Mcslay Reservoir Report

Last Updated: December 5, 2025

Mcslay, John Estate is a privately owned earth dam located in Hill, Montana, along Nelson Coulee.


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Summary

Built in 1947 by the USDA NRCS, this dam serves multiple purposes including fire protection, water storage for livestock, and as a small fish pond. With a height of 20 feet and a length of 490 feet, this dam has a storage capacity of 113 acre-feet, with a normal storage level of 58 acre-feet.

Managed by the Montana Department of Natural Resources and Conservation (DNRC), Mcslay, John Estate has a low hazard potential and a moderate risk assessment rating. Despite not having a current condition assessment, the dam is regularly inspected, with state permitting, inspection, and enforcement in place to ensure its safety and compliance with regulations. The spillway width is 40 feet, allowing for a maximum discharge of 180 cubic feet per second in the event of overflow.

Located in a scenic area of Havre, Montana, Mcslay, John Estate is a vital water resource for the local community, providing essential services for both fire protection and irrigation. With a rich history dating back to its construction in the mid-20th century, this dam continues to play a crucial role in water management and conservation efforts in the region.

Year Completed

1947

Dam Length

490

Dam Height

20

River Or Stream

NELSON COULEE

Primary Dam Type

Earth

Hydraulic Height

20

Drainage Area

3.44

Nid Storage

113

Hazard Potential

Low

Nid Height

20
       
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.