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• 29 December 1999 <br /> AGE-NC Project No 98-0465 <br /> Page 8 of 9 <br /> 4 5 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 /> 4 6 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) <br /> 4 6 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 6 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 6 3 Sample Withdrawal <br /> Water samples will be collected from each 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 /> which allows controlled flow out of the bottom of the bailer by lifting the check valve <br /> Advanced GeoEnvironmental,Inc <br />