MT00743 - Helena Valley Dam


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Helena Valley Dam


	Statistics

General

Region (Map) : ................ Great Plains

State (Map) ...................... Montana

County .............................. Lewis and Clark

Project: ...............................PSMBP-Helena Valley

Dam type: ......................... Earthfill

Location: .......................... 8mi NE of Helena

Watercourse: ................... Tenmile Creek Trib.

Reservoir: ......................... Helena Valley

Construction Date: ........ 1957-1958

National ID Number ....... MT00743

Hydrologic Unit Code ....

Dimensions

Crest Elevation of Dam: ................. 3,828.0 ft

Structural Height of Dam: .................. 91 ft

Crest Length: ......................................... 2785 ft

Top of Joint Use: ...................................... x.0 ft

Top of Active Conservation: ........... 3,820.1 ft

Top of Inactive Conservation: ........... 3,805 ft

Spillway Crest: .......................................... x.0 ft

Top of Dead Storage: ....................... 3,799.4 ft

Streambed at Dam Axis : ..................... 3,755 ft

Hydraulics

Normal Water Surface Elev: .............. 3820.1 ft

Hydraulic Height: ...................................... 72 ft

Service Spillway Type:

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

Morning-Glory ........................................... No

Crest Length .......................................... xx ft

Gated ....................................................... No

Capacity at Elev: xxxx.0 ft, x,xxx cfs

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

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

Outlet Works Capacity at

Elevation 3,807 ft., ........................... 350 cfs

Hydrology

Drainage Area: ........................................... 3 sq mi

Hydrometeorological Report (HMR) HMR x

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

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

Probable Maximum Flood (PMF) Report:

Peak Inflow: .................................. cfs

Inflow Volume: ........................ acre-ft

Flow Duration: ......................................0 days

PMF Routing MWS Elev.: ................. x.0 ft

Initial Routing Elev: ............................ x.0 ft

Study Date: xx 19

Power Generation

Power Generation at Dam Site - None

Bureau of Reclamation Power Program

Narration

Geology

The earliest geologic history of this region is recorded in the thick section of pre-Cambrian rocks known as the Belt series. After these sediments were deposited, the area was subjected to diastrophism and was reduced by erosion to low relief. The Flathead quartzite of Middle Cambrian time, basal formation of the Paleozoic section, was deposited on the truncated beds of the Belt series. Conditions of deposition changed during Cambrian time in such ways that shale mud was deposited alternately with time. No general stratigraphic breaks between these Cambrian formations are recognized; they are separated chiefly on the basis of lithographic differences.

Links

| Recreation |

| Dams Located by State | USBR Montana Dams | North Great Plains Region Dams |

| Owner: Bureau of Reclamation, Montana Area Office,
PO Box 30137, Billings, MT 59107-0137, (406) 247-7664

| Operator: Helena Valley Irrigation District,
3840 North Montana, Helena, MT 59602, (406) 442-3292