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KEI-P91-0202 .QR1 May 4 , 1992 Page 7 turnun r, la—i,-H—by---Cate'y:materia, that generally extend to the maximumdeptYis exp'roed(Sto 8 feet below grade) , except for MW3, where an approximately 4 foot thick zone of sand was encoun- tered at about 81 to 85 feet below grade. Also, at the base of the relatively thick sequence of interbedded sand and silt is an approximately 2 to 5 foot thick zone of silty to well graded gravel, except at MW2, where an approximately 2 foot thick lens of poorly graded sand was encountered between the gravel and the clay materials. In addition, within the relatively thick sequence of sand and silt, an approximate 19 to 20 foot thick uninterrupted zone of sand was encountered that extends to a depth of about 61. 5 to 62 feet below grade across the site. Additionally, ground water was initially encountered during drilling activities within both sand and silt materials at approximately 4 . 5 to 5. 5 feet above the relatively consistent gravel bed discussed above. The results of our current subsurface study (the log of borings MW4 through MW9, EB1 and EB2) indicate that the subject site is underlain predominantly by interbedded silt and sand beds that appear to be at least locally lenticular (similar to our previous study) . Also, a relatively laterally consistent clay bed was encountered at depths ranging from 77 . 5 to 80 feet below grade (and which extends to a least the maximum depths explored) . ANALYTICAL RESULTS Ground water samples were analyzed at Sequoia Analytical Laboratory in Concord, California, and were accompanied by properly executed Chain of Custody documentation. The samples were analyzed for TPH as gasoline by EPA method 5030 in conjunction with modified 8015, and BTX&E by EPA method 8020. Analytical results of the ground water samples collected from monitoring wells MW1, MW3 , MW4, MW5, MW7, and MW8 indicated non- detectable levels of TPH as gasoline and BTX&E. Analytical results of the ground water samples collected from monitoring wells N- 2 �, and indicated levels of 5�� a_, s �so�lln� at concentrations of 180 ppb, 99 ppb, and 70 _pb, res ectively. B.e_nzen was detected in monitoring wells "MiJ2. MW:6 and' MW, at concentrations of 2 . 3 ppb, 0. 95 ppb, and 0. 57 ppb, respectively. The concentrations of TPH as gasoline and benzene detected in the ground water samples collected on April 7, 1992 , are shown on the attached Site Plan, Figure la. The results of the analyses are summarized in Table 2 . Copies of the analytical results and Chain of Custody documentation are attached to this report.