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4�+ 1 ' Mr Don Rodgers Project 792774 01000000 May 2, 2000 Page 2 ' Between September 17 and October 11, 1996, EMCON 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 1 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 Polychlorinated bi-phenyls, ' TPHD, and chlorinated hydrocarbons were below laboratory detection limits in all soil samples analyzed from soil borings B-2R and B-6R ' TPHG, 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-1R TPHG 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 2000 ' On February 22 and 25, 2000, an IT technician was on site to measure depth to groundwater and collect a groundwater sample from well MW-1R for subjective and laboratory analyses 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-1R was analyzed at Sequoia Analytical in Sacramento, California The groundwater sample was analyzed for TPHG 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 TPHG was detected at a concentration of 3,380 micrograms per liter (µg/L}, BTEX constituents were detected at concentrations of 403 µg/L, 72 µg/L, 191 µg/L, and 191 µgfL, respectively, and MTBE was below raised laboratory detection limits at <25 µg/L using USEPA 1 Method 8020 Results of laboratory analyses are presented in the Table 1 Groundwater analytical IC"1CamPkUData\ArchivelRodgerslQtrlyIRDGRIg6o doc-981ot I IT Corporation