Thompson Falls - Intake Dam B Reservoir Report

Reservoir Report

Montana

Nearby: Thompson Falls - Intake Dam A Thompson Falls - Dry Channel Dam

Last Updated: December 23, 2025

Thompson Falls - Intake Dam B, located in Sanders County, Montana, is a privately-owned hydroelectric facility designed and built by Stone & Webster-Kiewit JV in 1996.

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Summary

The dam, standing at a height of 135 feet with a structural height of 142 feet, serves the primary purpose of generating hydroelectric power from the Clark Fork River and Pend Oreille. With a normal storage capacity of 14,970 acre-feet and a total storage of 24,450 acre-feet, the dam plays a crucial role in water resource management in the region.

The dam features a gravity type structure with a concrete design, utilizing Tainter and Vertical Lift outlet gates for water control. Despite being categorized as low hazard potential, the dam's risk assessment is rated as high, highlighting the importance of regular inspections and adherence to safety protocols. The Federal Energy Regulatory Commission oversees the regulatory aspects of the facility, ensuring compliance with operational standards. Although the dam does not fall under state jurisdiction, its strategic location and efficient hydraulic design make it a key player in the regional water management system.

Thompson Falls - Intake Dam B is a significant player in the hydroelectric power generation landscape of Montana, contributing to the sustainable utilization of water resources in the area. With its modern infrastructure and efficient operation, the dam serves as a testament to the importance of harnessing renewable energy sources while maintaining strict safety standards. As climate change impacts water resources, facilities like Intake Dam B play a crucial role in ensuring a reliable and sustainable water supply for future generations.

Year Completed	1996
Dam Length	78
Dam Height	135
River Or Stream	Clark Fork River, Pend Oreille
Primary Dam Type	Gravity
Surface Area	1580
Hydraulic Height	133
Drainage Area	21113
Nid Storage	24450
Structural Height	142
Outlet Gates	Tainter (radial) - 1, Vertical Lift - 3
Hazard Potential	Low
Nid Height	142

Explore Interactive Map

THOMPSON FALLS - INTAKE DAM B

Reservoir Report • Water Levels • Weather Forecast

December 23, 2025

Year_Completed	1996
Dam_Length	78
Dam_Height	135
River_Or_Stream	Clark Fork River, Pend Oreille
Primary_Dam_Type	Gravity
Surface_Area	1580
Hydraulic_Height	133
Drainage_Area	21113
Nid_Storage	24450
Structural_Height	142
Outlet_Gates	Tainter (radial) - 1, Vertical Lift - 3
Hazard_Potential	Low
Nid_Height	142

Seasonal Comparison

Weather Forecast

Nearby Streamflow Levels

Prospect Creek At Thompson Falls Mt 560.0cfs	560cfs
Thompson River Near Thompson Falls Mt 765.0cfs	765cfs
St. Regis River Near St. Regis 1210.0cfs	1210cfs
Clark Fork At St. Regis Mt 9520.0cfs	9520cfs
Clark Fork Near Plains Mt 24900.0cfs	24900cfs
Canyon Creek Ab Mouth At Wallace 80.8cfs	81cfs

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.