Greene Mill Dam Reservoir Report
Nearby: Marble Rock Milldam Wedeking Dam
Last Updated: December 13, 2025
Greene Mill Dam, located in Greene, Iowa along the Shell Rock River, is a historic gravity dam that was completed in 1925 for hydroelectric purposes.
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Summary
With a height of 10.67 feet and a length of 282 feet, the dam has a normal storage capacity of 385 acre-feet and serves as a vital water resource in the region. Managed by a private owner, the dam is regulated by both state and federal agencies, including the Iowa Department of Natural Resources and the Federal Energy Regulatory Commission.
Despite its age, Greene Mill Dam has a low hazard potential and is considered to be in moderate risk condition. With an uncontrolled spillway and a maximum discharge capacity, the dam plays a crucial role in managing water flow and storage in the area. Regular inspections are conducted by regulatory agencies to ensure the structural integrity and safety of the dam, with the most recent inspection taking place in July 2018. Additionally, emergency action plans are in place to mitigate any potential risks and ensure the protection of downstream communities in case of a dam failure.
Overall, Greene Mill Dam stands as a testament to early 20th-century engineering and continues to contribute to the region's water resource management and hydroelectric power generation. As an integral part of the Shell Rock River watershed, the dam's historical significance and functional importance make it a focal point for water resource and climate enthusiasts interested in sustainable infrastructure development and management.
Year Completed |
1925 |
Dam Length |
282 |
Dam Height |
10.67 |
River Or Stream |
Shell Rock |
Primary Dam Type |
Gravity |
Surface Area |
85 |
Hydraulic Height |
11 |
Drainage Area |
1357 |
Nid Storage |
385 |
Structural Height |
11 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
11 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Cedar River At Charles City
|
450cfs |
Shell Rock River At Shell Rock
|
484cfs |
Little Cedar River Near Ionia
|
70cfs |
Cedar River At Waverly
|
436cfs |
West Fork Cedar River At Finchford
|
502cfs |
Cedar River At Janesville
|
711cfs |
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.
Greene Mill Dam