Environmental Declaration WPCP 20240409

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LC A $AN LEANDRO TREATMENT WETLAND PROJECT J A $AN LEA N D ROB ALAMEDA COUNTY, CALIFORNIA BIOLOGICAL ASSESSMENT APRIL 2020 4.0 EFFECTS OF THE PROPOSED PROJECT ON FEDERALLY LISTED FISH This section identifies potential temporary adverse effects of the proposed project on the two federally listed fish species and EFH during work related to the replacement or modification of the outfall. The existing outfall along the bank of the tidal slough may be replaced, repaired, or modified. If possible, work will occur during low tide when water and fish are not present at the outfall. If work needs to be completed during a higher tide, a temporary cofferdam or similar structure will be installed to prevent sediment from entering the slough and prevent fish from accessing the work area. No permanent effects from the proposed project are anticipated with the implementation of avoidance and minimization measures described in Section 2.2. 4.1 TEMPORARY EFFECTS FROM REPLACEMENT OR MODIFICATIONS OF OUTFALL 4.1.1 Turbidity and Increased Sedimentation The proposed project alternative is to conduct all in -water work during low tides, but if in -water work cannot take place solely during high tides, a cofferdam will be used. The proposed project is expected to create temporary increases in turbidity in the adjacent water column within the slough from increased sedimentation around the outfall. Short-term, localized turbidity effects on anadromous salmonids may potentially interfere with visual foraging, increase susceptibility to predation, and interfere with migratory behavior. Green sturgeon may be affected but are likely less susceptible to turbidity effects than the other federally listed fish species in this BA because they forage on bottom sediments (NMFS 2020b). Minor and localized elevated levels of turbidity from outfall work will be temporary and are not expected to result in harm, injury, or behavioral responses that impair migration or make federally listed fish species more susceptible to predation. If a cofferdam is not needed, a temporary silt fence will be installed during any maintenance activities that are likely to result in the disturbance of sediment within the existing outfall. This temporary fence will be installed and removed during the low tide. 4.1.2 Contaminants The current level of environmental contaminants in the slough within the Action Area is unknown, but the suspension of sediments associated with removal, modification, and/or replacement of the outfall may temporarily increase contaminant levels in the water column. However, such minor and localized elevations in contaminants should be quickly diluted to levels that are unlikely to adversely affect federally listed fish. 4.1.3 Toxic Chemicals Equipment refueling, fluid leakage, equipment maintenance, and construction activities in the slough pose some risk of contamination of aquatic habitat and subsequent injury or death to federally listed fish species. However, due to general construction environmental protection measures identified in Section 2.2.1, risk of aquatic habitat contamination is expected to be minimal and adverse effects on federally listed fish species are not expected. 24 P:\TER2001\BA\San Leandro Treatment Plant BA 4-7-20.docx (04/07/20)