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BV = (7 48/4) x (CD2+P (BD2-CD) 2) x (WD-GW) <br /> BV borehole volume (gallons) BD borehole diameter(feet) <br /> CD casing diameter(feet) WD well depth (feet) <br /> GW depth to groundwater(feet) P porosity of the gravel pack, 25% <br /> Table of Common Boring and Casing Diameters <br /> Boring Casing Volume 3 VolumesX (WD-GW) <br /> diameter diameter gallons/foot gallons/foot <br /> inches inches <br /> 4 1 0 042 0 126 <br /> 6 1 0 082 0 246 <br /> 6 2 0 173 0 519 <br /> 8 2 0 277 0 831 <br /> 8 4 0 671 2013 <br /> 10 2 0 572 1 716 <br /> 10 4 0 844 2 532 <br /> EXAMPLE An 8 inch boring with 2 inch casing requires removal of 0 831 gallons of <br /> water per foot of water column <br /> The water collected during purging is either safely stored on- site in 55 gallon DOT 17H <br /> drums for later disposition, transported to an approved on-site/off-site treatment facility <br /> or to a sewer discharge system <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 <br /> purging, if 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 <br /> the analyses needed or required The water samples are decanted from the bailer into the <br /> appropriate number and size containers These containers are furnished pre-cleaned to <br /> exact EPA protocols, with and without preservatives added, by the analytical laboratory <br /> or a chemical supply company The bottles are filled, with no headspace, and then <br /> capped with plastic caps with teflon liners <br /> The vials or bottles containing the groundwater samples are labeled with site name, <br /> station, date, time, sampler, and analyses to be performed, and documented on a chain of <br />