A risk assessment may be necessary in order to determine the risk to human health and the environment from contaminants in soil and/or groundwater. The risk assessment is a primary driver to determine the need and/or completeness of a remedial action. Ninyo & Moore has developed its Risk Assessment program to define and quantify the risk of hazardous substances to human health and the environment in accordance with EPA’s Risk Assessment Guidance for Superfund and other accepted risk models. A risk assessment provides technically defensible conclusions regarding the possible risk to human health or the environment from the contaminated media and will be based on current federal, state, or local guidelines. The risk assessment will include a discussion of strengths and weakness of the assessment by describing any uncertainties and explicitly stating assumptions and limitations, as well as providing the scientific basis and rationale for each assumption. Factors Ninyo & Moore typically considers when performing risk analyses include:

• Contaminant exposure pathways and media of concern
• Contaminant concentrations at potential exposure points
• Relevant and significant human toxicological information of each chemical of concern
• Risk characterization for each chemical and exposure pathway as potential human health hazards