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.
General
Project
Colorado-Big Thompson
Latitude
40.1650
Watercourse
Colorado River
Original Construction
1941-1950
Longitude
-105.8633
Reservoir
Lake Granby
National ID Number
CO01656
Dimensions
Structural Height
298.00 ft
Crest Length
861.00 ft
Top of Active Conservation Pool (Elevation)
8279.50 ft
Top of Inactive Conservation Pool (Elevation)
8186.00 ft
Spillway Crest Elevation
8260.00 ft
Streambed at Dam Axis
8059.00 ft
Crest Elevation
8290.00 ft
Hydraulic Height (Normal Operating Depth at Dam)
223.0 ft
Top of Joint Use Pool (Elevation)
8280.00 ft
Top of Dead Storage Pool (Elevation)
8174.63 ft
Hydraulics & Hydrology
Spillway Capacity at Elevation
11500 cfs at 8280.0 ft
Outlet Works Capacity at Elevation
435 cfs at 8280.0 ft
Drainage Area
311.0 sq mi
Hydrometeorological Report (HMR)
HMR 49
Normal Water Surface Elevation
8279.5 ft
Auxiliary Spillway
No
Contact
Owner
Title: Area Office Manager Organization: Eastern Colorado Area Office Address: 11056 W. County Rd 18E City: Loveland, CO 80537-9711 Fax: 970-663-3212 Phone: 970-461-5410
Operator
Organization: Northern Colorado Water Conservancy District Address: 220 Water Ave. City: Berthoud, CO 80513 Phone: 800-369-7246
More Information about the U.S. Bureau of Reclamation