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• Memorandum• <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION <br /> 3443 Routier Road Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS: 8-495-5600 <br /> TO: Gary Reents FROM: John J. Tomko <br /> Senior Engine- Area Engineer <br /> DATE: 24 February 1989 SIGNATURE: <br /> SUBJECT: MARLEY - PHASE IV INTERIM RESULTS <br /> The Hargis & Associates (H&A) report entitled "Quarterly Ground Water Monitoring <br /> and Interim Results of Phase IV Ground Water Assessment, Marley Cooling Tower <br /> Company, Stockton, California, December 1988" has been reviewed . The report <br /> presents the analytical results of the December 1988 sampling of 63 monitoring <br /> wells (including 15 newly installed wells) , a summary of the Phase IV ground water <br /> investigation conducted from September through November 1988, and an additional <br /> phase of monitoring well construction to delineate the extent of the chromium <br /> plume (scheduled for commencement on 6 March 1989) . Specific comments on this <br /> report follows: <br /> Phase IV Ground Water Investigation: <br /> 1. Nine (9) exploratory boreholes (2x - 15x, 250' = TD) <br /> A. Borehole 7-x continuously cored to 250 feet and drilled to 455 feet. <br /> B. All boreholes logged from drill cuttings and geophysical techniques <br /> including caliper, natural gamma, SP, point resistance, and 6-foot lateral <br /> ER. <br /> C. Very good correlation attained between borehole 7-x and point resistance <br /> and ER logs. <br /> 2. Fifteen (15) monitoring wells <br /> A. One (1) shallow, MW-400, 80' = TD <br /> B. Twelve (12) intermediate, MW-410 and 420 to 430, 105' to 195' = TO <br /> C. Two (2) deep, MW-460 and 461, 220' and 200' = TO <br /> D. An exploratory boring is adjacent to every intermediate and deep well . <br /> E. Construction techniques, and well installation and purging procedures, <br /> appear adequate to obtain representative aquifer samples. <br /> F. All monitoring wells were equipped with dedicated pumps. <br />