USEPA CERCLA Guidance Documents (Cont.)

decisions made at each phase are similar. The USACE describes four phases in

the site investigation process.

a. Phase I is a preliminary risk screening of the site (known as PA/SI under

CERCLA and an RFA under RCRA).

b. Phase II, a baseline risk assessment (BRA), is performed in an Remedial

Investigation (RI) or Remedial Feasibility Investigation (RFI).

c. Phase III is a risk-based analysis of remedial alternatives in which

different options are evaluated for their potential to reduce the baseline

onsite risk Feasibility Study (FS) or Corrective Measures Study (CMS).

d. In phase IV, the short-term risks associated with remediation of a site are

assessed in a Resource Damages/Risk Assessment (RD/RA), CMI,

removal action, or interim corrective measure.

Within each phase of the site investigation process, the USACE defines five

steps for determining data needs.

a. Step 1. Background information review, site features, hazard information,

and exposure information are collected.

b. Step 2. Using the information collected in Step 1, a project decision

statement (PDS) is made which states whether the assessment should

continue or whether the site can be eliminated from concern.

c. Step 3. The data requires identification defining project study elements.

This step includes the development of a site conceptual exposure model

(SCEM). Note: In phase III of site investigation, two SCEMs are needed.

One SCEM is for the site during remediation or implementation of

corrective measures, and the other SCEM is for the site after remediation.

d. Step 4. The risk assessor must define and group data needs and describe

the methodology used to analyze the data.

e. Step 5. The data needs must be documented.

The authors of this document emphasize that risk assessments should consider

risk management needs. For example, "Under the PA/SI or RFA phase, screening

risk assessment and exposure analysis may be performed to determine the need for

further investigation." In Phase II (Remedial Investigation (RI)), the results of a

BRA are used to develop cleanup levels during the next phase (Feasibility Study

(FS) or Corrective Measures Study (CMS) phase). The purpose of an FS or CMS

is to provide a quantitative and qualitative evaluation of potential health impact

from remedial alternatives. Two types of risk assessments are done in an FS or

CMS. One assessment is done to develop chemical-specific remediation goals

(RGs) to be applied to site cleanup. The purpose of the other assessment is to

evaluate the short and long-term risk associated with each alternative.

A14

Appendix A Summary of Federal, State, and Regional Guidance