Numerical methods to predict groundwater flow and contaminant fate and transport have been available to the industry since the initial introduction of MODFLOW by the USGS in 1988. Since that time both finite difference and finite element methods have grown in availability, with both 2-D and 3-D capability. Communicating model output to both regulatory agencies as well as the lay stakeholder is essential to model acceptance, but identifying model vulnerability and potential for error is often overlooked. This session will provide a platform for those who use models and other numerical tools to showcase their work and report on lessons learned.