Basic HTML Version
66
Current Status of Remedial Works
at Garden Island
A revised table below shows how the bulk earth
works are near final completion on Garden Island.
The carting of the remaining CUF clay and topsoil
has been completed and sufficient clay and topsoil
has now been received on site to complete the
capping works.
As of 30 June 2012, Leed Engineering has completed
the following capping works on Garden Island.
South Island
Works completed to date:
Planting
All areas complete - Total area = 219,500m2
Clay capping x 3 layers, Growing Medium x 3 layers
and Topsoil
All areas complete - Total area = 219,500m2
Subgrade preparation: 100% complete
Hillside Contour Drains: 100% complete
Reno Drop Chute Drains: 100% complete
Sediment Basins 3 & 4: 100% complete
Fencing completed
North Island
Works complete to date:
Clay capping x 3 layers and Growing Medium x 3
Layers 100% complete
Topsoil Spread and shape, Cells 1 to 3 and 8 to 24 –
completed
Cells 4 to 7, topsoil currently on-site ready to spread
and shape in final operation.
Sub-grade preparation on the north island:
100% complete.
Hillside contour drains: 50% complete
Reno Drop chutes 100% complete
Sediment Basins 1 & 2: 100% complete
Fencing completed
Minor ancillary items, roadside drains, completed.
Imported spoil conditioning and planting to be
complete spring 2012.
Landfill Gas Management
WRWMA originally intended to utilise if practical, the
methane gas generated from the domestic waste
degrading in the landfill if in sufficient quantities for it
to be commercially harvested and used to power
electrical generators in the production of green energy.
However, testing has indicated that insufficient
methane gas is being generated by the site.
Early monitoring of existing LFG wells confirmed gas
was present at the site boundaries which is consistent
with the location of deposited waste right up to these
boundaries. Shallow groundwater and sandy soils
limit the potential for LFG migration laterally. Whilst
the early monitoring indicated that there was no
imminent risk of unacceptable LFG impacts, on-going
LFG monitoring has been undertaken across the site.
Surface monitoring has been undertaken (nil result)
and additional monitoring well installed.
Further to the LFG Risk Assessment Report which has
been prepared, surface monitoring has continued to
been undertaken across completed portions of the
landfill cap. Additional surface monitoring was also
undertaken during the 2011-2012 summer periods at
the request of the EPA. This monitoring was
undertaken to determine if there was any season
variations in LFG migration. This additional
monitoring has re-confirmed earlier monitoring results
that the gas is present at the site boundaries.
Monitoring for LFG is continuing under EPA guidelines
at the surface of the cap. Given the age of the waste
and these results of recent monitoring, the LFG
Management system will need to be reviewed in
consultation with EPA. Initial discussions with EPA
have confirmed that they are willing to consider
further assessment and refinement under the LFG
Management Plan for a LFG System to reflect actual
site conditions.
A draft LFG Management Plan is to be developed by
Tonkin in early December 2012 which will consider
the feasibility of passive control (methane oxidation in
the cap) and monitoring in the centre part of the
island. This draft will be discussed with EPA (and
Urban Renewal Authority) and the feedback will
enable Tonkin to produce the formal LFG Management
Plan (LFG MP) to submit to the EPA for approval in
early 2013. The LFG MP will set out the principles
and objectives required by the EPA, and will then
enable a tender to be issued in the first quarter of
2013 for the appropriate LFG infrastructure works.
Activity
Clay
Growing
Medium/Topsoil
Material
On-Site
632,888
tonnes (100%)
970,444 tonnes
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