Grayrocks Reservoir Report
Nearby: Whalen Diversion Dam Guernsey
Last Updated: December 5, 2025
Grayrocks is a significant Earth dam located on the Laramie River in Fort Laramie, Wyoming.
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Summary
Built in 1980, this dam stands at a height of 95 feet and has a storage capacity of 194,000 acre-feet, with a normal storage level of 104,110 acre-feet. The dam plays a crucial role in flood control and water supply management for the region, covering a surface area of 3,547 acres and draining a watershed area of 4,484 square miles.
Managed by a public utility, Grayrocks is regulated by the State of Wyoming and is subject to regular inspections and enforcement measures to ensure its structural integrity and safety. The dam's spillway, with a width of 14 feet, is designed as uncontrolled, and the outlet gates consist of a single valve. Despite being categorized as having a high hazard potential, the dam's condition assessment is deemed fair, with a moderate risk rating of 3. While there are no associated structures, Grayrocks remains a critical infrastructure for the community, contributing to water resource management and climate resilience efforts in the area.
Overall, Grayrocks represents a vital component of the water resource infrastructure in Platte, Wyoming, serving multiple purposes beyond flood control, including irrigation, recreation, and wildlife habitat enhancement. With a designer name of Forest M. Kepler, the dam stands as a testament to engineering ingenuity and environmental stewardship. As climate change impacts intensify, the importance of structures like Grayrocks in ensuring the sustainability and resilience of water resources in the region cannot be overstated, making it a focal point for water resource and climate enthusiasts alike.
Year Completed |
1980 |
Dam Length |
2625 |
Dam Height |
95 |
River Or Stream |
LARAMIE RIVER |
Primary Dam Type |
Earth |
Surface Area |
3547 |
Hydraulic Height |
74 |
Drainage Area |
4484 |
Nid Storage |
194000 |
Structural Height |
95 |
Outlet Gates |
Valve - 1 |
Hazard Potential |
High |
Foundations |
Soil |
Nid Height |
95 |
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 |
|---|---|---|
Grayrocks Reservoir Public Access - WGF
|
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Larson Park
|
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Guernsey State Park
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Grayrocks