Rendering of the new Mountain Highway Interchange
In its “BC on the Move: A Ten-Year Transportation Plan”, the BC Ministry of Transportation and Infrastructure prioritized upgrades to the Mountain Highway Interchange on Highway 1 in North Vancouver. The Province of BC, Government of Canada, and the District of North Vancouver are investing $198 million to improve access to-and-from Highway 1 in the Lower Lynn area to increase safety and reliability, and reduce congestion. The Mountain Highway Interchange project is the first of four phases of the Lower Lynn Interchange Improvements.
The BC Ministry of Transportation and Infrastructure retained Associated as prime consultant for the Mountain Highway Interchange upgrades. Key features of the project include a new partial diamond interchange and on/off ramps on Highway 1; a new five-lane Mountain Highway underpass; median and outside shoulder widening on Highway 1; realignment and widening of Mountain Highway from two to four lanes; and municipal roadwork improvements on the adjacent Keith Road and Brooksbank Avenue in North Vancouver. New on- and off-ramps to Highway 1 will better distribute traffic, and relieve pressure on neighbouring roads and interchanges.
Design Manager, Ron Gratz, tells us, “One of our challenges was to develop a design which accommodates future widening of Highway 1, an eastbound on-ramp, and other traffic movements, which will be implemented in subsequent phases of the Lower Lynn interchange improvements.”
To determine the future requirements, a future/ultimate interchange geometric and laning design concept was developed based on high-level conceptual options provided by the Ministry. The new five-lane Mountain Highway Underpass includes provisions to accommodate the addition of a future southbound to eastbound left-turn lane and future six-laning of Highway 1.
Major improvements to cycling and pedestrian facilities are incorporated in the design, including approximately 500 metres of sidewalks, one kilometre of on-road bike lanes, 400 metres of multi-use paths, and a new 5.2 metre-wide underpass beneath Mountain Highway, connecting existing trails to the east and west. The upgraded intersection at Keith Road/Brooksbank Avenue/Mountain Highway will separate pedestrians, cyclists, and vehicles, improving safety.
Significant upgrades and replacement of the existing utility crossings beneath Highway 1 using trenchless technology are also required. The road widening on Keith Road and Brooksbank Avenue is heavily constrained by the proximity of private properties and steep grades of existing driveways and accesses. Three cast-in-place retaining walls with a concrete privacy screen fence are proposed on Keith Road and Brooksbank Avenue to minimize impacts to private properties. Environmental enhancements are incorporated in the culvert and creek design to enhance fish passage. These include fish baffles in the two, new, large culvert crossings under Highway 1 and Mountain Highway, and a series of boulder weirs with large woody debris and wood wads in the realigned Keith Creek, as well as riparian revegetation plantings.
The design of drainage infrastructure, including major culverts, storm sewers, and catch basins, consider climate change impacts. “Climate Change Resilience Design Criteria” were developed and submitted to the Ministry for signoff as part of the design process. The design of the new Mountain Highway Underpass, pedestrian tunnel and retaining walls also consider a potential increase in temperature due to climate change.
The team developed construction staging and advance works plans--key tasks for this busy section of Highway 1. Early completion of the new Mountain Highway Underpass is critical to maintaining the construction schedule. The project was tendered in February 2017 with construction completion scheduled for late 2018.