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aci i„cueo it -� rnn a009/0 17 <br /> Jerry Lile Page 4 <br /> February 2.2005 ' <br /> b: Total concentratlons of contaminants In groundwater are needed for risk <br /> assessment purposes. Identify analytical chemistry data 001160ted from TCLP <br /> analyses or filtered groundwater(as an example, in the January 24, 2003 <br /> SECOR report all metals date are dissolved 'concentrations);thesedata are <br /> unacceptable for use In the risk assessment. <br /> c. Results of groundwater ana(yses for polycyclic aromatic hydrocarbons is missing <br /> page 3 of 4 and Results of groundwater analyses for volatile organic compounds <br /> Is missing pages 5, B. B and 9. <br /> d. Groundwater Data DLs were elevated for several chemicals (1,2- <br /> dichloropropane, benzene,naphthalene,MTBE,methylene chloride,n- <br /> butyibenzene,trichloroethene (TCE),bromodichioromethene, carbon <br /> tetrachloride, tetrachloroethene(PCE),trans-1,24obloropmpene, vinyl chloride, <br /> B(a)P,brombform, txomomethane, chloroethane,chloroform,.ohioromethane, <br /> dibromochloromethene,ethanol. banzo(a)anthrecene, benzo(k)fluorenthene, and. <br /> indeno(1,2,3-cd)pyrena with DLs in excess of the California MCL and/or the U.S. <br /> EPA Region IX PRG fortep'water. Consequently,the analyses were not <br /> sensltive enough to detect heakh-based concentrations of these chemicals, <br /> which maybe present In cn-site groundwater at levels of human health concern. <br /> e_ •Every groundwater sample that was analyzed for dibenz(a,h)anthracene was. <br /> • rejected;therefore there are no groundwater data for this chemical. Thus. <br /> ensure future analyses generate acceptable data for the HRA. <br /> 13. Apartments'area: Priorto'operatton ofthe'SVE systeffoollectsupplemental dots to <br /> fill all active soil gas and soil geotechnical parameters consistent with DTSC- <br /> approved'Work Plan for Collection of Data for Human Heakhh Risk Assessment furthe <br /> L&M Operable Unit"dated September 11,2003 by Earth Tech with modifications <br /> kdenti l6d In this memo and attached tables. Please note the addlllonal-soll gas <br /> sampling methods requested under the Data Gaps column of the enclosed tabtes., <br /> Consult with DTSC to determine if additional sample locations are warranted due to <br /> locations of urlderground utilities or any other features hereafter discovered. In <br /> accordance with DiSC guidance, prior to collecting samples observe a minimum 30 <br /> day reequilibration period after any loll disturbances(DTSC,2004). <br /> 14.Undeveloped area: Work plan for sampling and analyses to fill all data gaps, <br /> including data requested in the following table. <br /> 15.Supplemental date collected consistent with•OTSCapproved work plan.' <br /> 16.Conceptual Site Model (CSM)-Submit CSM consistent with comments In HERD's <br /> September 9,2004 memorandum. <br /> 16.Surface soil--HERD continues to recommend using 0-6 Inches glow ground' <br /> surface(bgs)as surface soil for the HRA, not 0-6 ft bgs as was employed in the <br /> HRA. Use no more than the 0—2 or 2.5 ft bgs soil interval as surface soil Tor <br />