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a <br /> Technical Summary & Report of 4TH Qtr Monitoring April 2, 1992 <br /> Diamond Walnut Growers, 1050 South Diamond Street, Stockton, CA W0564 i <br /> Groundwater samples were collected on December 18 after purging the monitoring wells and <br /> ' verifying the stabilization of pH, electrical conductivity (EC), and temperature Samples were <br /> collected from the City wells via the nearest sampling port <br /> 442 LaboratoaL Analysis <br /> ' Samples were submitted to Sequoia Analytical Laboratories, (Redwood City, CA) for analysis <br /> of ethylene glycol (by GC/FID), propylene glycol (by GC/FID), total chromium (EPA method <br /> ' 6010), and hexavalent chromium (EPA methal 7196) Laboratory results indicate that the <br /> samples collected from the monitoring wells contained total chromium and hexavalent chromium <br /> ' less than the California primary maximum contaminant level (MCL) for drinking water (.05 <br /> mg/f) with the exception of well MW-3. The sample from MW-1 contained nondetectable <br /> ' concentrations of total and hexavalent chromium The sample from MW-2 contained 0.025 <br /> milligrams per liter (mg/1) hexavalent chromium and 0.015 mg/f total chromium, this <br /> discrepancy is probably due to analytical variance (different detection limits were used for each <br /> analytical method). The sample from MW-3 contained 0 052 mg/P hexavalent chromium and <br /> ' 0 037 mg/Q total chromium, again, this discrepancy is likely due to analytical variance. The <br /> glycols were nondetectable in the samples collected from all of the monitoring wells No <br /> ' analytes were detected at or above the method detection limits in the samples collected from the <br /> City wells. These analytical results are summarized on Table 1. <br /> 4�3 History_ of Anal, ical Data for City Supply Wells <br /> The results of three sampIing events for the City wells WP-1, WP-2, and WP-3 for California <br /> Title 22 constituents were obtained for review. The dates of the sampling events were <br /> ` November 6, 1989, November 6, 1990, and October 20, 1991. The constituents of concern <br /> include total chromium, calcium, sodium, and chloride. The analytical results indicate that the <br /> constituents detected in the samples were generally below the California Primary MCL for total <br /> chromium and sodium, and below the EPA secondary standard for chlorides, no standard has <br /> been established for calcium to date However, the October 1991 analysis for well WP-2 <br /> R411792 SAY 5 <br />