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Description:
Source: https://erdc-library.erdc.dren.mil/jspui/ ; Model investigation of the outlet works for the Beltzville Reservoir was concerned with the overall performance of both the flood-control and selective withdrawal facilities of the intake structure. The study was conducted in a 1:20-scale model of the outlet works which reproduced a portion of the approach area, the intake structure, the outlet conduit, and the hydraulic-jump type stilling basin. Modifications of the proposed outlet structure were required to provide effective regulation of flood-control releases up to about 2000 cfs and water-quality releases ranging from 35 to 300 cfs (summer and winter flows). Subatmospheric pressures that were detected in the original design water-quality conduit in the area below the control gate were eliminated by reducing the central angle of the elbow above the control gate from 90 to 82 deg and placing the gate chamber and downstream chute on an 8-deg slope (type 2 design). Pressures were positive throughout the flood-control conduit for all full flow conditions. With gate openings equal to or less than 50 percent and partial flow conditions, the discontinuity due to the intersection of the horizontal gate section and sloping conduit produced subatmospheric pressures in the immediate area of the intersection. Rounding or streamlining the area of intersection in the prototype structure should result in acceptable pressure conditions. Performance of the original stilling basin was satisfactory and the height of the basin training walls was sufficient to prevent overtopping. Protective stone is not required in the exit channel since it will be excavated in sound rock.