Dry Creek Road Bridge Replacement (Lake or Streambed Alteration Agreement No. EPIMS-NAP- 30649-R3)

Dry Creek Road Bridge Replacement (Lake or Streambed Alteration Agreement No. EPIMS-NAP- 30649-R3)

The Project is limited to replacement of an existing bridge structure, which is structurally deficient. The existing bridge and roadway approaches will be removed and a new bridge will be constructed along a roughly east-west alignment, approximately 150 south of the existing bridge. The approach to and from the bridge will be widened from 22 feet to 28 feet and the west approach will consist of a 15-foot-high embankment. The new structure will be a free span precast-prestressed concrete wide flange girder bridge that will be approximately 32 feet wide and approximately 81 feet long, with two 11-foot wide lanes and 3-foot wide shoulders on each side. The bridge structure will consist of four precast wide flange girders and a cast-in-place concrete deck. The deck will be placed on stay-in-place metal corrugated deck forms. Falsework (i.e., temporary support structures) within the creek shall not be used to construct the bridge deck. Concrete barriers with bicycle railing will be installed on each side of the bridge deck. One abutment will be a short seat abutment and the other will be a high cantilever abutment. Both abutments will be supported with 24-inch cast-in-drilled-hole piles and above the 100-year water surface elevation, but within top of bank, and will include wingwalls. Rock slope protection will be placed along abutments and extend between 25 feet and 45 feet up and downstream of the bridge deck. The existing bridge, wingwalls, western abutment, and part of the eastern abutment, will be removed and the bank slopes restored and planted with native vegetation. This will include installation of vegetative soil lifts and a root wad system on the south side of the stream banks where the abutment will be removed. The Project will also install a new stormwater bioretention basin and stormwater outfalls, which will include placement of rock slope protection. The Project will require dewatering of the channel. One stream diversion will be required to install the new bridge, and another stream diversion will be required for demolition of the existing bridge and bank stabilization and restoration. The equipment staging area will be northwest of Dry Creek Road, just south of Dry Creek, approximately 100 feet outside of the ordinary high-water mark and beyond top of bank. The channel will be accessed from the banks and within the Project footprint. The Project will result in 0.13 acres and 215 linear feet of permanent impacts to stream and riparian habitat from the storm drain outfall structures, bridge abutment footings, and shading from bridge deck. The Project will result in temporary impacts to: 1) 0.35 acres and 345 linear feet of riparian habitat from removal of existing bridge abutments and replacement with biotechnical bank stabilization including planted rock slope protection at the toe of the slope, as well as from access and staging, and 2) 0.21 acres and 500 linear feet of aquatic habitat from two stream diversions and dewatering the channel. Approximately 25 native trees within the riparian corridor will be removed.

Unincorporated area

Napa

Northern California, San Francisco Bay Area

Napa