When Does an Old Landfill Cease to be a Landfill?

By Steve Last

There is an easy and glib answer to that question. That answer is: “When it reaches final storage quality”.

OK. You say that's fine. But, what exactly does that mean?

The fact is that nobody (particularly in the UK) has really done enough research to be able to tell you with any certainty.

In the developed nations formal regulation entailing detailed record keeping for landfills (“dumps”, or “tips” as they then were) has rarely been in place for more than 30 years. Until now these sites where almost without exception clearly not fully decomposed let alone harmless.

However, the question will arise increasingly from now on as the first properly designed early landfills that were licensed, and where the owners still have to comply with their “licence”, are becoming a lot cleaner are free from landfill gas, and the material in them is at times considered to be reasonably inert and harmless.

These owners would like to be able to hand back their licences and remove the stigma from the land which comes with it being classified as a landfill.

final storage quality - not yet achieved

This landfill has been extensively developed with retail park units, and yet leachate is present on this face which exceeds the safe discharge quality.

Due to a lack of reliable data and research on what should be defined as Final Storage Quality, little is known about the real time needed to reach final storage quality for a landfill. In addition, even within the regulatory bodies the concept of final storage quality is poorly understood.

A paper presented at the UK Waste2004 conference by O. Hjelmar and J.B. Hansen of DHI Water and Environment, gives us some guidance when it provides us with a case a study. They tell us that their results for the site they studied, indicate that even with a relatively high leachate production rate corresponding to a very abnormally high infiltration of 33 % of the precipitation, final storage quality is hardly achieved in 30 years.

Very low concentrations have been reached for some components while others remain of concern.

So, this explains why so few have given thought to exactly how one might define final storage capacity in terms of each contaminant in an old landfill site leachate.

This leads all old landfill owners to feel that maybe they are being neglected. They don't see why a more sophisticated investigation of the time needed to reach final storage quality for landfills containing MSW residues has not yet been carried out. After all, they would like to have a much better idea for how long their old landfill will continue to be a liability.

The eventual achievement of final storage quality (FSQ) at a landfill, i.e. a situation where active environmental protection measures are no longer necessary and the leachate is acceptable in the surrounding environment, is certainly embodied in the regulations.

When a landfill is closed and the surface is restored these days the owner/operator/licence holder must provide a site closure plan.

However, acceptance of the closure plan by the regulator does not imply anything with regard to the time post-closure when the regulator will cease to regulate the site under its environmental permit or licence.

It is implicitly assumed in most landfill regulations, including the EU Landfill Directive (CEC, 1999) that the owner must hold the licence for an open-ended period – and with it all the responsibilities this entails.

In principle, it is often in the past been established by default that each generation should take care of its own waste and ensure the protection of the environment in their lifetime, but the practical implications of this are rarely addressed. Although, some countries have initiated research in this area, final storage quality (FSQ) or "equilibrium" is seldom defined precisely.

Similarly, the strategies and means to move towards FSQ have not yet been included in existing landfill guidelines and landfill regulations.

One of the main reasons for this state of affairs is probably the scarcity of reliable long-term or even generation-long observations of the development of leachate from controlled landfills, in particular modern landfills. Most of the information available on landfills, leachate generation and management and the potential impacts on the environment caused by landfill leachate relates to landfills containing mostly biodegradable municipal solid waste.

Modern waste management is moving towards the production of increasing proportions of inorganic waste, and towards separate landfilling of predominantly organic waste, e.g. household waste, and predominantly inorganic waste, e.g. residues resulting from municipal solid waste incineration (MSWI).

Only limited documentation is available on the development, over a longer period of time of leachate from landfills containing inorganic waste.

In all cases the regulators and existing owners are far to coy to admit even, it seems, to themselves just how long these liabilities will extend into the future.

The owners of old landfills, who are often several ownerships remote from the original operator, often purchase these lands with inadequate knowledge about just how onerous is the liability they take on.

They need an advocate to plea on their behalf for far more clarity on this issue from lawyers and regulators. This is important, lest many more landfills fall into the hands of unsuspecting landowners, without the skills or resources to manage their landfill properties for the protection of present let alone future generations.