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RECEIVED NOV 2 6 2012 DIETZ ENGINEERING AND CONSTRUCTION, INC. 1 120 HOLLYWOOD AVENUE,SUITE 3,OAKLAND,CALIFORNIA 94602 ENVIRONMENTAL HEALTH PERMITISERVICES Notice: Pending Closure of the Leaking Underground Storage Tank (UST)` Case at 7500 W. -11th. Street, Tracy CA 95304-9305, the .former Navarra Property, .by the San Joaquin County Environmental Health Department (EHD), Site Code: 1392 An investigation and characterization of the-impact from an unauthorized release from a former UST system on the above referenced site has been completed under the regulatory oversight of the EHD. The j EHD has concluded that the investigation and characterization of the release::has been completed and is adequate to determine that there-is no longer a significant health risk -or hazard to the .public or to the environment associated with this' release and is considering closure of the case. The EH.D will be accepting and considering comments from the public regarding the pending case closure fora 60-day period from December 1, 2012 through January 29, 2013,, be fore,proceeding_w.ithahecase closure:ir--r-� Comments-should be--Airected-to`M Nue[Henderson by mail at 186$ E. Hazelton Ave., Stockton, CA 95205,by phone at(209)468-3436, or by email at nhenderson@sjeehd.com. 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. 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 were found to be floating on the, groundwater; the.`floating fuels were removed by suctioning into vacuum trucks and transported for recycling for 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 .EHD. Those investigations found thata plume of contaminated groundwater extended some 1000 ft. to the north northeast down the groundwater gradient from the 1500 West Eleventh'Street 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(MT.BE): 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 4s attached:"shows'h6 current extent of dd the area:.ffc:ted oy diesel gird gasoline and the fringe of MTBE that extends beyond that due to MT.BE'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 w.hich 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 11/16/12 TELEPHONE:OAKLAND, CALIFORNIA(51 0)336-91 18 TRACY,CALIFORNIA(209)832-2910