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<br />0002:8 <br /> <br />future. However, the proposed experimentation will place the technology on much firmer <br />scientific footing. Completion of the CREST program is fully expected to give potential users <br />considerable confidence in winter orographic cloud seeding in the Basin. <br /> <br />Physical investigations will continue throughout the statistical experiment, but at a lesser <br />frequency than during the direct detection phase. Investigations will inciude testing of the <br />statistical design and continuation of studies of cloud and precipitation processes. The physical <br />observations also will monitor proper operational conduct of the randomized program. For <br />example, measurements of ice nuclei concentration will test AgI generator operation. Tracer gas <br />tracking and chemical analysis of snowfall will test proper targeting. <br /> <br />Monitoring all key processes throughout all statistical experimental units is impractical. <br />Aircraft sampling, which would be expensive to carry out throughout every experimental unit, <br />is one limitation. Moreover, heavy airframe icing or severe turbulence will at times preclude <br />aircraft sampling at low levels over the target. Consequently, direct detection experimentation <br />must be limited to a fraction of the total time that orographic clouds are present. However, <br />plausible results from many direct detection experiments will add significant credibility to <br />statistical analysis. The combination of statistical results, backed by physical evidence and <br />numerical model predictions from a subset of the experimental units, will provide the scientific <br />evidence desired from the proposed program. <br /> <br />3.4 Site Selection Process <br /> <br />Two mountain barriers have been tentatively selected for the CREST experimentation: the <br />Grand Mesa of west central Colorado and the Wasatch Plateau of central Utah. Final selection <br />will be made only after appropriate NEPA (National Environmental Policy Act) and public <br />involvement processes are completed. The criteria and procedures used to select these locations <br />as the best experimental sites are discussed in detail in appendix A The experimental areas <br />will be on the eastern half of the Grand Mesa (fig_ 2), and on the Wasatch Plateau in the region <br />between the towns of Fairview and Price (fig. 3). Specific small target areas for direct detection <br />experiments will be chosen during the startup year of the program, in coordination with <br />environmental compliance activities. As discussed in section 4, the well-instrumented target <br />will be no wider than the crosswind extent of 1 to 2 seeding plumes (on the order of 5 km)_ The <br />target's alDng-the-wind dimension will be investigated during the direct detection phase, but <br />will be less than the barrier widths, which are about 25 km_ <br /> <br />Larger areas will be targeted during the follow-on statistical experiments. These areas will be <br />specified as the statistical design is developed. Observations from the direct detection phase, <br />and numerical modeling results, are needed to specifY the exact target areas for the statistical <br />experiments on the Grand Mesa and Wasatch Plateau, respectively. At this time, the target <br />areas are anticipated to be in the range Df500 to 1000 km2_ <br /> <br />Limiting target size will increase association with nearby crosswind and upwind control <br />precipitation gauges, discussed further in section 5, which reduces the experimental duration <br />needed for significant results. A very large target area is not needed to demonstrate cloud <br />seeding effectiveness. However, the specified area must be routinely targeted with appropriate <br />concentrations of seeded ice particles. <br /> <br />15 <br />