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<br />CHAPTER II - PROPOSED ACTION AND ALTERNATIVES <br /> <br />Alternatives <br /> <br />Two basic alternatives were examined in detail and several alternatives were discarded from <br />detailed analysis. Under the No Action alternative, the barrier caused by the GVIC Diversion <br />Dam would continue to have a negative impact on the endangered Colorado squawfish and <br />razorback sucker under low flow conditions. The preferred alternative would be to place large <br />rocks (riprap) on the downstream face of the GVIC Diversion Dam. The riprap and the river <br />channel would be arranged in a manner that simulates. natural pools and riffles. This pool and <br />riffle pathway would permit upstream fish movement. This natural passage design at GVIC, as <br />well as the passageway structure recently completed on the Gunnison River, will be monitored <br />and evaluated to help determine the best designs for additional passageways on the river at the <br />Price-Stubb and the Government HigWine Diversion Dams. <br /> <br />GVIC Fish Passage <br /> <br />Design <br /> <br />FLO Engineering, Inc. (1997) provided a brief history and description of the existing GVIC <br />Diversion: "The GVIC is the oldest major irrigation project in the Grand Valley, It initially went <br />into operation in 1883. The original headgates were destroyed by a flood in 1898 and replaced in <br />190 I by the current structure. The original wooden cribbing diversion structure was modified <br />over a three year period around 1980 to incorporate a concrete cutoff wall and an additional <br />concrete cap across its crest." "The system provides water to approximately 38,000 acres <br />through 100 miles of canals," "To supply the system, GVIC owns 640 cubic feet per second (cfs) <br />of irrigation water rights which are comprised of520 cfs with a 1882 priority date and 120 cfs <br />with a 1914 priority date." <br /> <br />At high streamflows of approximately 12,000 cfs, the diversion dam becomes submerged and is <br />not a barrier to fish passage. However, at lower streamflows, the diversion dam effectively blocks <br />fish passage to upstream reaches. <br /> <br />The preferred alternative was selected based on the behavior of the endangered fish, their <br />swimming abilities, GVIC operation and maintenance needs, and the need to not interfere with <br />irrigation diversions. To simulate a "natural-like" stream feature, the plan includes a 30-foot <br />wide notch in the existing GVIC dam to allow the fish to swim upstream through the notch at <br />flows ofless than 5,000 cfs. Rocks (2-foot diameter) would be placed downstream from the <br />diversion dam in a series of pools and riffles and on a slope designed to reduce velocities <br />significantly to accommodate the swimming abilities of the endangered fishes, The series of20- <br />foot long pools with intervening riffles about 5.0 feet long would extend over 400 feet. The <br /> <br />7 <br />