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The additional investigation will include several components: • The construction of an additional upgradient monitoring well to provide better data on background groundwater quality and improved understanding of groundwater flow directions • The collection of samples from all the monitoring wells at the holding ponds, as well as from the ponds and from Sugar Cut Slough • The performance of TDS mass balance and water budget studies to assess the fate of the water entering the ponds and evaluate the impact of evaporation on TDS concentrations in the ponds This plan will describe the additional investigation. It will discuss the location and construction details of the additional monitoring well, and explain the procedures for developing, sampling, and surveying the well, as well as sampling the holding ponds and Sugar Cut Slough. It will also include a discussion of the water budget method, and a proposed approach for conducting the study. Data will be collected during the canning season from August 1 to October 31, 1994. Following approval of the plan, the new monitoring well will be constructed and the additional data collected. A report will then be prepared summarizing the results of this work, as well as the quarterly monitoring that has been conducted since 1992, and will indicate whether holding pond water appears to be infiltrating the groundwater system. Monitoring Well Installation The proposed location of the new monitoring well is shown on Figure 3. This well will be designated as HP-5 and will be located south of Arbor Avenue and sufficiently upgradient from the holding ponds to avoid any potential that the ponds may affect the groundwater quality or groundwater elevation in the well. Before drilling at this location, Underground Service Alert will be contacted to check for the possible presence of underground utilities. If necessary, an initial hole will be augered by hand to a depth of 5 feet to check for utilities. In addition, a well permit will be obtained from San Joaquin County. Drilling The borehole for HP-5 will be drilled by a continuous flight 11-inch-diameter hollow-stem auger. This method is appropriate because of the expected depth of the borehole (less than 35 feet); it does not require the addition of drilling fluids into the borehole; and it allows for the collection of relatively undisturbed soil samples for lithologic logging. The drill string consists of continuous flight edges welded to hollow drill pipe with a cutter head at the bottom. As the cutter head rotates and advances the hole, cuttings are lifted to the surface along the flights. SAC/SAC36357/041.WP5 4 8/94