A number of the project's roadworks design and construction elements contained significant technical complexities including a severely constrained road alignment, flat grades, variable soil conditions and a very high water table through parts of the project area.
In addition to the highway, the project was further complicated by the substantial modifications required to the connecting road network that included an extension of Orrong Road, disconnecting William Street from the existing Roe Highway, providing a new link road to connect William Street and Welshpool Road, and providing new bridges across the highway at Brixton Street and Spencer Road.
Road Alignment Constraints
While the project team developed a design that ensured the project works were contained within the road reserve, extensive drainage, the location of existing residential development, a passenger and freight railway, a major gas pipeline and nationally important wetlands provided the project with a number of challengers that required the project team's attention.
In addition, the profile of the road was constrained by existing bridges at Albany Highway and Kenwick Link, and a partly completed railway tunnel under the road alignment near Albany Highway. These items combined to complicate the road designers' task in identifying a suitable horizontal and vertical road alignment, drainage, structures and other project elements that met all standards and addressed Main Roads' stringent SWTC.technical criteria.
In areas where reserve constraints were particularly difficult to accommodate the road designers integrated the requirements of many project elements including approved safety materials, the road surface, shared use path and bridge abutments to ensure that all road users were able to use the highway in a safe an efficient manner.
At the Brixton Street bridge this meant using wire rope barrier instead of clear zones between the road carriageway and the shared use path and road exclusion fencing to enable the shared use path to pass underneath the bridge adjacent to its northern abutment.
As another example additional spans were installed at the Brixton Street bridge to accommodate the freight railway line and the needs of the nationally important Brixton Street wetlands. The additional spans provide appropriate clearance for the freight railway line, improve the appearance of the bridge and reduce the visual impact of the approach embankment, and provide an underpass for fauna wishing to move through the wetlands. without the need to construct a separate structure as was originally proposed. The open aspect provided by the additional spans is likely to prove more successful than a standard box culvert fauna underpass, as was originally proposed.