West Branch Ditch Bridge Replacement – Fort Henry National Historic Site of Canada

5P468-23-0070 West Branch Ditch Bridge Replacement – Fort Henry National Historic Site of Canada

REQUIREMENT
The existing FHNHS West Branch Bridge was constructed circa 1832 and serves as the main entry point to the site for visitors and operations. Throughout its lifecycle the structure has undergone changes to the design, character, and operations via rehabilitations. The 18m multi-span timber bridge has reached the end of its service life as determined by comprehensive detailed bridge inspections (CDI) and load limits on the bridge have been imposed.
The intent of this project is to replace the existing end of life structure with a new vehicular bridge capable of providing emergency services access while maintaining cultural heritage. As part of bridge replacement, the existing heritage masonry will require rehabilitation. In addition to this, the approaches
and entire north limits of the Fort Henry Access Road require reconstruction of the pavement surface.

Replacement of the Existing Multi-Span Timber Bridge
The existing 18m multi-span timber bridge will be replaced by a 21m multi-span steel bridge with wood cladding, decking, and railings. The steel uperstructure consists of stringers and diaphragms all of which is situated on elastomeric bearings. In order to limit ground disturbance at the site, the bridge will utilize 1.5m deep reinforced concrete pile caps with 14 micro-piles (< 5.0m long) per pile cap for the foundation, installed behind the existing masonry walls.

Restoration of the Existing Heritage Masonry
Restoration of the existing limestone heritage masonry walls will consist of repointing, stone repair, and stone replacement, and includes the existing ridge abutments, heritage access walls, and masonry swing bridge components. The masonry repair work will be completed following construction of the new
bridge, to address existing defects and any potential new defects caused by the adjacent construction activities.

Reconstruction of the Fort Henry Access Road
Reconstruction of the Fort Henry Access Road is required as part of this project to provide improved access to the new structure. This includes the bridge approaches and entire north limit, approximately 6m in width and 300m in length. The newly placed asphalt will be consistent with the existing asphalt
structure which is to be replaced like-for-like with minor grading of the granular road base as required.

Temporary Access to FHNHS
Due to the scope of construction work anticipated for the project, as well as the seasonal constraints associated with operations at FHNHS, a temporary pre-fabricated bridge will be required across the West Branch Ditch to provide access for pedestrians. The temporary bridge will span the ditch and be situated to the east of the existing bridge on temporary foundations bearing over fill soils over native material. Approaches to the temporary bridge, are required to be Accessibility of Ontario with Disabilities Act (AODA) compliant, and will also be constructed over native soils. The temporary bridge will not
accommodate vehicle traffic into FHNHS, all vehicle access will be through the east entrance into the site.