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Mr John Benedict Project 880039 IA April 19, 2001 Page 2 Between September 17 and October 11, 1996, EMCON/OWT observed the drilling of six soil borings (B-1R through B-6R) One soil boring was converted to monitoring well MW-1R, three soil borings were converted to dual completion vapor extraction wells VW-1 through VW-3, and one soil boring was converted to a single vapor extraction well VW-4 (EMCON, Preliminary Investigation and Evaluation Report, February 5, 1997) The results of this investigation indicated the following • With the exception of soil samples collected from boring B-6R, residual hydrocarbons were detected in each boring The highest concentrations were detected approximately ' 10 feet below ground surface (bgs) near the former USTs Total oil and grease was detected in the soil sample collected near the former UST cavity (located near the building) at a concentration of 10,000 parts per million Polychlonnated biphenyls, ' TPH-d, and chlorinated hydrocarbons were below laboratory detection limits in all soil samples analyzed from soil borings B-2R and B-6R • TPH-g, benzene, toluene, ethylbenzene, and total xylenes (BTEX) isomers, and methyl tert-butyl ether (MTBE) were detected in the groundwater sample collected from monitoring well MW-IR TPH-g and benzene were detected at concentrations of 33,000 parts per billion (ppb) and 1,400 ppb, respectively MTBE was detected at a concentration of 550 ppb GROUNDWATER MONITORING, FIRST QUARTER 2001 On February 15, 2001, an IT technician was on-site to measure depth to groundwater and collect a groundwater sample from well MW-IR for subjective and laboratory analyses The first quarter sampling was joindy conducted with former ARCO facility 2168, located east and downgradient of I the subject site Floating product was not observed in groundwater monitoring well MW-1R (see Table 1 and Appendix A) IT used these data to evaluate changes in concentrations of dissolved gasoline hydrocarbons in the groundwater IT's sampling and analysis procedures are presented in Appendix B The groundwater sample collected from monitoring well MW-1 R was analyzed at ' Sequoia Analytical in Sacramento, California The groundwater sample was analyzed for TPH-g using U S Environmental Protection Agency (USEPA) Modified Methods 8015, and for BTEX and MTBE using USEPA Method 8020 Copies of the chain-of-custody records and laboratory analysis reports are presented in Appendix C The results of laboratory analyses indicated that dissolved hydrocarbons were present in the monitoring well TPH-g was detected at a concentration of 234 micrograms per liter (pg/L), benzene, toluene, ethylbenzene, and total xylene constituents were detected at concentrations of IT CORPORATION SAC 1N lrancfp]\Proiccts\Projects1880103911A1Quarter[ys11g01 doc-Mit 1 (01010000)