O'Neill Forebay Dike dam
O'Neill Forebay Dike
The O'Neill Forebay Dike in California, managed by the Bureau of Reclamation, serves a primary purpose of hydroelectric power generation. This earth dam, completed in 1966, stands at a height of 16 feet and spans 1120 feet in length. It is situated on the San Luis Creek in Merced County, California, and has a maximum storage capacity of 64,800 acre-feet, with a normal storage level of 56,430 acre-feet.
Despite being classified as low hazard potential, the O'Neill Forebay Dike poses a high risk due to its condition assessment being marked as "Not Available." The dam has not been modified over the years, and there is no spillway in place. While it does not fall under state jurisdiction, the Bureau of Reclamation oversees its operations, inspections, and regulatory aspects. Emergency action plans have been prepared, but their compliance with guidelines and inundation maps are not currently available.
For water resource and climate enthusiasts, the O'Neill Forebay Dike represents an integral part of California's hydroelectric infrastructure. Its strategic location and design contribute to the state's renewable energy goals while also highlighting the importance of regular maintenance and risk management for dam safety. With its historical significance and ongoing operational oversight by federal agencies, the O'Neill Forebay Dike serves as a reminder of the critical role dams play in water resource management and climate resilience.
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 O'Neill Forebay Dike -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Mud Slough Nr Gustine Ca | 33 cfs | → |
| Orestimba C Nr Newman Ca | · | → |
| Salt Slough A Hwy 165 Nr Stevinson Ca | 24 cfs | → |
| San Joaquin R A Fremont Ford Bridge Ca | 263 cfs | → |
| San Joaquin R Ab Merced R Nr Newman Ca | 294 cfs | → |
| San Joaquin R Nr Newman Ca | 486 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near O'Neill Forebay Dike.
Boat launches
Campgrounds
- San Luis Creek - San Luis Reservoir
- Medeiros State Rec Area - San Luis Reservoir
- Basalt State Rec Area - San Luis Reservoir
- Los Banos Creek - San Luis Reservoir
- George Hatfield State Rec Area
- Wilson Camp
Fishing spots
- Oneill Forebay
- O&Acute;Neill Forebay
- San Luis Reservoir
- Los Banos Reservoir
- Coyote Lake
- San Justo Reservoir
Paddle runs
Track O'Neill Forebay Dike 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 O'Neill Forebay Dike
Where does the data for O'Neill Forebay Dike 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 O'Neill Forebay Dike.