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anticipated turbidity of the purged groundwater (typically 0 NTUs to 10 NTUs). If the <br />reading varies by more than one unit between calibration checks, the meter will be <br />recalibrated. Multiple physical conditions can cause variations in readings, including <br />bubbles in the sampled water, wet or dirty sample containers, a wet or dirty lens, a wet <br />or dirty optical sensor, or leakage of incidental light into the sample chamber. <br />ď‚·Multiple Sensor Meter (pH, Dissolved Oxygen, Conductivity, Temperature, Turbidity): A <br />multiple sensor meter may be used for multiple parameter measurements during sampling. <br />Calibration is performed prior to initiation of sampling activities, using manufacturer auto- <br />calibration solution. If any of the readings are outside of the manufacturers specifications, <br />the meter will be recalibrated for the parameter outside of the calibration range. Calibration <br />checks are performed daily. <br />Equipment not listed herein will be calibrated according to manufacturers' recommendations <br />and/or generally accepted practice. Calibration procedures will be documented for the project <br />file. Instruments for which calibration cannot be easily checked will be either tested against <br />another instrument of a similar type, or will be returned to the manufacturer for appropriate <br />calibration. If tested against another instrument capable of making the same measurements, <br />variation between instruments must not exceed five percent. If readings vary more than five <br />percent, the instrument will be returned to the manufacturer for calibration. <br />Scheduled periodic calibration of testing equipment will not relieve field personnel of the <br />responsibility of employing properly functioning equipment. If equipment malfunction is <br />suspected, the device will be removed from service, tagged so that it is not inadvertently <br />used, and the appropriate personnel notified so that re-calibration can be performed, or a <br />substitute piece of equipment can be obtained. <br />Equipment Maintenance <br />Maintenance responsibilities for field equipment are coordinated through an instrument <br />technician who is responsible for ensuring that available equipment and instrumentation are <br />ready for use, and that returned equipment is inspected, serviced, and returned to available <br />inventory in a timely manner. Maintenance during use is the responsibility of the field team using <br />the equipment. Calibration logbooks contain information on instrument maintenance, calibration, <br />and repair. A separate logbook is maintained for each instrument. The paperwork includes a <br />detailed listing of the item that was cleaned/replaced, and the make/model/serial number for <br />the particular piece of equipment.