(108e) Fully Integrated GIS Based LNG Consequence Model for Spills on Water

LNGMAP, a fully integrated geographic information system (GIS), has been developed to predict the fate and transport of spills of LNG on water. The model contains separate algorithms that are linked together to represent processes that affect LNG once it is released on water. LNGMAP uses spill geometry, environmental data forcing (currents and wind) and physical-chemical properties to simulate fate processes over time after the release, including: (1) time dependent release rate, (2) spreading, (3) transport on the water surface, (4) evaporation from the water surface, (5) transport and dispersion in the atmosphere, (6) and, if ignited, burning and associated radiated heat fields. LNGMAP is a Lagrangian model, when LNG is released it is broken into many tiny individual masses of LNG called spillets. These fate processes then act on each individual spillet. At each calculation time the spillets are integrated together to report the temporal evolution of surface thickness of LNG, vapor concentrations in the atmosphere and thermal intensity on a map-based display.

Due to the lack of field experiment using significant amounts of LNG, LNGMAP was validated by comparisons to predictions of models developed by ABS Consulting and Sandia for time dependent point releases from a draining tank, with and without burning. To illustrate the model predictive capability for realistic emergency scenarios this paper presents results for a tanker entering Block Island Sound. Three hypothetical cases were studied: the first assumes the vessel continues on course after the spill starts, the second that the vessel stops as soon as practical after the release begins (3 minutes), and the third that the vessel grounds at the closest site practical. This model output can be used by decision makers to help select the best course of action to minimize consequences.