The Irvine River Bridge is located on David Street in the historic village of Elora, Ontario.
David Street is a residential collector roadway and one of three links across the Grand River and the Irvine River in Elora. It provides access between downtown Elora, and Wellington Road 7 which is the main north-south bypass around Elora. In addition, it serves as access to/from the Community Centre and Arena and residential areas.
The village of Elora is a significant tourist destination with a number of historic buildings, the Elora Gorge, Elora Quarry Conservation area, the Elora Mill and numerous shops and boutiques.
The bridge is located at the terminus of a hiking trail on top of the Irvine River gorge and is used as a viewing point of the gorge. The gorge itself is used extensively by hikers and canoeists/kayakers.
To date, seven different bridges have been constructed over the 25m deep gorge at this location, the earliest one in 1847. The sixth structure was a two-span reinforced concrete open spandrel arch bridge, constructed in 1921 supported by a single masonry pier approximately 22m high, constructed in 1867 - the year of Canada's Confederation. This was the fourth different bridge supported by this pier, which is the highest masonry pier constructed in Ontario in the 19th century.
The 1921 bridge was a two span reinforced concrete open spandrel arch structure. The overall length and width were 37.6 m and 7.9 m respectively with a roadway width of 5.35 m and a 1.52 m sidewalk on the south side. The single masonry pier is approximately 22 m high and some 6.7 m x 3.1 m at the base and 5.5 m x 1.3 m at the top.
The structure was a provincially significant heritage bridge being a rare surviving example of open spandrel concrete arch construction in Ontario. It is included in the Ontario Heritage Bridge Program's list of heritage structures and is featured on the cover of David Cuming's "Discovering Heritage Bridges on Ontario's Roads".
In addition, the bridge has significant heritage, aesthetic and economic importance to the community in which tourism plays a major role in the local economy.
Because of ongoing severe deterioration of major components, increasingly restrictive posted load limits had been required over the past 30 years. The most recent posted load limit was 10 tonnes. This restricted emergency vehicle access to/from the Community Centre, the Arena, residential areas and downtown as well as tour bus access to/from downtown.
In addition to the structural deficiencies, the kinked roadway alignment at the bridge was substandard and the structure only accommodated a single lane of traffic. Traffic projections indicated that a two-lane facility would be required in the near future.
The principle objective of the project was to replace the bridge with a new structure that would eliminate all of the structural and functional deficiencies of the existing one. At the same time, the aesthetic and historic significance of the structure were key considerations in the development of alternative solutions. In fact, based on strong input from the community and approval agencies, replicating the appearance of the existing bridge was practically a must to obtain EA approval.
A number of site constraints added to the complexity of the design and construction including:
•Existing topography precluded any access to the bottom of the gorge by heavy construction equipment - all material and equipment had to be lowered from above.
•Close proximity of private properties and overhead utilities adjacent to the bridge and road resulted in limited working space for large cranes required to remove the existing structure and to erect the new precast elements.
•Environmental and physical site constraints required that the existing bridge be completely removed from above by sawcutting and lifting out one section at a time while at the same time, protecting the vegetation and the river from dust and debris.
•A regionally significant plant species, Smooth Cliffbrake, was identified on the gorge walls and had to be protected during construction.
•Fishery timing restrictions for in-water works including temporary cofferdams to enable pier restoration.
•Navigation in the Irvine River had to be maintained throughout construction.
Existing utilities on the old bridge included a watermain, sanitary force main, gas main, Bell Canada fibre optic cables and Cable TV. In addition, overhead hydro cables crossed diagonally over the bridge. All of these services had to be maintained during construction and had to be accommodated onto the new structure.
After a detailed evaluation of the pier, MRC concluded that it could be used to support a new wider superstructure and provide a service life of at least 70 years, subject to undertaking a full rehabilitation of the masonry. The original pier, which accommodated a single lane bridge, was modified to support the new two lane structure. The rehabilitation principally included repointing of the masonry and replacement of deteriorated stone. In addition, a cast-in-place extension was constructed on the top of the pier that cantilevered from the sides of the pier to accommodate the new wider superstructure.
For the new superstructure, consideration was initially given to a new concrete spandrel arch design, similar to the existing one. However, two key factors precluded this option:
•While the existing abutments and arch bases are practically at the edges of the gorge, the geotechnical recommendations required that the new structure be founded several metres back necessitating an overall length of 44 m instead of the existing 38 m. This would have resulted in a flatting of the arches, which would not be consistent with the desire to match the original aesthetics. Alternatively, the arches would have had to have been embedded much deeper into the gorge walls resulting in undesirable environmental impacts.
•Modern design loads plus the fact that the new bridge had to be two lanes wide would have required arches with a larger cross sectional area than the existing ones. This would have resulted in a significantly different appearance than existing.
MRC subsequently developed a unique and innovative replica design that features a two span precast side-by-side box girder structure and independent precast spandrel arches beneath the girders. The arches are primarily for aesthetics as they are not used to support the superstructure. However they support key utilities to service properties west of the gorge including a watermain, sanitary sewer and Bell, Hydro and cable ducts.
Each arch rib was precast integrally with the spandrel columns and spandrel arches as one piece that would span from abutment to the rehabilitated pier. The four pieces, two per span, were then lifted into place with cranes located on both sides of the gorge.
Precast beams that replicated the existing transverse floor beams were then erected and connected to the arches with steel angles, plates and anchor bolts. These "floor beams" created a structural frame to stabilize the arches and served to support the various utilities under the bridge.
By supporting the utilities from these beams, the main bridge beams can be replaced in the future without impacting the utilities. Precast corbels were attached to the outside of the arches with hidden steel connections to replicate existing.
Standard 1220 x 800 precast prestressed box girders were fabricated by Prestressed Systems Incorporated in Windsor, Ontario. The girders, which were erected over top of the precast arch / floor beam frames, span from the abutments to the new pier extension and are completely independent from the arches and floor beams with a narrow gap between the two. A cast-in-place reinforced concrete slab and sidewalks were constructed on top of the box girders.
The design also features heritage style concrete railings, sympathetic to the 1921 railings and carriage style luminaries and posts. The railing is designed to meet current Canadian Highway Bridge Design Code requirements for traffic barriers.
Semi-integral abutments were used to eliminate the need for expensive expansion joints which are notoriously high maintenance components on bridges.
The new structure is now the fifth bridge in almost 140 years to be supported by the historic 1867 masonry pier. It successfully addresses all of the functional and structural deficiencies of the previous bridge, while at the same time satisfies local community and provincial interests in heritage preservation and economic value to tourism in the area.
Construction commenced in June 2004 and was completed on time with the road open to traffic in December 2004. The total construction cost was $2.2 M.
Owner: County of Wellington
Engineer: McCormick Rankin Corporation
General Contractor: Hard Rock Construction
Precaster: Prestressed Systems Incorporated, Windsor