Upper Ansonia Reservoir East Dike Reservoir Report
Last Updated: December 5, 2025
Upper Ansonia Reservoir East Dike, also known as Upper Derby Hill Reservoir, is a masonry dam located in Derby, Connecticut, owned by the local government and regulated by the Department of Energy and Environmental Protection (DEEP).
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Summary
The dam stands at a height of 12 feet and stretches 345 feet in length, with a fair condition assessment as of May 2017. The reservoir has a high hazard potential, with an inspection frequency of every 2 years to ensure public safety.
Situated in New Haven County, Upper Ansonia Reservoir East Dike serves as a crucial water resource for the region, although its normal storage capacity is listed as zero. The dam has no spillway and associated structures, with no outlet gates identified. While the dam was last inspected in August 2015, there is no information available on the year of completion or the purposes of the reservoir. Despite its fair condition, the dam's hazard potential underscores the importance of regular inspections and maintenance to prevent potential risks.
As climate and water resource enthusiasts delve into the details of Upper Ansonia Reservoir East Dike, its significance in the local water management system becomes apparent. With a high hazard potential and fair condition, the dam's role in providing water storage and flood control underscores the need for continued monitoring and management to ensure its structural integrity and public safety. As a key infrastructure in the region, the reservoir's upkeep and regulatory oversight by DEEP reflect the ongoing efforts to safeguard water resources in Connecticut and mitigate potential risks associated with dam failures.
Dam Length |
345 |
Dam Height |
12 |
Primary Dam Type |
Masonry |
Outlet Gates |
None |
Hazard Potential |
High |
Foundations |
Rock, Soil |
Nid Height |
12 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Housatonic River At Stevenson
|
455cfs |
Naugatuck River At Beacon Falls
|
258cfs |
Mill R Nr Hamden
|
20cfs |
Rooster River At Fairfield
|
3cfs |
Pootatuck R At Sandy Hook
|
24cfs |
Pomperaug River At Southbury
|
71cfs |
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.
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