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1 BCR & Associates, Ltd Rcrv02 05,94 Standard Procedure 5 1 Purging and Sampling Groundwater Monitoring Wells See Site Health and Safety and Equipment Decontamination 1 Well Pure The purpose of well purging is to remove stagnant water from the well casing and to provide representative formation water for laboratory analysis In theory, one WELL BORE volume should suffice for this purpose In practice, it is difficult to instantaneously evacuate one such volume and replace it completely 1 with formation water without mixing stagnant and fresh formation water Since well water is removed during purging gradually over time, the measurement of CASING volummes and specific parameters has become the "industry" standard for determining valid purging Typically, the well is purged until temperature, specific conductance and pH have "stabilized " The well will be purged with a decontaminated bailer or centrifugal pump Purge water will be temporarily lawfully stored in accordance with specific site procedures, typically 55-gallon DOT-17H drums are used for this purpose The purge water is monitored for specific conductance, temperature and pH The unit will be calibrated on site for pH, and temperature, and will be adjusted on site to match well water temperature Typical units are factory conductance calibrated Where temperature fluctuates rapidly due to the differential between formation water temperature and ambient atmospheric, this condition will be recorded Initial cloudy water will be monitored and recorded once each casing volume Purging will continue until the water clears and three successive bailers indicate pH units witlun one standard unit (i e 1/10) and specific conductance is within 1% Temperature stabilization often cannot be determined accurately, as noted above The readings are measured and recorded in the Monitoring Well Purge and Sample Field Form, and samples collected Low-Yield Formations Where formation yield is low, the well may be bailed or pumped dry The duration of purging, and the quantity of water removed is recorded The well may be sampled when the water level in the well has recovered to 85% of the static level Groundwater Sam lin Samples for volatile analysis are collected by disposable, factory cleansed and sealed bailors and are contained in pre-cleaned 40-m1 VOA vials provided by the analytical laboratory The VOA are checked in the field for headspace or air bubbles If these occur, another sample is collected Semi-volatile and metal-analysis samples are collected, filtered, if necessary, and contained according to the specific method appropriate for that analysis The samples are assigned a unique identification including the well name, date and time of collection, samplers initials, and site address The sample is recorded on the chain-of- custody and immediately placed on ice in an iced cooler for transport to the laboratory I s