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I CAM BRIA In October 1990, Aegis installed wells MW-1, MW-2, and MW-3. Soil samples collected from the well borings and the initial groundwater samples collected from the wells did not contain detectable concentrations of TPHg, benzene, toluene, ethylbenzene, or xylenes (BTEX). This investigation is summarized in Aegis' March 26, 1991 Site Assessment/Monitoring Well Installation Results Report. In August 1995, Fugro West, Inc. (Fugro) of Roseville, California drilled one soil boring and installed well MW-4. TPHg and BTEX were not detected in any soil samples collected from this boring or in the initial groundwater samples from well MW-4. These activities are summarized in Fugros' November 27, 1995 Subsurface Investigation Results, Annual Fourth Quarter 1995, Ground Water Monitoring Report, and Case Closure Request. iB in a letter dated July 18 � Site closure was granted by the RWQC , 1996. On October 15, 1996, Enviros, Inc. (Enviros) destroyed wells MW-1 through MW-4 by pressure grouting. These activities are described in Enviros' November 19, 1996 Well Destruction Report. In January 1999, Triangle Construction of Sacramento, California removed the gasoline l USTs, dispensers, and associated piping. Cambria observed the UST removal on January 19, 1999 and collected samples from the tank excavation bottom and from beneath the former dispensers, product piping, vapor recovery piping, and vent lines on January 22, 1999. Based on the analytical results from these soil samples, Cambria returned to the site on February 4, 1999 and conducted over-excavation in several locations. Soil samples were collected subsequent to over-excavation. These activities are documented in Cambria's June 11, 1999 Underground Storage Tank Removal Report. In February 1999, Stockton -Service Station Equipment Company, Inc. of Stockton, California installed a new gasoline UST, a new diesel UST, and five dispensers in the same locations as the former USTs and dispensers. In February 2000, Cambria drilled four soil borings near the northern dispensers and converted one of these borings into a monitoring well (MW-5). TPHg and benzene were not detected in soil or groundwater during this investigation. Methyl tertiary butyl ether (MTBE) was detected by EPA Method 8260A in well MW-5 at a concentration of 10.3 parts per billion (ppb) during the initial sampling event. Complete details of this investigation may be found in our September 8, 2000 Site Investigation/First Quarter 2000 Groundwater Monitoring Report. r I 1346 2 l