SITE INFORMATION AND CORRESPONDENCE

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ATC Associates Inc. (YA 1117 Lone Palm Avenue,Suite 201 Modesto,California 95351 209-579-2221 Fax:209-579-2225 ASSOCIATES INC. ATC submitted to the SJCEHD the Closure Summary Report dated December 12, 2010. In addition, ATC also submitted to the SJCEHD the Addendum to ATCs Closure Summary Report Former Thiemann's Service Station, 106 West Second Street, Ripon, California dated November 29, 2011. In this report and addendum, ATC utilized the Central Valley Regional Water Quality Control Board (CVRWQCB) No Further Action (NFAR) Reporting criteria, concluded that the site does not appear to represent a significant risk to human health or the environment. NFA status was requested for the site. On December 21, 2011, the CVRWQCB issued a No Further Action Required Concurrence letter for the site. The letter stated that the CVRWQCB reviewed the Case Closure summary sent by the SJCEHD and that the Board agreed with the County's recommendations to close the site. On January 9, 2012, the SJCEHD issued a letter stating that it received the CVRWQCB No Further Action Required Concurrence letter for the site and required groundwater monitoring wells be property abandoned. The letter also requested a work plan be submitted that addressed the SJCEHD concerns and the San Joaquin County Well Standards. SCOPE OF WORK Well Destruction On March 8 and 9, 2012, ATC supervised the destruction of monitoring wells MW1 through MW6. Wells MWt through MW3 were constructed with 2 inch diameter PVC inside an 8 inch borehole and set at a depth of 42 feet bgs. Wells MW4 through MW6 were constructed with 4- inch diameter PVC inside a 10 inch borehole and set at a depth of 40 feet bgs. The well abandonment was conducted by Precision Sampling, State C57 License No. 636387. For wells MW1, MW4 through MW6, neat cement grout was pumped into each well via tremie, until the pipe was completely filled. At each well a minimum of 25 psi of pressure was applied for a minimum of five minutes. An annular space of 22 inches was excavated around each well to a depth of 3 feet bgs. The wells were then backfilled with additional grout until the excavation was filled to a minimum of one foot above the top of the PVC pipe. The remaining excavation was backfilled with native soil and a concrete cap was installed. Wells MW2 and MW3 were overdrilled with 8 inch hollow stem auger to a depth of 46 feet and 51 feet respectively. Upon reaching total depth, each borehole was backfilled with neat cement grout to approximately one foot. Investigative Derived Waste Soils generated by the abandonment of the monitoring wells were stored in Department of Transportation approved drums. The soil generated during the well abandonment activities was tested by a state certified laboratory and the results indicate that no chemicals of concern were detected above the laboratory detection limits. Lead was detected at 14 mg/kg. The laboratory s:\62605-Thiemann\REPORTS\Well Abandonment summary rpt 4