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PES Environmental,Inc. <br /> Ms. Emily Cushman <br /> November 4, 2016 <br /> Page 2 <br /> Monitoring Well Installation and Groundwater Sampling <br /> Using the groundwater data from the initial and supplemental grab groundwater investigations, <br /> PES will select approximately 6 locations for installation of groundwater monitoring wells <br /> within, and around, the hydrocarbon-affected area. The proposed locations of these wells, <br /> which will be used to monitor impacts to groundwater, evaluate hydrogeologic conditions and <br /> assess effects of tidal fluctuation to localized groundwater direction and gradient, if any will be <br /> provided to the Central Valley Regional Water Quality Control Board (Board) for concurrence <br /> prior to installation. <br /> Monitoring Well Installations <br /> Borings for the groundwater monitoring wells will be drilled using a hollow-stem auger drill <br /> rig with oversight by a PES geologist or engineer. The monitoring wells will be installed <br /> using 8-inch diameter hollow-stem augers. The shallow monitoring wells will be drilled to a <br /> terminal depth of approximately 20 to 25 feet below ground surface. The depth of the shallow <br /> groundwater monitoring wells may be modified based upon field observations, including well <br /> location in reference to the existing levee, lithology encountered, depth to groundwater at time <br /> of drilling, etc. <br /> A PES geologist or engineer will supervise the drilling and well construction activities, and <br /> prepare a lithologic log of the boring using the Unified Soil Classification System. Soil <br /> samples will be retrieved for lithologic characterization from the borehole at 5-foot intervals <br /> using a California-Modified split-spoon sampler advanced beyond the tip of the lead auger. <br /> Additionally, soil samples will be screened in the field periodically for the presence of VOCs <br /> based on headspace analysis using a portable photo-ionization detector (PID) equipped with a <br /> 10.2eV photo-ionization lamp. PID readings will also be recorded on the field lithologic log. <br /> Soil cores collected during the investigation will be contained in Department of Transportation <br /> (DOT)-approved 55-gallon drums pending offsite disposal or recycling. Representative <br /> samples of the investigation derived waste (IDW) will be collected and submitted to a <br /> laboratory for analysis. <br /> Upon reaching the desired depth interval, the monitoring wells will be constructed using <br /> 2-inch diameter schedule 40 polyvinyl chloride (PVC) casing and well screen. The well screen <br /> interval of the groundwater monitoring wells will begin approximately 10 feet to 15 feet bgs <br /> and extend the full depth of each well. The final well screen interval will be based upon <br /> encountered lithology. Wells screens will be constructed with 0.010-inch slots using <br /> No. 2/12 Monterey Sand as a filter pack. The sand filter pack of the shallow wells will be <br /> extended from the bottom of the borehole to approximately 2 feet above the top of the well <br /> screen. <br /> 148400101woo5.dmx <br />