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C <br />0 <br />I I <br />0 <br />r <br />C <br />0 <br />n <br />u <br />C <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 />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 ±0.5 pH units, <br />(2) conductance is within 5 percent, or (3) temperature is within <br />1.0°F. All records of the above data will be kept in a waterproof <br />PJ9 9390313.00D <br />