Lake Riley Reservoir Report

Last Updated: December 5, 2025

Lake Riley, located in Hennepin County, Minnesota, is a gravity dam constructed in 1958 with a primary purpose listed as "Other." This picturesque reservoir on Riley Creek has a normal storage capacity of 3000 acre-feet and a maximum storage capacity of 3900 acre-feet, covering a surface area of 296 acres.


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Summary

The dam stands at a height of 9 feet and has a length of 20 feet, with a low hazard potential and satisfactory condition assessment as of the last inspection in December 2015.

With a drainage area of 8.3 square miles, Lake Riley plays a crucial role in water resource management in the region, with a maximum discharge capacity of 350 cubic feet per second. Although not state-regulated, this state-owned structure provides recreational opportunities in the city of Eden Prairie. The dam's Buttress core type and unlisted/unknown foundations contribute to its structural integrity, ensuring the safety of the surrounding community and enhancing the natural beauty of the area.

Lake Riley, managed by the state of Minnesota, is a key feature in the local landscape, offering a peaceful retreat for residents and visitors alike. The dam's strategic location on Riley Creek and its vital role in flood control and water storage make it a significant asset in the region's water resource infrastructure. With its low hazard potential and satisfactory condition, Lake Riley stands as a testament to effective dam management and environmental stewardship in the face of changing climate patterns.

Year Completed

1958

Dam Length

20

Dam Height

5

River Or Stream

RILEY CREEK

Primary Dam Type

Gravity

Surface Area

296

Drainage Area

8.3

Nid Storage

3900

Structural Height

9

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

9
       
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.