Pacific Highway Upgrade Woolgoolga
to Ballina (W2B): Wave 4 Early Works

• 70,000m3 foundation treatment using R31 spec drainage rock.
• 600,000m3 imported earth fill material.
• 320,000m3 vertical wick drains.
• Works undertaken in Endangered Ecological Communities (EEC).
• Works undertaken in a flood plain with significant Acid Sulphate Soils (ASS).
• Creek re-alignment.
• Temporary crossings.
• Property adjustments.
• Clearing and grubbing.
• Geotechnical instrumentation.
• High strength geosynthetic reinforcement.

Soft Soils

Foundations for the Wave 4 project consisted of 600-millimetre drainage rock (including wick and bridging rock), followed by the installation of wick drains and geotechnical instrumentation to monitor soil conditions.

Around 330,000 cubic metres of earth fill was placed as the surcharge material within high strength geosynthetic reinforcement interwoven at specific locations and levels to prevents slips or embankment failures. Geotechnical monitoring equipment installed and subsequently managed, including 90 settlement plates, 12 vibrating wire piezometers, 10 standpipe piezometers, 21 inclinometers, 6 hydro-static profile gauges and 5 magnetic extensometers.

Erosion and Sediment Control

Due to the significant sensitivities of the projects work area, as well as the significant water management required, erosion and sediment control was vitally important.

The project team used industry best practice controls including the placement of the top-class soil binder, Vital Bon-Matt HR instead of bitumen emulsion adjacent to highly sensitive creeks and drains in threatened fish habitats.

Due to the final design gradient of an abutment, soil binders were considered inefficient in stabilising the batters nearby to an OPP waterway.

The project team devised a system of installing geofabric and pinning it to the batter using takes to ensure the batter could be stabilised without impacts on the fish habitat below. Based on its success, this system was used on six batters throughout the project.

• The Works diverted an OPP waterway and constructed a vegetated drainage channel to remove project works from OPP habitat zones. The project also installed three pre-cast concrete bridges, designed for construction loads of fully loaded 657 scrapers and 777 dump trucks to mitigate ongoing site access issues within the threatened fish habitats. This allowed construction to continue, reduced the impacts on fish habitat area and the timeframe that creeks needed to be bunded.
• The use of more than five kilometres of impermeable sediment fencing and infiltration bays to manage site water via plastic and rock lined batter chutes.
• A W2B project first in the use of Vital Bon-Matt HR as a soil binder for abutments instead of bitumen emulsion due to the abutments being near threatened fish habitats. This allowed embankments to be stabilised with minimal impact to the highly sensitive creeks and drains surrounding them.
• Amendment to stabilisation measures on some abutment batters which were too step to enable successful soil binder application. To overcome this, geofabric was installed and pinned to the batter with stakes to successfully stabilise the area, preventing degradation of the creek below.