Groll Dam; Sonja Reservoir Report
Last Updated: December 5, 2025
Groll Dam, also known as Sonja, is a privately owned structure located in Bowman, North Dakota, along the East Fork Deep Creek.
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Summary
Designed by USDA NRCS and completed in 1996, this earth dam serves multiple purposes including fire protection, stock watering, and supporting a small fish pond. With a dam height of 15.1 feet and a storage capacity of 62 acre-feet, Groll Dam is regulated by the North Dakota State Water Commission (NDSWC) and is subject to state permitting, inspection, and enforcement.
The dam's spillway, classified as uncontrolled, has a width of 165 feet to manage water flow during periods of high discharge. Groll Dam has a low hazard potential and a moderate risk assessment rating. While the condition assessment is currently not rated, the structure is deemed safe for its intended purposes. Emergency action plans have not been prepared or updated, but the risk management measures in place ensure the safety and integrity of the dam for the surrounding community and environment.
Located within the Omaha District, Groll Dam stands as a vital water resource in Bowman County, providing essential services and mitigating potential hazards. With its strategic design and efficient operation, this structure exemplifies responsible water management practices and underscores the importance of maintaining and monitoring dam infrastructure for the benefit of both people and wildlife in the region.
Year Completed |
1996 |
Dam Height |
15.1 |
River Or Stream |
EAST FORK DEEP CREEK |
Primary Dam Type |
Earth |
Surface Area |
3.5 |
Drainage Area |
7.5 |
Nid Storage |
62 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
15 |
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.
Groll Dam; Sonja