Pacoima Dam was constructed in 1929 and provides flood protection and debris control for Sylmar, Pacoima, and other downstream communities. In addition to flood protection and debris control the dam captures stormwater for annual groundwater recharge for the San Fernando Basin. The County of Los Angeles Department of Public Works (Public Works) operates and maintains the dam and reservoir on behalf of the Los Angeles County Flood Control District (District). Please see the fact sheet for more info regarding the Dam and Reservoir.
Why remove sediment from Pacoima Dam?
Sediment must be removed to restore flood control and water conservation capacity. After the 2009 Station Fire and the 2008 Sayre and Marek Fires, storm events washed abnormally large volumes of sediment into the reservoir, thereby decreasing storage capacity and increasing the chances of plugging the outlet works with sediment or debris. In its current condition, the Reservoir does not have sufficient capacity to contain a large debris event without burying the outlet works. The lowest outlet gate, which is normally used to naturally pass sediment through the Dam is buried under 65 feet of sediment. An additional 31 feet of sediment on the upstream face of the Dam would bury the inlets for all other flood outlet valves, making them inoperable.
What is the scope of the Pacoima Reservoir Sediment Removal Project?
The scope of the proposed Project has not yet been determined. Joint scoping meetings pursuant to the California Environmental Quality Act (CEQA) and the National Environmental Protection Act (NEPA) will occur in Winter/Spring 2015. The public will be encouraged to participate during these scoping meetings to develop alternatives.
What is the timeline for the project?
In accordance with CEQA, a Notice of Preparation (NOP) to prepare an Environmental Impact Report will be published for public review on February 23, 2015. Public scoping meetings would also occur on March 25, 2015; March 26, 2015 and March 28, 2015 to garner public input on the NOP. Subsequently, the joint CEQA/NEPA document would be drafted and published for public review. The CEQA/NEPA document will disclose all the environmental impacts of the proposed Project to be determined and its alternatives for the public to review and comment on. Construction is anticipated to begin in 2017.
How do we keep up to date with the progress of the project?
The website will have the most updated information on the CEQA/NEPA process and project components. We will conduct additional outreach to the community before each scoping meeting.
Will dump trucks be driving by the Sylmar, Placerita Canyon, or Sun Valley neighborhoods as part of this project?
One of the many methods of sediment transportation that will be analyzed is hauling via trucks; however a sediment transportation method and route has not yet been selected. The Project is required to first go through the CEQA/NEPA process to analyze the environmental impacts of all feasible methods and routes of sediment transportation before a method and route is recommended.
What happens if there is an earthquake?
This dam has been retrofitted to the Division of Safety of Dams (DSOD) standards to withstand seismic events. However, the reservoir must be quickly drained in a major seismic event, which may be difficult if the lower valves remain buried in sediment.
What impact will this project have on the environment and the people of Sylmar?
The potential impacts from this Project will vary depending on what methods are used for sediment removal. Each method has its own unique impacts.
Has the District started the process to purchase the North and South Canyons immediately downstream of the dam as a new sediment placement site (SPS)?
No, the District has not decided or started the process to purchase the North and South Canyons. No decision or purchase for any of the Project options can be made until the District first complies with the CEQA/NEPA process.
Why doesn't the District place the sediment removed from the Pacoima Reservoir at the canyons (i.e. Cougar and Maple Canyons) located immediately upstream of the Dam?
The joint CEQA/NEPA document will analyze the environmental impacts associated with using Cougar and Maple Canyons as potential SPSs. Currently, Cougar and Maple Canyons do not have adequate capacity and would not be able to accept the total sediment expected to be removed with the Project.
Sylmar is a high wind area, how will this project prevent dust, ash, and particulates from getting carried away by the wind?
By recognizing that Sylmar is a high wind area, the District can design our proposed project and alternatives with design features in advance to control dust and particulates from the project site from adversely affecting adjacent communities. Also, as feasible, mitigation measures will be developed and addressed in the joint CEQA/NEPA document to further reduce air quality impacts to Sylmar and the adjacent communities.