Risk-based cleanup of contaminated property.

Determining appropriate cleanup objectives is a critical first step in remediating contaminated properties. Historically, many regulatory agencies have used conservative standard-based criteria (i.e., drinking water standards). Other agencies have required cleanups to background levels, usually assumed to be pristine environments. These types of criteria have contributed to costly cleanups and dormant brown field properties.

Recently, there has been a trend to use site-specific risk-based cleanup goals instead of "standard-based" or "background levels." When properly planned and conducted, risk-based cleanups protect human health and environmental resources just as effectively as previous criteria. Risk-based cleanup can be less extensive and less costly because site-specific conditions, potential risks, engineering controls and proposed land use are all considered.

In 1994, the American Society for Testing and Materials (ASTM) published Emergency Standard Guide For Risk-Based Corrective Action Applied at Petroleum Release Sites (ASTM ES 38-94), which provides a consistent, three-tiered approach for the development of risk-based cleanup goals. Also in 1994, the U.S. EPA published Draft Guidance For Soil Screening Level Framework, (SSL) which contains guidelines for preliminary risk assessments based on site-specific data.

In 1995, the Illinois Environmental Protection Agency (IEPA) established a Risk-Based Corrective Action (RBCA - pronounced Rebecca) procedure to develop cleanup objectives for the remediation of both soil and groundwater. IEPA used the above ASTM ES 38-94 and U.S. EPA SSL documents to serve as the foundation for their procedures. In November of 1995, the Illinois Brownfields Law passed, which also includes these concepts.

The RBCA Process

The process uses a three-tiered (choice) approach. The following is a brief summary of the three tiers of cleanup objectives:

Tier 1 - Goals published by IEPA based upon conservative assumptions and a limited amount of site-specific information. These are generic and based on one in one million health risks.

Tier 2 - Goals are developed through the use of simple analytical models (RBCA and SSL equations) which consider site-specific data and conditions. Tier 2 objectives are less restrictive than Tier 1 objectives, but are still relatively conservative.

Tier 3 - Goals are set by use of more site-specific information. They are developed through formal risk assessment procedures and sophisticated models that account for physical/chemical processes, contaminant movement, availability and likely potential human exposure. Establishing Tier 3 objectives generally requires a substantial effort relative to Tiers 1 and 2, but may yield a much easier to achieve objective, or may demonstrate that no cleanup is required.

A site owner has the option of which tier will be used to set cleanup objectives for the property. The actual level of contamination present is first compared to published Tier 1 objectives. If concentrations exceed Tier 1 levels, the owner has the option of either cleaning up to meet Tier 1, or developing site-specific cleanup goals through the Tier 2 or Tier 3 processes.

Here is an example of how clean is clean enough. Prior to RBCA, 25 ppb would have been the cleanup level required for certain soils contaminated with trichlorethylene (TCE). The new RBCA Tier 1 level is up to 100 ppb, and, depending on site-specific conditions, Tier 2 levels could be even higher (e.g., 1,000 ppb or more). Tier 3 in this case could be higher yet, and might even eliminate the need for any cleanup. The flexibility and easier to meet criteria of RBCA will save landowners millions of dollars and make it feasible to remediate many sites that were previously unaffordable.