Hilleary Dam Reservoir Report

Last Updated: December 5, 2025

Hilleary Dam is a private dam located in GEODE STATE PARK, Iowa, along the TR-CEDAR CREEK river.


°F

°F

mph

Wind

%

Humidity

Summary

Built in 1989, this Earth-type dam stands at a height of 32 feet and spans a length of 280 feet, with a storage capacity of 41 acre-feet for purposes such as fire protection, stock, or small fish pond. The dam is under the regulatory oversight of the IOWA DNR and has been identified as having a low hazard potential, with a moderate risk assessment rating.

Despite being privately owned, Hilleary Dam is subject to state regulations, inspections, and enforcement, ensuring its structural integrity and safety. The dam's design was attributed to SCS, and it falls under the jurisdiction of the Kansas City District of the USACE. With its strategic location and purposeful design, the dam serves as a crucial water resource infrastructure in Des Moines, Iowa, contributing to the local ecosystem and providing essential services such as water storage and flood control.

Water resource and climate enthusiasts will appreciate the significance of Hilleary Dam in managing water resources and mitigating potential risks in the region. Its location within GEODE STATE PARK adds to its ecological value, while its low hazard potential and moderate risk assessment highlight the importance of maintaining and monitoring dams for the safety of surrounding communities. As a key player in the water infrastructure network, Hilleary Dam exemplifies the balance between harnessing water resources for various purposes and safeguarding against potential hazards in a changing climate landscape.

Year Completed

1989

Dam Length

280

Dam Height

32

River Or Stream

TR-CEDAR CREEK

Primary Dam Type

Earth

Surface Area

3.1

Drainage Area

0.07

Nid Storage

41

Hazard Potential

Low

Foundations

Soil

Nid Height

32
       
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.