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EvNuxv O. Bxawx Jx. ,r n,• Mn.,Haw Rvvniovaz Water Boards Central Valley Regional Water Quality Control Board MAY 2 1 2013 22 May 2013 ENViPONMENTAL HEALTH PERM11T,fSERVICES Mark Schell Jim Groff Diamond Pet Food Processors of Ripon, LLC Ripon Cogeneration, LLC P.O. Box 156 944 S. Stockton Ave Meta, MO 65058 Ripon, CA 95366 APPROVAL OF GROUNDWATER LIMITATIONS COMPLIANCE ASSESSMENT PLAN, DIAMOND PET FOOD PROCESSORS OF RIPON, LLC. AND RIPON COGENERATION, LLC., SAN JOAQUIN COUNTY Central Valley Regional Water Quality Control Board staff has reviewed the 4 March 2013 Groundwater Limitations Compliance Assessment Plan (Assessment Plan) prepared by Lawrence &Associates for Diamond Pet Food Ripon Facility. Based on the review, the plan is generally acceptable. The Assessment Plan is required by Waste Discharge Requirements (WDRs) Order R5-2012-0105, Provision H.1.a., as follows: By 1 January 2013, the Discharger shall submit a Groundwater Limitations Compliance Assessment Plan. The plan shall describe and justify the statistical methods used to compliance for the constituents listed in the Monitoring and Reporting Program. Compliance shall be determined annually based on an intra-well statistical analysis prescribed in Title 27, section 20415(e)(10) to compare monitoring data collected at each compliance well. The Assessment Plan proposes to apply intra-well statistical analysis and evaluate compliance with groundwater limitations using the Mann-Kendall test, which is a nonparametric test for trend detection. The Assessment Plan states that the Mann-Kendall can identify whether data for a single parameter in a single well exhibit an increasing or decreasing trend with time; the Mann- Kendall test is robust with respect to the data distribution, non-detect values, and outliers, and would be appropriate for this site. The WDRs prohibit groundwater degradation statistically greater than current groundwater quality. To determine the baseline for the current groundwater condition, the Assessment Plan proposes to use groundwater data since April 2009 for trend analysis, because the previous discharger paper mill ceased discharge at that time. Based on the review, staff concurs with the proposed statistical method and the time baseline to set the current groundwater quality, and approves the Assessment Plan. KARL E. LONOLEY SCD, P.E., CHAIR I PAMELA C. CnEEDON P.E., BCEE, E%ECVTIVC orrsocn 11020 Sun Center Drlve#200,Rancho CoMoye,CA 95570 I www.waterbowdo.ca.gov/contralvalley �'j nFc.ciev rsren