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AO/FEL ER <br /> Bright People.Right Solutions <br /> Detected Range Soil Screening Levels-Commercial/Industrial Land <br /> Element/Compound Onsite Soil (mg/kg) Use m /k <br /> CHHSLs(1) ESLs(2) RSLs(4) <br /> Lead 4 to 12 320 320 (3) 800 <br /> Total Petroleum 2,500 (TPH 1,800,000(as <br /> Hydrocarbons as 2.5 to 430 None Residual Fuels) mineral oil) <br /> Hydraulic Oil (Ceiling Value] <br /> (1) =Table 1 of CHHSLs, Human Health Basis <br /> (2) =Table A of ESLs, Shallow Soils, Groundwater is Current or Potential Source of Drinking Water <br /> (3) = Human Health Basis <br /> (4) = Regional Screening Level Table <br /> Ceiling Value Basis: Lowest of the Nuisance Odor/Taste threshold <br /> As shown above the total lead values are below the noted SLs. In addition the range of <br /> lead concentrations detected in soil are within reported background levels based on a <br /> study of Air Force bases in California (Hunter et al. 2005). In this study, the upper 95th <br /> percentile background concentrations at California Air Force bases were noted to range <br /> from 11.7 to 59.2 mg/kg for lead in soil at depths ranging from surface to 15 feet. Similarly <br /> a study of soil from 50 benchmark soils in California (Kearney Foundation, March 1996) <br /> indicates a natural background mean concentration for lead at 23.9 mg/kg. Based on this <br /> data it is Kleinfelder's opinion that the lead concentrations detected onsite are below <br /> applicable SLs and are reflective of background lead concentrations in California. <br /> There was no direct SL for total petroleum hydrocarbons (TPH) as hydraulic oil (TPHho), <br /> specifically. The closest categories included TPH as residual fuels (ESLs) and for mineral <br /> oil (RSLs). Residual fuels were defined in the ESLs as heavy hydrocarbons with a carbon <br /> range greater than C24, The carbon range for TPHho will vary but generally range from <br /> C15 to C50 and represent heavier hydrocarbon ranges. Hydraulic oil is closely associated <br /> with and usually contains mostly mineral-type oil. Therefore these two categories for SLs <br /> appear to be the most applicable for comparison to TPHho. The range of TPHho from <br /> onsite soil ranged from 2.5 to 430 mg/kg, but was found to be below both of the referenced <br /> SLs. <br /> Based on this data Kleinfelder does not recommend further action related to onsite soil at <br /> the former UST location. Although the concentrations of TPHho in stockpiled soil is below <br /> 125819.E01/ST013RO732 Page 7 of 10 December 11, 2013 <br /> Copyright 2013 Kleinfelder <br />