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r <br /> { v <br /> i wAddr- <br /> HORIZON ENVIRONMENTAL INC. <br /> Specialists in Site Assessment Remedial Testing,Design and Operation <br /> March 17, 2011 1106 J) <br /> Mr. Michael Infurna Svc) r,y <br /> San Joaquin County <br /> Environmental Health Department 04 ? '"Fre 1, 1 <br /> 600 East Main Street 3 7C'y 4'/0�9 <br /> Stockton, California 95202-3029 <br /> Subject: No Further Action Required Request $ZSa <br /> Beacon Station No. 3641 V1 <br /> 1210 East Hamner Lane, Stockton, California nv P. <br /> Mr. Infurna: <br /> Horizon Environmental Inc. (Horizon), on behalf of Ultramar, Inc. (Ultramar), is submitting <br /> the enclosed No Iirrther Action Required Request dated 17 March 2011. 'fie report was <br /> requested by the San Joaquin County Environmental Health Department (EHD) in a letter <br /> dated 26 October 2010. <br /> The report provides documentation upon which an objective decision may be made <br /> regarding the request for closure. The report was prepared in accordance with the <br /> requirements contained in the Regional Water Quality Control Board (RWQCB) Tri- <br /> Regional Board Staff Reconvnendaiions for Preliminary Investigations and Evaluation Jor <br /> Underground Tank Sites, Appendix A - Reports (Appendix A-Reports) dated 16 April 2004. <br /> Following are summaries for each of the numbered items listed in Part 6.6 of Appendix A- <br /> Reports and the section where that specific information may be found in the NFAR Request. <br /> 1. Site investigations were initiated in November 1996 when four underground storage <br /> tanks (USTs) were removed. Soil and groundwater investigations were conducted through <br /> June 2010. Groundwater monitoring has been conducted from November 1996 through <br /> fourth quarter 2010. See.S'ite lli.story. <br /> 2. The site surface is underlain by silty sand, sandy silt, clayey silt with interbedded sand, <br /> gravelly sand and clay to approximately 135 feet bsg. The fourth quarter 2010 static <br /> groundwater levels were measured at approximately 49 feet bsg. Monitoring data collected <br /> since 1996 indicate variable groundwater flow directions under gradients less than 0.01. <br /> During the past year of monitoring, groundwater flow directions in the UST area were <br /> predominantly southeastward under gradients of approximately 0.001 to 0.004. See <br /> Updated Site Conceptual Model, Site Physical and I mydrogeological Conditions. <br /> 3. A sensitive receptor survey was completed. Four water supply wells were identified <br /> within 'l:-mile radius of the site. No naturally occurring surface water bodies were <br /> identified within time survey area. See Updated.Site Conceptual Model, Sensitive Receptor <br /> Survey. <br /> 4970 Windplay Drive,1105 • EI Dorado Hills,CA 95762 • (916)939-2170 • FAX(916)939-2172 <br /> P.O.Box 5283 • Bakersfield.CA 93388 • (661)589-8389 • FAX(661)589-1456 <br />