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Mr. Jerry Lile <br /> July 17, 2000 <br /> Page 3 <br /> Recommendation <br /> Please clarify which PAH exceeded the PRG four times, if any, for soil samples <br /> collected from Area 10. Also, identify the boring and depth for each of these <br /> samples. <br /> 4) Page 26, second paragraph: It is reported that soluble lead results obtained using <br /> the Soluble Threshold Limit Concentration Deionized (STLC DI) method ranged from <br /> 0.011 to 0.081 mg/L. These results may indicate a potential threat to groundwater <br /> quality. Beneficial use protective numerical limits for soil established by the Regional <br /> Water Quality Control Board (RWQCB) to protect municipal and domestic water supply <br /> may be required. <br /> Recommendation <br /> The GSU recommends consulting with the RWQCB to determine if beneficial <br /> limits apply to this site. <br /> 5) Diesel was detected in groundwater in 10 of 12 groundwater samples collected <br /> during the recent investigation at detected concentrations ranging from 0.05 to 0.18 <br /> mg/L. These concentrations may be of concern to the RWQCB. The concentrations <br /> may exceed beneficial limit criteria for diesel. It is important to note that diesel and <br /> motor oil have been detected in the soil and may have or be acting as a source of <br /> groundwater degradation. It is possible the motor oil range petroleum hydrocarbons <br /> overlap with diesel range petroleum hydrocarbons and as such infiltration of detected <br /> motor oil constituents to groundwater may be detected as diesel in the groundwater <br /> samples. On page 27 it is indicated that paint contamination occurred in the laboratory <br /> at the same time groundwater samples were being analyzed and therefore the dieser <br /> hits could have been a result of laboratory contamination. <br /> Recommendation <br /> The GSU recommends consulting with the RWQCB to determine if beneficial <br /> limits apply to this site. If diesel concentrations in groundwater exceed the <br /> beneficial use limit it may be necessary to calculate cleanup levels for diesel and <br /> motor oil in vadose zone soil based on leachability and environmental <br /> attenuation factors. If the diesel results are believed to be the result of laboratory <br /> contamination then additional groundwater samples should be collected and <br /> analyzed. This may only be necessary if beneficial use limit for diesel are found <br /> to apply at this site. <br /> C:OFFICEIWPWINIWPDOCSIWPSUREW ORSHRI.WPD <br />