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Page 10 of 141 <br />SOP NUMBER 0.0 Monitor Well Groundwater Sampling <br />5. Field measurement meters (pH/temperature, specific conductivity, dissolved oxygen, and <br />oxidation- reduction potential) must be calibrated each day. Calibration and operation should <br />follow the manufacturer's specific instructions and SOP **, Field Parameter Measurements <br />(including Instrument Calibration). <br />6. Collect Samples: Collect samples at a flow rate between 100 and 050 mL /min and such that <br />drawdown of the water level within the well does not exceed the maximum allowable <br />drawdown of 0.3 ft. VOC samples must be collected first and directly into sample containers. <br />VOC samples should be collected at a flow rate of 0.1L/min or less. All sample containers <br />should be filled with minimal turbulence by allowing the groundwater to flow from the tubing <br />gently down the inside of the container. <br />7. Collect QA/QC Samples: using procedure in 10. (also refer to section 4.0.5). <br />8. Remove Pump and Tubing: After collection of the samples, the tubing, unless permanently <br />installed, must be properly decontaminated or dedicated to the well. <br />9. Close and lock well. <br />4.0.3 Addressing Potential Problems <br />Problems that may be encountered using this technique include. <br />o Difficulty in sampling wells with insufficient yield. <br />• Failure of one or more key indicator parameters to stabilize. <br />• Cascading of water and /or formation of air bubbles in the tubing. <br />• Cross - contamination between wells. <br />Wells with insufficient yield (i.e., low recharge rate of the well) may dewater dtiring purging. <br />Care should be taken to avoid loss of pressure in the tubing line due to dewatering of the well <br />below the level of the pump's intake. Purging should be interrupted before the water level in the <br />well drops below the top of the pump, as this may induce cascading of the sand pack. Pumping <br />the well dry should therefore be avoided to the extent possible in all cases. Sampling should <br />commence as soon as the volume in the well has recovered sufficiently to allow collection of <br />samples. <br />If one or more key indicator parameters fails to stabilize after 4 hours, one of four options should <br />be considered: <br />• Continue purging in an attempt to achieve stabilization <br />• Discontinue purging, do not collect samples, and document attempts to reach stabilization in <br />the field book. <br />• Secure the well, purge and collect samples the next day (preferred). <br />To prevent cascading and /or air bubble formation in the tubing, care should be taken to ensure <br />that the flow rate is sufficient to maintain pomp suction. Minimize the length and diameter of <br />tubing (i.e., % or 3/8 inch ID) to insure that the tubing remains filled with groundwater during <br />sampling. <br />0 -10 <br />