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� ....,.,, ,c. . n.. 12011/013 <br /> Jerry Lite Page 6 <br /> February 2,2005 <br /> and hydrogen sulfide were detected in soil gas at locations that are not under <br /> current buildings at concentrations of concern for risks to potential fixture indoor <br /> air using default-assumptions. Methane,detected in soil gas in excess of the <br /> lower explosive limit(LFL),was brought to the attention of local tin;departments. <br /> HERD noted soil concentrations of lead (86-11, 1790 ppm)and benzo(a)pyrene <br /> (B(a)P up to 0.74 mgtkg)were above levels of human health concems. HERD <br /> recommended additional active soil gas sampling and analyses lysing TO-14 SIM <br /> (to remove masking and the elevated DLs)with resampling at 6 ft bgs and <br /> sampling at the depth of the capillary fringe. HERD also recommended active <br /> soil gas to better characterize methane Including pressure testing since• <br /> concentrations exceeded the LEL.of 53,000 ppmV. HERD requested information <br /> including dates•of the last soil wetting episode(rein events and landscape <br /> Irrigation). The responsible parties acknowledged that the undeveloped area will <br /> likely be addressed in a separate health risk assessment. Over the past year, <br /> the only follow through-has been some additlonsi passive methane Investigation <br /> with hand held Instruments,though no measurements were collected from under <br /> any buildings. <br /> c. HERD revidwed the.lune 3;2004"Draft Human Heatth ftkAssessment at Me L& <br /> M Operable Unit and Dena GatewayApartmenrs, Sfocldon, Cathbmia"and the July <br /> 14,2004 IFInal Human Health Risk Assessment at fhe L&M Operable Unit and <br /> Delle GafewsyApartment's,Stockton, Cafr7omis"both prepared by Earth Tech in <br /> San Jose, California and received by HERD on July 12,2004 and August 4,2004. <br /> respectively. The July 14,2004 version final HRA has a cover letter stating the <br /> document was Identical with no other changes fo the text,tables,or figures besides <br /> changing"draft"to"final", HERD's review of the"final'HRA document was very <br /> limited,focusing on pages that were missing from the"draft"HRA. In a SepteMber <br /> 9,2004 merrrorandum HERD Issued written comments on these two documents <br /> Identifying numbrous deficiencies and inconsistencies which rendered the HRA <br /> unacceptable.Including site characterization Issues and lack of follow through on <br /> previous agreements.• None of the issues identified by HERD have been ' <br /> addressed by the responsible parties. <br /> CONCLUSIONS <br /> To expedite risk evaluations In the apartments'area,the responsible parties should ' <br /> address the L&•M OU as two areas of concern(AOCs),•prepartng a separate HRA using <br /> a hot spot approach for each AOC. One AOC being the Delta'View Apartments(the <br /> apartments`area)end the-second AOC being the undeveloped area. HERD recommends <br /> providing the above listed ADDITIONAL,DOCUMENTATIONiDATA NEEDED to <br /> continue progress towards an aooeptable HRA. HERD strongly recommends filling all <br /> soil gas data gaps prior to operation of an SVE system,including not only soil gas <br /> sarppling and analyses but also collection of soil geotechnical data needed for <br /> predictive indoor air modeling. HERD continues to recommend:(1)collecting <br /> supplemental data to address all data gaps consistent with a DTSC approved sampling <br /> and analyses work plan (for the apartments'area use"Work Plan for Collection-of Data for - <br /> Human Health Risk Assessment forthe L.BM Cperebts Unit"dated September 11,2003 by <br /> Earth Tech with modifications identified In this memo and attached tables);(2)sfibminal of <br /> 050202JLdoc <br />