HomeMy WebLinkAboutDOE3_PN_Project_Narrative_TRIP_SSDP_171128_v1.pdf
Project Name:
I-405, Tukwila to Renton Improvement Project, Stage 3
Size and Location of Site:
The existing I-405 bridge over the Cedar River in the City of Renton will be replaced with a single span
bridge, and the west side of the southbound lanes of I-405 north side of SR 169 widened. Total riparian
impacts on either side of the river will amount to 6,000 square feet.
Bridge Location: Latitude: 47°28'50.91"N, Longitude: 122°11'59.29"W
Land Use Permits Required for Proposed Project:
Master Land Use Permit, Critical Areas Permit for Aquifer Protection
Zoning Designation of the Site and Adjacent Properties:
Northwest – Commercial arterial
Southwest – Commercial downtown
Northeast – Commercial office residential
Southeast – Resource conservation
Note that WSDOT has authority to design and construct state highways within WSDOT ROW. WSDOT
design manuals address steep slopes and seismic hazards, and WSDOT’s design will comply with the
substantive requirements of the City of Renton’s critical areas ordinance.
Current use of the site and any existing improvements:
The proposed work area is part of a complex of multiple transportation crossings that include the
Houser Way bridge and a BNSF bridge to the west of the I-405 north and southbound lanes. Land use
and ownership adjacent to the I-405 corridor includes Renton Old City Hall on the south bank and
Liberty Park and Cedar River Park on the north bank.
Special site features (i.e., wetlands, water bodies, steep slopes:
The I-405 bridge crosses the Cedar River, an anadromous fish-bearing stream approximately 1.62 miles
upstream of its outlet into Lake Washington.
Statement addressing soil type and drainage conditions:
Soils in the vicinity of the bridge include alluvium composed of sand, silt, and clay deposited by the
Green River and sand and gravel with thin beds of silt and clay deposited by the Cedar River; Pilchuck
sandy loam in the low areas beyond the north bank; and Alderwood and Kitsap soils on very steep
slopes to the southeast. Pilchuck sandy loam is an excessively drained soil with high water transmittal
rates, and both Kitsap and Alderwood soils are moderately well-drained.
Proposed use of the property and scope of the proposed development:
The west side of the southbound I-405 bridge will be widened to accommodate additional lanes.
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For plats, indicate the proposed number, net density, and range of sizes (net lot area) of the new
lots:
Not applicable to this project.
Access:
From I-5 take I-405 to Exit 4, WA 169; take the first right from WA 169 south into Cedar River Park on
the northeast side of the bridge.
Proposed off-site improvements (i.e., installation of sidewalks, fire hydrants, sewer main, etc.):
Minor off-site improvements may include pavement markings, drainage improvements, permanent
signing, illumination, intelligent transportation systems and ramp metering, barriers, and tolling
gantries.
Total estimated construction cost and estimated fair market value of the proposed project:
I-405 bridge widening and relocation work is part of the larger I-405 Renton to Bellevue Express Toll
Lanes Project for which the total cost is estimated at $890 million. The Tukwila to Renton estimated
construction cost is $308 million.
Estimated quantities and type of materials involved if any fill or excavation is proposed:
The proposed plan does not require added fill materials within the Cedar River floodplain. Disturbed
areas are to be restored to the existing grade. There may be minor amounts of fill (approximately 100
cubic yards) in some locations associated with final grading.
Number, type, and size of any trees to be removed:
A registered landscape architect will prepare a tree inventory and restoration plan once the design
build contractor has been hired. Maps showing the location of proposed tree planting areas, and a list
of replacement species has been included in Attachment 5 – Tree Impacts and Restoration Plan.
Explanation of any land to be dedicated to the City:
Not applicable to this project.
Any proposed job shacks, sales trailers, and/or model homes:
Construction offices and staging areas will be within the WSDOT right-of-way to the extent possible.
Any proposed modifications being requested (include written justification):
None are being requested.
Distance from closest area of work to the ordinary high-water mark (for projects within 200 feet of
the Cedar River):
The closest bridge pier will be approximately 30 feet landward of the ordinary high-water mark on the
left (south) bank, and 80 feet on the right (north) bank.
Description of the nature of the existing shoreline:
Vegetation under the I-405 and other bridges is limited to shrubs, blackberry, and a few trees. River
banks downstream and on the south side of the upstream channel support mixed vegetation
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consisting of Douglas fir, big-leaf maple, red alder, black cottonwood, and blackberry. Upstream, the
north bank is stabilized by cement bulkheads along the shoreline of the Renton Community Center.
Work over and adjacent to the Cedar River will occur within the Shoreline High Intensity shoreline
designation.