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ADDENDUM LETTER -3- <br /> ADDITIONAL HYDROGEOLOGICAL INVESTIGATION WORKPLAN <br /> MUSCO FAMILY OLIVE COMPANY <br /> TRACY, CALIFORNIA <br /> Cross-Section E to E' <br /> Cross-section E to E'contains new shallow groundwater monitoring wells MW-14, MW-15, and <br /> MW-16. These wells plus Exploratory Boring TW-2 and deep monitoring well MW-2 show a substantial <br /> thickness of clay in the upper interval from ground surface down to approximately 30 feet. MW-15 is the <br /> only exception, with the interval in this well containing sandy interbeds. The high TDS in the deep <br /> groundwater encountered in MW-2 is a totally different type, perhaps of marine origin. MW-3 was <br /> previously discussed and Exploratory Boring GT-3 was dry. <br /> GROUNDWATER QUALITY <br /> A review of Stiff Diagrams prepared for each well, the 84-MGAL Pond, the seepage, and the spring <br /> indicate that there are several different water types. None of the diagrams looks similar to the 84-MGAL <br /> Pond. It couldn't be determined at this time whether wastewater migration has impacted groundwater. <br /> Some data results are-questionable and were not used. <br /> RWOCB PROPOSAL <br /> Due to the heterogeneity in the subsurface and the lack of adequate site characterization of the <br /> subsurface stratigraphic framework, it is recommended the thirteen deep (at least 250 feet deep) <br /> exploratory borings be drilled with mud rotary and geophysically logged at the locations shown on the <br /> attached map. The logs need to be correlated to more accurately define the hydrogeologic framework. <br /> The information obtained would be used to determine which existing wells appear to be located properly <br /> for detection monitoring and where additional wells should be considered. <br /> It is also recommended that a tracer be added to the 84-MGAL Pond to track fluid migration in the <br /> subsurface from either the pond or spray fields. <br /> JKD:c:Uny documentsWUSCO\Wrk Plan <br />