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Closure Report 4 Golden Grain Manteca Bean Facility,299 Moffat Boulevard,Manteca,California July 16,19% 1 This work was performed according to the Final Remedial Plan and Addendum to the Final Remedial ' Plan that were approved by SJCPHS and the RWQCB Table 2 presents a summary of the well construction details and table 3 summarizes the analytical results of the soil samples collected and analyzed from the site Historic groundwater elevation data are summarized in table 4 and historic groundwater analytical results are summarized In table 5 The ' results of the Initial site assessment work are presented in the following two subsections to provide the baseline site conditions which existed prior to site remediation I 21 Geology/Hydrogeology ' Details of the subsurface geology and hydrogeology have been evaluated by preparing three geologic cross-sections A cross section location map (figure 3) shows the location of cross-section ' A-A' (figure 4), B-B' (figure 5), and C-C'(figure 8) A view of the subsurface geology from south to north is Illustrated by cross-section A-A', from west to the east by cross section B-13', and from the northeast to southwest by cross-section C-C' Soil type from the boring logs (appendix B) and the j N analytical results (table 3) of the soil samples collected dunng the installation of the site wells were used to prepare the cross-sections Soil type data from the recent soil boring program are included ' on the cross-sections for completeness and as part of the discussion of current site conditions presented in section 4 0 As illustrated on the cross-sections, a surface zone of dark-brown, silty, well-graded sand was encountered from surface grade to approximately 8 feet below surface grade (bsg) A light brown, coarser sand unit with thin layers of sandy silt was encountered below the dark brown sand to approximately 25 feet bsg A sandy clay unit about 4 feet thick was observed at approximately 25 feet bsg in some of the borings Beneath the sandy clay, a light brown,well-graded sand exists to at least 48 feet bsg, where a clay unit was encountered in the bonngs for wells MWA 0, MW-12, MW-13, and MW-14 Water level data collected at the site prior to the initiation of groundwater extraction indicated that groundwater flow was to the north at a gradient of less than 0 001 foot per foot (ft/ft) (figure 7) Hydrographs prepared using the historic groundwater level data (table 4) are included in appendix C Review of the hydrographs indicate that groundwater at the site is seasonally influenced and can fluctuate up to 8 feet Results of the aquifer test performed on the extraction well in December 4990 • provided an average transmissivity value of 8,100 gallons per day per foot and an average storativity 42020213 CR FLUOR DANIEL GTI