PROJECT DESCRIPTION
Cogswell Dam, San Gabriel Dam, and Santa Anita Dam are vital components of the Los Angeles County flood control system. They provide flood protection for numerous residents and communities downstream along the San Gabriel and Los Angeles Rivers, while also maximizing water conservation in the county. The reservoirs also provide additional benefits such as sustaining year-round flows downstream of the dams and recharging groundwater aquifers.
The 2020 Bobcat Fire burned extensive portions of the Angeles National Forest, including portions of the watersheds tributary to Cogswell, San Gabriel, and Santa Anita Reservoirs. The lack of vegetation in the burned watersheds increases the chance of large volumes of sediment flowing into the reservoirs over the next few years. If large amounts of sediment were allowed to accumulate above current levels, it would compromise the flood control and water conservation capabilities of Cogswell, San Gabriel, and Santa Anita Dams.
In anticipation of the increased debris and sediment flows from the burned watersheds, LACFCD is proposing to remove 2.0 million cubic yards (MCY) of sediment from Cogswell Reservoir, 4.9 MCY of sediment from San Gabriel Reservoir, and 600,000 cubic yards of sediment from Santa Anita Reservoir. Excavation equipment would remove the sediment from the reservoir and transport it to an existing sediment placement site, located adjacent to each reservoir. Excavation activities would occur between April and November each year.
UPDATE: 06/20/23
Notice: Santa Anita Update
UPDATE: 04/26/21
Notice: Cogswell Update
Construction activities for the Cogswell Reservoir Post-Fire Emergency Restoration Project have commenced.
UPDATE: 04/14/21
Notice: San Gabriel Dam Update
The construction contract for the San Gabriel Reservoir Post-Fire Emergency Restoration Project was awarded to W.A. Rasic Construction Company.
UPDATE: 03/04/21
Notice: Cogswell Update
The construction contract for the Cogswell Reservoir Post-Fire Emergency Restoration Project was awarded to Griffith Company. The multi-year contract includes the restoration of utilities destroyed in the Bobcat Fire, removal of sediment from Cogswell Reservoir, and the performance of other appurtenant work in the Angeles National Forest.
UPDATE: 12/07/20
Notice: Cogswell Update
As a result of the Bobcat Fire, the U.S. Forest Service issued Forest Order No. 05-01-20-11 which prohibits public use of the West Fork Access Road. The road provides access to Cogswell Dam from Highway 39. No pedestrians, bicyclists, or motorized vehicles are allowed on the West Fork Access Road until at least April 1, 2022.
UPDATE: 10/13/20
Notice: General Update
On October 13, 2020, the Los Angeles County Board of Supervisors passed a motion instructing Los Angeles County Public Works to take immediate action to repair and restore facilities affected by the Bobcat Fire. This includes the removal of sediment from major dams and reservoirs such as Cogswell and San Gabriel Reservoirs.
Protecting the Environment
Public works will implement measures to reduce impacts to the environment, including:
- All construction activities will occur within the designated project footprint.
- Qualified biologists conducted pre-construction biological surveys for special status species and nesting birds within a 500 ft buffer of project areas.
- Qualified biologist will redirect or capture and relocate all wildlife to outside the work area prior to and during construction.
- Biological resources monitoring will be provided during construction to ensure that special status species are not impacted.
- Any special status species discovered will be relocated where avoidance not feasible.
- Workers Environmental Awareness Program (WEAP) training is provided to construction crews regarding how to identify and avoid impacts to sensitive resources that may be observed on-site.
- Earthwork areas, unpaved transport routes, etc. will be watered down to reduce dust. All diesel-powered vehicles will be equipped with model year 2013 or newer engines that conform to EPA’s emission standards.
- Haul trucks shall be manually cleaned of visible sediment and debris prior to leaving the loading area.
- All equipment and vehicles will be decontaminated and certified before entering the work site. Any equipment leaving the work site and returns will require to be re-certified.
- All equipment within the work site will be cleaned and free of materials deleterious to aquatic life, including noxious and nuisance weeds, aquatic invasive species, soil and other debris.
- Paved roads shall be maintained and cleaned continuously so that there is no visible dust, sediment, debris, or any other material that could become airborne.
- PW will follow Federal, State, and/or local regulations for discharge of smoke, dust, equipment exhaust, or any other air contaminants into the atmosphere. Flow of disturbed sediment and particulate matter will be prevented or limited to reduce particulate matter to downstream areas by using desilting basins/pumps. Desilting basins will be constructed within the reservoir to capture water and reduce turbidity prior to release from the dam.
- Surface water diversion systems will be installed to maintain natural flow rates for the downstream West Fork San Gabriel River by diverting all upstream water flow around the construction area.
- A water quality monitoring plan will be implemented during construction. Sampling data will be utilized to identify any project-related alterations to water quality and avoid/minimize potential impacts downstream.
- Fish exclusionary nets will be installed upstream and fish exclusionary screening at pipe inlets to prevent fish from entering work area.
- Access to the Burro Canyon Shooting Range will be maintained during the project.
- All temporarily impacted areas within the project site will be restored per the restoration plan approved by the regulatory agencies.
