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r <br /> 1419 Charter, Stockton <br /> Stefanos Gasoline <br /> Page 2 <br /> sand unit from 114 feet bsg to 119 feet bsg. This is in agreement with the data log of CPT- <br /> 1,which indicated the presence of a sand unit from 57 feet bsg to 62 feet bsg, and a sand <br /> unit from 114 feet bsg to 120 feet bsg. <br /> Wright proposed in Monitoring Well Installation Workplan, dated April 24, 2003,installing 3 <br /> groundwater sampling wells screened from 5$ feet bsg to 63 feet bsg off site to,2 the east to <br /> investigate the groundwater contamination in the sand layer found at about 60 feet bsg, and <br /> one deep monitoring well screened at 114 feet bsg to 119 feet bsg to investigate the <br /> groundwater contamination in the sand layer found at about 115 feet bsg. Due to the <br /> possible presence of sand-filled former stream channels, EHD and Wright agreed that an <br /> additional 3 CPT borings should be advanced'to obtain a more detailed profile of the <br /> lithological distribution before installing the proposed monitoring wells. EHD.also <br /> recommended installing at least one additional deep screened monitoring well to assess the <br /> vertical extent of the TPH-g and 1,2-DCA contamination found in the two deep sand units. <br /> EHD recommended you look into multi-chambered monitoring well technology as a cost- <br /> effective alternative due to the need to monitor multiple sandy intervals. Submit a work plan <br /> addendum to EHD by June 27, 2003. <br /> Interim remediation such as groundwater extraction or ozone injection as discussed in the <br /> letter dated January 2003 from EHD remains'a viable option to begin reducing the <br /> contaminant mass, control groundwater plume migration, and ultimately help expediate the <br /> site toward closure. If you still wish to pursue interim remediation, submit a work plan / <br /> feasibility test proposal,including justifications, to EHD as previously discussed in the <br /> above-mentioned letter. <br /> If you have an questions, lease contact effre Won at 209) 468-0335. <br /> Y any P J Y g � <br /> Donna Heran, REHS, Director 0 <br /> C .�'. <br /> JePfrey#ong, Senior REHS Nuel C. Henderson,Jr.,R <br /> LOP/Site Mitigation Unit IV FLOP/Site Mitigation,Unit N k <br /> C: RWQCB, Central Valley Region—James Barton <br /> C: Wright Environmental Services, Inc. —John Lynch / Chris Palmer <br /> w <br />