Engin. library

55%

•ui

T8
US

General Information

Purpose: Flood control, diversion for irrigation, storage, sedimentation control, fish and wildlife preservation, and recreation & Location: On Republican River, about 2-1/2 miles west of Trenton, Nebr. Constructed: 1949-1953 Water supply: Republican River Drainage area: 4, 003 square

miles
Maximum flood: 200, 000 second-
feet (May 31, 1935)
Average yearly flow: 211 second-
feet (1947-1952)
Reservoir:

Official name: Swanson Lake
Area: 7,975 acres at elevation

2773.0 Flood control storage: 133, 800 acre-feet, between elevations 2752.0 and 2773.0 Active irrigation storage: 116,100 acre-feet, between elevations 2710.0 and 2752.0 Dead storage: 4, 100 acre-feet, between elevations 2693.0 and 2710.0 Dam

Type: Zoned rolled-earth fill
Foundation: Pierre shale"
Slope protection: Riprap on gravel
blanket on upstream face, seeded
topsoil on downstream face
Dimensions:

Height: 144 feet above lowest ex-
cavation in cutoff trench, 100
feet above riverbed
Crest length: 8, 600 feet
Crest elevation: 2793.0
Crest roadway width: 30 feet
Volume: 7, 800, 000 cubic yards
Slopes: Upstream, 6 to 1 to ele-
vation 2710, 3 to 1 to elevation
2760, and 2-1/2 to 1 to eleva-
tion 2793

Downstream, 10 to 1 to elevation 2710, 4 to 1 to elevation 2735, 2-1/2 to 1 to elevation 2760, and 2 to 1 to elevation 2793

Dam (Continued)

Main cutoff trench: 50-foot base width

with 1-1/2 to 1 side slopes, length

about 6, 760 feet
Auxiliary cutoff trench: 50-foot base

width with 1-1/2 to 1 side slopes,

length about 570 feet

Spillway

Type: Concrete overflow chute type
with stilling basin

Crest length of overflow section: 126
feet

Crest: Elevation 2743. 00

Maximum discharge: 126, 500 secondfeet at water surface elevation 2785. 6 (as determined by model studies)

Gates: Three, 42 by 30 feet

Stilling basin: Reinforced concrete with dentated sills

River Outlets

Outlets: Two

Invert: Elevation 2710. 00

Gates: Four, 6 by 7.5 feet (two are installed in each outlet)

Discharge capacity: 1, 000 second-feet with reservoir water surface elevation at 2720.0

Canal Outlet Works

Intake structure:

Vertical shaft: 50 feet high
Sill elevation: 2710.00

Outlet conduit: 5 feet 6 inches in diam-
eter, 208 feet long

Outlet pipe: 56-inch-diameter pipe in horseshoe conduit, 244 feet long

Gates: Two, 4 by 4 feet (one is installed in the emergency gate chamber and the other in the control house)

Discharge capacity: 300 second-feet with reservoir water surface elevation 2720.0, and canal water elevation 2705.0