USEPA Environmental Response Team (Cont.)

make a good prediction of risk. This document outlines what the basic contents of

a WP and an SAP should be and that they should follow the EPA model for work

plans and SAPs. The end of Step 4 also has an SMDP to approve the work plan

and sampling and analysis plan that will be used in the next steps of the risk

assessment.

Step 5 - Field verification of sampling design

In this step, the information collected thus far is verified and the feasibility of

sampling is evaluated after visiting the site. Some elements of the WP or SAP

may need to be modified to meet the objectives of the risk assessment. These

changes can be made in consultation with the risk assessor and risk manager. If a

reevaluation of the assessment endpoints in the WP or SAP is needed, however,

the assessor must return to Step 3. The SMDP for Step 5 is the signing of the

finalized WP and SAP.

Step 6 - Site investigation and analysis phase

This step involves field sampling and surveys as well as analysis of exposure

and ecological effects. Field sampling implements the plans designed in Step 5 to

collect data. The analytic approach for characterizing exposure effects and

ecological effects is outlined in the WP and SAP and are based on the site

conceptual model. After sample collection and analysis of exposure and

ecological effects, an exposure-response analysis is conducted. This analysis

relates the "magnitude, frequency, or duration of contaminant stressors ...to the

magnitude of the response." Also, "measurement endpoints [measures of effects]

are related to the assessment endpoints using the logical structure provided by the

conceptual model." An SMDP is needed in Step 6 only if the WP or SAP needs to

be altered.

Step 7 - Risk characterization

The risk characterization is a "qualitative and quantitative presentation of risk

and the associated uncertainties." The risk characterization involves risk

estimation and risk description. In the risk estimation component, the assessor

must describe the methods used and reasoning behind the connections made

between exposure profiles and exposure-effects information. The risk description

provides information important for interpreting risk results and identifies a

threshold for adverse effects on assessment endpoints. One caution that the

guidance makes is to clearly distinguish between uncertainty and variability in the

description of risk.

Step 8 - Risk management

This step is the responsibility of the site risk manager. There must be a balance

of the risk reduction associated with cleanup with the potential ecological impacts

of the cleanup process itself. The decision must be made whether or not to clean

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Appendix A Summary of Federal, State, and Regional Guidance