Remediation Project to Restore Nature Reserve via Petroleum Australia
March 2022 – Since undergoing cessation of production activities in 2014, the Chevron-operated facilities at Thevenard Island, Western Australia have been in a care and maintenance phase, with the site subject to campaign inspections and environmental monitoring. Onshore well plug and abandonment activities were completed in 2019, followed by some early-phase onshore decommissioning activities and waste removal.
In late 2020, Liberty Industrial was awarded the onshore decommissioning and remediation project through a competitive tender process – a project that intends to remove all asset infrastructure from the island, and restore those areas to a condition similar to and compatible with the adjacent nature reserve.
Most of the work completed on the island to date has been the removal of the three oil storage tanks and associated infrastructure, while the earthworks, land forming, and jetty removal work are set to begin this year.
Remediation works will follow on from the demolition phase and will involve the bioremediation of hydrocarbon impacted soils, the extent of which has been verified through the results of prior site investigations.
These soils will be excavated, blended with stabilised sand and then bioremediated on the island, after which the amended soil mixture will be placed into an excavated cell on site, below a depth of 1.5 metres from the final landform surface.
The final grade, or top 1.5-metre layer of the soil, must be free from any foreign materials, so all sands are being screened and all foreign inert materials (such as blue metal) removed.
This approach to remediation has been endorsed by the relevant regulators and provides a way to return the site to a state compatible with the nature reserve while being protective of environmental receptors and human health.