A research vessel ran aground in a Hawaiian marine wildlife reserve on Sunday and appears to be leaking oil. Aerial surveillance of the crash site by the Coast Guard revealed a “rainbow-colored sheen” on the water, and the crew of the ship took actions to control the spread of a possible spill. What happens when your ship spills oil?
First, you report the spill to the Coast Guard, along with an explanation of what you plan to do about it. Big oil tankers must have a pre-approved “vessel response plan,” which includes the name of a private marine cleanup company that can get the right equipment to the scene within a few hours. If you don’t have a plan, the Coast Guard will hire a cleanup crew and send you the bill.
Big tankers are required to carry “spill kits” so their crews can start to mop up a slick before the pros arrive. Spill kits typically include pads of oleophilic (oil-attracting) material that soaks up the spill. These devices, called sorbent pads, come in many forms. Crews might use an 18-inch square that can be dabbed in the oil and then wrung out on board the ship; sometimes bales of hay are used.
The research vessel in Hawaii happened to have a “containment boom” on board, which it deployed not long after the crash. Containment booms are water-borne fences that keep the slick in one location. A standard boom consists of a flotation rope topped by a plastic wall that extends above the surface of the water. A weighted curtain hangs underwater to keep oil from leaking underneath the boom.
A ship’s crew can also use containment booms to divert the oil in one direction—perhaps away from the shoreline or a sensitive coral reef—or to push it into a thicker pool that’s easier to clean. The boom’s effectiveness depends on weather and water conditions: Rough waves can wash oil right over the top of the fence; fast currents can sweep it underneath. In heavy wind, the boom might be blown flat against the water’s surface.
Once a cleanup team has contained the oil, it can attempt to skim it off the surface of the water. Some skimmers work by separating the top layer mechanically; others use a sort of blotter or a suction mechanism. Very thick oils that resemble floating tar can be removed by hand, or with a pitchfork or shovel. Any of these mechanical methods for cleanup can be used immediately after a spill without prior approval from government officials.
Later on, workers can use chemicals or fire to clean up if the spill occurred far enough away from sensitive areas and if the government approves. “Dispersants” are EPA-approved chemicals—deployed from water cannons or from specialized booms—that break up the oil slick into tiny droplets that sink below the surface and wash away. If the oil slick isn’t too thin, and if it’s contained with a fire-resistant boom, workers can set it on fire. (This creates some local air pollution, which may be less dangerous than the water pollution.) The fire burns off most of the oil but leaves a viscous burn residue that either floats or sinks to the bottom—and must be picked up either way.
Cleanup crews have a few options to protect local shorelines and wildlife before they even come in contact with a spill. The land nearby can be pretreated with chemicals to prevent the oil from sticking when it washes ashore. Birds and other animals that might be affected can be “hazed”—frightened away—by high-tech scarecrows such as floating dummies, helium balloons, or propane scare cans, which fire off a frightening pop every minute or so.
Explainer thanks Lt. Eric Bauer of the United States Coast Guard.