4.1.3 Initial Assessment – walkover survey (all sites)
To assess ground conditions, a walkover survey of the site and the surrounding area shall be undertaken by a suitable person.
A walkover survey is a direct inspection of the site and the surrounding area carried out in conjunction with the desk study. Indications of any potential hazards should provide a basis for the investigation. A photographic record of the site can help in the reporting of the walkover survey.
Table 2: Potential hazards
| Source of information | Items to be taken into account |
|---|---|
| Topography | • abrupt changes in slope
• valley bottoms or depressions which may be soft or filled • evidence of overburden on slopes • excavations at the base of the slope • signs of landslip, eg tilting trees, posts or walls • signs of subsidence • evidence of imported soil including local surface depressions, tipped material or rubbish, particularly if it is hot or has an odour |
| Soils and rocks | • the basic ground type
• evidence of peat, silt or other highly compressible material at or below the surface • cracking or stickiness of the surface which may indicate a shrinkable sub-soil • sudden changes in conditions, eg clay to chalk or soil to rock |
| Surface water and vegetation | • a high water table indicated, eg by waterlogged ground
• signs of flooding • reeds or water-loving plants • springs, ponds, wells, ditches or streams • the source of any discoloured water |
| Vegetation | • vegetation which may indicate the nature of the soils
• sparse dead or dying vegetation • type and condition of vegetation on land adjoining the site • species, height and condition of the trees • species, height, spread and condition of hedges and scrub on clay • evidence of former trees, hedges or scrub on clay |
| Structural information | • damage to structures, eg cracking in buildings, on or around the site
• other evidence of movement, eg tilting or distortion • any structures or services below ground |
| Local information | • local knowledge of the site, eg mining, refuse tipping or flooding
• local industrial history records indicating past and present uses of the site • place names and street names that may give clues to previous site usage, eg Brickfield Cottage, Water Lane, Tin Shop Hill |
Last updated: 2nd January 2024