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California Reghual Water Quality Co4trol Board <br /> Central Valley Region <br /> Robert Schneider,Chair . :. .: <br /> Winston H.Hickox Gray Davis <br /> Secrelary for Sacramento Main Office Governor <br /> Environmental Internet Address: http://wvnv.swrcb.ca.gov/-rwgcb5 <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3164 <br /> 25 June 2001 <br /> Mr. Mike Lecision <br /> Diamond Walnut Growers Inc. <br /> 1050 South Diamond Street <br /> Stockton, California 95201 <br /> REVIEW OF GROUNDWATER MONITORING REPORT,DIAMOND WALNUT <br /> GROWERS, STOCKTON PLANT, SAN JOAQUIN COUNTY <br /> We have reviewed the 31 May 2001 Second Quarter 2001Monitoring Report(QMR) submitted <br /> by ATC Associates Inc. (ATC), on behalf of Diamond Walnut Growers Inc. (DWG) for its <br /> Stockton Plant. This document contains the groundwater monitoring results for samples <br /> collected 16 April 2001. The QMR shows that groundwater beneath the site contains hexavalent <br /> chromium (Cr+6), with the highest concentration found in monitoring well MW-3 at 7,460 µg/l. <br /> Monitoring wells MW-1 and MW-2 contained 11.3 and 28.3 µg/1,respectively. We have the <br /> following comments on the QMR. <br /> 1. Table 2 of the QMR shows that DWG employed U.S. EPA Method 218.4 for Cr+6 analysis. <br /> However, the QMR attachment that includes the laboratory data sheets from Sequoia <br /> Analytical reports U.S. EPA Method 7196A with a detection limit of 5.0 µg/1. We request <br /> that DWG use U.S. EPA Method 7199 for Cr+6 analysis. U.S. EPA and California certified <br /> laboratories in our area are generally able to achieve a detection limit of about 2 µg/l for Cr+6 <br /> 2. In 1998, the Board adopted a Water Quality Control Plan,Fourth Edition,for the <br /> Sacramento and San Joaquin River Basins (Basin Plan). The Basin Plan designates <br /> beneficial uses and establishes water quality objectives to protect those uses. Groundwater <br /> beneath the DWG site has, among others, a beneficial use as an existing source of municipal <br /> and domestic supply. Therefore, human health-based criteria and guidelines are relevant to <br /> protect municipal and domestic supply beneficial uses. Published human health based <br /> criteria and guidelines for Cr+6 are summarized in A Compilation of Water Quality Goals <br /> (Compilation). The Basin Plan and the Compilation can be viewed via the intemet on the <br /> world-wide web at http://www.swrcb.ca.gov/rwgcb5/wq_goals. Based on the information <br /> in this publication, Cr+6 has a U.S. EPA Integrated Risk Information System (IRIS) reference <br /> dose as a drinking water level of 21 µg/1, a CAL-EPA Cancer Potency Factor as Drinking <br /> Water Levels (one-in-a-million cancer risk) of 0.18 µg/1, and a California Public Health Goal <br /> (PHG) of 0.2 µg/1 which is based on a one in a-million cancer risk level and derived from the <br /> assumption that the percentage of Cr+6 in total chromium(PHG of 2.5 µg/1)is 7.2 percent. <br /> California Environmental Protection Agency <br /> ed Recycled Paper <br /> The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of <br /> simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swmb.ca.gov/rwgcb5 <br />