Hopkinton Sewage Lagoon Dam Reservoir Report
Nearby: Hopkinton Hopkinton Dam - Dike H-3
Last Updated: December 16, 2025
The Hopkinton Sewage Lagoon Dam in Merrimack, New Hampshire, stands as a crucial water resource management structure owned by the local government.
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Summary
Completed in 1983, this earth dam with a height of 18 feet serves a primary purpose that goes beyond typical water retention functions. With a storage capacity of 12 acre-feet, it plays a significant role in the region's wastewater treatment system while also providing a surface area of 1.6 acres for environmental support.
Despite its modest size, the Hopkinton Sewage Lagoon Dam is subject to stringent state regulations, inspections, and enforcement by the NHDES Dam Bureau. The dam's hazard potential is considered significant, with a high-risk assessment due to its condition and location. While the dam is currently rated as satisfactory, regular inspections every four years ensure its continued safe operation and mitigate potential risks. The absence of a spillway and outlet gates underscores the critical importance of proactive risk management measures for the dam and surrounding area.
Year Completed |
1983 |
Dam Length |
380 |
Dam Height |
18 |
River Or Stream |
NA |
Primary Dam Type |
Earth |
Surface Area |
1.6 |
Drainage Area |
1.6 |
Nid Storage |
12 |
Hazard Potential |
Significant |
Foundations |
Unlisted/Unknown |
Nid Height |
18 |
Seasonal Comparison
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Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Hopkinton Sewage Lagoon Dam
Depot Lane Hopkinton
Sewall'S Island To Manchester Street Bridge