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Number of LNG <br />ISOs Derailed (X) 0 1 2 3 4 5 6 7 8 9 10 <br />Probability 59% 17% 3.7% 3.7% 3.0% 2.1% 2.7% 2.5% 2.3% 2.4% 2.4% <br />Finally, the loss of containment (LOC) was modeled using a probability versus quantity released <br />relationship developed from analysis of historical PHMSA data. Since data are sparse for a <br />0 ISO containers in rail accidents, pressure tank car data was used as an analog to represent (4) <br />(4) <br />pressurized ISO container failure probability. The probabilities are shown in the table below. <br />The release scenario probabilities were combined with the probabilities of derailment for <br />multiple cars in an event tree model to estimate the quantity released for each distinct outcome in <br />the accident model. <br />LOC probability from PHMSA pressure tank car incident data and equivalent <br />release scenario for LNG ISOs. <br />Quantity Released in gallons Probability Release Scenario <br />=< 100 0 958 No Release <br />100 < x =< 1,000 0.014 1/2 -inch Leak <br />1,000 < x =< 30.000 0.025 2 -inch Leak <br />> 30,000 0.003 Catastrophic <br />E.2.2 Mainline Risk <br />The risk posed by the LNG ISOs along the mainline was evahiated by making conservative <br />assumptions in order to bound the maximum risk of all route options. The results are reported for <br />the highest mainline population density value of 11,800 people per square mile. For regions of <br />the mainline with lower population, the calculated risk will be less than that presented. Two <br />speed ranges, low speed <25 mph and high speed >25 mph to <60 mph, were applied in the <br />model to demonstrate the effects of train speed restrictions. Seven different train configurations <br />were evaluated to demonstrate the effects of blocking LNG ISOs into sequential car groupings. <br />For example, the baseline case (C-1) placed ® LNG ISOs in sequence from train position I to <br />® This configuration poses the highest risk since all LNG ISOs are in sequence, all may be (4) <br />) (4) involved in an individual derailment (high speed only), and the highest probability <br />of derailment is at the front of the train. As a comparison, train configuration C-2 places the <br />LNG ISOs in sequence from train position I to H The table below compares the calculated <br />risk metrics for (4) low speed and high speed movement of these train configurations along the <br />1308194.001- 5691 Ax <br />