CO01656 - Granby Dam


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Granby Dam and Dikes


	Statistics

General

Region (Map) : ........... Upper Colorado
State (Map) ................. Colorado

County ......................... Grand

Project: ......................... Colorado Big Thompson
Dam type: .................... Earthfill

Location: .......................5.5 mi NE of Granby

Watercourse: .............. Colorado River

Reservoir: .................... Lake Granby

Construction Date: .....1941-1950

National ID Number ... CO01656

Hydrologic Unit Code ...

Dimensions

Crest Elevation of Dam: ....................... 8290.00 ft
Structural Height of Dam: .................... 298.00 ft
Crest Length: ........................................ 861.00 ft
Top of Joint Use: .................................. 8280.00 ft
Top of Active Conservation: .............. 8279.50 ft
Top of Inactive Conservation: ............ 8186.00 ft
Spillway Crest: ....................................... 8260.00 ft
Top of Dead Storage: ........................... 8174.63 ft
Streambed at Dam Axis : ...................... 8059.00 ft

Hydraulics

Normal Water Surface Elev: ............. 8279.5 ft
Hydraulic Height: ................................ 223.0 ft
Service Spillway Type:

Uncontrolled Crest ............................. No

Morning-Glory ........................................ No
Crest Length ......................................... NA
Gated ....................................................Yes

Capacity at Elev: 8280.0 ft, 11,500 cfs

Auxiliary Spillway ....................................... No

Capacity at Elev. ................................ 0 cfs

Outlet Works Capacity at
Elevation 8280.0 ft., ........................ 435 cfs

Hydrology

Drainage Area: ............................... 311.0 sq mi

Hydrometeorological Report HMR 49

Flood Type: ..............................Winter General

Storm Duration: ....................................... 72 hrs

Probable Maximum Flood (PMF) Report:
Peak Inflow: ..................................... 57,900 cfs

Inflow Volume: ........................ 151,600 acre-ft

Flow Duration: .................................... 15 days

PMF Routing MWS Elev.: ........................ NA

Initial Routing Elev: ........................... 8279.5 ft

Study Date: ............................... October 1994

Power Generation

Power Generation at Dam Site - None

Bureau of Reclamation Power Program

Narration

Geology

Granby Dam, Spillway and Tunnel Outlet Works are located in a steep, narrow canyon composed of Precambrian crystalline rocks. Several small faults and rock with varying degrees of hardness and weathering were encountered in the cutoff trench, spillway and tunnel excavations. Fractured, loose and weathered rocks were removed from foundation areas during construction. The dam outside the limits of the cutoff trench rests on granular alluvium up to 65 feet in thickness; the soil types are unknown. Dikes No. 1, 2 and 4 are founded on siltstone of the North Park Formation. Two faults bound the area of the dikes. One passes from the left abutment of Dike No. 2 down the valley southwestward approximately parallel to the axis of DIKE No. 1. The other trends due north and passes under the West End of Dike No. 1. These faults have broken the siltstone

Other Dams or Dikes which enclose Lake Granby

1) Granby Dike No. 1
2) Granby Dike No. 2
3) Granby Dike No.3
4) Granby Dike No.4

Links

| Recreation |

|Dams Located by State | USBR Colorado Dams | South Great Plains Region Dam |

| Owner: Bureau of Reclamation, Eastern Colorado Area Office,
11056 West County Road 18E, Loveland, CO 80537-9711, (970) 667-4410

| Operator: Northern Colorado Water Conservancy District,
PO Box 679, Loveland, CO 80539, (970) 667-2437