Environmental Site Investigation, Contaminated Land, Planning and Development

Background

Over the past few years there has been an increasing awareness of issues surrounding land contamination and the potential for chemical substances upon, in or beneath the ground to impact upon people, animals and the wider environment. The government has set a target of 60% new build on previously used land, often referred to as ‘brownfield sites’. Frequently these sites have some form of contamination present upon them usually arising from past activities, particularly those sites of an industrial nature.

Risk Assessment

Risk assessment has become the essential tool for site investigations as the Environmental Protection Act (EPA) Part IIA requires a risk based approach to be used when assessing potentially or actually contaminated sites. This risk based approach is also required as part of the planning process for new developments.

Phased Site Investigation

Legislation and guidance regarding contaminated land requires the landowner and/or the developer of a site, which is potentially contaminated, to undertake a site investigation which is fit for purpose.

Site history is often complex and could involve several different industrial uses or activities that may have led to ground contamination from a wide variety of different sources.

Sites that have been used for one type of process may have become contaminated from a potentially large number of contaminants; processes change with time, chemicals are phased out of use and newer ones replace them, the layout of operations can be altered, demolition and reconstruction can also affect the likely presence and distribution of contaminants.

The investigation of contaminated land can be correspondingly complex and is ideally undertaken using a phased approach as identified in BS 10175. The need for and hence the cost of particular elements of an investigation are managed pro–actively depending upon the findings of the previous phase. Subsequent phases can then be carefully targeted. This avoids unnecessary work being undertaken. The phased approach typically consists of the following stages.

Site Investigation - Phase 1 Desk Study

Historical research and review of available information from sources such as archives, plans and records, databases and regulatory authorities to discover the past and current activities at a site and in the surrounding area and to assess them for potentially contaminative processes, to determine the potential for the presence of contamination.

The Phase 1 Desk Study identifies any potential sources of contamination resulting from the current and/or historical activities at the site and in the surrounding area.

The report will also identify any potentially sensitive receptors, e.g. humans, surface watercourses, aquifers, buildings or ecological receptors and collate the information relating to the site’s environmental setting i.e. geology, hydrogeology, industrial activity, location of controlled waters (canals, estuaries, lakes, ponds, rivers, springs, aquifers), pollution incidents and proximity to open/closed landfill sites.

This information is then used to undertake a qualitative risk assessment through the development of a conceptual model for the site. The conceptual model identifies any Significant Pollutant Linkages which may be present.

If Significant Pollutant Linkages are present then a Phase 2 site investigation may be required to quantify the risk and also to assess the potential for environmental liability associated with the site.

Site Investigation - Phase 2 Intrusive Investigation

An intrusive site investigation is then undertaken to investigate each aspect highlighted by the Phase 1 desk study, historical research and walkover survey. This comprises exploratory holes constructed using the most appropriate method for the site to investigate the local subsurface strata.

The Phase 2 intrusive contaminated land investigation is designed and implemented, using a variety of in situ exploratory methods, depending on factors such as sensitivity of the area, ground conditions (anticipated geology, hydrogeology, the expected presence of old foundations or other obstructions, which may have an impact on the technique selected), size of site and type of contaminants identified by the desk study as potentially present.

Chemical analysis of soil and water samples for common contaminants is performed to establish the concentration and extent of any contamination present. A risk assessment, using the “source-pathway-receptor” model would then be carried out, this assessment may be Qualitative or Quantitative dependent upon the site.

If a sensitive water receptor such as groundwater is identified beneath (or within the vicinity of) the site, then the investigation can also involve assessment of groundwater, using chemical analysis of water samples and computer modeling aided by various packages to quantify the risks posed. See (Groundwater Investigations).

Also see: On Site Chemical Analysis Investigation.

Site Investigation - Phase 3 Remediation Design, Execution and Validation

If remediation is deemed necessary following the Phase 2 works, then a site specific remediation methodology can be produced. Design of a site specific remediation methodology, as with all stages of investigation, involves consultation with the regulatory authorities to ensure satisfactory design and implementation of the remediation programme.

This can include delineation of contamination hot spots, further soil sampling, chemical analysis and additional monitoring, if additional information is required to supplement the previous investigation(s).

A wide range of remediation techniques are available and the methods chosen are dependent upon a range of factors including contaminant type and distribution, environmental sensitivity of the site, intended end use, cost and timescale etc. For information on our remediation work see Waste Management, Groundworks and Remediation.

Capabilities

ESG has been involved in a wide range of development projects requiring site investigations of potentially contaminated sites. We are able to provide a comprehensive contaminated land investigation service including:

• Production of Phase 1 Desk Study reports through extensive information gathering, analysis and interpretation;
• Designing, commissioning and supervising Phase 2 Intrusive Site Investigations, to meet the requirements of both the client and statutory authorities;
• Design & Implementation of remedial schemes and undertaking post remediation monitoring (Phase 3);
• Validation of remediation (Phase 4) and production of Post Remediation Validation Reports and remediation statements;
• Liaison with statutory authorities (e.g. the Environment Agency, local authorities, HSE etc.);

ESG undertake site investigations and reporting in accordance with relevant guidelines including BS 10175: 2001, DEFRA and Environment Agency guidance. We have extensive experience in undertaking site investigations on a wide range of sites.