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=.Yt_; = -. i'.-., moi -3-a g 41 r ) were not detected in most of the ethylbenzene, ande es (HowBTXE one nt at ons of 0.007 ppm soil samples analyzed, or less were detected in samples from 15.5 feet below grade in boring B-14, from 25.5 and 36.5 feet below grade in boring B-10 (MW-4), and 15.3 feet below grade in boring B-11. Groundwater rcundwate samples nocollected from all four monitoring tectable concentrations of TPPH or BTXE. All of the on-site monitoring wells were surveyed for top-of-casing elevations to mean st-al level by John E. Koch,land surveyor, LS4811, on October 16, 1989. The USGS benchmark314-inch iron pin is a . monument at the intersection of Fresno Street and Navy Drive. Groundwater flow beneath the site on October , 1 99 of 0 was in an This southeast direction at a very shallow gradient groundwater now direction does not correspond to the northwest 3 groundwater now direction estimated for September 11, 1987, and the north flow direction estimated for March 28, 1988fssihe al curac or of these earlier flow directions is suspect since a pethe was not used. In addition, the flow directions mou bdwate°t pumping ongoing drought which is causing increased gr in the area. Surface water in the area is limited to Mormon Slough which flows intermittently northwest about 1 mile north of the site and discharges into the Stockton Deep Water Channel. a Soils have been characterized from previous soil investigations performed at the former underground tank lite silts In tend clays the area of o tanks the site is underlain by p er discontinuous layers of clayey sand to a depth of approidmnao le 26 feet to below grade. These silts and clays are underlain by high-estimated permeability silty sand and clean sand. :e r� 1-7