Chemical Dispersant Exercise

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Fate Exercises: Chemical Dispersant

Incident

At 0700 on April 4th, 2017, a collision occurred between a shrimp boat and a freighter about 30 miles southeast of Galveston, Texas at 28° 55.9’N, 94° 21.5’W. Initial reports indicate 315 bbls of IFO 180 were lost. The National Weather Service marine forecast indicates that the winds will be from the southwest at 15 knots for the next 36 hours.

Approval has been given for the application of dispersants. Corexit 9500 has been loaded onto a DC-4, and the aircraft is on standby in Houma, Louisiana. Unfortunately, the aircraft has a mechanical problem with the dispersant equipment. The contractor indicates that they will be able to disperse the next day.

Commander Jones would like to know if the oil will emulsify to the extent that dispersants will not work.

Model Input

Begin on the home page by clicking “Oil Fate Wizard” under “Weathering Only”. Or, from the Setup View, click the “New” menu and select “Oil Fate Wizard”.

Scenario Settings

  1. Click Scenario Settings

  2. Give the incident a name

  3. Set the start time: 0700 on April 4th, 2017

  4. Set the model duration to 2 days

  5. Click Save

Oil:

IFO 180.

  1. Click Oil to open the ADIOS Oil Database

  2. There are multiple ways to find an IFO-180 in the database. Here are a few options:

    • type “IFO” in the search box

    • type “180” in the search box

    • select Residual Fuel Oil in the “Type” selection

  3. You probably want to select the oil with the highest score unless you know it’s a more specific oil.

  4. Click the oil name to show you the details of the oil.

  5. Click “Download” to select the oil to use in GNOME.

Spill:

Instantaneous release of 315 bbls.

  1. Click “Spill” to set the spill properties

  2. Select “Instantaneous Release”

  3. Set Amount Released to 315

  4. Make sure the units are set to “bbl”

  5. Load the oil file that you downloaded from the ADIOS Oil Database

  6. Click Save

Water:

Water temperature has significant effects on evaporation rates.

Ideally, you would find a field data value for water temp in the region, perhaps from the NDBC web site (for the US):

http://www.ndbc.noaa.gov/

As of April 4, 2017, the water temp south of Mobile is 75.6 F (station 42012).

Or use an approximation for the season

  1. Click Water

  2. Enter 75.6 and choose F from the popup menu.

  3. Select 32 psu (avg. oceanic) from the Salinity popup menu

  4. Select 5 mg/l (ocean) from the Water Sediment Load popup menu

  5. Leave Wave Height at “Compute from Wind (Unlimited Fetch)”

Wind:

Winds will be from the southwest at 15 knots for the next 36 hours

  1. Click Wind

  2. Select the Constant Wind Tab

  3. Set the direction to “SW”

  4. Set the speed to 15 knots

  5. Click Save

Run the model

Click “Solve”

Discussion

Commander Jones would like to know if the oil will emulsify to the extent that dispersants will not work.

IFO-180’s do not normally emulsify, however, the oil may weather and become very viscous so that dispersants may be less effective. You can address this issue by using the Oil Viscosity Graph.

  1. Click the Weathering tab to see the oil properties graphs.

  2. Click the Viscosity tab to see how the viscosity of the oil is changing with time.

  3. Notice that after about 8 hours, dispersability is restricted. The effectiveness of dispersants will be questionable. Ask your SSC for further guidance.