Foothills Reservoir Report

Last Updated: December 5, 2025

Located in Boulder, Colorado, the Foothills dam stands as a testament to early 20th-century engineering, with construction completed in 1911 for the primary purpose of irrigation.


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Summary

This private-owned structure, designed by R.E. Richardson, Rocky Mountain Consultants, and Smith Geotechnical, boasts an earth dam type with a core made of stone and foundations in rock and soil. Standing at a height of 52 feet and a length of 3150 feet, Foothills reservoir has a normal storage capacity of 4139 acre-feet and serves as a vital water resource along the St. Vrain Creek-TR.

Over the years, Foothills has undergone multiple modifications to enhance its structural and hydraulic integrity, with significant upgrades in 1987, 2001, and 2001. The dam's spillway, with a width of 222 feet, is uncontrolled, while its hazard potential is classified as high, though its condition assessment remains satisfactory. With a risk assessment rating of moderate, Foothills continues to be closely monitored through regular state inspections and enforcement to ensure its safety and functionality for the surrounding community in Longmont and beyond.

Years Modified

1987 - Structural, 2001 - Hydraulic, 2001 - Structural

Year Completed

1911

Dam Length

3150

Dam Height

52

River Or Stream

ST. VRAIN CREEK-TR

Primary Dam Type

Earth

Surface Area

183

Hydraulic Height

52

Drainage Area

1

Nid Storage

4983

Structural Height

56

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

56
       
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.