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in 0 10/0 13 <br /> Jerry Lile Page 5 <br /> February 2.2005 <br /> calculating exposure point concentrations (EPCs)for current exposure scenafts. <br /> Subsurface soils up to 10 or 12 bgs can become redistributed to the surface during <br /> redevelopment. Therefore, for future exposure sc9narios, use the greater of the' <br /> surface soil concentration or the 0 to 10 or 12 ft bgs soil interval concentration for <br /> each ctiemieal of potential concem (COPC)as the dxposure point concentration <br /> (EPC), consistent with HERD's recommendation in our meeting ori January 7, 2b03, <br /> 17. Exposure Areas-Consistent with the receptors use of the land. While sveraging <br /> over the whole site may be appropriate for outdoor air exposures,for soil exposures <br /> use an area comparable-to a residential lot size when evaluatrng the residential <br /> scenario, in accordance with DTSC and EPA guidance(OTSC, 1999;EPA, 1996; <br /> EPA, 4989). Hi=RD recognizes that not all media were sampled at a density <br /> sufficient to obtain.EPCs for residential lot size exposure units. For soil, ff sampling' <br /> density of a COPC is insufficient for residential backyard area averaging(that is less. <br /> than W samples per residential tot area), HERD recommends use of a hot spot <br /> approach (EPA, 1989). <br /> SPECIFIC COMMENTS <br /> 1, Many of HERD's comments and agreements reached-in meetings(both in person and <br /> via teleconference)have yet to be-completed by the responsible parties. Some of the <br /> key doduments and meetings with outstanding follow-through are as follows. <br /> a. HERD participated In conference calls on January 7,2004,Januaryl2,2004,and <br /> January 29,2004 to discuss underground pipes discovered in the-undeveloped <br /> porllon of the L& M OU. On Monday,Jammryl2,2004(the day HERD received <br /> the January 9,-2004 Uderground U&Ny Seek*Reporr prepared by 8ECOR), <br /> HERD provided oral comments including apparent Incorrsistencles between photos <br /> and captions or text. HERD recommended completion of site cheracterization prior <br /> to preparing a health risk assessment in order to avoid the ilkely.possibtllty that the <br /> risk assessment wail be unacceptable and another risk assessment will need to be <br /> performed rrtrrmng adequate site characterization data. The.responslble parties <br /> were to submit a full underground utility report and work plan for additional <br /> sampling and analyses. in the January 29,2044 conference call it was agreed that - <br /> among other topics,our next teleo6riterence would Include a conceptual plan <br /> prepared by the responsible partles for sampling and analyses in the area ofthe <br /> newly discovered underground pipelines. There has been no€allow through by the <br /> responsible parties on any of these issues Identified over a year ago. <br /> On February 2, 2004 HERD received the January 30, 2004, 'Summary of Hamar? <br /> Health RfskAssessment Data Collection, L&•M OU, Stockton, Califomle" <br /> prepared by Earth Tech in Sacramento, Califorhia; on February 8, 2004 HERD <br /> participated in a teleconference and provided comments based ori a time-lighted <br /> review,including the-need for depletion of storm drain, sewer and water lines In <br /> the apartment area, identification of Visual contamination,and potential indoor air- <br /> Issues. Vinyl chloride,tribhlorcethylene (TCE),and tetraohloroethylene (PEE) <br /> were detected-in soil gas under apartment buildings at concentrations generating <br /> concern for risks from indoor-air using default assumptions,whereas benzene <br /> 0=2&doo <br />