The department is in the process of revising and updating the Missouri Risk-Based Corrective Action (MRBCA) Rule and accompanying technical guidance document. A stakeholder workgroup, consisting of consultants, industry groups and partner agencies met to hear from the user community and review the department’s list of proposed updates and revisions. The stakeholder workgroup reviewed a draft of the revised guidance document and provided comments.
The MRBCA rule became effective on Oct. 30, 2009. Both the rule and the guidance are used to guide the investigation, risk assessment and cleanup of contaminated sites. Most sites to which the rule and guidance have been and will be applied are enrolled in the department's Brownfields/ Voluntary Cleanup Program.
MRBCA is similar to other risk-based remediation systems used by other states. It includes three evaluation tiers, with increasing levels of site-specificity, complexity and cost. The majority of sites are cleaned up under Tier 1.
The MRBCA process includes Risk-Based Target Levels (RBTLs) that are conservative, default cleanup levels. RBTLs are used to guide site investigation, determine whether contaminant levels at a particular site require further action (screening) and determine when sufficient cleanup has occurred. The RBTLs published in 2006 were based on information current at the time.
Since 2006, certain toxicological properties and data evaluation methods used to develop the RBTLs have changed. The vapor intrusion exposure pathway also become an even more important aspect of site investigations, risk assessment and cleanup. As a result, the RBTLs published in 2006 are out of date and need to be updated. Additionally, the department identified needed clarifications in the MRBCA guidance and determined that a guidance revision is warranted.