The Colorado River and Its Deveudpment 535 



On the Little Colorado River, there is a dam site at Tolchaco, 

 where the entire flood flov^^ of that stream can be controlled by a dam 

 50 feet high. 



The site at the mouth of Diamond Creek is of particular interest 

 to Arizona, on account of its favorable location and because it is con- 

 trolled by Arizona people. The site is only 16 miles from Peach 

 Springs, a station on the Santa Fe Railroad. It is a power project 

 only, there behig practically no storage. Present plans, subject to 

 modification, call for a dam 284 feet high, 324 feet above bedrock, to 

 the spillway crest, and the top of the structure would be 25 feet higher. 

 About 110,000 horsepower could be developed with the unregulated 

 flow of the river, but in case the flow is equalized by a project with 

 storage farther up the river, the ultimate power development may reach 

 600,000 horsepower. The canyon at this site is only 220 feet wide at 

 the water level, and the length of the dam at the top will be 600 feet, 

 about the same as the Roosevelt dam. The walls and foundation are 

 of granite. The main electric transmission line would extend through, 

 or near, Prescott, Phoenix, Mesa, Florence, and Tucson to Douglas, 

 with important laterals to Jerome, Ray, Globe, Clifton, Ajo, and Yuma. 



The Boulder Canyon site is in a similar narrow canyon in granite 

 rock. The canyon walls are 300 feet apart. Here it is proposed to 

 build a solid concrete masonry dam 600 feet high, 735 feet above bed- 

 rock, to elevation 1300 feet above sea level. The capacity of the reser- 

 voir is 31,600,000 acre-feet, and the estimated cost of the dam alone is 

 $55,000,000. The great depth to bedrock is the main disadvantage of 

 this site. While the problems of carrying the foundation to so great 

 a depth and of passing the annual and occasional floods of the river 

 during the construction period strike terror to the heart of the en- 

 gineer, the task can be accomplished if adequate funds are provided. 

 The power development will be 700,000 continuous horsepower as long 

 as the irrigated area in the lower basin does not exceed 1,500,000 

 acres, and will decrease to 600,000 horsepower as the acreage increases 

 to 2,000,000 acres. 



The last annual report of the United States Reclamation Service 

 states that an inspection of the lower river was made by boat by Homer 

 Hamhn, a noted engineer, in April, 1920, and that he reports that 



