtt 1 PC""& <br /> Rev 0,August 18,1998 <br />