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piled soil is stored on site, or tank excavation work is in progress.; <br /> Ambient conditions blanks are collected by filling sample containers in the field with <br /> analyte-free water obtained from the laboratory. The water is poured directly from the <br /> storage container into the sample vials, with the only contact being ambient air. <br /> Field Duplicate Samples <br /> A field duplicate sample is a second sample collected independently at a sampling <br /> location during a single act of sampling. Duplicates are collected to assess the <br /> accuracy of sampling procedures. Gettler-Ryan collects field duplicate samples at a <br /> rate of one duplicate per ten water samples, or as specified by the client. The % RPD <br /> calculated for field dupicates arise from two sources of uncertainty: normal analytical <br /> uncertainty and sample collection uncertainty, which includes sample heterogeneity. <br /> Thus, % RPD calculated for the field duplicate cannot be assessed by the same criteria <br /> established for the analytical precision assessment. <br /> Preventive Maintenance <br /> Equipment, instruments, tools, gauges and other items requiring preventive <br /> maintenance will be serviced in accordance with each manufacturer's specified <br /> recommendations and/or written procedures developed by the operators. Preventive <br /> maintenance for all equipment includes inspection before use, cleaning as necessary <br /> during use, and thorough cleaning and inspection after use. Equipment failures are <br /> repaired in the field, if possible, or equipment is returned to the manufacturer for repair <br /> or replacement. In the absence of manufacturers' recommended maintenance criteria, <br /> a maintenance procedure will be developed by the operator based upon experience <br /> and previous use of the equipment. <br /> Section 3.0 Sampling Procedure, Sample Containers, Sample Handling <br /> Water-level Measurements <br /> Prior to purging and sampling a well, the static-water level, free-product thickness, and <br /> total well depth are monitored using an electronic sounder or calibrated portable <br /> oil/water interface probe. Both static water-level and separate-phase product <br /> thickness are measured accurate to the nearest 0.01 foot. The presence of separate- <br /> phase product is confirmed using a clean, acrylic or polyvinylchloride (PVC) bailer, <br /> measured to the nearest 0.01 foot with a decimal scale tape. <br /> Well Purging <br /> Prior to sampling, well casing water and interstitial water in the artificial sand pack is <br /> purged using 1) a positive displacement bladder pump constructed of inert, Teflon and <br />