Flood Control Zone 2
Zone 2 at a Glance:
Communities served: Portions of San Leandro and Hayward, Castro Valley, San Lorenzo, and the unincorporated Eden Townships of Cherryland, and Ashland
Area in acres: 40,390
Total miles of natural creek: 81
Total miles of earth channel: 5
Total miles of concrete channel: 12
Total miles of underground pipe: 44
Total miles of improved channel: 2
Creeks: Castro Valley Creek, Chabot Creek, Cull, Crow, Bolinas, Norris, Eden, Hollis, Palomares, San Lorenzo, and Sulphur
Drainage Canals: Ashland-Washington, Estudillo, and Bockman
Pump stations: Sulphur Creek and Roberts Landing
Reservoirs: Cull Canyon and Don Castro
Zone 2 Hydrology
Water flows down from Castro Valley and the Hayward hills to storm drains, channels, and pipelines leading to San Lorenzo Creek and on to San Francisco Bay. Sulphur Creek and the Estudillo and Bockman Canals also flow to San Francisco Bay.
At high tide, rain water is pumped into San Francisco Bay at Sulphur Creek and Roberts Landing Pump Stations. The Bay water level at high tide is higher than that in the creeks (sometimes by as much as eight feet) so pumps must physically lift the collected storm water so it can flow into the Bay.
Zone 2 Major Projects
Cull Canyon and Don Castro Reservoirs
Cull Canyon and Don Castro Reservoirs are maintained by the District for flood control and operated by the East Bay Regional Park District as recreational facilities.
A major issue for both Cull Canyon and Don Castro Reservoirs is siltation. Eroded silt—earth and debris—from upstream creeks continually fills in the reservoirs, thus reducing capacity to hold stormwater, jeopardizing water quality and impeding recreation. Cull Canyon Reservoir has over 400,000 cubic yards of silt—enough to fill nearly 2.7 million garbage cans!
Silt removal is extremely expensive and incurs environmental problems due to the vast quantities of silt extracted. Limited disposal areas near the reservoirs and high transportation costs to a final disposal site are also challenges.
Additionally, Cull Canyon Reservoir was the subject of an extensive seismic study, completed in 2006, that concluded the dam is seismically unstable. To stabilize the structure, the District must drain the reservoir completely which will eliminate its recreational use.
The District is currently exploring options to deal with both siltation and seismic problems. In the meantime, the water level at the Cull Canyon Creek dam has been lowered to make it more stable.
Eroding creek banks at Cull Canyon deposited silt into the reservoir. Post-and-wire revetments, much like wire fences, were installed at the toe of the creek bank at eroding spot to prevent collapse of creek banks.
San Lorenzo Creek Restoration & Wetlands
The District’s Clean Water Program Division is now drawing on a Coastal Impact Assessment Program (CIAP) grant to develop a plan to restore wetlands at the mouth of San Lorenzo Creek. District staff hopes to improve the existing habitat for native flora and fauna, as well as maintain or enhance the creek’s flood control capability.
In 2006, the District obtained a hydraulics and hydrology report that engineers are reviewing to determine how best to improve the wetlands. Design of the project will proceed once the District identifies what kind of construction and mitigation will be required.
New and Ongoing Projects in Zone 2
- Line B Habitat Improvement along San Lorenzo Creek from Hazel Ave. to 2nd Street
- Castro Valley Creek Restoration
- Line B San Lorenzo Creek Trail (2nd Street to City Center Drive)
For more information about the history of projects undertaken in Zone 2, please view the District’s Annual Reports.