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HORIZON ENVIRONMENTAL INC. <br />Specialists in Site Assessment, Remedial Testing, Design and Operation <br />May 9, 2013 <br />Mr. Harlin Knoll <br />San Joaquin County Environmental Health Department <br />1868 East Hazelton Avenue <br />Stockton, California 95205-6232 <br />Subject: Additional Groundwater and Soil Gas Investigations, NFAR Request and <br />Well Destruction Work Plan <br />Abdelwahed Facility, Ultramar No. 13792 <br />2255 South Airport Way, Stockton California <br />Mr. Knoll: <br />On behalf of Ultramar Inc. (Ultramar), Horizon Environmental Inc. (Horizon) has prepared <br />this report documenting the results of additional groundwater and soil gas investigations at the <br />subject site located in San Joaquin County, California. This report also includes a No Further <br />Action Required (NFAR) Request and a work plan for well destructions. <br />The additional groundwater and soil gas investigations were recommended by Horizon in the <br />fourth quarter 2011 Groundwater Monitoring / Remediation Status Report dated 12 January <br />2012. Horizon proposed the destruction of monitoring well MW -1, installation of a dual- <br />phase extraction (DPE) well, and soil gas investigation in the Work Plan for DPE Well <br />Installation and Soil Gas Investigation (Work Plan) dated 5 May 2012. The San Joaquin <br />County Environmental Health Department (EHD) approved the work plan in a letter dated 14 <br />May 2012. The EHD requested that the results of the investigations be included in a case <br />closure summary in addition to a work plan for well destructions in an e-mail dated 25 <br />January 2013. The EHD correspondence is contained in Attachment A. <br />SITE DESCRIPTION <br />Site description and historical background details are contained in Attachment B. The site is <br />located in San Joaquin County, California as shown on Figure 1. Current site features are <br />shown on Figure 2. Currently, there are eleven groundwater monitoring wells (MW -2 through <br />J� MW -4 and MW -6 through MW -13), five vapor extraction wells (VW -I through VW -5) and <br />two sparge wells (SW -I and SW -2) associated with the site as shown on Figure 3. Wells <br />y117 MW -6, MW -7, MW -10, MW -1 I and MW -12 are located off site to the east and southeast. <br />Monitoring wells MW -1 and MW -5 were destroyed in July 2012 and March 2008, <br />respectively. <br />Groundwater monitoring has been conducted since July 2003 with the most recent in <br />December 2012 (fourth quarter 2012). Depth to groundwater was approximately 31 feet <br />below surface grade (bsg). The groundwater flow direction was eastward under a gradient of <br />approximately 0.001 as shown on Figure 3. An analytical summary for fourth quarter 2012 is <br />4970 Windplay Drive, #C5 - FI Dorado Hills. CA 95762 - (916) 939-2170 - FAX (916) 939-2172 <br />PO. Box 5283 - Bakersfield, CA 93388 - (661) 589-8389 - FAX (661) 589-1456 <br />