County Line Impoundment Reservoir Report
Nearby: Robert Calkinsor Duwayne Slaathaug #1
Last Updated: December 7, 2025
County Line Impoundment is a federal-owned earth dam located in Lyman, South Dakota, on Antelope Creek.
°F
°F
mph
Wind
%
Humidity
Summary
Completed in 1992, this dam stands at a height of 17 feet and has a storage capacity of 96 acre-feet. While its primary purpose is not specified, it serves as a crucial water resource for the region, with a normal storage capacity of 42 acre-feet and a drainage area of 4 square miles.
Despite being categorized as having a low hazard potential and a "Not Rated" condition assessment, County Line Impoundment has not undergone recent inspections or maintenance updates. It lacks an Emergency Action Plan (EAP) and other risk management measures, raising concerns about its readiness in the face of potential emergencies or natural disasters. With no designated outlet gates or associated structures, the dam's operations and safety protocols remain ambiguous, highlighting the need for enhanced regulatory oversight and proactive maintenance efforts to ensure the longevity and resilience of this vital water infrastructure.
As climate change continues to impact water resources and weather patterns, the importance of maintaining and monitoring dams like County Line Impoundment becomes increasingly urgent. With its strategic location on Antelope Creek, this dam plays a pivotal role in water storage and flood control for the surrounding area. Moving forward, prioritizing comprehensive inspections, risk assessments, and emergency preparedness measures will be essential to safeguarding not only the dam itself but also the communities and ecosystems that rely on its stability and functionality.
Year Completed |
1992 |
Dam Length |
600 |
Dam Height |
17 |
River Or Stream |
ANTELOPE CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
17 |
Drainage Area |
4 |
Nid Storage |
96 |
Hazard Potential |
Low |
Nid Height |
17 |
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.
County Line Impoundment