Chinderah Bypass Project

Hydraulic Sand Transfer,
Resource Dredging,
Sand Mining,
Civil Works.

Principal:

Roads & Traffic Aurtority NSW

Location:

Tweed Heads, NSW

Chinderah Bypass

Overview of Project

It takes time to adapt to new regulations and methodologies; however, the Chinderah Bypass contract saw Neumann Contractors placed in a situation that required experience that was yet to be gained. No precedence had been set, so a sharp learning curve was essential.

The Chinderah Bypass was a technically complex project that required a combination of best management practices and the conception of new industry practices to achieve the desired end. Modifying the original concept during the construction phase through systematic scientific research and a touch of entrepreneurship has seen a potential environmental nightmare turned around to benefit both the contractor and the community.

Despite the difficulties faced during the project, Neumann Contractors completed the contract to the clients’ requirements on time and within budget.  A success worthy of winning the 1997 National Case Earth Award for demonstrating a commitment to innovation and best practice in the field of environmental in civil construction.

Environmental Impact Studies (EIS) had concluded that increasing the waterway by removing sand would reduce the risk of flooding of adjacent low lying developed areas. Therefore the dredging of the River was part of a longer-term plan for the Chinderah Bypass area.

The dredging operation was to be conducted with strict control as the road traversed over 800m of tidal wetland, crossing three large tidal drains and areas that were considered environmentally sensitive.

To further complicate the situation, prior testing had revealed that existing soils in the road corridor had recorded a significant Acid Sulphate Potential.

Scope of Works

The scope of work included:

  • Importation by dredge of approximately 700,000m3 of fill,
  • Dredging of alluvial sand from the Tweed River directly to the road corridor,
  • Pollution mitigation measures relating to sand pumping operations,
  • Containment and treatment of dredge tailwater to meet EPA standards,
  • Containment and disposal of Acid Sulfate dredge residue.

Challenges

The dredging operation was to be conducted with strict control as the road traversed over 800m of tidal wetland, crossing three large tidal drains and the following areas that were considered environmentally sensitive:

  • Two separate coastal wetlands including an area of mangroves,
  • A coastal dune area,
  • The only remaining section of rain forest in the district that contained a stand of endangered trees (Acronychgia litturalis).

Innovations

There were many environmental challenges on the Chinderah Bypass some of the methods for overcoming these were:

  • During the dredging process the sand and silts separated within the slurry. At the dredge head the sand separates allowing the tailwater containing the acid sulfate silt to run to the lowest point where a secondary pumping system had been established to pump the tailwater and fines to a temporary sedimentation pond and treatment facility.
  • A water treatment facility with a 132,000m3 capacity was constructed on thirty-two hectares of land adjacent to the road’s corridor leased from a sugarcane farmer.
  • The final 75,000m3 of topsoil product was sold on the Gold Coast and won several large supporters amongst the landscape industry.
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Outcome

The Chinderah Bypass project was a great success for all those involved and became a valuable building block in the future treatment and management of acid sulfate soils. Neumann’s treatment of the soil has been the topic of several scientific publications including the National Conference on Acid Sulfate Soil.

Throughout the contract interested visitors to the site included:

  • ASSMAC Committee,
  • Department of Agriculture,
  • Department of Natural Resources,
  • Queensland and NSW Acid Sulfate Committees,
  • Federal Airports Commission,
  • Tweed Shire Council,
  • Gold Coast City Council.

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