Union Valley dam
Union Valley
Union Valley is a captivating hydroelectric and recreational dam located in El Dorado, California. Built in 1962 by Bechtel, this Earth-type dam stands at an impressive height of 440 feet and has a storage capacity of 266,369 acre-feet, with a normal storage level of 204,000 acre-feet. The dam is situated on the Big Silver Creek and covers a surface area of 2,860 acres, providing a picturesque backdrop for outdoor enthusiasts and climate aficionados alike.
Managed by the Federal Energy Regulatory Commission, Union Valley serves as a vital water resource in California, with a maximum discharge capacity of 44,500 cubic feet per second. The dam features a controlled spillway with a width of 85 feet and two Tainter radial gates for water regulation. Despite its high hazard potential, the dam is regularly inspected and regulated by both state and federal agencies to ensure public safety and environmental protection. With its scenic location and impressive engineering, Union Valley offers a unique blend of hydroelectric power generation and recreational opportunities for visitors to enjoy.
With its rich history and strategic location in the Coloma area, Union Valley continues to play a crucial role in California's water resource management efforts. The dam's risk assessment indicates a very high level of risk, emphasizing the importance of ongoing monitoring and maintenance to safeguard its structural integrity. As a popular destination for outdoor activities and nature enthusiasts, Union Valley stands as a symbol of sustainable water utilization and climate resilience in the region, highlighting the intersection of engineering ingenuity and environmental stewardship in the face of changing climate patterns.
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 Valley -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Pilot C Ab Stumpy Meadows Res Ca | 3 cfs | → |
| Pilot C Bl Mutton Canyon Nr Georgetown Ca | 2 cfs | → |
| General C Nr Meeks Bay Ca | 16 cfs | → |
| Upper Truckee R At Hwy 50 Above Meyers Ca | 216 cfs | → |
| Blackwood C Nr Tahoe City Ca | 87 cfs | → |
| Upper Truckee R At S Upper Truckee Rd Nr Meyers Ca | 4 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Union Valley .
Boat launches
- Junction Boat Ramp Road El Dorado County
- Dry Lakes Trail El Dorado County
- Poho Ridge El Dorado County
- Ice House Road El Dorado County
- Forebay Road El Dorado County
- Sly Park Road, Pollock Pines
Campgrounds
Fishing spots
Paddle runs
- Ellicots Bridge To Big Grizzly Canyon
- Big Grizzly Canyon To Oxbow Reservoir
- Hell Hole Dam To Ellicotts Bridge
- Confluence With Van Horn Creek To Cosumnes Mine Road
- Interbay To Oxbow (End Of The World)
- Cosumnes Mine Road To Confluence With Steely Fork Cosumnes River
More reservoirs
Track Union Valley 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 Valley
Where does the data for Union Valley 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 Union Valley .