Sunday, June 06, 2010

Cleaning up is hard to do

The situation that has been unfolding in the Gulf proves, among other things, that having too many options can be a problem. That's especially true when all of them are at best imperfect, and some may indeed make matters even worse. Case in point for Comprehensive Anticipatory Design, if ever there was one.

There's really not much more than can be said about all this. We've backed ourselves into the proverbial corner and are faced with the contradiction of having more options and fewer choices at the same time. (GW)

Twelve (Imperfect) Ways to Clean the Gulf

New York Times
June 6, 2010

It’s been nearly seven weeks since oil from BP’s deep-ocean Macondo well began gushing into the Gulf of Mexico. Over that time, the public has, understandably, become increasingly frustrated with industry and government efforts to prevent damage to wildlife and wetlands. There is the growing sense — reflected in last week’s discussion of using nuclear weapons to stop the leak and a viral video about using hay to sop up the mess — that somehow, somewhere there are more innovative and effective measures for containing and cleaning up the oil.

But I can tell you, based on 21 years’ experience analyzing and observing oil spills, that the best minds in the business are already doing all they can. No special techniques that would work well to clean up the oil in this situation aren’t being tried or planned. There simply are no foolproof solutions.

Once oil spills into water, responders must race against time and the forces of physics, chemistry and biology to minimize the harm to life in the sea and on land. Oil spreads quickly into a hair-thin sheen and begins to evaporate, dissolve and travel with the winds and currents. Strategies to chemically disperse the oil, vacuum it away, sponge it up, burn it or divert it from especially sensitive areas all have their benefits — and their drawbacks.

So decisions about how to respond to a disaster of this magnitude involve evaluating the tradeoffs and the net long-term benefits to the environment. Efforts to spare marsh birds may hurt fish; a wetland may be protected, but only by diverting oil to a sandy beach; attempts to clean up the oil may involve trampling marshes or polluting the air.

The best strategy, of course, is to prevent spills in the first place. The second best strategy is to do everything possible to clean them up. And that seems to be what is happening.

The chart below summarizes the various cleanup efforts being undertaken or proposed in the gulf and along the coast.

— DAGMAR SCHMIDT ETKIN, an environmental risk consultant, who is advising the State of Louisiana and Mobile County, Ala., on the BP spill

1. Dispersants on water surface

Chemical dispersants sprayed from airplanes or boats break up 50 percent to 98 percent of oil on the water surface into smaller droplets so it’s easier for microbes to metabolize into harmless components.

Benefits: Chemically dispersed oil is one-tenth to one-hundredth as toxic as fresh oil to birds and other wildlife in wetlands, and results in less shore cleanup.
Challenges: Dispersants work best within a couple of days after oil enters the water.
Drawbacks: Dispersants drive oil down into the water, where it is toxic to fish and invertebrates and their larvae and eggs. Near-shore use is difficult because the oil has less area to disperse and dilute. Dispersants are too toxic to use near coral reefs and mangrove swamps.

2. Dispersants below the surface

This is an untested approach — used for the first time in the BP spill — in which dispersant chemicals are applied at the source of the leak.

Benefits: Theoretically can minimize the amount of oil that reaches the surface and ends up on the shore.
Challenges: Dispersants must be applied by remotely operated vehicles a mile deep, and it is difficult to measure how well they work at that depth.
Drawbacks: It is possible that breaking up the oil at this depth allows its more toxic components to dissolve into the water, harming the eggs and larvae of fish and invertebrates.

3. Burning

A fireproof boom is used to collect the oil into a relatively thick layer that is ignited with gels dropped from helicopters. Works best for freshly spilled oil far offshore.

Benefits: As much as 98 percent of the oil can be burned (leaving some residue on the surface) so that it is kept off the coastline and out of sensitive near-shore areas.
Challenges: It can be difficult to collect the oil in a thickness that is conducive to ignition, especially if currents make booms ineffective.
Drawbacks: Burning oil creates black plumes of smoke and particulates, and it cannot be done near populated areas.

4. Booms and skimmers

Thick layers of surface oil are herded into floating booms, where skimming devices vacuum the oil into storage barges or tanks.

Benefits: Oil is recovered with little or no damage to the environment.
Challenges: Getting the equipment in place before winds and currents spread the oil, especially in places where there are fast currents and the booms are ineffective.
Drawbacks: A labor-intensive strategy that rarely recovers more than 5 percent to 10 percent of the oil. (As much as 25 percent can be recovered in sheltered areas with very calm water.) Large volumes of skimmed water often contain little oil. The collected oily water must be stored, cleaned as much as possible and ultimately disposed of.

5. Sorbent materials

Mats and pads that act like sponges are applied to the water surface in calm areas with low concentrations of oil. Near the shore, sausage-like booms filled with sorbent materials are placed in the water to soak up surface oil.

Benefits: A non-invasive approach that requires no large machinery and can keep small amounts of oil out of sensitive areas.
Challenges: Effective placement of materials can be difficult.
Drawbacks: Oil-soaked pads and mats must be replaced (at least every few days), and disposed of as hazardous waste. The large number of people needed to place the materials can harm marshes through trampling.

6. Protective/deflective booming

Booms are placed to deflect oil from wetlands, bird nesting habitats and other sensitive shoreline or near-shore areas.

Benefits: Can be effective in places where tidal currents are not too fast.
Challenges: Booms often need to be shifted with the tides, and proper placement and installation can be tricky.
Drawbacks: Oil is diverted to other areas where it can do damage.

7. Marsh flushing

Seawater is pumped through the marsh to dilute the oil sticking to grasses, enhancing tidal movements to promote natural recovery.

Benefits: Can dilute and remove high concentrations of oil.
Challenges: Placing pumps and hoses in dense marshes can be difficult.
Drawbacks: The flushing action may take weeks to months.

8. Marsh grass cutting

Marsh grasses in heavily oiled areas are cut and removed.

Benefits: May prevent oil from migrating to other sensitive areas nearby. Challenges: Bringing people and equipment into a marsh often causes more harm than the oil itself. And the oiled grasses and debris must be disposed of.
Drawbacks: Areas where grasses are cut often take much longer to recover than oiled areas that are not cut.

9. Mechanical removal

Bulldozers and other heavy machinery are brought in to remove oiled sediment, grasses, and debris. Appropriate for heavily oiled sandy beaches. In marshes, it makes sense only if all other methods have failed.

Benefits: May prevent the oiling of sensitive areas nearby.
Challenges: The risk of damaging marshes is great, and oiled grasses, sand, and debris must be disposed of.
Drawbacks: Marshes can take a long time to recover from damage caused by heavy equipment.

10. Natural recovery

Tides and waves break down oil on the water surface, or on the shoreline in marsh areas that can otherwise be damaged by aggressive cleaning.

Benefits: No environmental side effects, and it’s always possible to try alternatives later.
Challenges: It can be difficult to convince the public that it’s wise to do nothing, and the effectiveness of the strategy may not be known for months or years.
Drawbacks: May not be completely effective, especially if the wave action is not robust or the oil is especially heavy.

11. Manual Shoreline Cleanup

On moderately oiled sandy or pebbly shorelines, people use shovels, rakes and gloved hands to pick up tar balls, oily patches and debris.

Benefits: No heavy equipment is needed, and unskilled workers can participate.
Challenges: Workers must be trained to recognize oil and reduce personal exposure. The collected oily debris must be disposed of.
Drawbacks: The work is labor-intensive and time-consuming.

12. High-pressure washing

High-pressure hoses are used to spray oil off seawalls, piers, boats and other hard surfaces, and the oil is then collected with skimmers, vacuum pumps, or spongy materials.

Benefits: An effective way to clean off lighter oils.
Drawbacks: On shorelines that support marine life, the damage from high-pressure washing would be greater than that from the oil itself.

Jon Han is an illustrator and Maye Webb is a graphic designer.


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