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k'9 KLEINFELDER Based on detections of TPH-D and TPH-MO at sample location TPI at a depth of approximately 6 feet bsg, two additional samples were collected at depths of approximately 9 and 15 feet bsg. These two soil samples were analyzed for the following: ' • Total Extractable Petroleum Hydrocarbons as referenced to Diesel and Motor Oil [TPH- D/TPH-MO] by EPA Method 8015B/DHS LUFT ' A s ummary o f t he r esults a re s hown o n a ttached T able 1 . T hree o f t he f our s hallow d iscrete excavation soil samples (Cl, C2, C3) were none detected for the requested petroleum ' constituents. TPH-G, TPH-D and TPH-MO were detected in the fourth shallow soil sample (CTDIS) at relatively low concentrations of 23 milligram/kilogram (mg/kg), 21 mg/kg and 40 mg/kg, respectively. Please note for clarity, the respective sample designations of the Test Pits TPI, TP2 and TP-3 (November 30, 2004 sample event), such as TPl-4', refers to the trench depth beneath the existing shallow excavation of 2 feet, for a total of 6 feet bsg. Therefore, the actual sample depth is actually two feet deeper than the sample designation. The sample designations for TPI on December 16, 2004 is based upon surface grade since the shallow excavation was no longer ' present. Two of the three test pit samples, TP2 and TP3, collected at depth of approximately 6 and 8 feet bsg, respectively were none detected for the requested petroleum constituents. TPH-D and TPH- ' MO were detected from a soil sample colleted at a depth of approximately 6 feet bsg from Test Pit TP-1. Re-sampling at this location at depths of approximately 9 and 15 feet bsg resulted in none detect results for TPH-D and TPH-MO. ' A single 4-point composite stockpile sample was collected from each of the two soil stockpiles generated during excavation activities. TPH-G was detected in one of the stockpiles (SPD) at ' 7.6 mg/kg. TPH-D and TPH-MO were detected in both stockpiles. TPH-D ranged from 14 to 27 mg/kg and TPH-MO ranged from 77 to 240 mg/kg. BTEX constituents were not detected in either stockpile. ' For additional details please refer to the attached chain-of-custody form and analytical results in Attachment B. ' ABBREVIATED LEACHING POTENTIAL ASSESSMENT The following leaching potential assessment is based on a general Leaching Potential Worksheet previously forwarded to Kleinfelder from the county [based on a State Regional Water Quality Control Board (SRWQCB) leaking underground fuel tank(LUFT) manual, dated October 1989]. The worksheet is used primarily to assess underground storage tank spills and was evaluated as being relevant to near surface gas and diesel concentrations detected at the subject site, which was 23 mg/kg (CTDIS) for TPH-G. TPH-D concentrations were detected at 21 mg/kg from ' CTDIS. The highest TPH-D concentration was detected at 27 mg/kg from a stockpile soil sample. This worksheet is a general form which takes into account relative information such as depth to groundwater, subsurface fractures, average precipitation, man made conduits, and nearby relevant features (wells, coarse soil etc.). As part o f evaluating depth to groundwater, 51726/ST05R157/DH:ly Page 4 of 7 2005,Kleinfelder, Inc. February 8,2005