Highway 40 South of Kananaskis Lakes - Epicentre of the Storm

Highway 40 South of Kananaskis Lakes - Epicentre of the Storm By: Des Kernahan, P. Eng. Senior Transportation Engineer Associated Engineering and Erin Rooney, P. Biol. Biologist/Regional Manager Summit Environmental Consultants, Inc. Paper prepared for presentation at the Emergency Repair and Construction of Transportation Infrastructure Damaged by Catastrophic Environmental Events session of the 2014 Conference of the Transportation Association of Canada Montreal, Quebec 0 Abstract The 2013 floods brought enormous changes to the natural and man-made landscapes in many parts of southern Alberta. Associated Engineering was hired by Alberta Transportation to coordinate, prioritize and determine site specific strategies for repairing a 55 km stretch of Highway 40 south of Kananaskis Lakes, southwest of Calgary, Alberta. This section of highway traverses the Highwood Pass, the highest paved road in Canada, and is located adjacent to the headwaters of the Highwood River. This was the epicentre of the June 19 to 22, 2013 rainfall event, where over 325 mm fell, and was the origin for the flood damage and devastation that travelled downstream through numerous communities, including High River. A total of 117 distinct sites with flood damage were identified, including debris flows across the highway, washouts, culvert blockages, erosional scours, and hydrological changes that carved new channels where they had never existed prior to June 2013. Each site was triaged into one of four categories, which were defined as follows: Stage 1 – required to provide access for construction operations; Stage 2 – required to open the highway to the public; Stage 3 – work off the road surface required to fully restore the highway cross-section; and Stage 4 – major works requiring substantial engineering design effort. The Stage 1 work was initiated immediately, using Alberta Transportation’s local highway maintenance Contractor. A combined Tender was then issued, with an interim completion date in the fall of 2013 for the Stage 2 work and a final completion date in the summer of 2014 for the Stage 3 work. Some Stage 4 work continues to be worked on as separate Tenders or integrated into the existing contract in 2014. One of the greatest challenges of the project was the environmental component, as over 50 of the sites required some form of regulatory approval under the Provincial and Federal legislation. Several sites required channel reconstruction, including over 250 metres of a watercourse classified as highly sensitive due to its important bull trout spawning habitat. In order to improve the local stream hydraulics, re- establish connectivity of the channel to maintain fish passage, and protect the highway from future flooding events, the watercourse was re-aligned with its historical channel. Fisheries mitigation measures, engineering plans, as well as hydrotechnical and fluvial geomorphologic assessments were required for these submissions. This paper will review the effects of the flood, and discuss numerous challenges faced throughout the assessment, design and construction phases of the project. 1 Introduction Highway 40 is a Provincial highway located in mountainous terrain in southwestern Alberta. The highway provides access to “Kananaskis Country”, an area south of the Trans-Canada Highway between the City of Calgary and Banff National Park. Attractions in this area include Peter Lougheed Provincial Park, Kananaskis Village, Nakiska Mountain Resort (location of the 1988 Winter Olympics) and many other tourist and recreational facilities. South of the major tourist sites, Highway 40 traverses the Highwood Pass, which at an elevation of approximately 7,200 feet above sea level is the highest paved roadway in Canada. Beyond the pass, Highway 40 continues southeast to Highwood House, where the intersection with Highway 541 and 940 provides an alternate access route (from the south and east) to the Kananaskis area. The section south of the major tourist sites is low volume with an average annual daily traffic volume of 350 vehicles per day, and is closed between December 1 and June 15 of each year due to major wildlife migration movements in the area. A location plan showing this section of Highway 40 is included in Figure 1. The weather in this area is typical of the Rocky Mountains with quickly changing conditions, and snowfall beginning in October and lasting through June annually. Highway 40 was built as a two lane paved road to replace the original gravel forestry trunk road. Highway 40 was built 30 - 40 years ago to service the growing demand for mountain recreation, including skiing, horseback riding, hiking, white water sports, motor biking, road biking, hunting, and camping. Provincial parks set up complemented with a world class golf course, hotel, and convention centre using newfound Alberta wealth from oil and gas revenues. Highway 40 also serves forestry and hydro-electric industries in the area. Between June 19 and June 22 of 2013, a combination of natural conditions (large snowpack and frozen ground) combined with a major extended rainfall event caused extensive flooding and damage to numerous locations in Southern Alberta. The extremely large volume of rain resulted when a low pressure system stalled over southern Alberta, pushing humid air from the northeast over Calgary towards the mountains. Over 75 millimetres of rain fell in Calgary, and over 100 mm fell in Canmore, which is located on the Trans-Canada Highway just east of the Banff Park Gates. The heaviest rainfall, however, occurred further south along the eastern ranges of the Rocky Mountains, with the “epicentre” of the storm lying just east of Highway 40 in the southern Kananaskis area. In this area, over 325 mm of rain fell, as illustrated on the rainfall contour map (Figure 2), resulting in severe erosion and damage to the natural environment and constructed infrastructure. Drainage courses were completely overwhelmed by the incredible volume of water, with a hydrometric station on the Highwood River measuring flow volumes in excess of 30 times the average flow rate prior to the gauge breaking as a result of the force of the event (Figure 3). From this area, the water travelled east through the watershed causing extensive damage in downstream communities including Calgary and High River. This section of Highway 40 was significantly impacted as a result of being located through the valley of the epicentre of the storm. Most of the damage consisted of debris such as rocks and trees that washed over the highway and plugged ditches and culverts; erosion scours that washed out the roadway embankment, and morphological changes in watercourses that carved completely new drainage channels. In the immediate aftermath of the flood, efforts were focussed on re-opening the Trans- Canada Highway and other highways with a high economic impact, primarily completed on an emergency basis through Alberta Transportation’s Maintenance Contractor. Once these emergency repairs were complete, efforts re-focussed on opening the rest of the highway network, including Highway 40,and Engineering Consultants were retained to complete assessments of damage, design of repairs, environmental assessments and permitting, tendering, and supervision of construction. Design Stage An initial overview assessment to identify the number, location and severity of the various damage sites was completed for Alberta Transportation by Thurber Engineering along Highway 40 from the Trans- Canada Highway to Highwood House via helicopter. Associated Engineering and subsidiary company Summit Environmental Consultants Inc. (Summit) were subsequently retained by Alberta Transportation 2 in mid-July to complete the engineering work for the southern section, a 55 kilometre long stretch from the Peter Lougheed Park entrance to Highwood House shown in Figure 4. There were 117 different sites along this stretch of highway that were washed out or damaged due to the heavy erosion, including 20 locations where the highway was completely impassable. At one site, approximately 60 m of highway was completely washed away, and the existing multi-plate structure was damaged beyond repair. As a low volume highway serving no settlements and primarily recreational users, this section of Highway 40 had been closed and gated on both ends to prevent public access since the flood. Upon award of the assignment, the project team quickly organized a site investigation which was completed on July 23, 24 and 25 of 2013. As one of the primary driving forces behind the project methodology was accelerating the schedule, the investigation had multiple purposes that went beyond a typical preliminary survey. This included assessing the extent of damages, determining the proposed repair strategy, measurement of quantities, and understanding environmental sensitivities at each of the 117 sites. This required involvement of senior engineering and environmental staff as part of the investigation, as key design decisions would be made in the field. To maximize efficiency, GPS enabled cameras and voice recorders were used for data collection, which were subsequently georeferenced to create a data management system using mapping software. A LiDAR survey was also completed to ensure accuracy of quantities at the sites with larger volumes of material to be moved, and to generate a survey of the post-flood water course conditions both within and outside of the highway Right-of-Way for the required hydrotechnical assessments. The general intent of the project was to re-establish the original highway design. For the most part, the highway is in the northeast side of the valley, with mountains to the northeast and the valley to the southwest. There were numerous sites on the mountain side of the cross section with rock debris flows crossing the highway and/or filling the ditches and culverts creating excess material. There were also numerous sites on the valley side of the cross section with major erosion scours that required fill material. Wherever feasible, material from sites with excess debris was used to repair erosion scours, eliminating the need to haul debris off site and significantly reducing borrow material requirements.

Load more