ABSTRACT: Decisions that determine the proper risk-based remediation approach are based on technical, regulatory, cost, legal, and political factors. A wide variety of options such as the ASTM RBCA tiered approach, the API Decision Support Software, and a host of agency specific methods and commercial risk assessment software are all available. The optimization of a remediation project requires the right remediation technology coupled with the appropriate analytical framework. For groundwater remediation, the application of various "risk reduction" technologies can be classified as aggressive (pump and treat), moderate intensity (air sparging), low intensity (oxygen release compound-ORGY), and intrinsic (monitor only). The time frame of risk analysis will establish the proper risk reduction strategy. The selection process is inherently iterative, and the approach by which an optimal solution can be derived forms the basis of this article. A case study of a Texas site put these issues into context.

The current state of the art in the field of remediation of contaminated soil and groundwater sites involves the coupling of the movement of chemicals in air, soil, and water (transport) with the estimation of their effects once they have reached their "location" of interest. Risk estimation involves the averaging of chemical concentrations at receptor locations for varying periods of time and their pathways into the human body (human health risks) or the natural environment (ecological risks). Risk-based corrective action (RBCA) has become the latest attempt at merging transport and risk (ASTM, 1995). The application of RBCA involves a tiered approach starting with a screening look-up exhibit with default parameters (Tier I) to a complicated approach for difficult sites involving multi-parameter models and uncertainty analysis (Tier III). The American Petroleum Institute has developed the Decision Support Software (DSS) (API, 1994) to aid with the implementation of RBCA.