Chabot Dam Upgrade - Frequently Asked Questions


CEQA is the California Environmental Quality Act, which requires state and local agencies such as East Bay Municipal Utility District (EBMUD) to identify the project's significant environmental impacts and to avoid or mitigate those impacts, if feasible. EBMUD will publish a draft Environmental Impact Report (EIR) that will describe the impacts of the preferred alternative and the proposed mitigations. The public can comment on the draft EIR and those comments and EBMUD responses would be included in the final EIR.

The Chabot Dam Upgrade Draft Environmental Impact Report (EIR) will be released for public review in late 2013, and a public hearing will be held during the 45-day review period. Written comments on the draft EIR will be addressed in the final EIR. The EBMUD Board of Directors will formally certify the final EIR and approve the project in spring 2014. The California State Department of Water Resources Division of Safety of Dams (DSOD) will also need to approve the project.

The EIR is being prepared by staff and consultants, and will identify two dam alternatives: soil treatment (cement deep soil mixing) and conventional earthwork. After the EIR is complete, EBMUD staff will recommend a preferred alternative based on costs, environmental impacts, and public and resource agency comments.

Twelve environmental issues will be analyzed in the Chabot Dam EIR: aesthetics/visual quality, biological resources, air quality, greenhouse gas emissions, public services (parks), hazards and hazardous materials, hydrology and water quality, cultural resources, geology and soils, transportation and traffic, recreation, and noise and vibration. The EIR analysis will identify potential impacts resulting from the project for each environmental issue, and propose mitigation measures that either avoid, reduce or eliminate the significance of the impact. The Draft EIR will be released for public review in late 2013, and a public meeting will be held during the 45-day review period. Written comments on the Draft EIR will be addressed in the Final EIR which will be presented for Board action in spring 2014.

Reservoir Operation and Water Use

Chabot Reservoir water is stored for emergency supply, recreational use, maintenance of flows downstream, and to provide irrigation water for two golf courses. The emergency supply could be used for drinking and/or for fire suppression. Water from Chabot Reservoir has been used for fire suppression on multiple occasions, and at least once in the last ten years. San Leandro Creek, downstream of Chabot Dam, runs through a heavily urbanized area, has been channelized for flood control, and there are man-made weirs and other structures on the creek. Releasing additional water for fish downstream is not likely to improve fishery conditions unless additional downstream improvements are made to restore the creek to a natural state. Any additional releases will reduce storage for other needs.

The long-term planned use for the Chabot Dam is the same as the current use. Lake Chabot Reservoir provides emergency standby water supply and it supplies raw water to Lake Chabot Golf Course and Willow Park Golf Course. The facility is used extensively for recreation: the East Bay Regional Parks District (EBRPD) leases EBMUD property to operate Lake Chabot Regional Park and Anthony Chabot Regional Park, and the City of San Leandro leases EBMUD property to operate Chabot Park. The retrofits to the dam and the outlet tower will be addressed by this project.

Outlet Works

The pavilion was added to the tower by a private water company 40 years after the tower was constructed. Public access is not allowed due to public safety and water quality concerns. The estimated cost to retrofit the pavilion to comply with seismic safety standards is substantial. Additional expenses would have to be incurred to maintain the structure. One commonly utilized alternative is to install commemorative plaques that document the pavilion, consistent with the placards installed by EBRPD for other previously-removed historical features at the site.

No, the work would not impact the spillway function.

Work at the tower would need to be completed before work at the dam begins in the spring of 2016. Work at the tower could begin as early as the fall of 2015.

Construction Impacts (Earth Movement/Hauling/Ground Improvement)

Excavation at the dam is expected to begin in the spring of 2016; fill and compaction at the dam is expected to end in the fall of 2016.

EBMUD generally surveys and documents the roadway's condition prior to work and repairs the paving to the pre-construction condition.

The conventional earthwork option would require excavating between 100,000 and 140,000 cubic years of soil. This approximates to enough volume to cover a football field 56 to 79 feet high.

Under the soil treatment option, 32,000 to 39,000 cubic yards of material (soil and solidified mixture of cement and soil) would be hauled and temporarily stockpiled. The soil treatment alternative would require the import of 8,100 to 10,800 tons of cement, which uses heavier cement trucks. Also, the soil treatment alternative would require excavation, which although smaller, would still need to be hauled and stockpiled.

The anticipated size is 10 to 20 CY trucks for earthwork.

The excavated soil would be stockpiled on site at the site of former filter ponds, at Chabot Park, or at a combination of both sites. Both sites are owned by EBMUD and the Chabot Park area is leased to the City of San Leandro that operates the Chabot Park.

Offsite stockpiles, including the Quarry and Covington sites, are no longer under consideration.

Yes it is. The bridge was upgraded in the 1980s during the dam spillway construction work.

Pedestrian access/safety would be addressed as part of a traffic study in the EIR. If required, flaggers can be used to direct traffic at problematic intersections.

The hours of construction have not been determined, and this is something that is typically addressed in the EIR during the CEQA process. For a recent comparable project (2008 though 2010) EBMUD constructed seismic upgrades at San Pablo Dam using the CDSM construction approach. The working hours for that project were from 7:00 a.m. to 7:00 p.m., Monday through Friday for all work except the soil treatment. These are typical construction hours allowed by cities. CDSM soil treatment work also occurred through the night.

The cost of these alternatives will be estimated concurrent with the preparation of the EIR and will be one of the factors used to evaluate possible alternatives.

Dam Stability

EBMUD has a comprehensive dam safety program. Chabot Dam has been studied extensively and there is no life-safety hazard associated with the dam. The latest seismic stability report is available at the project website.

Dam surveillance instruments (piezometers, drains, survey markers) are installed at the dam. EBMUD inspects the dam and monitors the dam safety instrumentation periodically: drains are continuously monitored and are inspected bi-monthly, piezometers are monitored and inspected monthly, and surveys are performed bi-annually. The instrumentation and survey data are also received by DSOD.

The stability evaluation and the design for the upgrade are based on the maximum credible earthquake (MCE) on the Hayward Fault, which has a moment magnitude of 7.25. As a comparison, the 1989 Loma Prieta earthquake had a moment magnitude of 6.9. Monitoring data before and after the Loma Prieta earthquake had an estimated moment magnitude of 8.0. No evidence of instability or apparent damage was reported after the 1906 San Francisco earthquake. The Hayward Fault earthquake in 1868 had an estimated moment magnitude of 6.8, and it occurred before the construction of Chabot Dam. It is important to note that the recent earthquakes have been on different faults, and represent lower levels of seismic risk. T this time, EBMUD is completing the seismic upgrade of Chabot dam based on the MCE on the Hayward Fault which represents the most severe earthquake forces among the Bay Area faults at the dam site.

For the conventional earthwork option, dewatering wells will pump down the water table in the dam before soil excavation begins. This will relieve pressure caused by the groundwater. By pumping down the water table, the soil at the excavation will have increased strength to keep the dam safe during construction. For the soil treatment option, the dam will remain safe during construction without any additional measures.

Inundation maps are required by the State of all dams for municipal emergency planning purposes only and are not indicative of the safety and stability of the dam. Again, the dam is safe and is not expected to fail in the maximum credible earthquake.

Recreation and Chabot Park

Portions of the loop trail will need to be closed near the dam to accommodate the construction.

Yes, it will be necessary to close Chabot Park during construction because of the heavy equipment moving through the park. The day camp will have to be relocated, as it was when EBMUD last upgraded in 1980. EBMUD staff will work with the City and EBRPD to identify location and recreation alternatives in the area, as done for the 1980 upgrade.

San Leandro Creek

EBMUD plans to use best construction practices in the industry to prevent the migration of silt into the pumped water. In the event that silt is present in the pumped water, that water would be held in tanks to allow the silt to settle out before the water is returned to San Leandro Creek.

The proposed project has no impact on planned releases from Chabot Reservoir; releases will be maintained as they have been in recent years. A review of those releases is just being initiated by EBMUD in conjunction with stakeholders and that effort might lead to a changed release schedule in the future.

There is no record of a man-made fishery of San Leandro Creek. However, there are three distinct fisheries on San Leandro Reservoir (USL) and Chabot Reservoir, and one above USL. The origin of the fish in either side of Chabot Dam is unknown. The fishery above USL consists of protected genetically pure native steelhead. Existing reservoir releases maintain the creek in the channel for several thousand feet downstream and keep the fish in good condition.

Because there are no planned changes to the current stream flows during or after dam construction, mitigation associated with steelhead habitat would not be part of this project.

The National Oceanic and Atmospheric Administration (NOAA) Fisheries is preparing a study on central California coast steelhead, and EBMUD has had workshops with NOAA Fisheries on the subject. It should be noted that San Leandro Creek runs through a heavily urbanized area, that soils within the creek contain toxins from local urban runoff, and that the creek has been channelized for flood control, which causes flashier runoff. These factors severely compromise creek conditions for fishery.

The outlet would not be operable during the retrofit of the tower and outlet. Stream flows would be maintained by other means, such as pumping water over the spillway through temporary pipes from the reservoir.


Some trees will need to be removed. The number will be determined by the alternative that is selected. The number and location of the trees will be reviewed as part of the EIR in the CEQA process. The tree removal will be mitigated, per the requirements of CEQA.

Yes, EBMUD is aware of the eagle nest location. Potential impacts will be evaluated as part of the EIR.