12 Field reconnaissance

A thorough visual examination should be made of the site to confirm, amplify and supplement the available findings of the desk study. All the information compiled about the site should be reviewed thoroughly before the field reconnaissance is undertaken, allowing a greater understanding of the significance of the features subsequently observed within and around the site. The reconnaissance should encompass the areas surrounding the site; the extent and coverage of these off-site observations is a matter of judgement.

NOTE 1 Annex E gives a summary of the procedure for field reconnaissance and the main points to be routinely considered. This procedure might need to be extended or modified, depending upon the particular circumstances of the site.

The following preparations should be made before carrying out field reconnaissance:

  • a) a site plan, district maps or charts, and geological maps and aerial photographs and satellite imagery should be obtained as available;
  • b) permission to gain access should be obtained from both owner and occupier as necessary; and
  • c) where evidence is lacking at the site or some verification is needed on a particular matter, for example, flood levels or details of changes in site levels, reference should be made to sources of local information (see Annex C).

A health and safety risk assessment should be carried out before the visit. This assessment should be based on the results of the desk study and should be updated as the reconnaissance proceeds to take account of what is seen on site. If the presence of potentially hazardous substances is suspected (e.g. contamination), the risk assessment should be reviewed and appropriate control measures should be taken, which might necessitate the use of personal protective equipment. Specialist advice should be sought as necessary. Personnel undertaking the visit should be briefed on the hazards that could be encountered and the precautions to be taken.

NOTE 2 Information about the nearby area can include:

  • natural or man-made exposures such as cliffs, quarries or pits, railway or road cuttings can reveal soil and rock types and their stability characteristics;
  • embankments, buildings or other structures in the vicinity that have a settlement history because of the presence of compressible or unstable soils;
  • other important evidence that might be obtained from reconnaissance is the presence of current or old mine workings (see Annex F) or other underground excavations, such as old cellars, tunnels or sewers; and
  • other important evidence that might be obtained from reconnaissance is the presence of current or old mine workings (see Annex F) or other underground excavations, such as old cellars, tunnels or sewers; and
  • the behaviour of structures similar to those planned also provides useful information, as does the absence of such structures, for example, a vacant site in the midst of otherwise intensive development could be significant.

The type and abundance of vegetation on a site should be noted and can provide information on the groundwater conditions, chemical contamination of the ground, or the presence of ground gases (see BS 10175 and BS 8576). The presence of protected and/or invasive or injurious species should be noted (see 19.2.6).

If during the visit anything is seen that is deemed likely to pose an immediate threat to human health and safety or the environment, this should be reported to whoever is in control of the site so that any required action can be taken.

13 Earlier uses and state of site

13.1 General

If a site has been used for other purposes in the past, this can have a major effect on the proposed intended use; therefore, a careful visual inspection of a site, including the vegetation it sustains, should be carried out. This might reveal clues suggesting interference with the natural subsoil conditions at some time in the past.

A study of maps and information from all available dates and sources should be undertaken.

NOTE 1 The former uses of a site can sometimes be determined from such a study, which could include examination of aerial photographs, and could be carried out in tandem with an archaeological study. In some cases, the forerunners of local authorities commissioned the making of maps of their areas long before Ordnance Survey maps were produced, and these maps were often drawn in the most meticulous detail.

Former occupiers of the site should also be consulted, as they might be able to provide detailed information indicating the layout of facilities. The courses of former drainage systems should be identified.

NOTE 2 There might be several years between the survey date and the publication date of some OS maps. In addition, because of the potentially large intervals between surveys, activities can occur in an area (e.g. formation and filling of a pit) without it being recorded on an OS map.

NOTE 3 In the marine environment to high tide or where topographic changes can occur more rapidly, references to early Admiralty charts and other charts might indicate earlier configurations, see C.4.

13.2 Tunnels and underground structures

Where the presence of tunnels or underground structures are a possibility, they should be taken into account. It should not be assumed that they are all shown on Ordnance Survey mapping. Information from transport and services/utility infrastructure owners should be requested as needed.

13.3 Underground mining

Annex F gives details of the procedure that should be followed when carrying out enquiries and the subsequent ground investigation for an area where underground mining has been or is currently being carried out or planned.

Potential liabilities and ownership issues should be considered when planning ground investigations in areas potentially containing voids. Permission from the mineral and land owner should be obtained before any ground investigations are carried out; it is common practice for such investigations to be carried out in accordance with a licence or permit which places certain rights and responsibilities on each party, e.g. the Coal Authority.7) The responsible expert specifying the investigation should take responsibility for completing the application, obtaining the permit and ensuring thereafter compliance with the permitting requirements.

NOTE 1 The United Kingdom Health and Safety Executive also requires prior notification of certain ground investigation activities proposed within mining areas.

NOTE 2 Mining has been used to recover a range of materials including coal and minerals as well as construction and agricultural materials such as building and roofing stone, sand, clay, flint and chalk.

13.4 Quarries and opencast mines

Relevant sources of information should be consulted regarding the quarrying of materials such as building stone, chalk, sand, gravel and clay, which has been carried out since ancient times. Over the years, many excavations have been backfilled and then put to some other use; many such sites have subsequently been used for waste disposal (see BS 10175 and BS 8576).

The extraction of coal by opencast methods has been carried on extensively since the late 1930s and details of the availability of records are given in Annex C; the relevant records should be consulted.

Other minerals have also been extracted by opencast methods. The relevant records should be consulted.

13.5 Waste tips and landfills


The site under investigation might have been used for the tipping of mining waste, industrial waste, domestic refuse, chemical waste and miscellaneous refuse. Such sites require special consideration before any intrusive investigation is carried out to ensure the safety of ground investigation personnel and protection of the environment

It should normally be assumed that harmful chemicals and toxic or explosive gases are present. The Environment Agency in England, the Scottish Environmental Protection Agency, Natural Resources Wales, and Northern Ireland Environment Agency should be consulted, as appropriate, during the planning stage of investigations at such sites (see also BS 10175 and BS 8576).

13.6 Industrial sites


In many parts of the country, there are sites where heavy industries once existed. Often no visible signs remain of the buildings and other structures, but below ground level, for example, there might be foundations including piles and sheet piled walls, engine beds, pits, chambers, and underground storage tanks, often of massive construction, which can be major obstacles to redevelopment. The ground might still be affected by extremes of temperature from installations such as cold-storage plants, or high-temperature kilns and furnaces. The ground is also frequently contaminated by spilled chemicals, leaking sumps and drains, the spreading or burial of waste, or the importation of contaminated material. Historical aerial photography can be very useful in identifying the locations of physical obstructions and potential chemical contamination. Other sources of evidence might be identified by archaeological desk-based assessments.

Planning and building control records can be a useful source of detailed plans of the site including the location of underground tanks and services; such records should be consulted.

NOTE Care is required when using plans derived from planning and building control records as they do not always accurately show the "as built" layouts.

13.7 Monuments and archaeological remains

If it becomes apparent during the desk study that any Designated or non-Designated Historical Asset is likely to be affected by the investigation or subsequent works and if this has not already been noted in an archaeological study conducted as part of the same project, then the project's archaeological consultant or contractor, if such have been appointed, should be notified. If no such appointment has been made, the matter should be referred to the relevant local (Local Planning Authority) or national (English Heritage, Cadw, Historic Scotland or DOE Northern Ireland) authority as appropriate.

13.8 Ecology

Ecological issues should be carefully taken into account, because they could impose significant constraints on both the execution of the ground investigation and on the future development of the site.

NOTE Many plants, animals and habitats are specially protected by law. Attention is drawn to the Conservation (National Habitats, etc.) Regulations 1994 [11].

BS 5930:2015 Code of practice for ground investigations