The Coomera Connector is a 45 kilometre north-south transport corridor connecting the Logan Motorway and Pacific Motorway interchange at Loganholme and Nerang-Broadbeach Road in Nerang.

The Department of Transport and Main Roads (DTMR) identified the 16 kilometre section between Coomera and Nerang (referred to as Stage One Coomera to Nerang) as having the highest demand for providing additional capacity between Loganholme and Nerang.

The preferred arrangement has been identified as a new urban high-speed motorway having grade-separated interchanges which will provide an alternate route to the M1 for both the Coomera and Nerang River crossings. Stage One will be delivered in three construction packages.

Stage One North includes a four kilometre section from Shipper Drive to Helensvale Road. Construction commenced in early 2023 and is slated for completion by 2025.

The BG&E and WSP JV (WBJV) was engaged by Acciona Georgiou (AGJV) to carry out the successful tender design and subsequent detailed design for the Coomera Connector Stage One North.

BG&E’s QLD Bridge team were the lead designers for bridges and structures on this project.

Scope included

• Three dual carriageway road bridges Coomera Overflow Bridge, Coomera River Bridge and Helensvale Road Bridge.
• All bridges are future-proofed to six lanes to minimise construction impacts for nearby residents during future upgrades.
• One pedestrian bridge over Helensvale Road.
• Major sign and shade structures.
• RC cantilever and contiguous pile retaining walls.
• Noise walls (freestanding, mounted on barriers and on bridges).
• Existing bridge abutment modification.
• Construction support.

The bridges on this project all utilise precast Super-T girders ranging from 1225 millimetres deep to 1825 millimetres deep with over 600 precast girders required for the project. The construction corridor is only 2.5 metres wider than the total carriageway width at most locations along the Coomera River Bridge, which also runs parallel to the south coast QR railway line. Due to the tight construction corridor, Coomera River, adjacent residents, QR railway and deep soft ground – the design and construction methodology posed significant design challenges.

The main bridge over the Coomera River and Saltwater Creek consisted of 30 spans with a total bridge length of 885.5 metres, comprising spans ranging from 25 metres to 37 metres. The bridge comprised 1225, 1525 and 1825 deep Super-T girders with two spans being made continuous for live load to avoid major PUP services. The bridge is approximately 30 – 35 metres wide, carrying three design lanes in each direction while the southbound carriageway also carries a four metre wide shared path which includes a connection to the new Hope Island Railway Station. Due to the large width of the bridge and narrow corridor, a longitudinal joint separates the two carriageways by a 20 millimetre gap.

The Coomera Overflow Bridge and Coomera River Bridge sites consist of up to 20 metres of soft ground – which presented major challenges for the bridge design. The key challenges were designing for up to 10 metres of liquefaction, five to seven metres of scour during flooding, railway collision loads and lateral pile movements due to soft soil settlements at the abutments.

Geotechnical ground improvements were included at the bridge abutments on the north abutment of the Coomera River Bridge and both abutments of the Coomera Overflow Bridge, which consisted of rigid inclusions.

Long term abutment movements and locked in additional movements and stresses on the bridge foundations had to be assessed and included in the design which was carried out by the Structural and Geotechnical design teams collaboratively during the design. Similar design checks during construction have also been undertaken by the WBJV to assist the construction team and to ensure no adverse load conditions are imparted onto the design during crane operations for girder installations.

Materials Scope

BG&E was engaged to provide a holistic durability report for Coomera Connector Stage One North – Shipper Drive to Helensvale Road.

The report was constructed by assessing geological, hydrological, and atmospheric data, and providing durability recommendations to the specific site conditions for concrete, steel, and polymer technology. Inaccessible items were designed to withstand 100 years without maintenance and accessible assets were designed to minimise disruptions to serviceability and utilisation, recommending durable solutions and specific characteristics to fit the project location and intended use.

The durability report was completed in November 2022.