ISO 18400-202:2018 土壌の質 — サンプリング — Part 202: 予備調査 | ページ 7

7 Scope of preliminary investigations

7.1 General/strategy

The preliminary investigation should consist of:

• a desk study, including consultations (see 7.3) with those who might have relevant information about the site, in which information on the history and other relevant aspects of the site, is collected and critically reviewed (see 7.2);
• a site reconnaissance (site inspection, walk-over survey) (see 7.4);
• development of a conceptual site model (see Clause 8), which in the case of potentially contaminated sites should include:
  • formulation of hypotheses on the possible type(s) and amount of contamination, migration pathways (on- and off-site), and spatial and temporal distribution; together with hypotheses regarding other aspects of the site, such as the hydrogeology;

• drawing conclusions with regard to the need for and scope of further investigations (see 8.4);

• identification of any need for immediate actions to protect humans or the environment (e.g. fencing, removal of superficial deposits).

7.2 Desk study

7.2.1 General

A desk study should include collection of all relevant information on the site, e.g. references to the location, infrastructure, utilization, historical information. It should comprise a combination of documentary research (see 7.2.1) and consultations (see 7.3). The search radius around the site for which information is to be gathered should be specified at the outset of the investigation.

The site location and site boundaries should be accurately established before any investigatory work is commenced.

The desk study should include, as appropriate, the following topics, amongst others (see also Tables 1 to 3):

• a) ownership and occupier(s);
• b) the history of the site and adjoining areas, with particular attention to the nature of any industrial processes and other activities that could have been potentially contaminative or could have modified the ground structure to create potential migration pathways;
• c) review of any previous desk study or investigation of the site;
• d) the geological, geomorphological, geochemical, hydrogeological, hydrological, topographical, archaeological and ecological setting of the site and surrounding area;
• e) potential receptors of contamination (for example, trespassers, current and intended users, construction workers, surface waters, ground waters or nearby water abstractions, ecological receptors, property);
• f) the proximity of waste disposal sites or other sources of contamination that could have an impact on the site;
• g) on- and off-site incidents that could have had an impact on the site such as fires or spills, etc.;
• h) the existence of naturally occurring harmful materials, such as radon, or naturally elevated concentrations of harmful substances;
• i) the presence of any mining activities;
• j) proximity to ecological sensitive sites or water protection areas;
• k) any constraints on an intrusive site investigation (access or height limitations, underground and overhead services or obstructions, noise, working hours, etc.);
• l) the potential for the site to contain or have been affected by unexploded ordnance (UXO)^[9];
• m) review of developers' designs and plans where the site is to have a change of use, with details recorded of the future use/characteristics of the site;
• n) any foreseeable events or changes (e.g. flooding, rising groundwater, planned or likely changes of use of neighbouring sites) that could have an impact on the assessment.

Sources of information that it could be useful to consult are publications, maps (check the accuracy of any map used and check whether there is a reproducible graphic scale), aerial photographs, satellite imagery, and records held by official bodies (see Table 4). Particularly important is information on the physical and chemical properties and the possible spatial distribution of the soil parameter under investigation; special attention should be paid to geological features such as stratigraphy and hydrogeology.

The sources of information available for use in preliminary investigations will vary from country to country and jurisdiction to jurisdiction and thus the guidance given about sources of information in this document is of necessity generic in character. The user will find it useful to prepare detailed information about local sources for their own use. National standards providing guidance on the design and execution of geotechnical investigations often contain a requirement that a desk study and site reconnaissance should be carried out and thus might provide useful guidance about potential sources of information.

7.2.2 Information on past and present use

The rapid growth of urban areas has resulted both in the absorption of areas which were formerly rural and in the change of use of existing urban land. Contamination within urban areas is therefore frequently the result of some historic industrial process that has occurred on the site, or nearby, and information to be collected for both urban and industrial sites is very similar.

It is important to recognize that an agricultural site or a wooded site could be a potentially contaminated site, not only because of activities carried out on the site but because they were developed in the past on potentially contaminated land, for example an old refuse disposal site (landfill) or mining waste. This could have significance for agricultural performance of a site and the health and safety of investigator; hence the need for a good site history to be developed.

Data gathered on historic and current use of a site should, where relevant, provide information on the following (subject to any agreed limitations within the objectives):

• any development, building or other activity that has taken place on the site and its immediate surroundings;
• any specific actions that were taken in the past, and any materials that were used (including chemical composition when available), in connection with industrial, building or other activities on the site;
• industrial or other activities which have been (or are currently) potential causes of soil contamination [production processes, storage facilities, materials transport facilities including underground railways with an indication (as precise as possible) of the location(s)];
• details with regard to cables, conduits, areas of soft landscape and areas of hard landscape, areas of made ground and areas of tipped material, effluent treatment, sludge disposal, surface drainage, chemical storage, underground tanks, waste materials, building rubble, etc.;
• information on adjacent land use (present and intended) which could affect the site under investigation;
• any incidents such as spills or detected leakages of potentially harmful liquids from tanks, pipes and drains on the surface or underground;
• deposition or burial of industrial, agricultural or domestic waste or temporary stockpiling of leachable materials (for example, road salt);
• presence of wind or water dispersable dust;
• demolition of industrial structures and dispersal or burial of contaminated rubble and other materials;
• importation of potentially contaminated fill material onto the land.

In addition, it should be determined whether unexploded ordnance (UXO) is likely to be present^[9].

Any available plans of the previous or current layout of different usages on the site should be inspected, as well as any plans of site drainage or underground services. Other information sources that should be consulted, as appropriate, are listed in Table 4.

The level of historical research undertaken should be compatible with the objectives of the investigation. The extent of research into the history of the site should take into account factors such as the complexity of past potentially contaminative uses on and adjacent to the site, the vulnerability of the site geology and local water environment, and the degree of confidence required by the client and/or regulator. The methods and extent of research should be agreed with the client (and regulator when required) in advance and modified as necessary according to the findings of the preliminary investigation.

7.2.3 Information on geology, pedology, geomorphology, hydrology and hydrogeology

Information should be collected on the geology and pedology of the area and the hydrological and hydrogeological situation as far as available. The scale at which this information should be collected, and the degree of detail that is required, depends on the defined objectives of the investigation.

The collected information should include:

• anticipated soil profile (natural and anthropogenic);
• obvious soil components (native or introduced) and their distribution regarding a statement on the homogeneity of the material;
• geomorphology including indications of artificial changes in topographic levels and landform;
• the nature of the underlying ground and the thicknesses of the underlying strata;
• presence of aquifers (number and type) and thicknesses;
• whether impermeable strata overlie an aquifer;
• tidal and seasonal variations in groundwater levels;
• groundwater flow direction(s), both on a regional and a local scale and variation with time (if possible);
• drainage patterns and the position of surface water courses, even if they are filled in at present and any continuity with groundwater;
• the presence of groundwater springs and wells and other abstraction points and any groundwater and soil gas monitoring installations;
• results of previous soil investigations at the site or its immediate surroundings, like boreholes or other forms of (geotechnical) investigations, in connection with, for example, building activities, and results of any chemical investigations;
• information on background geochemical aspects of soils and groundwater;
• properties of the contamination which could be relevant with respect to the local soil structure or profile (for example, humus in the ground could absorb contaminating organic compounds).

7.2.4 Ecology and archaeology

The preliminary investigation should determine whether the site (or its immediate environs) has been designated as an area of ecological or archaeological significance.

The preliminary investigation should also determine by enquiry whether it is known that there are species (e.g. bats, nesting birds, water voles, bats) or habitats present subject to legal protection.

The presence of invasive plant species, such as Japanese knotweed (Fallopia japonica) and giant hogweed (Heracleum mantegazzianum), or infective agents such as those responsible for foot/hoof and mouth disease (Aphatae epizooticae), and Rhizomania [Benyvirus; beet necrotic yellow vein virus (BNYVV)] or Ash dieback disease (Chalara fraxinea) should also be determined. Care should be taken during the site reconnaissance not to do anything that could lead to the spread of any such organisms.

Similarly subsequent ground investigations should be designed to avoid any spread of these species or infections.

7.3 Consultations

Relevant parties should be consulted, normally in parallel with the documentary research. This should include, when appropriate, consultation with authorities about the current use of the site including environmental and operational permits and discharge consents (i.e. permits to discharge water to sewers or water courses).

Among those officials or organizations that could be consulted are those responsible for

• management of contaminated sites on behalf of governments or local governments,
• management of groundwater and surface water resources,
• physical planning,
• controlling environmental impacts such as noise and air pollution,
• ecologically sensitive sites,
• storage of petroleum and other hazardous substances,
• sites protected because of their scientific values (in some jurisdictions these can include valued geological exposures), and
• archaeological and other heritage sites.

Client approval should be obtained before entering consultations with third parties and regulators, in case of confidentiality issues.

Where possible, and appropriate, interviews should take place with current or former owners and workers, current or former neighbours, neighbouring businesses, environmental groups, groundwater exploration companies, water companies, water quality inspectors, etc., to obtain for example, further information on, or enhance knowledge of, suspect locations or features, underground services, etc. The accuracy of such anecdotal evidence should be treated with caution unless the information can be confirmed by an independent source. Such consultations can be combined with the site reconnaissance (see 7.4).

7.4 Site reconnaissance

A reconnaissance of the site, neighbouring land (i.e. adjacent to the site) and the surrounding area should be made after available historical information and other relevant information has been obtained and collated. The area around the site for which information is to be gathered should be specified before the site reconnaissance is carried out.

Arrangements for the reconnaissance visit, including access, should be agreed with the client and the site owner and/or occupier, as appropriate, before being undertaken.

When appropriate, a request should be made for personnel visiting the site to be accompanied by someone familiar with the site, such as a plant manager, person in charge of maintenance or safety officer in the case of an industrial site.

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, but should be refined once the preliminary investigation is completed. The assessment should be kept under review as the investigation proceeds, but where there is any doubt as to the presence or degree of contamination then protective equipment should be used. Personnel undertaking the visit should be briefed on any hazards (e.g. physical, chemical, biological) that could be encountered and any precautions to be taken. Old buildings, etc. could be structurally unsound and should only ever be entered after an assessment of the potential risk of doing so (for further guidance on safety, see ISO 18400-103).

A strategy for the visit should be decided in advance and suitable plans, checklists and reference documentation prepared.

The principal objectives of the visit should be to:

• a) verify information on the site collated during the desk study;
• b) collect additional information about the site and its environs and, in the case of potentially contaminated sites, any potential contaminants, pathways and receptors;
• c) record observations of aspects of the site and its environs not revealed by the desk study, including the presence of invasive plant species;
• d) collect information that will assist in the planning of any subsequent phases of field investigation (for example any constraints to access).

Care should be taken during the site reconnaissance not to do anything that could lead to the spread of potentially harmful organisms (see 7.2.4).

Typical observations to be made during a site visit are:

• current usage and state of the site;
• site access and ease of movement on-site, and conditions which could prohibit sampling at specific locations (e.g. buildings or other structures);
• conditions at boundaries to the site and surrounding land usage;
• proximity of sensitive developments and habitats;
• potential site risks (e.g. overhead power cables, live services and voids);
• presence of hazardous materials;
• evidence that topographic levels (altitudes) have changed (both increases and decreases) as a result of human activity or natural processes;
• indications of contamination or other adverse conditions (e.g. vegetation stress or lack of plant growth, presence of visual staining or fibrous materials);
• visual evidence of contamination on or entering or emitting from the site or the presence of odours;
• condition of any surface waters;
• evidence of water abstraction points;
• existence of any ground water or soil gas monitoring wells;
• surface and, where there are existing monitoring wells, groundwater levels.

The topography of the site should be observed and compared to topographic levels (altitude) anticipated from the desk study. Raised ground and artificial slopes could be indicative of made or filled ground (anthropogenic ground).

If buildings still remain in which potentially contaminating processes could have taken place, the past and present usage should be reviewed and the buildings inspected for evidence of actual and potential contamination^[7]. However, care should be taken to ensure that it is safe to enter any building before doing so.

A photographic record should be made illustrating the site as a whole, and particular features of relevance to the investigation, subject to any restrictions forbidding photographs to be taken (in which case this should be noted in the report of the investigation).

If during the site reconnaissance anything is seen that is considered likely to pose an immediate threat to human health and safety or the environment, this should be reported immediately to whoever is in control of the site and to regulatory authorities or fire and police authorities when appropriate so that any essential urgent action can be taken.

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