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a <br /> x <br /> Oft <br /> r <br /> 2.7 GROUNDWATER WIPLING <br /> r <br /> Groundwater samples will be collected from existing monitoring wells. Groundwater <br /> samples will be collected in order, from least contaminated to most contaminated, to lower <br /> the probability of cross-contamination. Field weather conditions at the time of sampling will <br /> f; <br /> be recorded in the field logbook. Groundwater sampling methods discussed below fellow <br /> j procedures described in EPA (1986). <br /> Well PureinQ <br /> The water starling in the well may not be representative of in situ groundwater qu2jity. . <br /> Therefore, it is necessary to purge the well prior to sampling to achieve a representative <br /> sample. Before purging the well, the static water level and hydrocarbon level (if any) will <br /> be measured using an interface probe. After the static level(s) have been measured, a pump <br /> will be lowered down the well and set at a level about one foot from the bottom of the well <br /> screen. <br /> �.., At least three well casing volumes will be purged from the well, unless the well is evacuated <br /> before three volumes have been achieved. If the well is incapable of yielding three well <br /> volumes, the well will be pumped until it has been evacuated, then it will be allowed to <br /> recover. After the well has recovered sufficiently enough for a sample, the sample will be <br /> collected and tested for pH, electrical conductivity (EC), temperature, color, and odor. If <br /> sufficient recovery takes more than two hours, a sample will be collected separately for each <br /> parameter. If the well is capable of yielding three well volumes, then samples will be <br /> collected several times during the purging and tested for pH, EC, and temperature. If these <br /> parameters hive stabilized using the following criteria. pH± 1 unit, EC ± 10% of previous <br /> reading and temperature:k 0.5°C, or after three well volumes have been purged, then a _ <br /> sample will be collected for analysis. If the parameters have not stabilized, then pumping <br /> will continue until five well volumes have been purged, or parameters have stabilized, <br /> whichever comes first. <br /> OMSM01%M123YL 9 <br /> r <br /> r <br />