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Guidelines on remediation of contaminated sites

3. Initial survey

3.1 Introduction

During the initial survey, all information on the relevant site which is immediately available, should be obtained. The primary objective at the majority of industrial sites is to identify both the nature and physical location of the potential sources of contamination.

Information collected in the initial survey provides the foundation for the rest of the course of the investigation. Therefore, the initial survey should be executed with the greatest of care.

The initial survey comprises:

	Collection of historical data on use of the site, including information on possible listing of the site, cf. Guidelines on Mapping /1/.
	Acquisition of geological and hydrological data for the area.
	A site visit.
	An assessment of the data collected and a hypothesis on possible contamination.

3.2 Previous and current land use

As far as possible, the previous and current land use of the site should be described through acquisition of data on:

	The precise location and extent of the site. It is important here to note that a site can previously have extended further than the current limits, if the area has been parcelled out.
	All building activity and possible alterations to the terrain.
	The types of enterprises and possible other land use of the site in chronological order.
	All potential contaminating activities on the site are to be determined from information on production, including which equipment and processes have been used. It may be relevant to obtain information from different periods of the enterprise’s operations, since production methods may have changed.

There are a large number of sources from which information may be obtained. Table 3.1 lists a number of useful sources. Based on previous experience, the sources are divided into primary and secondary sources. The most important information is to be found in primary sources. If the primary source is thought to be inadequate, supplementary information can be sought in the secondary sources. This division is a recommendation only, since the need for information is naturally determined by the individual site. Furthermore, refer to ‘Guidelines on Mapping Soil Contamination and Sources’ /1/.

Table 3.1
Overview of sources of information on previous and current land use of sites.

Below is a short introduction to the sources mentioned in Table 3.1.

Local authority records

Local authorities maintain records of construction activities, including construction of sewage systems. They also keep records on environmental approvals and inspections, including contamination which has been ascertained, and they have records of underground oil and chemical storage tanks, as well as enterprises which generate chemical waste.

Some local authorities keep all the above information on a specific site in a single file, but filing practises vary from local authority to local authority.

Environmental permits contain descriptions of production processes, measures to limit contamination, and waste products and their disposal. Environmental permits cover the period after the Environmental Protection Act entered into force in 1974. Certain types of enterprises with regional impact are listed in the Act. These enterprise are supervised by the regional authorities.

Local historical records

At local historical archives, old maps, telephone directories, and information booklets may be available. There may also be collections of relevant photographs and newspaper clippings. Furthermore, personnel at these archives often have extensive local knowledge.

Background material on equipment and processes

General knowledge of production techniques, processes, raw materials, and chemicals etc. can be found in specialist literature and at sector organisations.

Materials which are specially relevant to the soil and groundwater have been prepared for a number of types of enterprise/sector. Besides descriptions of the enterprises’/sectors’ production and potential sources of contamination, including parameters for analyses, several references include descriptions of previous experience from earlier investigations, as well as soil and groundwater contamination which has been ascertained at the site. References to this material are included in Appendix 3.1.

Interviews and site visits

Interviews with previous and current employees can support and supplement information from records and literature. If possible, the collection of data should therefore include interviews.

A site visit should be carried out. During the walk through, information collected from records and archives should be checked against current conditions. The location of existing buildings and installations should be recorded and visible signs of soil contamination should be noted.

Moreover, it may be important to note information regarding access to the site for use in planning boring activities, etc.

Appendix 3.2 provides a checklist which can be used for the site visit.

Company records

The enterprise may maintain relevant information. Examples include: statements or data booklets regarding quantities of raw materials used and products produced, old photographs, or drawings.

Land Registry Office

Information on previous owners of individual sites is registered here. Information can be obtained from the Land Registry Office in the individual local authority by checking the declarations for the relevant cadastre and the appendices to these.

Police and fire departments

Information on previous stores of flammable and explosive substances may be kept by the local police or fire department. These authorities may also contribute with chronological information on actions which may have environmental significance, e.g. fire or other accidents such as spills, leaks, or overflows from tanks. In some cases, they may have information from the local authority records from before 1970.

Register of Companies etc.

More detailed information companies registered as limited can be obtained from the Register of Companies, Kompass Danmark, or Greens Danske Fonds og Aktier (Greens Danish Funds and Shares). These documents often include the company’s primary activities.

The National Working Environment Authority

Information on chemicals and accidents can be obtained from the National Working Environment Authority. To access historical archives the name of the enterprise is used, rather than address or cadastre numbers.

The Royal Library

A limited number of aerial photographs from before 1945 are kept at the Royal Library.

Aerial photographs can be useful in obtaining an impression of land use at the site. Tanks, barrel/drum stores, and waste can be localised from aerial photographs. The library also has a large collection of maps.

The Danish National Business Archive

‘The Danish Tariff Association’s Archive’ (Dansk Tarifforenings Arkiv), which is at the Danish National Business Archive in Aarhus contains a lot of relevant information based on insurance companies’ inspections of all larger enterprises (app. 50,000) in the period 1896-1982.

The register can be inspected at the Danish National Business Archive, while access to the reports themselves requires permission from the owner, the Danish Assurance Association (Dansk Skadesforening).

National Survey and Cadastre

Aerial photographs from 1945 onwards are available from the National Survey and Cadastre. Use of aerial photographs is described under ‘The Royal Library’.

Finally, the Danish National Museum has information on registration of industry.

3.3 Surface water recipients and soil and groundwater conditions

When obtaining information on geological and hydrogeological conditions in the area, a preliminary vulnerability assessment may be made.

In addition, an overview should be obtained of water abstraction, groundwater flows, and surface water recipients in the area.

Data for descriptions of soil and groundwater conditions, as well as surface water recipients is obtained from:

	Topographical maps (scale 1:25,000)
	Geologic basic data maps (with Danish cyclogram symbols)
	Maps of the groundwater’s potentiometric surface
	Water abstraction plans
	Water supply plans
	Geological literature
	Other investigations in the area

Information on the potentiometric surface, water abstraction, and groundwater quality can be obtained from the regional authorities.

The regional authorities, and to a large extent the Geological Survey of Denmark and Greenland (GEUS) and local authorities, can contribute with information on the location of borings and wells in proximity of the site. In addition to the location of borings, information on the geological strata and the depth of the groundwater is available.

3.4 Reporting

The results of the initial survey should be reported in such a way that the data collected, cf. Sections 3.2 and 3.3, is presented clearly and comprehensibly. The results should be assessed and related to the original hypothesis for possible contaminating activities at the site.

Sources of information should be stated, cf. Table 3.1, and possible ‘holes’ in the (historical) information collected should be considered.

There are advantages in reports comprised of a data sheet with relevant maps as appendices. The data sheet states information in table and in the form of key words. On one or more maps, relevant characteristics of buildings or production are shown, including where potential contaminating activities have taken place/take place.

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