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from surface grade to 15 feet bsg,with a coarse grain sand unit occurring between 20 feet and 25 feet bsg at CPT2 The zone is characterized by low pore pressures Hydrogeologic Unit 1 (HU1), at the top of the current saturated zone, extends from 15 feet to approximately 60 feet bsg and is comprised laterally continuous alternating layers of poorly graded I sand with silt and silty sand This unit has flow unit characteristics Hydrogeologic Unit 2 (HU2) extends from 60 feet to approximately 90 feet bsg and is composed dominantly of stiff, fine-grained soil, silty clay with a thin bed of poorly graded sand at 80 feet bsg Hydrogeologic Unit 3 (HU3) extends from 90 feet bsg to total depth,HU3 is composed of interbedded stiff,fine-grained soil,silty poorly graded sand, silty clay and silty sands from 90 feet bsg to approximately 110 feet bsg This unit has flow unit characteristics Hydrogeologic units were depicted in cross sectional view B-B' I in Cone Penetrometer Testing Report - .171ai fib, z60� Analytical data from a total of eight grab groTd water samples from HU1, HU2 and HU3 are as follows TPH-g and TPH-d were detected in grab water samples collected from CPT2--89 at concentrations of 120 gg/1 and 95µg/l,respectively These detections are likely due to silt within the I water sample causing a false detection of TPH-d, TPH-g and TPH-d were detected in grab water samples collected from CPT2-110 at concentrations of 380 µg/1 and 380µg11, respectively These detections are likely due to a detection of general biological Impact to the site, like natural ethene from a septic system or silt within the water sample causing a false detection of TPH-d The BTEX compounds toluene and ethylbenzene were detected in ground water samples collected • from CPT2-110 at concentrations of 1 3 µg11 and 1 0 gg/l, respectively However, gas chromatography mass spectrophotometer analysis did not Identify either of these compounds ' SITE CONCEPTUAL MODEL The major portion of the site consists of asphalt or concrete paved area One building containing an office and store is located on the property(Figure 2) One domestic ground water well is located on the property and an additional domestic well is located on the property east of the site The ' surrounding sites are used for boat storage/sales and for agricultural purposes, a California Department of Transportation road right-of-way is located west and north of the site ' A set of three USTs and three main dispensers islands operated on the site for approximately 15 years, from the mid 1980s to the late 1990s The three USTs were removed from a common I excavation near the northwest corner of the site The history of the USTs use, tank tests, product inventory and repairs are not known to AGE A140 Uns �*� -T3 ri/ 4 #&4a4 k.4 S dl si"e,�>-n-� 19 99, V*L Only one UST removallamplmg had detectable concentrations of hydrocarbons,yet all sample had ' moderate detections of fuel additives High concentrations of hydrocarbons and low concentrations of fuel additives were generally detected in soil samples D2, D3 and D5 from the former dispenser ' areas The dispenser soil samples exhibited significant staining and hydrocarbon odor IAdvanced Geo$nvironmental,Inc I