The Twelve Mile Creek Precast Prestressed Segmental Bridges

T he Twelve Mile Creek Bridges, located on Highway 406 linking the City of St. Catherines, Ontario, to the Queen Elizabeth Way, were completed in 1982. For the last two years the bridges have been used for access and hauling fill before being opened to the public this past October. The route of the new highway, which follows the valley through which the creek flows (as shown in Fig. 1), was selected for economy and minimum social and environmental impact. The Twelve Mile Creek originally formed part of the Welland Canal, connecting Lake Erie to Lake Ontario. Today, it is part of a fast flowing tailrace for a generating station. The twisting alignment and profile of the new divided highway at the creek crossing was dictated by an adjacent interchange, site terrain, poor soil conditions, and property constraints. The size, number, and location of piers in the waterway also were restricted and the requirement for a mimimum vertical clearance above the creek had to be met. In addition, the proximity of the adjacent interchange required part of the roadway on the bridge to be flared to accommodate the ramps. Therefore, where the divided highway crosses the creek, two bridges, one for the northbound lanes and the other for the southbound lanes, were necessary to meet the specified requirements.