If the site fails the screen, then the risk management decision will focus on whether to implement an interim cleanup or to proceed to a Tier 2 BERA. The RPM, together with input from the risk assessor, should consider a number of issues when making this decision:
1.What are the implications of selecting interim cleanup vs. proceeding to a Tier 2 BERA? Consider issues such as cost, policy, and social concerns. For example, in some cases it may be more cost effective to implement interim cleanup than to conduct a Tier 2 BERA, especially if the site is small and the volume of contaminated media is small. Alternately, the results of the Tier 2 assessment may indicate that remediation is not warranted, thus incurring a significant cost savings. As another example, there may be considerable public pressure to do something at your site. In this case, if the SRA identifies unacceptable risks and the site is small, it may be not only cost effective to implement an interim cleanup, but such a decision could go a long way in placating the public's desire to see some level of cleanup.
2. If interim cleanup is selected, what might be the implications of the Tier 1 Preliminary Cleanup Goals on the scope and cost of the cleanup? If interim cleanup is selected, preliminary remediation goals (PRGs) must be developed. PRGs represent the target contaminant media concentration levels for the cleanup. These PRGs are derived by back-calculating the media or dose concentrations so that the HQs = 1.0 or less. For media-based HQs, the PRG will be the SEV, even though the EPA Superfund ERA guidance specifically states that SEVs are not defensible cleanup goals, and should not be used as such. For dose-based HQs, the PRG will be a function of the SEV and the very conservative dose models, and the resultant back-calculated PRG will be very low. Use of these low PRGs may result in cleanup volumes that are likely much greater than necessary, resulting in higher than necessary costs.
3. How might the ecological impacts of interim cleanup compare with the impacts of not taking action? Interim cleanup may require the elimination of certain habitats and result in the loss of some ecological resources. Given the nature of the resources affected and of the interim action, restoration of the impacted habitats may be very difficult. Implementing an interim action may cause more harm than good, especially if there is a high degree of uncertainty associated with the SRA.
4. How might the risk characterization change following the Tier 2 reevaluation of the SRA assumption? The first step of the Tier 2 BERA, Step 3a, involves the re-evaluation of the Tier 1 results through the use of more realistic (less conservative) exposure assumptions. For example, Step 3a may utilize a SUF of 0.5 rather than 1.0, and AE and BA assumptions of less than 100%. Use of such less conservative values in the dose models will result in lower dose estimates and subsequently lower HQ risk estimates. Depending on the extent of the modeling revisions, HQs < 1.0 may now be indicated for one or more of the COPCs previously retained by the SRA. These can now be eliminated from further consideration, and no remediation for the site may be warranted. Proceeding with interim cleanup precludes the conduct of Step 3a, and may thus result in a cleanup that may not have been necessary. Step 3A is discussed in detail in Section 3 of the Ecorisk Process portion of this web site.
In general, interim cleanup may be considered when:
Interim cleanup should not be considered when: