New South Wales Maritime
In 2000, Thiess Services was nominated to Preferred Tenderer status to remediate and redevelop a large and complex contaminated site in Rhodes. Known as the Rhodes Remediation Projects, a Heads of Agreement was signed in May 2001 with the Remediation Agreement signed in December 2001.
This extensive remediation scope included the Homebush Bay Sediment Dioxin Remediation Project, the Lednez (former Union Carbide) Site, and theFormer Allied Feeds Site.
Thiess Services undertook the Homebush Bay remediation concurrently with the Lednez Site from 2001 to 2011, whilst undertaking remediation of the Former Allied Feeds Site from 2005 to 2009.
Sediments in Homebush Bay were contaminated with dioxins as a result of manufacturing and chemical processing operations that once occurred at the Rhodes Peninsula, in conjunction with land reclamation and waste disposal.
The main objective for remediation of the sediments in Homebush Bay was to:
“improve human health and ecological conditions to the extent allowed by budgetary considerations and ensure that the Bay is safe for recreational use.”
The area for sediment excavation covered 7.6 hectares and extended up to 65 metres from an existing seawall over a length of 1680 metres. Within this area, sediment was removed to a depth of 0.5 metres and the excavation reinstated with clean materials from the Lednez Site.
The initial proposed remediation methodology involved a series of Coffer Dams but due to concerns regarding the significant disturbance this process would inflict on the Bay in addition to sediment deposition effects from placing and removing a large quantity of dam material underwater, the alternative method of off-barge dredging was proposed by Thiess Services and accepted by the regulatory authorities and the Client.
The sediment remediation works in the north eastern portion of Homebush Bay were conducted in parallel with the Lednez Site remediation works as an integrated project to prevent potential contaminant from the Lednez Site into the Bay.