Roads & Bridges
Roads & Paving
February 15, 2023 By Grant Cameron
B.C. is in the process of replacing Old Fort Road
In 2018, a landslide washed away the lone road into Old Fort, a community of 150 residents along the Peace River in northeastern B.C. Crews repaired the road but Mother Nature paid a return visit in the summer of 2020.
Following heavy downpours, the ground shifted, again causing severe damage to the thoroughfare. A 100-metre section of the roadway, named Old Fort Road, was carried approximately 300 metres down slope.
Vehicles could not get through to the area five kilometres southwest of Fort St. John. A temporary gravel access road was later installed in July 2020 and then replaced with a high-grade gravel road to serve the community. However, area residents are still waiting to hear what the permanent solution might be.
Peace River Regional District has not yet received a definitive timeline from the province on when the new road will be built. B.C. is responsible for all aspects of the road, including maintenance and construction development. A permanent fix is complicated by the fact the area is prone to future slides.
There are also considerations for the environment and certain species of fish, wildlife and plants. In addition, the area is covered by a treaty which affects 10 First Nations communities with territories in B.C.
A number of high-level road realignment options were developed by the Ministry of Transportation and Infrastructure (MoTI) in 2018 for discussion purposes and to address slope stability and access reliability. The project team met in fall 2020 to determine which options were viable and decided to rule out three as they failed to demonstrate a superior alignment.
The MoTI engaged McElhanney Ltd. to provide high-level geometric, structural, environmental and hydrotechnical design input of the remaining options. Geotechnical review was done by BGC Engineering Inc. and overall project management services were provided by Stantec Inc.
An extensive report was presented to the MoTI.
The report addresses the pros and cons of each of the options as well as issues that could result from each one. The consultants evaluated the alignment options, developed several new alignments to bypass and mitigate the slide area, and conducted a high-level screening exercise to shortlist one or more options. They also prepared information about the potential impacts on property and high-level cost estimates.
“The review determined that the best option for access to the community of Old Fort is to continue using the existing route, which is a gravel road, and conduct further geotechnical assessments to identify potential improvements,” an MoTI spokesperson said in a statement prepared for Rock to Road. “This recommendation was determined based on a multiple account evaluation that studied reliability, cost, geotechnical, structural, environmental, hydrotechnical, and constructability considerations.”
At $30 million, the option being proposed is the least costly and is expected to have the lowest environmental impact.
The gravel road put in place after the slide would be left in its current alignment and grade without undertaking any stabilization of the sloped landslide area. The scenario recognizes that the gravel roadway would be impacted by future landslides.
The report notes that the option does not require any new construction but that future ongoing rehabilitation will likely be required due to its unknown access reliability associated with ongoing slide risks.
The MoTI is planning to do further assessments to further refine the preferred option for the roadway.
“The ministry is now undertaking further geotechnical assessments, including drilling and instruments installed in the boreholes, which will help inform next steps,” the MoTI spokesperson stated. “Any future works done by the ministry will follow the province’s environmental guidelines and required legislation to identify environmental risks.
“The effects of climate change include more severe weather patterns, which can influence slide movement. Geotechnical investigations will help the ministry understand what mitigative works can be undertaken to improve slide stability.”
The team also considered whether to upgrade the gravel road to current MoTI standards and undertake significant stabilization efforts to reduce future earthflow movements. But going that route, the consultants found, would require extensive field investigation to develop a more robust understanding of existing geohazards.
There would also be additional costs for a pile wall, and extensive drainage improvements required to mitigate hydrotechnical challenges due to the steep slope. Estimated cost would be $200 million.
Another alternative was to build new roadway south of the landslide area that ties into existing roads. Three slightly different configurations were proposed, which would require construction of bridges. Depending on the configuration, estimated costs range from $187 million to $243 million.
The alternative is further complicated by the fact that extensive field investigation would be required for all three configurations to develop a more robust understanding of existing geohazards.
Because river crossings would be required, permits would be needed from agencies responsible for in-stream works.
There would also be the potential for significant environmental impacts, causing extensive permitting efforts and approvals and possible costs for reclamation work or mitigation strategies.
Further, there is the potential threat the alternative would pose to many endangered and species of special concern, including birds, mammals, amphibians and plants.
The project team ruled out new access roads from the north, west and east.
A route from the north provided the shortest distance between Old Fort and the City of Fort St. John but, if built, would result in a steep grade of up to 25 per cent.
To reduce the grade, the road would need to be switch-backed up a hill and across unstable landslide terrain. There would also be costly geotechnical design options such as ground anchors, anchored pile walls and extensive drainage works.
Meanwhile, a route from the west would require more extensive geotechnical measures and still be vulnerable to potential future advances of the earthflow while one from the east would go over both active and dormant landslide terrain and present significant challenges for both design and construction.
The slide area is immediately above the Peace River, which is known to contain over 39 species of fish. Side channels on large rivers also generally provide refuge for smaller fish looking to avoid strong currents.
The area under study is covered by a treaty which affects 10 First Nations communities. They are Blueberry River, Dene Tha, Doig River, Fort Nelson, Halfway River, Horse Lake, McLeod Lake, Prophet River, Saulteau and West Moberly.
Since the 2018 landslide, an automated monitoring system has been on site at Old Fort to provide continuous updates on any ground movements in the area and an operating protocol is in place to respond appropriately.
An earlier report from British Columbia’s chief inspector of mines indicated that despite geotechnical assessments, the root cause of the 2018 slide remains inconclusive.
The report said it’s not clear if a cause will ever be determined with certainty, but that a nearby pit’s stockpile of gravel combined with natural slope instability and rain that was 44 per cent above average may all have been factors.
Earlier this year, final evacuation orders were lifted on several properties and sections of two roads near the community of Old Fort. They had been issued in 2018 and 2020.
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