With the increasing demand for water supply, the Regional Municipality of Halton is undergoing several large-scale infrastructure projects which are required to service growth in the surrounding area. The Zone 3 Interconnecting Water Main was identified in the ‘South Halton Water and Wastewater Master Plan Update’ to facilitate water conveyance between Burlington and Oakville. Among the project’s significant challenges were the CN Rail, Fourteen Mile Creek and Bronte Creek crossings.
Each of these challenges offered unique constraints but none more than the Bronte Creek Valley crossing. Bronte Creek is a 250 m wide valley known for its diverse habitat. It is officially designated as an Environmentally Sensitive Area and an Earth Science Area of Natural Scientific Interest.
Consideration of the Valley’s sensitive environmental features and infrastructure construction method cost led to the decision to support the water main above the Valley floor, utilizing four existing concrete piers of a former highway bridge that was constructed in 1919. In 1948, the highway was realigned and the bridge deck was removed, leaving the four piers to stand freely without a purpose for over 60 years. RVA led a Schedule C Class Environmental Assessment Study, which confirmed that supporting the 900 mm diameter water main on the old piers was the preferred alternative in light of environmental, financial and technical impact comparisons.
After detailed inspection, the condition of the concrete in the piers was analyzed to confirm they were suitable for the proposed use; however, structural and aesthetic improvements were necessary to revitalize the aged structures. The new bridge sits on five pairs of concrete girders which are supported by the four rehabilitated concrete piers and newly constructed east and west abutments. In this way, the abandoned piers were effectively transformed back into a functional piece of infrastructure with minimal disturbance to the Valley’s environmentally sensitive habitat.
Precast parapet walls were also set in place along each side of the water main bridge to recreate the original design. Halton Region is proud of its history and in order to honour that, the design team worked from the original 1918 structure to retain the built heritage significance of the original Dundas Street Bridge.
The award was presented at the Ontario Concrete Awards Banquet on Wednesday, December 4, 2013.