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1419 Charter Way <br /> Former Stefano's Gas Station <br /> Page 3 <br /> 1. A site conceptual model including a concentration contour map of the <br /> contamination plume defined so far, cross-sections of the plume and site geology, <br /> nearby well receptors,groundwater migration routes, and a review of the geology in <br /> the area pertaining to the proposed groundwater extraction. Discuss the targeted soil <br /> physical characteristics,how these factors affect the fate and transport model of the <br /> dissolved plume,and how they favor one type of technology versus another. <br /> 2. A description of the relevant physical characteristics of the chemicals targeted for <br /> remediation such as Henry's Law Constant, solubility,vapor pressure, and <br /> adsorption factor, etc., and how they behave in both dissolved phase as well as <br /> residual soil phase. Effort should be ' to justify groundwater extraction as the <br /> appropriate choice for interim remediation over other technologies. <br /> 3. Discuss the objectives of the groundwater extraction feasibility test, the scale of the <br /> extraction test,and the number of additional observation piezometers needed for the ' <br /> test. <br /> Please be aware that groundwater extraction may not necessarily be the most appropriate <br /> remediation technology. EHD welcomes interim remediation efforts to begin reducing the <br /> contaminant mass;however,if sorption of the chemicals relative to the targeted soil is high, <br /> or the chemicals have a high dispersion coefficient, the time required to remove the mass by <br /> groundwater extraction may be very long and the volumes of water needed to be removed <br /> very high. Other technologies such as ozone injection should also be evaluated. <br /> If you have any questions,please feel free to contact Jeffrey Wong at (209) 468-0335. <br /> Donna Heran, REHS,Director <br /> Environmental Health Department <br /> C, <br /> Jeffrey Wong, Senior REHS Nuel C: Henderson,Jr., RG <br /> LOP/Site Mitigation Unit N LOP/Site Mitigation,Unit N <br /> C: RWQCB, Central Valley Region—James Barton <br /> r M: <br /> C: Wright Environmental Services, Inc:` <br /> C; Ramage Environmental—Joe Ramage <br /> _ E. <br />