Main Mill Dam dam
Main Mill Dam
Main Mill Dam, also known as Imperial Dam, is a historic structure located in Plattsburgh, New York, along the Saranac River. Built in 1881, this concrete dam stands at a height of 25 feet and spans 715 feet, with a storage capacity of 920 acre-feet. Primarily used for hydroelectric purposes, the dam is owned by a private entity and is regulated by the New York State Department of Environmental Conservation.
Despite its age and significant storage capacity, Main Mill Dam has been assessed with a poor condition and a high hazard potential. The last inspection in September 2020 revealed the dam's structural deficiencies, prompting concerns about its safety and the potential risks it poses to downstream areas. With a very high risk rating of 1, it is crucial for ongoing risk management measures to be implemented to ensure the dam's integrity and the safety of surrounding communities.
As water resource and climate enthusiasts, the data on Main Mill Dam serves as a reminder of the importance of maintaining and monitoring aging infrastructure to prevent potential disasters. With its rich history and critical role in providing hydroelectric power, Main Mill Dam stands as a testament to the intersection of human ingenuity and environmental stewardship. Efforts to address its poor condition and high hazard potential will be essential in safeguarding both the dam's structural integrity and the surrounding ecosystem.
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 Main Mill Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Saranac River At Plattsburgh Ny | 1,170 cfs | → |
| Salmon River At South Plattsburgh Ny | 44 cfs | → |
| Little Ausable River Near Valcour Ny | 43 cfs | → |
| Little Chazy River Near Chazy Ny | 64 cfs | → |
| Ausable River Near Au Sable Forks Ny | 600 cfs | → |
| E Br Ausable River At Au Sable Forks Ny | 237 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Main Mill Dam.
Boat launches
- Green Street 32, Plattsburgh
- Green Street Plattsburgh
- Peru Boat Launch
- Fish Hatchery Road Grand Isle
- West Shore Road Grand Isle
- Sunrise Drive South Hero
Campgrounds
- Cumberland Bay State Park
- Primitive Campsite 13
- Primitive Campsite 14
- Primitive Campsite 16
- Primitive Campsite 20
- Primitive Campsite 19
Track Main Mill Dam 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 Main Mill Dam
Where does the data for Main Mill Dam 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 Main Mill Dam.