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i • GeologicafTechnics Inc. 2741 Rtmr Road M.&,W,Calaf. 95351 (209)538-6424/'jxC#538-5852 August 25, 1997 ' Project No 4252 Project Name George's Service ' Ms Mary Meays San Joaquin County Public Health Services Environmental Health Division 304 Weber Street P O Box 2009 Stockton, CA 95201 Re Domestic Well Survey and Geologic Cross Sections George's Service, 1600 Durham Ferry Road, Tracy, California Dear Ms Meays 1 Domestic Well Log Review As requested by you, here is the completed domestic well survey for a 2,000 foot radius around George's Service, 1600 Durham Ferry Rd, Tracy, CA To complete this task the site was walked and the table titled "George's Well Log Survey" was made This table has the address of residences in the immediate vicinity with domestic wells on their properties Specific well logs were then requested from the State of California Department of Water Resources on these properties A visit was then paid to the Department of Water Resources so that Geological Technics Personnel could review all well logs available and make copies of them The well logs that were available for this area are included in Appendix A In comparing the table and the logs in Appendix A it is apparent that a great deal of the wells in the area do not have logs on file Geoloizic Cross Sections Geologic cross sections were completed in West to East (A-A') and South to North (B-B') directions To complete these cross sections it was necessary to group the geology into either fine or coarse because water well drillers do not generally get any more specific then that Silts and clays were grouped into the fine category and sands and gravels were grouped into the coarse category 1 Generally the geology in West to East direction was more continuos then the geology in the South to North direction This is most likely due to the sediments transport direction in generally from the west with the sediments originating from the Diablo range From review the construction of the domestic wells it appears that most of the wells target either a coarse zone, generally gravely, that ranges from 75 to 100 feet below ground surface or several coarse zones that are between 120 and 200 feet below ground surface The logs show that some wells have a single screened interval, some have multiple screened casing intervals, some are open bottom, and some have both screen and open bottom Other well logs are not clear on well construction It is clear the that coarse grained units between 75 and 100 feet bgs under the site is the primary aquifer honzon for several domestic wells in the immediate vicinity of the site Even though we were not able to come up with a log for Mr Milton Birkhahn's well (1697 W Durham Ferry Rd), he stated that his well was about 100 feet deep and was in the same sandy strata that other wells in the area are in The greatest threat from the contamination at George's Service is to the shallower water producing zone, 75 to 100 feet below ground surface Contamination, both soil and