Geomembranes – The saviour of the environment?Guest Editorial

Geomembrane use for lining of landfills and waste repositories is effectively mandated in many circumstances in the USA and parts of Europe. The use of geomembranes for lining of waste repositories is also increasing in Australia.

How important is lining of waste repositories for environmental protection and should all potentially hazardous waste sites be lined? There is a wide divergence of opinion on these questions in the technical environmental community. In my years of practice in the waste industry, I have heard opinions range from:

• “Geomembrane liners must be used if you really want to protect the environment”
• “Don’t use geomembranes because they give a false sense of security”.
• “You can’t use geomembranes because no one knows how long they will last”.

How are we in Australia going to sort out a logical and consistent approach to lining systems given the extensive data and literature on geomembrane use, the claims of the salesmen and extreme pressures imposed by mandated use in the USA and Europe? Our regulatory authorities have so far offered very little guidance on this subject. It is in the hands of the geotechnical and environmental technical profession to determine what lining systems are required for landfills and other waste repositing.

In the design of any waste repository we must ask the questions:

1. What segments of the environment need to be protected?
2. What level of impact can be tolerated before it is deemed to be unacceptable?

For most solid waste disposal systems it is the impact of leachate on groundwater and surface water that governs design. Therefore, considerable attention must be given to the design of lining, leachate collection and capping.

How do Geotechnical Engineers decide what level of protection is required to control leachate discharge? If we were in the USA we would adopt minimum design provision under RCRA Subtitle C and D. In Australia, we have very little regulatory guidance on landfill design and it is left to the geotechnical engineers or design engineers to determine what level of protection is necessary. Unfortunately, many arbitrary decisions are made in design of Australian waste repositories and thus we are seeing a wide variation in design standards.

Given the variation in approaches to design, it is likely that regulatory authorities in Australia will ultimately provide guidance for design oflandfills and other waste repositories. If this occurs, there is the risk that the regulatory authorities will adopt a prescriptive and perhaps overly conservative approach to lining design. In this case, sensible design is abandoned for the “cook-book” approach. Anyone who has worked with the US regulatory environment will appreciate how disenchanting “cook-book” engineering can be. Also, if this occurs mining companies, landfill operations and industry are likely to be burdened with unnecessary cost.

As the principal disciplines involved in waste repository design, it is up to the geotechnical engineering and hydrogeological professionals to ensure that design of these systems is not left to the regulatory authorities.

We must be pro-active and ensure that systematic design methods are used to develop logical waste repository designs that are both environmentally effective and economical.

It will be a challenge for the Australian geotechnical community to ensure that we do not lose control of design functions for which we are trained.

The geotechnical conference on hazardous and solid waste organised by the Sydney Group of AGS was an important initiative for the Australian geotechnical profession. For the first time, “geo-environmental” engineers were able to discuss design approaches for waste systems. This initiative should be continued by other AGS Groups.

The AGS should also adopt a pro-active role in the development of procedures for landfill design. A working group should be established within the AGS with the commission to develop systematic design procedures. This will be a challenge for the geotechnical engineering community in the next few years.