Marion Reservoir Report

Last Updated: December 5, 2025

Marion is a privately owned dam located in Custer, Colorado, near the city of SAN ISABEL.


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Summary

Completed in 1909, this rockfill dam serves the primary purpose of water supply, with a normal storage capacity of 50 acre-feet. The dam stands at a height of 10 feet and has a length of 310 feet, impounding water from the AMETHYST CRK. stream.

Despite its low hazard potential, Marion poses a high risk due to its condition being labeled as 'Not Rated.' The dam lacks an Emergency Action Plan (EAP) and has not been assessed for its emergency preparedness or guideline compliance. With a drainage area of 3 square miles and a maximum discharge capacity of 150 cubic feet per second, it is crucial for stakeholders to prioritize the assessment and maintenance of Marion to ensure the safety and stability of its surrounding community and water resources.

As a water resource and climate enthusiast, monitoring Marion's risk assessment, condition assessment, and emergency preparedness measures is essential. With the potential for high risk associated with this dam, stakeholders must work towards implementing proper risk management measures and ensuring that emergency protocols are in place to mitigate any potential hazards that may arise from Marion's aging infrastructure.

Year Completed

1909

Dam Length

310

Dam Height

10

River Or Stream

AMETHYST CRK.

Primary Dam Type

Rockfill

Surface Area

10

Hydraulic Height

10

Drainage Area

3

Nid Storage

100

Structural Height

10

Hazard Potential

Low

Nid Height

10
       
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.