Herrick Reservoir Report
Last Updated: December 25, 2025
Herrick, located in Converse, Wyoming, is a privately owned irrigation dam constructed in 1946 by designer Albert B.
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Summary
Bartlett. This Earth-type dam on Twenty Mile Creek stands at 30 feet in height and 550 feet in length, with a storage capacity of 146 acre-feet. Despite its low hazard potential and fair condition assessment, the dam is state regulated and regularly inspected, with state permitting, inspection, and enforcement all in place to ensure its safety and compliance with regulations.
Managed by the Wyoming state agency SEO, Herrick serves the primary purpose of irrigation and has a spillway width of 100 feet for uncontrolled water release. With a moderate risk assessment rating, the dam is located in Edgemont, South Dakota, within the Congressional District 00 of Wyoming, represented by Congresswoman Liz Cheney. While the dam has a drainage area of 0 square miles and a surface area of 10 acres, it plays a crucial role in water resource management and agriculture in the region.
Despite its age, Herrick continues to support local agriculture and water supply needs, demonstrating the importance of proper dam maintenance and regulation in ensuring the sustainability of water resources. As a key structure on Twenty Mile Creek, this irrigation dam highlights the intricate balance between human development and environmental conservation in the face of changing climate patterns and increasing water demands.
Year Completed |
1946 |
Dam Length |
550 |
Dam Height |
30 |
River Or Stream |
TWENTY MILE CREEK |
Primary Dam Type |
Earth |
Surface Area |
10 |
Hydraulic Height |
20 |
Nid Storage |
146 |
Structural Height |
20 |
Outlet Gates |
Valve - 1 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
30 |
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.
Herrick