SITE INFORMATION AND CORRESPONDENCE

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INFORMATION SHEET • • - 11 - MUSCO FAMILY OLIVE COMPANY AND THE STUDLEY COMPANY WASTEWATER TREATMENT AND LAND DISPOSAL FACILITY SAN JOAQUIN COUNTY screened in two zones, an unconfined(water table) and a confined zone. Further study is required to define the subsurface conditions. • The report recommends the use of Well MW-2 as a background well. Staff believe the excessively high concentrations observed in the well are likely due to an unknown source or other unknown factor. Additional investigation of the groundwater conditions at Well MW-2 is warranted. • The report describes similar concentrations in samples from Wells W-2 and MW-1 and suggests the data as a proof of no groundwater impact. Review of the Stiff diagrams for the wells on Plate 5 reveals an almost identical shape. However, staff believe the similarity may be a result of both wells defining the background groundwater conditions. Kleinfelder's statement that Well W-2 is the furthest downgradient well doesn't take into consideration the topography and natural drainage configuration. Staff believe if better definition of the groundwater elevation contours were available, groundwater in the area of Well W-2 might be flowing to the east or southeast toward the natural drainage, making the well upgradient of source areas (assuming the Class II ponds are not leaking). If that is the case, Well W-2 may be located in an area upgradient of all land application areas. Kleinfelder recommended the following additional investigations: • Research of published databases for groundwater quality in the near vicinity of the site. The research would focus on Sections 33 and 34 and other sections in proximity and with similar depositional environments. Staff believe the research might be interesting but remain cautious about using data from other locations and depth zones that might not be appropriate. Using data from off-site wells that screen deeper aquifers will not produce data that is representative of on-site conditions. The area's heterogeneous nature of the geologic deposits further limit the use of off-site data. Kleinfelder's report notes that shallow groundwater in the Upper Tulare Formation is of poorer quality than the deeper groundwater zone; considering this reported variation of water quality with depth, use of deep wells may add more uncertainty to the problem of defining background groundwater quality. • Conduct a limited physical search in neighboring areas for groundwater wells and information on the water quality. Staff believe the research could be interesting with the caveats described above. If off- site wells will be investigated, it is important to include all the available data, staff note that the on- site well was not included in the RWD nor in Kleinfelder's evaluation of regional wells; nor was the Harpainter well that is located adjacent to the application areas and irrigation checks. Staff are concerned that selective use of the available data will result in inaccurate conclusions on the region's water quality. • Limited geological mapping of the railroad cuts and other exposed structural features. Staff believe this could yield useful information but it should build upon the work published in professional papers. • Kleinfelder recommends preparation of Stiff diagrams to further characterize groundwater quality. Staff agree this action could provide useful information. However, additional wells are needed to better characterize the groundwater quality and hydrogeology of the area. Additional characterization is required to determine if a water table zone exists in the northern area of the site and to allow monitoring of groundwater upgradient and downgradient of the 84-Mgal storage pond. Effluent Limitations