2011-08-09_REVISION - M1981185 (56)

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BOP NUMBER 0.0 Page 9 of 14 Monitor Well Groundwater Sampling o Bins for decontamination 4.0.0 Sampling Procedures 4.0.0.1 Pre.sampling Activities 1. Start at the well known or believed to have the least contaminated ground water and proceed systematically to the well with the most contaminated ground water. Check the well, the lock, and the locking cap for damage or evidence of tampering. Record observations. 2. Lay out sheet of polyethylene for placement of monitoring and sampling equipment 3. Remove well cap. 4. If the well casing does not have a reference point (usually a V- cut or indelible mark in the well casing), make one. Note that the reference point should be surveyed for correction of ground water elevations to the mean geodesic datum (MSL). 5. Measure and record the depth to water (to 0.01 ft) in all wells to be sampled prior to purging. Care should be taken to minimize disturbance in the water column and dislodging of any particulate matter attached to the sides or settled at the bottom of the well. 4.0.0.0 Sampling Procedures 1. Install pump: Slowly lower the pump, safety cable, tubing and electrical lines into the well to the depth specified for that well. The pump intake must be kept at least two (0) feet above the bottom of the well (where possible) to prevent disturbance and resuspension of any sediment present in the bottom of the well. Record the depth to which the pump is lowered. 2. Measure water level: Before starting the pump, measure the water level again with the pump in the well. Leave the water level measuring device in the well. 3. Purge Well: Start pumping the well at 000 to 500 milliliters per minute (ml/min) or 0.0 to 0:5 liters per minute (1 /min). The water level should be monitored approximately every five Minutes. Ideally, a steady flow rate should be maintained that results in a stabilized water level (drawdown of 0.3 ft or less from the static level). Pumping rates should, if needed, be reduced to the minimum capabilities of the pump to ensure stabilization of the water level. As noted above, care should be taken to maintain pump suction and to avoid entrainment of air in the tubing. Record each adjustment made to the pumping rate and the water level measured iniinediately after each adjustment. 4. Monitor Indicator Parameters: During purging of the well, monitor and record the field indicator parameters (temperature, specific conductance, pI -I, Eh and DO) approximately every five minutes. The well is considered stabilized and ready for sample collection when the indicator parameters have stabilized for three consecutive readings as follows: +0.1 for pH + 3% for specific conductance (conductivity) +10 my for redox potential + 10% for DO Dissolved oxygen and turbidity usually require the longest time to achieve stabilization. 0 -9