Environmental Impact Statement - Sonoma Land Trust

California Department of Fish and Game
U.S. Fish and Wildlife Service
Chapter 2. Alternatives
Internal Features
Implementing this alternative would provide a rare opportunity to restore a
historic gradient between tidal marsh, alluvial fan communities, and upland
grassland/riparian habitats. The overall design of this alternative would
incorporate the same internal features described above for the Project and would
appear as shown in Figure 2-12.However, unlike the Project, in which the
proposed pilot channels consist of multiple trunk channels extending from
various breaches in the outboard levee, thisThis alternative would require that
only a single trunk channel be extended from Breach 1 to the area north of the
rail line. The trunk channel would pass through one of the potential
bridge/culvert options. This channel would in turn compose part of an intricate
channel network consistent with what was described for the Project.
Excavation of pilot channels south of the rail line would be the same as for the
Project. Excavation for the approximately 19,000 linear feet of pilot channels
north of the SMART rail line would require removal of approximately 18,800
feet of material with a volume of 137,000 CY of material. The combined pilot
channel excavation north and south of the SMART rail line would be
approximately 72,100000 feet in length, and would require excavation of
586,approximately 1,337,000 CY of material. Ditch blocks would be constructed
in several drainage channels located north of the rail line. They would be
constructed in the same manner as for the Project. An estimated 500 CY of
material would be used to construct ditch blocks north of the rail line.
Additionally, a seriesthe same types of interior graded topographic features—
including marsh mounds, sidecast ridges, counter-leveeand sidecast mounds, and
gently sloping habitat levee edges—would also be included in project design and
would help dissipate wind and wave erosion. These features would be designed
and constructed similar to that described for the Project. These internal features
would include up to 650 marsh mounds, 65 side cast ridges and 325 and sidecast
mounds.
Stormwater Conveyance Modifications
As for the project, storm water flows from the north side of Highway 37 would
need to be discharged to the south side of the highway. Culvert 7 (C-7), which
drains watershed runoff under Highway 37 immediately west of the driveway to
the Dickson Ranch, would be modified to allow flows to gravity drain directly
into the restored tidal marsh. Modifications include raising the existing culvert to
keep the water above tide heights and adding a second culvert through the new
flood control levee alongside Highway 37.
Additionally, the riparian corridor leading downstream from culvert 10 (C-10)
would be extended south to its confluence with culvert 11 (C-11) to create both a
continuous stand of riparian vegetation along its entire length and an area of
freshwater marsh at its downstream end. As described for the Project, the
resulting patches of marsh and riparian woodland created by the these
Sears Point Wetland and Watershed Restoration
Project Final Environmental Impact
Report/Environmental Impact Statement
2-37
April 2012