38. Reservoir Storage Allocations. Storage allocations in the reservoir have been made as follows: *After 50 years of operation. An allowance of 7,000 acre-feet for sediment has been made. B. Spillway 39. Requirements. The spillway was to be designed in compliance with the following requirements: (1) To pass all floods of magnitudes up to and including the 200-year frequency (reservoir design flood) by use of the flood control storage and release through an uncontrolled spillway opening of limited capacity. (2) To pass all floods of magnitudes up to and including the spillway design. flood by use of the flood control storage and by release through an uncontrolled opening and through a gate-controlled crest without exceeding a water surface elevation of 3129.5. Discharges through the uncontrolled spillway notch or weir were limited to 2,000 second-feet (the safe channel capacity of the stream below the dam) when the reservoir water surface elevation is 3127.0. 40. Preliminary Designs. The preliminary spillway design work included alternative schemes for the following: (1) A concrete, limited-capacity uncontrolled spillway in conjunction with a much larger capacity emergency or "grass" spillway. (2) A single concrete spillway consisting of an uncontrolled notch of limited capacity and a gate-controlled crest of much larger capacity. In either arrangement, all floods up to 200-year frequency flood would be handled by using the reservoir flood storage span and the uncontrolled spillway. Flows from floods of greater magnitude would pass through the emergency spillway in (1) or the gate-controlled crest in (2). After further studies were made, including costs, foundation conditions and structural features, three schemes were selected as presenting the more practicable of several solutions of the spillway problem. These schemes were designated as A-1, B-1, and B-2 (figs. 15, 16, and 17). Scheme A-1 was ruled out because of the high cost Figure 15.--Preliminary spillway scheme A-1. This scheme made use of an unlined spillway. UNITED STATES DEPARTMENT OF THE INTEROR FRENCHMAN CAMBRIDGE PROJECT-NEBR ENDERS DAM AUXILARY SPILLWAY OSLORADO JAN 7,1946 328-0 Figure 16.--Preliminary spillway scheme B-1. This scheme included six 50- by 30-foot gates. NOTES UNITED STATES DEPARTMENT OF THE INTERIOR MISSOURI BASIN PROJECT ENDERS DAM SPILLWAY PLAN AND SECTIONS 6-50x30 GATES - GATE SILLATEL 2097 DRAWN D.R.J. TRACED CHECKED SUBMITTED RECOMMENDED APPROVED DENVER COLORADO MARCH SCHEME B-1 |