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k <br /> ' be calibrated using calibration gas The results of this screening will be used for selection of <br /> representative samples for laboratory analysis, and as data for determining the boring depth <br /> ' All soil samples will be described in the field Field observations noting sediment type, color, <br /> grain size, sorting, hardness, texture, clay content, moisture content, visible evidence of <br /> contamination, odor, and any other information important to the investigation <br /> ' These soil sampling procedures are designed to <br /> • ensure that representative soil samples are collected and accurately described in the field <br /> • ensure that all boring logs, sample descriptions, and field observations are consistent and <br /> ' accurate <br /> • minimize the risk of cross-contamination between samples <br /> 3.3 Well Water Sampling Procedures <br /> Prior to sampling of monitoring or other wells, the water level will be measured and the wells will <br /> be purged of three to five casing volumes or until well is dry Bailers or submersible pumps used <br /> M for purging will be thoroughly cleaned before and between samples, or disposable bailers may <br /> used The amount of casing volume of water in the well can be calculated with the formula <br /> r2 X(h I - h2) X 7 48 gallons/ft3 = gallons/casing volume, where <br /> ' r= inner radius of casing (ft) <br /> hi = depth of well (ft) from top point measurement (normally from <br /> reference mark in casing) <br /> ' h2 =depth to water (ft) from to of point of measurement(POM) <br /> 1 <br /> i1 <br /> • <br /> American Geological Services, Inc. <br /> 4 <br />