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Todhills Landfill Restoration

Todhill is an old landfill site in Bishop Aukland, County Durham. In September 2007 we ceased landfilling operations at this site and began the work to restore it.

Summary
The last load of waste went into Todhills at the end of September 2007.
We then began the capping and restoration of the land. The aim is to return the site to the profile and appearance of what would have been there before the original quarry.

Winter working 2007/2008
Work on the capping and restoration on the site has to stop during the winter. We have continued to deliver the material we need for the capping and restoration during the winter.

We have been stockpiling soils, including bio-compost (CLO) from our Parc facility and green waste compost from our recycling centres for use as the cover on the site.

The site restoration will be complete in November 2008.

The stages of restoration

Capping
Once the site was shut we started to build an engineering cap over the site. This seals the site off – stopping the methane gas coming out and rainwater getting in. The cap will be complete in Spring 2008.

Gas infrastructure
Once the cap is down additional gas collection infrastructure is put into the site.

Protection cap
Once the cap is in place we put a protection cap over it. This is a layer of fine sandy soil that protects the cap from any damage from above.

Sub-soil and top soil
After the protection cap we build up a sub-soil and soil profile. We will use a range of soil products for this to provide the growing surface for plants, this will include the bio-compost (also known as CLO) that is produced by our Parc facility at Thornley in County Durham, green waste compost produced from garden and park clippings and recovered soils produced from our aggregates recycling business. Depending on what is going to be planted the soil profile will range in depth from one metre or up to 1.5 metres.

Seeding and planting
Once the soils are in place the area will be seeded with grass and trees.

Continued management

We will manage the site for the next 30 years – in fact we will manage the site until it is completely stabilised: gas has stopped being produced, decomposition has stopped, leachate has stopped and any settlement has stopped.

Gas extraction
As the waste buried in the landfill starts to decompose it produces methane gas. This is a powerful greenhouse gas and must be collected and burnt off in a flare - this is what happens at Todhills, but not for much longer. We have had plans to install electrical power generators at the site for the last two years – the delay has been waiting for a connection to the national grid, which is now in place. So the flare will be shut off and power generation equipment installed and the gas used to generate power. The flare will only be used in the future if too much gas is received by the power generation equipment.

Leachate management
The site has a leachate collection system installed. The leachate is collected into a holding tank and tankers are used to take it off site for treatment and safe disposal.

Looking up at Todhills from the bottom of the hill, you can see some of the restoration work taking place.