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Well Sampling Pumps <br /> EMCON recommends that dedicated pumps be installed in all wells <br /> following well construction completion. The benefits associated with <br /> permanently installing these pumps are (1) reduced field time for well <br /> purging and equipment cleaning and (2) eliminating the potential for <br /> cross-contamination. The type of pumps installed will be determined <br /> based on pumping characteristics of the wells. Based on experience <br /> gained from Well MW-1, a low-yield formation is anticipated. If this <br /> is consistent in the new wells, it is likely that EMCON will recommend <br /> positive displacement bladder pumps. <br /> Well Purging <br /> Before sampling, standing water in the casing and sand pack will be <br /> purged from the well . The amount of water purged will be greater than <br /> or equal * to four casing volumes so that water representative of the in <br /> situ ground water is obtained. Some wells may be pumped dry before <br /> the removal of four casing volumes. If this occurs, the wells are <br /> allowed to recharge up to 24 hours. For parameters sensitive to <br /> volatilization, samples will be collected as soon as the wells have <br /> recharged to a level sufficient for sample collection. For the <br /> remaining parameters, samples will be collected within 24 hours of <br /> evacuation to dryness. If a well has not recharged within the 24-hour <br /> period, it will be recorded as dry for the sampling event. <br /> During the purging operation, purged water will be monitored at an <br /> approximate frequency of one set of measurements per casing volume <br /> removed for. temperature, pH, and specific conductance. Prior to <br /> collecting samples for laboratory analysis, these parameters must be. <br /> stabilized to verify that a representative sample will be collected; <br /> that is, two consecutive sets of field measurements must be similar. <br /> Purged water is stabilized when (1) pH is within j0.5 pH units, <br /> (2) conductance is within 5 percent, or (3) temperature is within <br /> 1.0OF. All records of the above data will be kept in a waterproof <br /> PJ9 9390313.00D B-5 <br />