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' 11 June 2001 <br /> AGE-NC Project No. 96-0232 <br /> ' Page 10 of 11 <br /> ' 4.5. 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 /> 4.5.1. 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 /> ' 4.5.2. Well Evacuation <br /> ' Subsequent to measurement of depth to water and prior to sampling, each well will be purged using <br /> a teflon tube bailer or peristaltic pump to ensure that the sample is representative of the surrounding <br /> t aquifer ground water. The well will be purged until: 1) a minimum of three casing volumes is <br /> removed from the well; and/or 2) the field-measured ground water parameters have stabilized. <br /> However, if the well is purged dry prior to evacuating three casing volumes,a ground water sample <br /> ' will be collected following 80 percent recovery of ground water within the well or within 24-hours <br /> of well evacuation. <br /> 1 4.5.3. Sample Withdrawal <br /> ' Water samples will be collected from multi-level monitoring wells using new, pre-cleaned <br /> disposable teflon tubing and a peristaltic pump. The tubing will be disposed of after one use and <br /> require no decontaminating, thereby minimizing cross contamination due to sampling devices. <br /> Samples will be drawn and collected in such a manner that agitation and exposure of the <br /> groundwater to the atmosphere is minimal. <br /> ' 4.5.4. Sample Handling <br /> ' Ground water samples will be collected into laboratory supplied containers. Ground water samples <br /> will be collected into 40-m1 VOA vials containing 0.5-m1 of hydrochloric acid as preservative and <br /> ' Advanced GeoEnvironmental,Inc. <br />