Laserfiche WebLink
Extended Site Characterization Report., 7500 West Eleventh Street, Tracy, CA, Page 27 <br /> interpretation of the data available from logs of push-probe and well borings along <br /> Section C-C' (Figure 11), strongly suggests the presence of the same stratum of sands <br /> and silts at similar depths to those at which this stratum of permeable materials was <br /> encountered in borings along Section A-A'. A similar zone of sand and silt is seen on <br /> Section B-B' on Figure 10. (However, along that section, which passes through MW-2 in <br /> the west and MW-4 in the east, there is a distinct discontinuity in the sand facies in the <br /> -3 and MW-3. <br /> )icivnit of borings PP <br /> Beneath the sand stratum found in a zone between some 10 ft. and 25 ft. BGS, there is <br /> another clay zone that appears to be continuous over the whole area explored; its top is at <br /> depths varying between approximately 25 ft. and 28 ft. BGS. Where borings were drilled <br /> to sufficient depth (i.e., on the 7500 West Eleventh Street property itself) that clay layer <br /> was found to have a thickness of some 10 ft. It is underlain by another sand stratum in a <br /> zone between approximately 28 ft and 33 ft. BGS. Beneath that sand lies a third clay <br /> stratum with a thickness of about 5 ft., and beneath that, with its top approximately 35 ft. <br /> BGS, is a thick sand stratum down to at least the maximum depth of exploration (50 ft. <br /> BGS). <br /> The stratigraphy described above is typical of the alluvial fan upon which Tracy and the <br /> surrounding area is situated. <br /> Based on pump tests that SJC has conducted in similar strata at other locations in Tracy, <br /> it is estimated that the clays and silty clays beneath the 7500 West Eleventh Street site <br /> ' have a hydraulic conductivity on the order of 10-4 to 10-6 cm.lsec., while the silts and <br /> sands have permeabilities in the range of 101 to 10-2 cm./sec. (The San Joaquin Company <br /> Inc. 1994.) <br /> �` <br /> sic <br />