Union Auxiliary No. 2 dam
Union Auxiliary No. 2
Union Auxiliary No. 2, located in Dorrington, California, is a privately owned rockfill dam with a primary purpose of hydroelectric power generation. This dam is regulated by the California Department of Water Resources and is also inspected and enforced by federal agencies like the Federal Energy Regulatory Commission. With a height of 7 feet and a hydraulic height of 6 feet, Union Auxiliary No. 2 has a storage capacity of 3,283 acre-feet and serves multiple purposes including recreation and water supply for the surrounding area.
Situated on the North Fork Stanislaus River, Union Auxiliary No. 2 has a spillway width of 40 feet and a surface area of 215 acres. The dam has a low hazard potential and a moderate risk assessment rating. Although the condition assessment is not available, the Emergency Action Plan was last revised in December 2020, indicating the dam's readiness for any potential emergencies. Despite its relatively small size, Union Auxiliary No. 2 plays a significant role in water resource management and climate resilience in the Alpine County, California region.
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 Union Auxiliary No. 2 -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| E F Carson R Bl Markleeville C Nr Markleevilleca | 1,110 cfs | → |
| West Fork Carson River At Woodfords | 286 cfs | → |
| Upper Truckee R At S Upper Truckee Rd Nr Meyers Ca | 4 cfs | → |
| Leviathan Mine Adit Drain Nr Markleeville Ca | 0 cfs | → |
| Leviathan C Ab Mine Nr Markleeville Ca | 0 cfs | → |
| Leviathan C Channel Underdrain Nr Markleeville Ca | 0 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Union Auxiliary No. 2 .
Boat launches
Campgrounds
- Union Reservoir East
- Union East Campground
- Union West Campground
- Utica Reservoir Campgrounds
- Spicer Meadow
- Spicer Reservoir Campground
Fishing spots
Paddle runs
- Confluence With Clark Fork To Donnell Reservoir
- State Highway 108 To Donnell Reservoir
- Highway 4 To Salt Springs Reservoir
- Salt Springs Reservoir Dam To To A Point 1 Mile West Of Bear River Confluence
- Wilderness Boundary To Confluence With Middle Fork Stanislaus
- Headwaters To Wilderness Boundary
Track Union Auxiliary No. 2 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 Union Auxiliary No. 2
Where does the data for Union Auxiliary No. 2 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 Low 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 Union Auxiliary No. 2 .