Tolt River - South Fork dam
Tolt River - South Fork
The Tolt River - South Fork dam, also known as Tolt Main Dam, is a key structure owned by the local government in King County, Washington. Completed in 1962, this earth dam stands at a height of 200 feet and serves primarily for water supply purposes. With a maximum storage capacity of 68,400 acre-feet and a normal storage of 57,500 acre-feet, the dam plays a crucial role in ensuring reliable water supply to the surrounding area.
Located in Carnation, Washington, the Tolt River - South Fork dam is regulated by the Federal Energy Regulatory Commission and has a high hazard potential due to its size and location. The dam's spillway, which is uncontrolled and 40 feet wide, helps manage excess water flow during peak discharge events. The dam's inspection frequency is set at 1 year, with the last inspection conducted in September 2020. Although the current condition assessment is not available, the emergency action plan was last revised in January 2021.
Water resource and climate enthusiasts will appreciate the Tolt River - South Fork dam for its critical role in water supply management and its impact on the surrounding ecosystem. As a key structure in the region, the dam's risk assessment is moderate, highlighting the need for ongoing monitoring and management measures to ensure its safety and reliability. The dam's association with the Federal Energy Regulatory Commission underscores its importance in the broader context of energy and water resource regulatory frameworks.
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 Tolt River - South Fork -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| South Fork Tolt River Near Carnation | 67 cfs | → |
| South Fork Tolt River Near Index | 9 cfs | → |
| Sf Tolt River Bl Regulating Basin Nr Carnation | 73 cfs | → |
| North Fork Tolt River Near Carnation | 68 cfs | → |
| Nf Snoqualmie River Near Snoqualmie Falls | 144 cfs | → |
| Tolt River Near Carnation | 202 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Tolt River - South Fork.
Boat launches
- King County
- Lake Langlois Road Northeast King County
- Lake Marcel Community Park
- Northeast Tolt Hill Road 30348-30762, Carnation
- Southeast Fish Hatchery Road 36495-37159, Fall City
- Stevens Pass Highway Sultan
Paddle runs
- Confluence Of Tye And Foss Rivers To Gold Bar
- Confluence With Troublesome Creek To Confluence With South Fork Skykomish River
- Alpine Lakes Wilderness Boundary To Quartz Creek Road
- Headwaters In Se1/4 Of Sec 31, T24 1/2n, R11e To Alpine Lakes Wilderness Boundary
- Quartz Road To Confluence With Middle Fork Snoqualmie River
- Snoqualmie Falls To Plum's Landing
Track Tolt River - South Fork 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 Tolt River - South Fork
Where does the data for Tolt River - South Fork 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 Tolt River - South Fork.