Proposed Basin Plan Amendments to implement the Long Term Management Strategy for the Disposal of Dredged Material in the San Francisco Bay Region
June 13, 2001
Background and Existing Conditions
Disposal of dredged material at various sites within San Francisco Bay has been ongoing for at least 100 years and probably dates back to the gold rush era filling of the margins of the Bay surrounding San Francisco. Dredging in the past was used to provide fill material for the expansion of land around the Bay. Today, dredging is necessary to maintain the navigation channels, docks, and marinas in San Francisco Bay because of the deposition of sediments carried to the Bay by tributaries, especially the Sacramento-San Joaquin river system. The need is further exacerbated by the desire to deepen navigation channels and maritime facilities to accommodate increasingly large vessels. The trend to larger vessels has been accelerated in recent years for ports on the West Coast by the increase in trade with Pacific Rim countries. This has removed one of the barriers that had previously limited vessel size, the Panama Canal.
The most common practice for dredged material disposal for the past 20 years has been to place dredged material at in-Bay locations with the expectation that the material would be removed and redistributed by tides and currents. Since at least 1986, dispersive disposal has been limited to five designated disposal sites (Figure 1). Three of these sites, the Alcatraz, San Pablo, and Carquinez sites (SF-11, SF-10, and SF-9, respectively), are potentially available for use by any dredging project. The San Francisco Bar Channel disposal site (SF-8) is for exclusive use by the U.S. Army Corps of Engineers (USACE) for disposal of maintenance material from the San Francisco Bar Channel; similarly, the Suisun Bay site (SF-16) is reserved for material from USACE maintenance dredging of the Suisun Bay Channel and New York Slough federal channels.
As illustrated in Figure 2, the volume of dredged material disposed of at the designated in-Bay disposal sites since 1991 has averaged approximately 2.3 million cubic yards (mcy) per year. This is a reduction from disposal volumes in the 1970’s and 1980’s. Though the data from those decades is not of sufficient quality to provide accurate estimates of true disposal volumes, it is clear that the volume was more than 8 mcy in some years. The recent reduction in in-Bay disposal volumes is the result of a number of factors, including changes in commercial shipping patterns and competition between ports both in the Bay Area and with other West Coast ports. However, the primary factor in the reduction is the closure of military facilities that had previously required channel maintenance.
The major focus of recent concern about in-Bay disposal of dredged material has been the Alcatraz disposal site. The Alcatraz site has historically received the largest portion of the volume disposed. Figure 3 shows a reconstruction of the Alcatraz site prior to organized disposal activity. Figure 4 shows recent bathymetric data at the Alcatraz site, illustrating one of the reasons for concern about in-Bay disposal: the potential for disposal to impact the use of the Bay for navigation, a designated beneficial use. The mounding of material at Alcatraz was probably the result of several factors. The first was high disposal volume (more than 8 mcy annually) during the 1980’s. The second factor is earlier disposal practices that did not limit material type to dredged sediments. During this period, material other than Bay sediments, such as concrete rubble and construction debris, were placed at the Alcatraz disposal site. This practice may have limited dispersion or removal of material below an “armoring” layer of rubble and debris. These practices were eliminated in the late 1980’s and early 1990’s with actions by the Board and USACE to restrict the type and volume of material that could be placed at the Alcatraz site.
In addition to the potential for in-Bay disposal to impact the beneficial use of the Bay for navigation, there are additional concerns regarding the potential impacts of turbidity during dredging or disposal and possible impacts related to the mobilization of contaminants. The relationship of the proposed Basin Plan amendments to each of these potential impacts will be discussed in this report.
Concerns about the impacts of in-Bay disposal of dredged material led to the creation of the Long Term Management Strategy for the Disposal of Dredged Material in the San Francisco Bay Region (LTMS) program in 1990, by the USACE, the USEPA, the San Francisco Bay Conservation and Development Commission, the San Francisco Bay Regional Water Quality Control Board, and the State Water Resources Control Board, along with representatives from the dredging, fishing, environmental, and scientific communities. The LTMS was formed to resolve the Bay’s “mudlock,” a period in the late 1980’s when concern by regulatory agencies and environmental and sportsfishing groups about the effects of in-Bay disposal of dredged material were so high that the permitting of disposal projects came almost to a standstill. The LTMS hoped to accomplish this by diversifying disposal options and identifying feasible alternatives to dependence on the in-Bay disposal sites. The goals of the LTMS are:
Maintain in an economically and environmentally sound manner those channels necessary for navigation in San Francisco Bay and estuary, and eliminate unnecessary dredging activities in the Bay and estuary;
Conduct disposal of dredged material in the most environmentally sound manner;
Maintain a cooperative permitting framework for dredging and disposal applications.
The federal partners in the LTMS signed a Record of Decision (ROD) in July 1999, certifying (pursuant to the National Environmental Policy Act) a Policy Environmental Impact Statement/Programmatic Environmental Impact Report (LTMS EIS/EIR) describing potential alternative long-term strategies for accomplishing these program goals (the State Board certified the document pursuant to the California Environmental Quality Act in October, 1999). The selected alternative identified in the ROD was to decrease reliance on in-Bay disposal of dredged material and to increase reliance on disposal in the open ocean and on beneficial reuse of dredged material for uses such as wetland restoration and levee maintenance. The program’s long-term goal is to reduce the total volume of in-Bay disposal to approximately 1 mcy per year, with a less-ambitious regulatory maximum (target) of 1.25 mcy per year. The LTMS agencies held a series of public workshops to discuss how to implement this target, and using the feedback received, developed a Management Plan, detailing the mechanisms the agencies proposed for implementation of the LTMS. A draft Management Plan was circulated for public comment in 2000, and a final will be completed by the fall of 2001.