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Page 5 of 14 <br />SOP NUMBER 0.0 Monitor Well Groundwater Sampling <br />• Measure (to nearest 0.01 foot) and record depth of static water level from the measuring point <br />on the well casing and indicate time as per SOP No. "". Record what the measuring point is <br />(e.g., notch on north side, top of PVC well casing). <br />• Measure and record total depth of well from the same measuring point on the casing. <br />Calculate volume of water in the well casing in gallons based on feet of water and casing <br />diameter (see Section 4.4.3 for calculation of volumes). <br />• From the above calculation, calculate the three casing volumes to be evacuated. <br />During well evacuation, the following procedures are to be performed: <br />• If evacuating the well using a pump, determine flow rate of pump in gallons per minute using <br />the 5- gallon bucket (e.g., 5 gallons in 30 sec. =10 gallons /min.) Divide the total volume <br />(gallons) by the flowrate (gallons /minute) to obtain the number of minutes to evacuate three <br />casing volumes. If evacuating using a bailer, empty contents of the bailer into a 5- gallon <br />bucket to measure cumulative volume of water bailed. <br />• Obtain an initial sample from the bailer or discharge hose of the pump for field <br />measurements (temperature, specific conductivity, dissolved oxygen, oxidation- reduction <br />potential, and pH measurements) and observation of water quality. <br />• Evacuate three volumes of water in casing. Take and record temperature, specific <br />conductance, and pH measurements after evacuation of each well volume to confirm that the <br />water chemistry has stabilized. Generally, pH values within +0.0 pH, temperature within 1 °C <br />and conductivity within +10 percent between three consecutive readings indicate good <br />stability of the water chemistry. If the chemistry is not stable after 3 well volumes, continue <br />evacuating, measuring pH and specific conductance after each one -half well volume until <br />adequate stability is reached. If parameters don't stabilize after 5 casing volumes then <br />discontinue purging and obtain sample. <br />• 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 />• Monitor discharge rate and maintain a steady flow if using a pump. <br />• If the well is pumped or bailed dry during evacuation, it can be assumed that the purpose of <br />removing three well volumes of water has been accomplished, that is, removing all stagnant <br />water that had prolonged contact with the well casing or air. Samples should be obtained <br />after the well has recovered (80 %). If recovery is very slow, samples may be obtained as <br />soon as sufficient water is available to collect required parameters. <br />4.1.6 Collect Groundwater Samples <br />Collect groundwater samples for chemical analysis within two hours after evacuation is <br />completed. Both filtered and unfiltered samples will be collected (see SOP *°, Field Filtration of <br />Water Samples). For slow recovering wells, the sample shall be collected immediately after a <br />sufficient volume is available. Samples should be collected with a decontaminated stainless steel <br />0 -5 <br />