Research to Date
One of the most significant research reports to date in relation to the Coffs Harbour Bypass was conducted ten years ago by engineering company, Connell Wagner Pty Ltd, and commissioned by the RMS.
In the report, construction options for the bypass are assessed, with large-scale cuttings and tunnels both reviewed as options. The most critical part of the report, however, is the considerable risks noted with large-scale cuttings and the benefits associated with a by- pass constructed of tunnels.
Click here for the full report: Coffs Harbour Bypass Concept Design Report, September 2008
Purpose of Report
This Concept Design Report provides more specific detail of the concept design developed for the bypass proposal, including a synopsis of the key engineering features along the route, including road geometry, bridges and other major structures, provisions for flooding and drainage and preliminary noise mitigation proposals.
- A prominent feature of the horizontal alignment of the bypass proposal is that it passes through two major and two other substantial ridge- lines as it traverses around the Coffs Harbour basin.
- The vertical alignment of the bypass proposal has been developed to provide a best fit through the natural terrain constraints and the resultant cutting depths on these four ridges would be substantial, ranging from 40 metres to 65 metres.
- The excavation of major cuttings on the ridgelines pose risks in the following key areas:
- Depth of excavation of the design and the ongoing maintenance of the cutting
- Large volumes of surplus fill which may be in excess of project requirements
- Potential negative urban design outcomes due to the wide expanse of clearing
- Difficulty in cost estimation/certainty of price
- As an alternative to the excavation of deep cuttings, the feasibility
of tunnels has been considered on three of the four major ridgelines. The rationale for consideration of tunnels instead of the earthworks on these major ridges is that the ridges are quite steep and that the resulting tunnels would be relatively short at less than 500 metres. As such any bypass tunnels would be less likely to require major ventilation and emission control systems.
- With the provision of tunnels it would be possible to substantially low- er the proposed vertical alignment in that vicinity, allowing the bypass to be lowered more sympathetically into the existing terrain either side of the major ridgelines, with consequent aesthetic and acoustic benefits.
RMS holding vital traffic data on dangerous goods
One common question we have had from members of the community, including those who want to see tunnels, is around the number of dangerous goods vehicles passing through the city.
The NSW Government’s Roads and Maritime Service (RMS) currently holds this data from a survey conducted late last year. The data includes the number of heavy vehicles currently using the Pacific Highway, including the number that do not have destinations in Coffs and which would be excluded from using tunnels.
All of Coffs Harbour City Council’s efforts to obtain this data have been rebuffed. The Build the Best Bypass campaign is calling on the information to be released.
– While there is genuine support among the community for the bypass to includes tunnels, there needs to be some transparency on the real impacts tunnels would have on dangerous goods vehicles (that is, trucks that carry explosive or hazardous materials).
– The survey has an accurate count of the number of Class 1 and Class 2.1 dangerous goods vehicles actually using our highway. These are the vehicles that, according to legislation, would not be allowed to use tunnels on the Coffs Harbour bypass.
– Based on anecdotal figures received, the CHCC is confident the number of trucks that would be forced to travel through the city as a result of tunnels would be negligible.
– The bypass is the most significant issue for our community and it’s vital that they are kept informed with all available information that is out there.