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Problem Assessment Report December 5, 1484 <br /> USA Petroleum Station No. 65, Lodi, California AGS 87050-3 <br /> SOIL STRAT;tGRAPIIY <br /> Previous drilling at the site indicated deposits of sand, silt, and clayey sand to sandy clay <br /> in borings S-1 and S-2. Geologic cross sections show interbedded layers of sand, silty <br /> sand,clayey sand, silt and clay. These various deposits thicken from approximately 5 <br /> feet to 25 feet from well MW-2 to well MW-3. The deposits also grade from silt and <br /> clay in MW-2 to sand and silt in MW-3 (Applied GeoSystems, October 13, 1987). <br /> Copies of these cross sections are includ"-d in Appendix B. <br /> Borings B-4 and B-5 (Plates P-5 through P-8) encountered sediments consisting of <br /> interbedded silty sand, sandy silt; silt,:and silty clay to a depth of approximately 45 feet <br /> below grade, underlain; by a laver of fine- to medium-grained sand about 10- to 14-feet <br /> thick. A silty clay was encountered below the sand. We suspended sampling between . <br /> 48 and 52 feet.in MW-5 due to sands heaving into the hollow stem of the augers. A <br /> clay aqu'txrd was encountered at 52 feet below grade. <br /> f <br /> Boring B-6 (Plates P-9. through P-11) encountered sediments consisting of sand layers 2- <br /> ' 6 feet thick along with 2- 16 feet thick silt and clay layers. The silt and clay layers are i <br /> mixed.with traces of sand. The aquifer was logged as a silty clay layer with a trace of t <br /> rx € line grained sand <br /> 27 . <br /> 1. <br /> "c „ . . <br />