Twelvemile Creek Watershed Site D-41-A2 Reservoir Report
Last Updated: December 12, 2025
Twelvemile Creek Watershed Site D-41-A2, located in Grand River, Iowa, is a local government-owned earth dam completed in 1999 by the USDA NRCS.
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Summary
This dam serves multiple purposes including fire protection, stock, small fish pond, and flood risk reduction. With a height of 38 feet and a length of 544 feet, the dam has a storage capacity of 411 acre-feet and covers a surface area of 13.3 acres, with a drainage area of 1.56 square miles. The dam is regulated by the Iowa DNR and is considered to have a low hazard potential, with a moderate risk assessment rating.
Managed by the Natural Resources Conservation Service, Twelvemile Creek Watershed Site D-41-A2 plays a crucial role in mitigating potential flooding and providing water resource management for the surrounding area. The dam is equipped with an uncontrolled spillway and is designed to handle a maximum discharge, although the hydraulic height is currently recorded as zero. While the condition of the dam has not been formally assessed, it is considered to be in satisfactory condition, with no reported incidents or emergencies.
Despite its low hazard potential, Twelvemile Creek Watershed Site D-41-A2 remains an essential piece of infrastructure for the community, ensuring the safety and well-being of residents in Union County, Iowa. As climate change continues to impact water resources, the proper maintenance and regulation of this dam are vital in safeguarding against potential risks and maintaining the overall resilience of the watershed. With continued inspection and adherence to regulatory guidelines, this dam will continue to serve its purpose effectively for years to come.
Year Completed |
1999 |
Dam Length |
544 |
Dam Height |
38 |
River Or Stream |
TWELVEMILE CREEK |
Primary Dam Type |
Earth |
Surface Area |
13.3 |
Drainage Area |
1.56 |
Nid Storage |
411 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
38 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Thompson River At Davis City
|
22cfs |
East Fork 102 River At Bedford
|
1cfs |
Raccoon River At Van Meter
|
1640cfs |
South Raccoon River At Redfield
|
268cfs |
North River Near Norwalk
|
48cfs |
Raccoon River Near West Des Moines
|
1300cfs |
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.
Twelvemile Creek Watershed Site D-41-A2
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