REP21636 - Laserfiche WebLink

Home Browse Search

4 sampling station. The groundwater pump malfunctioned during the sampling trip. It was determined that the pump could not be turned up to its full pumping rate because it was relatively new and still was being broken in. When the pump was turned up to its full pumping rate, the pump would cut out. This lengthened the sampling time required for the groundwater wells. 2.1 Field Measurements Halepaska and Associates used Field Data Collection Sheets, as described in TR-0006 (pg. 5). The collection of all field data in a field notebook may be preferable to the use of these sheets. The information on sheets is easier to alter than information written in ink on bound and numbered pages in a field notebook. Unused portions of the page, and unused pages, are marked with a diagonal line to avoid later entry of information. Any cross-outs or changes should be initialed by the person entering the 5eld irfermation (see Appendix B). The field parameters (pH, temperature, dissolved oxygen and specific conductance) were sometimes not allowed to reach equilibrium before the sample was collected. For well M-13 the pH and specific conductance (SC) measurements did not met the criteria for stabilization (±0.1 pH unit and ±10% in specific conductance). Three measurements of field parameters were taken: pH1=9.29, pH2=9.21, pH3=9.08; SC1=252µS, SC2=282µS, SC3=335µS. The last two pH measurements were within 0.1 pH unit if the measurement are rounded, but more importantly, there is a larger difference between the last two measurements than the first two, indicating that steady state has not been attained. The last two SC measurements were within 17%, not 10%, and again there was a larger difference between the last two SC measurements than the first two, indicating that the field parameters had ;tat yet stabilized. In part, the readings were accepted because of the extreme cold and the fact that it was dark. The method used to check stability of the dissolved oxygen (DO) and pH measurements was to turn the meter off, take a reading, turn the meter off again, take a reading. It would have been more accurate to watch the reading after turning the meter on again to observe whether or not the reading had stabilized. Groundwater wells M-9 and M-13 had at least three casing volumes purged from them before collection of the sample, while only appro~dmately two casing volumes were purged from well M-12. However, the field parameters measurements from well M-12 were within the established stability criteria. Instruments are required to be calibrated at the beginning of each sampling day (TR-0006, pg. 16); in addition, the calibration should be checked after 3-5 samples ate collected and after collection of a sample that differs significantly from the following sample (i.e., after RCG/Hagler, Bailly, Inc.