Mersey Forest Road 3600 Dia Pipe

Project: MERSEY FOREST ROAD 3600 DIA PIPE

Client: SHAW CONTRACTING

Principal: DEPT STATE GROWTH (DSG)

TASK

Following the devastating floods of June 2016 across Northern Tasmania, various sections of the Mersey Forest Road were seriously damaged impeding access to this iconic area for tourists, industry, and recreational users.  At a key stream crossing site in a significant valley a major box culvert structure was washed away – the ferocity of the storm flows were such that the concrete box culvert units were never located downstream.

Department of State Growth (DSG) tendered for a replacement culvert structure, which presented various construction challenges and presented at a significant cost.  Timing and access were key issues to be addressed, along with protection of the environment and the need for time-consuming and difficult in-situ concrete works.

Shaw Contracting and Hudson Civil Products presented an alternative option to use a custom manufactured precast concrete pipe section 3600mm in diameter, believed to be the largest pipe ever manufactured and installed in Tasmania, which was prepared and installed in tight timeframes at a significant cost saving to the Principal over the original solution (a saving of over $200,000).

The innovative use of this custom-built pipe solution allowed the contractor to maximise efficiency in manufacture, crane and truck movements, and manage difficult site access. The subsequent ease of installation presented benefits in time and safety on site over in-situ options.  Similarly the use of the proven modular MASSBLOC system for retaining structures presented advantages to the construction effort and significant savings over other shorter-life and less flexible alternatives.

Working closely with key supplier Hudson Civil Products and designer Frank Brierley of Brierley Consulting Engineers, the Shaw Contracting and Hudson Civil Products team proposed and developed this large pipe solution which met the various key needs of the principal on the project, ensured environmental and safety standards were exceeded over the original proposal, with savings for the client and the project meeting practical completion sooner than expected.

Operating in a high profile and environmentally sensitive area, adjacent to Tasmanian Wilderness World Heritage Area (TWWHA), ongoing road access to this iconic area was provided efficiently, safely and well under budget thanks to the innovation and delivery of the Shaw Contracting / Hudson Civil Products Team through this project.

Installation commenced for the project in April 2017, and major works were completed within six weeks . Shaw Contracting, through careful planning and coordination with Hudson Civil Products for manufacture and supply, completed the total installation for this project, including supporting roadworks and retaining structures, in a fraction of the time of traditional construction methods. The project was completed as noted well under the Principal’s initial budget and exceeds all the objectives of the end user. Total project cost was approximately $750,000.

CHALLENGES & INNOVATION

Based on the lack of access to this iconic area, the Principal was under pressure to re-open the road as soon as possible, and early completion was favoured.

Located close to the TWWHA, low impact and environmentally sensitive solutions were favoured, minimizing work in wet periods or for extended duration where further storm events may have presented potential for erosion, stream damage, and sedimentation.  Additionally minimizing site footprint including storage and staging areas, achieved through the use precast products manufactured off-site and delivered on a “just-in-time” basis, was a key priority.

The team proposed and developed a solution which met some key needs of the principal including:

• Immediate repair works to road to reinstate access as soon as possible, whilst still providing a long term (100 year plus design life) solution
• Undertake these large scale civil works during the latter part of the construction season, with speed of construction and commencement at short notice important
• Ability to undertake construction works continuously during installation with no delays due to periods of concrete cure, etc. to shorten period of works minimizing potential for stream erosion or flooding events to impact works approaching winter, and using modular systems that presented flexibility for options on site as required
• Consideration of work on a remote site and difficulties in access to materials such as fresh concrete, equipment, consumables, etc.
• Significant emphasis on safety and environment during installation and construction activity

OUTCOMES 

Under budget, ahead of time, and a credit to all involved – this iconic drive was re-opened in record time with an innovative and efficient solution provided which is recognised as a major advancement in concrete pipe technology and installation in Tasmania for future applications.