The project at Ti Tree Bio-Energy Facility involves the construction of a leachate liner system on a new "piggyback" landfill cell, integrated with an existing monocell. It includes rehabilitation of a former coal mine while maintaining public operations at the waste facility. Key tasks include bulk earthworks, the installation of various liners and geosynthetic materials, groundwater management systems, and stormwater drainage. The scope also covers the necessary site preparation, excavation, material handling, and coordination of safety and environmental controls. Additionally, the project entails detailed planning and communication with stakeholders throughout the process, with a strong focus on sustainability and compliance with legislative requirements.

Scope of Works:

• Clearing and grubbing of 110,600 m²
• Bulk earthworks (cut and fill) to achieve liner level, excavation, filling, and compaction for Cell 7
• Removal and disposal of existing caps and material as necessary
• Supply and installation of various geosynthetic materials (GCL, HDPE geomembrane, LLDPE geomembrane, geogrids)
• Construction of anchor trenches and connection to existing liners
• Placement of leachate drainage aggregate and separation geotextiles
• Excavation and compaction for the formation of Cell 7 and perimeter, including northern "plug"
• General fill to complete formation and sub-base layers
• Excavation and backfilling of riser trench
• Supply and installation of groundwater underdrain systems
• Design and installation of a leachate pump and ring-main system
• Connection of groundwater collection systems to the existing leachate management system
• Installation of stormwater drainage infrastructure
• Constructing and backfilling of drainage trenches
• Implementation of erosion and sediment control measures
• Environmental protection, site management, and compliance with legislative requirements
• Installation of cover soil, turf, and hydro-mulch

The construction of the Cell 0 piggyback liner system at Reedy Creek Landfill is being carried out in two stages over a non-operational waste cell. Stage 1 focuses on the eastern section, tying into existing Cells 1 and 2 West Wall, while Stage 2 addresses the western section, divided into Zones A and B. All construction is occurring concurrently with the landfill’s operational and maintenance activities.

Scope of Works:

• Site Preparation and Excavation: Remove unsuitable material, conduct leachate investigations, and manage excavated waste.
• Subgrade Preparation: Prepare the subgrade and maintain its integrity until covered.
• Landfill Gas Venting System: Construct the landfill gas venting system with provisions for future Stage 2 connection and coordinate with operators to protect it during construction.
• Base Layer Construction: Construct the base layer with provisions for future Stage 2 connection and ensure protection until covered.
• Bearing Layer Construction: Build the bearing layer, considering Stage 2 integration, and protect it during construction.
• Bund and Trench Construction: Construct perimeter and internal bunds, anchor trenches, and ensure approval for geosynthetics placement.
• Geosynthetics Installation: Install geosynthetics layers with proper connections and integrity and conduct liner integrity surveys.
• Drainage and Leachate Infrastructure: Construct drainage aggregate layers, install leachate infrastructure, and integrate with existing systems.
• Access Infrastructure: Construct access ramps, culverts, and drains with provisions for future stages, and complete topsoil placement and revegetation.
• Documentation and Compliance: Submit progressive As-Built surveys and reports, ensuring compliance with approvals and specifications.

Construction of a new landfill cell and leachate containment system, including integration with two adjacent active landfill cells.

Scope of Works:

• Cut-to-fill over 50,000 m² and placement of 80,000 tonnes of subgrade material.
• Implementation of traffic management plans for public access through the operational landfill, with controlled site entry via the main weighbridge.
• Coordination around live landfill gas extraction networks, requiring excavation permits, safe work procedures, and measures to stabilise batters while working in a biogas environment.
• Strategic earthworks planning to tie into active landfill cells with waste, leachate, and biogas considerations.
• Containment System Installation (Approx. 45,000 m²):
  • Geosynthetic clay liner.
  • 2.0mm HDPE liner.
  • Cushion geotextile.
  • Leachate drainage aggregate.
  • Leachate collection pipework (180mm and 315mm PE pipes) and valves.
  • Integration with the existing leachate collection sump.
  • Temporary edge bunds for future cell connectivity.
  • Clay liner installation to support the geocomposite containment system.
• Perimeter Access Road Construction (440m):
  • Subgrade preparation, cut-to-fill formation, and road base pavement (300mm Type 2.3).
  • Drainage crossings with three 600mm diameter PE pipes.
  • Edge protection, roadside furniture installation, and clean water diversion drain lined with geotextile, topsoil, and turf.
  • Clean and dirty water drainage diversion.

Characteristics of the works undertaken included, but were not limited to:

• Maintaining landfill operational traffic flows during construction
• Staged construction including site traffic and stockpile management
• Excavation, onsite treatment/processing and stockpiling of site won materials
• Material supply and compliance testing of imported earth fill and geomembrane liners
• Construction of new SW5 clean water drain, concrete lined HES basin and new cell perimeter road
• All earthworks and liner works required for cell expansion and cell capping works

Supply and Installation of landscaping, topsoiling, turfing, tree planting and establishment maintenance (13 weeks)