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1 <br />' (3) All measurements should be made within as brief a period <br />' of time as possible, so that temperature or chemical <br />changes will be minimized. <br />' (4) In some cases, the instruments take a certain amount of <br />time to stabilize. This stabilization time should be <br />' noted for each measurement. <br />' (5) Instrument probes should be cleaned with de-ionized water <br />between each sampling station to prevent Bross- <br />' contamination. <br />Prior to sampling, while water is being evacuated from each well, <br />water will be poured into a separate clean vessel to measure the <br />field parameters of pH, specific conductance and temperature. The <br />first sample for field parameter measurement shall be collected <br />after approximately three casing volumes have been removed, and <br />' during the bailing of the first casing volume for low-yileld wells. <br />All instrument probes that come in contact with the saunple water <br />and the measurement vessel will be cleaned between uses by rinsing <br />' with laboratory-provided deionized water. A minimum o,~~wo sets of <br />measurements will be made at each sample location tm evaluate <br />~ ~ whether the parameters have stabilized. Samples will nqt be taken <br />until each of the parameters stabilize. The criteria for <br />stabilization are ± 0.1 pH units, ± 10$ in specific conductance <br />value, and ± 1 °C for temperature. <br />' Replicate measurements will be made a minimum of one time per <br />' sample period in the following manner: <br />(1) collect a sample of water into measurement weasel; <br />(2) measure field parameters; <br />(3) rinse instrument probes in de-ionized water; and <br />(4) re-measure field parameters in same sample. <br />' -16- <br />/ ;~c.e i <br />