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. . . O(}3323 CHAPTER III POTENTIAL IRRIGATION DEVELOPMENT and west of the reservoir. The O'Neal Park Canal would serve lands generally south of the reservoir. In addition to these two canals. five main laterals with a combined length of approximately 14 miles would be required to. serve the project lands. Small farm laterals also would be required for the entire project area. Only a limited drainage system consisting primarily of surface drains would be required for some of the lower lAnds that have the relatively heavy soils. o rTOJec. worKS ana ~os.s Preliminary designs and estimates of reconnaissance scope, based on typical structures successfully constructed, operated, and maintained over many years, were made of the required project works. Designs were based on a minimum of field data with consideration given to terrain and loca- tion, required capacities, apparent geological conditions. and availabil- ity of materials. Some difficulty could be encountered in the construc- tion of canals or laterals on moderately steep shale hillsides in the area. Such places were avoided as much as possible by using alternate locations or siphons. The designs and estimates are believed suitable for development of a project plan and for use in determining the relative engineering feasibility and economic justification of further project investigations. The available engineering data would not be adequate for a feasibility report nor for construction designs and estimates. Brief descriptions of the project works are given in the following paragraphs. The descriptions are followed by a summary of estimated construction costs and ennual operation, maintenance, and replacement costs. Perry Dra1{ Dam and Reservoir A:a offstream storage reservoir would be created on Perry Draw by an earth-fill dam that would rise 77.5 feet above streambed and would have a crest length of 1,410 feet. The reservoir would have an active capa- city of 5,300 acre-feet and a dead storage capacity of 200 acre-feet. The outlet works would have a capacity of 55 second-feet at low reservoir water level. As the natural drainage area above the reservoir is only 1,150 acres. it was deemed more economical to store all flood waters in the reservoir than to provide a spillway. The 5-foot zone above noI'llla1. water surface would provide 1,000 acre-feet of such storage. A:a additional 5 feet of freeboard has been provided for estimating the cost of the dam. Hore detailed study, however, l1Jl!J.y show th~ need for a BIIlBll emergency spill- way. Topography of Perry Draw Reservoir and Dam site was obtained by widely spaced planetable shots. These points were identified on aerial photos and contours sketched with the aid of a stereoscope. Elevations were based on an altimeter elevation carried in from a bench mark approximately 2 miles from the reservoir area. 19