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KAPREALIAN ENGINEERING <br /> I N C O R P O R A T E D <br /> KEI-P89-1104 .QR6 <br /> February 1 , 1993 <br /> Unocal Corporation <br /> 2000 Crow Canyon Place, Suite 400 <br /> P.O. Box 5155 <br /> San Ramon, California 94583 <br /> Attention: Mr. Edward C. Ralston <br /> RE: Semi-Annual Report E C711 EVIE" 0 <br /> Unocal Service Station #5421 FEB 12 1993 <br /> 7303 Pacific Avenue <br /> Stockton , California ENVIRONMENTAL HEALTH <br /> PERMIT/60VI��b <br /> Dear Mr. Ralston: <br /> This report presents the results of the most recent period of <br /> monitoring and sampling of the monitoring wells at the referenced <br /> site by Kaprealian Engineering, Inc. (KEI) , per KEI ' s proposal <br /> (KEI--P89-1104 .P5) dated December 10, 1990, and as modified in KEI 's <br /> quarterly report (KEI-P89-1104 .QR4) dated February 3 , 1992 . The <br /> wells are currently monitored quarterly and sampled on a semi- <br /> annual basis. This report covers the monitoring and sampling work <br /> performed by KEI from September through December of 1992 . <br /> SITE DESCRIPTION AND BACKGROUND <br /> The subject site contains a Unocal service station facility. Two <br /> underground gasoline storage tanks, one waste oil tank, and the <br /> product piping were removed from the site in November of 1989 <br /> during tank replacement activities. The fuel tank pit and a <br /> portion of the product pipe trench were subsequently overexcavated <br /> in order to remove contaminated soil . A septic tank and leach <br /> field were removed from the site during July through October of <br /> 1992 . Four monitoring wells have been installed at the site. In <br /> addition, seven exploratory borings have been drilled at the site. <br /> A site description, detailed background information including a <br /> summary of all of the soil and ground water subsurface investiga- <br /> tion/remediation work conducted to date, site hydrogeologic <br /> conditions, and tables that summarize all of the soil and ground <br /> water sample analytical results are presented in KEI ' s quarterly <br /> report (KEI-P89-1104 .R9) dated December 17 , 1992 . <br /> RECENT FIELD ACTIVITIES <br /> The four monitoring wells (MW1 through MW4) were monitored two <br /> times and were sampled once during the semi-annual period. During <br /> monitoring, the wells were checked for depth to water and the <br /> 2401 Stanwell Drive Suite 400 <br /> Concord California 94520 <br /> Tel 510 602 5100 Fax 510 687 0002 <br />