The project is limited to the demolition and removal of the existing Crosby Herold Bridge over Doty Ravine and the construction and installation of a new replacement bridge. Demolition of the existing bridge will include clearing and grubbing, including tree removal, to accommodate the replacement bridge. The existing bridge abutments will be removed to a depth of approximately two feet below the channel bottom and the void backfilled with river rock. The adjacent banks will be recontoured and lined
with rock slope protection. The new bridge abutments will be located within the road prism behind the existing abutments (i.e. further away from the creek channel).
The new bridge will be a precast girder bridge and will be approximately 91 feet long and 36 feet wide with two 12-foot wide lanes and two four-foot wide shoulders. The bridge will sit on seat abutments founded on spread footings with wing walls at the south abutment and a combination of return wall and retaining walls at the north abutment. The road approaches will be widened to a pavement width of up to 32 feet. Roadside drainage will be captured in over side drains or inlets on the roadway approaches, directing the flow away from the bridge. New drainage ditches will be excavated along the roadway approaches where needed. Drainage
from the bridge deck will be discharged through a series of scuppers that will outfall directly into Doty Ravine. In order to keep road runoff within the right-of-way, the roadside ditch northeast of the bridge will be channeled into a pipe starting approximately 130 feet north of the bridge. An existing 12-inch corrugated metal pipe cross culvert that drains runoff from the roadway surface and offsite runoff from
the hillside to the east and an adjacent private parcel will be replaced with a single 42-inch reinforced concrete pipe culvert. Removal of the existing bridge and construction of the new bridge will require construction equipment to access the Doty Ravine creek bed and may require diversion of the creek. An open channel diversion will be used during construction to minimize impacts to fish. General bridge construction equipment expected to be used includes, but is not limited to: haul trucks, cranes, excavators, backhoes, dump delivery trucks, concrete trucks, concrete boom pump, and service vehicles. Project activities will remove a total of 33 native trees, 16 of which will be removed from riparian habitat.