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Table 1 <br /> Criteria for Stabilization <br /> of Indicator Parameters During Purging <br /> Field Parameter Stabilization Criterion <br /> Dissolved Oxygen 0.10 mg/L <br /> Electrical Conductivity 3% Full Scale Range <br /> PH 0.10 pH unit <br /> Temperature 0.2° C <br /> The method described above is recommended as an alternative to the conventional "three <br /> well volume" purging protocol. Purging until the parameters in Table 1 have stabilized is <br /> a technically sound method for obtaining groundwater samples that are representative of <br /> formation groundwater. Most regulatory agencies accept this newer method based on it's <br /> technical'merits. However, some regulatory agencies may still. require the older "three <br /> well volume" method. For wells completed in very transmissive zones, it may not be <br /> practical to purge at a slow rate with minimal water table depression while still achieving <br /> the required purge volume. In these cases, a higher purge rate may be acceptable <br /> r initially, but purging rates should be decreased as the required purge volume is <br /> approached, with the objective of producing groundwater samples that are not turbid and <br /> have not been artificially aerated. <br /> 2.4 Field Indicator Parameter Measurement <br /> During purging, continuously measure dissolved oxygen, electrical conductance, pH, Eh, <br /> and temperature with the flow cell or container (e.g., large beaker or bucket). If using the <br /> container for measuring the field indicator parameters, direct the discharge into the <br /> bottom of the container and allow the bucket to continuously overflow during <br /> measurements to minimize aeration. Allowing the discharge to pour into the container <br /> will aerate the water and result in nonrepresentative results for critical intrinsic <br /> bioremediation parameters. <br /> Record indicator parameter and water level measurements in a field notebook or onto <br /> well development logs at approximately 114 well volume increments. Purging is <br /> complete once the parameters have stabilized to within the ranges presented in Table 1 <br /> regardless of the number of well volumes. <br /> f <br /> SF010030487.DOC D-3 <br />