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<br /> <br />- 19 - <br /> <br />new structures; and the combining of two parallel sections of canal, <br />owned by the Pine River Canal Company and the Spring Creek Ditch <br />Company, into one canal. These structural measures are needed to help <br />provide the necessary improvement in irrigation water management on <br />the irrigated lands. Structural works of improvement involving re- <br />habil i ta tion of the main canal sys tern are res tric ted to those measures <br />within the canal rights-of-way. <br /> <br />Locations of existing and proposed structures are shown on the <br />Project Map. Structural costs are shown in Tables 1 and 2. Structural <br />items and quantities are listed in Tables 3 and 3A. For the purpose of <br />evaluation, the structures are divided into two units: (1) floodwater- <br />retarding reservoirs, and (2) distribution system rehabilitation. <br /> <br />Floodwater-RetardinR Structures.- This Work Plan proposes the <br />installation of two floodwater-retarding structures located above the <br />irrigated lands. They will be compacted earthfill structures with <br />reinforced concrete spillway tubes. The emergency spillway will be a <br />shaped and vegetated earth section. <br /> <br />The reservoir area behind each dam will have sufficient capacity <br />to provide flood prevention storage for floodwater runoff resulting <br />from a storm with a recurrence interval of once in 25 years. Additional <br />storage will be provided for the amount of sediment expected to accumu- <br />late over a 50-year period. There will be no permanent storage of water <br />and the reservoirs will be dry except during flood runoff. (See Figure I, <br />"Typical Floodwater-Retarding Structure".) <br /> <br />The floodwater-retarding structures PR-l and PR-2 will be located <br />above two of the present canal structures that need replacement, and <br />will reduce floodwater, sediment, and scour damages to irrigated lands, <br />canals, and State and County roads and bridges. <br /> <br />The estimated cost of installing the floodwater-retarding features <br />of structures PR-l and PR-2 is $99,101. Group A in the following <br />"Distribution System Rehabilitation" section describes the agricultural <br />water management features that will be added to these structures and <br />gives their cost as $27,737. The incremental costs for .these appur- <br />tenances to the floodwater-retarding structures will be cost-shared on <br />the same basis as other agricultural water management features. Total <br />installed cost is $126,838 for PR-l and PR-2 with appurtenances. The <br />cost distribution is shown in Table 2. <br />