Dam 7 South TSF Closure
Glencore engaged ATC Williams to deliver the geotechnical investigation, detailed design and construction support for closure of the Dam 7 South Tailings Storage Facility (TSF) at Ravensworth Operations in the Hunter Valley, New South Wales. The project required an engineered capping platform over an extremely low-strength in-pit coal tailings deposit, enabling future overburden emplacement under the site’s closure strategy.
Dam 7 South served as the primary tailings storage facility for the Ravensworth Coal Handling and Preparation Plant until 2013. Under the approved mine closure plan, the TSF was to be incorporated into a future overburden emplacement area, so the tailings deposit had to provide a stable foundation for ongoing mining operations and final rehabilitation.
The final landform was designed for up to 125 m of overburden above the tailings surface. That called for a carefully engineered foundation that could safely carry heavy mining equipment during construction and remain stable throughout progressive waste emplacement and rehabilitation.
Decades of deposition had created large areas of extremely soft, saturated tailings, particularly within the eastern decant pond and wet areas. Geotechnical investigations identified near-surface shear strengths below 1 kPa in places. These conditions could not support conventional earthmoving equipment, making standard capping approaches unviable.
The scale of the overburden emplacement added further complexity:
The challenge was to build a capping platform that stayed stable throughout construction while letting mine equipment onto the facility at the earliest possible stage. That balance was critical to reducing construction costs, maintaining productivity and supporting Glencore’s closure objectives.
ATC Williams ran an extensive geotechnical investigation, building on more than six years of site characterisation data:
The resulting database divided the facility into strength zones, so closure methodologies could be tailored to local ground conditions rather than applying a single design site-wide.
The platform combined two complementary systems. Conventional capping covered stronger, dry and desiccated areas of the tailings surface. High-strength woven geotextile reinforcement covered weaker decant pond and wet areas, where near-surface shear strengths fell below 1 kPa. This gave safe construction access while optimising earthworks quantities.
Given the ground conditions, construction monitoring was critical. ATC Williams implemented a monitoring program supported by construction TARPs, using fixed survey stations around the facility together with:
The system gave real-time assessment of tailings and capping performance, identifying movement early and allowing rapid mitigation and active intervention to prevent capping failure.
Rather than building the full capping profile before allowing mine equipment access, ATC Williams developed a staged methodology that progressively increased capping thickness while letting larger equipment onto the platform as soon as conditions permitted. We achieved this by:
This reduced construction timeframes, improved efficiency and let Glencore use its existing mining fleet earlier, generating significant cost and productivity benefits.
Construction commenced in 2020 and culminated in a 19 m-thick engineered capping platform capable of supporting mine waste emplacement. Subsequent waste dump lifts were placed over the capped surface, with combined fill thickness exceeding 40 m achieved during controlled construction.
Through geotechnical expertise, innovative design and close construction support, ATC Williams turned a challenging tailings facility into a stable platform for long-term mine rehabilitation.
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