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Pilot Study Workplan November 7, 2014 Project#54.62583.0001 Page 9 presented in Appendix A, indicates the lithology corresponding to the screen interval consists of primarily of silty sand with some sand and sandy silt. These materials have hydraulic conductivities in the general range of 10-3 to 10'5 cm/s (Freeze and Cherry, 1979). Consequently, it is unlikely that the Cascade® solution could be gravity fed and Cardno ATC proposes to inject the solution under pressure as discussed below. Because of the low conductivity material in the saturated subsurface, groundwater velocity is anticipated to be low. Specifically, using Darcy's Law with conductivities of 10-3 to 10-5 cm/s, an estimated porosity of 0.40, and an averag5e gradient of 0.0014 ft/ft, the groundwater velocity is expected to be in the general range of 8 x 10-3 to 8 x 10" ft/day. Consequently, Cardno ATC proposes to target a small treatment area around MW-3 and will install an observation well nest approximately 10-15 feet directly downgradient of MW-3. 6.2 PILOT TEST OBSERVATION WELL INSTALLATION Prior to conducting the pilot test, Cardno ATC will install an observation well nest approximately 10-15 feet downgradient of MW-3 consisting of two 2-inch diameter monitoring wells nested in a single borehole. The two nested wells will be completed to total depths of 55 and 75 feet bgs with ten and five feet of screen at the bottom of each well, respectively. This will allow for monitoring the influence of Cascade®throughout the water column corresponding to the screened interval of the injection well. The individual wells will be constructed of 2-inch diameter Schedule 40 PVC with 0.010 factory slotted PVC screen followed by blank PVC casing to grade. Each screen interval will have a sand pack consisting of 2/12 Monterey sand from the bottom of the screen to approximately two feet above the screen. The annulus between the screen intervals will be grouted with bentonite chips, and the annulus from two feet above the uppermost screen will have a two to three foot bentonite seal followed by a cement grout mixture to one foot below grade. The wells will be equipped with a steel flush-mount traffic-rated protective cover mounted in concrete. Following installation, the wells will be developed using a surge-and-bail technique. The borehole for the observation well nest will be advanced using a hollow stem auger by a State certified drilling contractor. Soil samples will be collected at intervals of five feet using a 2-inch diameter split-spoon sampler containing three brass tubes. The borehole will be logged using a split-spoon sampler and the lithology of the borehole will be logged by a Cardno ATC field scientist lithology according to the Unified Soil Classification System. The drill cuttings will be containerized and stored on site pending laboratory results and arrangements for disposal. 6.3 BASELINE MONITORING Following installation and development of the nested observation well next, baseline groundwater samples will be collected from each of the wells comprising the observation well nest and from monitoring well MW-3 using low-flow sampling methods. Specifically, a downhole pump will be used to extract groundwater from the middle of the screen interval in each well and the pump tubing will be connected to a flow cell from which field parameters will be measured. Groundwater samples will be collected once field parameters have stabilized. Field parameters will consist of temperature, specific conductance, pH, dissolved oxygen (DO) and oxidation- reduction potential (ORP). Groundwater samples will be submitted to a State certified analytical laboratory for analysis of hexavalent chromium according to EPA Method 7199 and total chromium according to EPA Method 200.7. Additional analytes may be required under the General Order R5-2008-0149. 6.4 PILOT TEST INJECTION AND MONITORING Once the baseline monitoring is completed the injection of Cascade® will proceed. Injection activities will be conducted under the direct supervision of a Cardno ATC field scientist.