Sullivan Dam Reservoir Report
Nearby: Cowpath Dam Alkali Flat
Last Updated: December 6, 2025
Sullivan Dam, also known as Lake Shel-Oole, is a critical Earth-type structure located in Shelby, Montana, designed by the USDA NRCS and completed in 1967.
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Summary
With a height of 49 feet and a hydraulic height of 40 feet, the dam serves the primary purpose of flood risk reduction along the TR-MARIAS river. It boasts a capacity of 1470 acre-feet of storage, with a normal storage level of 360 acre-feet and a surface area of 33 acres.
The dam, which is under state jurisdiction and regulated by the DNRC, has a spillway width of 70 feet and can discharge up to 3150 cubic feet per second. Despite being classified as having a high hazard potential, the dam's condition assessment as of June 2018 was deemed satisfactory. Emergency action plans are in place, with the last revision dating back to September 2021. With a moderate risk assessment rating, the dam's risk management measures are currently unspecified, but regular inspections are carried out every five years to ensure its safety and integrity for the community it serves.
Year Completed |
1967 |
Dam Length |
750 |
Dam Height |
49 |
River Or Stream |
TR-MARIAS |
Primary Dam Type |
Earth |
Surface Area |
33 |
Hydraulic Height |
40 |
Drainage Area |
2048 |
Nid Storage |
1470 |
Structural Height |
68 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
High |
Foundations |
Rock, Soil |
Nid Height |
68 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Sullivan Dam