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ATC Associates Inc. vv 11171 one Palm Avenue, Suite 201 Modesto, California 95351 209-579-2221 r..r ASSOCIATES I N C. fax: 209-579-2225 r f On December 2, 2004, ATC supervised the advancement of five soil borings, SB-1 through SB- O, to approximately 10 feet bgs. Three of the borings (SB-1 through SB-3) were advanced on the V,, subject property and two borings (SB-4 and SB-5) were advanced west of the site along Holly Drive, for the purposes of evaluating the vertical and horizontal extent of petroleum and oxygenate impacted soil and groundwater. A sixth boring was attempted but probe refusal was encountered. The boring was abandoned and filled to the surface with neat grout. Woodward Drilling advanced the borings using a truck mounted Geoprobe® narrow diameter rig employing direct push technology. Soils were continuously collected from borings SB-1 through SB-5 in acetate sampling tubes and described according to the Unified Soil Classification System. Groundwater samples were collected from borings SB-1 through SB-5 at the depth groundwater was first encountered, approximately 5 to 10 feet bgs. Upon completion of each boring, slotted 3/4-inch, diameter PVC well screen was placed within the exposed boring. The groundwater was allowed to equilibrate and then samples were manually collected using disposable polyethylene bailers. Following soil and groundwater sample collection, the borings were backfilled with neat cement grout to surface grade. Soil samples collected from borings SB-1 through SB-5 and rl° CPT-1 and CPT-2 contained detectable concentrations of total petroleum hydrocarbons quantified as gasoline (TPHg), benzene, toluene, ethylbenzene and total xylenes (BTEX), and the C/c��j�' y fuel oxygenate methyl tertiary butyl ether (MTBE). Maximum detectable concentrations were S�3 noted as follows: TPHg 330 milligrams per kilograms (mg/kg) in SB-4 at 5.5 to 6.0 feet bgs, 5� benzene (4.3 mg/kg in SB-4 at 7.5 to 8.0 feet bgs), and MTBE (4.0 mg/kg in CPT-2 at 7.0 feetgt bgs. Groundwater samples collected from borings SB-2 through SB-4 and CPT-2 contained detectable concentrations of TPHg, BTEX, and MTBE. TPHg concentrations ranged from <50 micrograms per liter(gg/1) (SB-1 and SB-5) to 8,700 gg/l (SB-4); benzene concentrations ranged from <0.50 µg/1 (SB-1 and SB-5) to 83 gg/1 (SB-4); and MTBE concentrations ranged from <0.50 gg/l (SB-1 and SB-5) to 8,100 gg/1 (SB-3). Groundwater samples were collected from CPT-2 at a depth of 41 and 67 feet bgs, respectively. From each interval, TPHg was detected at 7,600 gg/l and 300 gg/l, respectively. Benzene was detected at 22 gg/1 and 2.7 gg/1, respectively. MTBE was detected at 2,100 gg/1 and 120 gg/1, respectively. _ On October 23, 2006, the SJCEHD issued a written directive requesting submittal of a workplan for the installation of additional groundwater monitoring wells. ;JJ u---a( SUBSURFACE GEOLOGY / V Soil beneath the site generally consists of inorganic clays and silty clays to a depth of 10 feet bgs as observed from the direct push Geoprobe® soil borings. The CPT in situ down-hole measuring technique allowed for a more comprehensive lithologic evaluation with a maximum explored depth of 80 feet bgs. Silts, sands, and clays were observed throughout the CPT boring interval with three distinctive sand and gravel-sand units located from approximately 20 to 25 feet bgs, 35 to 45 feet " 4 ATC Associates Inc. S:\Environmental\25847.0037\Work Plan additional vert-hor delineationTH2.doc 6W