Pierce Mills Reservoir Report

Last Updated: December 16, 2025

Pierce Mills is a historic hydroelectric dam located on the Passumpsic River in St.


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Summary

Johnsbury, Vermont. Built in 1928, this concrete gravity dam stands at a height of 19 feet and has a length of 140 feet. With a storage capacity of 300 acre-feet, it serves as a key source of hydroelectric power in the area. The dam is owned by a public utility and is not state-regulated, making it an important asset for the local community.

The dam has a low hazard potential and is currently rated as "Not Rated" in terms of its condition assessment. Despite not being regularly inspected or permitted by state agencies, Pierce Mills continues to operate efficiently, providing clean and renewable energy to the region. The last inspection of the dam was conducted in May 2000, and it meets all necessary safety guidelines. The surrounding area is at low risk for inundation, and emergency preparedness plans are in place to ensure the safety of nearby residents in the event of a dam failure.

With its picturesque location on the Passumpsic River and its important role in supplying hydroelectric power, Pierce Mills remains a significant landmark in Caledonia County, Vermont. As a multi-arch dam with a solid foundation on rock and soil, it represents a sustainable and reliable source of renewable energy. Climate and water resource enthusiasts will appreciate the historical significance and environmental impact of this well-maintained dam.

Year Completed

1928

Dam Length

140

Dam Height

19

River Or Stream

PASSUMPSIC RIVER

Primary Dam Type

Concrete

Surface Area

1

Hydraulic Height

19

Drainage Area

237

Nid Storage

300

Structural Height

23

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

23
       
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.