Millett Swale Reservoir Report
Nearby: Taylor Wwtp (Basins 1 & 2) Schoens
Last Updated: December 5, 2025
Millett Swale, located in Navajo County, Arizona, is a vital flood risk reduction structure with a primary purpose of debris control and flood risk reduction.
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Summary
Constructed in 1958 by the USDA NRCS, this earth dam stands at a height of 24 feet and stretches 2500 feet in length, providing a storage capacity of 2104 acre-feet. Despite its crucial role in managing water resources, Millett Swale is facing challenges with a poor condition assessment and a high hazard potential, emphasizing the need for immediate attention and maintenance.
Managed by the Arizona Department of Water Resources, Millett Swale is regulated, permitted, inspected, and enforced in accordance with state regulations. With a drainage area of 40 square miles and a maximum discharge capacity of 6120 cubic feet per second, this structure plays a significant role in protecting the surrounding communities of Taylor and Shumway from potential flooding events. However, the dam's deteriorating condition raises concerns about its long-term effectiveness in safeguarding the area against flood risks, highlighting the importance of ongoing risk management measures and maintenance efforts.
Despite its critical importance in flood risk reduction, Millett Swale's current state of disrepair and high hazard potential underscore the urgent need for comprehensive risk assessment, maintenance, and potential rehabilitation efforts. As a key infrastructure managed by the Natural Resources Conservation Service, Millett Swale serves as a crucial component in the region's water resource management system, emphasizing the importance of proactive measures to ensure its continued functionality and resilience in the face of changing climate conditions and increasing water-related challenges.
Year Completed |
1958 |
Dam Length |
2500 |
Dam Height |
24 |
River Or Stream |
MILLET SWALE |
Primary Dam Type |
Earth |
Surface Area |
200 |
Drainage Area |
40 |
Nid Storage |
2104 |
Structural Height |
35 |
Hazard Potential |
High |
Foundations |
Rock, Soil |
Nid Height |
35 |
Seasonal Comparison
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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.
Millett Swale