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21 March 2003 <br /> AGE-NC Project No. 95-0114 <br /> Page 9of10 <br /> of fine-grained sediment. Developmental purging activities will be continued until field parameter <br /> (pH, electrical conductivity, and temperature)readings have stabilized and purged water is visually <br /> sediment-free. <br /> 4.3. EQUIPMENT DECONTAMINATION <br /> All sampling tools used for sample collection will be thoroughly rinsed with clean water after being <br /> washed with a solution ofAlconox.Prior to each use all down-hole drilling and sampling equipment <br /> will be pressure washed prior to starting each boring. <br /> 4.4. GROUND WATER MONITORING PROCEDURES <br /> Groundwater sample collection will be performed in accordance with EHD guidelines(San Joaquin <br /> County Public Health Services Environmental Health Division Well Standards)and the CVRWQCB <br /> guidelines (Tri-Regional Water Quality Control Board Recommendations for Preliminary <br /> Investigations and Evaluation of Underground Storage Tanks) sampling protocols. <br /> 4.4.1. 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 Teflon well casing. Before and after each use, the <br /> measurement device will be washed with a solution of Alconox and rinsed with clean water. <br /> 4.4.2. Well Evacuation <br /> Subsequent to measurement of depth to water and prior to sampling, each well will be purged by <br /> inserting a 3/8-inch outer diameter polyethylene hose equipped with a ball-valve water tip(liftbailer) <br /> through the selected well chamber into the specific water-charged screened interval and oscillating <br /> the tube vertically to lift the water. The well will be purged until: 1) a minimum of three casing- <br /> water volumes is removed from the well;and/or 2)the field-measured ground waterparameters have <br /> stabilized. However, if the well is purged dry prior to evacuating three casing-water volumes, a <br /> ground water sample will be collected following 80 percent recoveryof ground water within the well <br /> or within 8 hours of well evacuation. <br /> Advanced GeoEnvironmental,Inc. <br />