Profesor

The CAMEO® Software Suite

ALOHA
December 2011

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Example Scenarios

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U.S. Environmental Protection Agency Office of Emergency Management Washington, D.C.

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National Oceanic and Atmospheric Administration Office of Response and Restoration Emergency Response DivisionSeattle, Washington

This document contains three step-by-step fictional ALOHA example scenarios. You can complete the first two scenarios using only ALOHA. To complete the third scenario, you’ll also need the latest MARPLOT mapping application.

ALOHA Examples
Example 1: A Tank Source (Puddle and Pool Fire) ........................................................................ 3 Part 1:Modeling a Toxic Vapor Cloud............................................................................... 3 Part 2: Modeling a Pool Fire ............................................................................................. 15 Example 2: A Tank Source (Multiple Scenarios) ......................................................................... 20 Part 1: Modeling a BLEVE............................................................................................... 20 Part 2: Modeling a Flash Fire or Vapor Cloud Explosion ................................................ 28 Part 3: Modeling a Jet Fire ................................................................................................ 37 Example 3: A Direct Source and a MARPLOT Map................................................................... 40

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Example 1: A Tank Source (Puddle and Pool Fire)
In a small industrial park outside Baton Rouge, Louisiana, a 500-gallon, 4-foot-diameter, vertical tank contains liquid benzene. On August 20, 2006, at 10:30 p.m. local time, a security guard discovers that liquid is leaking out of the tank through a 6-inch circular hole located 10 inches above the bottom ofthe tank. He also sees that the liquid is flowing onto a paved area in the industrial park. The guard thinks that the tank has just been filled that evening. The temperature on scene is 80°F, with the wind from the southwest at 7 miles per hour (as measured at a height of 10 meters by a fixed meteorological tower at the site). The sky is more than half covered by clouds and the humidity is about75 percent. A thunderstorm is approaching from the southwest. There is no low-level inversion. There are very few buildings in the industrial park and a large grassy field is located to the northeast of the industrial park. The Local Emergency Planning Committee has requested that on-scene responders use ERPG-2 concentrations to define the toxic endpoints in their analysis of benzene hazards. Inthis example scenario, you’ll determine: 1. Distance to the ERPG-2 level if the puddle evaporates and forms a toxic vapor cloud. 2. Thermal radiation threat if a lightning strike ignites the puddle and forms a pool fire.

Example 1, Part 1: Modeling a Toxic Vapor Cloud
Choosing a Location and a Chemical
1. Start ALOHA. (In Windows, click the Start button, point to Programs, then choose theALOHA item. On a Macintosh, double-click the ALOHA program icon located in the ALOHA folder.) 2. Read the list of ALOHA’s limitations (click for more details), then click OK.

3. Select Location from the SiteData menu. A Location Information dialog box appears with a list of the names of cities included in ALOHA’s location library. 4. The industrial park is located outside Baton Rouge, Louisiana.Type the characters ba to quickly move to the section of the list containing names beginning with “ba.” Scroll down a little farther until you see BATON ROUGE, LOUISIANA. Click on this name to highlight it, then click Select.

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5. Select Date & Time from the SiteData menu. A Date and Time Options dialog box appears. 6. The release occurs at 10:30 p.m. on August 20, 2006. Select the Set...