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Appendix C <br /> Page 1 <br /> STANDARD PROCEDURE FOR <br /> GROUNDWATER SAMPLING <br /> Depth to Groundwater/LPH Thickness Measurements <br /> Prior to purging each of the wells, the depth to groundwater and thickness of liquid <br /> phase hydrocarbons, if present, within each well casing is measured to the nearest 0.01 ft <br /> using either an electronic Solinst water level indicator or an electronic oil-water interface <br /> probe. Measurements are taken from a point of known elevation on the top of each well <br /> casing as determined in accordance with previous surveys. <br /> Groundwater Monitoring Well Purging <br /> Groundwater wells are purged by using a dedicated bailer or a groundwater pump. To <br /> help assure that the collected samples are representative of fresh formation water, the <br /> conductivity, temperature, and pH of the delivered effluent are monitored and recorded <br /> using a Cambridge Hydac meter or another meter similar in nature during purge <br /> operations. Purge operations are deemed sufficient once successive measurements of <br /> pH, conductivity, and temperature stabilize to within +/- 10 percent. <br /> During purging, a minimum of three (3) well volumes, measured as the annular space of <br /> the well casing below the groundwater surface, are removed from each well. However, <br /> in the case of very slow recharging wells, purging is deemed sufficient if the well contents <br /> are completely evacuated during purge operations. Unless recharge takes more than <br /> two hours, wells are sampled once the well is recharged to within in 80 percent of the <br /> pre-purge groundwater elevation. For very slow recharging wells (wells pumped dry <br /> during purging), samples may be collected after 2 hours of recharge. <br /> Groundwater Sample Acquisition, Handling, and Analysis <br /> Following purging operations, groundwater samples are collected from each of the wells <br /> using pre-cleaned, single-sample polypropylene, disposable bailers. The groundwater <br /> sample is discharged from the bailer to the sample container through a bottom emptying <br /> flow control valve to minimize volatilization. <br /> Collected water samples are discharged directly into laboratory provided, pre-cleaned, <br /> hydrochloric acid-preserved and unpreserved 40 milliliter (mQ glass vials and sealed with <br /> Teflon-lined septum, and screw-on lids for analysis of total petroleum hydrocarbons for <br /> gasoline range organics, methyl tertiary butyl ether, and benzene, toluene, <br /> ethylbenzene, total xylenes, and 5 fuel oxygenates by EPA Method 82606. Collected <br /> 5 Stantec <br />