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4 <br /> { <br /> water in a 2 inch well The water is then used to pump the water from the well The usual amount <br /> of water removed is three well volumes, unless othenvise stated <br /> WV= (CD/2)' x (WD-GW)X 7 48 gallons/cubic foot <br /> WV well volume(gallons) CD casing diameter(feet) <br /> WD well depth(feet) GW depth to groundwater(feet) <br /> Table of Common Casing Diameters <br /> Casing Volume 3 Volumes X(WD-GW) <br /> diameter gallons/ foot gallons/foot <br /> inches <br /> 1 00374 0 112 <br /> 2 0 165 0 494 <br /> 4 0 367 1 10 <br /> Collection of Water Sample for Analysis <br /> The groundwater in the well is allowed to recover to at least 80% of its volume prior to purging, if <br /> practical,before the groundwater sample is collected <br /> Percent Recovery=(1 - Residual drawdown) x 100 <br /> Maximum drawdown <br /> A fresh bailer is used to collect enough water for the requirements of the laboratory for the analyses <br /> needed or required The water samples are decanted from the bailer into the appropriate number <br /> and size containers These containers are furnished pre-cleaned to exact EPA protocols, with and <br /> without preservatives added, by the analytical laboratory or a chemical supply company The <br /> bottles are filled, with no headspace, and then capped with plastic caps with teflon liners <br /> The vials or bottles containing the groundwater samples are labeled with site name, station, date, <br /> time, sampler, and analyses to be performed, and documented on a chain of custody form They <br /> are placed in ziplock bags and stored in a chest cooled to 4 °C with ice The preserved samples are <br /> COC (chain of custody) delivered to the chosen laboratory <br />