Wohler Road Bridge Over Russian River Seismic Retrofit (Lake or Streambed Alteration Agreement No. EPIMS-SON-35832-R3)

8 Documents in Project


SCH Number
Lead Agency
Sonoma County
Document Title
Wohler Road Bridge Over Russian River Seismic Retrofit (Lake or Streambed Alteration Agreement No. EPIMS-SON-35832-R3)
Document Type
NOD - Notice of Determination
Document Description
The project is limited to a seismic retrofit of the existing Wohler Road Bridge over the Russian River. Retrofit components include installing new cast-in-drilled-hole piles with permanent steel shell casings around the existing footings, enlarging the footing caps, installing new piles at the abutments, replacing the bridge bearing with seismic isolation bearings, retrofitting the pier caps, and replacing the bridge deck. Retrofit construction will require work within an existing unnamed tributary for piers 2 and 3, with the unnamed tributary being shifted slightly to the north to accommodate project components. Work will occur under dry conditions and the unnamed tributary will be restored prior to the contractor completing the project. Work around Piers 2, 3, and 5 will result in temporary impacts to riparian habitat of approximately 16,988 square feet (0.39 acres) and 130 linear feet of channel in the unnamed tributary resulting from expansion of the pier footing caps. The footings will be located below ground and will allow for revegetation on top. Potential in-water work within the main stem of the Russian River is necessary to access pier 4. If dry conditions exist and Pier 4 can be accessed without contacting the active flow, work on Pier 4 may begin on or after April 1 to avoid higher flows when the Mirabel inflatable dam is raised. If water is present and Pier 4 cannot be accessed without contacting the active flow, then work will not start until on or after July 1. Temporary access for Pier 4 will be achieved via construction of a temporary gravel work pad, which includes a temporary gravel causeway extending from the west bank of the Russian River to pier 4 and 50 feet beyond the pier to the east. The temporary access causeway will measure approximately 150 feet long and 30 feet wide, and the temporary work pad will measure approximately 90 feet long and 60 feet wide. Both the work pad and causeway will be left to naturally disperse downstream during the winter after construction. Temporary access to pier 4 will leave the eastern portion of the Russian River unobstructed allowing for fish passage. Depending on the timing of when the Mirabel inflatable dam is raised, it may be possible to place the gravel work pad within the existing gravel bar when the channel is dry, and then the area would backwater once the dam is raised. Sheet piles will be installed directly into the temporary gravel work pad surrounding pier 4 using a vibratory hammer to prevent water that may seep through the gravel work pad from entering the work area around pier 4. Work on pier 4 will result in approximately 720 square feet of permanent impact to open channel habitat. As part of the project, there will also be clearing of approximately 5,400 square feet of riparian vegetation in an area that is within the Pacific Gas and Electric (PG&E) right of way, which will result in a permanent impact to riparian habitat. The project will not require dewatering. In total, the project will result in permanent impacts of 6,120 square feet (0.14 acres) to riparian and open channel habitat. The project will also result in temporary impacts of 16,988 square feet (0.39 acres) to riparian habitat. Approximately 30 trees will be removed as part of this project. Staging will occur within existing roads and developed or disturbed areas.

Contact Information

James Hansen
Agency Name
Job Title
Environmental Scientist
Contact Types
Responsible Agency


Northern California, San Francisco Bay Area
Other Location Info
The project is located at the Russian River and an unnamed tributary, in an unincorporated area of the County of Sonoma, State of California; Latitude 38.507446°, Longitude -122.883482°; 9703 Wohler Road, Healdsburg, CA 95448.

Notice of Determination

Approving Agency
Approving Agency Role
Responsible Agency
Approved On
County Clerk
Final Environmental Document Available at
2825 Cordelia Road, Suite 100 Fairfield, CA 94534


(1) The project will have a significant impact on the environment
(2a) An Environmental Impact Report was prepared for this project pursuant to the provisions of CEQA
(2b) A Mitigated or a Negative Declaration was prepared for this project pursuant to the provisions of CEQA
(2c) An other document type was prepared for this project pursuant to the provisions of CEQA
(3) Mitigated measures were made a condition of the approval of the project
(4) A mitigation reporting or monitoring plan was adopted for this project
(5) A Statement of Overriding Considerations was adopted for this project
(6) Findings were made pursuant to the provisions of CEQA


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