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_ HORIZON ENVIRONMENTAL INC. <br /> c <br /> Specialists in Site Assessment,Remedial Testing, Design and Operation <br /> October 29, 2002 <br /> Mr. Joe Aldridge NOV 1 8 2002 <br /> Ultramar Inc. ENVIRONMENT HEALTH <br /> 685 West Third Street PERMIT/SERVICES <br /> Hanford, California 93230 <br /> Subject: Quarterly Groundwater Monitoring Report <br /> Third Quarter 2002 <br /> Beacon Station No. 12474 <br /> 3440 East Main Street, Stockton, California <br /> Mr. Aldridge: <br /> Horizon Environmental Inc. (Horizon) has prepared this report which documents third <br /> quarter 2002 groundwater monitoring at the .subject site located in San Joaquin County as <br /> shown on Figure 1. There are currently 12 groundwater monitoring wells (MW-1 through <br /> MW-12), seven vapor extraction wells (VW-1 through VW-7) and one air sparge well (AS- <br /> 1) associated with this site. The wells are located on site, except for monitoring wells MW-4 <br /> and MW-5, which are located on East Main Street and Broadway right-of-ways north of the <br /> site (Figure 2). <br /> Groundwater Monitoring <br /> Groundwater monitoring activities were conducted by Horizon on August 30, 2002 <br /> according to Horizon Field Methods and Procedures (Attachment A). Monitoring activities <br /> included measurement of static groundwater level, purging groundwater from the wells, <br /> collection of groundwater samples, and preparation and delivery of the samples to the <br /> analytical laboratory. <br /> The depth to groundwater was measured to the nearest 0.01 foot from the top-of-casing <br /> (TOC) in monitoring wells MW-1 through MW-12, vapor extraction wells VW-1 and VW- <br /> 4, and air sparge well AS-1. Vapor extraction wells VW-2, VW-3 and VW-5 through VW-7 <br /> were dry. The physical parameters, conductivity, pH and temperature were monitored with <br /> field instrumentation during the purging process. The visual characteristics of turbidity, the <br /> presence of free product or sheen, and the obvious olfactory characteristics of the <br /> groundwater were also noted during the purging process. Field groundwater monitoring <br /> well purge data are included on Horizon Monitoring Well Data sheets (Attachment B). <br /> Groundwater samples were collected from groundwater monitoring wells MWA through <br /> . MW-12, vapor extraction wells VW-1 and VW-4, and air sparge well AS-1. The samples <br /> were submitted, under chain-of-custody documentation, to Kiff Analytical LLC (Kiff), a <br /> 5011 Golden Foothill Parkway, Suite 7 • EI Dorado Hills, CA 95762 . (916) 939-2170 • FAX (916) 939-2172 <br /> P.O. Box 5283 41 Bakersfield, CA 93388 • (661) 589-8389 • FAX (661) 589-1456 <br />