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California P-gional Water Quality Cont,--)l Board Central Valley Region �y Karl E. Longley,SCD, P.E.,Chair '_ Linda S.AdamsArnold 11020 Sun Center Drive N200,Rancho Cordova_California 95670-6114 Schwarzenegger Secreiar for Phone(916)464-3291 •FAX(916)464-4641 Envtronmenra1Cirn�rrnor httpahv++++.watcrboards.ca.gov/centralvalleN � Protection D nE SVED 13 March 2009 MAR 1 6 2009 Mr. Tim Van Domelen EN'JIROWJIENT tfiEALTli Manager, Environmental Health, Safety, and Security pG°^n'TISFgV!CLS J. R. Simplot Company 16777 Howland Road Lathrop, CA 95333-0198 COMBINED ASSESSMENT REPORT— J.R. SIMPLOT COMPANY, 16777 HOWLAND ROAD, LATHROP, SAN JOAQUIN COUNTY The Central Valley Regional Water Quality Control Board (Regional Water Board) staff have received the Combined Assessment Report (Report), dated 3 February 2009, submitted on behalf of J. R. Simplot by AMEC Geomatrix, Inc. (AMEC). In the Report, AMEC describes the field activities, data collection, and results of soil and groundwater sampling conducted July through August 2008 in the area of the process water ponds at the J.R. Simplot facility. It is clear from the results of the Combined Assessment that releases of nitrate- and sulfate- impacted water from the northwest pond have occurred. These releases have affected groundwater across the property. Impacts from individual releases associated with the process water pond piping leak, the UN-32 tank release, the auto accident area, and the dilute ammonium sulfate solution release are generally within the footprint of the nitrate and sulfate plumes as depicted in several figures in the Report. It is not clear whether the process water ponds continue to leak and release sulfate and nitrate to the underlying groundwater. Further, it is not clear whether the groundwater extraction and treatment (GWET) system operated by Glenn Springs Holdings Inc. (GHSI) is hydraulically affecting migration of sulfates and nitrates (the GWET system has been in full operation since 23 November 2008, and should remain in full operation until cleanup is completed). Further clarification is needed, also, on whether AMEC is recommending remediation of the individual releases separate from the larger nitrate and sulfate plumes. We request that your Feasibility Study, due 15 April 2009, clarify these issues and address the specific comments below. 1 . We agree with J.R. Simplot that samples of soil collected at borings EB-AZ, EB-BA, and EB-BB, and water from well LP-7 are deemed to be representative of background concentrations. As noted in section 7.1 of the Report, however, the background concentration of ammonia as nitrogen in groundwater exceeds the Water Quality Protection Standard published in the Monitoring and Reporting Program (MRP) No. R5-2008-0838 (4.9 milligrams per liter). Thus the standard will need to be evaluated per the MRP. Please provide a rationale for the increase in ammonia and a statistical California Environmental Protection Agency