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IMM ' 4.0 Water Sampling At the time of water sampling, the wells will first be checked for the existence of a floating product layer by the use of an oil-water indicator paste spread on the end of a weighted tape measure. If the paste indicates product is present, its thick- ness will be measured from the oil-water paste, and the depth to product and depth to water will be recorded. Regardless of the presence or absence of detectable floating product, the total petroleum hydrocarbons sample will. then be collected. The sample will be obtained using a clean, transparent teflon bailer lowered into well using new, clean monofillament line until the bailer is partially submerged. The bailer will be retrieved and inspected for visual confirmation of the oil-water paste results and its contents will be poured into the appropriate sample container. It may be necessary to lower the bailer more than once in order to obtain enough water to satisfy the analytical method . require- ments. Once the total petroleum hydrocarbons sample has been collected, the total well depth will be verified. In conjunction with the depth to water measurement, the volume of standing water in the well and the required purge volume will be calculated and record- ed on a standardized well sampling log sheet. It is proposed to purge three standing well casing volumes with a 3 inch submers- ible pump prior to collection of the water samples. The pump will be thoroughly cleaned prior to use with a high pressure potable water spray rinse, and will be cleaned after each well is purged in the same fashion. in the last moments of well purging, the pH, temperature, and conductivity of the water will be measured and recorded. A record of the *urging activities, including the volume of water purged, the jump discharge rate, and the start and finish time of purging will be maintained in the field log book and on the sample log sheet. Well yield as determined during development will control place- ment of the pump during purging. If the well yield is greater than the pump discharge rate, then the pump will be placed near the top of water column in the well. If the pump discharge rate is greater than the well yield, then the pump will be placed about mid-height in the well water column, such that, the water level in the well is drawn down to the pump intake. For low yield wells, it may be necessary to install a flo: ccntrol valve on the pump discharge line. Once the wells have been purged, the pump will be pulled from the well. Provided no measurable floating product was observed, water samples will be collected by lowering a conventional *teflon bailer into the well as soon as practical after purging. If floating product was measured, a "thief" bailer will be used for sample collection. The bailer will be lowered into each - - well using- ew clean--monofillamantIne:f---This-1zne will notbe reused _ between wells. Water collected in the bailer will be - 4 -