Mansfield Hollow Dam - Dike A And B dam
Mansfield Hollow Dam - Dike A And B
Mansfield Hollow Dam - Dike A and B, also known as Mansfield Hollow Lake, is a federal-owned structure located in Willimantic, Connecticut. Constructed in 1952 by the US Army Corps of Engineers, this gravity dam stands at a height of 78 feet and has a hydraulic height of 74 feet. With a dam volume of 1,458,000 cubic feet and a storage capacity of 76,000 acre-feet, it primarily serves the purpose of flood risk reduction along the Nachaug River.
Managed by the US Army Corps of Engineers, Mansfield Hollow Dam plays a crucial role in mitigating flood risks in the region by monitoring its structural health, conducting regular inspections, and engaging with local emergency managers to ensure preparedness in case of dam-related emergencies. The dam has a high hazard potential and a moderate risk assessment level, highlighting the importance of ongoing risk management measures to safeguard the surrounding communities and infrastructure. While the dam is equipped with an uncontrolled spillway and emergency action plan, efforts are continuously made to address potential flood risks and enhance public safety.
Despite its critical role in flood control, Mansfield Hollow Dam is not immune to the unpredictable nature of severe weather events and the inherent limitations of water storage capacity. As such, the US Army Corps of Engineers remains vigilant in its risk management approach, constantly working to address evolving threats and ensure the structural integrity of the dam. By collaborating with local stakeholders, maintaining emergency preparedness, and conducting necessary maintenance and repairs, the USACE strives to uphold the safety and resilience of Mansfield Hollow Dam for the benefit of the surrounding communities and environment.
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.
- 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.
- 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.
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, environmental 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.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Mansfield Hollow Dam - Dike A And B -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Natchaug River At Willimantic | 231 cfs | → |
| Willimantic River Near Coventry | 160 cfs | → |
| Shetucket River Near Willimantic | 504 cfs | → |
| Mount Hope River Near Warrenville | 40 cfs | → |
| Little River Near Hanover | 29 cfs | → |
| Yantic River At Yantic | 78 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Mansfield Hollow Dam - Dike A And B.
Boat launches
- Mansfield Hollow Dam
- Beaver Brook Pond
- Pine Acres Lake
- Coventry Lake
- Jerusalem Road South Windham
- Mono Pond
Campgrounds
Fishing spots
Paddle runs
- Begins Below The Tailrace Of The Rainbow Dam To The Confluence With The Connecticut River
- The Confluence Of The East And West Branches To The Confluence With The Farmington River In East Granby
- Begins Below The Tailrace Of The Lower Collinsville Dam To The Route 187 Bridge
- The Confluence With The Nepaug River To A Point 0.2 Miles Below The Lower Collinsville Dam Tailrace
- New Hartford/Canton Town Line To The Confluence With The Nepaug River
- The Massachusetts-Connecticut State Line In Hartland To The Confluence With The Salmon Brook Main Stem
Track Mansfield Hollow Dam - Dike A And B in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About Mansfield Hollow Dam - Dike A And B
Where does the data for Mansfield Hollow Dam - Dike A And B come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the High hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Mansfield Hollow Dam - Dike A And B.