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t <br /> 24 September 1999 <br /> AGE-NC Project No. 96-0232 <br /> ' Page 10 of 12 <br /> ' 4.1.4. EQUIPMENT DECONTAMINATION <br /> All sampling tools used for sample collection will be thoroughly rinsed with clean water after being <br /> ' washed with a solution of Alconox. All down-hole drilling and sampling equipment will be pressure <br /> washed prior to starting the boring. <br /> t4.2. GROUND WATER MONITORING PROCEDURES <br /> ' Groundwater sample collection will be performed in accordance with PHS-EHD guidelines (San <br /> Joaquin County Public Health Services Environmental Health Division Well Standards) and <br /> ' CVRWQCB guidelines (Tri-Regional Water Quality Control Board Recommendations for <br /> Preliminary Investigations and Evaluation of Underground Storage Tanks) sampling protocols. <br /> 4.2.1. Static Water Level Measurements <br /> Prior to all ground water purging and sampling, static water levels in each well will be measured <br /> using an electric water level indicator. Water level data will be recorded to the nearest 0.01 foot from <br /> ' a reference point marked on the top of each PVC well casing. Before and after each use, the <br /> measurement device will be rinsed with clean tap water. <br /> t4.2.2. Well Evacuation <br /> ' Subsequent to measurement of depth to water and prior to sampling, each well will be purged using <br /> a bailer or submersible pump to ensure that the sample is representative of the surrounding aquifer <br /> ground water. The well will be purged until: 1)a minimum of three casing volumes is removed from <br /> the well; and/or 2)the field-measured ground water parameters have stabilized. However, if the well <br /> is purged dry prior to evacuating three casing volumes, a ground water sample will be collected <br /> following 80 percent recovery of ground water within the well or within 24-hours of well evacuation. <br /> ' 4.2.3. Sample Withdrawal <br /> Water samples will be collected from the monitoring well using a new, pre-cleaned disposable <br /> ' polyethylene bailer. These bailers are disposed of after one use and require no decontaminating, <br /> thereby minimizing cross contamination due to sampling devices. Samples will be drawn and <br /> collected in such a manner that agitation and exposure of the groundwater to the atmosphere is <br /> ' minimal. Sample containers will be filled using the appropriate disposable sampling attachment <br /> Advanced GeoEmironmenlal,Inc. <br />