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Mr. Himanshu H. Mehta, P.E. 2 June 2023 Page 5 Geosynteccl consultants statistical analysis, trend analysis graphs showing temporal concentrations of constituents and a summary of the Mann -Kendall statistics will be included to identify increasing, decreasing, or no trends in groundwater constituent concentrations. Historical data summaries will be included for monitoring wells recommended for removal from the monitoring plan. The draft Summer and Winter 2023 reports will be submitted to IRC SWDD for review prior to submittal to FDEP. Each final report will be signed and sealed by a Florida -registered Professional Engineer or Geologist. Phase 6 — Pre-RAPM Addendum No. 4 Iniection Activities:. Upon review of data from 2022 sampling events, elevated concentrations of trichloroethene (TCE), cis-1,2-dichloroethene (cis-1,2- DCE), and vinyl chloride (VC) suggest that reductive dechlorination has slowed significantly in groundwater at the Site, and aquifer conditions (low pH and slightly higher ORP) are less favorable for the occurrence of intrinsic biodegradation. To develop the treatment area that will be presented in the RAPM Addendum No. 4, groundwater samples will be collected in the vicinity of the former source area (near GR-MW30B) and northwest of the former source area (near GR-MW26B) using temporary sampling techniques utilizing a drilling rig. Data from these locations will be used to develop a high resolution CVOC concentration horizontal/vertical profile of the aquifer from which injection intervals will be selected. Prior to the commencement of field sampling activities, Geosyntec will update the site-specific task hazard analysis (THA). Geosyntec will provide oversight for a contractor to clear brush in the former source area and around select well clusters in preparation for drilling rig mobilization and groundwater sample collection. A private underground utility survey of all proposed drilling locations will also be performed prior to the field event. Costs are included for 1 day oversight (with 1 person) and for subcontractor costs. DPT drilling will be used to conduct top-down groundwater sample collection at the proposed 12 locations shown on Figure 1 in the Attachment. Groundwater samples will be collected at 4 -foot (ft) discrete intervals beginning at 10 -ft below land surface (BLS) to 80 -ft BLS (5 samples per location). Groundwater stabilization parameters will be collected during sampling and samples will be submitted to a fixed -base laboratory for analysis of volatile organic compounds (VOCs) by EPA Method 8260B. A continuous soil boring will be advanced in each of the two drilling areas to record site lithology and evaluate mass distribution using a photoionization detector (PID). The proposed discrete groundwater sampling intervals will be selected based upon the area -specific lithologic observations and PID responses from the continuous soil borings. Upon completion at each drilling location, the borehole will be pressure or tremie grouted from total depth to land surface. A geographical positioning system (GPS) will be used to record horizontal coordinates of all drilling locations. Drilling activities are estimated to take 5 field days with 1 person providing oversight. FR0766\XR23010.docx engineers I scientists I innovators