Holyoke - Overflow No. 4 Reservoir Report

Last Updated: December 6, 2025

Holyoke - Overflow No.


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Summary

4, located in Holyoke, Massachusetts, is a vital structure owned by the local government and managed by the Federal Energy Regulatory Commission (FERC). Constructed in 1891, this masonry dam serves the primary purpose of hydroelectric power generation while also providing recreational opportunities. With a height of 22.5 feet and a storage capacity of 26,000 acre-feet, this dam plays a crucial role in the region's water resource management.

The dam is situated on the Holyoke Canal, within the Hampden County of Massachusetts, and has a controlled spillway width of 150 feet. It has a low hazard potential and a very high risk assessment rating, making it essential to ensure proper maintenance and risk management measures. With four slide (sluice gate) outlet gates and a maximum discharge capacity of 950 cubic feet per second, Holyoke - Overflow No. 4 is a significant infrastructure contributing to the area's water supply and energy needs.

Despite not being state-regulated, the dam undergoes regular inspections by FERC, with the last inspection conducted in September 2017. The structure has a rich history of serving the community for over a century and continues to be a key component in the water resource infrastructure of the region. As a notable example of early hydroelectric development in the area, Holyoke - Overflow No. 4 stands as a reminder of the intersection between water resources, climate, and sustainable energy practices.

Year Completed

1891

Dam Length

150

Dam Height

22.5

River Or Stream

Holyoke Canal

Primary Dam Type

Masonry

Surface Area

2290

Drainage Area

8309

Nid Storage

26000

Outlet Gates

Slide (sluice gate) - 4

Hazard Potential

Low

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.