Hillsborough Sewage Lagoon Dam Reservoir Report

Last Updated: December 19, 2025

The Hillsborough Sewage Lagoon Dam in Hillsborough, New Hampshire, is a local government-owned structure that serves a critical purpose in managing wastewater in the area.


°F

°F

mph

Wind

%

Humidity

Summary

Completed in 1984, this earth dam stands at a height of 12 feet and stretches for 2000 feet, providing storage for up to 11 acre-feet of water. Despite not having a spillway, the dam is regulated by the NHDES Dam Bureau and undergoes regular inspections to ensure its safety.

With a significant hazard potential and a high risk assessment rating, the Hillsborough Sewage Lagoon Dam is a key infrastructure piece in the region's water resource management. While the condition assessment is currently listed as "Not Rated," the dam is subject to frequent inspections and emergency action plans are likely in place to address any potential issues. Its location in a densely populated area underscores the importance of maintaining its structural integrity to prevent any environmental or public safety risks.

As climate change continues to impact water resources and infrastructure, the Hillsborough Sewage Lagoon Dam stands as a crucial component in the local ecosystem. With the potential for increased extreme weather events, ensuring the resilience and safety of this dam is essential for protecting the surrounding community and maintaining the integrity of the water resource infrastructure.

Year Completed

1984

Dam Length

2000

Dam Height

12

River Or Stream

NA

Primary Dam Type

Earth

Surface Area

2

Nid Storage

11

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

12
       
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.