Twin Falls Auxiliary Spillway dam
Twin Falls Auxiliary Spillway
Located on the Menominee River in Iron Mountain, Michigan, the Twin Falls Auxiliary Spillway is a concrete dam with a primary purpose of hydroelectric power generation. Designed by Mead & Hunt and completed in 1960, this structure stands at a height of 30 feet and has a hydraulic height of 16.4 feet. With a maximum discharge capacity of 58,900 cubic feet per second, this controlled spillway has a width of 81 feet and a length of 101 feet.
The Twin Falls Auxiliary Spillway has a normal storage capacity of 9,750 acre-feet and serves multiple purposes including hydroelectric power generation and recreational activities. The dam is situated in a high hazard potential area with a very high risk assessment rating. Despite not being state regulated, the Federal Energy Regulatory Commission oversees its operations, inspections, and regulatory compliance. While its condition assessment is not available, the spillway has not undergone any modifications in recent years and its emergency action plan was last revised in 2005.
With its strategic location and significant role in water resource management, the Twin Falls Auxiliary Spillway stands as a crucial infrastructure for the region. Its efficient design, impressive storage capacity, and controlled spillway feature make it a key asset for both energy production and recreational use along the Menominee River. As climate and water resource enthusiasts, understanding the importance of maintaining and monitoring this dam is essential for ensuring the safety and sustainability of the surrounding area.
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 Twin Falls Auxiliary Spillway -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Menominee River At Twin Falls Near Iron Mt | 3,420 cfs | → |
| Pine River Below Pine R Powerplant Nr Florence | 259 cfs | → |
| Menominee River Near Florence | 1,210 cfs | → |
| Menominee River At Niagara | 1,180 cfs | → |
| Brule River Near Commonwealth | 572 cfs | → |
| Paint River Nr Alpha | 299 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Twin Falls Auxiliary Spillway .
Boat launches
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Campgrounds
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Fishing spots
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River runs
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About Twin Falls Auxiliary Spillway
Where does the data for Twin Falls Auxiliary Spillway 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 below 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.
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.