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Mr. Maurice Benson - 2 - 30 December 2009 <br /> Defense Logistics Agency <br /> placed as close as feasible to the former UST location, but outside of any excavation <br /> backfill. <br /> 2. Central Valley Water Board staff concurs with DLA's decision to collect additional <br /> CPT/HPT data prior to installation of groundwater monitoring wells. The proposed <br /> CPT/HPT locations will likely enhance the characterization of contaminant extent and <br /> assist with construction of monitoring wells. <br /> 3. Section 3.6 of the Work Plan states that DLA will assess the potential for contaminant <br /> migration into Building 255 indoor air using the Johnson and Ettinger model as a <br /> screening-level tool. Furthermore, DLA will use the model results to estimate the <br /> potential risk to human health and to assess the need for collection of soil vapor analytical <br /> data. However, the Work Plan does not indicate when the modeling will be performed <br /> and the human health risk potential reported. DLA should conduct the modeling and <br /> estimate the risk concurrently with the CPT/HPT investigation work and present the <br /> results with recommendations in the investigation Technical Memorandum. For the <br /> purpose of modeling, DLA should assume that liquid-phase petroleum hydrocarbons are <br /> floating on the water table beneath <br /> Building 255. <br /> If you have any questions, please contact me at (916) 464-4675, or by email at <br /> jbrownell@waterboards.ca.gov. <br /> James I. Brownell, P.G. <br /> Engineering Geologist <br /> cc: Mr. Phillip Ramsey, USEPA Region 9, San Francisco <br /> Mr. Peter MacNicholl, DTSC Region 1, Sacramento <br /> Mr. Harlin Knoll, San Joaquin County Health Department, Stockton <br /> Mr. Charles O'Neill, engineering-environmental Management Inc., Rancho Cordova <br /> Mr. Brian Renehan, AFCEE, San Antonio, Texas <br /> Mr. David Hofmann, Booz Allen Hamilton Inc., San Antonio, Texas <br />