5.2.3.4 The spacing of an LNG tank impoundment to the property line that can be built
upon shall be such that, in the event of an LNG spill as specified in 5.2.3.5, an average
concentration of methane in air of 50 percent of the lower flammability limit (LFL) does not
extend beyond the property line that can be built upon, in accordance with calculations using
one of the following:
(1) The model described in GRI Report 0242, “LNG Vapor Dispersion Prediction with
the DEGADIS Dense Gas Dispersion Model”
(2) A model that incorporates the following:
(a) Physical factors influencing LNG vapor dispersion, including, but not limited to,
gravity spreading, heat transfer, humidity, wind speed and direction,
atmospheric stability, buoyancy, and surface roughness
(b) Validation by experimental test data appropriate for the size and conditions of