Final Storage Quality and How Long Before an Old Landfill Will Cease to be a Landfill?
There is an easy and glib answer to that question. That answer is: “However long it takes to reach final storage quality”.
OK. You say that’s fine. But, what exactly does that mean?
The fact is that nobody 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. The question arises increasingly these days 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 and the material in them is at times considered to be reasonably inter 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.
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 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 explain why so few have given thought to exactly how one might define final storage capacity in term 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.
As we have already stated, the concept behind FSQ is not very well defined. In principle, it refers to the quality which will be attained by the waste in any landfill at some time in the future. The intention of the concept is to define when protective measures and maintenance no longer are necessary to ensure that the leachate produced is fully acceptable in the surrounding environment.
Presumably, within the principle at FSQ there will be no landfill gas present and the atmosphere within the landfill will be fully aerobic.
It is generally assumed that the processes of decomposition which occur within al landfills (e.g. biodegradation, leaching, chemical reactions, mineral changes) and subsequent removal of dissolved components with the leachate by flushing will eventually lead to the attainment of the FSQ.
However, in most nations throughout the globe, with the possible exception of Japan, all the good practise guidance and even the EU Landfill Directive push the site designer and operators into making decisions which extend, not reduce the time needed to reach FSQ. Some are now reporting that they extend the time to FSQ to as much as possibly even a thousand years, maybe more.
The major design requirement which militates against rapid attainment of FSQ is the philosophy in landfill design of preventing or reducing infiltration of water. The lack of flushing with water which this produces directly delays the progression to FSQ.
In effect the result is entombed waste in current sanitary landfills which will inevitably generate biogas and leachate when physical barriers fail in the future, allowing for the first time the intrusion of moisture into the waste mass. This is a contradiction of the precepts of the sustainability concept.
The current regulations for diversion of organic materials away from landfills do not either fully address this, although in principle they should help.
Throughout the landfilling nations, with notably only one or two exceptions, and despite the obvious need for changes, and the importance of reaching FSQ in the shortest possible time, there is generally very little political will to fund and support any research in this area.
Steve Evans is a waste/resource management expert and consultant. Visit his Landfill and Waste Recycling Blog.
Final Storage Quality and How Long Before an Old Landfill Will Cease to be a Landfill? / Author: Steve Evans
