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Dim ENGINEERING AND CONSTRUCTION, INC. 1 120 HOLLYWOOD AVENUE,SUITE 3,OAKLAND,CALIFORNIA 94502 SITE:Navarra Property SITE ADDRESS: 7500 W. 11th. Street, Tracy CA 95304-9305 San Joaquin County Environmental Health Department Site Code: 1392 Status of Plume of Dissolved Contaminants in Groundwater Site History The property at 7500 West Eleventh Street in Tracy was used as a fueling station for trucks and other vehicles from circa.1930 until 1998. In 1998 the fueling station was closed and all underground fuel storage tanks were removed from the site in December of that year. When the underground tanks were removed it was found that buried piping beneath the fueling station pump island had leaked and released diesel and gasoline fuel into the underlying soil and groundwater. In some areas of the site approximately 2000 gallons of the released fuels was found to be floating on the groundwater. However, the floating fuels were removed by suctioning into vacuum trucks and that material was transported for recycling in beneficial use. Following removal of the underground storage tanks, an extensive program of site characterization and groundwater-quality monitoring was undertaken under the direction and oversight of the San Joaquin County Environmental Health Department. Those investigations found that a plume of contaminated groundwater extended some 1000 ft. to the north northeast down the groundwater gradient from the 7500 West Eleventh Streets site to a point close to the intersection of Chrisman Road and Carmelo Avenue. The contaminants in the plume include diesel and gasoline and the gasoline components benzene, toluene, ethyl benzene, xylene isomers, tert-butyl alcohol, tert-amyl methyl ether and methyl tertiary butyl ether(MTBE). Current Status of Plume of Contaminants Following removal of the fuels floating on the groundwater, the concentrations of contaminants in the plume have been decreasing due to natural processes of attenuation which include natural bioremediation. Figure 1, which is attached, shows the current extent of the area affected by diesel and gasoline and the fringe of MTBE that extends beyond that due to MTBE's greater mobility in the underground. Analyses have shown that the components of the hydrocarbon fuels in the subsurface do not pose a risk to human health. The plume is now stable and contaminant concentrations are now sufficiently low and the rate at which they are being reduced by natural attenuation is sufficient for the California State Water Resources Control Board to have recommended that no further active remediation or groundwater-quality monitoring need be undertaken. Projected Future Status of Plume of Contaminants As the processes of natural remediation continue to reduce the concentration of contaminants in the plume, its area will be further reduced and it is estimated that no contaminants will be detectable in the groundwater within 15 years from 2012. DJW 05/07/12 TELEPHONE:OAKLAND,CALIFORNIA(51 0) 336-91 18 TRACY, CALIFORNIA(209)832-2910