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vG/ t/cvv� is �G r„/t 0009/013 <br /> Jerry Lile pege 4 <br /> February 2,2005 <br /> b,. Total concentrations of contaminants in groundwater are needed for risk <br /> assessment purposes. Identify analytical chemistry data collected from TCLP <br /> analyses or filtered groundwater(as an example, in the January 24,2003 ' <br /> SECOR report all metals date are dissolved concentrations);these-data are <br /> unacceptable for use in the risk assessment. <br /> c. Results of groundwater analyses 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, 6,6 and 9. <br /> d. Groundwater Data DLs were elevated for severai chemicals(1,2- <br /> dichloropropane, benzene, naphthalene, MTBE,methylene chloride,n- <br /> butylbenzene,trichloroethene (TCE),bromodichlonomethene,carbon <br /> tetrachloride, tetrachlorcetherte (PCE),trans-1,2-dlchloropropene, vinyl chloride, <br /> 6(a)P,brombform, bromomethane,chloroethane,chioroform,.chloromethane, <br /> dibromochlorornethane, ethanol, benzo(a)anthrecene, benzo(k)fluoranthene, and <br /> indeno(1,2,3-cd)pyrene with-DL9 in excess of the California MCI.and/or the U.S. <br /> EPA Region IX PRG fortap'water. Consequently, the analyses were not <br /> sensitive enough to detect health-based concentrations of these chemicals, <br /> which may be present in on-site groundwater at levels of human health concern. <br /> e. Every groundwater sample that was analyzed for dlbenz(a.h)anthracene was'. <br /> rejected;therefore there are no groundwater data for this chemical. Thus, <br /> pnsure future analyses generate acceptable data for the HRA, <br /> 13. Apartments'area: Prior to'opemdon of the'SVE system oollect supplemental data to <br /> fill all active soil gas and soil geotechnical parameters consistent with DTSC- <br /> approved'YVork Plan for Collection of Data for Hurnan Heakh Rlsk Assessment for the- <br /> L&M Operable Unit"d&ted September 11,2003 by Earth Tech with modifications <br /> ldentifi6d In this memo and attached tables, Please note the addiflonal"soll gas <br /> seMpling methods requested under the data Gaps column of the enclosed tables., <br /> Consult with I)TSC to determine If additional sample locations are warranted due to <br /> locations of underground utilities or any other features hereafter discovered. In <br /> accordance with DISC guidance,prior to collecting samples observe a minimum 30 <br /> day reequillbration period after any soil disturbances(I)TSC,2004). <br /> 14.Undeveloped area: Work plan fur sampling and analyses to fill all data baps, <br /> Including data requested in the following table. ' <br /> 15.Supplemental date collected consistent with"DTSC-approved work plan.' <br /> %Conceptual Site Model (CSM)-Submit CSM•consistent with comments In HERD'a <br /> September 9,2004 memorandum. <br /> 16. Surface soil—HERD conflnues to recommend using 0-6 Inchds below 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 /> 05020Z3l.tloc - - . <br />