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®011/013 <br /> • Jerry L118 Page b <br /> February 2, 2005 <br /> and hydrogen sulfide were detected In 5011 gas at locations that are not under <br /> current buildings at concentrations of concern for risks to potential future Indoor <br /> air using default•assumpfions. Methane,detected in soil gas in excess of the <br /> lower explosive limit(LEL),was brought to the attention of local fire departments. <br /> HERD noted soil concentrations of lead (88-11, 1790 ppm)and benzo(a)pyrene <br /> (B(a)P up to 0.74 mg/kg)were above levels of human health concerns. HERD <br /> recommended additional active soil gas sampling and analyses Using 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(rain 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 throughbas been some additional passlve methane investigation <br /> with hand held Instruments,though no measurements were collected from under <br /> any buildings. <br /> c. HERD reviewed the June 3,2004 ')raft Human Health RtskAssessment at the L & <br /> M Operable Unit end Delle Gateway Apartments, Stanton,CaMmia'and the July <br /> 14,2004 t=lnal Human Health Rlsk Assessment at the L & M Operable Unit and <br /> Delia GatewayApartmants, Stockton, Ca0(omia"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 to the text,tables,or figures besides <br /> changing'draft"to'final', HERD's review of the'finar HRA document was very <br /> limited,focusing on pages that were missing from the"draff HRA, In a September <br /> 9,2004 memorandum HERD Issued written comments on these two documents <br /> identifying numerous deficiencies and inconsistencies which rendered the HRA <br /> unacceptable.Including she 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),-preparing a separate HRA using <br /> a hot spot approach for each AOC. One AOC being the Delta'View Apartments(the <br /> apartments'area)and theseoond AOC being the undeveloped'area. HERD recommends <br /> providing the above listed ADDITIONAL DOCUMENTATiONIDATA NEEDED to <br /> continue progress towards an acceptable HRA, HERD strongly recommends filling all <br /> soil gas data gaps prior to operation of an EVE system,including not only soil gas <br /> sampling 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&M Operable Unit'dated September 11,2003 by <br /> Earth Tech with modifications identified In this memo and attached tables); (2)submittal of <br /> • 050202JLdm - <br />