Blackmer #1 Reservoir Report

Nearby: Skeel Holly

Last Updated: December 5, 2025

Blackmer #1 is a privately owned irrigation dam located in Arapahoe County, Colorado, along the South Platte River.


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Summary

Built in 1936, this earth dam stands at a height of 12 feet and has a hydraulic height of 8 feet, with a length of 488 feet. The dam serves primarily for irrigation purposes, with a storage capacity of 69 acre-feet and a normal storage of 37 acre-feet.

Despite being classified as having a low hazard potential, Blackmer #1 underwent a satisfactory condition assessment in 2016. The dam features an uncontrolled spillway with a width of 67 feet and has a maximum discharge of 2000 cubic feet per second. While the risk assessment for the dam is moderate, there are no specific risk management measures or emergency action plans in place as of the last inspection date in 2016.

For water resource and climate enthusiasts, Blackmer #1 offers an intriguing case study of an early 20th-century irrigation structure in Colorado. Its location on the South Platte River and its role in water management make it a significant piece of the region's hydrological landscape. As discussions around dam safety and risk management continue, Blackmer #1 serves as a reminder of the importance of maintaining and monitoring critical infrastructure in the face of changing environmental conditions.

Year Completed

1936

Dam Length

488

Dam Height

12

River Or Stream

SOUTH PLATTE RIVER-TR

Primary Dam Type

Earth

Surface Area

8

Hydraulic Height

8

Drainage Area

1

Nid Storage

69

Structural Height

12

Outlet Gates

Drum - 0

Hazard Potential

Low

Nid Height

12
       
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.