San Leandro Marina Alts Study_Final

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SECTION 2 Alternatives Considered This section describes the three alternatives that are being analyzed for the San Leandro Marina Harbor Basin, as well as a No Action Alternative. 2.1 No Action Alternative (Custodial Care Only) If the City were to suspend the required periodic dredging of the Harbor Basin and Channel due to lack of funding or for some other reason, over time, the basin would fill with sediments through natural deposition. Within 4 to 5 years, Channel deposition would prevent access to the basin for the typical boats that presently use the marina. Kayaks and other hand launched craft could continue using the basin at high tides for another 4 to 5 years, at the end of which it would become difficult and unadvisable to continue. The harbor would very likely become a mud flat, and will eventually acquire salt marsh emergent vegetation over time starting at the periphery of the basin. A complex assemblage of plants and associated wildlife could exist in the harbor basin in the long- term, although Section 4.3 makes the argument that the mud flats could persist indefinitely. If the site evolved more conventionally, California cordgrass would occur closest to the water and common pickleweed at higher elevation, interspersed with salt grass, fleshy jaumea and alkali heath. Higher marsh elevations would support species such as arrowgrass, sea lavender, and marsh plaintain. Put another way, it would resemble the restored San Leandro Shoreline Marshlands to the south, with its wildlife community including resident and transient ducks, herons, egrets, geese, rails, wading birds such as avocets, sandpipers, gulls, terns, raptors, small mammals and upland bird species. It is also noted that, in the event that no funding is available for the removal of the existing piers and other structures in the Harbor Basin, they would eventually rot and the area would likely need to be fenced off for safety reasons. In this case, the site could eventually become blighted. Design concept for the No Action Alternative is illustrated in Figure 2-1, on the following page. 2.2 Alternatives Descriptions To varying degrees, all alternatives would contain wildlife high -marsh refugia, islands, high marshl, and low marsh areas. These wetland features would be created using the materials dredged from the basin during the next one or two dredge cycles. These wetlands would provide The terms high -marsh, refugia, and island are used interchangeably in this report. They are areas at or near high tide elevations and provide different, and usually more diverse, vegetation and habitat for additional species, especially those, such as the salt marsh harvest mouse, that seek higher ground during incoming tides. The detailed design of a selected alternative would determine the final elevations. San Leandro Marina Harbor Basin 2-1 ESA / 210461 Alternatives Study March 2011