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1117 Lone Palm Ave , Suite 6 <br /> Modesto, California 95351 <br /> www atc-enviro corn <br /> 209 579 2221 <br /> Fax 209 579 2225 <br /> A g S 0 C t A T $ 8 I N C <br /> November 1, 2002 <br /> 54 62583 0001 <br />' Ms Mary Serra <br /> Regional Water Quality Control Board <br /> 3443 Routier Road, Suite A <br />' Sacramento, CA 95827 <br /> Subject Additional Subsurface Investigation of Diamond Walnut Growers, 1050 South <br /> Diamond Street, Stockton, California <br /> Dear Ms Serra <br />' ATC Associates Inc has completed a Subsurface Investigation of the above referenced site The <br /> investigation was performed to evaluate the horizontal and vertical extent of groundwater <br /> impacted with hexavalent chromium at the site Activities included installing five additional <br /> wells in the shallow water-bearing zone, advancing two cone penetrometer test borings and <br /> collecting groundwater samples from the deeper water-bearing zone, and surveying, measuring <br /> depth to water, and sampling all the monitoring wells on site Groundwater analytical results <br /> indicated that relatively low concentrations of hexavalent chromium were detected in four of the <br /> five new wells Hexavalent chromium was also detected in the groundwater samples collected <br />' from the deeper water-bearing zone The groundwater flow direction and magnitude were found <br /> to be consistent with historical events The attached report summarizes our activities and <br /> findings in detail and recommendations for the installation of a deep well at the site <br /> 1 If you should have any questions or comments regarding this report or our recommendations, please <br /> feel free to call us at your convenience at(209) 579-2221 <br /> 1 Respectfully submitted, <br /> ATC Associates Inc <br /> 1hn Sellman w� i` !' - 4 <br /> Staff Geologist <br /> 1 <br /> �— Yn <br /> f� Fa <br /> w <br /> J e Hornsey, P E <br /> CA Registered Civil Engineer No 47410 rH <br /> cc Mr Mike Lescisin, Diamond Walnut Growers <br />' Ms Margaret Lagono, San Joaquin County Environmental Health Department <br /> 1 ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />