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(Exhibit 12) graphically portray how the problem occurs and what its consequences are. An intelligent decision on the structural alternatives to the proposed Strontia Springs Dam cannot ,be made without a thorough review of those reports. Garstka points out that attempts to avoid the problem by use of fifty-foot-high structures and heated trash racks can only result, at best, in preventing the frazil from adhering to the trash racks so that it can be carried into the tunnel where it can freeze the tunnel shut or, if enough pressure is exerted, push the bulked frazil out the other end like toothpaste. The icing problem is not a new one for Denver; it has occurred regularly since the early 1900's with varying severity and during different periods of the winter. Attach- ments to Garstka's second study show a ten-year record of occurrence and explain the long-term struggle of Denver to cope with the problem. An even more extraordinary descrip- tion of the problem from an operating standpoint emerges from the deposition of C.E.C. Carlson (Exhibit 13), who described how, in the recent past, Denver's Conduit No. 20 froze up with frazil ice. The resulting column of ice was ninety inches in diameter, and after extraordinary measures were taken, was finally pushed through the conduit to Marston Lake which had, in the meantime, been drawn down to a level which could provide service for only ten to IS more days. From Garstka's studies, it is clear that fifty-foot- high diversion structures will not avoid the frazil ice problem; indeed he has real doubts as to whether the 191- foot-high Low Strontia Springs Dam alternate will avoid them. His best judgment and that of others who have studied the problem Objectively is that the only way to avoid the icing problem is to use the proposed Strontia Springs Dam and Reservoir with its large, SOOO-acre feet of capacity not required for river regulation and emergency operating storage. No competent evidence exists which can refute that seasoned professional judgment. No federal action or decision which ignores that judgment can be reasonable. 3. Sediment capacity. In its report to the BLM, the USBR grudgingly admits that the low-diversion structure would have, "*** limited sediment storage capacity, which would increase the future operating costs at the dam and treatment plant." This masterpiece of understatement reveals how shallow the USBR analysis of the problem was. This is so because, in the judgment of one of the best sediment experts in the world, Mr. Whitney Borland (one-time chief of the sedimentation branch of the USBR), the entire 97 acre feet of impoundment behind the fifty-foot-high low diversion structure could be filled with sediment in a single event. -13-