King - West Snoqualmie Valley Road NE Culvert Replacement
Project Number: 1619
From milepost 8.22 to milepost 8.24
RATA Funds: $882,000
Legislative District: 45
Status:
Date Approved: 2013
At the project location, West Snoqualmie Valley Rd NE is classified as a rural major collector road that is generally aligned in a north-south direction running along the west side of the Snoqualmie river and connecting NE Woodinville Duvall Rd to NE 124th St. At the project site, West Snoqualmie Valley Rd NE is a 2-lane paved collector, with 11-foot average width lanes and narrow gravel outer road shoulders. Existing guardrail runs along the east shoulder north of the existing culvert from a flared terminus and continuing north beyond the project limits. The driveway #13523 meets the west edge of W Snoqualmie Valley Rd NE at the south end of the project limits and extends into private property (parcel 232303-9012) at a 12% to 20% slope. An existing stream runs west to east through private property (parcel 232303-9012) and through conveyance systems down an embankment at the east perimeter of the parcel. Once the stream is within right-of-way, it crosses via an existing cross culvert under the West Snoqualmie Road NE and continues eastward, meandering through private property (parcel 232606-9010) until eventually reaching the Snoqualmie River.
The existing pipe has proven to lack adequate hydraulic capacity in larger flow events, with headwater elevations often reaching the roadway edge of asphalt. This creates potential for roadway flooding hazards and future degradation to road condition due to possible erosion/scouring. Overtime the high-capacity flows have deposited sediment throughout the existing pipe with most buildup occurring at the outlet (nearly 75-80% full). The western embankment is prone to slides which tend to plug the pipe inlet at expedite flooding. Road closures force long detour routes and increase ADT on rural minor roads. Though some hydraulic capacity could be restored by performing maintenance on the existing pipe, this will only delay a chronic capacity issue which may eventually cause failure of the structure or roadway.
The project replaced the existing 18” concrete cross culvert identified in 2008 as part of a Vulnerable Road Segment Report prepared for King County. The replacement is a 46 feet long x 12 feet wide x 5’ high concrete box culvert at 1.7% slope and 30° skew the concrete box culvert. Since the project built, roadway is prevented from failure/degradation due to flooding hazards.
The existing pipe has proven to lack adequate hydraulic capacity in larger flow events, with headwater elevations often reaching the roadway edge of asphalt. This creates potential for roadway flooding hazards and future degradation to road condition due to possible erosion/scouring. Overtime the high-capacity flows have deposited sediment throughout the existing pipe with most buildup occurring at the outlet (nearly 75-80% full). The western embankment is prone to slides which tend to plug the pipe inlet at expedite flooding. Road closures force long detour routes and increase ADT on rural minor roads. Though some hydraulic capacity could be restored by performing maintenance on the existing pipe, this will only delay a chronic capacity issue which may eventually cause failure of the structure or roadway.
The project replaced the existing 18” concrete cross culvert identified in 2008 as part of a Vulnerable Road Segment Report prepared for King County. The replacement is a 46 feet long x 12 feet wide x 5’ high concrete box culvert at 1.7% slope and 30° skew the concrete box culvert. Since the project built, roadway is prevented from failure/degradation due to flooding hazards.