Colebrook Sewage Lagoon Dam Reservoir Report

Last Updated: December 7, 2025

Colebrook Sewage Lagoon Dam, located in Coos County, New Hampshire, serves as a vital water resource management structure for the city of Colebrook.


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Summary

Built in 1980, this earth dam stands at a height of 15 feet and has a length of 3100 feet, providing a storage capacity of 24 acre-feet. Despite having no spillway, the dam is designed to handle significant hazard potential with a satisfactory condition assessment.

Managed by the local government and regulated by the New Hampshire Department of Environmental Services Dam Bureau, Colebrook Sewage Lagoon Dam is inspected every four years to ensure its structural integrity and functionality. With a high risk assessment rating of 2, the dam's risk management measures are crucial in mitigating any potential emergencies or inundation events. Although primarily serving as a sewage lagoon, this dam plays a crucial role in maintaining water quality and quantity in the region.

For water resource and climate enthusiasts, Colebrook Sewage Lagoon Dam presents an intriguing case study of a multifunctional earth dam that addresses both water management and environmental concerns. With its location in a pristine natural setting, the dam's efficient design and operation highlight the importance of sustainable water infrastructure in mitigating climate-related challenges. As efforts continue to enhance its risk management measures and emergency preparedness, Colebrook Sewage Lagoon Dam stands as a crucial asset in the region's water resource management framework.

Year Completed

1980

Dam Length

3100

Dam Height

15

River Or Stream

NA

Primary Dam Type

Earth

Surface Area

3

Nid Storage

24

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

15
       
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.