Step 1. 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 to apply the dispersant (this is a small, twin-engine helicopter). 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).

Graphic: Snapshot of program window.

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:

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.

Questions

  1. How long will it take you to treat the entire slick with dispersant? ____ hours
  2. What percentage of the total time will be spent spraying dispersant? ____ %
  3. How much dispersant will you need to treat the entire slick, in bbl (barrels)? (Hint: consider DOR, the dispersant-to-oil ratio.) ____ bbl
  4. What difference would it make if the transit distance was only half as far (i.e., 10 km)? It then would take ____ hours to treat the slick, and ___ % of the time would be spent in transit or resupply.
  5. Is applying dispersant a realistic option, given the time and resources you have available?

 Check Your Answers


Scenario | Step 1 | Step 2 | Step 3

Revised: April 16, 2001
Office of Response and Restoration, National Ocean Service, National Oceanic and Atmospheric Administration