While the RBC represents a valiant effort on the part of a few individuals in the EPA, the RBCA (pronounced "Rebecca") is the fruition of years of hard work by the American Petroleum Institute (API) and the American Society for Testing and Materials (ASTM). The full title of the document is "Emergency Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites." It was ASTM ES38-94 and is now E-1739-95e1 which you can see a synopsis of . Go to ASTM ,then ASTM Store, then search for individual standards, then search for e1739. (I can't seem to get a direct link, but it is worth your while to find this and peruse it.) With a credit card and $45 you can get a copy of the standard sent to you by pdf file. None of which you have to do. But here are the key points:
RBCA uses the concepts of TIERs. The first Tier is very similar to RBC. RBCA has lookup tables RBSLs, risk based screening levels, that are similar to RBC, and likewise based on very conservative assumptions. If the contaminant is less than the RBSL table, you should be able to walk. Also, if the contamination can easily be cleaned up to below the table value, you should do that, then walk. Tier 1 also suggests that you calculate the cost of doing a real risk assessment, and if the cost of cleaning up is less than the cost of the full risk assessment, then you should clean the site (to the levels in the table) rather than spend the money on the risk assessment.
In order to use the table, you need to do a site assessment and develop a CSEM in order to know which section of the tables to use. Here is an excerpt for review purposes from the RBCA table:
Note that it only covers six chemicals: the four BTEX volatiles, the semi-volatile Naphthalene, and the nonvolatile Benzo(a)pyrene. In general these are the most common chemicals of concern at petroleum spills and contaminated sites. If these are below the RBSL table, the site is likely clean enough.
Tiers 2 and 3 involve more risk management, but basically Tier 2 involves determining some compliance point (often the property line), and again determining if the contaminant is likely to be less than the RBSL at the compliance point. Tier 3 is just the risk assessment as you have been learning, with the exception that if cleaning the RBSLs is cheaper than proceeding to the next tier, you should just clean to the RBSL.
In summary, both RBC and RBCA publish very conservative numbers, such that, with adequate sampling and analysis, if you determine the contamination at your site is less than the level stated in the table, you should not have to do anything further on the site. If it is feasible to clean up to the RBSL, you should do that, rather than a complete risk assessment. End of Sub-module 9B. BACK
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