Course: BLD 159 Intro to Brownfield Remediation, Land Re-use, and Public Health

Reading: Risk-Based Corrective Action (RBCA)

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Risk-Based Corrective Action (RBCA)

How does RBCA Work?
The ASTM standard (E1739) is based on a "tiered" approach to risk and exposure assessment, where each tier refers to a different level of complexity. For example, in the three-tiered approach:
- Tier 1

Tier 1 consists of a qualitative risk-assessment based on general site assessment information. This data would need to identify obvious environmental impacts (if any), potentially affected sensitive receptors (schools, homes, water bodies, etc.), and significant exposure pathways (drinking water wells, recreational use of streams, vapor transport, etc.). When gathered for a number of sites, this information is typically sufficient to help categorize sites and determine acceptable time frames for corrective action (immediacy of response), if necessary.

- Tier 2

Tier 2, more site-specific data is utilized to determine the appropriate risk-based actions. Here, the reasonable maximum site-specific impact is evaluated through the use of site-specific characterization and monitoring data, conservative projections of expected levels of contaminates after treatment and potential plume migration, and reasonable maximum exposure scenarios. This information is used to set conservative corrective action objectives that are protective of human health and the environment.

- Tier 3

Tier 3 focuses completely on the site-specific conditions. More sophisticated mathematical descriptions of fate and transport phenomena are used and descriptions of the range of possible exposures/risks are generated. At this level of complexity, site specific risk assessment models may be developed. Due to the costs involved, this analysis is suited to only large sites.

It is important to note that the goal of all tiers is to achieve similar levels of protection. The difference is that, in moving to higher tiers, more efficient and cost-effective corrective action results because the conservative assumptions of earlier tiers are replaced with more realistic site-specific assumptions. Additional site assessment data may be required as sites move to higher tiers.