ARCHIVED REPORTS_2013 ANNUAL REPORT

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Nest16 USA, Inc., Ripon, California March 26, 2014 2013 Annual Report 2.2 WATER LEVEL MONITORING Table 4 provides the list of wells and a summary of the quarterly depth-to-water measurements gauged on January 7, April 8, July 8, and October 7, 2013. The 2013 water level elevation data for each aquifer are discussed below. ECM used the groundwater elevation data collected during each quarter from wells screened in the three aquifers to develop a series of 12 potentiometric surface maps (Figure 3-1 through Figure 5-4). During development of the potentiometric surface maps, ECM evaluated the temporal water level trends and differences between adjacent wells. If the water level elevations between two co-located wells screened in different units of the same aquifer (e.g., B unit versus A unit) differed by more than 0.5 feet, one of the wells was excluded from the contouring process based on a comparison with the data for surrounding wells. In addition, ECM did not use wells that had water level elevations outside of regional and historical trends for contouring. The wells with water levels that were not used for contouring varied by quarter and are identified on their respective potentiometric surface maps (Figure 3-1 through Figure 5- 4) and in the table below. Aquifer Quarter Well ID Figure First M-9A, TH-7 Figure 3-1 Upper Second M-9A, W-7 Figure 3-2 Third M-9A, W-7 Figure 3-3 Fourth M-913, W-7 Figure 3-4 First TH-10, MW-10 Figure 4-1 Intermediate Second MW-10 Figure 4-2 Third M-39C, MW-10 Figure 4-3 Fourth MW-9, MW-10 Figure 4-4 First M-27D, M-38D, M-34D1 Figure 5-1 Lower Second MW-5 Figure 5-2 Third MW-10 Figure 5-3 Fourth MW-10 Figure 5-4 Note:Water levels for these wells were not used during groundwater elevation contouring The following subsections summarize ECM's interpretation of the potentiometric surface maps and discuss the influence of river stage, recharge basins, and pumping on groundwater levels and flow patterns. 2.2.1 GROUNDWATER FLOW DIRECTION During all four quarters of 2013, the predominant groundwater flow direction in the Upper Aquifer (Figure 3-1 through Figure 3-4) and Intermediate Aquifer (Figure 4-1 through Figure 4-4) was north-northwesterly, likely related to the recharge effects of the Stanislaus River. Groundwater flow in the southern portion of the Study Area and north of the Stanislaus River is also influenced by the City of Ripon wastewater treatment plant (WWTP) lagoons/recharge pond and Diamond Pet percolation fields. When active, these recharge features create groundwater mounding and elongated radial groundwater flow in the Upper and Intermediate Aquifers. In addition, groundwater flow is locally influenced by pumping wells dependent on aquifer penetration interval 4