River Road Over Gill Creek Bridge Replacement (Lake or Streambed Alteration Agreement No. EPIMS-SON-33058-R3)
3 Documents in Project
Summary
SCH Number
2022060354
Lead Agency
Sonoma County
Document Title
River Road Over Gill Creek Bridge Replacement (Lake or Streambed Alteration Agreement No. EPIMS-SON-33058-R3)
Document Type
NOD - Notice of Determination
Received
Posted
6/26/2024
Document Description
The project is limited to removal of the existing 40-foot-long and 23-foot-wide bridge that is constricting the Gill
Creek channel and replacement with a new free-span bridge measuring 112-feet-long and 36-feet-wide to alleviate
channel constriction. New bridge abutments will be located at the top of bank and the new bridge will pass the 100-
year storm flow with four feet of freeboard. The new bridge will cause approximately 4,000 square feet of
permanent impacts including rock slope protection that will be placed underneath the bridge, which will not be
interplanted because plantings would not survive due to lack of sunlight.
A temporary detour consisting of a gravel road through the dry streambed, will be constructed just downstream of
the existing bridge before the bridge is removed, to allow continued public access for residents living on River
Road. An existing concrete weir associated with the current bridge and located downstream of it will also be
removed as part of this project to improve fish passage and prevent scour. The weir will be removed prior to
construction of the detour road. As part of the detour road construction, a temporary 50-foot-long, 18-inch-diameter
corrugated metal pipe culvert will be placed in the dry stream channel before the detour road is constructed in case
of summer rain events.
Prior to removal of the existing bridge, a temporary gravel work pad will be constructed below the existing bridge
and in the footprint of the new bridge. The temporary work pad will allow access for equipment to demolish the
existing bridge and to capture debris as the bridge is removed. Once the temporary work pad is installed, the
existing bridge and associated wingwalls, measuring in total 1,200 square feet, will be demolished and debris
hauled away to proper disposal sites. With the existing bridge demolished, approximately 12,000 square feet (0.27
acres) of the channel will be graded to remove approximately 1,920 cubic yards of accumulated sediment to
accommodate the new wider bridge and allow the channel to migrate more naturally. This area of grading and
temporary impacts will contain the temporary detour road, the weir to be removed, the temporary culvert, and the
temporary work pad. The banks of the channel will be graded at a 2:1 slope and approximately 10,500 square feet
(0.24 acres) of rock slope protection will be placed and interplanted with native willow stakes. A portion of this rock
slope protection will be placed at the confluence of an unnamed tributary to Gill Creek to prevent erosion on thenorthwest portion of the new bridge.
Once earthwork is completed, the new bridge will be constructed onsite. Concrete foundations for the new bridge
will be poured into formwork to prevent it from entering the creek channel. While some construction equipment may
be working from the existing temporary gravel work pad, all concrete pumps will be staged outside of the channel.
Once the foundation has set, the abutments and wing walls will be placed. The location of the abutments and
wingwalls will be within the existing roadway, as the new bridge is longer than the existing bridge. The bridge
superstructure will be constructed on-site with the use of cranes to lift materials into place. The bridge deck will be
made of concrete and poured once the girders are in place. A debris tarp will be hung from the new bridge
superstructure to prevent debris from entering the creek channel. This project will result in permanent impacts to
riparian and open channel habitat of 2,800 square feet, with an additional permanent impact of 10,500 square feet
(0.24 acres) from interplanted rock slope protection. The project will also result in temporary impacts of 12,000
square feet (0.27 acres) to channel habitat and ruderal grasses along the road shoulder. As part of this project, nine
riparian trees will be removed. Access and staging will also occur in existing roads and pullouts.
Contact Information
Name
James Hansen
Agency Name
CDFW
Job Title
Environmental Scientist
Contact Types
Responsible Agency
Phone
Location
Cities
Unincorporated area
Counties
Sonoma
Regions
Northern California, San Francisco Bay Area
Other Location Info
The project is located at Gill Creek and an unnamed tributary to Gill Creek, in
an unincorporated area of the County of Sonoma, State of California; Latitude 38.735428°, Longitude -
122.916037°; on River Road where it crosses over Gill creek, approximately 850 feet northwest of the intersection
of River Road and Fox Ridge Road.
Notice of Determination
Approving Agency
CDFW
Approving Agency Role
Responsible Agency
Approved On
County Clerk
Sonoma
Final Environmental Document Available at
2825 Cordelia Road, Suite 100
Fairfield, CA 94534
Determinations
(1) The project will have a significant impact on the environment
No
(2a) An Environmental Impact Report was prepared for this project pursuant to the provisions of CEQA
No
(2b) A Mitigated or a Negative Declaration was prepared for this project pursuant to the provisions of CEQA
Yes
(2c) An other document type was prepared for this project pursuant to the provisions of CEQA
No
(3) Mitigated measures were made a condition of the approval of the project
Yes
(4) A mitigation reporting or monitoring plan was adopted for this project
No
(5) A Statement of Overriding Considerations was adopted for this project
No
(6) Findings were made pursuant to the provisions of CEQA
No
Attachments
Notice of Determination
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