Application of CHARM®for studying chemical dispersion due to accidental release

Abstract

The EPA risk management program (RMP, Rule 112r) requires hazard assessment and emergency response programs. To assure that you have adequate resources and that plans are well organized for any contingency, you need to plan for emergency response. Should such an accident occur, you need real time data to guide the response activities (CHARM – Software, when realism counts, www.charmmodel.com). An example given in this paper helps the planner to understand how dispersion modelling can help to guide response activities. There are two versions of CHARM; the first deals with a flat terrain and second deals with a complex terrain. Both use different types of algorithms. In a flat terrain, release is simulated as it simulates a series of puffs, while in a complex terrain, release is determined by the fundamental equations of Navier-Stokes. The CHARM software is an application that calculates the movement and concentration of airborne plumes from released chemicals; thermal radiation impacts from fires; and overpressures from mechanical and vapour cloud explosions. In this paper the complex terrain version of CHARM is being used and instantaneous release of 50 kg Chlorine is being considered to explain the simulation process. It is worth mentioning that hazard assessment could be done in a cost effective manner using data mostly available free of cost, like satellite images, digital elevation model, digital surface model, chemical properties of released chemicals, surface roughness data and meteorological parameters.