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Show The second pertinent snow sampling problem is that contamination is a re problem. The collection equipment and materials, personnel vehicles, an analysis facility and personnel must be completely physically separated from any personnel, equipment, or vehicles that are ever used in any Phas of the nuclei or tracer generation process. The results of the first season neutron activation silver analyses were made suspect by contamination, even though what was thought to be adequate safeguards against contamination had been enforced. The sometimes puzzling results of the sample ana yses of other programs can possibly also be attributed to contamination of the . samples at some stage of the procedure. The total material we are loo ing for in several seasons of sampling and tracer experiments is probably less than the dust under one's findernail, so contamination is a very real problem to be rigidly guarded against. Also, care must be taken to guard against pollution or dilution of a sample by blowing or drifting snow. 1 2. 9 Snow Sensor Network The snow sensor network as of the conclusion of the project consisted of eighteen sensor locations as located in Figure 12. The instrumentation co sisted of an optical snow rate sensor which integrates the pulses produced by snow-crystals falling through a light beam-photocell unit. At all but three sites modified weighing bucket gauges -were also used. These consisted of standard weighing gauges with the collection area doubled over the standard eight inch diameter gauge. The weighing bucket sensor with a standard alter type wind shield definite!, tends to underestimate the actual snowfall. Figure 13 is a comparison of the seasonal record of accumulative snowfall as indicated by the weighing bucket snow sensor and the measured special snow course values. After five seasons experience with the complete series of special snow course measurements there is no reason to believe the snow course values are ov estimates of precipitation. Jn fact, they are the most accurate measures o accumulated snowfall available; but the time resolution of the measuremenl does not make them suitable for the determination of a short period snowf total. The USDA Soil Conservation Service (SCS) operated a network of five tele· metered snow pillows and EG&G operated a sixth in support of the project. Also, a network of 25 snow courses were read approximately weekly by thi SCS in support of the project. The network was rounded out by the two existing_ stream gauges with long periods of record, and eight additional gauges mstalled and operated by the U. S. Geological Survey and the USDA Rocky Mountain Range and Forest Experiment Station. During routine operations the network was serviced on approximately a weekly schedule. The optical rate sensors operate more reliably if the batteries are not operated past seven days. Section 2. 9. 1 describes the 26 |