PSPC requires upgrades to four (4) culvert crossing locations of the Alaska Highway, BC.  The work is proposed to address drainage capacity, structural degradation, drainage structure maintenance and fish passage concerns at the four culvert crossings.  The locations, existing conditions and issues at each of these locations are described below:

• Km 458.0 Site (approximately 3 km west of Fort Nelson): The existing culvert crossing includes one 900 mm diameter Corrugated Steel Pipe (CSP) culvert which is corroded and currently undersized.
• Km 596.8 Site (Summit Pass): The existing culvert crossing includes one 1200 mm diameter Wood Stave Culvert which is undersized, significantly deteriorated and at the end of its service life.  The culvert has deformed to a state such that it is at risk of collapse.  The outlet of the culvert is perched, presenting a barrier to potential fish passage upstream.
• Km 647.4 Site (Toad River): The existing culvert crossing includes one 1200 mm diameter CSP and one 1500 mm diameter CSP which are undersized, corroded and deformed.  The outlets of the existing dual culverts are perched presenting a barrier to potential fish passage upstream.  The culverts are located within a section of highway with vertical geometry which does not meet the Transport Association of Canada design guidelines for the posted speed limit (i.e. vertical sag curve, clear zone).
• Km 676.2 Site (approximately 28 km west of Toad River): The existing culvert crossing includes one 900 mm diameter CSP culvert which is undersized and subject to debris flows which block large portions of the culvert.  Maintenance to remove the debris from within the culvert is regularly required but difficult to complete due to the relatively small dimeter of the existing culvert.

Upgrading these culvert crossings presents an opportunity to install replacement drainage structures with greater flow capacity, improve\ fish passage with the streams, repair and mitigate erosion concerns, and reduce ongoing maintenance costs.