As part of the LTMS, BCDC conducted studies on the potential of beneficial reuse as a viable alternative to in-Bay disposal. The beneficial reuse studies focused on ways to use dredged material as a resource, rather than disposing of it as a waste, thus avoiding many of the problems associated with in-Bay disposal. The three types of projects that the LTMS studies identified as most appropriate for the Bay are habitat restoration, rehandling facilities, and levee maintenance.
The LTMS studies evaluated approximately 100 sites around the Bay and in the Delta for a variety of beneficial reuse projects and found many that have high potential: nine sites with potential for habitat restoration areas using dredged material; eight sites for potential rehandling facilities where dredged material could be stored permanently, if necessary, or dried for construction or landfill use; three landfills where dredged material could be reused; and three Delta Islands where material could be used for levee restoration. Cumulatively, these sites could provide a significant percentage of the capacity needed for disposal of Bay dredged material and thus diversify disposal options.
Wetland restoration projects usually involve restoration of wetlands in the diked baylands, areas that have been diked from the Bay and are subsided below elevations suitable for the establishment of tidal wetland habitat. Dredged material can be used to raise existing elevations to allow wetland vegetation to establish thereby accelerating the restoration process. Dredged material can also be used to create elevated areas at sites that will be inundated only during maximum high tides or above the reach of the tides. These tidal pannes and seasonal wetlands provide habitat diversity and reestablish a more natural shoreline that can better adapt to sea level rise and other natural processes. Dredged material can also be used to enhance managed wetlands or for other habitat purposes. In the Bay Area, dredged material has been used to restore tidal wetlands at Muzzi Marsh in Marin County, Faber Tract in Santa Clara County, and Salt Pond No. 3 in Alameda County. In 1995, over two mcy of dredged material from the Port of Oakland’s 42-foot deepening project were used to restore tidal wetlands at the Sonoma Land Trust’s and Coastal Conservancy’s Sonoma Baylands restoration site at the mouth of the Petaluma River in Sonoma County. However, diked baylands can also provide existing valuable habitat functions, including seasonal wetlands and resting and roosting areas for shorebirds and migratory waterfowl. The LTMS studies concluded that restoration and other projects need to take into account existing habitat values as part of project planning.
Rehandling Facilities and End Uses
Rehandling facilities are typically areas along the shoreline where dredged material can be readily off-loaded, and subsequently dried and transported off-site for use as construction material or landfill cover. Dredged material use at landfills has significant potential since these sites: (1) need large volumes of cover and capping material, and some landfills have insufficient on-site sources; (2) have limited natural resource value; and (3) are designed to contain contaminants and manage runoff. However, landfills cannot accept material unless it has first been dried. While demonstrating the feasibility of rehandling, existing Bay rehandling facilities are either temporary (e.g., Port of Oakland’s Berth 10 facility) or limited to processing relatively small volumes (e.g., Port Sonoma Marina) or material from a specific sources (e.g., San Leandro Marina), thereby limiting the volume of material that can be used in landfills. The LTMS engineering analyses identified that rehandling facilities require deep-water access for barges at all tidal stages, access to utilities, and adequate landside areas in order to be economically viable.
The reclaimed islands and other low‑lying areas of the Sacramento and San Joaquin River Delta region are surrounded by an 1,100-mile levee system which protects infrastructure, environmentally sensitive habitat, and, by preventing salinity intrusion, the drinking water supply for much of the state. The Delta levees consist mainly of peat material taken from adjacent channels and sloughs. The high organic matter content of these materials together with inadequate maintenance and construction standards have resulted in decomposition, subsidence and instability of many of the Delta levees.
The state Delta Flood Protection Act of 1988 directed the California Department of Water Resources (DWR) to develop and implement flood protection for the eight western Delta islands. In 1994, the Federal Emergency Management Agency (FEMA) determined that 39 reclamation districts in the Primary Flood Control Zone of the Delta did not fully comply with the state’s Flood Hazard Mitigation Plan, which outlines levee rehabilitation standards. The DWR, the Corps, and local reclamation districts have use Bay dredged material to upgrade Delta levees at Twitchell and Jersey Islands, and, most recently, at Winter Island using material from the Corps maintenance project at Suisun Channel. However, concerns about the potential impacts of saline material on a freshwater environment may limit use of Bay dredged material in the Delta.