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Strategic Context
Environmental Performance Agreement – Closure Plan
The Western Region Waste Management Authority
(WRWMA) signed an agreement in October 2005 with
the Environment Protection Authority (EPA) as the
licensing body, and the Urban Renewal Authority
(formally the Land Management Corporation) as the
property owner to rehabilitate Garden Island over a
maximum period of eight years. Work on the
rehabilitation of the island was tendered out with the
contract being awarded to Leed Engineering. Leed
Engineering commenced its eight year contract valued at
$12 million soon after to undertake the civil works on
Garden Island. The program of works is based on the
availability of suitable soils, especially clay, and it is
planned that the works program will be significantly less
than the maximum eight years allowed for in the
contract.
Paul Lightbody of Tonkin Consulting has been appointed
as the Superintendent under the Civil Works Contract to
provide independent advice and supervision of the
contract with Leed.
WRWMA has also provided a $12 million financial
guarantee through the Local Government Finance
Authority to complete the works in rehabilitating Garden
Island.
The financial results for WRWMA reflect the cost of the
works to complete the rehabilitation of Garden Island as
per the Environment Performance Agreement and the
sole vision and focus of WRWMA going forward is to
successfully rehabilitate Garden Island to the agreed
standards in the Capping Implementation Plan.
To complete the Capping Implementation Plan Garden
Island requires approximately 1.3 million tonnes of soil,
40% clay and 60% growing medium. The design calls
for a 600mm thick clay cap placed under level 1
supervision and then covered by 750mm of growing
medium and 150mm of topsoil.
The completed cap is then to be planted with grasses
and small vegetation.
Financial Considerations
The Board commissioned KPMG to undertake an
actuarial assessment of all of the liabilities in relation to
the rehabilitation of the former Garden Island landfill
site. This report was presented to the Audit Committee
and the Board in June 2008 and was adopted with a
total estimated liability of $14.3m. This liability has been
factored into the audited financial statements as at 30
June 2008, and has been carried forward in to future
years at its written down value.
Environmental Monitoring
WRWMA retains the responsibility to supervise the
environmental monitoring program in the rehabilitation
plan for Garden Island.
An Environmental Monitoring Plan report was
completed in April 2008 and investigated and appraised
two components, biological and groundwater
contamination. The specialist consultants, Eco
Management Services completed, in association with
Australian Groundwater Technologies and SARDI (South
Australian Research
and Development), the Environmental Monitoring Plan
(EMP) report.
The results of the investigation concluded that ammonia
concentrations are generally low and
well within the range that could be expected for
mangrove sediments in the waterways surrounding the
island. The biological monitoring results whilst
inconclusive showed the low diversity and density in
fauna that are naturally generally occurring
in mangrove sediments in areas similar to
Garden Island.
As the groundwater contamination investigation found
low ammonia concentrations it appears additional
biological assessment investigations are not warranted.
The EMP report has been received by the EPA and
recommended future monitoring should include
the existing groundwater sampling and analysis
program and the analysis of groundwater and
pore-waters at the five locations where ceramic cup
samplers have been installed.
Tonkin has undertaken additional groundwater
monitoring in line with the requirements of the EMP
throughout 2011-2012. Detailed reports have been
submitted to the EPA for their review and WRWMA is
awaiting further guidance from the EPA on future
groundwater monitoring requirements.
The environmental monitoring is continuing on
Garden Island under EPA guidance and in accordance
with the Environmental Monitoring Plan, and agreed
long term monitoring post-closure will be determined to
meet EPA requirements.
Western Region Waste Management Authority Annual Report 2011/2012
Member Councils: Charles Sturt; Holdfast Bay; Port Adelaide Enfield; West Torrens
For the Year Ended 30 June 2012