Step 2. The In-Situ Burn Calculator

In Part 1 of this step, you'll estimate the time needed to burn part of the slick. For equipment, you have two vessels that you can use to tow fire-proof boom in order to capture and burn part of the oil from the slick. In Part 2, you'll estimate the extent of the smoke plume generated by the burn, and determine whether it might pose a hazard to people downwind of the burn.

Part 1. Predicting Burn Performance

Photo: a burn generates a thick plume of smoke.In an in-situ burning operation, two vessels towing a U-shaped, fireproof boom approach an oil slick. They collect part of the oil within the boom, tow it a safe distance away from the rest of the slick, and then ignite the oil within the boom (as shown at right). This operation is typically repeated, so that a series of burns is made.

Follow the steps below to use the Burn Calculator to predict how well this operation would work for this scenario, if you have a 300-foot fireproof boom with a draft of 18 inches, which can be towed at a maximum rate of 1 knot to create a swath 30 feet wide.

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

2. Click the Single Release tab, then the Direct tab (if necessary), so that the boxes for a single release scenario are visible (you would click the ADIOS tab if you wanted to use output from the ADIOS weathering model in your calculations).

3. Fill out the boxes in the Calculator to describe your spill scenario, as shown below. Type in the Volume and Area of the slick, and choose units (the Calculator then will automatically estimate Thickness). Under the Boom Parameters heading, type in a boom Draft of 18 inches, the vessels' Tow Speed of 1 knot, your planned Offset Distance of 1500 feet (this is the distance you will pull the boom away from the main slick before igniting the oil within it), and the boom's total Length of 300 feet.

The Calculator then estimates the Swath (the width of the U-shaped area enclosed by the towed boom), the Area enclosed by the boom and the Capacity of the boom (the amount of oil that can be enclosed within the U-shaped boom during one pass through the slick; generally, capacity is reached when about one-third of the area within the boom is filled with oil to a depth of about one-third of the boom draft).

Graphic: Program window snapshot

4. Click Calculate. The Calculator will use the information you entered to estimate

Questions

  1. How long would it take to complete each burn (account for filling, offsetting, and redeploying the boom as well as burning the oil)? ____ hours
  2. How much of the oil in the slick would be burned during a single burn? (Hint: Consider the Effective Burn rate) _____ bbl
  3. How many burns of this size would you need to burn off all the oil in the slick? _____
  4. How long would it take to burn the entire slick? _____ hours
  5. Is burning a realistic option, given the time you have available?

 Check Your Answers for Part 1


Part 2. Predicting the Smoke Plume

Photo: a smoke plume can extend substantial distances downwind.An in-situ burn generates a plume of smoke, which can potentially create a visibility hazard to boats and aircraft, and a health hazard to people in the area. An example is shown at right.

You'll now use the In-Situ Burn Calculator to estimate the extent of the smoke plume generated by your burn operation, given the following conditions:

Use the standard Level of Concern (LOC) of 150 micrograms of smoke particles per cubic meter of air (this is the maximum concentration of smoke particles in the air to which members of the general public can be exposed, for up to 1 hour; this level is recommended by the National Response Team; here are more details).

Follow these steps:

1. If necessary, repeat the steps in Part 1 to reestimate the burn rate and duration. If you have not modified your scenario from Part 1, continue to 2.

2. Click the Plume Estimate tab.

3. Fill out the boxes in the Calculator to describe your scenario, as shown below. Type in the Wind Speed and the Oil Density, and choose units. From the atmospheric Stability menu, choose Day or Overcast Night. Click Standard LOC, then type in the Air Temperature and choose units.

Graphic: program window snapshot

4. Click Gnd Level Conc. to view a graph of the estimated smoke particle concentration at ground level out to 20 kilometers (12 miles) directly downwind of the burn, in micrograms per cubic meter, during the time that the burn is proceeding at a steady rate. On this graph, a horizontal dashed line represents your LOC, while a second dashed line represents estimated concentrations. When you have finished viewing the graph, click the button in the lower right corner of the window.

5. Click LOC Plume to view a diagram showing a side view of the predicted smoke plume, out to 5 kilometers directly downwind of the burn. On the diagram, the area enclosed by the bent-over oval figure represents the area where smoke particle concentrations are predicted to exceed your LOC, during the time that the burn is proceeding at a steady rate. When you have finished viewing the graph, click DONE.

Questions

  1. Would people in boats downwind of the burn be exposed to smoke concentrations above the LOC?
  2. What about pilots in small aircraft? (What aircraft might be in the area, and what might they be doing?)

 Check Your Answers for Part 2


Scenario | Step 1 | Step 2 | Step 3

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