Middle Br. Park River #9 Reservoir Report

Last Updated: December 7, 2025

Middle Br.


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Summary

Park River #9, also known as Union Dam, is a local government-owned structure located in Grafton, North Dakota. Built in 1970 by the USDA NRCS, this earth dam stands at 67.5 feet in height with a structural height of 74 feet and a length of 1080 feet. Its primary purpose is flood risk reduction, serving the Middle Branch Park River-TR watershed with a storage capacity of 2466.6 acre-feet.

Managed by the NDSWC, Middle Br. Park River #9 is regulated, permitted, inspected, and enforced by state agencies to ensure its safety and functionality. The dam's spillway, with a width of 250 feet, is of the uncontrolled type, and it holds a hazard potential rating of "Significant." Despite being in moderate risk condition and not having a current condition assessment, the dam continues to play a crucial role in the flood risk mitigation efforts in the region.

With its stone core and soil foundation, Middle Br. Park River #9 is a key feature in the Omaha District's water resource management infrastructure. Although not under the jurisdiction of the USACE, this dam remains a critical component in protecting the surrounding area from potential flood events, showcasing the collaborative efforts between local and federal agencies in safeguarding communities against the impacts of climate change.

Year Completed

1970

Dam Length

1080

Dam Height

67.5

River Or Stream

MIDDLE BRANCH PARK RIVER-TR

Primary Dam Type

Earth

Surface Area

9.4

Drainage Area

7.6

Nid Storage

2466.6

Structural Height

74

Outlet Gates

None

Hazard Potential

Significant

Foundations

Soil

Nid Height

74
       
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.