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• S E C O R --,� --- <br /> STANDARD PROCEDURE FOR <br /> GROUNDWATER SAMPLING , <br /> n <br /> Depth to Groundwater/LPH Thickness Measurements ;y <br /> Prior to purging each of the wells, the depth to groundwater and thickness of SPH, if present, <br /> within each well casing is measured to the nearest 0.01 foot using either an electronic Solinst ta`' <br /> water level indicator or an electronic oil-water interface probe. Measurements are taken from a <br /> point of known elevation on the top of each well casing as determined in accordance with previous (* <br /> surveys. �s <br /> Groundwater Monitoring Well Purging <br /> Groundwater wells are purged by using a dedicated bailer or a groundwater pump. To help <br /> i <br /> assure that the collected samples are representative of fresh formation water, the conductivity, . <br /> temperature, and pH of the delivered effluent are monitored and recorded using a Cambridge <br /> Hydac meter, or another meter similar in nature during purge operations. Purge operations are <br /> deemed sufficient once successive measurements of pH, conductivity, and temperature stabilize <br /> r <br /> to within +/- 10 percent. � <br /> During purging, a minimum of three (3) well volumes, measured as the annular space of the well <br /> casing below the groundwater surface, are removed from each well. However, in the case of very <br /> slow recharging wells, purging is deemed sufficient if the well contents are completely evacuated <br /> during purge operations. Unless recharge takes more than two hours, wells are sampled once ; <br /> the well is recharged to within in 80 percent of the pre-purge groundwater elevation. For veryR ' <br /> slow recharging wells (wells pumped d rydurin <br /> g purging), samples may be collected after 2 hours <br /> of recharge. 9 <br /> Groundwater Sample Acquisition, Handling, and Analysis <br /> Following purging operations, groundwater samples are collected from each of the wells using , <br /> pre-cleaned, single-sample polypropylene, disposable bailers. The groundwater sample is <br /> discharged from the bailer to the sample container through a bottom emptying flow control valvev. a <br /> to minimize volatilization. <br /> Collected water samples are discharged directly into laboratory provided, pre-cleaned, ' <br /> hydrochloric acid-preserved and unpreserved 40 milliliter (ml) glass vials and sealed with Teflon- <br /> lined septum, and screw-on lids for analysis of TPH GRO, TPH DRO, BTEX, and MtBE by EPA4 <br /> Method 8260B. <br /> l!S-s,kFe <br /> E h <br />