Construction work is well advanced on what is being called ‘the biggest construction project in Canada’. The 1,550MW La Romaine hydroelectric complex will be situated on Rivière Romaine north of Havre-Saint-Pierre, in the Cote-Nord region of Quebec. Construction of the four reservoir-powered plants and a permanent 150km long road will cost an estimated CAD 6.5bn (USD 6.8bn).

Average annual production at the complex is anticipated to be 8TWh, enough to power more than 450,000 households.

In April 2010 Canadian contractor Simard-Beaudry Construction was awarded the downstream section of the Romaine 2 intake tunnel for some CAD 63M (USD 66M).

The first step in starting up this major project was putting together a strong team to build the tunnel. The team from Simard-Beaudry had just completed two other large tunnel projects – the Rupert Transfer tunnel and the Rio Tinto Alcan tunnel.

Drilling on the downstream access portal excavation of 10,400 cu m began in mid June 2010.

Blasting cycle
The actual access tunnel began a month later using a pilot and slash technique with two, three boom Sandvik jumbos drilling a9.5m by 12m wide full face heading for 460m down to the main tunnel. Work began on the main tunnel in November 2010 driving towards the penstocks and in the other direction towards the access tunnel for the surge shaft and beyond.

The full face top heading 12.5m wide by 8.9m high is being driven using two Sandvik three boom jumbos drilling 57mm dia blast holes with 5.8m long steel with an average 159 blast holes and five 100mm relief holes per round as shown in Figure 2.

Once drilling is complete, Simard-Beaudry moves in two Skylift platforms that are used by the blasting crew to pneumatically load AMEX using Orica ANFO Mizers to control the loading rate and avoid overloading in central holes. The use of ANFO Mizers helps to reduce spillage of ANFO and results in lower levels of AN in mine wastewater, thereby reducing the environmental impact.

To reduce micro fractures in the remaining rock, cartridge explosives were loaded in buffer and perimeter holes to a typical powder factor of 2.6 kg/cu m. Holes were initiated using Orica 6m Exel Long delay non-electric detonators.

The full face, round when in dry conditions, could be loaded in about two hours ready to blast and advance an average 5.2 to 5.3m. After venting out fumes in 20 to 30mins with a 96-inch (2.4m) diameter ventilation system, work moved onto the next stage of the cycle.

Muckout and support
This involved watering down the muck pile and beginning the excavation of blasted rock using a Komatsu WA-600-6 or CAT 988H (6.4cu m) loader filling the 50-ton Cat 773 trucks.

Once the mucking is complete – in typically three to four hours – a Cat 345 shovel with a large ripper tooth is brought in to scale the face removing any loose rock ready for inspection for rock bolt support and wire mesh installation. This step is carried out using either a two or three boom Sandvik jumbo drilling 4m deep holes for typically six rock bolts per round.

The bolts are installed using two custom designed sliding lift platform trucks also used for the installation of the wire mesh. Once the wire mess is installed up to the face the survey crew can come in and layout the face for the next round and shoot the laser to line up the data drill jumbos to begin the cycle once again. When conditions are good the full cycle can be completed in about 15 hours.

Driving the full face intake towards the powerhouse at about 250m the tunnel is expanded in an area called the transition where the main tunnel is widened and split to form two penstock tunnels. These are being driven as full-face headings 7.35m by 7.45m for a length of 245m. Here shorter rounds are being driven to minimize overbreak for these tunnels that will be concrete lined to a finished inside diameter of 6.45m. Excellent results are being achieved again due to the accuracy of drilling provided by the data drill jumbos from Sandvik.

As part of the downstream end of the tunnel another important part of this contract will be the massive surge shaft excavation. The access tunnel top heading has been excavated 45m to the base of the future surge shaft.

Work is just beginning on excavating a 3m diameter raise to the surface using an Alymak raise climber. This work has been sub contracted to CMAC Thyssen to drive this 163m raise to the surface.

Once the raise is completed Simard-Beaudry will begin blasting the upper surge chamber 32m in diameter in shallow benches down 62m using the 3m diameter raise as a muck chute. Once this section has been excavated, walls bolted and covered in wire mesh then CMAC Thyssen will return to sink the lower surge chamber slashing out to an 8.5m diameter using a custom built Galloway drill platform with two booms. To complete the surge shaft the lower access tunnel will be deepened by a 10m bench.

In June 2010 Simard-Beaudry was awarded the CAD 73M (USD 76M) contract for construction of the intake end of the tunnel. Work began on excavating rock for the access tunnel portal (18,200 cu m) in mid-July. This access tunnel was also driven full face, starting mid-September. It is 12m by 9.5m high using two more three-boom Sandvik data drill jumbos down to the main tunnel, with work beginning after Christmas break on the top heading of the upstream end of the main tunnel.

Work has now been completed towards the intake end awaiting warmer weather prior to breaking out into the open cut intake channel, which will require an additional 94,200cu m of rock excavation. Main work as of March 2011 is focused on driving the two top headings full-face rounds towards each other with an anticipated meeting early next year to complete the 5.5km top heading and removal of 538,000 cu m of rock.

Currently Simard-Beaudry is averaging over 100m per week in the top heading in current good rock conditions which makes it one of the fastest advancing hard rock tunnels in the world for this size of heading.

Once the top heading is complete, work will then shift to driving the remaining 10m deep bench 11.5m wide to complete the tunnel and removal of an additional 632,500 cu m of rock by the fall of 2013.

Figure 1, the Romaine reservoir flood area and the hydro projects Figure 2, typical full face top heading drill round with 57mm dia. Holes Drilling full face top heading A view down the tunnel showing the 2.4m diameter venilation system Scaling the face to remove loose rock Figure 3, Romaine 2 general layout and intake tunnel alignment