SCOPE OF WORKS

The construction of a 1500+ lot residential subdivision and 20 hectare lake including:
• 68 civil stage packages
• 2,000,000m3 of bulk earthworks
• Excavation of 20 hectare lake that reaches depths of RL13
• Preloading the majority of the site
• Installation of wick drains under preload to expedite settlement
• 19 kilometres of roadworks
• Major stormwater, sewer and water reticulation works
• Sewerage pump station
• Sewer rising main
• Salinity rising main
• Seven gross pollutant trap units
• Over 3.5 kilometres of revetment walls
• Construction of wetland reserve
• Creation of parklands and parks, including lake front and oceanfront community parks
• Acid sulphate soil treatment and management
• Water quality testing and management
• Dust control and dust levels monitoring
• Relocation of fish and dewatering the existing canal
• Construction of a lock and weir

Newport is a multi-precinct residential and commercial development on the Redcliffe Peninsula. In the first year of construction works, one million cubic metres of earthworks has been completed, with 800,000 cubic metres of fill being removed during the excavation of the new lake.

A number of challenges have arisen throughout the project, with the methodology of how to treat the highly acidic marine clays found throughout the site being one of the most challenging, along with dewatering the existing water body and obtaining a dry, hard floor to run machinery on.

STAGING OF WORKS

Initial
Over a number of years, previous contractors had carried work out on the site, under the master plan of an extensive canal system. As such, there was an existing body of water in the southern corner of the site. An open drain ran through the site from south to north and then turned east and connected back into the existing canals through a tidal flood gate, which released built up water. Preload had also been placed by a previous contractor next to Jabiru Canal.

Early Works
Early works commenced with the goal of delivering the first three stages of works to the client – the sales office site and entry road, along with the two display village stages. This involved removing a section of previously placed fill and replacing it under Level 1 supervision and bringing the stages to finished level with material won from the existing preload stockpiles.

Whilst these works were underway, works began in other areas of the site to prepare for the delivery of the remainder of Precinct A. The existing water body was cleared of all fish and dewatered and topsoil was stripped off the first phase of the future lake.

The existing water body was to be filled with material won from the Phase 1 lake excavation, however, the presence of Acid Sulphate Soils was identified in the sites’ geotechnical assessment. Multiple bunded treatment pads were established in the Precinct A footprint and these were used to place, treat and dry the highly acidic marine clays in 300mm layers. Agricultural lime was used to treat the material and verification testing was carried out to ensure the neutralisation of the marine clays before the next layer was placed.

Civil works have progressed, with six stages completed to date. Bulk earthworks have also moved into Precinct A2 and Precinct B1.

LAKE EXCAVATION

The lake works have been designed to be staged in three separate phases of excavation. The first two phases do not extend to the full ultimate lake design, as some of the material had to be left in place to provide stability during the preloading of the lake edge lots.

The first phase was undertaken to complete the filling and preloading of both Precinct A and Precinct B, as well as making a start on Precinct A2. This process included backfilling the existing waterbody with approximately 300,000 cubic metres of material. The second phase will excavate the remaining majority of the ultimate design and the third phase will trim back the batters to ultimate design after the preloading has been completed.

During the Phase 1 excavation, Shadforths proposed to remove and replace the lake edge to the north instead of preloading it. This methodology saved both time and money for the client. Being below the ground water table, there is a constant requirement to drain the excavation of water. This was achieved by creating a series of open drains to a sump, where the water is pumped out into the sites’ overall drain. Water quality is ensured before any water is released offsite.

CIVIL STAGES

Currently two stages of civil construction have been successfully completed and handed back to the client, with another four stages due to be completed in the coming weeks and a further four to begin early in the new year.

The largest challenge with the civil construction aspect of the project is completing the works in the tight timeframes to satisfy settlements. Despite this, multiple stages have been successfully completed on time and budget.

As current works are in close vicinity to neighbouring properties, control measures to limit disturbance to residents have been implemented. Dust was the biggest focus, with high levels of dust control in the form of water carts and polymers in place. Dust was also monitored using two methods – with dust deposition monitoring over a month long period, along with daily volumetric sampling of airborne micro-particles.

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