Abstract Manager

Highway 666 is a two-lane Alberta highway south of the City of Grande Prairie. The ‘Wapiti Hill’ section climbs out of the Wapiti River Valley using a sidehill cut through the south escarpment. The 2.5 km long segment climbs a long 7% grade and experienced increasing slide movements and temporary road closures. The planning study explored the social, environmental, and economic sustainability of Highway 666’s Wapiti Hill segment. This included looking at the relevant design standards and policies, community interests and government role, both provincial and municipal. To keep the roadway serviceable/safe required increasing maintenance activity, however, the road gradually eroded, compromising the cross-section and reducing the posted speed from 80 to 50 km/h. A geotechnical assessment confirmed that the area would continue to slide and that within the next 5 years more aggressive slide events may occur, presenting a significant safety concern if it occurred while the highway was open to traffic. The cumulative effect of the incremental slide movements would likely require the segment be downgraded to a gravel surface, while continuing to require ongoing maintenance. Alberta Transportation & Economic Corridors (TEC) commissioned the study to examine the long-term costs and benefits, impacts and issues (both technical and community), involved in continuing to maintain and operate this failing highway section. The study developed several alternatives to understand the available choices for the future highway configuration. In addition to finding a viable long-term solution, the study addressed the concerns and impacts arising from a revised road network, including the risks and trade-offs for the province and the municipality; costs, reliability, and safety; and anticipated community support. The feasible alternatives were evaluated through a Business Case comparison to identify a preferred alternative and develop an implementation plan. The study found that the reactive maintenance practice was not sustainable. To keep the roadway open and safe required a major rehabilitation, with an estimated $50M cost, and increased the maintenance cost to at least $1M/year. Furthermore, the risk of an underlying catastrophic slide would remain. Realigning Highway 666 around the Wapiti Hill segment utilizing a municipal roadway, devolving existing Highway 666 to the municipality and downgrading the Wapiti Hill segment to a more manageable 2-lane gravel roadway was recommended.