Holsworthy STP Demolition & Remediation

Unicivil was engaged by Enviropacific Services to supervise and execute the full demolition and remediation of the former sewage treatment plant at Holsworthy Barracks. Previously operated by Sydney Water on behalf of the Department of Defence, the site contained a range of large‑scale treatment assets including a clarifier tank, four settlement tanks, four digester tanks, five trickle filters, two humus ponds, and two settling ponds.

The project required the dewatering of 1.4 million litres of infrastructure water, with flows managed through attenuation trenches to ensure controlled, compliant dispersion. Demolition works included the removal of redundant plant structures, vegetation management, fauna habitat management, and bulk excavation to support site remediation. Unicivil also imported, placed, and compacted 70,000 cubic metres of engineered backfill to reinstate ground levels and stabilise the site for future use.

Contaminants encountered included bonded and friable asbestos as well as mercury—particularly within the trickle filter units and asbestos encapsulated in concrete structures. These conditions required tailored methodologies, specialist equipment, and adaptive work sequences to safely manage depth, height, and structural complexity.

Environmental management requirements included flora and fauna protection, sediment controls, and water‑quality management. Through proactive planning and rigorous controls, Unicivil successfully delivered a safe, compliant, and high‑quality outcome on a site with significant operational challenges.