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a4 1} <br /> FHS/EHD <br /> October 3, 2002 <br /> Page 5 of 5 <br /> For the most conservative approach, we re-ran the model assuming no biodegradation of <br /> MTBE Under these conditions the concentrations would be as follows <br /> Compound Source Conc Facility Well Conc Domestic Well Conc <br /> MTBE 8 6 ppb 13 ppb 4 9 ppb <br /> These transport simulations do not account for the fact that the supply wells are presumably <br /> screened far below the depth of contamination Modeling data are included in Attachment F <br /> In our opinion your request for additional investigation is unwarranted The data collected from this <br /> site during the course of the investigation are more than adequate to illustrate that this is a low risk <br /> site The tank removal and minor overexcavation have removed the contamination source from the <br /> soil, dissolved groundwater contamination is limited to a relatively small area within the uppermost <br /> 6-7 feet of the saturated zone, and MTBE is only marginally above the secondary MCL in a single <br /> well The groundwater transport modeling included herein supports this conclusion Ground Zero <br /> recommends that this site be closed with "No Further Action" required <br /> Please feel free to contact the undersigned (209838-9888) at your convenience if you have any <br /> . questions or comments regarding this submittal <br /> f <br /> Respectfully, ED GAO <br /> Ground Zero Analysis, Inc <br /> JOHN P <br /> [AN" <br /> No 6795 <br /> John P Lane <br /> CA Registered Geologist No 6795 O <br /> ;'-1 G� O <br /> GREGORY P <br /> Gregory P Stahl, RG 5023 STAHL <br /> CA Certified Hydrogeologist No 264 <br /> Na 5023 � <br /> P <br /> Attachments l� OF CALIF <br /> cc Mr Marty Hartzell, CRWQCB-Central Valley Region <br /> Mr Martin Harris, Tuff Boy Trailers <br /> i <br /> G\Data\GROUNDZE\T uffBoy\Corresp\0902gpsrevd doe <br />