|The purpose of the project is two-fold: |
- replace the failing culvert at Neahkahnie Creek that has reached its useful life. and
- install left-turn improvements at Laneda Ave. and Manzanita Ave. as included in the City of Manzanita’s Transportation System Plan (TSP).
The project is currently under construction. A tunnel structure will replace the existing culvert and there will be enhance-ments to the stream bed. The project also includes realigning U.S. 101 near Manzanita with new turn lanes at Laneda andManzanita Avenues. The scheduled work includes installation of retaining walls with flaggers occasionally needed to control single lane traffic.
The project is scheduled to be completed in September 2017.
According to the ODOT maintenance inspection report dated Oct 14, 2008, there is distortion at the seam (bulge) in bottom on corrugated metal pipe (CMP), with a 5 foot section of the invert completely rusted through. Approximately 100 feet near the culvert midlength is "egg shaped". The culvert will be inspected every 24 months. Neahkahnie Creek is listed on the Oregon Department of Fish and Wildlife as the highest priority for fish passage due to excellent spawning habitat within the upper reaches of the existing lake. The existing culvert is 460 feet long, has a steep grade (causing high water velocities) and the outlet is perched above the stream channel. These conditions are barriers to juvenile fish in reaching critical habitat. The replacement culvert will be 270 feet long and 15 feet in diameter and will be located within the road prism. The remaining 400 feet of culvert will be replaced with a "natural" stream channel that will extend up to the outlet of Reinhart Lake.
The Modernization improvements at Laneda Ave. and Manzanita Ave. were recommended by the NW Area Commission on Transportation (NWACT) and approved by the Oregon Transportation Commission (OTC) for the 2008-2011 Statewide Transportation Improvement Program (STIP). Improvements include constructing left-turn storage lanes at both intersections with U.S. 101 north bound, improving pedestrian facilities, restriping, upgrading signage and guardrail.
Checking the five year crash history (1/1/2003 – 12/31/2007) adds one injury crash into a fixed object with two moderate injuries. This was an out-of-state south bound semi-truck that lost control and overturned within the curve in June 2004. Adding an additional left turn lane, correction of a poorly configured left turn lane, using standard travel and median lane widths and flattening an existing 28 degree curve to a 20 degree curve will contribute to a potential decrease in crash rates.
To do the work, ODOT decided to have the contractor replace the culvert by building a temporary structure at grade over the culvert and perform the work under the structure with all lanes open on highway 101. The temporary structure will keep traffic above the work area while the culvert is being replaced and the new stream channel is being graded.
Funding for this project comes from the Fish Passage ($3.2M) and Modernization ($3M) programs.