Agency tightens policy on 'closed' areas of landfills

Operators of almost 1,000 landfill sites in England and Wales are due to apply for PPC permits over the next three years. The regime will require them to bring their sites in line with EU landfill Directive engineering requirements.

A critical issue for operators is whether their existing waste deposits will fall for regulation under the new-style permits. Operators will have to ensure that there are no "unacceptable" discharges to groundwater from wastes falling under the new permits - irrespective of how long ago the wastes were deposited.

It has been clear for some time that the new permits will cover existing waste deposits if there is no hydrological separation between the two areas. Guidance issued by the Agency last March made it clear that PPC permits will cover closed parts of a site where the site is essentially a single waste body or where separation between the areas is provided by barriers that are likely to break down (ENDS Report 339, pp 41-42 ).

Now, in revised guidance on landfill engineering requirements,¹ the Agency has toughened up its position by arguing that a landfill permit must apply to a particular "site" - and that since this word is not defined in the regulations it should carry its ordinary meaning of "an area of ground". The new guidance, dated 27 November, replaces a previous version dated June 2002.

"A definition of a landfill that seeks to delineate the waste disposal site other than by reference to a line on a plan is not acceptable," says the guidance. In other words, the boundary between two landfill sites has to be a vertical plane.

"This means that an attempt to produce separation through engineering a barrier overlying previously deposited wastes would not be acceptable."

Some waste businesses have reacted with horror to the news, because they had been planning to operate newly engineered cells overlying portions which have already been tipped.

By designing the new phase so as to prevent leachate transmission to earlier deposits, operators had assumed that they would be able to treat the two phases as separate "sites". ENDS is aware of one landfill where engineering work to create a new phase on this basis has already been completed.

The Agency's guidance says that it will be a question of judgement for each case as to whether the necessary degree of separation has been obtained between sites. It says regulators should have regard to issues such as any perimeter fencing, separate accesses, intervening land uses and "generally what can be seen on the ground".

"Shared infrastructure including leachate treatment and gas plants will be relevant in making the judgement as to whether there are separate waste disposal sites."

Where closed areas of a landfill fall under a new PPC permit, the onus will be on the operator to demonstrate that the overall impact of the installation on groundwater will be acceptable. In some cases it may be impossible to issue the permit.

However, often in may be possible to demonstrate through a risk assessment that mitigation measures are available to render the existing discharge "acceptable", and that the ongoing landfill operation itself will not result in additional risk of List I substances entering groundwater or List II substances causing pollution.

Some operators may now elect not to submit PPC applications, and instead prepare their sites for closure. Where applications go ahead, much will depend on the Agency's reading of the eventual risk assessments.

For the time being, it is saying that mitigation measures relating to existing waste deposits should be designed to achieve the required reduction in discharges "as soon as possible" after the permit is issued and in time for the first four-yearly review.

Passive systems such as impermeable capping may be required to provide mitigation over the long term, and there will have to monitoring and evaluation criteria in place.

The guidance also confirms the Agency's position that "geological barriers" made of clay and plastic - as required under the landfill Directive - must extend up the side walls of landfill sites. In areas where the side walls are very steep, this is likely to pose problems. "Many current steep-wall liner systems incorporate single-geosynthetic liners," notes the document.