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JAN-16-1100 04:13 FROM GEOLOGICAL TECHNICS TO 4640130 P.02 yj�eofigicafq�tfinks Inc. zreribWxwa arra ca&a g r491 emacs s3aXasz March 25, 1997 Mr. Ron Rowe San Joaquin County Public Health Services Environmental Health Division 445 San Joaquin Street P.O. Box 2009 Stockton,CA 95201 Re: Water Well Construction Survey C&B Equipment 7474 West 11th Street,Tracy,California Dear At.Rowe: Geological Technics Inc. has reviewed the records of both the SWRCB and San Joaquin County for the Drillers Log of the domestic well located on C & B Equipment property at 7474 West 11th Street,Tracy,California. A log of this well was not located at either agency. However,logs of wells on two properties approximately 7 miles to the south were available. These logs have not been attached because they are of poor quality and would not fax well_ They wM be included with the work plan. We have made a valiant effort to locate well logs for other properties in the vicinity both by street address and by township and range, but have not come up with any from either the county or state. At thispomi t we would like to proceed with developing the work plan for the site and put this project back on schedule. Too do this we will finish the work plan and submit it to you within one week of this letter. Here follows a summary of what we are planning to do for the construction of the deep monitoring well in the absence of geologic data for that zone. The shallow water table wells that are currently on the property are 20 feet deep and the new water table wells are proposed to be construction similarly. The three shallow monitoring wells provide a geologic record to a depth of 20 feet. The geology from 20 feet down to the expected depth of the deep well, 45 feet, the geology is unknown. To allow for the installation of the deep well and to decrease possibility of breaching a clay layer which acts as a barrier to the vertical migration of contaminants we propose the following method of drilling. • MW-101 will be drilled from the surface to 20 feet depth and sampled every 5 feet. From 20 feet on it will be sampled continuously for geology. This will provide a thorough understanding of the deeper geology. • If a clay layer is encountered of greater then 3 foot thickness a conductor casing will be installed into the clay unit. • The well will then be drilled through the conductor cssing, sampling continuously until a sandy layer is encountered below the clay. • The well will be 2 inch diameter and have a 5 foot screen. • In the event that the clay layer is non-fractured and is continuous for 25 feet it will be assumed it is an affective barrier to vortical contaminant migration and the attempt to set the well will be abandoned. The borehole will be grouted with a neat cement grout, with a 40/a bentonite mix, and a tremie pipe from the bottom up in order to displace all groundwater from the hole. A concrete cap will be added to bring the borehole to grade with the surrounding surface.