Sanborn Reservoir Report

Last Updated: December 5, 2025

Sanborn is a privately owned dam located in Longmont, Colorado, along the St.


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Summary

Vrain Creek. Built in 1890 for irrigation purposes, this earth dam stands at 16 feet tall and spans 2300 feet in length. With a storage capacity of 284 acre-feet and a normal storage of 214 acre-feet, Sanborn plays a crucial role in managing water resources in the area.

Despite being classified as having low hazard potential and a satisfactory condition assessment, Sanborn underwent its last inspection in September 2013. With a moderate risk assessment rating, there is a need for continued monitoring and potential risk management measures to ensure the dam's safety and functionality. The dam features an uncontrolled spillway type with a width of 30 feet, allowing for a maximum discharge of 640 cubic feet per second.

Sanborn serves as a vital component of the water infrastructure in Weld County, Colorado, providing irrigation water for agricultural purposes. With its historical significance and ongoing role in water resource management, Sanborn showcases the intersection of tradition, engineering, and climate resilience in the region. As water resource and climate enthusiasts, understanding the intricacies of dams like Sanborn can offer valuable insights into sustainable water management practices and the importance of infrastructure maintenance in the face of changing environmental conditions.

Year Completed

1890

Dam Length

2300

Dam Height

16

River Or Stream

ST. VRAIN CREEK

Primary Dam Type

Earth

Surface Area

35

Hydraulic Height

16

Drainage Area

1

Nid Storage

284

Structural Height

16

Hazard Potential

Low

Nid Height

16
       
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.