Frequently Asked Question - Are soil improvement techniques treatment activities and do they require a permit?

Are soil improvement techniques treatment activities and do they require a permit?

Construction activities carried out on uncontaminated soils solely for the purpose of improving geotechnical properties are not generally regarded as waste treatment operations and do not require a permit. These include:

• Lime/Cement Stabilisation: Stabilisation of soils with high moisture content to improve their compaction characteristics by mixing with lime-cement or cement only. If the lime is considered to be a waste material, or if the treatment is required specifically to recover a discarded material this may need to be reconsidered.
• Vibro Compaction: Vibratory techniques to improve the bearing capacity of weak soils (often made ground).
  These techniques use a vibratory poker that is lowered into the ground under its own weight. In most cases, stone is introduced into the ground either down the centre of the poker or into the hole when the poker is removed. The poker applies further compactive effort until adequate resistance is achieved. The combined affects of the vibration and the introduction of the stone result in an increase in the density of the soil and a consequent improvement in bearing capacity. This activity must be carried out in accordance with requirements of the EA published guidance "Piling and Penetrative Ground Improvement Methods on Land Affected by contamination: Guidance on Pollution Prevention. NC/99/73".
• Dynamic compaction: This technique involves dropping a heavy weight from considerable height to compact weak soils (often made ground). A series of ‘footprints’ are formed which are subsequently filled with granular fill. This may either be a primary aggregate or a re-cycled material. Dynamic compaction is not a waste treatment activity (unless it is being done on a landfill site for example) and any risk to controlled waters must be addressed during the assessment of the Planning permission.
• Surcharging: This technique involves placing soils in a mound to compress weak soils thus reducing future settlement potential. If the material used for the surcharging is generated and then reused (in line with the CoP) on the site it should not require a WFD permit or Exemption. However if the material is to be imported or exported from the site after use there may be requirements for waste permitting.
• Piling: There are various forms of piling which are used to transfer structural loads through weak soils to more competent materials at depth. These range from driven displacement, bored and continuous flight auger bored piles. A WFD permit will not be required for this activity. The piling activity must be carried out in accordance with requirements of the EA published guidance "Piling and Penetrative ground Improvement Methods on Land Affected by contamination: Guidance on Pollution Prevention. NC/99/73".
• Soil Reinforcement: This technique involves the introduction of geo-textiles or ‘geogrids’ to layers of soil (often made ground) to improve load distribution and bearing capacity. This technique is also often applied to improve the slope stability of soils to facilitate construction of steep sided embankments. A variation, to improve the stability of cuttings, is the use of ‘soil nailing’ whereby rods are ‘fired’ into the ground at regular intervals.