SITE INFORMATION AND CORRESPONDENCE

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CHRONOLOGY CALIFORNIA HIGHWAY PATROL 385 GRANT LINE ROAD, TRACY 3125-26199 Four geoprobe borings were pushed to 25 feet below ground surface (bgs) around a 12,000 gallon gasoline underground storage tank (UST), to investigate if an unauthorized release had occurred. 4120199 Date of the"Subsurface Investigation Report"with results of the March 1999 investigation. The soil samples collected from 25 feet bgs had MTBE contamination and so did the grab water samples. 4128199 The site was placed in the Local Oversight Program and the responsible party was directed to submit a work plan to define the extent of the contamination at the site. 5118100 The 12,000 gallon UST was removed on this date. Four side wall soil samples and a grab water sample was collected from the excavation. 6122100 Monitoring wells MW1, MW2 and MW3 were installed on this date. 9114100 Date of the URS Greiner report on the installation of the three monitoring wells on 6122100. The wells were screened from 5 to 15 feet. The only soil samples analyzed were from 6 feet deep and MTBE was detected in these samples. MTBE was detected in the water samples also. 10/18/00 Date of the Environmental Health Department(EHD) letter directing submittal of a work plan to investigate the extent of the contamination. 1125101 Date of another EHD letter requiring a work plan be submitted. 3116101 Date of a work plan proposing installation of one deep and two shallow monitoring wells on the adjacent private property north of the site (downgradient). 3130101 EHD approved the 3116101 work plan. 4110103 Date of the EHD letter agreeing to an on-site vertical investigation since off-site access could not be obtained. 411104 Monitoring well MW4(deep well) installed on site this date. 5126104 Date of Winzler Kelly report on installation of monitoring well MW4. 12/17/04 EHD staff discussed the site with the Regional Water Quality Control Board staff on this date. The water samples from MW4 (deep well)were non detect for analytes after three quarters of sampling and concentrations of MTBE in MW1, MW2 ans MW3 were below the maximum concentration levels allowed in public drinking water. It was decided that if the fourth quarter of sample results were similar that closure would be considered. 6130105 Date of the "No Further Action Required"report prepared by Kleinfelder. No contaminants were detected in the water samples from MW4 after four quarters of sampling. The only contaminant found in the last quarter of samples was in the water sample from MW2 that had 1.7 ppb of MTBE.