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1 - -- GROUNDWATER QUALITY INVESTIGATION---- ---- --- - -- - -- — Work Plan for July through January, 1989 Southwest Hide Company Manteca , California June, 1988 TASK I I. Drill four (4) additional groundwater monitoring wells as shown on the accompanying aerial photo, Exhibit 1, page 8, as well numbers 8, 10, 12 and 13. These wells will be approximately thirty feet ( 30' ±) in depth, cased with two inch (2" ) diameter PVC, and constructed by the same procedures used for drilling wells 5, 6, 7 , 9 and 11. The details of the construction materials, procedures and logging are presented on page 2. 2. One deeper hole will be drilled at Groundwater Monitoring No. `h 8. The hole will be drilled to a depth of approximately 100 feet with continuous core samples taken to establish the stratigraphy of the upper aquifer(s) . Once drilled and logged, the bore hole wiII be sealed using a bentonite/cement slurry to fill the hole to an elevation 30 feet below the ground surface. Any impervious layers encountered will be sealed with bentonite pellets. Sealing will be done with San Joaquin Local Health District' s staff present and will meet San Joaquin County standards. Once the slurry seal is set, the remainder of the hole will be constructed and developed as Groundwater Monitoring Well No. 8. This will enable the engineer/geologist to better understand the upper 100 feet stratigraphy and associated aquifers at a reasonable client cost. If more than one aquifer is found to exist, this exploratory bore hole will also provide valuable information required. to prevent the possibility of creating cross-contamination between aquifers during the future installation of deeper wells. At a later date (August 1988) , it may be desirable to drill a second boring to a deeper depth for further identification of the aquifer' s stratigraphy. 3. Drill at least two (2) monitoring wells to approximately sixty feet (60' ±) . See location of monitoring wells No. 7A and 9A, Exhibit 1 , page 8. The screening depth and length will depend upon the stratigraphy encountered. Construction of the wells will be as stated in #1 above and previously used at the site. All of the above wells will be developed by a surge block and bailing. These are the same procedures that were used to develop wells 5, 6, 7 , 9 and 11 , and the procedures are listed in detail in Appendix C, page C-1 . All drill holes will be evaluated by taking continuous core samples from a hollow stem auger until it can be determined whether the stratigraphy is consistent. Should impervious strata be encountered 6