SOUTH WESTERN HIGHWAY THOMPSON HILL SECTION REALIGNMENT
Client: Main Roads WA – South West Region
Thompson Hill, WA
WML was engaged by MRWA-SWR to design the re-alignment of a section of the South Western Highway referred to as the Thompson Hill section. This section of road was identified as a road safety issue due to the reverse curves and overtaking lane combination in a high speed zone.
The scope of work including Preliminary geometric design to determine the route and vertical alignment for the purposes of
- Environmental clearances and Geotechnical investigation
- Geotechnical investigation and design of a 20m deep cutting;
Geotechnical investigation of wet areas and design of subsoil drainage solutions
- Pavement design, including improved subgrade through the cutting area
- Drainage design of the cutting to prevent scour of the cut faces and ensure road user safety on the road
- Detailed geometric design and detailing of intersections, drainage, safety barriers, etc.
- Assistance with providing information for environmental clearing applications
- Pavement marking and signage design
- Detailed design of the temporary bypass required to allow construction work.
This was a particularly complex project to design due to the specific drainage issues encountered with the 20m deep cutting. WML developed a number of specific drainage details unique to this project in consultation with MRWA. The hilly nature of the area also posed difficult drainage issues which had to be addressed with specific scour solution designs for each situation. This in turn required many detailed drainage solutions to be documented individually.
The detailing of the safety barrier interfaces with kerbing and concrete open drains required unique solutions to be developed. The layout of the project posed specific problems to overcome with drafting and presentation. The drafting team worked through the night on a few occasions to meet the delivery deadlines.
The temporary bypass posed significant challenges with constructability of the road and WML developed a staged implementation strategy to allow part construction of the main alignment while operating on the bypass with a switch over to the part constructed main alignment which then allowed demolition of the temporary bypass and completion of the construction work on the main alignment. This required many intricate details and staging drawings.
The project was a challenging one from a design and detailing perspective as detailing requires thinking time, which we were not provided, due to a political promise that was made to get construction started and completed within a certain timeframe. WML overcame this issue by working many long days and nights, which demonstrates our commitment to meeting client needs.