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SECOND QUARTER 2003 GROUNDWATER MONITORING REPORT AND ADDITIONAL ASSESSMENT REPORT JAIVIAR OIL DLSTRMUTION JUNE 2003 In April 2002, GHH Submitted an Additional Assessment Workplan in response to County directives for additional investigation at the site. The County approved the workplan in a letter dated May 28, 2002. On January 13-16, 2003, three cone penetrometer borings (CPT) and three geoprobe borings were advanced to depths between 104-feet below ground surface (bgs) and 122-feet bgs. General lithology logs generated with a CPT computer program showed little geologic or hydrologic variation between borings. Groundwater samples collected documented that the eastern limit of MTBE- impacted groundwater was not defined. A southeastern limit to MTBE impacted groundwater was defined on the southeast comer of East Main Street and Oro Avenue. SCOPE OF WORK The following is a brief summary of the scope of work authorized by JAMAR, which consisted of completing the extraction well installation on May 19, 2043, completing the installation of the two sets of clustered monitoring wells on May 20-23, 2003, conducting three slug tests and five aquifer performance tests on May 22, 2003 and conducting second quarter groundwater monitoring on May 29, 2003. i Extraction Well and Monitoring Well Installation • Prepare a site specific health and safety plan (HSP). • Obtain necessary boring and well permits from San Joaquin County (County). • Obtain encroachment permit from San Joaquin County for monitoring wells. • Obtain Underground Service Alert(LISA) clearance. • Drill and install onsite extraction well EW-1 and off-site, clustered, monitoring wells MW-6A, MW-6B, MW-7A and MW-7B. • Develop the groundwater monitoring wells. • Survey the elevation of new groundwater extraction well and monitoring wells. 3