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GROUND WATER SAMPLING FOR VOCS
Citation:
Paul*, C J. GROUND WATER SAMPLING FOR VOCS. Presented at USEPA Seminar Series on Vapor Intrusion, San Francisco, Dallas, Atlanta, 12/3-4/02, 01/14-15/03, 02/25-26/03.
Description:
Sampling protocol should be dictated by the sampling objective(s). It is important to obtain representative ground water samples, regardless of the sampling objective(s). Low-flow (minimum draw-down) purging and sampling techniques are best in most instances, particularly for VOCs. Dedicated sampling devices are recommended where feasible. Bailers and suction lift devices (i.e. peristaltic pump) are not recommended for sampling VOCs because of excessive degassing and aeration of the sample. Passive or other alternative methods may be best for certain contaminants or in extremely low permeability formations. Water quality parameters should be monitored during purging to determine when formation water has been accessed and sampling can be initiated. Choose appropriate field instruments to monitor WQPs for the site and monitoring objectives. Monitor the water level in the well during purging to match the recharge rate within the well. Filtration is not recommended for VOCs due to the increased aeration and exposure to the atmosphere of the sample, thereby increasing volatilization. Finally, ensure that samples are preserved and stored properly at 4 C following collection, during shipment, and prior to analysis.