ON THIS PAGE
Big Tujunga Reservoir Restoration Project
What to Expect
Major sediment removal work takes place during the non-storm season, from April 15 to October 15. During storm season, the reservoir will continue to operate normally to provide flood protection and capture stormwater to replenish the local water supply.
Sediment removed from Big Tujunga Reservoir will be placed at the Maple Canyon Sediment Placement Site (SPS), adjacent to the reservoir. This placement location will limit hauling through surrounding communities.
Project update
Los Angeles County Public Works is preparing for sediment removal at Big Tujunga Reservoir. Environmental review is complete. The project will move forward in phases, beginning with site preparation and followed by sediment removal. Project timing will continue to be coordinated with Pacoima Reservoir and partner agencies.
Timeline
Construction
Fall 2027 to late 2031
Understanding the Need for Sediment Removal
Pacoima Reservoir is part of LA County’s flood control system. The reservoir and dam are designed to reduce flood risk for downstream communities and capture stormwater for groundwater basin replenishment. As stormwater flows into the reservoir, it carries natural material like rocks, soil, sand, and vegetation. That material, called sediment, settles in the reservoir over time.
Wildfires increase sediment build-up because they burn away the vegetation that normally helps keep soil in place. At Big Tujunga, the 2009 Station Fire burned 87% of the watershed, which has led to much more sediment washing into the reservoir.
Vegetation
Trees, plants, and shrubs all have roots that hold sediment (rocks, mud and soil) in place.
Wildfires
When wildfires occur, vegetation is burned away. There are fewer roots to hold sediment in place.
Erosion
Storms carry sediment downhill and into reservoirs and debris basins.
That sediment takes up space the reservoir needs to capture stormwater for flood protection and to support groundwater recharge, which helps replenish local groundwater basins. Removing sediment will restore needed space in the reservoir and help keep the dam operating safely and reliably.
Why Action is Needed Now
This project is moving forward now because wildfire impacts and repeated storms have significantly reduced reservoir capacity. Restoring that capacity is necessary to protect surrounding communities and maintain safe, reliable operations.
During major storms, these facilities help reduce the risk of flooding and debris flows that can threaten nearby communities. Maintaining their capacity is an important part of keeping that protection in place.
Supporting Groundwater Recharge
Groundwater recharge is the process of letting captured stormwater soak into the ground and refill underground aquifers. In LA County, groundwater supplies about 30–40% of the county’s water.
Restoring capacity at Big Tujunga Reservoir helps preserve space to capture stormwater and support downstream recharge. Water released from Big Tujunga Dam moves to downstream spreading grounds, including the Tujunga Spreading Grounds in Sun Valley and the Hansen Spreading Grounds, replenishing the San Fernando Groundwater Basin and supporting water supply in the San Fernando Valley.
Since October 1, 2025, Hansen Spreading Grounds has captured and recharged about 22,000 acre-feet (7.2 billion gallons) of stormwater. Across all stormwater capture facilities, LA County captured a record 122.7 billion gallons of stormwater, enough to meet the needs of about 3 million residents for a year. Big Tujunga is one part of this larger countywide system.
Fire Response and Water Supply
Big Tujunga Reservoir is a flood control reservoir, not a drinking water reservoir. It is not connected to household taps or fire hydrants. While it has occasionally been accessed by aircraft for firefighting, that use has been limited. Over the past 10 years, water for aerial firefighting operations has been drawn from Big Tujunga twice.
Most firefighting water, especially for neighborhood and structure fires, comes from municipal water systems, including hydrants, tanks, and pipelines operated by local water agencies. The reservoir is not part of this municipal water system. Moreover, fire response does not rely on a single source. Depending on what is safest and most effective, agencies draw from a broad range of regional water sources to support suppression efforts.
Public Works is coordinating closely with local fire agencies, such as LACoFD, to maintain fire response capabilities throughout this work. The County is developing a staggered approach to reduce the amount of time the Big Tujunga and Pacoima Reservoirs are drawn down at the same time, although some overlap may occur depending on the phase of work. The County is coordinating with fire agencies to identify alternate water sources for firefighting purposes during construction periods.
Frequently Asked Questions
Answers to common questions.
What is sediment?
Sediment is natural material from the surrounding hillsides, including rocks, soil, sand, and vegetation. Under normal conditions, plants and trees help hold this material in place. After a wildfire, that vegetation is gone, and rain can wash large amounts of sediment into reservoirs and debris basins much more quickly. This is a natural process, but the scale has increased significantly due to wildfire activity in recent years.
Why is this project happening now?
The need for this project has been building for years, but wildfire activity has accelerated the problem. The Station Fire burned 87% of the watershed that drains into Big Tujunga Reservoir. Since then, storms have carried much larger volumes of sediment into the reservoir. The project is moving forward now to proactively address this buildup and ensure the facility continues to function as designed, providing adequate flood protection and maximizing stormwater capture to support a sustainable local water supply.
What happens if the sediment is not removed?
If sediment continues to accumulate:
- The reservoir will have reduced capacity to capture stormwater
- Flood risk could increase for downstream communities
Where will the sediment go?
Sediment will be transported to Maple Canyon Sediment Placement Site (SPS), an existing County sediment placement site in Big Tujunga Canyon. It is important to note that sediment is natural material, not hazardous waste.
Why does the reservoir need to be drained?
The reservoir will be drawn down only during the dry season (April 15 – October 15). Lower water levels allow crews to safely reach and remove accumulated sediment. During storm season, it will operate normally to manage stormwater, reduce flood risk and capture water for local supply.
Will this affect wildfire response or water availability?
No. This project will not diminish the region’s overall wildfire response capacity. Over the past 10 years, Big Tujunga has been used for aerial firefighting operations twice. Fire suppression depends on a broader network of municipal infrastructure, including hydrants, tanks, and pipelines operated by local water agencies. Big Tujunga Reservoir is part of the County’s flood control system, not the municipal drinking water system that supplies neighborhood fire hydrants.
The County will continue coordinating with local fire agencies to plan for and identify alternate water sources for firefighting during construction periods.
This project will improve long-term water reliability by increasing the reservoir’s capacity to capture stormwater, which is used to recharge groundwater basins that supply drinking water.
How long will the project take?
The project is expected to take five years or less. This schedule will help manage environmental impacts and maintain safe reservoir operations throughout the work.
Project Maps
Coming soon.
Resources
Contact & Stay Informed
Community input is an important part of the process. Residents can sign up for project updates. Public Works will continue to provide updates as the project progresses.
LA County Public Works 24-hour Dispatch Center
800-675-HELP (4357)
LA County Public Works