SITE INFORMATION AND CORRESPONDENCE

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W,2: Mr. John Russell Page 2 of 5 Comments on Cleanup Fund Site Closure Recommendations January 18, 2011 claim No.H31 -22871 now=)-S. Hwy 99, Ripon Closure on this site Is delayed by two Issues: - a vapor intrusion evaluation that encountered TPH9 In soli gas at concentrations that exceeded the Tier I evaluation, and - EHD is concerned about the analysts and results for TPHd. Subsequentvapor data manipulation and evaluation by the consultant has been by methods that am not supported by authoritative guidance documents, such as those provided by the California Department of Toxic Substances Control (DTSC)or by the Los Angeles Regional Water Quality Control Board (LARWQCB). The EHD requested technical data supporting the subdivision of total petroleum hydrocarbons quantified as gasoline TPHg data Into smaller carbon number ranges than were reported by the analytical laboratory and validation of the data manipulation methods employed by the consultant The consultant did not analyze the soil gas samples for total petroleum hydrocarbons quanUfled as diesel TPI-Id by method TO-17, as was proposed In the approved work plan, and has not provided a justification for deviating from the work plan or demonstrated that the results of the analysis employed are equivalent to those that would have been obtained by method TO-17.The EHD requested very specific Information regarding these issues in correspondence dated September 23, 2009, and the responding report (No Furthw Action Request) issued by the consultant dated November 10, 2009, did not directly address any of these issues. By letter dated 13 December 2010, the EHD directed that the technical Justification for the methodology utilized to enter the soil gas TPHg data in to Johnson and Ettinger Model be submitted to the EHD within 30 days, but It has not been received. The unusual TPHd analytical mad-sod and results remain an unresolved Issue. In an electronic mail submitted to the EHD on July 31, 2010, the consultant stated `Additional chromadograms 1br TPH-d QAIQC for spa(ale) me" 8260 are not avaNable, as the GCUS method did not use a TPhLD standard for evatuadon. A notation an the base of the an&Wk% states 7PH-d was performed by CGUS analysis for TPH-d range compounds and the detection lffn# Is 20,000 mkn9rams per cubic meter:' In December 2010, the EHD Issued a directive to the responsible party(RP)to resample the soil gas and utilize proper analytical techniques to resolve the Issue. If the RP does not comply, the site will be referred to the CVRWQCB for final disposition. If this Issue had been adequately addressed In the November 2009 report the EHD believes this site would now be closed (or nearly closed). The EHD believes this site should be closed, and intuitively, a problem with TPHd vapor intrusion does riot seem vary likely, but vapor intrusion has been identified at the State level as a potential health Issue that must be addressed before closing a site. The EHD is attempting to exercise due diligence by acquiring scientifically defensible data and/or a sound technical justification that demonstrates that the health risk posed by potential vapor intrusion from residual contamination Is at or below an acceptable level. If the CUF technical staff can provide the EHD with additional technical Insight on this matter, it will be appreciated and carefully considered. claim No.Beg—5491 F Street. Banta The issues related to impacted soil and groundwater have been resolved. The consultant has recommended confirmation soil gas sampling to reevaluate the vapor intrusion potential, as the initial soil gas assessment was conducted during active soil gas extraction (SVE). The EHD has