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e <br /> 1419 E Charter Way <br /> Page 2 of 2 <br /> + Between October 2005 and August 2006 the ozone system was operational; however, <br /> groundwater sample results reported in quarterly groundwater monitoring reports do not <br /> demonstrate a significant influence from the ozone system. <br /> • The ozone sparge points are set in sand twelve feet below the monitoring wells with fine- ' <br /> grained soil between the sparge points and the monitoring wells. There is no monitoring <br /> well set in the sand at sixty-two feet bgs to demonstrate contaminants..are present and <br /> responding to the ozone. <br /> • New ozone sparge points should.directly address impacted groundwater in the existing <br /> monitoring wells. <br /> AGE proposes to advance one CPT boring to approximately 100 feet bgs near the northeast comer <br /> of the former dispenser area and collect soil and groundwater samples from an adjacent twin boring <br /> "for the purposes of characterizing lithology, modeling potential contaminant migration pathways <br /> and assessing the vertical extent of hydrocarbon-impacted groundwater." To date, five CPT and <br /> associated adjacent borings have been advanced.at this site and nearby locations. Analytical results <br /> for groundwater samples collected from these adjacent borings indicate groundwater is <br /> contaminated well below 100 feet bgs at depths of 105 feet bgs (CPT-1A-105), 115 feet bgs(CPT- , <br /> 2-115) and 119 feet bgs (CPT-3@115-119'). Historically_groundwater flow direction has been <br /> toward the southeast. EHD will not approve the propose_d CPT boring because-EHD does not <br /> believe the proposed CPT boring, up gradient of the source area and proposed to be advanced only <br /> to 100 feet bgs, will provide adequate additional information to determine the vertical extent of <br /> hydrocaibon-impacted groundwater. If you can provide justification for advancing the CPT boring <br /> at the proposed location and depth; EHD will reconsider its position. <br /> Please respond by October 12, 2007, to EHD's recommendation for installing additional monitoring <br /> wells. If you have any questions regarding this letter, contact Vicki McCartney at (209) 468-9852 <br /> or by email at vmccartneZ(a sicelid.com. <br /> Donna Heran, RENS,Director <br /> Environmental Health Department <br /> Victoria L. McCartney, Senior REHS Nuel C. enderson, Jr., PG <br /> LOP/Site Mitigation Unit IV Engineering Geologist <br /> LOP/Site Mitigation Unit IV <br /> c: Jessica Rugge -AGE <br /> James L.L. Barton,PG -CVRWQCB <br />