ARCHIVED REPORTS_SECOND HALF AND ANNUAL 2010 GW MONITORING RPT

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Diamond Pet Food Processors of Ripon California LLC January 28,2011 Combined Annual and Fourth-Quarter 2010 Gronndwater Monitoring Report Page 5 of 8 was away from the mounds, then generally towards the northeast. The magnitude of the gradient ranged between 0.0028 and 0.00156 ft/ft (Figure 8). Mounding within the intermediate aquifer was present in approximately the same general areas where mounding was observed in both the semiperched and upper aquifers. The direction of the groundwater gradient was away from the mounds, then generally towards the north. The magnitude of the gradient ranged between 0.0018 and 0.0031 (Figure 9). The highest onsite SC in the semiperched aquifer was measured in wells located in and adjacent to the eucalyptus grove in the northeast quadrant of the site; in wells located around ASB-1, and wells located along the western property boundary. The area of lowest SC was in the southeastern comer of the site along the Stanislaus River in well OB-16 (111 µmhos/cm). SC levels in wells located along the Stanislaus River and in the north central portion of the site were in compliance with the WQPS of 1,242 µmhos/em (Figure 10). The highest SC levels in the upper aquifer were in wells M-11-A and TH-4 (1,310 and 1,281 µmhos/cm, respectively). The area of lowest SC was in the northwestern corner of the site in well TH-7 (76 µmhos/cm). All wells screened in the upper aquifer were in compliance with the WQPS of 1,580 µmhos/cm (Figure 11). The highest SC level in the intermediate aquifer was in the northeast quadrant of the site in TH- 3 (1,978 µmhos/cm). The area of lowest conductivity was in the northwest quadrant of the site in well M-11-C (136 µmhos/cm; Figure 12). The areas of highest and lowest total dissolved solids (TDS) concentrations in the semiperched (Figure 13), upper(Figure 14), and intermediate aquifers (Figure 15) were approximately the same as the areas of highest and lowest field conductivity values in the semiperched (Figure 10), upper(Figure 11), and intermediate aquifer(Figure 12). Conclusions Infiltration of plant process water is suspected to be responsible for the elevated SC levels measured in the semiperched, upper, and intermediate aquifer over most of the site. The elevated TDS levels in the semiperched aquifer in the northeastern quadrant of the site, however, which have been up to three times higher than effluent TDS levels, are likely caused by the eucalyptus trees' concentrating effect on TDS.3 The elevated TDS levels observed along the western portion of the site, particularly in the southwest comer of the site, probably reflect the infiltration of higher TDS water originating at the City of Ripon's MWWTF encroaching onto the DP site. Recommendations DP should apply either low TDS surface water or groundwater to the east percolation field during the 2011 irrigation season in order to create a hydrologic barrier between ASB-2 and the production wells. Removal of the eucalyptus grove, in order to eliminate their concentrating effect on groundwater TDS levels, should be considered. G.S.Jorgensen,Kenneth H. Solomon,and V.Cervinka,March 1993,Agroforeshy Smemsfor On-Farm Drain Peter Management. 10107.01 Task 2 Lawrence d Associates R-I CLIENTSIDiantnnd Pet Foods1010107.01-Grouadbvater Monitoring)Grotutd,vater hloaitaring1201012nd Haff 2l/101amntal-2,,d Half 2010 repomdoc