ARCHIVED REPORTS_RPT OF WASTE DISCHARGE FOR WASTEWATER DISPERSAL 2011

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Diamond Pet Food Processors of Ripon,LLC June 30,2011 Report of Waste Discharge Page 10 of 17 corner of the site adjacent to the Stanislaus River and groundwater samples likely are composed mainly of river water. The small size of their Stiff patterns (relative to most other wells) indicates that this water is less mineralized than that in other wells. River water is characterized by increasing relative percentages of magnesium+calcium and bicarbonate while mill effluent has been characterized by increasing relative percentages of sodium and chloride+sulfate.$ The patterns illustrate that the best groundwater quality is in the southeast part of the site and the most degraded groundwater quality is in the northeastern part of the site. As with analysis of groundwater quality contour maps, the poorest water quality in the northeast can be attributed to the concentration of constituents from evapotranspiration by the eucalyptus trees in this area.9 TREND ANALYSES For the second-half 2010 monitoring report, Mann-Kendall trend analysis was perform for all analytes in all wells. Figure 17 shows a summary of the trend analyses. Trend analyses for TDS show more improvements in water quality in the southeastern part of the site, reflecting application of the higher quality surface or groundwater to the east percolation field. The trend analyses also show more degradation of groundwater quality in the northeastern part of the site, reflecting concentration of constituents from evapotranspiration by the eucalyptus trees,10 and in the southwestern part of the site from the inflow of high TDS water from the City of Ripon's MWWTF. PREVIOUS CORRECTIVE ACTION In order to meet the WQPS adopted by the CVRWQCB for the site (Table 3), Diamond's predecessor,Neenah Paper, chose to import low TDS water from the South San Joaquin Irrigation District(SSJID) as the preferred corrective action method for reducing TDS levels in Plant effluent water and groundwater beneath the site.11,12 The water was provided by the City of Ripon and piped from their holding pond located on the north side of their MWWTF ponds. Groundwater-quality modeling predicted that the application of low (<150 mg/L) TDS water in the east percolation field would improve (lower) TDS levels by 100 to 500 mg/L, depending on the location in the subsurface, over a five year time period. 8 L&A,November 17,2008,Five-Year Water Quality Review Report. 9 Ibid.P. 8 io L&A,November 17,2008,Five-Year Water Quality Review Report. u L&A,June 15,2005,Amended Report of Waste Discharge For Disposal Of Plant Effluent Water. 12 L&A,March 31,2006,Addendum To Amended Report of Waste Discharge For Disposal Of Plant Effluent Water. 010107.00, Task I Lawrence&Associates w:Iclientsl diamond pet foods1010107.00-ripon rowdldiamondpet_rowdjune2011_draft.docx