Laserfiche WebLink
California Regional Water Quality Control Board Ell <br /> Central Valley Region >� <br /> Robert Schneider Chair <br /> Alan C.Lloyd Ph.D. Sacramento Main Office Arnold Scbwarzenegger <br /> tern <br /> Secretary for Inet Address: http://www.swreb.ca.gov/rwgcb5 Governor <br /> 11020 Sun Center Drive#200 Rancho Cordova,CA 95670-6114 <br /> Environmental Phone(916)464-3291 Fax(916)464-4797 f�1 f�� <br /> Protection - IO�II(IL'-} <br /> 15 June 2005 JUN 7005 <br /> ENVIRONMENT HEALTH <br /> Mr. Mike Lescisin PERMIT/SERVICES <br /> Diamond Walnut Growers Inc. <br /> 1050 South Diamond Street <br /> Stockton, California 95201 <br /> MEETING SUMMARY, DIAMOND WALNUT GROWERS, STOCKTON PLANT RELEASE SITE, <br /> 1050 SOU7W DL9MOND STREET, STOCKTON, SAN JOA QUIN COUNTY <br /> Diamond Walnut Growers, Inc. (DWG) is conducting cleanup at its Stockton Plant at 1050 South <br /> Diamond Street in San Joaquin County(site)because of hexavalent chromium discovered in soil and <br /> groundwater beneath its cooling tower. The release of hexavalent chromium polluted groundwater and <br /> impaired its beneficial use. Central Valley Regional Water Quality Control Board (Regional Board) <br /> staff visited the Stockton Plant on 7 June 2005 to meet with DWG managers and discuss plant <br /> operations and maintenance. The following items were discussed at our meeting. <br /> 1. Recent groundwater monitoring shows that other pollutants in addition to hexavalent chromium <br /> are present. We discussed possible sources for the chloroform found in groundwater and <br /> developed a pollution prevention strategy to prevent further degradation of groundwater with this <br /> pollutant. DWG has agreed to complete a work plan that provides for sealing the floor drains and <br /> the subsurface sump contained in and near the cleaning plan to prevent chorine infiltration. In <br /> addition, there are chemical strategies such as sodium thiosulfate to neutralize chlorine and reduce <br /> chloroform formation. However even if chemical strategies are used, DWG must not allow any <br /> chemicals used on site to come into direct contact with surface soil thus allowing a pathway of <br /> migration to groundwater. Thus, sealing site-wide floor drains and sumps should be a matter of <br /> routine maintenance. <br /> 2. The source of the tetrachloroethylene (PCE) and aluminum pollution in groundwater beneath the <br /> site remains unknown. Regional Board staff will send out letters of inquiry to local businesses. <br /> 3. The 21 January 2005 Bench Scale Treatability Study for Reducing Hexavalent Chromium <br /> (Treatability Study) submitted by ATC Associates Inc. (ATC) on behalf of DWG suggests that <br /> additional bench scale testing is necessary. During our meeting we discussed the possibility of <br /> groundwater extraction with subsequent discharge in to the sanitary sewer and, in our 9 June <br /> e-mail we referred you to Mr. Richard Stiffler with the City of Stockton Municipal Utilities <br /> Department (Stockton MUD) to further explore this option. We agreed to postpone additional <br /> bench scale tests until DWG evaluates the feasibility of groundwater extraction and discharge to <br /> the sanitary sewer. <br /> California Environmental Protection Agency <br /> 0 Recycled Paper <br />