Remediation Works

Background

Historically, Kendall Bay was used for loading and unloading coal and other materials at the adjacent, former Australian Gas Light Company (AGL) Mortlake Gasworks.

In May 2004, the EPA issued a declaration of remediation site under section 21 of the CLM Act for the sediments of Kendall Bay and the Parramatta River in an area 200 metres from the boundary of the former Mortlake Gasworks site. The declared area (and Jemena’s staging site premises for the remediation works in Tennyson Road Mortlake) is shown on the following figure.

Investigations carried out by AGL established that areas of sediments within the Bay had been contaminated and they entered into a voluntary remediation agreement (VRA) with the NSW Environment Protection Authority (EPA) in September 2005.

The VRA committed AGL to further investigations with the view to remediate the sediments within the bay, where necessary. In 2006, Jemena inherited the responsibility to remediate Kendall Bay as a result of various corporate transactions involving AGL. Following the investigations, it has been confirmed by the EPA that the remediation of Kendall Bay is required to address health and environmental risk posed by contamination.

In June 2007, the EPA issued a remediation order to the Maritime Authority of NSW (now known as TfNSW) as the owner of the sediments in Kendall Bay with the purpose of making sure the sediments in Kendall Bay are not disturbed without EPA Approval.

Jemena proposed a Voluntary Management Proposal (VMP) to govern its remediation activities which was accepted by the EPA in August 2017. Jemena is committed to meeting its obligations under the VMP agreed with the EPA.

Within the declared area, two areas of the Bay – the Southern Area and the Northern Area – were identified through technical studies as requiring remediation, referred to as the Southern Remediation Area and Northern Remediation Area as described below:

Southern Remediation Area

  • SA1 – in-situ stabilisation of contaminated sediments by addition of cement and other additives, remove upper layer of treated material for off-site disposal and add clean capping layer
  • SA2 – remove surface stained materials and rubbish and replace with clean crushed rock and clean sand
  • SA3 – remove coke and coal from upper sand layer and spread clean sand, train stormwater flows through mangrove stand
  • SA4 – extend existing sandstone wall to stabilise beach sands, remove coke and coal from upper sand layer and replenish beach sand
  • SA5 – remove coke and coal from upper sand layer and clean layer of sand

Northern Remediation Area

  • NA1 – remove surface stained materials and rubbish, replace with clean crushed rock and clean sand
  • NA2 and NA3 – in-situ stabilisation of contaminated sediments by addition of cement and other additives, remove upper layer of treated material for off-site disposal and add clean capping layer.

 

Project Application to the Department of Planning, Industry & Environment

The planning process involved a project application to the NSW Department of Planning, Industry and Environment (DPI&E) for the remediation works. The project application was originally to be dealt with under Part 3A of the Environmental Planning and Assessment Act 1979.

As a result of various transitional arrangements associated with legislative amendments, on 14 May 2013, Jemena received notification that the Minister for Planning and Infrastructure had signed a Government Order on 4 April 2013 declaring the Kendall Bay Remediation Project to be a State Significant Development (SSD). This took effect in the Government Gazette issued on 12 April 2013 and meant that the project would be dealt with as a Development Application under Part 4 of the Environmental Planning and Assessment Act 1979.

The approval process commenced with the submission of the EIS to the DPI&E. The EIS was placed on public exhibition from 3 - 31 October 2018, so that any person could make a submission on the project.

The Project received DPI&E consent on 31 May 2019, and work commenced in September 2019.  The work was expected to be completed in approximately 15 months – weather and site conditions dependent, however works were completed ahead of schedule in October 2020.

 

Remediation Site Access

The remediation work were conducted from barges positioned in Kendall Bay. The excavated materials were barged to the Jemena facility at 140 Tennyson Road, Mortlake and transported to off-site treatment facilities.

 

Full Scale Works Remediation Works

Insitu stabilisation (ISS) was selected as the main remediation method. ISS is a commonly used, highly successful method on land however there are only a few small scale examples that have been completed in the marine environment. ISS involved mixing of marine cement with the sediment underwater to form a stabilised raft-like structure that will permanently contain the contaminated sediments.

The Kendall Bay Sediment remediation works are understood to be the world’s first full-scale sub-aqueous ISS remediation. Jemena along with our project partner Ventia, had to address many challenges associated with working in a marine environment and fine tuning the cutting edge remedial design.

A custom designed floated cement batch plant was constructed to supply cement to the excavator barge which undertook the stabilisation of the sediment in place below the water. The excavator was fitted with GPS positioning and telemetry to track the successful completion of the works as it progressed.

Full scale remediation works were successfully completed between Sept 2019 and October 2020. The photograph below shows ISS remediation works occurring in the Northern Remediation areas. Several layers of environmental controls were installed prior to commencing the works to protect the marine environment, including silt curtains and sheet piles. 

Remediation occurring in Northern Remediation Area- Breakfast Point Residential Development in background. 

The project was successfully completed in October 2020, completing what is understood to be the world’s first full scale remediation of this kind with over 80,000 worked hours with no Loss Time Injuries, 2 months ahead of schedule, during a worldwide pandemic and with great feedback received from the adjacent community.

Jemena are currently engaging with key stakeholders and providing post completion reports to close out DPI&E Consent Conditions, EPA EPL and VMP and TfNSW (formerly RMS) license. The Jemena project timeline has EPA accredited Site Auditor approval and final stakeholder endorsement scheduled for completion in mid-2021.