Spill Tools Exercise:
The Dispersant Mission Planner

In this exercise, you'll estimate whether you have the resources to treat the slick with chemical dispersant and, if so, how long it would take. You have a single Bell 212 helicopter (a small, twin-engine helicopter) to apply the dispersant. The helicopter base is 20 kilometers away from the location of the slick. Here's how to use the Planner to make the necessary calculations:

1. Create and name a new scenario. To do this, click New Scenario, type in the name of your scenario, then click OK.

2. Assign the Bell 212 platform to the scenario (a "platform" is the kind of vessel from which dispersants will be applied). To do this, first click Go to Platform, then click on "Bell 212 - Suspended Bucket" in the list of platforms (you then can see information about the characteristics of the Bell 212). Next, click Scenario Assignments, click on the name of your scenario, click >>Move>>, then click OK. To return to your scenario, from the Scenario menu, choose the name of your scenario, then click Go to Scenario.

3. Fill out the boxes in the Planner to describe your spill scenario, as shown below. Type in Transit Distance (the distance the helicopter must fly to get from its base to the slick), Average Pass Length (the average downwind length of the slick), and the Volume and Area of the slick (the Planner then will automatically estimate Thickness), then set DOR (Dispersant-Oil Ratio) to 1:20 for this exercise (DOR is the ratio by volume of applied dispersant to spilled oil; it is based on manufacturers' estimates, and also is affected by the type of oil spilled, and other factors). Check that you've used correct units for all your inputs. The Planner will estimate the Pump Rate of the Bell 212 (the rate at which this helicopter can apply dispersant).

4. Click Calculate. The Planner will use the information you entered along with the characteristics of the Bell 212 to estimate the number of sorties the Bell 212 must fly, and the number of application passes it must make in order to apply dispersants to the entire slick. Here's what the various Mission Calculation estimates mean:

• Areal Coverage Rate is the rate at which the Bell 212 can apply dispersants, while it's spraying.
  
• Spray is the total amount of time during which dispersants could be applied.
  
• Transit is the total time spent transiting to and from the slick.
  
• Turns/Repositions is the total time spent in turning and repositioning the helicopter between passes.
  
• Resupply is the total time spent refueling the helicopter and resupplying it with dispersants.
  
• Total Time is the time required to treat the whole slick.
  
• Number of Sorties is the number of times the Bell 212 must transit to and from the slick.
  
• Number of Passes is the number of passes across the slick that the Bell 212 must make.
  
• Number of Fuel Stops is the number of times it must be refueled.
  
• Area/Sortie is the area of slick that can be treated with dispersants during each sortie.
  
• Volume/Sortie is the volume of oil that can be treated during each sortie.
  
• Dispersant Used is the total amount of dispersant needed to treat the entire slick.
  
• Oil Treated is the total volume of oil treated (this is the total volume of oil in the slick). The volume of oil treated will not equal the volume of oil dispersed, since dispersants are never 100% effective.

Spin-up time, the amount of time needed to load and send out the helicopter on its first sortie, is not included in these calculations.