The Thousand Islands Bridge - Canadian Crossing
Bridge Rehabilitation 1996-1998

The St. Lawrence River is one of the most important rivers in North America, spanning over 1286 kilometers. In the upper part of the river near the city of Kingston, it is already almost 2 km wide and over the distance of some 64 kilometers has 1,700 islands, hence, this area is known as The Thousand Islands. The St. Lawrence Seaway Authority on the Canadian side and The St. Lawrence Development Corporation on the USA side manage bridges crossing the St. Lawrence River. The Thousand Islands Bridge is made up of two sections: The Canadian Crossing (Canada to Hill Island) and the USA Crossing (Hill Island to the USA). The Thousand Islands Bridge Authority, located in Alexandria on the USA shore, collects the tolls and operates both bridges.

The Canadian crossing is some 1015 meters long and is composed of suspension cable bridge, viaducts, arch and truss bridges. Steinman (now Steinman, Boynton, Gronquist and Birdsall) from New York designed it in 1936 and it was officially opened by President Roosevelt in 1938. This project was the first major repair since that time.

In the fall of 1996, Peter Kiewit Sons Co. Ltd. (KIEWIT) had won the 14 million dollar rehabilitation contract which was prepared by Steinman from New York and Delcan Corporation from Toronto, and tendered by The St. Lawrence Seaway Authority, which allowed for two-year construction. REMISZ was retained to provide all construction engineering design for KIEWIT.

The tender called for a total replacement of the orthotropic steel grid deck, replacement of stringers and railings, and slight widening of bridges. Working conditions on the top of the deck were restricted to one lane during night hours only with a $200.00 penalty for each minute of late opening beyond 6:30 a.m.

Due to the very heavy truck traffic which generates substantial income for the Bridge Authority, closing of the bridges was ruled out and KIEWIT had to work out traffic control schemes and install custom made steel guiderails every night. Also, due to the varying cross sections of the bridges, all construction activities had to be done moving from the Canadian side towards the Hill Island so that traffic will always go from a narrower section to wider.

In order to work day and night shifts, KIEWIT's team (under the direction of Project Manager Mr. Frank Raji) suggested using suspended platforms and a moving gantry frame. This was quite a challenge for the design engineers who, under the supervision of the Project Manager, Wojciech Remisz, prepared a few alternative designs. The designs were then subject to reviews by KIEWIT staff during a pre-construction brainstorming meeting. Later on, the drawings were forwarded to Steinman and Seaway for further engineering input, especially for the suspension bridge spans. As mentioned above, there were no previous similar contracts on this crossing over the past sixty years. Our engineers had to perform structural evaluation of all the structures to account for platform arrangements and gantry frame movement. Therefore, engineers from REMISZ extensively used a 3D model with actual section properties and analyzed all the bridges using the latest ROBOT V6 computer program. Design and Contractor's project engineers had to exercise common sense and good engineering judgment many times, since the platforms and gantry system were unique in their design and operation. Work platforms (approximately 12 x 7.5 m) were made up of steel and Aluma beams with plywood decking, complete with safety handrails. They were pre-assembled on the shore and later transported by barges to the required position and lifted up by winches. They allowed for 1.8 m clearance and were suspended on double channel hangers, which also were to act as compression struts in order to eliminate platform warping due to unequal loading or failure of any one hanger. In addition, platforms were braced using coil rods and cables in the longitudinal and transverse direction, which assured very stable configuration despite 5.5% grade. Since it was reported that wind gusts and turbulence may cause suction between platforms and the underside of the deck, vent holes covered with steel grating were part of the flooring. Thanks to the very careful planning of load balancing by KIEWIT and REMISZ, platforms could be mounted on both sides of the main towers, providing almost 180m of continuous work area, full width of the suspension bridge. This arrangement allowed for different construction works to go concurrently, such as: pre-drilling of holes and preparation for removals in one location, deck replacement at the other, and finishing touch-ups with sidewalk modification at the other end. The custom-built gantry frame could service 36 m of the bridge length, allowing replacement of up to four deck panels per night shift. Since the same gantry had to fit into different deck cross sections and pass under wind bracing, it was co-designed with Applied Fluid Mechanics Inc., Toronto, with hydraulic controls and exchangeable vertical and inclined legs. Its steel casters were moving inside channel rails which were being relocated every few days. Four longitudinal gantry beams allowed working on either side of the roadway from one parking position. As an extra safety procedure, the gantry was being moved to the nearest tower upon completion of the night work.

Steel grating panels were pre-assembled with new galvanized deck stringers and filled with steam cured concrete in a prefab yard. They were being transported to the job site on flat bed trucks, which, on the return trip, were coming with the old removed deck components. Construction joints between new deck panels were filled with fast setting grout, reaching min. 24 MPa in 3 hours, thus allowing opening of the bridge to regular traffic every morning. In practical terms, replacement of the whole deck, railings and sidewalks lasted from May to October 1997, substantially accelerating the completion date.

This project attracted not only the attention of the general public but also very close scrutiny by the Ontario Ministry of Labour. Transportation officials from Kashmir, India, who visited the project site on their cross Canada tour on behalf of the World Health Organization, congratulated REMISZ and KIEWIT.

The practical approach to many difficult construction engineering issues and the excellent co-operation between REMISZ and KIEWIT engineers proved very satisfying to all parties. In the forthcoming years of rehabilitation projects, we should see more partnering arrangements like this one, which saved the Seaway a few million dollars and allowed early completion without any accidents and shortcuts.

Technical Data
spans between abutments: suspension bridge 411 m; viaducts 238 m; arch 118 m; truss 183 m; approach viaduct 65 m
deck replacement 12,100 m²
temporary suspended platforms under: suspension bridge 4,880 m²; viaducts and arch 2,550 m²; truss bridge 2,170 m²
design live load on platforms 2.40 KN/m² (240 kg/m²)
width between stiffening girders/main cables 9,300mm
main cables E=24,000,000 psi, each containing 37 strands, each strand made up of 7 wires; total net cross section of a cable 36.1 in²
hangers between cables and stiffening girder at 25 ft; main span 750 ft. (228.75 m); cable sag 75f ft.
maximum truck load 90,000 lbs. (41 tones) at 150 m between trucks up to a maximum of 130,000 lb. (59 tones) for escorted trucks with special permit

Ó Wojciech Remisz, M.Sc., P.Eng.

January 26, 2001