IN the dark, early morning crowds gathered for a viewing of 563t TBMs on the move. It was the weekend of April 17-20, 2015, two TBMs were lifted out of extraction shaft located just west of Allen Road, and moved to the launch shaft just east of Allen Road to bypass a nearby subway line.

While there was still a number of kilometres left to mine on the tunnel project, spectators outnumbered journalists, excited to see a major milestone on a project that is making history in Toronto.

In Toronto, these are two of four TBMs deployed on 10km of tunnels for the 19km-long Eglinton Crosstown LRT project. It’s the largest expansion in Toronto’s history. Across the country, a number of cities are working toward large infrastructure projects to increase mass transit systems, many of which include an underground component.

In North America, demand for underground construction stems from varying end sectors depending on the location. In British Columbia, hydroelectricity is the largest source of electric power generation. Facilities in the province range from large storage hydro facilities to run-of-river small hydro to micro hydro plants. Increasing mass transit infrastructure in Toronto has required excavation of tunnels for new subway and light rail lines. Cities across the US Midwest are updating their sewer systems to meet consent decrees with the EPA. Deep tunnel networks are often the backbone of these billiondollar programs.

BRITISH COLUMBIA

Hydropower is continually a strong source of demand for the west coast, in fact TAC regional director for British Columbia, Serge Moalli, says, "Hydroelectricity is leading the way in terms of the number of tunnels currently underway."

Innergex Renewable Energy, a developer, owner and operator of run-of-river hydroelectric facilities, wind energy, and solar farms in North America, has a number of hydroelectric facilities (HEF) in development, requiring tunnel work. The Upper Lillooet HEF is an 81.4 MW plant consisting of an approximately 2,500m long inverted D tunnel shaped 6m wide and 5.5m high. The Boulder Creek HEF is 25.3 MW comprising a 2,900m long inverted D shaped tunnel 3.6m wide x 4.5m high to be mainly excavated from the downstream portal. Moalli reports, approximately 2km of that tunnel is to be excavated with a 13 per cent uphill grade. So far, 979m of the Boulder Creek tunnel have been excavated. The Big Silver HEF is 40.6MW project, conveying water through an 1,800m long tunnel with the same dimensions as the Upper Lillooet HEF tunnel.

The BC Hydro and Power Authority, an electric utility in British Columbia is moving forward with Phase I of the Site C project: included in the works are two diversion tunnels approximately 670m and 762 long with a diameter of 12.2m. The project also comprises some drainage tunnels with access adits under the dam. Technical and Financial submissions are currently scheduled for this autumn.

Another BC Hydro project currently under development is the John Hart Generating Station Replacement Hydro project. Located in Campbell River, on Vancouver Island, this nearly USD 1bn project was awarded to InPower BC. The project comprises a 2.1km long power tunnel, underground powerhouse and associated adit tunnels. At the end of July, the 116m long, 6m x 6m diameter service tunnel is complete and controlled blasting and drilling has gone across the 93-metre length of the crown of the powerhouse cavern. There are two adits that feed off the service tunnel, with Adit B now complete and over 260 metres long. Work is just starting on Adit C. Excavation of the main access tunnel 6m wide by 9m high is now about 40 per cent complete. Excavation of the power tunnel is also about to commence.

Hydropower isn’t the only market creating demand for tunnelling across in the province. In Vancouver, a McNally- Aecon JV completed tunnelling on the Port Mann water supply tunnel this summer, and work is on-going for the Evergreen Line rapid transit project.

Moalli reports, Metro Vancouver has more tunnel projects being planned and proposed: the 1.1km-long Second Narrows Water Supply tunnel, the Annacis Main No. 5 Water Tunnel and the Coquitlam Intake No. 2.

CSO in Columbus

In the Midwestern United States work is mostly focused on TBM tunnelling for combined sewer overflows (CSOs). The US Environmental Protection Agency (EPA) identified 746 communities using combined sewer systems (CSS) in 2004- the majority located in the Great Lake and Northeastern regions. Home to the nation’s older communities, these areas were quickly developing in the late 19th century when cities began building municipal sewer systems.

According to data from Timetric, the value add of the sewage infrastructure construction in the US was USD 10.7bn in 2012, continuing to increase each year from USD 10bn in 2008. The market analyst company forecasts there will be even bigger gains, increasing some 23.8 per cent over the next five years.

Water infrastructure construction in the US follows very similarly according to Timetric, and is also expected to make an increase of some 22 per cent from 2012 to 2017.

In 2004, the EPA identified Ohio as having the highest number of communities using a CSS, and its cities are finding tunnelling to be the best solution to relieve their CSOs. Many of the programs comprise more than 20 miles of tunnels and are worth billions of dollars.

For example, the City of Columbus Public Utilities department celebrated the breakthrough of the TBM mining the 4.5-mile long Olentangy Scioto Interceptor Sewer (OSIS) Augmentation Relief Sewer (OARS) sewer tunnel in September 2015. Approximately 170ft below ground, the tunnel will include three relief structures that will divert wet weather combined sewer flow from the OSIS to the OARS tunnel.

A joint venture of Kenny/Obayashi has a USD 264.5M contract for building Structure at Shaft 6, Screen Building over Shaft 2, West Gate Chamber. The overall project is currently scheduled to be completed in late summer 2017.

Money talks

In New York and surrounding reach, the subway and commuter train systems are in dire need of increased capacity. Local and state officials have finally closed the funding gaps in the MTA’s 2015-19 capital plan as of this October. The USD 26.1bn plan includes the second phase, of four, of the Second Avenue Subway.

Another proposed project for the region has significant tunnelling work, Amtrak’s Gateway Tunnel under the Hudson River, but there is no consensus among New York, New Jersey, the federal government and other relevant parties for sharing the costs.

Other projects along the eastern seaboard continue to move forward. The Elizabeth River Tunnels Project Team, comprised of Elizabeth River Crossings OpCo, LLC, SKW Constructors (Skanska, Kiewit and Weeks) and the Virginia Department of Transportation, placed the final element for the new Midtown Tunnel in Virginia this summer. RFQs have recently been issued for DC Water’s largest tunnel in its entire Anacostia River tunnels project.

Western horizon

The SR99 tunnel project to replace the Alaskan Way Viaduct in Seattle has captured headlines not just in the industry but also across the country. At the time of its launch in 2013 it was the world’s largest TBM. After more than a year of down time for repairs, the machine was expected to start tunnelling again in December 2015.

Meanwhile, Seattle is the home of two more large tunnelling projects to expand its light rail system. The University Link project is scheduled to be operational in 2016, and two tunnelling contracts completed 2 miles of twin tunnels. An extension to the University Link project, Northgate Link, is currently underway. Two TBMs are mining 4.5 miles of twin tunnels. The USD 2.1bn project is Sound Transit’s largest to-date. Looking at California, there are several projects with tunnelling components at all stages of construction. San Francisco will be hosting the 2016 WTC and the city’s Central Subway project phase 2 is nearing completion. Work to expand Los Angeles’ Subway and light rail lines includes a number of tunnelling contracts.