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Spill Tools / Step 1 / Answers
Step 1 - Answers
Here's how the Dispersant Mission
Planner should look, once you've entered all information and clicked Calculate:

Answers
- How long will it take you to treat
the entire slick with dispersant? This is the Total Time, 4.2 hours.
- What percentage of the total time
will be spent spraying dispersant? This is the time spent spraying dispersant
(Spray), divided by the Total Time (spent spraying, transiting, resupplying,
repositioning, and so on), multiplied by 100%: (0.5 hours / 4.2 hours) * 100%
= 12%
- How much dispersant will you need
to treat the entire slick? Since DOR, the dispersant-to-oil ratio, is 1:20
for this scenario, you must apply 1 bbl of dispersant to every 20 bbl of oil
in the slick. The total volume of oil in the slick is estimated to be about
1,000 bbl, so your answer is 1000 bbl / 20 = 50 bbl.
- What difference would it make
if the transit distance was only half as far (i.e., 10 km)? To answer this
question, just type in a new Transit Distance of 10 kilometers, then click
Calculate (leave all other aspects of the scenario unchanged). You'll find
that it would take 2.8 hours to treat the slick (Total Time), with about 18%
of the time spent spraying dispersant ([Spray / Total Time] * 100%), and 100%
- 18% = 82% of the time spent in transit, turning/repositioning, and resupply.
- Is applying dispersant a realistic
option, given the time you have available? You have an estimated 10 hours
before the slick is predicted to reach the sensitive site. Since treating
the slick is estimated to take just 4.2 hours, applying dispersant is a realistic
option, as long as
- little time is needed for spin-up
(loading and sending out the helicopter on its first sortie).
- you have reason to believe that
the oil would be effectively dispersed before the slick reaches the sensitive
site. Environmental conditions greatly influence how quickly and effectively
oil is dispersed once dispersant has been applied.
Compared with other application platforms,
the Bell 212 helicopter has a relatively small cargo capacity and relatively
narrow swath width (width of the area covered by dispersant during a pass).
If you had available an aircraft with more capacity and a wider swath width,
such as a C130, you would be able to apply dispersant to this entire slick sooner,
using fewer sorties. To see this difference, try repeating this exercise using
the C130 as your application platform.
Revised: April 16,
2001
Office of Response and Restoration, National Ocean Service, National Oceanic
and Atmospheric Administration