Introductory RA

What is a contaminated site?

Who does what?

Why is it important?

What is risk management?

Risk assessment fundamentals

Risk assessment methods

Limitations of risk assessment

What are RA tiers?

Framework

Initiation 

Problem Identification

Site Characterisation

Site Investigation

Receptor Characterisation

Exposure Assessment

Toxicity Assessment

Risk Characterisation

RM Decisions

XYZ Example

Resources

Glossary

FAQ's

Introduction

It is assumed that you have already identified a particular site as requiring a RA. The objective of Problem Identification is to ‘take stock’ of the problem for a particular site, and answer the question:

'What do we think the problem is?'  

"What information should be collected and assessed to confirm our understanding of the problem?"

The main outcome of the Problem Identification stage is to set the overall purpose and objectives of the RA and to determine the likely data requirements. This step should:

• Clearly identify what aspect of the RA needs to be addressed;
• Set the objectives of the RA (what will and will not be considered), and
• Identify what information needs to be collected, analysed and assessed.

Risk Assessment Objectives

The specific objectives of the assessment will depend on the state of knowledge about the site.

• If no previous studies or sampling have been undertaken, the objectives may relate to establishing whether contamination is present, at what concentrations and in what media.
• If there has been a previous investigation, this step may identify that a particular contaminant pathway needs to be further assessed.
• If previous Tiers of a RA have been completed, this step may address a particular information gap.
  The objectives of a Risk Assessment will vary depending on the nature of the site and the Tier at which the Risk Assessment is being undertaken.

Tier 1 - Problem Identification

The first part of this step is to assess existing information and identify the problem that the RA is trying to address.

Any preliminary findings about the site should be documented. Care should be taken to make sure that all available information is carefully assessed before the next stages of the RA are undertaken. At this stage it is important to identify and document the following details:

• current and historic land uses
• potential/actual contaminants of concern
• potential pathways
• potential receptors
• areas of uncertainty.

Problem Identification should consider a wide range of possible contaminants, receptors, and pathways. This should lead to the formulation of a conceptual site model that can be tested through the RA process, and provide the basis for developing the objectives for undertaking a Tier 1 assessment.

In most cases some general information about the site should be available from the Initiation stage. This should include current and past land uses, consent information, and site records. Further information is generally necessary to undertake a full site characterisation, including:

• land use and land-use history:
  • identify existing and past land uses on site
  • identify nearby existing and past land uses
  • document any gaps in these records
  • identify what chemicals or materials were used at the site (types, quantities, processes, storage, and disposal).
  • identify and document any incidents of chemical releases and possible release mechanisms
• identify potential or possible contaminants of concern
• identify other contaminant sources (e.g. nearby factory, natural contaminant source), and
• broadly define the surrounding environment and identify:
  • potential ecological values
  • buildings or heritage sites
  • sensitive land uses (e.g. school) or human receptors, and
  • cultural sites.

Using this information, you should draw preliminary conclusions on the following key factors:

• contaminants of concern;
• potential receptors; and
• main pathways (contaminants release, transport and fate mechanisms).

Any assumptions used in completing the site characterisation, and any information gaps should be clearly documented.

An example checklist is provided to help you to undertake a site characterisation and a completed example is also provided for the XYZ Enterprises example.

It is often useful to develop a conceptual model in the form of a flow diagram or site map to identify and clarify the problem and to identify any information gaps. Examples of a conceptual model diagram for XYZ Enterprises is shown, but you may choose to undertake this process using a different diagrammatic approach. Examples of other conceptual models are shown in USEPA 1998 Appendix C.

The construction of a simple site model is a useful tool to help characterise a site. A large number of site visualisation and characterisation models or software packages have been developed in recent years. These models may assist you in fully identifying the problem at the site of concern.

	Introductory risk assessment information on the next RA stage: Receptor characterisation
	Advanced risk assessment information on Problem Identification