Chemical dispersants that break an ocean oil slick into tiny droplets, scattering the oil through the water column in a similar manner to dish soap removing grease from dirty plates, have long been part of the inventory of techniques available to respond to an offshore oil spill disaster. The idea is that oil consuming microbes in the water column will rapidly destroy the minute oil particles, thus greatly accelerating the destruction of the oil pollution.
But the use of dispersants has also proved controversial. Some people have raised questions over the potential toxicity of the dispersant chemicals. And some have questioned whether dispersant use is more a case of “out of sight, out of mind,” as an oil slick disappears from the sea surface, rather than a means of removing spilled oil from the sea.
Proposed Alaska policyAt a session of the Alaska Forum for the Environment on Feb. 6 government officials and others spoke about the issues relating to dispersant use in Alaska waters and about a new proposed Alaska dispersant policy that the Alaska Regional Response Team, or ARRT, is proposing. The proposed policy includes the implementation of a dispersant pre-authorization zone some distance offshore the Aleutian Islands and the Alaska Peninsula, and around the Cook Inlet and Prince William Sound regions. Within this zone the use of dispersants to respond to an oil spill would be allowed, albeit with some safety checks, without having to obtain a dispersant permit, thus improving the efficiency with which a dispersant use decision could be made.
The Coast Guard and the Environmental Protection Agency are engaged in a public outreach exercise, gathering public comments about the proposed policy changes. Impacted communities will also have opportunities to recommend areas where the use of dispersants should be restricted within the pre-authorization zone. The ARRT is the advisory board that coordinates the federal planning of oil spill contingency arrangements in Alaska.
In addition to improving the efficiency of decision making, the implementation of a pre-authorization zone would have the effect of forcing shipping companies plying the waters around southern Alaska to have dispersants available, should a shipping accident cause a significant oil spill, the Coast Guard has said. The Coast Guard is particularly concerned about the potential for a marine accident, either involving a vessel carrying Alaska crude oil or a vessel holding crude oil or heavy fuel oil on the international sea route that passes close to the Aleutian Islands.
The Coast Guard sees mechanical oil recovery using boom and oil skimmers as the spill response approach of choice, but wants to be able to use dispersants if necessary.
A necessary updateMark Everett, the Coast Guard co-chair of the ARRT, told forum participants that the proposed dispersant policy changes would update existing Alaska policies that have become outdated.
“We really want the best policy fit for Alaska and Alaskans,” Everett said, adding that the National Contingency Plan, the set of federal regulations governing regional response plans, requires that regional plans incorporate advance planning for the use of alternative response techniques such as dispersant application. And, under the current policy, the Coast Guard cannot regulate industry’s dispersant capability, Everett said.
Chris Field, the ARRT co-chair from the EPA, emphasized the desire of the ARRT to gather as much public input as possible — he particularly stressed the importance of the involvement of Native tribes and traditional knowledge in emergency planning and response.
”We want to get as much input as we can before we make a decision on this dispersant policy and pre-authorization plan,” Field said.
A last resortRichard Bernhardt, an official from the Alaska Department of Environmental Conservation, commented that the high number of harmful toxins in oil is particularly problematic when oil is spilled into the environment. Once oil is in the water, dispersants, with toxicity far below that of oil, can be a useful last resort, keeping oil out of bays along the coastline and enabling responders to deal with the oil offshore, should other response techniques fail to contain the spill, he said.
“When we can’t go out with ships and skimmers and boom and collect that (oil) mechanically, then we have to look at what we’re left with,” Bernhardt said. Having dispersants in the toolbox is an important alternative, he said.
Studies have shown that the effectiveness of dispersants ranges from 30 to 80 percent, depending on the prevailing conditions, Bernhardt said. A dispersant application quickly causes a spike in hydrocarbon concentration in the upper meter of the water column, but that spike drops off dramatically after about five hours, he said. After five to eight days 90 to 95 percent of the dispersed oil will likely be gone, although the rate of degradation after that is very low, he said.
Dispersants would never replace the use of mechanical recovery, would only be applied at an adequate distance offshore and would not be used in high winds. Regulations require pilot testing of dispersant use before a full-scale dispersant application, Bernhardt said.
An environmental tradeoffDoug Helton, operations coordinator for the National Oceanic and Atmospheric Administration’s Office of Response and Restoration, commented that an oil spill is a bad situation with no good outcomes.
There is an environmental tradeoff involved in dispersant application, in that the dispersant changes the behavior of the oil in the water, Helton said. It is a question of what is “the least bad choice” in choosing techniques to deal with the spill — the use of dispersants as a spill response technique is relatively rare and is only effective within about two days of the spill happening, he said.
After dispersant is applied, the concentration of oil in the water moves quite quickly from high to lower values, but there is a pulse of oil in the water column, he said.
Helton particularly cautioned about the need for careful and critical reading when reviewing the many published studies on the use of dispersants following the Deepwater Horizon disaster in the Gulf of Mexico. Some of these studies appear to have involved poorly conducted research, in some cases creating misleading headline news, he said.
“We know that public concerns still persist and there’s good reason for it, which is why any time we’re going to use dispersants it’s going to be a very thoughtful, careful decision,” Helton said.
Major improvementMark Swanson, executive director of the Prince William Sound Regional Citizens Advisory Council said that the proposed new dispersant policy represents a major improvement over the previous policy.
“There’s no pre-authorization within 24 miles of the coast … there are incident-specific requirements to consult with resource agency trustees,” he said, while also commenting on some other proposed stipulations, such as considerations of potential impacts on maritime species and habitats, and detailed reporting requirements.
Major concernsHaving conducted research into dispersant use over the past 20 years, the Regional Citizens Advisory Council worries about the technique. Major concerns relate to the effectiveness of the technique in Alaska’s low temperatures and the toxicity of the dispersant chemicals, Swanson said.
The toxicity data for the chemicals only comes from short-term testing on species that are unrepresentative of the Alaska environment, Swanson said. And the prevalence of relatively fresh glacial melt water at the sea surface around Alaska raises questions over the depths at which the mixing of dispersant-treated oil would take place. There are also unanswered questions over the long-term versus short-term impacts of the dispersants, and over the impact on human health, he said.
Native tribes and the government agencies responsible for environmental protection must be consulted over dispersant use and must have equal recognition in the consultation process, Swanson said.
“We want good guidance and well-informed decision making,” he said.
Ocean currentsJohn French, a consultant with Pegasus Environmental Solutions, questioned whether during a spill response there would be time to take all of the actions set out in checklists associated with dispersant use in the proposed dispersant policy.
He particularly expressed concern about the way in which ocean currents around the Aleutian Islands and through the Bering and Chukchi seas might carry dispersant-treated oil north up the Alaska coastline, through biologically productive seas, rich in nutrients that support fish and other wildlife. People do not have a good handle on the impact of dispersed oil on fish, French said.
The real question for dispersant use is what happens to the most toxic components of the oil, the components that may degrade most slowly, French argued.
Some coastal village residents attending the forum also expressed concern about the potential for pollution from a dispersed oil spill moving northward up the Alaska coast.