Twenty Four Mile Reservoir Report
Nearby: Portneuf Toponce Ditch Dam Lower
Last Updated: December 19, 2025
Twenty Four Mile is a privately owned dam located in Chesterfield, Idaho, with a significant hazard potential and a fair condition assessment.
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Summary
Completed in 1928, this Earth dam stands at a height of 27.4 feet and has a hydraulic height of 21.8 feet, providing a storage capacity of 700 acre-feet for water from Twentyfour Mile Creek and Portneuf River. The dam spans 1100 feet in length, with a spillway width of 20 feet for uncontrolled discharge.
Managed by the Idaho Department of Water Resources, Twenty Four Mile is subject to state regulation, permitting, inspection, and enforcement to ensure its safety and compliance with guidelines. The dam's surrounding area covers a drainage area of 7.8 square miles, with a surface area of 44 acres. Despite its moderate risk assessment, the dam has not been modified in recent years, and its last inspection in August 2020 indicated a fair condition, highlighting the need for ongoing monitoring and maintenance to mitigate potential risks and ensure its long-term functionality.
For water resource and climate enthusiasts, Twenty Four Mile presents a fascinating case study of a historic dam in Idaho that continues to play a crucial role in water management and flood control. With its unique design features, storage capacity, and regulatory oversight, this dam serves as a valuable asset in the region's water infrastructure, demonstrating the importance of proactive risk management and maintenance to safeguard against potential hazards and ensure the safety of surrounding communities and ecosystems.
Year Completed |
1928 |
Dam Length |
1100 |
Dam Height |
27.4 |
River Or Stream |
TWENTYFOUR MILE CREEK PORTNEUF RIVER |
Surface Area |
44 |
Hydraulic Height |
21.8 |
Drainage Area |
7.8 |
Nid Storage |
700 |
Hazard Potential |
Significant |
Foundations |
Rock, Soil |
Nid Height |
27 |
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.
Area Campgrounds
| Location | Reservations | Toilets |
|---|---|---|
Sagehen Flat
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Sage Hen Flats Campground
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Graves Creek
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Cutthroat Trout Campground
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Grave's Creek Campground
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Morgan's Bridge Campground
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Twenty Four Mile