Importance of background threshold value development within risk-based corrective action programs

Abstract

Risk-based corrective action (RBCA) programs employ conservative models to develop default values for soil screening, which simplify the risk assessment process. However, for several naturally occurring metals (e.g., arsenic and lead), these published screening values are often unrealistic and well below the documented background levels in soil. This can lead to confusion among the regulated community and inexperienced regulators, as it will inappropriately identify naturally occurring conditions as a release (false positive or Type I error). An effective RBCA program requires the incorporation of defensible background threshold values (BTVs) in the screening process. Recent datasets and BTV development methods are available to enhance existing RBCA programs and reduce the occurrence of Type I errors. This review evaluated the role “background” currently plays in the Texas Risk Reduction Program (TRRP) and offers defensible approaches in minimizing Type I errors estimated by one Texas municipality to directly result in an unnecessary expenditure of over $250,000 annually to address this confusion in the form of additional assessment, remediation, soil management, and even disposal requirements. The same BTV development process demonstrated in this Texas case study can also inform risk assessment efforts in other areas where BTVs can supplement existing RBCA programs.