This 2005 photo shows the southbound / eastbound lanes approaching the Montreal portal of the Louis-Hippolyte Lafontaine Tunnel (A-25). (Photo by Douglas Kerr.)
THE FIFTH CROSSING TO THE SOUTH SHORE: In anticipation of growing congestion between Montreal and the South Shore, and even as construction was well underway on the Champlain Bridge (A-10, A-15, and A-20), the Quebec government announced plans in 1960 for a new crossing further downstream along the St. Lawrence River from downtown Montreal. The proposed crossing, which was to be built and operated by the province, was to be part of a province-wide autoroute network being developed under the government of Premier Jean Lesage.
The crossing was to be the last link in the Trans-Canada Highway, and as part of the continent-wide link was eligible for 90% federal financing with Quebec funding the remaining 10%. It was to be completed in time for Expo 67 to celebrate Canada's centennial; the world's fair was awarded to Montreal in 1962 after Moscow backed out of the competition.
Two alternatives were considered before engineers decided on a final alternative. A suspension bridge alternative was developed, but concerns were raised about the high cost, potential interference with nearby port operations, and the need for a serviceable crossing in the event of a nuclear attack. (However, the post-construction costs for operating and maintaining a bridge were found similar to that of a tunnel.) A dual deep-bore tunnel (with the same six-lane capacity) through rock was considered impractical. Engineers finally decided on an immersed tube tunnel (ITT) design similar to one used for the construction of the George Massey (Deas Island) Tunnel, which was built in Vancouver in the late 1950's.
In the fall of 1962, the Ministère de la Voirie du Québec (MVQ) retained three firms (Brett & Qulett, Lalonde et Valois, and Per Hall Associates) to assume planning, engineering, and project management responsibilities. Work commenced in April 1963, although right-of-way condemnation for the A-25 northern approach in Montreal had begun two years earlier.
The northern (western) portal in Montreal (Long Point) was to connect to A-25 (Lafontaine Autoroute), on which right-of-way condemnations already had been underway for two years. The contract included construction of a high-speed directional interchange between A-25 and a future extension of the Ville Marie Autoroute (current EXIT 4 on A-25).
The southern (eastern) approach between the Ile Charron portal and Boucherville was comprised of a 484-meter (1,500-foot)-long causeway, an interchange serving the provincial parks on Ile Charon (EXIT 1 on A-25), and an interchange with A-20 / QC 132 (former A-430) at the base of the causeway.
TUNNEL DESIGN: The ITT design had two vehicular tubes each with three 12-foot-wide lanes; a service tube for tunnel employees and emergency personnel was situated between the vehicular tubes. The tunnel was built 90 feet below the low water mark of the St. Lawrence River and could accommodate a 2,400-foot-wide shipping channel. Each of the tunnel sections measured 116 meters (360 feet) long, 38.5 meters (119.5 feet) wide, and 8.1 meters (25 feet) high, and weighed about 32,000 tons. The placement of the casting basin reduced the length of the ITT sections to 813 meters (2,520 feet), and construction time and cost savings were realized.
To provide space for the three-lane tubes, new concepts were developed for the design and construction of the tubes. Transverse pre-stressing of the roof and bottom slabs was required to resist the hydrostatic pressure for the tunnel section to be sunk into place while keeping the weight of the section within limits to provide for buoyancy to float the section into place. To counterbalance the various forces, temporary ties were installed along the bottom and roof slabs. Once the tunnel sections were lowered into place, these temporary ties were removed.
A modified semi-traverse ventilation system connected to ventilation buildings situated at the quarter-points of the 1,471-meter (4,561-foot)-long tunnel. The northern ventilation tower was built on land, while the southern tower was built on the earthen dyke extending from the casting basin on Ile Charron. Fresh air is distributed through a central duct between the vehicular lanes; vitiated air is pushed out directly from the traffic lanes by 16 fans in the ventilation buildings (eight for fresh air and eight for exhaust) ranging from 125 to 200 horsepower. The ventilation system was tested in a 32-meter (100-foot)-long scale model.
BUILDING THE TUNNEL: Before the ITT sections could be placed beneath the St. Lawrence River, a buoyant concrete caisson for the southern (eastern) approach and ventilation building was prefabricated off-site, floated into place, and sunk into position just off the shore of Ile Charron. A casting basin to protect the caisson was built behind an earthen dyke for the fabrication of the tunnel sections and ultimately the southern approach.
Work on the casting basin, which extended north (west) from Ile Charron, was completed in May 1965. Workers then dug the trench to accommodate the seven immersed tube tunnel (ITT) sections that would comprise the main underwater tunnel. The Ile Charron casting basin resembled one large floating assembly line. When each section arrived, it was placed at the end of the dock where the "assembly line" began. Assembly teams placed the concrete roadway deck and steel reinforcement bars inside each ITT section. The concrete and steel were placed carefully so as not to capsize the ITT section that was being floated. When each section was finished, it was floated out by barge to the trench in the St. Lawrence River, and the next section was pushed up the "assembly line." The first ITT section was sunk into the St. Lawrence River in September 1965; the last section was immersed April 1966.
The Lafontaine Tunnel and its approaches were opened to traffic on schedule on March 11, 1967 - just 47 days prior to the opening of Expo 67 - at a cost of C$75 million. To this day, the Lafontaine Tunnel remains the longest underwater vehicular tunnel in Canada. Conceived originally as a link in A-20 before the Ville Marie Autoroute extension was shelved indefinitely, the bridge-tunnel complex has carried the A-25 designation since it opened. It was named in honor of Louis-Hippolyte Lafontaine, who was the first Canadian to become prime minister of Lower Canada.
These 1970 photos show the eastbound (Montreal) and westbound (Ile Charon) portals of the Lafontaine Tunnel (A-25). (Photos from the Archives de Montréal and the Bibliothèque et Archives Nationales du Québec.)
THE TUNNEL TODAY: According to the Ministère des Transports du Québec (MTQ), which operates and performs capital projects on the tunnel and its approaches, the Lafontaine Tunnel carries approximately 130,000 vehicles per day (AADT). Trucks are restricted to the center travel lane because of lower clearances on the left and right lanes.
In the early 2000's, the MTQ upgraded the electrical system serving the ventilation, lighting, surveillance, and fire protection systems. From 2006 to 2008, construction crews carried out a major rehabilitation of the Ile Charron causeway approach that added a fourth southbound (eastbound) lane to A-25 for exiting traffic. In the spring and summer of 2009, the Lafontaine Tunnel was closed on the weekends so that workers could repair concrete supports for the large basins positioned at the tunnel entrances; they also made additional repairs to the ventilation and electrical systems. The MTQ expects additional weekend closures through 2014 to replace asphalt and repave the roadways.
ADDRESSING TUNNEL SAFETY: Following a smoky vehicle fire in the Ville Marie Tunnel in 2001, firefighters addressed concern to the MTQ that the existing ventilation system was inadequate. The MTQ then sought the advice of National Research Council Canada to evaluate tunnel ventilation. Through a series of twice-yearly overnight tests in which the Lafontaine Tunnel is closed to traffic - these tests still are being conducted - researchers are learning how best to control ventilation fans in case of a fire.
These 2005 photos shows the southbound / eastbound lanes of the Louis-Hippolyte Lafontaine Tunnel (A-25) exiting the Ile Charron portal (left photo) and at EXIT 1 on A-25 (Ile Charron / Iles de Bouchervile, right photo). (Photos by Douglas Kerr.)
Construction started: Opened to traffic: Number of tubes: Number of traffic lanes: Length between portals (Montreal to Ile Charon): Length of causeway (Ile Charon to Boucherville): Operating headroom of tunnel: Roadway width: Maximum depth, mean high water to roadway: Length of each immersed tunnel section: Width of each immersed tunnel section: Height of each immersed tunnel section: Weight of each immersed tunnel section: Number of immersed tunnel sections: Structural steel used in construction: Concrete used in construction: Supply and exhaust fans: Cost of original structure:
A THIRD TUBE: Given the pending completion of the A-25 extension in October 2011 and the A-720 extension sometime in the late 2010's, it may be time to consider adding a third tube to the Lafontaine Tunnel and expanding the approaches to cope with additional congestion. However, extending A-640 north of Greater Montreal - as proposed by the Nicolet Commission - may be a more optimal solution as the northern bypass (along with the A-30 southern beltway) would remove most through traffic from Montreal Island.
SOURCES: "Bridge-Tunnel Link Is Opened in Canada," The New York Times (3/13/1967); "Prefabricated Sections in the Construction of Underwater Tunnels," Hydrotechnical Construction (March 1969); Place Versailles Inc. v. Minister of Justice of Quebec,  2 S.C.R. 1118; Supreme Court of Canada (10/05/1976); Immersed Tunnel Techniques, Institution of Civil Engineers (1990); "Louis-Hippolyte Lafontaine Bridge-Tunnel" by RSW (Electrical Consultant), Canadian Consulting Engineer (December 2005); "Ile Charron Bridge To Get an Extra Lane," The Montreal Gazette (4/08/2006); "Montreal Tunnels Undergo Safety Inspections," Journal of Commerce (9/06/2006); "Breathing Easier in Montreal Tunnels," National Research Council Canada (February 2008); "Lafontaine Tunnel To Be Semi-Closed for Six Weekends," CTV News (4/14/2009); "Lafontaine Tunnel Closed for the Weekend," CTV News (4/17/2009); Canam Group; International Tunneling and Underground Space Association; Ministère des Transports du Québec; National Research Council Canada; Félix-Mathieu Bégin; M.J. Pierre Fortin.
A-25 shield by Wikipedia. Lightpost photos by Douglas Kerr.