In 1993, BP made a business decision in the U.S. to develop a standardized approach for conducting soil and groundwater risk assessments across all ‘downstream’ activities (service stations through refineries). The rationale was that the company needed to ensure that the latest thinking on fate and transport, exposure, statistical analyses and toxicological criteria were adopted and applied uniformly its businesses. It would also help ensure that BP spoke with a consistent voice when approaching regulators and the community on this vital issue. Eventually it became clear that a software package containing embedded fate and transport models with intuitive user inputs offered the most convenient and flexible means of implementing this objective. This would enable the process to be readily standardized, communicated and transferred, while still allowing a risk application to be individually tailored to the regulatory regime of the particular business or country. By developing the code in-house, BP would also be able to rapidly adopt new algorithms or approaches (e.g. indoor air models), thus keeping the process evergreen. Versions 1.0 and 2.0 of the code were released in January, 1994 and August, 1995, respectively, with the former pre-dating the publication of the ASTM standard Risk-Based Corrective Action Applied at Petroleum Release Sites, commonly known as RBCA. Version 3.0, released in September, 1997, was a major upgrade that allowed back-calculations to be performed, i.e. soil and groundwater clean-up targets to be calculated for an input value of acceptable risk.

Version 4.0 of RISC has new features that give it even greater flexibility in assessing risk for the following scenarios:

• Irrigation pathways, i.e. water used for gardening but not for indoor usage
• Vegetables grown in contaminated soil
• Two new vapor models , where the vapors are allowed to biodegrade during transport through the unsaturated zone
• Models for surface water and sediment contamination from impacted groundwater and direct comparison with relevant national standards for these
  media
• The use of groundwater MCLs (maximum concentration levels) and surface water concentrations in addition to acceptable risk levels as the criteria for back-calculating clean-up targets
• The ability to calculate a site-specific target level (SSTL) for a TPH mixture using the site-specific measured concentrations of the TPH fractions detected in the soil
  

It is felt that Version 4.0 provides the latest and most complete package for calculating risk to human health and surface water. This version has been peer-reviewed by Arcadis, Geraghty and Miller in Cambridge, UK.