Laserfiche WebLink
1117 Lone Palm Avenue, Suite B <br /> Modesto, CA 95351 <br /> C-V-WATC <br /> www.atc-enviro.com <br /> 209.579.2221 <br /> Fax 209.579.2225 <br /> A S S O C I A T E S I N C I / <br /> �u V kFU <br /> June 25, 2003 <br /> JUN 2 6 2003 <br /> Ms. Mary Serra HEALTH <br /> HEAL <br /> California Regional Water Quality Control Board PERMIT/SERVICES ENVIRONMEMENT NT EAL <br /> Central Valley Region <br /> 3443 Routicr Road, Suite A <br /> Sacramento, CA 95827-3003 <br /> Subject: Cleanup Plan/Conceptual Remediation Design for Diamond Walnut Growers Stockton <br /> Plant <br /> Dear Ms. Sena: <br /> Of behalf of Diamond Walnut Growers, Inc. (DWG), ATC Associates Inc. (ATC) has developed a <br /> cleanup plan including a Conceptual Remediation Design (CRD) for the subject site located at 1050 <br /> South Diamond Street in Stockton, California. This CRD was prepared in response to your request <br /> contained in your letter to Mr. Mike Lescisin of DWG, dated June 2, 2003. The CRD was prepared to <br /> address elevated hexavalent chromium concentrations in groundwater beneath the site. <br /> Background Information <br /> The DWG plant is located northeast of the intersection of Charter Way and South Diamond Street in <br /> Stockton, California(Figure 1).According to DWG,the facility has been operating as a walnut processing <br /> plant since the 1950s. Five underground concrete vaults were located north and east of the main <br /> processing building and formerly contained refrigerants used in the plant cooling systems (Figure 2). <br /> Vaults 1, 5, and 6, installed between 1974 and 1976, were concrete and historically contained propylene <br /> glycol. <br /> Vaults 1 and 5 had 1,200-gallon capacities and Vault 6 had a 500-gallon capacity. These vaults were <br /> located along the eastern side of the property adjacent to large walnut storage bins (Figure 2). Vaults 7 <br /> and 8 were constricted with poured concrete and lined with fiberglass and asphalt, and were used to store <br /> calcium chloride and sodium dichromate chill water solution. Vaults 7 and 8 had 3,000 and 5,000-gallon <br /> capacities,respectively, and were located against the north wall of the processing building(Figure 2). All <br /> of the vaults were taken out of service and cleaned in June 1990(Weiss Associates,April 1991). <br /> Weiss Associates (WA) of Emeryville, Califomia conducted several phases of subsurface soil and <br /> groundwater investigation activities at the subject property since December 1988. In January 1991, three <br /> groundwater monitoring wells were constructed to monitor the first encountered saturated zone, which <br /> was encountered at a depth of approximately 71 feet below grade in each boring. The wells were screened <br /> at a minimum of 56 feet and at a maximum of 89 feet below grade surface (bgs). On January 31, 1991, <br /> Weiss Associates (WA) personnel collected groundwater samples from each well. Samples collected <br /> from monitoring wells MW-1 and MW-2 (adjacent to Vaults 1 and 6, respectively) were analyzed by <br /> GC/FID for ethylene and propylene glycol. The water sample collected from MW-3, adjacent to Vault 8, <br /> was analyzed for total soluble chromium, sodium and calcium(EPA method 6010), hexavalent chromium <br /> (EPA method 7196), and chlorides (EPA method 325.2). All constituents were detected below the <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />