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l , ameO 7.2 SCOPE OF WORK Conceptually, the groundwater remediation pilot test will involve injection of HRC at locations just upgradient of monitoring well cluster MW-5 at three depths corresponding to the depth of the wells in the cluster. The highest concentrations of CVOCs in groundwater are at this location (Figure 6). Proposed I-IRC injection locations are shown on Figure 8. -three injection locations are proposed for each of the three depths of well completions. The direction of groundwater flow at the MW-5 cluster wells is generally to the northeast but may vary to become more easterly at times. The injection locations have been selected such that even if groundwater flow direction varies, at least one injection point should be upgradient at each depth for the corresponding monitoring well. The progress of the remediation in the area being treated will be monitored by sampling the MW-5 well cluster and MW-7 and MW-9 (Figure 6). Wells MW-7 and MW-9 will be used to monitor the affect of the treatment downgradient of the area being treated. Groundwater monitoring will be conducted before the start of the pilot test to determine baseline groundwater chemistry conditions and then for 2 years after the injections to monitor the progress of the remediation and changing groundwater chemistry. The supply of HRC in the aquifer is expected to be exhausted in about 1 to 2 years. Monitoring for 2 years should provide adequate data to evaluate treatment effectiveness and changes in groundwater chemistry in the treated area. Tasks are described below in the approximate order in which they will be conducted. 7.2.1 Pre-Field Work Prior to commencing subsurface work, AMEC will obtain drilling permits for the I-IRC injection borings from the SJCEHD. AMEC will also obtain encroachment and traffic permits from the City of Stockton to work in the city right of way on Hunter Street. At least 2 business days before the injection borings are advanced, AMEC will notify Underground Services Alert. The injection locations will also be cleared by private underground utility locating service. Additionally, each location will be cleared to a minimum depth of 5 feet bgs using a hand auger. 7.2.2 Water Quality Sampling The progress of the pilot test will be monitored by measuring field parameters on samples collected from the MW-5 cluster wells and downgradient wells MW-7 and MW-9 and submitting samples to a laboratory for selected analyses. An initial sampling event will be conducted prior to HRC injection and will include field parameters and laboratory analyses. Groundwater samples will be collected from the three MW-5 wells and measured for field AMEC Geomatrix, Inc. L\13000s\13290Wchive\13290-49.DOC 11