Environmental Impact Statement - Sonoma Land Trust

California Department of Fish and Game
U.S. Fish and Wildlife Service
Section 3.3. Water Quality
Full-Tidal Alternative
The Full-Tidal Alternative includes the construction of a box culvert/bridge for
the SMART rail, and flood protection levees along Reclamation Road and
Highway 37,. and an expanded trail system. This increase in construction
activities would increase the potential for turbidity impacts. However, as above,
most construction will occur prior to levee breaching. and turbidity and
sedimentation cwould increase in the short term until equilibrium is established
in the restored tidal marsh and tidal sloughs. This localized, short-term impact is
considered less than significant because high turbidity is characteristic of the
water in dynamic tidal marsh environments. No mitigation is required.
The potential impacts of dredging the pilot channels and levee breaches include
increased turbidity and suspended sediments comparable to the Project. With
implementation of Mitigation Measure WQ-MM-43, this impact is considered
less than significant.
Conclusion: Less than Significant with Mitigation.
Impact WQ-6: Degradation of Water Quality due to
Inundation of Formerly Drained Wetlands
Proposed Project
The proposed restoration site would be located on a formerly drained tidal
wetland. The site is therefore likely to contain acid-sulfate soils. Such conditions
could affect the water quality in the created tidal marsh because of resulting low
pH levels. However, because the proposed restoration site was diked and drained
in the 1890’s, it is likely that any sulfuric acid runoff resulting from the
formation of acid-sulfate soils would have occurred over time and would not be
exacerbated by the Project. In addition, sampling results from the adjacent Tolay
Creek restoration project (Takekawa et al. 2002) have indicated that pH readings
at the Project site would be expected to increase over time following breach of
the surrounding perimeter levee. Therefore, breaching of the levees and
restoration of the Sears Point site to natural tidal wetlands accretion processes are
not expected to generate substantial changes in San Pablo Bay water quality
associated with acid-sulfate soils. Water quality indicators, such as pH, are
expected to normalize over time as the wetlands restoration site matures, and
appropriate monitoring will be included in the project monitoring plan. This
impact is considered less than significant, and no mitigation is required.
Conclusion: Less than Significant.
Full-Tidal Alternative
Similar to the Project, breaching the levees and restoration of the Sears Point site
to natural tidal wetlands accretion processes are not expected to generate
Sears Point Wetland and Watershed Restoration
Project Final Environmental Impact
Report/Environmental Impact Statement
3.3-23
April 2012