Making good use of the soil you dig

An extension, a new drive or a landscaping job usually starts with a pile of earth. With a little planning, much of that soil can go back into the garden or the site in good condition.

This page covers how to keep soil healthy while it is dug and stored, how to dig safely, and how to reuse or move it properly in England.

Soil is worth keeping

Defra's code of practice on soils for construction sites calls soil a finite resource. It says topsoil, the most productive layer, can take more than 500 years to form 2cm. One hectare of topsoil can hold up to 5 tonnes of living organisms. Good soil is what gardens, playing fields and green spaces grow in.

The code suggests keeping and using the soil already on site where possible. If soil has to be brought in, it suggests a reputable supplier, and checking where the soil came from and that it suits the job.

Keep topsoil and subsoil apart

The code says mixing topsoil with subsoil lowers the quality of the soil. Keeping them in separate piles keeps both useful. Soil mixed with building waste or contaminated material may need treatment before it can be reused. As a last resort it may go to landfill.

The code suggests marking out each pile clearly. On a larger site, a soil resource plan shows where each kind of soil is stripped from and where it will be stored.

Dig and store it dry

Dry soil handles well. The code suggests stripping soil in the driest conditions possible. After heavy rain, it suggests waiting for at least a full dry day. Light, sandy soil can be moved when wetter than heavy clay. Tracked machines and set routes for dumpers help avoid compacting the ground.

Soil that goes into a pile dry mostly stays dry, and it spreads easily afterwards. Wet soil packs down under its own weight and stays wet in the middle. It then needs drying and cultivating before it is good for planting again. The code says piles of dry topsoil 3 to 4 metres high are common.

Planning a safe dig

The Health and Safety Executive says no ground can be relied on to stand unsupported in all conditions. A cubic metre of soil can weigh more than 1.5 tonnes. So it helps to decide on supports or sloped sides before digging starts.

The HSE suggests keeping vehicles back from the edges, since extra weight can make the sides collapse. Loose soil can also fall from spoil heaps into a trench. Garden and boundary walls often have shallow foundations, which a small trench can undermine. It is also important to find out where buried cables and pipes run before digging.

Reusing soil and moving it on

CL:AIRE's Definition of Waste Code of Practice gives a process for reusing excavated soil on its own site, or moving clean natural soil straight to another site. It can be an alternative to an environmental permit or a waste exemption.

In England, businesses can register a U1 waste exemption to use suitable waste in construction. This includes bringing in soil for landscaping as part of a building project, though not for landscaping or levelling on its own. The waste must not be stored for more than 12 months before use. It must be free of pollutants such as plastic, asbestos and oil. There is a charge for most exemptions.