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70 ' S E C 0 R ' Request for No Further Action Chevron Station 9-2396 December 16,2004 Page 1 ' 1.0 INTRODUCTION SECOR International Incorporated (SECOR), on behalf of Chevron Environmental Management Company (Chevron), has prepared this No Further Action Required (NFAR) request report for Chevron service station 9-2396 located at 25651 Highway 99 North In ' Acampo, CA (Figure 1) This NFAR request has been prepared for the San Joaquin County Environmental Health Department (County) to support an objective decision regarding the requested closure This report Includes the Information required by the ' outline for NFAR request report documentation' As required by the NFAR guidelines, a "check-off' table of required information for NFAR status was completed by SECOR and Is included as Appendix A 1 This report presents SECOR's understanding of existing conditions at the subject site The conclusions contained herein are based on analytical results and professional judgment in accordance with current standards of professional practice, no other warranty is expressed or Implied SECOR assumes no responsibility for data reported by other consultants or contractors ' 2 0 SETTING lie A summary of the regional geology, stratigraphy, and hydrogeology is presented In this section 21 Geology The San Joaquin Valley is the southern two-thirds of the Great Central Valley (Central Valley) geomorphic province2 It Is separated from its northern one-third, the Sacramento Valley, by the buried Stockton arch and combined river deltas of the Sacramento and San Joaquin Rivers This 430 mile long structural valley is an asymmetrical synclinal trough with a gently inclined undeformed eastern limb and a tightly folded and faulted narrow western limb Near Fresno, the valley reaches Its widest portion of 62 miles The Central Valley Is bounded on the south by the Tehachapi and San Emigdio Mountains, the east by ' the Sierra Nevada Mountains, the north by the Klamath Mountains, the northeast by the Cascade Range and the west by the Coast Range The basin drains Into the San Francisco Bay by the Sacramento and San Joaquin Rivers The structure of the Central Valley is controlled by Its tectonic evolution 3 As subduction of the Kula Plate comes to an end during the Eocene, the subsequent formation of the San ' Andreas Fault becomes the major tectonic Influence The result is the formation of ,' Regional Water Quality Control Board 2004 Tri Regional Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites Appendix A dated April 16 2 Hackel, O 1966, Summary of the Geology of the Great Valley Geology of Northern California Bulletin 190 California . Division of Mines and Geology,p 215-238 3 Bartow J A 1991 The Cenozoic Evolution of the San Joaquin Valley, California Professional Paper 1501 United States ' Geological Survey ' 11Chevron1923961Reports\FINAL_NFAR REPORT doe