Hall Contracting was engaged to excavate 13 ha (and over 1,000,000 m3 of material) to create a lake for masterplanned community Brightwater, and fill the surrounding land for development. The site is located within a flood plain adjacent to the Mooloolah River and Mooloolah National Park.
A critical component of the project was the management of acid sulfate soils and groundwater, with 90% of the site below 5m AHD. Due to a high environmental risk factor, the team adopted a variety of management measures and construction methods to mitigate any potential hazards.
Groundwater was monitored daily to identity changes in levels and water chemistry. The team used GPS excavators to construct multicellular compartments, allowing the groundwater to be adjusted when required. A dredge with GPS capabilities was also utilised to keep groundwater above PASS material and reduce the risk of oxidation.
An advanced acid sulfate soil liming strategy was adopted, involving thorough testing, site mapping, lime dosing recording, validation testing and staff training.