Environmental Impact Statement - Sonoma Land Trust

California Department of Fish and Game
U.S. Fish and Wildlife Service
Chapter 2. Alternatives
Creek Restoration Area. Breaches 3 and 4 would most likely be smaller than
Breaches 1 and 2, and would require less excavation. If Breaches 3 and/or 4 are
required, they would either be constructed once Caltrans has implemented
improvements to protect Highway 37 from flooding at the Upper Lagoon of
Tolay Creek (as a separate and independent project), or would require hardening
a small portion of Tolay Creek just south of the Upper Lagoon to mute the tidal
range reaching Highway 37. In the case of the latter, the narrowest point of the
channel south of the Upper Lagoon in Tolay Creek would be hardened using
riprap, gravel, cobble, articulated mats, or similar armoring. This would require
up to approximately 2,000 CY of material, placed along the side slopes and
bottom of Tolay Creek, and cover a footprint of up to approximately 30,000
square feet.
Constructing all four breaches and the connector channel (see below) could
require removing up to approximately 145,000 CY of material and disturbing a
total of up to approximately 8.7 acres of tidal marsh. Because these small
volumes of excavated materials would be highly saturated and would be difficult
to transport to other areas of the project site, they could be used to construct
Marsh Mounds or side cast inside the site adjacent to the breaches. The typical
equipment used for this work would be an excavator or a long reach excavator. If
material was hauled to other areas of the site for reuse off-road trucks would
likely be used.
Improving tidal exchange in Tolay Creek is no longer a component of the project,
therefore dredging and widening of Tolay Creek has been removed from this
project description.
Dredging
Dredging between the site and Tolay Creek would further enhance hydraulic
connections, allowing for eventual full unimpeded tidal flow in Tolay Creek.
Dredging would be accomplished with a hydraulic rotary cutter head suction
dredge. The dredged materials would be piped into the tidal wetlands area and
used to refill borrow pits or generally raise the interior grade. The dredging
process water would be held in a detention pond and returned to the Bay/Creek in
compliance with water quality permit conditions. In the event that the dredged
material was unneeded or unsuitable for on-site use, this dredging could be done
with a small clamshell dredge and the material could be barged to an open water
disposal area or other suitable reuse option.
Considering the local bathymetry and the size of the project, a 10- to 14-inch
hydraulic dredge would be used. The dredge would be diesel-powered and have
engines totaling about 700 horsepower (hp). A tender tug of about 300 hp and a
crew boat of about 150 hp would also be in use part of the time. On the land side
placement area, a small bulldozer or loader would be used to move the dredged material
pipeline as needed. Temporary drainage pump(s) of approximately 70 hp would
likely be required to return the process water to the Bay/Creek. These pumps
Sears Point Wetland and Watershed Restoration
Project Final Environmental Impact
Report/Environmental Impact Statement
2-11
April 2012