Manitoba Hydro is a CrownCorp. of the province of Manitoba, Canada. It provides electric energy and natural gas service throughout Manitoba. The company also exports electricity to over 50 electric utilities and marketers in the Midwestern United States, and Ontario and Saskatchewan, Canada.
Manitoba Hydro generates approximately 98% of its power through 14 hydroelectric generating stations on Canada's Nelson, Saskatchewan, Winnipeg and Laurie rivers. Most of these generating facilities are located in northern Manitoba, while the bulk of Manitoba Hydro's customers — including the provincial capital, Winnipeg — are located in the southern part of the province.
Manitoba Hydro's system control center (SCC) remotely monitors and controls all of Manitoba Hydro's generating and converter stations from its Winnipeg location. Therefore, ultra-quick and reliable communications capability with these stations is essential. The Interlake Nelson River Optical Cable System (INROCS) is the fiber-optic link between the SCC in the south, the generating and converter facilities in the north and all the facilities in between.
The sheer length of this project, along with weather, terrain, remoteness, schedule restrictions and regulatory requirements, led to several unique and interesting construction challenges.
The routing of INROCS extends from Winnipeg, located in southern Manitoba, to the Gillam area, in northern Manitoba — a distance of more than 1150 km (714 miles). The route of the fiber-optic cable parallels and is contained within Manitoba Hydro's transmission line right of way and Manitoba Highways' road right of way.
The fiber-optic cable consists of 48 strands of fiber bundled together and protected by alternating layers of polyethylene coating (3) and corrugated stainless-steel sheathing (2). The cable is delivered in reels up to 8 km (5 miles) in length. The design called for the cable to be installed in a protective high-density polyethylene (HDPE) conduit buried at a depth of 1.5 m (5 ft) below grade. The HDPE conduit has an inside diameter of 3 cm (1.25 inches) with a standard dimension ratio (SDR) of 11. It was supplied in lengths up to 1.5 km (0.93 miles).
Three major contracts were issued for this project: one contract for Stage I, the southern half of the project; the second for Stage II, the northern half; and a directional-drill contract for 21 major water crossings. Various smaller contracts for tree and brush clearing, ice road construction, and inspection services were also awarded.
Stage I construction started on Nov. 12, 2002, and overlapped with Stage II construction, which was substantially completed on April 8, 2004. Work took place year-round throughout this period. Construction crews and inspection staff worked in temperatures ranging from -40°C (-40°F) in the winter to +35°C (95°F) in the summer.
The first step in construction was installing the conduit. This was done using various methods including:
Initially, a dozer with a ripper tooth pre-rips a trench path for the plow to follow. Led by a tow cat, the plow pulls a shank, placing the conduit at 1.5-m (5-ft) depth as it moves along. In ideal soil conditions — clay/loam/sand — up to 12 km to 15 km (7.5 miles to 9 miles) of conduit can be installed in one day.
In areas where the conventional plow train method previously described was not suitable — for example, in wet areas just prior to the spring thaw — a spider plow was used. This plow consisted of three separate units: the traction unit, the spider plow and the reel carrier. The spider plow is winched ahead by the traction unit. Each wheel of the plow can articulate independently to move up, over and around obstructions. Typical rates of production were 300 m to 500 m (984 ft to 1640 ft) per day.
- Directional drilling
The conduit was installed using this method under 275 water crossings, ranging from intermittently wet streams to major rivers over 460 m (1500 ft) in width. Also, more than 250 road, highway, railway and utility pipelines were crossed using the directional-drilling method. This involved the drilling of a pilot hole under and across the channel or obstruction and then pulling back the HDPE conduit through the bored hole.
- Rock saw
For limestone or fractured rock areas, a rock saw was most suitable.
The conduit was installed by a track-hoe in areas where other methods were unsuitable.
Where granite was encountered, rock blasting was the only method that would allow placement of the conduit.
As sections of conduit were installed, the conduit ends were electro-fused together producing long contiguous sections of conduit. Cable was then installed into the conduit by the jetting method. This involved the use of jetting devices, which would push the cable inside the conduit using high-velocity streams of air. A series of these jetting devices at cascade stations set at intervals of 1.2 km to 1.8 km (0.75 miles to 1.1 miles) enabled reels of cable of up to 8 km (5 miles) in length to be installed. The cables were installed into large (slightly larger than a coffin) polymer-concrete boxes called splice vaults, where they were spliced by Manitoba Hydro staff. For the project, 177 splice vaults were installed.
Terrain conditions encountered on this project ranged from clay/loam (plowing 12 km/day to 15 km/day, or 7.5 miles/day to 9 miles/day) to muskeg/swamp (directional drill or winter work) to limestone/granite (blasting or rock saw — 50 m/day to 400 m/day, or 164 ft/day to 1312 ft/day).
In terms of production, one good day of plowing could equal 30 to 45 days of blasting/rock saw. Of course, this played havoc on the schedule.
Certain sections of the route consisted of swamp and muskeg, which were only accessible in the winter when completely frozen. While those who don't live in Manitoba might think the province is completely frozen all of the time, that's not so. The access period for these areas was generally limited from mid-December to mid-April, the coldest time of the year in that region. The pace of construction during those months slowed dramatically, because of the cold temperatures, winter storms, equipment breakdowns and limited daylight hours.
Another interesting aspect of the project was the construction of winter ice roads. The routing of the fiber-optic line crossed three major rivers in an area where there were no permanent roads. These rivers freeze over in the winter, but not to a thickness that's able to support construction-equipment traffic. In order to install the conduit/cable under these rivers, it was necessary to construct winter ice roads. Initially, this was accomplished by packing existing snow cover with snowmobiles and then repeatedly drilling holes in the ice to flood and re-flood the area until the desired ice thickness — generally 1 m (40 inches) — was achieved. This thickness provided a bearing capacity that could support the weight of a D-10 cat. Regular monitoring of the condition of the ice and its thickness was required, as river flows tend to erode the underside of ice.
Manitoba Hydro's first corporate goal is to “continuously improve safety in the work environment,” which made it a top priority for all workers on the project to work safely and go home at night.
For the INROCS project, a job safety plan (JSP) was prepared for each of the construction contracts. The JSP examines the work on a high-level basis and identifies potential hazards. Protective barriers were put into place to protect workers from the identified hazards. In addition, every individual work crew took part in a tailboard meeting before starting work each day. This meeting addressed the specific hazards of that day's work and workers discussed measures that would mitigate the dangers. Overall, the safety record on this project was excellent, with only one significant lost-time injury recorded.
Another of Manitoba Hydro's corporate goals is to “be a leader in strengthening working relationships with Aboriginal peoples.” Routing of the INROCS project passed through several 1st Nations Resource Management Areas (RMAs). Major contracts on this project were structured so that bidders would receive credit in the tender evaluation process for showing aboriginal participation. Although the work was highly specialized in that plows, rock saws, directional drills, blasting and jetting equipment are not typically owned by northern Aboriginal communities, aboriginal participation as subcontractors occurred in the supply of equipment operators, general laborers, hotels, meals, fuel and materials. Additionally, Manitoba Hydro awarded several contracts to 1st Nations construction groups for tree clearing, ice road and repeater station site construction. The total estimated value of aboriginal participation was CDN$2.3 million.
A third corporate goal of Manitoba Hydro is to “be proactive in protecting the environment.” For the INROCS project, the services of an environmental consultant were engaged with a two-part mandate:
To prepare an environmental assessment report (EAP) to examine and present general mitigative measures for project impacts to pollutants, soil, vegetation, wildlife, aquatic life and heritage resources.
To prepare an environmental protection plan (EPP) to present specific environmental measures for the 275 stream and river crossings throughout the project length. The EPP is a user-friendly document that “supplements project design, construction and operating specifications to prevent or minimize adverse environmental effects arising from the construction and operation of the project.”
All contractor supervisory staff and Manitoba Hydro inspection staff were well versed in the EPP requirements, which included buffer zones for stream crossings and monitoring and controlling of directional drilling fluids and cuttings. With the cooperation and efforts of Manitoba Conservation, Fisheries & Oceans Canada, the company's contractors, inspectors and in-house environmental staff, all of the potential environmental issues were identified, reviewed and mitigated in a manner that met or surpassed regulatory requirements and corporate goals.
Overall costs for this project totaled approximately $75 million. The civil construction component, which included project management, inspection and contractor costs (excluding materials), was approximately $33 million.
Ken Ducheminsky, P.E., is a civil engineer with Manitoba Hydro in Winnipeg, Manitoba, Canada. He graduated with a bachelor of science degree from the University of Manitoba in 1979. He has 25 years experience in both the public and private sectors and has construction and design experience in the areas of general civil construction works, water resources, municipal infrastructure and natural gas installations. KDucheminsky@hydro.mb.ca