G&J Heck No.1 Reservoir Report
Nearby: G&J Heck No.2 R. Clark No.1
Last Updated: December 13, 2025
G&J Heck No.1 is a privately owned dam located in Dewey, South Dakota, along the TR-GRAND river.
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Summary
Built in 1937, this earth dam stands at a height of 15 feet and has a storage capacity of 90 acre-feet. The dam serves the primary purpose of water resource management and flood control in the area, with a low hazard potential and a current condition assessment of "Not Rated".
Managed by the South Dakota Department of Environment and Natural Resources (DENR), G&J Heck No.1 is regulated, inspected, and enforced by the state agency to ensure its safety and structural integrity. The dam has a maximum discharge capacity of 3150 cubic feet per second and a normal storage capacity of 40 acre-feet. Despite not having an official Emergency Action Plan (EAP) in place or a condition assessment date listed, the dam is considered to meet guidelines for risk management measures.
Overall, G&J Heck No.1 plays a crucial role in water resource management in the area, providing essential flood control and storage capacity. With its low hazard potential and state regulation, the dam continues to serve its purpose effectively while being monitored and maintained by the appropriate authorities.
Year Completed |
1937 |
Dam Length |
475 |
Dam Height |
15 |
River Or Stream |
TR-GRAND |
Primary Dam Type |
Earth |
Hydraulic Height |
15 |
Nid Storage |
90 |
Hazard Potential |
Low |
Nid Height |
15 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Moreau R Near Whitehorse Sd
|
35cfs |
Grand R At Little Eagle Sd
|
47cfs |
Moreau R Near Faith Sd
|
14cfs |
Cedar Creek Nr Raleigh
|
20cfs |
Oak Cr Near Wakpala Sd
|
10cfs |
Cannonball River Nr Raleigh
|
40cfs |
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.
G&J Heck No.1