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' 03 April 2002 <br /> AGE-NC Project No. 97-0333 <br /> ' Page 11 of 12 <br /> ' 4.4. EQUIPMENT DECONTAMINATION <br /> All down-hole drilling and sampling equipment will be pressure washed prior to starting eachboring. <br /> 1 <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 /> ' <br /> RWQCB guidelines(Tri-Regional Water Quality ControlBoardRecommendationsfor Preliminary <br /> 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 a Solinst battery operated water level indicator.Water level data will be recorded to the nearest <br /> ' 0.01 foot from a reference point marked on the top of each PVC well casing. Before and after each <br /> use, the 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 with <br /> a 3/8-inch teflon tube bailer and Watera-Hydro-Lift lI pump to ensure that the sample is <br /> representative of the surrounding aquifer ground water.The well will be purged until: 1)a minimum <br /> of three casing volumes is removed from the well; and/or 2) the field-measured ground water <br /> parameters have stabilized. However, if the well is purged dry prior to evacuating three casing <br /> volumes, a ground water sample will be collected following 80 percent recovery of ground water <br /> ' within the well or within 24-hours of well evacuation. <br /> ' 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 /> Advanced GeoEnvironmental,Ine. <br /> 1 <br />