MRBCA - A New Term and a new ERA
by Keith Piontek - P.E., The Forrester Group from The Missouri Environmental Insider, Vol. 6, Issue 3, April/May 2004
Used by permission

With the release of the Missouri Risk-Based Corrective Action Process (MRBCA) for Petroleum Storage Tanks in January of 2004, we now have a new term in the lexicon of site remediation in Missouri, and the start of a new era in how many environmentally impaired sites will be managed. This new MRBCA process will apply not only to Petroleum Storage Tank sites. While the guidance for the tank sites was the first out of the box, broader guidance for other sites (for example, sites in the Brownfields/Voluntary Cleanup Program) should be out for public comment before the end of the year.

The development of the new MRBCA process, and the issuance of the guidance, is all in response to Senate Bill (SB) 334, signed into law in August of 1999, which required the Missouri Department of Natural Resources (DNR) to develop risk-based ground-water remediation procedures through the rulemaking process. In a subsequent and ongoing stakeholder consensus process led by Department of Natural Resources (DNR) staff, it was determined that a sound risk-based process needed to encompass all environmental media (not just ground-water), and that the actual rulemaking should be deferred until after a host of inter-connected policy and technical issues are resolved through the development of technical guidance.

It has taken longer than anticipated by most participants in the process to see the fruition of SB 334, but the higher level of risk-based decision making envisioned in the legislation is now a reality. In a policy statement issued in April of 2003, DNR stated, “Although the department remains committed to the formal rulemaking process, it need not delay the use of the RBCA process. The department hereby adopts this commitment to implement the RBCA process as a mater of policy.” The author can personally attest to DNR’s commitment, and the new flexibility made possible by the MRBCA approach (see “St. Louis Senior-Housing Renovation Saved by Risk-Based Solution in the February/March issue of Missouri Environmental Insider).

What is the MRBCA process? It is consistent with the definition of RBCA adopted by EPA in 1995 (OSWER Directive 610.17): “A streamlined approach in which exposure and risk assessment practices are integrated with traditional components of the corrective action process to ensure that appropri ate and cost-effective remedies are selected, and that limited resources are properly allocated.” It is consistent with the three-tiered approach embodied in the American Society for Testing Materials (ASTM) RBCA guides, which are the basic framework for RBCA programs in states across the nation. Given the “fear and loathing” the term RBCA had among some key stakeholders early in the process, the adoption of the ASTM RBCA standard is a develop ment of substantial significance.

A basic premise of the MRBCA process is that more ‘up front” investment in analysis of site-specific risks will yield return on the ‘back end” in terms of site-specific cleanup goals, more flexibility in managing potential risks, and (in many cases) reduced corrective action costs.

Examples of the greater investment in site-specific risks are the evaluations of the groundwater use and vapor intrusion pathways embodied in the guidance. The guidance specifies a process to evaluate whether or not zones of subsurface saturation merit protection as a current or potential future source of drinking water, which provides greater flexibility in groundwater cleanup levels than has historically been the case.

However, because all potential pathways must be considered, one must also examine the potential for constituents of concern in groundwater to volatilize and migrate into structures (the vapor intrusion pathway), which may in some cases result in a more stringent cleanup level than has historically been the case. At a minimum, the attention that must be given to the vapor intrusion pathway will force DNR, the regulated community, and consultants to add to the toolbox employed in managing environmentally impaired sites.

The manner in which the vapor intrusion pathway should be evaluated and the appropriate role of institutional controls (aka activity use limitations or AULs) in a RBCA approach are two of the most unsettled issues in the MRBCA process. While the technical guidance that was released for tank sites specifies has a certain vapor intrusion pathway methodology, it is recognized that this part of the guidance needs additional work, and a stakeholder committee (pursuant to the overall stakeholder consensus process) is currently deliberating this topic. With respect to AULs, the AUL policy that currently appears in the technical guidance for tank sites may not be the same as the AUL policy that will be incorporated into the technical guidance for other sites. Among DNR management, there appears to be momentum building in support of a change in state law that would reflect the Uniform Environmental Covenants Action drafted by the National Conference of Commissioners on Uniform State Laws in 2003.

Another unsettled issue is exactly what portion of the technical guidance will appear in the rule required by SB 334. In general, there are two schools of thought on this issue. One is that the rulemaking process is arduous, and it is in no one’s interest to have to go through rulemaking every time there is a change in science or technology that should be reflected in the MRBCA process (for example, default numerical cleanup standards). The other is that changes to the MRBCA process should have stakeholder imput, and the way to ensure that happens is to have details of the process in the rule. DNR staff expect to have greater clarity on the nature and timing of the specific rule or rules needed to implement MRBCA by this Fall.

The specific nature of the MRBCA process is yet to be fully defined, and the degree to which the underlying “protective but more cost-effective” promise of RBCA is achieved is yet to be determined. However, a new era in managing environmentally impaired sites in Missouri is upon us. It’s been a long time since SB 334, but we’re now at a point where we are going to start finding the answers to these questions very quickly.

For more information, contact Keith Piontek, P.E., with The Forrester Group, at 636-728-1034, or email