Roads & Paving
B.C. Roadbuilder tackles construction challenges
A successful highway project through spectacular scenery has had its share of challenges
February 1, 2010 By Andy Bateman
For travellers on Highway 97, British Columbia’s north south arterial route, the Okanagan corridor between Kelowna and Penticton has often been one of the highway’s most memorable stretches, in terms of spectacular scenery as well as frustrating traffic congestion on winding two lane sections. For the roadbuilder on a major highway upgrade project there, the expected challenges of construction through this rugged terrain were accompanied by unexpected natural events including a potential rock slip and wildlife rescue.
For travellers on Highway 97, British Columbia’s north south arterial route, the Okanagan corridor between Kelowna and Penticton has often been one of the highway’s most memorable stretches, in terms of spectacular scenery as well as frustrating traffic congestion on winding two lane sections.
|A typical blast on the Highway 97 project yielded between 3,000m3 and 10,000 m3 of rock.|
For the roadbuilder on a major highway upgrade project there, the expected challenges of construction through this rugged terrain were accompanied by unexpected natural events including a potential rock slip and wildlife rescue.
|Subcontractor Paramount Drilling and Blasting utilised two Sandvik Tamrock Ranger 700 drill rigs, one Ranger 800, one 1500 Ranger, a tank drill and an excavator drill on the Highway 97 project. |
|The $38.6 million Highway 97 project involves the widening and straightening of a seven kilometre section in the between Kelowna and Penticton.|
|Material extraction and haulage has been a major component of the Highway 97 job. Arthon Contractors Inc.’s mobile equipment fleet included six Kenworth Heavy Duty highway trucks with side dump and end dump trailers. |
|The crew of general contractor Arthon Contractors Inc. and the company’s new fleet of four Caterpillar 775F haul trucks. |
|Haul trucks loaded by this Komatsu PC 1250 LC excavator included four Caterpillar 775F units, four Caterpillar 740 Articulated Dump Trucks (ADTs) and six Terex TA40 ADTs. The PC 1250 LC was fitted with a 7.65m3 bucket and filled the ADTs in 2.5 passes. |
|Abe Kruger (in red) with the Penticton Indian Band works for Arthon, setting instrument gauges to detect movement in the project’s famous ‘rock slip.’ Test results confirmed that the face was stable enough to withstand blasting and support heavy equipment. |
Steve Dimond, project engineer and partner with general contractor Arthon Contractors Inc., explains that work on the widening and straightening of a seven kilometre section north of Summerland began in February 2008. The $38.6 million four laning project is scheduled for completion by summer 2010 and, unexpected events aside, Dimond still expects the project to be completed ahead of schedule.
Material extraction and haulage has been a major component of the job, with some 1,100,000 m3 of rock removal and 1,200,000 m3 of dirt removal. Both materials have been used for embankment fill, while excess rock has been stockpiled and crushed on site for roadbase and asphalt aggregates.
At the design stage, it was recognized that the new road alignment would require road closures and several focus groups were held by the province’s Ministry of Transportation to reduce construction impacts on the travelling public. Dimond notes that over fifty stakeholders were consulted and this input, supported by traffic data confirmed that night closure windows would be the best solution wherever possible. Traffic data indicated that 14,000 vehicles travelled this section of Highway 97 during daylight hours in the peak season compared to an hourly average of only 50 vehicles at night.
Another important consideration at the design stage was the project’s extensive drilling and blasting requirements. It was decided early on that night blasting was impractical for safety reasons, so a number of mitigation measure were put in place to minimise traffic delays resulting from blasting during the daylight hours.
As Dimond points out, the process of blasting on a roadbuilding project is significantly more involved than quarry blasting where public access is restricted, uniform rock faces are often already developed and shot rock is often left in place for some time. Contrast that to highway blasting, where the process requires closure of the blast zone to the public before the blast and the immediate removal of shot rock after the blast before the highway can be reopened.
In terms of the blasting process itself, Dimond estimates that about 700,000 kg of explosives have been used on the project in total. Here again, advance work was done at the design stage, with a pre-blasting analysis performed to consider the effects of blasting on the local population. The resulting blasting procedures were site specific, with a project staff member present at locations that might have been vulnerable during a blast.
Blast patterns varied according to local rock conditions, although a common blast pattern consisted of 16 to 50 holes, each 100mm in diameter in a 3m by 3m pattern. The backline was drilled at 0.75m spacing with 75mm holes with buffer holes at 2m spacing. To complete this work, subcontractor Paramount Drilling and Blasting utilised two Sandvik Tamrock Ranger 700 drill rigs, one Ranger 800, one 1500 Ranger, a tank drill, and an excavator drill. A typical blast yielded between 3,000m3 and 10,000 m3 of rock Holes were charged with a cast booster or emulsion (1.5×8”) primer and 25 to 50 kg of ANFO (Ammonium nitrate – fuel oil) blasting agent, with non-electrical initiation through shock-tube assembly with 25 millisecond delays between holes and 500 ms down the hole detonation. Of all the blasting work completed on this project, probably the best known was the remedial work following the discovery of a huge section of unstable rock in October 2008. (See sidebar: Unstable rock discovery and treatment).
Material excavation and haulage on this project was completed by an extensive mobile equipment fleet that included Caterpillar D10 and D8 dozers, Komatsu PC 1250 LC excavator, and four Caterpillar 775F haul trucks. Additional equipment included a John Deere 450CLC, Komatsu PC400LC-8 and Volvo 210B excavators, four Caterpillar 740 Articulated Dump Trucks, six Terex TA40 articulated rock trucks, six Kenworth Heavy Duty highway trucks with side dump and end dump trailers, two Caterpillar graders (14G + new model rental) and several Bomag BW213DH pad foot compactors equipped with Bomag’s Variocontrol Intelligent Compaction system as well as a fleet of mechanics service trucks, water trucks, fuelling trucks and pickup trucks. Several other hired excavators were used on an as needed basis.
Arthon also completed all gravel production with an Elrus spread comprised of a 2442 primary jaw crusher, Sandvik H3000 and H4000 cone crushers, a 6×20 inclined screen deck, Elrus conveyors and surge bins, powered by a 400kW power plant. Two Volvo L330 wheel loaders were on raw material supply and product handling duty in support.
The paving of the 7km four lane project includes 36,000 tonnes of Superpave mix and some 3,000 tonnes of Class 1 medium mix for side roads and off-highway intersections. Peter’s Bros. Construction Ltd. from Penticton are providing the paving using a Roadtec RP195 Paver, a Roadtec RX60C Milling Machine, Caterpillar 634C, Ingersoll Rand PT 240, and Dynapac CC424 compactors, with the paving train supplied by a 300 tonne per hour Aesco – Matsen asphalt plant set up in the material stockpile area, high above the highway.
Environmental protection measures are now an integral part of virtually all major roadbuilding projects and this job was no exception. Measures included the use of two dedicated water trucks to minimise fugitive dust generation on adjacent dirt side roads as well as portions of the highway itself.
On this project, the Ministry of Transportation also engaged a team of Qualified Environmental Professionals (QEPs) and goat specialists to monitor the activity of the region’s mountain goats and ensure their protection from construction activity. Prior to excavating operations, for instance, the QEP’s performed a sweep of the area to identify and develop mitigation measures to protect the goat population and other wildlife. On that note, Arthon Contractors made the news again with the rescue of the mountain goat “Houdini” from the same rock crevice that triggered the rock slip prevention program in October 2008.
Arthon’s key individuals who have run and completed this project include project manager Graham Bennison, chief superintendent and partner Guy Ferrari, Superintendent Jim Masson, with Dimond, a Gold Seal Certified project manager, in charge of Quality Control, Traffic, Safety & Contract Administration.
|Team effort solves unstable rock headache |
One of the most unusual and challenging situations faced by Arthon Construction during the Highway 97 contract was the discovery of a section of unstable rock face in October 2008.
The drama began when a small fissure some 100 mm wide was noticed by Geotechnical Engineers high above the rock face, directly above the highway. Within 48 hours, the fissure was more than 1m wide and a large fracture line extending from lower areas to well up the mountain was expanding. The same night, Arthon Construction’s crew discovered loose rock debris and, with up to 250,000 cubic metres of unstable rock on the move, immediately closed the highway as a safety precaution.
With the situation now front page news, geotechnical experts, the province’s ministry of transportation, contractors and specialists gathered to devise a plan to stabilize the rock face. One of the first challenges was to determine whether the face was stable enough to withstand blasting and support heavy equipment. As Arthon Contractors’ Steve Dimond noted at the time: “We wanted to test and see what a blast could do and how to deal with working in a limited space. Visual and electronic monitors on the hill were used to assess what affect each blast had in terms of movement and rotation of the slope. Until it was assessed, we couldn’t move forward and the tests provided the necessary three dimensional data to confirm that the slope was stable.”
Once it was established that the mass could withstand drilling, the goal was to progressively remove material from the top of the bluff and put it at the toe to stabilize the base. Drilling equipment was initially put on a shelf above the fissure as the whole rock mass was moving, limiting the size of the first blast to 1,000 cubic meters. Blast sizes were then increased incrementally to 3,500 cubic metres, 6,000 cubic metres and finally 18,000 cubic metres.
Monitoring results showed that the slope continued to move 10-20 millimetres a day during the first week of work. Face movement then slowed down to about 8mm a day for the next two or three days, slowing further still to about 4mm a day by the end of week two. After the 18,000 cubic metres blast, there were two consecutive days without movement. Based on those results, the chief geotechnical engineer concluded the slope had reached a point where it was secure and traffic could resume below. In all, a total of about 34,000 cubic metres of unstable rock was blasted from the hill side before Highway 97 was reopened.
Looking back, Dimond has high praise for those who worked round the clock to resolve a potentially dangerous situation and safely reopen Highway 97. “Full marks to the Arthon Construction team, Paramount Drilling & Blasting and Chimera Springs Rock Works for their expertise, commitment and hard work during a difficult time.”
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