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Ms Lori Duncan Project No 880-039 IA January 30, 2004 Page 2 .r collected from subsurface investigations performed at the former ARCO Service Station, Chevron Station, and Texaco Station (located at the corners of Charter Way and Lincoln Street), residual and dissolved hydrocarbons have been detected beneath those facilities Between September 17 and October 11, 1996, EMCONIOWT observed the drilling of six soil borings (B-1 R through B-6R) One soil boring was converted to monitoring well MW-1 R, 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 indicate the following • With the exception of soil samples collected from boring B-6R, residual hydrocarbons were reported an each boring The highest petroleum hydrocarbon concentrations were reported at approximately 10 feet below ground surface (bgs) near the former USTs Total Oil and Grease were reported in the soil sample collected near the former UST cavity (located near the building) at a concentration of 10,000 parts per million (ppm) M Polychlorinated biphenyls, TPHd, or chlorinated hydrocarbons were not detected in soil samples analyzed from soil borings B-2R and B-6R o TPHg, benzene, toluene, ethylbenzene, and total xylenes (BTEX), and methyl tert-butyl ether (MTBE) were reported in the groundwater sample collected from monitoring well MW-1R TPHg and benzene were reported at concentrations of 33,000 and 1,400 parts per billion (ppb), respectively MTBE was reported at a concentration of 550 ppb i GROUNDWATER MONITORING FOURTH QUARTER 2003 On November 3, 2003, a Shaw employee was on-site to measure depth to groundwater and collect ' groundwater samples from wells MW-1R through MW-4R(D), and VW-2 through VW-4 for laboratory analyses Shaw coordinated joint quarterly sampling with the adjacent service station sites Free product was not observed in groundwater monitoring wells (see Table 1 and Appendix A) Shaw used the fourth quarter 2003 data to evaluate changes in concentrations of dissolved petroleum hydrocarbons in the groundwater Shaw sampling and analysis procedures are presented in Appendix B The groundwater samples were analyzed by Severn Trent Laboratory in West Sacramento, California, for TPHg using U S Environmental Protection Agency (USEPA) Method 8015M, and for BTEX and MTBE using USEPA Method 8021B The results of laboratory analyses N 4sacDR20041PgI88018800391A 4aa doc Shaw Environmental,Inc