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Board California Regrbnal Water Quality Control Central Valley Region Robert Schneider,Chair Winston H.Hickox Gray Davis Secretaryfor Sacramento Main Office Governor Environmental Internet Address: http,.//w .sweb.ca.gov/— gcb5 ON Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 y Phone(916)255-3000•FAX(916)255-3164 '10 ?J J1 12 April 2002 = w N F Mr. Mike Lecision Diamond Walnut Growers Inc. dba Diamond of California 1050 South Diamond Street Stockton, California 95201 REVIEW OF MONITORING REPORT AND SUBSURFACE INVESTIGATION RESULTS, DIAMOND WALNUT GROWERS, STOCKTON PLANT, SAN JOAQUIN COUNTY We have reviewed the 19 December 2001 Fourth Quarter 2001 Monitoring Report(QMR4), the 25 February 2002 First Quarter 2002 Monitoring Report(QMR1) and the 6 February 2002 Subsurface Investigation (SI) submitted by ATC Associates Inc. (ATC), on behalf of Diamond Walnut Growers Inc. (DWG) for its Stockton Plant. During the 24 October 2001 and the 16 January 2002 sampling events reported in the QMRs, monitoring well MW-3 contained 8,800 µg/1 and 6,600 µg/1 of hexavalent chromium, respectively. We have the following comments on these documents. 1. The QMR1 contains tabulated results for sampling on 16 January 2002. However, the text is the same as that in QMR4. 2. QMR4 contains analytical results for samples collected from the Stockton City supply wells WP-1, WP-2 and WP-3. The Stockton City supply well WP-4 was not sampled. In relation to MW-3, WP-2 and 4 are generally sidegradient, WP-3 is upgradient and WP-1 is downgradient. During the 24 October 2001 sampling event, WP-I contained 4.4 µg/1 of hexavalent chromium. This concentration is not cause for immediate concern. However, DWG must arrange to annually sample supply well WP-1 during the first quarter monitoring event. Routine sampling of WP-2, 3 and 4 are not necessary at this time. 3. The QMR says, "The water sample collected from MW-3 contained relatively high levels of sodium (130 mg/1), calcium (1,300 mg/1), and chloride (3,000 mg/1)." Sodium has a suggested no-adverse-response level (SNARL) of 2 mg/l, which is for toxicity other than cancer risk. Chloride has a secondary Maximum Contaminant Level (MCL) of 250 mg/l. In California Environmental Protection Agency 0 Recycled Paper The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://w .swreb.ca.gov/mgcb5