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=. h,.e •.r- s' :.'S <br /> Problem Assessment Report <br /> •- USA Petroleum Station No. 65, Lodi, California December 5, 1989 <br /> f AGS 87050-3 <br /> f <br /> Boring B-7 (Plates P-12 through P-14) encountered sand, silty sand, silt and clay. Tire <br /> I <br /> deposits as logged were less than 8-feet thick. The aquifer was logged as a sand with a <br /> trace of m,�dium- to coarse grained gravel. <br /> i The Map 'View of Crom-Sections Line (Plate P-15) shows the line of vertical cross <br /> sections A-A' and B-B'. Cross section A-A' (plate P-16) is a north-south geologic cross <br /> # . section of the site and cross section 13-13' (Plate P-17) is a south geologic <br /> � g <br /> cross section of the site. The cross sections show levels of sail contamination as not <br /> detected (ND), initial water levels encountered during drilling, measured water levels <br /> taken on April 18, 1989, and the perforation interval. <br /> l ,t <br /> Cross section A-A' shows silt deposits extending from the surface to approximately 20 <br /> f I <br /> feet below grade. .At approximately 20 to 30 feet below grade a 10-foot clay layer r <br /> thickens to the north and grades into a poorly sorted sand. Above the water-bearing <br /> s <br /> zone is a layer of silt with very fine-grained sand or clay indicating a confined aquifer. = <br /> The aquifer is composed of Poorly g g <br /> p y graded sand ran in in'thickness from 6 to <br /> 16 feet. A continuous sand body extends between wells NI%V-1 and N-IW-4 and grades <br /> 4k � . <br /> into silt with fine-grained sand to the south. a <br /> Cross section B-13 shows a sand deposit interfingering liOweeu wells S-1 and S-2 at <br /> z <br /> approximately 5 to 25 feet below grade, The sand deposit grades into a silt and.clay r <br /> } <br /> e 28 <br /> �i�it�/led Geos Wems <br />