Environmental Impact Statement - Sonoma Land Trust

Sonoma Land Trust
Chapter 4. Consultation and Other Requirements
However, forIn addition to potential turbidity and contaminant effects, the action
alternatives could also result in short-term reductions in dissolved oxygen (DO)
due to discharge of low DO water during implementation of Breach 1 (if standing
water remains as a result of pre-vegetation or seasonal precipitation), and/or
reductions in DO due to decay of submerged vegetation following restoration of
tidal action. As discussed in Section 3.3, tidal flushing would quickly restore DO
levels to ambient concentrations. This potential impact would be of short
duration, and would also be localized. Even if other restoration projects where
construction has not yet been completed are breached during the same time frame
as the Sears Point project, there would be no cumulative impacts. Compliance
with permit conditions and implementation of the water quality control measures
identified in Mitigation Measures WQ-MM-1, WQ-MM-2, WQ-MM-43, HAZ-
MM-1, and HAZ-MM-5 would adequately protect against degradation of water
and sediment quality due to release of construction-related pollutants and thus
hazards due to release of such hazardous materials levee breaching and potential
low DO conditions and thus avoid any considerable contribution to cumulative
water quality impacts during construction.
As discussed in Section 3.3, Water Quality, it is currently unknown whether the
effects of the restoration alternatives on methylmercury production would be
more notable than the natural methylation processes. It is generally thought that
restoring large areas of tidal marsh throughout the San Francisco Bay region
would be beneficial to the environment. However, large-scale restoration projects
could expose populations of special-status species to increased concentrations of
methylmercury, if new areas of tidal marsh added over a short period of time
actually resulted in an increase of mercury methylation over existing conditions.
Mitigation Measure WQ-MM-32 requires the implementation of a
methylmercury adaptive management plan based on consultation with the
relevant local, state, and federal agencies. The likely outcome of the adaptive
management plan would be informed decision making that would guide the
phased restoration of tidal marshes throughout the estuary. Depending on the
findings of the subsequent monitoring and other studiesy, it, further adaptive
management actions may be necessary to schedule the amount and timing of
restoration activity to reduce mercury methylation within water bodies adjacent
to multiple wetland restoration projects. However, because it currently remains
unknown whether wetland restoration would actually resultrequired in increased
mercury methylation,the long term, and an adaptive management approach is
appropriate. The contribution of either action alternative to potential cumulative
methyl mercury impacts can be reduced to a less than significant level with
implementation of Mitigation Measures WQ-MM-2.
Apart from With implementation of the methylmercury potential noted above,
the project is notmitigation measures outlined in Section 3.3 and 3.9 neither
action alternative is expected to result in a considerable contribution to a
significant cumulative water quality impact. The contribution of the project to
potential cumulative methyl mercury impacts can be reduced to a less than
considerable level with implementation of Mitigation Measures WQ-MM-3.
Sears Point Wetland and Watershed Restoration
Project Final Environmental Impact
Report/Environmental Impact Statement
4-12
April 2012