Thief Valley Dam

Overview

Thief Valley Dam is a reinforced concrete, slab and buttress (Ambursen) structure, 73 feet high and 390 feet long. The original reported (1932) total capacity of Thief Valley Reservoir was 17,600 acre-feet (active 17,400 acre-feet) and covered an area of 740 acres. A sedimentation survey completed in 1992 estimated the total capacity at 13,307 acre-feet (active 13,300 acre-feet) and the surface area at 685 acres.

Geology

Thief Valley Dam is founded on closely fractured, metamorphosed basaltic rock. The basalt is hard, brittle and only slightly altered. Principal orthogonal fractures are spaced 12 to 18 inches apart and are oriented parallel and perpendicular to the canyon axis. Subsidiary jointing is spaced less than 2 inches apart and oriented obliquely to the principal joint-set. There appears to be no change in fracture orientation between the right and left abutments inferring that there are no faults of significance within the canyon.

Two shear zones are visible in the rock of the right abutment. These zones are about one foot wide, the width varying in both directions. A third shear zone was reported to pass between No.6 and No. 9 buttresses within the stilling basin area. The shear zone material, which consisted of alterered rock, was excavated to a depth of about 6-feet below sound rock and to a sufficient width to allow for the placement of a 6-foot concrete footing where buttress 7 crosses. A cutoff trench was excavated on the upstream toe of the dam, and curtain grouting was performed along the trench through grout holes which were drilled on about 5-foot centers and to a depth of about 10 to 20 feet.


General
RegionFacilities in Pacific Northwest | Pacific Northwest Home Page
StateOregon
CountyBaker, Union
ProjectBaker, Union
Dam TypeConcrete Slab and Buttress
ReservoirThief Valley
WatercoursePowder River
Location16 mi N of Baker, OR
Longitude-117.7810764
Latitude45.012996
Original Construction1931-1932
Modified Construction
National ID NumberOR00592
Hydrologic Unit Code

Dimensions
Structural Height73.0 ft
Hydraulic Height (Normal Operating Depth at Dam)58.0 ft
Top Parapet (Elevation)
Spillway Crest Elevation31433.0 ft
Crest Elevation3143.0 ft
Crest Length390.0 ft
Crest Width7 ft
Base Width85 ft
Volume of Dam Construction Materials6,300 cu yd
Streambed at Dam Axis
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)
Top of Active Conservation Pool (Elevation)3133.0 ft
Top of Inactive Conservation Pool (Elevation)
Top of Dead Storage Pool (Elevation)

Hydraulics & Hydrology
Total Water Storage at Elevation13,307 ac-ft
Maximum Water Surface Elevation
Normal Water Surface Elevation3133.0 ft
Spillway TypeUngated overflow
Auxiliary Spillway
Spillway Capacity at Elevation35,000 cfs at 3143.0 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation2,150 cfs at 3133.0 ft
Diversion Capacity at Elevation
Drainage Area914 sq mi
Hydrometeorological Report (HMR)HMR 43

Contact Information
Owner
TitleArea Office Manager
OrganizationSnake River Area Office
Address230 Collins Road
CityBoise, ID 83702-4520
Phone (Fax)208 383-2275
Phone (Office)208 383-2248
Operator
OrganizationLower Powder River Irrigation District
Address2550 Broadway Avenue
CityBaker, OR 97814
Phone (Office)541 523-6471


Last updated: Jul 26, 2012