OR00098 - Ochoco Dam


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Ochoco Dam


	Statistics

General

Region (Map): ................... Pacific Northwest
State (Map) ........................ Oregon

County ................................ Crook County

Project: ................................ Crooked River
Dam type: ........................... Earthfill

Location: ............................ Along Ochoco Creek

Watercourse: ..................... Ochoco Creek

Reservoir: ........................... Ochoco

Construction Date: .............1918-1920

National ID Number .......... OR00098

Hydrologic Unit Code ......

Dimensions

Crest Elevation of Dam:¹ ...................3143.00 ft
Structural Height of Dam: ................. 125.00 ft
Crest Length:: .....................................1350.00 ft
Top of Joint Use: ...............................3130.90 ft
Top of Active Conservation: ...........3113.94 ft
Top of Inactive Conservation: .........3113.94 ft
Spillway Crest: ....................................3130.90 ft
Top of Dead Storage: ........................3049.00 ft
Streambed at Dam Axis : ...................3018.00 ft

¹Without camber

USBR elevation is 0.7 feet greater than project elevations.

Hydraulics

Normal Water Surface Elev:................ 3136.2 ft
Hydraulic Height: .................................. 118.2 ft
Service Spillway Type:

Uncontrolled Crest ...................................... Yes

Crest Length ............................................ 275 ft
Gated .............................................................. No

Capacity at Elev: 3136.2 ft, 11,200 cfs

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

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

Outlet Works Capacity at

Elevation 3136.2 ft ................................. 415 cfs

Hydrology

Drainage Area: ................................... 291 sq mi

Hydrometeorological Report ............. HMR 57

Flood Type: ........................... Nov-Feb General

Type Storm: ................................. Winter Event

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

Probable Maximum Flood (PMF) Report:

Inflow Volume: ........................ 136,700 acre-ft

Flow Duration: ................................... 7.5 days

Peak Inflow: ..................................... 74,900 cfs

PMF Routing MWS Elev: ................. 3145.8 ft

Initial Routing Elev: ......................... 3130.9 ft

Study Date: ................................. January 1994

Power Generation

Power Generation at Dam Site - None

Bureau of Reclamation Power Program

Narration

Geology

Landslide (Qls) - This unit is a chaotic mixture of welded rhyolitic blocks up to 20 feet in diameter in a matrix of predominantly granular soil. It extends about one mile right and downstream of the centerline of the dam and several miles upstream. It has high permeability with repeated development of sinkholes along the reservoir shore. This unit is connected with most of the major seepage problems at the dam. It forms the right abutment of the dam and the foundation of the outlet works conduit. This unit contains a Basal Zone (Qlsb) with a significantly high proportion of clay fines and lower permeability. The Basal Zone is the failure surface upon which the landslide rides.

Alluvial Fan/Talus Complex (Qaf) - This unit is a crudely stratified mixture of hard angular cobbles and boulders in a matrix of gravelly silt and clay. It is generally semipervious but can transmit significant seepage in some areas. It forms most of the foundation of the spillway and most of the left abutment of the dam.

Slopewash (Qsw) - This unit is composed of local residual and accumulated deposits of angular cobbles and boulders with a matrix of gravel, sand, silt and clay on the left abutment.

Alluvium (Qal) - This unit is composed of gravel and sand deposits of Ochoco Creek with some interbeds of silt and clay and occasional cobbles. The permeabilities range from about 200 to 7,000 ft/yr. Upper and lower zones form local aquifers with the lower zone being artesian to the upper zone.

Fluviolacustine Sediments (Qfs) - This unit is predominantly fine-grained silt and clay with minor amounts of sand and gravel. The unit behaves as an aquitard between the upper and lower alluvium. This unit forms the foundation for the maximum section of the dam.

Mud/debris Flow (Qtmf) - This unit is about 75 percent cobbles and boulders to a maximum dimension of 12 feet in a matrix of dense sandy silt. It was found exposed on the left abutment during excavation for the spillway stilling basin.

John Day Formation (Tjdt) - This is the local bedrock. It is moderately hard to hard lapilli tuff and is generally lightly weathered but with zones of intense weathering. It is moderately to intensely fractured. Unconfined compression tests ranging from 130 to 3,000 psi.

Miscellaneous Links

| Current Reservoir Storage, plus other storage units within the Deschutes River Basin |

Links

| Recreation |

| Dams Located by State | USBR Oregon Dams | Pacific Northwest Region Dams |

| Owner: Ochoco Irrigation District,
1001 North Deer St, Prineville, OR 97754-1134, (541) 447-6449

| Operator: Ochoco Irrigation District,
1001 North Deer St, Prineville, OR 97754-1134, (541) 447-6449