Spook Hill Reservoir Report

Last Updated: December 5, 2025

Spook Hill, located in Mesa, Arizona, is a fascinating earth dam constructed in 1979 by the USDA NRCS for flood risk reduction along the Salt River.


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Summary

This local government-owned structure stands at a height of 27 feet, with a dam length of 21,120 feet and a storage capacity of 4,250 acre-feet. The dam's primary purpose is flood risk reduction, providing critical protection to the surrounding area in Maricopa County.

Despite its satisfactory condition assessment, Spook Hill poses a high hazard potential due to its uncontrolled spillway and outlet gates. The dam's risk assessment is rated as moderate, emphasizing the importance of regular inspections and maintenance to ensure its continued effectiveness in mitigating flood risks. The Arizona Department of Water Resources plays a key role in regulating, inspecting, and enforcing safety measures for the dam, highlighting the state's commitment to water resource management and climate resilience in the region.

With its intriguing design and vital role in flood risk reduction, Spook Hill serves as a testament to the importance of infrastructure in safeguarding communities against natural disasters. As water resource and climate enthusiasts, the unique features and regulatory oversight of this earth dam offer valuable insights into the intersection of engineering, environmental stewardship, and public safety in managing water resources in Arizona.

Year Completed

1979

Dam Length

21120

Dam Height

15

River Or Stream

SALT RIVER - TR

Primary Dam Type

Earth

Surface Area

305

Hydraulic Height

15

Drainage Area

16.3

Nid Storage

4250

Structural Height

27

Outlet Gates

Uncontrolled

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

27
       
Seasonal Comparison

Weather Forecast

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.