There are many thousands of closed landfills in the UK. In general all domestic waste landfills filled before the 1950s now exert little or no environmental impact as they contained a low organic content from the start. They did not ever become significantly methanogenic (methane producing), and were:
- normally shallow (2 to 5 metres deep),
- contained a great deal of ash and clinker from home fires,
- were rarely capped with a substantial thickness of soil materials,
- and they were as a result, sufficiently permeable to be “flushed” by percolating rainwater.
The leachate such sites produced was dissipated by dilution and dispersion, without any really structured decisions being made at all about the impact this might cause on the natural environment Fortunately, this did not matter greatly as the effects were short lived and localised.
The leachates they produce today will have slightly elevated salinity, metals, potash etc, but ammonia levels will be very close to background concentrations. Many have been developed as car parks, playing fields etc, and even built-upon with no ill effects, as long as suitable foundations to limit settlement, have been installed, and any soils contaminants are sufficiently deeply buried not to affect topsoil quality.
The result in these landfills is a well composted waste residue, which gives no odour if excavated, and even uncapped “tips” can now support substantial stands of trees.
The presence of these old landfills has only been systematically mapped since Local Authority contaminated landfill registers were introduced in the late 1990’s. The UK Environment Agency’s “not in my backyard” web site, shows some of the most recently closed landfill sites, alongside active sites.
How Closed Landfills Changed
During the 1960s, transport links improved, the sites each became larger, plastics entered the waste stream, and with improved affluence, waste tonnages rose. Home fire generated ash and clinker diminished progressively, alongside the cessation of home burning of organic and calorific value materials. Gas or oil fired central heating was installed in homes across the nation, and Clean Air Act regulated restraints on home burning, became the norm by the mid 1970s.
Without most of us realising it at all, we had created all the conditions necessary for today’s monster landfill “super” sites, with their ensuing need for containment and all their other emissions problems.
These landfills were built before there was any national regulation, and were not lined. For more information on landfill lining see our landfill lining development section.