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PROPOSAL FOR REMEDIATION SERVICES <br /> MOBIL SERVICE STATION X10-NP4 <br /> �r TRACY, CALIFORNIA <br /> conductance, and depth to groundwater will also be <br /> measured prior to sampling. <br /> After we have assessed the data from this task, and after your <br /> approval, we will initiate discussions with the LHD and the <br /> RWQCB to establish cleanup levels for the site. Additional <br /> monitoring wells may be recommended at this time to further <br /> assess the downgradient extent of groundwater contamination. <br /> After cleanup levels have been established and physical and <br /> chemical properties of this site have been assessed, we will <br /> evaluate applicable remedial technologies, prepare a site <br /> Remediation Work Plan, and after obtaining approval from the <br /> agencies, execute the Work Plan. <br /> Task 2 - Excavate and Dispose of Contaminated Soil <br /> Based on the results of Task 1, Hart Crowser may recommend <br /> excavation and disposal of localized areas at contaminated <br /> soil in order to more rapidly remediate the site. We will <br /> oversee the removal and transportation disposal of <br /> contaminated soil by a licensed waste handling contractor to <br /> an approved facility. <br /> Task 3 - Installation of Enhanced Soil and Groundwater <br /> Treatment System <br /> Based on the results of Task 1, Hart Crowser will execute the <br /> approved Site Remediation Work Plan. Site remediation may <br /> include excavation and treatment of contaminated soils, <br /> treatment of in situ soils, and/or extraction and <br /> treatment of contaminated groundwater. A preliminary <br /> groundwater treatment system, based on the assumed conditions, <br /> is described below. Remediation alternatives are also <br /> discussed below. <br /> A process schematic for the enhanced groundwater recovery and <br /> treatment system is shown on Figure 2. Our remediation plan <br /> includes one groundwater recovery trench and two reinjection <br /> trenches as shown on Figure 1. These trenches are positioned <br /> to provide a hydraulic barrier between the site and Grantline <br /> Road and Tracy Boulevard, and to draw potentially contaminated <br /> groundwater which may have migrated off-site back into the <br /> recovery trench. In the absence of site soil permeability and <br /> percolation data, our estimate of the length and location of <br /> the trenches is based on general soil descriptions and on Hart <br /> Crowser's experience in designing and operating these <br /> remediation systems. The groundwater recovery trench is <br /> approximately 18 inches wide and between 8 and 10 feet deep. <br /> -6- <br />