The Challenge of Model Implementation of Regulatory Models in Integrated Environmental Modeling Systems

This paper addresses an effort to develop a model for use both as a standalone regulatory model and as an operational module in an integrated modeling framework. As the state of the art of integrated environmental modeling advances, regulators have the opportunity to develop integrated modeling systems that have the capability of providing holistic overviews of potential environmental consequences. However because they are still bound by regulatory requirements, the implementation of regulatory models in integrated environmental modeling systems poses a number of special challenges. The component regulatory model must be able to be 1) documented as a separate entity, 2) implemented and used in a standalone mode, 3) meet the stringent quality control requirements for regulatory applications, 4) and for many applications have an expected operational lifetime on the order of decades. Implementation of a model (new or legacy) in integrated environmental modeling systems is usually accomplished either using direct coding or model wrapper approaches — both of which have major disadvantages for implementing regulatory models. During the process of developing a revised version of a regulatory facility emissions model for use in both standalone and integrated applications, a hybrid model implementation approach was developed. This hybrid approach enabled the authors to create an updated version of a regulatory model that has a single executable that performs both as 1) an independent standalone model and 2) a source-term module in an integrated environmental model system. Although the updated model is in the early stages of regulatory adoption, the experience to date indicate that the hybrid approach is meeting the special needs related to regulatory applications while still being operable in an integrated modeling environment.