Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:2:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 2 (pt 4/9)
Character Range: 904395–907420

the risk assessment. The steps recommended are:
    * identify the stakeholders
    * decide which of them it is appropriate to consult at this stage of the project.
Frame the answers to the following questions and discuss them with the stakeholders:
    * Is a risk assessment the right type of decision-making tool?
    * What is the issue that the proposed risk assessment is considering?
    * Why is a risk assessment necessary?
    * What do we want to find out?
    * What are the hazards posing a risk?
    * The source of the risks?
    * What exposure pathways should be investigated?
    * Who might be exposed and who will not be exposed?
    * What decisions need to be made?
    * Timing of the assessment (urgency of answers)?
    * Level of complexity/detail of risk assessment needed?
With the outcome of the consultation known, determine the objectives for the risk assessment. Where not all the stakeholders have been consulted, consideration of their likely objectives should be included.

     2.3.1.2         Problem formulation
The problem formulation stage is where discussions are conducted on how to conduct a risk assessment that covers the matters identified in the planning and scoping stage. Two critical products of the problem formulation stage are a conceptual model that explicitly identifies the stressors, sources, receptors, exposure pathways and potential adverse human health effects that the risk assessment will evaluate, and an analysis plan (or work plan) that outlines the analytic and interpretive approaches that will be used in the risk assessment (NRC 2008).

    2.3.2          Exposure pathways
The fundamental concept of risk assessment is that there should be an exposure pathway linking the source of contamination and the exposed population. Where this linkage exists, an assessment of the nature and significance of the exposure pathway is required to determine the level of risk.

    2.3.3          Conceptual site model
A key concept behind all risk assessments is the definition of a suitable CSM specific to each site. The CSM describes the source(s) of contamination, the pathway(s) by which contaminants may migrate through the various environmental media, and the populations (human or ecological) that may potentially be exposed.

A detailed CSM should include information on the following (on- and off-site as relevant):
    * the contaminants: nature of the contaminants identified, concentration, fate and transport, distribution and media in which they occur (soil, water, vapour, sediment or air)
    * physical characteristics of the environment:  soil type, porosity, vadose zone thickness, groundwater gradient and velocity and hydraulic conductivity of the saturated zone and the potential presence of preferential migration pathways
    * physical characteristics above-ground: sizes and locations and structures of current or future buildings (if known); potential presence of preferential vapour pathways; nature, size and location of outdoor spaces