Smoky Creek and Guthrie’s Gap Solar and Battery Project

The challenge.

The Smoky Creek and Guthrie’s Gap Solar and Battery Project is one of the largest proposed solar power stations in Australia comprising 600 MW of solar generation capacity with 2400 MWh of battery energy storage, approximately enough to power over 244,000 homes. The site is located approximately 42km northwest of Biloela, central Queensland.

The site is characterised by highly variable geomorphology, including floodplains, alluvial terraces, colluvial slope wash and areas of shallow weathered rock. Initial site observations identified widespread reactive clays, gilgai formations and surface water features, presenting geotechnical challenges for the design and construction of solar tracker foundations, associated earthworks and long-term ground performance.

The approach.

FSG Geotechnics and Foundations was engaged to deliver two phases of geotechnical assessment to support project feasibility and early design. Phase 1 comprised a preliminary geotechnical desktop assessment and site walkover to establish a regional geological and geomorphological model identifying key geotechnical risks to the project. Phase 2 involved a comprehensive site investigation at nearly 200 locations including boreholes, test pits, pavement dips, specialist laboratory testing and electrical resistivity surveys across the proposed development area.

FSG utilised local contractors and coordinated the investigation with several stakeholders including the developer, cultural heritage advisors and local landholders. The results of the investigation were used to characterise subsurface conditions across the site into defined zones to allow specific recommendations for solar tracker pile design and provide preliminary geotechnical parameters and constructability guidance for design and construction of solar tracker foundations, access roads, substations and battery energy storage infrastructure.

The outcome.

The investigation provided Edify with an understanding of site conditions to inform project planning, design development and risk management. Areas of variable ground behaviour, potential pile refusal and heightened shrink swell potential were identified, allowing these risks to be addressed early in the design process. Zone specific geotechnical recommendations for shallow and piled footing design, site classification and shrink swell behaviour, temporary batter slopes, pavements and subgrade preparation supported foundation design, earthworks planning and pavement design across the site. This reduces uncertainty and enabled informed decision making for the delivery of large scale solar and battery infrastructure in a complex geotechnical environment.