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`./ <br /> KAPREALIAN ENGINEERING, INC. <br /> K E Consulting Engineers <br /> P. O. BOX 913 <br /> BENICIA,CA 94510 <br /> (415)676-9100 (707)746-6915 <br /> KEI-P86-084C <br /> November 4, 1988 <br /> Mobil Oil Corporation � � 4 <br /> P. O. Box 127 <br /> Richmond, CA 94807 <br /> Attention: Mr. Steve Pao <br /> Re: Work Plan <br /> Mobil SIS #10-NP4 <br /> 2375 Tracy Blvd. <br /> Tracy, California <br /> Dear Mr. Pao: <br /> The active Mobil gasoline station on the southwest corner of the <br /> intersection of Tracy Blvd. and Grantline Road in Tracy has been <br /> under investigation by KEI since mid-1986. Both soil and ground <br /> water contamination have been identified but the full extent of <br /> ground water contamination is not yet known. <br /> BACKGROUND <br /> Mobil Oil Corporation contracted Kaprealian Engineering, Inc. <br /> (KEI) to undertake an initial site investigation to determine if <br /> any subsurface contamination occurred from the service station <br /> operations. In August 1986, four underground storage tanks (two <br /> 10,000 gallon and one 5,000 gallon gasoline tank, and one waste <br /> oil tank) were removed from the site. Contaminated ground water <br /> in the tank pit was observed during the tank removal. on August <br /> 29, 1986, four monitoring wells were installed on the site. <br /> Ground water was encountered at approximately seven feet below <br /> grade during drilling. Analytical results showed no <br /> contamination in MW-1 or MW-2 , but detectable levels of <br /> contamination were present in MW-3 and MW-4 . In an attempt to <br /> further define the extent of contamination, four additional wells <br /> were installed on January 27, 1987 (MW-5, MW-6, MW-7, and MW-8) <br /> (Location Plan) . The wells have been monitored and analyzed on a <br /> periodic basis since their installation (Tables 1 & 2) . <br /> FIELD ACTIVITIES <br /> The wells have been monitored and sampled several times between <br /> late 1986 and October, 1988. During monitoring, the wells were <br /> checked for depth to water using an electronic sounder, odor, and <br /> visual presence of free product. After monitoring, the wells <br /> were purged with a surface pump and allowed to recover. <br />