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Page 4 of 10 <br />SOP NUMBER 8.0 Field Parameter Measurements <br />5.2.3 Dissolved Oxygen Meter <br />The concentrations of dissolved oxygen in groundwater samples provide an indication of the <br />whether aerobic or anaerobic respiration is occurring in an aquifer system. Dissolved oxygen <br />concentrations greater than 1 mg/L are favorable for aerobic respiration. Manufacturer's <br />operating manuals, calibration; maintenance procedures will be followed and documented in the <br />field logbook. General calibration procedures Powertech's on-site equipment is provided in <br />Attachment 1 (Calibration of Powertech Field Instruments. <br />The procedures for using a DO meter are as follows: <br />1. Inspect the membrane before each field use for air bubbles, oily film, and/or holes. If the <br />membrane is defective, it must be replaced and soaked before recalibration in accordance <br />with manufacturer's instructions. <br />2. If the D.O. is measured in a container, rinse the sample container with deionized water and <br />then rinse it three times with the water to be sampled prior to measurement. <br />Read the D.O. meter to the nearest 0.1 mg/l. Record in the field logbook the D.O. <br />concentration and the range setting of the D.O. meter. <br />4. If the D.O. meter is equipped with an operational thermometer, read the water temperature at <br />the time the D.O. is measured. Protect the D.O. probe when not in use to prevent the <br />membrane from drying out or freezing. <br />5. Sampling tools, instruments, and equipment will be protected from sources of contamination <br />before use and decontaminated after use as specified in SOP No. 10.0, Decontamination of <br />Sampling Equipment. <br />QC requirements for D.O. measurements are provided in Section 5.3. <br />5.2.4 Oxidation Reduction Potential Meter <br />Oxidation-reduction potential is measure of the tendency of a solution to donate or accept electrons. <br />ORP is measured in units of milliVolts (mV). The oxidation-reduction potential (ORP) may be <br />measured at the time of sample collection. Manufacturer's operating manuals, calibration; <br />maintenance procedures will be followed and documented in the field logbook. General calibration <br />procedures for Powertech's on-site equipment are described in Attachment I (Calibration of <br />Powertech Field Instruments). <br />Oxidation-reduction potential is measured as follows: <br />1. Rinse the ORP meter probe with deionized water. If the ORP is measured in a container, rinse <br />the sample container with deionized water and then rinse it three times with the water to be <br />sampled prior to measurement <br />2. Dip the electrode'/2 to I-inch into the sample and stir once. The electrode should stabilize <br />within 2 to 5 minutes. When stable, take a reading and record it in the field logbook. Any <br />instability will be noted and recorded. <br />Powertech <br />4/23/2007 <br />Rev SOP 8-1 JAB <br />8-4 <br />R Squared Inc <br />