Extraordinary sites: from quarry to landfill

One of Australia’s largest landfills occupies a former quarry. The site, known as the Boral Western Landfill, has an available airspace totaling more than 15,000,000m3. Since 1999, the facility has offered municipal and commercial waste management services to metropolitan Melbourne. Today, more than 20 percent of Melbourne’s waste is managed there.

Of further note, the landfill also includes a substantial landfill gas (LFG) operation. The decomposing waste creates enough biogas to power 4,000 homes. An on-site plant converts the gas, which is generated in the waste piles and collected through an extensive network of pipes.

Gas collection is further enhanced by the utilisation of geo-synthetic cover systems on closed cells.

The Boral Western Landfill operates in compliance with Victoria EPA regulations and Landfill Best Practice Environ-mental Management (BPEM) guidelines. These regulations are on par with the enhanced environmental protection standards used in many countries for waste management. Chiefly, these regulations are designed to protect groundwater supplies, such as from leachate and to do so, they require the use of geo-synthetic lining systems.

The waste cells at the former quarry are managed largely in the same way as at more traditional landfill sites: the land is parceled into multiple cells, each with its environmental protections and monitoring; and, when a cell is filled, it is capped and new waste is subsequently diverted into the next open cell.

For the construction of the two most recent cells at the site, the operators followed their standard approach in a lining system (noted from bottom-up): clay, geosynthetic clay liner (GCL), high-density polyethylene (HDPE) geomembrane and protection and drainage layers.

NAUE Bentofix® GCLs were selected for the newest lining system.

Bentofix® has been used as a base liner or barrier system component for landfills and leachate ponds around the world. It has also been used routinely for cover systems when waste cells are closed. The GCL is a composite product that features robust geotextile layers on top and bottom and a central core of high-swelling, powdered sodium bentonite. The needle punched nonwoven geotextiles provide excellent frictional characteristics and long-term durability, as well as the flexibility to accommodate normal waste settlement variances, so Bentofix® is appropriate for flat, sloped, or curved soil and cell geometries. The bentonite core provides an exceptional barrier to liquid. It swells in contact with water and, subsequently, becomes too dense for other liquid to flow through.

Importantly, Bentofix® GCLs enable a higher level of environmental protection than just compacted clay, which is why modern landfill barrier designs use significantly less traditional clay, opting instead for thinner, more efficient, more economical and more durable GCL layers.

All of these reasons made Bentofix® an attractive option for the Boral Western Landfill.

In total, 160,000m2 of Bentofix® GCLs were installed by our partner Global Synthetics to secure the future of Melbourne’s waste management system and groundwater.

The Boral Western Landfill continues to evolve, having been a quarry, then an asphalt plant and now a landfill and renew-able energy producer. It does so with state-of-the-art environ-mental controls.