Dispersants
Chemical dispersants are substances applied to spilled oil that disperse oil into the water column rather than leaving it floating on the surface in a slick. The council has long endorsed mechanical recovery as the primary tool to combat an oil spill. Unlike dispersant use, mechanical recovery with booms and skimmers removes oil from the water.
Current state and federal laws and regulations hold that dispersants should be used only if it is clear that mechanical cleanup methods such as booming and skimming won't work.
PWSRCAC Position on Dispersants
After years of promoting research and testing to increase knowledge about dispersants and the environmental consequences of their use, the council in 2006 adopted a position against the use of dispersants in the Exxon Valdez oil spill region. PWSRCAC's position paper: Prince William Sound Regional Citizens' Advisory Council Dispersant Use Position Paper. May 2006. (pdf/20KB)
PWSRCAC's Scientific Advisory Committee (SAC) Dispersant Position Paper – April 26, 2006 (pdf/42KB)
PWSRCAC's Chemical Dispersants Program 1997 – April 2006 (pdf/67KB)
See also the council's news release on dispersants position.
Among the council's concerns is the scarcity of reliable scientific data about the efficiency, toxicity, and persistence of dispersants and dispersed oil in Prince William Sound/Gulf of Alaska conditions. There has not been a conclusive demonstration that chemical dispersants work in the extremely cold waters of Prince William Sound. Although effort has been put into evaluating chemical dispersant use over the last 30 years, a good portion of this effort was conducted by the formulators of dispersants and not by independently funded surfactant scientists.
The council seriously questions dispersant use based upon recent photoenhanced toxicity concerns and other outstanding questions regarding long-term effects. Photoenhanced toxicity occurs when a chemical becomes more toxic if exposed to the ultraviolet light present in natural sunlight.
Regulations and Guidelines
The Alaska Regional Response Team (ARRT) is an advisory board to the federal and state on-scene coordinators. It provides federal, state, and local governmental agencies with means to participate in response to pollution incidents. The ARRT also provides the guidance document for the use of dispersants in Alaska.
ARRT Oil Dispersant Guidelines for Alaska: Spill responders must use these guidelines when considering the use of dispersants (pdf/328KB on ARRT Web site)
For more information on regional dispersant use policies around the nation, visit the United States Coast Guard's dispersants page online.
Effectiveness Testing
Are Dispersants Effective in Alaskan Waters?
The council contracted with the National Oceanic and Atmospheric Administration’s (NOAA) Auke Bay Laboratory to test the effectiveness of dispersant Corexit 9527 and Corexit 9500 in dispersing various states of weathered Alaska North Slope (ANS) crude oil using a combination of realistic subarctic salinities and temperatures. At temperatures and salinities most common in the marine waters of Alaska, the dispersants were less than 10 percent effective at dispersing fresh or weathered ANS crude in these laboratory tests.
The Effectiveness of Corexit 9527 and 9500 in Dispersing Fresh, Weathered, and Emulsion of Alaska North Slope Crude Under Subarctic Conditions. Adam Moles, Larry Holland, and Jeffrey Short. April 2001. Published in Spill Science and Technology. December 2001. Volume 7, Issues 5-6, pp. 241-247. (pdf/795KB)
Stability and Resurfacing of Dispersed Oil. Merv Fingas, Environment Canada. November 2005. (pdf/15.7MB) Stability and Resurfacing of Dispersed Oil--One-page Summary (pdf/14KB)
Wave Tank Testing
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Oil behavior is tested in a wave tank. Photos by Lisa Ka'aihue, PWSRCAC. |
The Ohmsett dispersant test tank is a 2.6-million-gallon open-air saltwater test tank on the Atlantic seacoast and operated by the U.S. Minerals Management Service. It was created to test mechanical oil spill recovery equipment. Crude oil can be put on ocean water in the Ohmsett tank and sprayed with dispersants with little risk of release to the natural environment.
In recent years, the council has sent representatives to observe Ohmsett cold-water dispersant tests. The council has disagreed with many of the test parameters, and is concerned that tests like these have the potential for determining policies for dispersant use. PWSRCAC is working with industry and regulators to develop improved methods and procedures for dispersant testing.
Oil Spill Dispersant Effectiveness Testing in OHMSETT: February-March 2006. Merv Fingas, Environment Canada and Elise DeCola, Nuka Research & Planning. October 2006. (pdf/1.9MB)
Observers' Report: MMS Cold Water Dispersant Tests, Ohmsett Testing Facility, 28 February-3 March 2006. Elise DeCola, Nuka Research and Planning Group; Merv Fingas, Environment Canada. June 2006. (pdf/2MB)
A Survey of Tank Facilities for Testing Oil Spill Dispersants. Merv Fingas, Environment Canada. May 2005. (pdf/4.9MB)
Heated Oil and Under-Reported Dispersant Volumes Mar MMS/Exxon Cold Water Dispersant Tests at Ohmsett. Prince William Sound Regional Citizens’ Advisory Council. July 2004. (pdf/190KB)
Report on Visit to Ohmsett to Observe Exxon/MMS Cold-Water Dispersant Tests. Stan Jones, Prince William Sound Regional Citizens' Advisory Council. March 2002. (pdf/1.9MB)
A White Paper on Oil Spill Dispersant Effectiveness Testing in Large Tanks. Merv Fingas, Environment Canada. November 2002. (pdf/192KB)
Two major concerns emerged from the 2002 dispersant effectiveness tests in cold water conducted at Ohmsett. The council is concerned that oil used in the cold water tests was heated far above ambient water temperature before being dispersed, and that dispersant volumes in those tests were under-reported.
The following report is broken into sections due to its large file size:
Main report: Field Notes and Critical Observations from the OHMSETT Heavy Oil dispersant Trials, October 13-16, 2003. By James R. Payne, Ph.D., Payne Environmental Consultants, Inc. (pdf/1MB)
Appendix A: Figures and Photo Documentation
Appendix A pages 1-50 (pdf/10MB)
Appendix A pages 51-100 (pdf/8.7MB)
Appendix A pages 101-150 (pdf/10.3MB)
Appendix A pages 151-178 (pdf/4.8MB)
Appendix B: SL Ross/OHMSETT Operating Plan (pdf/1MB)
Field Testing
Issues that must be considered when determining appropriate field tests of dispersants include the ability to determine a mass balance, the use of proper controls, sound analytical methods, and weathering of the oil.
Review of Monitoring Protocols for Dispersant Effectiveness. Merv Fingas, Environment Canada. August 2003. This report includes explanations of experimental design, technology, and proper methodology necessary to conduct an accurate dispersant field test. (pdf/358KB)
A White Paper on Oil Spill Dispersant Field Testing. Merv Fingas, Environment Canada. May 2002. Reviews field monitoring of the effectiveness of oil spill chemical dispersants and examines considerations related to monitoring dispersant use. (pdf/2.4MB)
Salinity
Salinity plays a role in dispersant effectiveness. There are geographic and seasonal areas in Prince William Sound where low salinities are prevalent. It is unlikely that the standard dispersants would work well in these areas.
Dispersants, Salinity and Prince William Sound. Merv Fingas, Environment Canada. December 2004. (pdf/5.5MB)
Photoenhanced Toxicity
Photoenhanced toxicity is the increase in the toxicity of a chemical in the presence of ultraviolet light compared to a standard laboratory test conducted with fluorescent lighting.
Since standard dispersants toxicity testing has traditionally been conducted in a laboratory setting with fluorescent lighting, the council wanted to know how natural lighting might affect the toxicity of chemically dispersed oil. Photoenhanced toxicity, it turns out, is a factor that needs to be considered when chemically dispersing oil into the waters of Prince William Sound and the Gulf of Alaska.
Assessment of the Phototoxicity of Weathered Alaska North Slope Crude Oil to Juvenile Pink Salmon Final Report. Mace Barron, Mark Carls, Jeff Short, Stanley Rice, Ron Heintz, Michelle Rau and Richard Di Giulio. December 2, 2003. (pdf/57KB)
Critical Evaluation of CROSERF Test Methods for Oil Dispersant Toxicity Testing under Subarctic Conditions. Dr. Mace Barron, January 29, 2003. (pdf/174KB)
Potential for Photoenhanced Toxicity of Spilled Oil in Prince William Sound and Gulf of Alaska Waters. Mace Barron. March 9, 2000. (pdf/427KB)
Photoenhanced Toxicity of Aqueous Phase and Chemically-Dispersed Weathered Alaska North Slope Crude Oil to Pacific Herring Eggs and Larvae Final Report. Mace Barron, Mark Carls, Jeffrey Short, Stanley Rice. February 11, 2002. (pdf/1.7MB)
Dispersant Use in Relation to Other Oil Spill Response Techniques
Weather Windows for Oil Spill Countermeasures
Weather is the single most important factor in choosing and obtaining success with oil spill countermeasures—mechanical recovery, chemical dispersants, and in-situ burning. To understand better the "windows of opportunity" associated with each countermeasure, the council contracted with Dr. Merv Fingas of Environment Canada to study weather limitations of the countermeasures. The two most important factors described by Dr. Fingas are wind and wave height. Other weather factors of importance include current speed and temperature.
Weather Windows for Oil Spill Countermeasures. Merv Fingas, Environmental Technology Centre, Environment Canada. January 2004. (pdf/8.6MB)
Oil Spill Response Techniques Efficiency Review
To better understand the various nearshore oil spill response technique efficiency rates, the council commissioned Nuka Research and Planning, LLC to review moderately sized spills in the United States between 1993 and 2000. The review included categorizing the responses by types, and estimating, based upon the available response information, efficiency rates for the various techniques used including dispersants and mechanical recovery.
Review of Oil Spill Responses on Moderately-Sized Spills in US Waters from 1993-2000. Elise DeCola, Nuka Research and Planning, LCC. March 2004. (pdf/318KB)
Dispersant Literature Reviews
To aid in its dispersants investigation, the council commissions literature reviews, which are focused on the question of efficacy in cold waters.
Salinity, Weathering, Resurfacing of Dispersants: Bibliography, 2006. (pdf/44KB)
Excel file available upon request from Joe Banta.
A Review of the Emulsification Tendencies and Long-term Petroleum Trends of Alaska North Slope (ANS) Oils and the "White Paper on Emulsification of ANS Crude Oil Spilled in Valdez." Merv Fingas, Environmental Technology Centre, Environment Canada. August 2005 (pdf/3.7MB)
A Review of Literature Related to Oil Spill Dispersants Especially Relevant to Alaska. Merv Fingas, Environmental Technology Centre, Environment Canada. March 2002. (pdf/283KB)
Links
Coastal Response Research Center Dispersants Working Group
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