United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/600/R-93/195
November T993 /
&EPA
Use of Chemical
Dispersants for
Marine Oil Spills
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EPA/600/R-93/195
November 1993
USE OF CHEMICAL DISPERSANTS FOR MARINE OIL SPILLS
by
IT Corporation
11499 Chester Road
Cincinnati, Ohio 45246
Contract No.
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DISCLAIMER
The information in this document has been funded by the U.S. Environmental
Protection Agency (EPA) under Contract No. 68-C2-0108 to IT Corporation. It has been
subjected to the Agency's peer and administrative review, and has been approved for
publication. Mention of trade names or commercial products does not constitute endors-
ement or recommendation for use.
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FOREWORD
Today's rapidly developing technologies, industrial products, and practices fre-
quently carry with them ^generation of materials that, if improperly dealt with, may
threaten both human health and the environment. The U.S. Environmental Protection
Agency (EPA) is charged by Congress with protecting the Nation's land, air, and water
resources. Under a mandate of national environmental laws, the Agency strives to for-
mulate and implement actions leading to a compatible balance between human activities
and the ability of natural resources to support and nurture life. These laws direct the
EPA to conduct research to define our environmental problems, measure the impacts,
and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, imple-
menting, and managing research, development, and demonstration programs. These
programs provide an authoritative, defensible engineering basis in support of the policies,
programs, and regulations of the EPA with respect to drinking water, wastewater, pesti-
cides, toxic substances, solid and hazardous wastes, and Superfund-related activities.
This publication presents information on current research efforts and provides a vital
communication link between the researcher and the user community.
An area of major concern to the Risk Reduction Engineering Laboratory is the
impacts associated with oil spills in both marine and freshwater systems. This document
is intended to bring together all pertinent information on the use of chemical dispersants
as a tool in controlling oil spills in marine waters. It is meant to be a neutral presenta-
tion, referencing existing literature to the extent practicable, on the advantages and dis-
advantages of using dispersants.
Further information relative to this document may be obtained by writing to
Daniel Sullivan, P.E., U.S. EPA (MS-106), Releases Control Branch, 2890 Woodbridge
Avenue, Edison, New Jersey 08837-3679.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
111
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ABSTRACT
Chemical dispersants are one of the tools available to oil spill response personnel
during a spill incident in marine waters. This document presents information from the
literature relative to dispersant effectiveness, toxicity, and other environmental factors,
regulatory and administrative considerations, application methods, the dispersant use
decision process, and practical considerations for dispersant use. It is meant to be a neu-
tral presentation on the benefits and disadvantages associated with dispersant use in
marine waters.
Numerous documents have been published on the fate and effects of chemically
dispersed oil, the effectiveness of chemical dispersants, application techniques for disper-
sants, and criteria for deciding whether to use dispersants. Most of these documents
have appeared in the proceedings of the biennial Oil Spill Conferences or have been
published by the American Society for Testing and Materials (ASTM), the American
Petroleum Institute (API), and various other U.S. and foreign sources^ Because these
documents were produced by a wide variety of sources over a period of years, this docu-
ment compiles relevant information from these sources into a concise format for the use
of planners, responders to oil spills, and the lay public. The document has been re-
viewed by a group of 20 technical advisors and reviewers who are listed in the Acknowl-
edgements. The document contains four appendices that provide information on vessel
and aircraft application equipment, conversion factors and calculation tables, example
decision trees, and a bibliography.
This report was submitted in fulfillment of Contract No. 68-C2-0108 by IT Corpo-
ration under the sponsorship of the U.S. Environmental Protection Agency. This report
covers a period from September 1992 to September 1993, and work was completed as of
September 1993.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures . vii
Tables . vii
Abbreviations and Acronyms .. . . viii
Acknowledgements . . .. ix
1. Introduction 1
*
1.1 Characteristics of Oil and Oil Spills 2
1.2 Response to Oil Spills 4
1.3 Oil Burning 5
1.4 Accelerated Biological Treatment 5
1.5 Sinking the Oil 6
1.6 Planning and Regional Contingency Plans 6
1.7 Stages of An Oil Spill Response 7
2. Oil Spill Response Chemicals .. „ 11
2.1 Chemical Dispersants •...-..- 13
2.2 Other Oil Response Chemicals 16
3. Dispersant Effectiveness 18
3.1 Types of Oil, Viscosity r 20
3.2 Weathering of Oil ....." 21
3.3 Nature of Oil Spill 22
3.4 Sea State and Characteristics 22
3.5 Type of Dispersant 24
3.6 Dispersant Application Method 24
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CONTENTS (continued)
Page
4. Environmental Factors 26
4.1 Concerns About Toxicity of Dispersants - • 28
4.2 Chemical Dispersant Use Around Coral Reefs and
in Shallow Waters 32
4.3 Dispersant Use in Breeding Areas 33
4.4 Dispersant Use in Bird Habitats •. . .. 33
4.5 Intertidal Habitats 34 -
4.6 Dispersant Use in Other Habitats .. 34
5. Regulatory and Administrative Aspects 36
5.1 National Contingency Plan .36
5.2 Oil Pollution Act ... '39
6. Application of Dispersants . *. 42
6.1 General Principles of Dispersant Application 42
6.2 Marine Vessel Application 45
6.3 Aerial Application .49
7. Decision Process for Dispersant Use 58
7.1 Simplified Decision Tree ........ 59
7.2 Monitoring Dispersant Effectiveness 64
8. Practical Considerations for Dispersant Use 69
Appendices
A Description of Vessel and Aircraft Application Equipment 72
B Conversion Factors and Calculation Tables 80
C Example Decision Trees 92
D Bibliography < 99
VI
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FIGURES
Number Page
\
1-1 Major Tanker Spills 1970-92 . . 3
• . . •
2-1 Mechanism of Chemical Dispersion 15
6-1 Dispersant Delivery System Using a Boom-Mounted Arrangement .... 47
6-2 Spray Arm System With Overlapping Spray Pattern 47
6-3 Photograph of a Helicopter With Suspended Bucket Applying . 51
Chemical Dispersant
6-4 Photograph of a Bell 212 Helicopter With Simplex Bucket 51
6-5 Photograph of a Fixed Wing F-27 Applying Chemical Dispersant ...... 52
6-6 Photograph of a C-130 With ADDS Pack ......... 52
7-1 Oil Spill Initial Response Decision Tree 60
7-2 Oil Appearance as a Function of Thickness . . 65
TABLES
Number Page
7-1 Remote Monitoring of Oil Slicks 66
vn
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ABBREVIATIONS AND ACRONYMS
ACP Area Contingency Plan
ADDS Airborne Dispersant Delivery System
API American Petroleum Institute
ASTM American Society for Testing and Materials
CFR Code of Federal Regulations
COTP Captain of the Port
CWA Clean Water Act
EPA Environmental Protection Agency
ERT Environmental Response Team
FOSC Federal On Scene Coordinator
HV High Volume
IMQ International Maritime Organization
ITOPF International Tanker Owners Pollution Federation
LV Low Volume
MASS Modular Aerial Spray System
MMS Minerals Management Service
NCP National Contingency Plan
NCPPS National Contingency Plan Product Schedule
NIST National Institute of Standards and Technology
NOAA National Oceanic and Atmospheric Administration
NRC National Research Council
OPA Oil Pollution Act of 1990
OSC On Scene Coordinator
RCP Regional Contingency Plan
RREL Risk Reduction Engineering Laboratory
RRT Regional Response Team
SLAR Side Looking Airborne Radar
SSC Scientific Support Coordinator
STP Special Technical Publication
ULV Ultra Low Volume
UNEP United Nations Environmental Program
USAF United States Air Force
VMD Volume Mean Diameter
vm
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ACKNOWLEDGMENTS
This document was prepared by IT Corporation under contract to the Risk
Reduction Engineering Laboratory of the U.S. Environmental Protection Agency. A
group of technical advisors and reviewers was established at the beginning of the effort
to comment on the document as it was being written; however, their participation does
not imply concurrence with all conclusions in this document. That group is
acknowledged below. Further, comments on the completed draft document were
solicited from members of the National Response Team. Parts of the document were
extracted from draft dispersant use documents being produced by the Region II Regional
Response Team.
Technical Advisors
1. Mr. Merv Fingas, Chief
Emergencies Science Division
Tech. Development Branch
Environment Canada
Rm. 204, 3439 River Road
Ottawa, Ontario CANADA
K1A OH3
Phone: 613-998-9622
FAX: 613-991-9485
Reviewers
1. Ms. Gail Thomas
Environmental Protection
Specialist
Oil Pollution Response &
Abatement Sec.
U.S. Environmental Protection
, Agency
401 M Street, SW, ERD 5202-G
Washington, DC USA 20460
Phone: 703-603-8736
FAX: 703-603-9116
2. Dr. James N. Butler
Professor
Division of Applied Sciences
Harvard University
Pierce Hall, 29 Oxford Street
Cambridge, MA USA 02138
Phone: 617-495-2845
FAX: 508-358-5732
2. Mr. Kurt Jakobsen
Program Manager, Oil Spills
Research, Office of Research &
Development
U.S. Environmental Protection Agency
401 M Street, SW
Washington, D.C. USA 20460
Phone: 202-260-0594
FAX: 202-260-4524
IX
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3. Dr. Royal Nadeau
Deputy Branch Chief
Environmental Response Team
U.S. Environmental Protection
Agency (MS-101)
2890 Woodbridge Ave.
Raritan Depot Bldg. 18
Edison, NJ USA 08837
Phone: 908-321-6743
FAX: 908-321-6724
4. Mr. Doug Kodama, Chair
and Mr. Mike Solecki
OPA Regional Workgroup
U.S. Environmental Protection
Agency (MS-211)
2890 Woodbridge Ave.
Raritan Depot Bldg. 18
Edison, NJ 08837
Phone: 908-906-6905
FAX: 908-321-4425
5. Ms. Linda Ziegler
Oil Program Coordinator
Oil and Title III Section (3HW34)
U.S. Environmental Protection
Agency
Superfund Removal Branch
841 Chestnut Bldg.
Philadelphia, PA USA 19107
Phone: 215-597-1395
FAX: 215-597-8138
6. Dr. Robert R. Hiltabrand
Senior Environmental Scientist
Environmental Safety
U.S. Coast Guard R&D Center
1082 Shennecossett Road
Groton, CT USA 06340-6096
Phone: 203-441-2792
FAX: 203-441-2792
7. Capt. Richard Larrabee
U.S. Coast Guard
Captain of the Port
Building 108
Governors Island, NY 10004
Phone: 212-668-7917
FAX: 212-668-7907
8. Mr. Ed Levine
NOAA/SSC
Building 110, Box 2
Governors Island, NY 10004
Phone: 212-668-6428
FAX: 212-668-6370
9. Mr. Gary Shigenaka
c/o NOAA/HAZMAT
7600 Sand Point Way, NE
Seattle, WA 98115
Phone: 206-526-6402
FAX: 206-526-6941
10. Mr, Tom Quinn, Director
Spill Prevention & Response Division
NYS Environmental Conservation
50 Wolf Road, Room 340
Albany, New York 12233-3510
Phone: 518-457-7469
FAX: 518-457-4332
11. Mr. Stan Delikat, Chief
Bureau of Emergency Response
New Jersey Department of
Environmental Protection & Energy
401 E. State St., CN028
Trenton, NJ 08625-0028
Phone: 609-292-1075
FAX: 609-777-0985
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12. Ms. Alexis Steen
Senior Environmental Scientist
Health and Environmental Sciences Dept.
American Petroleum Institute
1220 L Street, Northwest
Washington, D. C. 20005
Phone: 202-682-8339
FAX: 202-682-8270
13. Dr. Bela James
Shell Oil Company
P.O. Box 4320
Houston, TX 77210
Phone: 713-241-5134
FAX: 713-241-3325
14. Mr. David Fritz
Amoco Oil Company (MS H-9)
P.O. Box 3011
Naperville, IL 60566-7011
Phone: 708-420-4985
FAX: 708-420-5016
15. Mr. Charles Christopher
Amoco Production Company
P.O. Box 3385
Tulsa, OK 74102
Phone: 918-660-3325
FAX: 918-660-4175
16. Mr. Don Henne
U.S. Department of Interior
Office of Environmental Affairs
U.S. Customs House, Room 217
200 Chestnut Street
Philadelphia, PA 19106
17. Dr. Robert J. Fiocco
Senior Engineering Associate
EXXON Research & Engr. Co.
P.O. Box 101
180 Park Avenue
Florham Park, NJ 07932
Phone: 201-765-6844
FAX: 201-765-1496
XI
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SECTION 1
INTRODUCTION
The literature contains a great deal of technical information regarding responses
to oil spills as well as the fate and effects of oil in the marine environment. This docu-
ment provides an overview of the general concepts and conclusions of previous research
and observations pertaining to one type of oil spill countermeasure-oil dispersing chem-
icals. The material presented in this document is intended for use by regional response
teams (RRTs), areawide committee members, other planners and responders to oil spills,
state and local officials, and the general public. This document is intended to provide a
basic understanding of oil dispersant use as a spill response measure and the trade-offs
that may be involved in the decision to use dispersants or to follow other response
actions. Technical details on the application of dispersants are included to assist
response personnel in preparing for and carrying out a spill response involving the use of
dispersants.
Although oil spills can occur in several environments, including on land and in
rivers, lakes, and shores, this document focuses solely on use of chemical dispersants for
oil spills occurring in the marine environment. Details of the concepts presented here
cannot be extended to the freshwater environment because not only do dispersants per-
form differently in freshwater, but the fate of dispersed oil in a river or lake may be very
different from that in the marine environment.
Dispersants do not provide a direct cleanup method for oil spills because they do
not remove the oil from the environment. Instead, dispersants promote the distribution
of oil throughout the water column and, as such, represent an oil spill control method.
Dispersants can also be used in conjunction with other oil spill control methods when
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properly coordinated. The appropriate use of dispersants may provide an increased
measure of control in affecting the fate of spilled oil. In any event, the decision to use
dispersants must be weighed against the relative risks of allowing the oil to reach
possibly sensitive shoreline areas vs. mixing and diluting it into the water column.
In practice, only rarely is any countermeasure completely effective in removing
floating oil. Just as mechanical recovery operations rarely collect more than 10 to 15
percent of the oil in open-sea conditions, dispersants usually remove as much as 30 per-
cent of a large spill from the surface under good conditions (Moller, et al., 1987; Nichols,
1993). Because environmental and economic impacts will occur regardless of the type of
response, the best spill response is one that minimizes the overall impacts.
1.1 Characteristics of Oil and Oil Spills
Oil is composed of thousands of hydrocarbon compounds whose relative propor-
tions vary, depending on its reservoir of origin, date of production, and subsequent
processing, transportation, and storage history. Oil consists mostly of low molecular
weight compounds (aliphatics and aromatics) that allow it to remain in a liquid state at
ambient conditions. These compounds act as solvents for the higher molecular weight
compounds (asphaltenes, resins, waxes).
Although a considerable amount of oil enters the environment from natural seeps,
significant amounts are also accidentally spilled or discharged. The vast majority of spills
are small, under 1000 gallons. In 1990, for example, the following oil spills occurred:
12,892 oil spills of less than 1,000 gallons (24 barrels)
980 oil spills of between 1,000 and 10,000 gallons (24-238 barrels)
208 oil spills of greater than 10,000 gallons (over 238 barrels)
Although the largest spills (usually from supertankers) are most often associated with
coastal marine waters, many large spills have occurred on inland freshwater systems.
Figure 1-1 shows the number of large marine spills for the past 22 years.
The detrimental effects of oil spills are most dramatic when oil is seen smothering
small animals or inducing hypothermia (by nullifying thermal insulation) in ocean mam-
mals and wild fowl. Components of oil can also be toxic to specific organisms by causing
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1970-79:24.5 spills/year
1980-92:9.1 spills/year
*^—A
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92
Year
Figure 1 -1. Major tanker spills*, 1970-1992.
(ITOPF, ,993)
*greater than 215,000 gal (700 metric tons or 5,130 bbl)
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fatal injury or alteration of behavior so as to greatly shorten lifespan. Spilled oil can also
render ecological niches incapable of life support for a season or for a longer period.
Under proper conditions, however, oil can provide a food source for some micro-
organisms, thereby affecting the degradation and fate of oil in the ecosystem.
12 Response to Oil Spills
In 1968, the Federal Government began oil pollution response efforts in the areas
of prevention and cleanup. In addition, current laws and regulations require a number
*
of safeguards. For example, regulations were developed to provide added protection
when oil is transferred between ships and shore terminals, and spill prevention regula-
tions were designed for onshore and offshore facilities. Accidents still occur despite
these precautions, however, primarily because of human error or equipment failure.
In cases where oil spill prevention has been ineffective, the preferred response has
been to contain the floating spill and to physically remove as much of the oil as possible
from the marine environment. An oil slick is typically contained with booms to prevent
further spreading and to reduce the movement and contamination of sensitive environ-
ments. The oil is subsequently skimmed and either recycled or disposed of at a land-
based disposal site. Unfortunately, collection efforts only account for approximately 10
to 15 percent of the oil spilled in the open sea. Inclement weather and logistical
problems (such as the lack of timely access to sufficient boom/skimming equipment)
often account for these low removal rates. Mechanical skimming generally can be at-
tempted if winds are under 20 miles per hour (30 kilometers per hour), but it is more
effective at lower wind speeds. When winds are greater than 30 mph (50 krn/h), skim-
ming is not effective.
If physical oil removal is ineffective or unable to be implemented, the next choice
has been to try to keep the spilled oil from contaminating the most biologically or cul-
turally significant resource areas, such as the shallow benthic zone and the shoreline.
This approach usually entails the use of booms or other barriers between the oil slick
and the resource. Other possible alternatives include the following:
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• Using dispersants to transfer oil from the surface into the upper water column.
• Burning oil in place.
« Accelerating biological treatment of the oil in place.
• Using sinking agents to move oil to the ocean bottom.
« Doing nothing.
Of these, the only direct prohibition by EPA has been on the use of sinking agents.
1.3 Oil Burning
Oil burning has been used with limited success in test spills to remove a substan-
tial portion (90%) of spilled oil. Although it has only been used once in the United
States (Exxon Valdez), burning has been used successfully in certain limited applications
in Canada and Norway. Burning is restricted to an oil slick that has specific properties,
and the physical and environmental conditions must be within fairly narrow limits for
burning to be successful. Such conditions are not present in most spill situations; when
all conditions are favorable, however, burning has the greatest potential for rapidly re-
moving the bulk of the oil from the water and leaving only a viscous tarry residue.
The trade-off in the use of burning is the generation of smoke plumes (par-
ticulates) and potential air pollutants. Also, the heat and flames generated can be quite
substantial, up to 300 feet (90 meters) into the atmosphere. This may be an acceptable
trade-off, however, for a short period of time in the open sea. Certainly, the issue war-
rants further attention. Federal research on oil burning is being conducted primarily by
the National Institute of Standards and Technology (NIST) and the Minerals Manage-
ment Service (MMS) of the Department of the Interior.
1.4 Accelerated Biological Treatment
Biological treatment has often been suggested as a tool in responding to oil spills.
This treatment, however, has two major drawbacks: (1) its natural processes are slow
when compared with required response times for open water oil spill cleanup; and
(2) the elements needed for biological degradation (i.e., sufficient nutrients) are difficult
to maintain in correct proportions on open water spills. The addition of nutrients may
also pose a lexicological hazard to marine organisms. Further, a typical slick moving
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toward a shoreline or other sensitive area is likely to impact it before effective biodegra-
dation can occur.
Over a period of weeks or months, however, biological processes can have sub-
stantial beneficial effects. In addition, organisms that can degrade various hydrocarbons
abound. Given proper environmental conditions, sufficient nutrients, and time, these
natural processes are probably the paramount activity for cleansing ecologically sensitive
areas of oil pollution. Further, bioremediation systems can be used to treat recovered
oil and oil-contaminated debris.
1.5 Sinking the Oil
Sinking the oil has been prohibited in this country because the impacts on produc-
tive benthic aquatic ecosystems would be greater than leaving the oil on the surface.
Further, much more time is usually required for biological degradation because less
oxygen is available in the bottom sediments.
Considerable laboratory and field data have been generated concerning the effects
of petroleum hydrocarbons on marine benthic communities. Long-term exposure to con-
centrations in the 1- to 100-ppm range results in acute toxicity for some benthic species.
Such long-term exposures are not typical of dispersant use. If, however, the oil is
trapped in sediment and is slowly released over time, chronic toxicity problems can arise
for benthic species. The exposure of benthic species under these conditions is similar to
laboratory toxicity test exposures in which chronic toxicity tests have demonstrated
numerous lethal, developmental, and behavioral effects. Thus, the risk of adverse eco-
logical effects is extremely high if oil is incorporated into bottom sediments following the
sinking of an oil slick.
1.6 Planning and Regional Contingency Plans
Advance planning and preparation are essential for any successful response. The
procedures to be followed must be decided upon in advance instead of during the crisis
situations that occur during a spill. The planning document developed by the RRT is a
regional contingency plan (RCP) that outlines a spill response policy. Many regions of
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the country will address marine dispersant use in updated RCPs and in Area Contin-
gency Plans (ACPs) developed for each Captain of the Port (COTP) zone. Each plan
committee is requested to formulate expedited decision-making procedures governing the
use of dispersants and other chemical countermeasures in their area.
This document presents a foundation for the dispersant planning process. Plan-
ning for all contingencies, however, is not possible. • An oil spill is usually accidental, and
response to the spill depends on numerous unpredictable variables. Certain planning
actions can be put in place that will improve the response and thus lessen adverse
impacts. Proper planning should address not only the decision process (Section 7) and
the type of dispersant and equipment to use (Section 6), but also the availability of the
dispersant and equipment. Unforeseen events may still occur, however, that have
unplanned consequences. Oil spill response planners, who have a basic understanding of
available response options, can address these unplanned events.
Immediate decisive action in the event of an oil spill can appreciably reduce the
impact of the spill. In addition, a spill response must be flexible enough to address the
changing events by applying alternative technologies and/or conventional methodologies
in concert, as appropriate. Two responses that have had extensive application in the
United States are off-shore recovery and shoreline cleanup. This document focuses on
the use of oil spill dispersants. The material in this document provides much of the
information needed for a planner to evaluate conditions and implement dispersant use
when circumstances are favorable.
1.7 Stages of An Oil Spill Response
The response to a typical oil spill involves three stages. The first stage is charac-
terized by confusion resulting from a lack of information, the second stage by initial
countermeasure implementation, and the final stage by stabilized response. Oil spill
dispersants are most likely to be useful during the first two stages.
The first stage of a spill, when the lack of accurate information generates con-
fusion concerning an appropriate response, is the time to begin to mobilize dispersant
equipment and make preparations to start dispersant application if further reconnais-
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sance indicates conditions are appropriate. Preparation for dispersant application during
this stage is one of the critical factors in an effective oil spill response. Dispersants are
more effective on fresh crude oil compared with weathered crude oil that is several days
old. Thus, even if it is unknown whether the use of dispersants will be the response
method of choice, it is prudent to begin mobilization of the dispersant, application equip-
ment, and supplies until sufficient information is obtained to make the decision. This
course of action should be followed unless dispersant use in the area has been precluded
during preplanning.
The second stage of a spill response involves the actual countermeasure activity.
At this stage, there should be sufficient information and resources to initiate the re-
sponse actions best able to address the current situation. This second stage involves
experimentation and evaluation. Although a response may have already been initiated,
the effectiveness of the response will only be known after observation and feedback from
the field. In addition, adjustments will be required as part of the recovery or dispersant
operation. Changes may be required because of equipment availability, weather con-
ditions, storage capacity, or changes in the character of the oil. In this stage, the
response is organized in the field and the best techniques for the particular conditions
developed.
The third stage of a response is characterized by a more stable approach involving
routine activities. For a large spill, the third stage may not begin for days. By this time
in the life of an oil spill response, the organization should be in place, equipment on site,
and personnel responding to the situation. In this stage, the dispersant's effectiveness is
declining, and more emphasis is placed on recovery or shoreline cleanup. Unless the
spill is from an ongoing source, the oil may be too weathered for dispersants to be effec-
tive.
Throughout all three stages, the overall objective of an oil spill response is to
reduce the environmental and economic impact (both short- and long-term) of the spill.
The evaluation of the potential environmental and economic impacts is a complex under-
taking that must be accomplished under less-than-ideal conditions. The interrelationship
between environmental and economic impacts involves both technical uncertainties and
8
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policy concerns. Opposing external pressures are often placed on an oil spill responder
concerning the potential impacts and how best to avoid them.
There are four major options that may be combined when responding to a spill.
These options are the no-action (natural degradation) approach, shoreline cleanup,
mechanical containment and recovery, and the use of chemical dispersants (NRC, 1989).
A fifth option, in-situ burning, also shows promise. Countermeasures that are less widely
used or have major limitations include gelling and enhanced biodegradation.
In some cases, the no-action alternative is the only choice because of stormy wea-
ther, lack of equipment, lack of qualified response personnel, or the lack of a bona fide
contingency plan. The no-action approach sometimes may be used in cases where the
spill can disperse naturally, where the shoreline impact is expected to be small, or where
shoreline removal is appropriate. This approach is ideal in many ways when the spill
location away from sensitive areas allows such ah approach and the oil is of the type that
will disperse naturally. Also, safety risks to response personnel are minimized, and the
environmental impacts to the open sea are thought to be minor relative to the environ-
mental impact at the coast. If this option is selected, there should be some certainty that
the spill will naturally disperse before it reaches the shoreline.
The second option is to allow the spill to come ashore and then to conduct clean-
up operations along the coast. This course of action is often involuntary when spill coun-
termeasures off shore are unsuccessful and coastal areas become oiled. Such a cleaning
operation can often cause significant environmental impacts and economic loss.
Recovery off shore has the greatest potential for minimizing environmental harm.
Such recovery operations, however, have historically been only marginally effective
(approximately 10 to 15 percent recovery) on major spills. Weather, equipment, storage
capacity, and area coverage have combined to prevent recovery operations from sig-
nificantly limiting shoreline impacts.
The fourth approach available is the use of chemicals, including dispersants, while
the oil is still on the water. This approach does not preclude the use of other responses.
Dispersant chemicals are the primary response mechanism in some European countries,
even though they are infrequently used in the United States. Dispersants, however, do
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not represent a panacea for oil spills. The effectiveness of dispersant countermeasures
can be increased with greater understanding of their proper use and limitations, and with
better preparation and planning.
Before any of these spill response approaches is implemented, certain information
is necessary to ensure the optimum combination of countermeasures. Minimum
information needed to determine a suitable countermeasure option includes:
Spill location (including geographic location and habitat type)
Oil type
Quantity released
Weather and sea conditions
Probable spill path
Potential consequences of coastal impact.
As mentioned, all of the information will not be available in the initial portion of the
response. The above information nevertheless can be used to identify the optimal
response mechanism. Actual implementation of the response, however, depends on
other factors such as resource availability and approval for dispersant use. In some
instances, best response methods may be identified but a lack of planning may still result
in the equipment, personnel, or approvals being unavailable within the time frame
needed to provide an optimal response. Therefore, proper preplanning prior to an oil
spill is essential to maximize the number of options available during a spill.
10
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Surface slicks are not easily biodegraded because they have a relatively smaller
water oil interface area compared with an oil-in-water dispersion. Oil on the surface is
also subject to emulsification, which increases the slick volume by forming degradation-
resistant emulsions that can contain up to 80 percent water. These emulsions are dif-
ficult to treat by either mechanical or chemical means,
"Weathering" of the slick begins to occur almost immediately. In this natural
process, the low molecular weight hydrocarbons evaporate and dissolve, leaving behind
the larger petroleum rosin and wax molecules. The bulk of evaporation occurs within
the first 24 hours, and, although the process continues, the residue remaining after this
period becomes more viscous and difficult to skim. This residue becomes increasingly
more difficult to handle with time.
In the rough seas, emulsification usually occurs. In this process, water mixes with
the oil to form an oil-water "mousse." This mousse (water-in-oil emulsion) is viscous and
has a volume up to five times greater than the oil alone. These characteristics make the
mousse difficult to remove or to otherwise be effectively handled for all cleanup methods
including skimming, burning, and dispersant application.
A mass balance performed on a typical spilled oil would yield the following results
within the first few days:
• A substantial quantity (up to 30 to 40 percent) would be removed through
evaporation.
• Some oil would be transferred in.o the water column, depending on sea condi-
tions.
• Very little would be biologically removed.
• Very little would be removed by photooxidation.
• Very little would sink.
If oil remains in the open sea, as much as 30 to 40 percent could evaporate, 50 percent
could be biologically metabolized, and approximately 10 to 20 percent of the heaviest
compounds would form tar balls or sink to mid-depths or the bottom of the sea. In most
cases as long as the slick does not move shoreward, its impact would be minimized by
the minimal exposure to humans or sensitive ecological areas. Unfortunately, not all
slicks stay at sea; they often reach land where the impact can be dramatic. Of course,
12
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SECTION 2
OIL SPILL RESPONSE CHEMICALS
Oil spill response chemicals are one of the countermeasures available to control
the spread of oil. Only chemicals that are listed with the U.S. Environmental Protection
Agency (EPA) may be used in U.S. waters. These chemicals are on the Product
Schedule of the National Contingency Plan (NCP - 40 CFR 300). Approximately 100
chemicals were listed in 1993 in the following four categories:
• dispersants - 48 products
• surface collecting agents - 2 products
• biological additives - 42 products
• miscellaneous oil spill control agents - 10 products
Definitions of these categories may be found in the NCP; they are discussed further at
the end of this section.
When large quantities of oil are released onto or into a body of water over a
short time, a slick forms and begins to spread rapidly in an uneven film. The extent of
the spread in the marine environment depends on sea conditions, especially wind, wave,
and current conditions. The degree of oil thinning depends on the types of oil, size of
spill, and other physical factors. In the absence of wind and waves, the film thickness
depends on the surface tension and oil viscosity. Wind and wave action can cause thick
patches of oil to form. The thickness of freshly-spilled oil can rapidly approach an aver-
age of 0.1 millimeter (mm) or less within a matter of a few hours except in areas where
wind and wave action form thicker patches that can exceed 1.0 mm (NRC, 1989). Slick
thickness also increases to over 0.1 mm in areas where a natural barrier is encountered
(e.g., a shoreline).
11
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there may be instances where an oil slick at sea can also have significant impacts on
sensitive ecological areas.
2.1 Chemical Dispersants
Dispersants are defined as "those chemicals that emulsify, disperse, or solubilize
oil into the water column or promote the surface spreading of oil slicks that facilitate
dispersal of the oil into the water column" (U.S. EPA, 1990). The purpose of chemical
dispersants is to enhance the natural dispersion process by facilitating the formation of
small (less than 20 Mm) oil droplets. Oil droplets on the order of 20 urn rarely coalesce
and are carried away both vertically and horizontally from the oil slick by wave action.
Dispersion also removes the oil from the action of the wind that may bring a slick
ashore. The dispersed oil becomes rapidly diluted in the sea water. Studies have shown
that the transient concentration of oil under a dispersed slick can range from as high as
50 ppm to as little as 1 ppm (Cormack and Nichols, 1977). The dispersion induced by
chemicals occurs, rapidly, with the oil concentration ranging from 16 to 48 ppm within the
first 2 minutes, 5 to 18 ppm after 5 to 10 minutes, and 1 to 2 ppm after 1 hour and 40
minutes (Cormack and Nichols, 1977). More detailed testing relating oil concentrations
to water-column depth over time was performed by McAuliffe, et al., and was summar-
ized by NRC (McAuliffe et al., 1980; McAuliffe, et al., 1981; NRC, 1989). The key find-
ing of all of the studies is that although transient concentration in the water column goes
up significantly, the effect is on the order of a few hours.
In the dispersion process, two dissimilar substances coexist to form a mixture that
resists separation into its components under ordinarily encountered conditions. In a
dispersion, unlike a solution, the two substances retain many of the physical properties of
the separate substances.
Chemical dispersants are surfactant formulations that generally include a solvent
carrier to reduce viscosity. The active ingredients are often a blend of surfactant esters
with both water-compatible (hydrophilic) and oil-compatible (lipophilic) properties.
Sulfosuccinate, sorbitan monooleate, and polyethylene glycol esters are the more com-
13
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mon surfactant bases. The dispersant formulation is usually a blend of nonionk and
anionic surfactants. Nonionic surfactants generally constitute the bulk of the active in-
gredient in most dispersants (NRC, 1989).
Water-miscible hydroxy compounds and hydrocarbons are used as the solvent
carriers. All solvents are selected so as to minimize the toxicity within the solvent group.
Hydrocarbon solvents are specifically selected on the basis of their low aromaticity.
With a minimum amount of mixing, the surfactant in the chemical dispersant can
diminish the tension at the oil-water interface and promote the breakup of the slick into
small oil droplets. Figure 2-1 illustrates the mechanism of chemical dispersion. When
optimally applied, the surfactant travels to the oil/water interface. The surface tension is
lowered as a result of the natural orientation of the dispersant molecules (i.e., lypophilic
toward the oil and hydrophilic toward the water). The amount of energy required to
disperse the oil depends on the quantity of dispersant applied, the composition of the oil
and water, and the extent to which the dispersant surfactants lower the interfacial
tension. Even a low amount of energy from wave action and currents can be sufficient
to distribute the dispersant and encourage droplet formation; breaking waves or mechan-
ical mixing is not required.
Chemical dispersants can break up an oil slick into small oil droplets. Through
the mixing energy provided by the sea, the droplets will rapidly disperse into the upper
one to ten meters of the water column. Chemically dispersed oil resembles a colloidal
suspension such as milk with finely divided droplets distributed throughout the water col-
umn. These droplets increase the surface area of the oil and may aid in natural degra-
dation; however, surfactant molecules at the interface of these droplets may compete for
surface sites with microorganisms that could degrade the oil (NRC, 1989).
Dispersants can be used in the initial response to an oil spill and, unlike mechan-
ical methods, can rapidly respond over a large area when applied by aircraft. Applica-
tion of chemical dispersants to an oil slick can reduce the amount of oil reaching the
shoreline. Dispersion of oil at sea generally will reduce the overall impact and
particularly the chronic impact of oil on many habitats (NRC, 1989). Oil, if successfully
dispersed chemically offshore, has a much less persistent impact than does oil allowed to
14
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come ashore without dispersal. Such dispersion is particularly important in the case of
mangrove communities that can survive dispersed oil impact but not the impact of crude
oil slicks, which kill the mangrove trees and destroy the habitat (Baker, 1993).
A. Surfactant Locates at Oil/Water Interface
Application
Hydrophilic
n Group
Lipophilic
Group
B.
Oil Slick Readily Disperses Into Droplets
with Minimal Energy
Hydrophilic ^_
Portion of
Dispersant
Prevents
Droplet
Coalescence
Oil Droplets
Figure 2-1. Mechanism of chemical dispersion (Canevari, 1969).
In the late 1960s, degreasing solvents containing aromatic hydrocarbons such as
toluene and benzene were used as the first chemical dispersants (Gilfillan, 1992). The
experience with the Torrey Canyon (a tanker responsible for a major oil spill on the
English coast line of Cornwall in 1967) put an end to such solvent use because of its tox-
icity. Today, most surfactant formulations are much less toxic both with respect to the
active agents and the solvent carrier. These new formulations have a nonaromatic sol-
vent carrier and a blend of surfactants designed to reduce surface tension.
Chemical dispersants do not dissolve oil; dissolution is a completely different
process that uniformly blends two or more substances into a third new substance that has
unique chemical and physical properties. In a dispersion, the dispersed substance retains
15
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the identity and chemical properties of its components. The surface area of the oil is in-
creased, however, because droplets are formed and distributed throughout the water
column. The dispersion results in a transient localized increase of oil in the water
column. Low-molecular-weight hydrocarbons in the oil can more easily dissolve in the
water and are less susceptible to evaporation, which could cause increased localized
toxicity.
Large droplets can return to the water surface because oil drops are generally less
dense than sea water; therefore, dispersed oil droplets should have a small volume mean
diameter (VMD) of 1 to 20 ^m in order to avoid resurfacing (NRC, 1989). VMD is
defined as the droplet size in or above which is contained half the volume of a given
dispersion (Fingas, et al, 1991a). Measurements at sea during test spills have shown that
dispersants produce oil droplets with average diameters in the range of 15 to 25 ^m and
VMDs between 35 and 50 jum (Lunel, 1993). Oil droplets 20 /xm and smaller tend to
remain suspended in the water column because of turbulent diffusion. These oil droplets
will remain dispersed in the water column as a result of natural water currents or Brown-
ian motion (Clayton et al., 1992).
2.2 Other Oil Response Chemicals
The following are examples of other types of spill-treating agents:
Surface-Washing Agents
Surface-washing agents or surface-active washing agents are used to clean up con-
taminated surfaces. These agents hold oil removed from a solid surface such as
rocks, seawalls, and beaches in a stable emulsion.
Surface-Collecting Agents
Surface-collecting agents (herding agents) act like a "chemical boom" to keep the
spill from spreading. Herding agents are most effective for small, thin oil slicks in
calm, enclosed waters and have a limited "action" time.
16
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Biological Additives
These microbiological cultures, enzymes, or nutrient additives are deliberately
introduced into an oil spill for the specific purpose of encouraging biodegradation
in order to mitigate the effects of the spill.
Miscellaneous Oil Spill Control Agents
These are any products, other than a dispersant, sinking agent, surface-collecting
agent, or biological additive, that can be used to enhance oil spill cleanup, re-
moval, treatment, or mitigation. The following are examples of such products:
. Recovery agents such as elastomeric agents to condition the spilled oil
and improve the recovery efficiency of skimmers These include vis-
coelastic enhancing agents that reduce the spreading rate and also
make it easier for skimmers to recover very light fuel oils. These
chemicals are only applicable in restricted circumstances because of the
necessity to recover the viscous fluid after application.
• Demulsifiers to break formations of water-in-oil emulsions Demulsifier for-
mulations are usually surfactants or other polymeric materials that tend to
break oil-in-water emulsions. Some recent products do not contain surfac-
tants, but instead contain other polymeric materials that serve a similar func-
tion. Oil spills in rough seas often become emulsions, particularly if the oil
contains paraffins and/or asphaltenes that act as stabilizing agents.
. Solidification or gelling agents used for oil collection and slick control These
gelling agents consist of polymerization catalysts and cross-linking agents that
change the oil into a solid. Solidification of oil requires both mechanical
mixing and time for setting. Large amounts of gelling agents are usually re-
quired.
Oil spill response chemicals other than dispersants are not .covered in this document.
17
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SECTION 3
DISPERSANT EFFECTIVENESS
There remains controversy over the best means to quantitatively measure disper-
sant effectiveness. Measuring the decrease in interfacial tension between water and oil
upon the addition of dispersant provides the most reproducible and theoretically based
test, but it is difficult to translate the laboratory measurement into actual field effective-
ness. Although many dispersants are shown in the laboratory to reduce interfacial ten-
sion to near zero (NRC 1989), closely monitored test spills have shown that only two-
thirds of a slick may be transferred to the water column (McAuliffe et al., 1987). In
addition to problems of reproducibility, test methods other than interfacial tension
measurement suffer similar problems in relating the laboratory data to use in the field.
Realistically, only about 30 percent removal can be expected in most open sea cases
(Moller, et al., 1987; Nichols, 1993). Currently, the effectiveness of a dispersant in a
particular response situation can only be determined by visual observation. One option
being considered by RRTs is to allow only small applications of dispersants (on the order
of one drum over an acre) for a test of their effectiveness prior to full-scale use. Even
direct observations, however, often result in conflicting opinions on the effectiveness of
oil removal or the reduction in adverse impacts. The final test of effectiveness is the
degree of success achieved in either removing oil from the sea surface in a particular
situation or reducing environmental and economic impacts.
Each of these factors are discussed in this section of the document. Laboratory
tests are routinely used to evaluate the relative effectiveness of chemical dispersants. At
least six laboratory tests (over 35 have been developed) are currently used throughout
the world. Five simplified field tests are also available. Each laboratory test follows the
18
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general approach of establishing an oil slick on water, applying a dispersant to the slick
(either directly or by premixing the oil and dispersant), applying energy to mix the oil-
dispersant-water system, and measuring the amount of oil dispersed into the water
column. Because chemical dispersion of oil in water involves complex interactions of
«.
many variables, it is unlikely that any single laboratory test will ever be completely suit-
able for quantifying the performance of chemical dispersing agents for all possible en-
vironmental scenarios (Clayton et al., 1992). Nonetheless, the tests have been a useful
tool for government agencies to use to screen and compare dispersant products prior to
granting approval for field use.
Several investigators have compared laboratory tests and concluded that results of
the different tests do not correlate well; generally, the more different the types of oil
tested, the less the results correlate (Fingas and Tennyson, 1992). Further, although
laboratory tests are useful for screening purposes, the laboratory results may not cor-
relate well with actual field performance because many.variables affect dispersant per-
formance (e.g., adequacy of mixing, mixing energy, and oil-to-dispersant ratio). The field
effectiveness tests are rapid and simple, but their results are of a very qualitative nature^
rather than quantitative.
Before the decision is made to respond with dispersants to a particular spill, lab-
oratory data describing the effectiveness of dispersants for use with various oil types
should be evaluated in combination with dispersant properties such as low toxicity and
biodegradability. As a practical matter, however, it is unlikely that a wide selection of
dispersants will be available from which to conveniently choose. Therefore, unless there
is a direct centra-indication of dispersant effectiveness with the specific oil involved in a
spill, laboratory data must be considered only second to observation.
Quantitative field measurement systems that can be used to determine the effec-
tiveness of dispersants on site are not yet widely available and tested. Such systems are
needed to supplement visual observations. The fluorescent properties of certain com-
ponents of crude or refined oil can be used to quantitatively determine the amount of oil
dispersed or dissolved in water. Under field conditions, fluorometry is useful for deter-
mining the increased transfer of oil to the water column upon the application of disper-
19
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sants. The use of fluorometry in a spill response presents two major difficulties: (1) A
vessel equipped with the appropriate instrumentation is needed at the oil spill site; and
(2) The instrument must be calibrated with the specific weathered oil under field condi-
tions. Despite these difficulties, fluorometry has the potential to be the most definitive
t
measure of dispersant effectiveness in the field.
The following physical and chemical factors greatly influence the effectiveness of
dispersants in removing oil from the sea surface:
• type of oil, intluding chemical composition viscosity
• weathering of oil
• nature of oil spill
• sea state
sea characteristics, including salinity
• type of dispersant
• dispersant application method.
3.1 Types of Oil, Viscosity
The hundreds of different types of oils, which are composed of thousands of
hydrocarbon compounds, have different dispersibility characteristics. Some are easily
dispersed, and others will not disperse despite all efforts.
The American Petroleum Institute (API) gravity scale is used to classify crude
oils. As the density of the material decreases, the API gravity increases as follows:
API gravity =
141.5
specific gravity (60/60 °F)
- 131.5
where: Specific gravity (60/60°F) is the oil density at 60°F divided by the density
of water at 60°F.
API gravities for crude oils generally fall within the range of 5 to 50; oils with API grav-
ities below 5 are not dispersible (Gilfillan, 1992). An increase in API gravity generally
means a more dispersible crude oil.
Viscosity has a loose inverse relationship to API gravity, with high API gravity
crudes generally having lower viscosity. Viscosity alone can be a good indicator of dis-
persant effectiveness (Clayton, et al., 1992). Dispersants generally are most effective for
20
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oil viscosities of less than 2,000 centistokes (cSt), and almost no dispersion occurs over
10,000 cSt; sufficient data has not been published, however, to determine the usefulness
with such viscous oil. Some new dispersant formulations may be effective on particular
oil types above 10,000 cSt. Several references are available that give API gravities and
viscosities for many crude oils transported by sea in U.S. waters (API, monthly; Whiticar,
et al., 1993; NOAA, 1993).
Dispersant effectiveness is also affected by oil composition. The main hydrocar-
bon components of crude oil can be classified as saturates, aromatics, polars, and asphal-
tenes. There is a strong correlation between the saturate content of oil and the effec-
tiveness of present dispersant formulations. The greater the saturated hydrocarbon con-
tent (especially the saturates with less than 19 carbon atoms), the greater is the disper-
sant effectiveness. As the asphaltene content of crude oil increases, however, the ten-
dency to form water-in-oil emulsions also generally increases. Water-in-oil emulsions are
not easily dispersible.
3.2 Weathering of Oil
During the first 24 to 48 hours of an oil spill, the oil undergoes several substantial
changes as it is "weathered." Even though weathering continues beyond 48 hours, the
initial changes are generally the most dramatic. The term "weathering" includes the fol-
lowing processes: evaporation, dissolution, photooxidation, and emulsion formation.
The major influences on the weathering process are the composition of the oil and envi-
ronmental factors such as water temperature, sea state, and wind speed. The disper-
sibility of the slick is reduced by weathering and may in extreme incidences result in a 50
percent decrease in dispersant effectiveness in a matter of two to four hours.
The loss of volatiles from an oil slick through evaporation increases the concen-
tration of nonvolatiles, which causes an increase in oil density, viscosity, and surface
tension. Some lower-weight aromatics with high solubilities will dissolve in the water
column or quickly evaporate at the slick interfaces (Mackay and Chau, 1984). The oil-
aging process decreases API gravity and increases viscosity, which leads to reduced dis-
21
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persibility. Within 48 to 72 hours, oil floating on the sea will have lost nearly all aro-
matic hydrocarbons that are lighter than naphthalene (Gilfillan, 1992).
Photooxidation, another natural-aging process, generally occurs too slowly to be a
factor to be considered during spill response decision making. Crudes with higher wax
content tend to be affected by photooxidation more rapidly than other crudes. This
exposure to air and sunlight may increase the tendency to form water-in-oil emulsions
(mousse).
Mousse will form with many oils in turbulent seas. Mousses generally are easily
formed if the oil contains waxes and asphaltenes. Emulsification results in a tremendous
increase in viscosity and reduces dispersibility because the dispersant will not effectively
penetrate the emulsion.
3.3 Nature of Oil Spill
The nature of the oil spill can influence the dispersibility of the slick, as occurred
during the Ixtoc well blowout in the Gulf of Mexico. In this situation, oil coming out at
high pressure under water became emulsified before it reached the surface. Because'
emulsified oil is more difficult or impossible to disperse, an underwater release can
severely reduce the effectiveness of the dispersants.
Fire can also reduce the effectiveness of dispersants because it results in the re-
moval of the lighter fractions of the crude. The residual oil thus becomes more viscous
and depleted of the components amenable to dispersion. These dispersible components
are necessary to form droplets of the more viscous fractions. The end result of a crude
oil fire at sea is a less-dispersible slick.
3.4 Sea State and Characteristics
The motion of the open sea provides the natural energy for dispersing treated oil
droplets into the water column. Wind, waves, and tide redistribute the oil slick and
cause changes in concentration. Mechanical dispersion occurs with wind speeds great
enough to cause breaking waves. Advection from daily tidal currents, wind-induced
22
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currents from sea breezes, and frontal mesoscale eddies redistribute the oil droplets
horizontally, while turbulent diffusion causes vertical movement as well.
During dispersant application, high winds require careful spray alignment so that
the dispersant is not blown away from the target. However, breaking waves from these
winds can hasten the dispersion process. High winds will also cause the slick to spread
quickly, thus reducing the response time for the use of dispersants. Untreated dispersed
oil may reappear on the surface after high winds have ceased because untreated oil tends
to form larger drops. Oil droplets formed by chemical dispersion are of approximately
the same composition as the oil slick, but smaller. Therefore, while the dispersant does
not appreciably change the density of the oil, the oil remains lighter than water, but with
decreased surface tension, and a minimum amount of energy will mix the oil droplets
into the water column.
Visual observation and the Beaufort Wind Scale can be used to correlate wind
speed and resultant wave actions. For example, if small floating material is in constant
motion or if wave crests at sea have scattered whitecaps, this gentle breeze is assigned a
Beaufort number of "3." A Beaufort code number of 3 correlates to a wind speed of 7 to
10 knots (Bates, et al., 1984). If the Beaufort number is above 5, dispersants probably
should not be applied since they will do,little to enhance the natural dispersion already
occurring (CONCAWE, 1988). The Beaufort wind scale is presented in Table B-8, Ap-
pendix B.
Properties of the water, such as temperature and salinity, will also affect disper-
sibility. Many of the current dispersant formulations increase in effectiveness with in-
creased salinity, up to a point. Dispersibility can decrease at salinities above 40 parts per
thousand or as the salinity decreases toward fresh water levels. Increased salinity can
lower the solubility of certain surfactants; thus, the correlation between effectiveness and
salinity will vary for different dispersant formulations. Decreased water temperatures
could increase viscosity of the once dispersible crude oil to such an extent that it could
not be effectively dispersed (NRC, 1989).
23
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3.5 Type of Dispersant
Current dispersant formulations contain 15 to 75 percent nonionic surfactants and
5 to 25 percent anionic surfactants. Nonionic surfactants used may include sorbitan
esters of oleic or lauric acid, ethoxylated sorbitan esters of oleic or lauric acid, polyethyl-
ene glycol esters of oleic acid, ethoxylated and propoxylated fatty alcohols, and ethoxy-
lated octylphenol (NRC, 1989). Anionic surfactants may include sodium dioctyl sulfosuc-
cinate and sodium ditridecanoyl sulfosuccinate. The main classes of solvents used in
current dispersant formulations are water-miscible hydroxy compounds and hydrocarbons.
Hydrocarbon solvents such as low-aromatic-content kerosene enhance the penetration of
the dispersant into more viscous oils.
3.6 Dispersant Application Method
Chemical dispersants may be applied by boat or aerial spray but, in any case, the
dispersant must contact the slick in order to be effective. Any dispersant falling outside
the oil slick is ineffective. Wind drift can reduce the effectiveness of the application by
drifting the dispersant away from the target.
The droplet size of the dispersant influences the effectiveness. To achieve proper
mixing, dispersant droplet size should be of the same order of magnitude or smaller than
the oil film thickness. Large dispersant droplets can penetrate the slick without disper-
sing in the oil. Physical properties of dispersants that influence dispersant droplet size
during application are viscosity, volatility, density, and surface tension (Fingas, et al.,
1992b). Application equipment must be compatible with the physical properties of the
dispersant in order to achieve proper droplet sizing.
The dispersant-to-oil application rate directly impacts the effectiveness of a dis-
persant. For planning purposes, manufacturers generally recommend dispersant-to-oil
ratios ranging from 1:10 to 1:20 parts dispersant to oil. As discussed later in Section 6,
the ratio should be determined through preplanning and observation. The dosage of
dispersant must be sufficient to reduce interfacial tension. Thick areas of the oil slick
require more dispersant than the thinner areas; thus, dispersant effectiveness may vary
over a slick if the dispersant is applied at a constant rate per unit area. The rate of
24
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application ratios over different parts of the oil slick may need to be changed to achieve
optimal effectiveness.
25
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SECTION 4
ENVIRONMENTAL FACTORS
Factors to be considered in evaluating the decision to employ chemical disper-
sants for oil spill control include the potential to obtain a balance between ecological
benefits and any adverse impact to marine organisms, wildlife, or plant habitats and the
potential, based on the factors discussed in Section 3, that an application of dispersants
will successfully disperse a significant fraction of the oil. Unless a successful recovery
operation can be mounted against an oil slick that is moving toward a biologically sen-
sitive area, an adverse environmental impact will result. Although dispersants can re-
duce the severity of impact to fragile habitats, they may impose temporary stresses in
other offshore areas because of higher short-term exposure to the toxic components of
oil. When deciding whether to use dispersants, one must weigh the tradeoffs between
the potential impact to the intertidal and shoreline communities by the untreated oil and
the potential adverse impact to water-column and benthic organisms by chemically dis-
persed oil.
Some environments are more vulnerable to longer lasting impacts of spilled oil
than are others such as mangroves, salt marshes, and exposed corals. Although chemical
dispersants can increase short-term toxicity in the upper water column, their use may be
the most appropriate response to certain oil spills. The use of dispersants does not pre-
clude the use of other recovery techniques. For example, dispersants can be applied at
the source and recovery can take place at the leading edge.
The American Society for Testing and Materials (ASTM) developed ecologically
based guidelines governing the use of dispersants in marine environments. These guide-
lines describe habitats in relation to possible dispersant applications. ASTM developed
these guidelines for the following areas: 1) bird habitats (ASTM F 1010, 1986),
26
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2) marine mammal habitats (ASTM F 929, 1986), 3) rocky shores (ASTM F 930, 1986),
4) sandy beaches (ASTM F 990, 1986), 5) gravel and cobble beaches (ASTM F 999,
1989), 6) coral reefs (ASTM F 932, 1986), 7) seagrass beds (ASTM F 931, 1986), 8) man-
grove swamps (ASTM F 971, 1986), 9) tidal flats (ASTM F 973, 1986), 10) near-shore
subtidal habitats (ASTM F 972, 1986), 11) offshore habitats (ASTM F 1002, 1986), 12)
salt marshes (ASTM F 1008, 1986), and 13) arctic habitats (ASTM F 1012, 1986).
In addition to ASTM guidelines, the American Petroleum Institute (API) pub-
lished recommended site-specific planning procedures pertaining to the use of disper-
sants (API, 1985). These procedures are based on physical factors rather than habitat
considerations. Table B-10 in Appendix B presents dispersant and other cleanup
methods recommended by API for various habitats. Recommendations for dispersant.
use are based upon the following zone characteristics:
Zone 1, Dispersant use recommended
- Sufficient mixing energy to allow dispersed oil droplets to be diluted and
distributed throughout a large volume of water.
- Ample distance from sensitive areas (e.g., bird nesting areas) so that dis-
persant use will not cause a disturbance.
»
- Significant reason to believe that the oil spill will reach and adversely af-
fect sensitive areas.
Zone 2, Dispersant use acceptable
- Same characteristics as Zone 1, but oil is not expected to affect sensitive
areas (i.e., trajectory of the spill is not directed toward sensitive areas.).
Zone 3, Dispersant use conditional
- Shallow or low-energy habitats.
- Located very near sensitive areas.
This third zone requires identification and evaluation of alternatives. In some cases,
chemical dispersants may be the best solution, particularly if stranding oil in sensitive
areas along the shore is likely to develop (Lindstedt-Siva et al., 1984). Even in shallow
27
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waters, the use of dispersants may be an advantage. Studies have indicated that treated
oil is less likely to be incorporated into benthic sediments (MacKay and Hossain, 1982;
API, 1986; NRC, 1989). Dispersants may have decreased effectiveness in shallow areas,
however, if less-than-adequate mixing energy is available. Thus, the assessment of trade-
offs becomes more complex, and a thorough knowledge of the specific ecosystem and
water circulation is important.
4.1 Concerns About Toxicity of Dispersants
*
After the tanker Torrey Canyon caused a major oil spill on the English coastline of
Cornwall in 1967, much effort was directed toward developing dispersants with low toxic-
ity. The dispersants used to control the nearly 1 million barrels of crude oil that spilled
from the Torrey Canyon consisted of high-aromatic-content degreasing agents that were
developed to clean tanks. The results were an ecological disaster: extensive mortalities
of animals and algae occurred immediately, and the natural recovery was severely slowed
and was still incomplete in some areas after 10 years. Because the biological impacts
along the shoreline were highly visible, dispersant response was not highly regarded
(NRC, 1989). Many environmental studies on newer-generation dispersants have been
published since the late 1960s; a good bibliography is contained in "Using Oil Spill Dis-
persants on the Sea" (NRC, 1989).
Dispersants change the rate at which volatile hydrocarbons are incorporated into
the water column (McDonald, et al., 1984). Chemically dispersed oil potentially releases
toxic water-soluble hydrocarbons to the water column more rapidly than a slick does; this
increased transient exposure should be considered when dispersants are used near sensi-
tive areas. The increased transient exposure is balanced by the more rapid dilution of
dispersed oil compared with a slick, however, and the net effect tends to be positive.
Although researchers have used very high concentrations of oil- and water-soluble
hydrocarbons in laboratory testing of dispersed oil on marine life in the field, natural
dispersion and aging of oil reduce the concentration and remove the toxic components
(Anderson, et al., 1987). Extrapolation from laboratory tests to conditions at sea and in
the complex ecosystems of intertidal zones has been unsatisfactory; yet it is clear that
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weathering reduces the toxicity of oil and that both natural and chemical dispersion in-
crease surface area and reduce the potential shallow water and shoreline exposure of
organisms to the oil.
Knowledge of the seasonal habits of marine populations in the response regions
provides information about the distribution of that population near the oil spill. Avail-
able data on seasonal habits (spawning and breeding) and migratory patterns of key
animal species need to be considered. The seasonal ecology of a specific location can be
extremely complex and varied. Fish, shrimp, mammals, and birds have different
responses to surface oil and dispersed oil, and competing factors such as fish and bird
breeding habits often will complicate the decision-making process regarding the use of
dispersants. Dispersants that remove oil from the water surface may provide effective
protection for marine birds and mammals while increasing the negative effect on larval
fish and shrimp populations. The least-controversial use of dispersants is on an oil slick
in deep water (greater than 10 meters) that is heading toward an ecologically sensitive
coastal area (Trudel, 1984). Other cases do not lend themselves to such easy evaluation
of the trade-offs.
With respect to dispersants alone, laboratory studies indicate that the acute lethal
toxicity of most dispersants to biota is low compared with the constituents and fractions
of crude oils and refined products. Although a wide range of sublethal responses in
biota has been observed, usually at high exposure concentrations, the sublethal effects of
dispersants at concentrations that may be expected to occur during a spill are only par-
tially understood. At recommended application rates, dispersants should not increase
significantly the lethal or sublethal toxicities of dispersed oils (Wells, 1989); however,
direct application of dispersants to seabirds and marine mammals must be avoided be-
cause dispersants destroy the water-repellency and insulating capacity of fur and feathers
(NRC, 1989).
With respect to dispersed oil, laboratory bioassays have determined that acute
toxicity generally does not reside in the dispersant, but primarily in the oil droplets (for
some species) and the low molecular weight and dissolved, aromatic, and aliphatic frac-
tions of the oil (for most species). Dispersed and untreated oil show the same acute
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toxicity-a conclusion obscured in much of the literature by many studies that quote oil
concentration as being the total oil per unit volume of the experimental system, rather
than the actual measured, dissolved, and dispersed hydrocarbon concentrations to which
organisms are exposed (NRC, 1989).
Scientists have documented a variety of acute effects on organisms and habitats
from both chemically dispersed oils and untreated oils. Organisms in the water column,
particularly in upper layers, experience greater short-term exposure from dispersed oil
compared with nondispersed oil. Long-term harmful effects to shallow water benthic or-
ganisms may be better reduced by chemically dispersing oil than by not treating the spill
(Wells, 1989). Laboratory research on mollusks, however, shows that high concentrations
of dispersed oil can be toxic (NRC, 1989). In areas having restricted water movement,
the acute effect of dispersed oil on some organisms or marine plants may be greater than
that of oil alone; however, intertidal habitats such as mudflats are less adversely im-
pacted by dispersed oil that is treated before it enters the habitat, and such habitats can
recover faster. Intertidal habitats do not benefit from dispersant application after the oil
reaches the shore (Wells, 1989). Measurable effects of dispersed or untreated oil on
commercial fisheries or their supporting food webs have yet to be fully verified. If such
effects do occur, however, they would be difficult to detect and measure effectively be-
cause of the mobility of most fish and many invertebrates, the natural variability of their
populations, and the effects of overfishing on stocks (NRC, 1989).
Using laboratory studies, scientists have also documented a variety of sublethal
effects to biota (e.g., changes in reproductive and feeding behavior) from dispersed and
undispersed oil, most at concentrations comparable to or higher than those expected in
the water column during treatment (1 to 10 ppm), but seldom at concentrations less than
those found several hours after treatment of an oil slick (less than 1 ppm). The. times of
exposure in the laboratory (24 to 96 hours) are much longer than predicted exposures
during slick dispersal in the open sea (1 to 3 hours), and the effects to biota would be
expected to be correspondingly less in the field (NRC, 1989). Bioaccumulation and
tainting occur to a greater extent in the short term in filter feeders because water column
concentrations are elevated. Over the long term, however, more bioaccumulation of oil
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occurs in deposit feeders when dispersants are not used. Some laboratory studies and all
field studies to date have shown that the biodegradation rate of dispersed oil is equal to
or greater than that of nondispersed oil (Wells, 1989).
Based on the foregoing, a variety of toxic and sublethal effects to water-column
and benthic biota may be anticipated from dispersed oil. Reduction of chronic exposure
is believed to be the key to reduction of biological impacts (Wells, 1989). In offshore
open water, concentrations of dispersed oil would be much lower than in shallower wa-
ter, or in waters with poor circulation, with correspondingly lower impacts (NRC, 1989).
Before a decision is made to use dispersants, the following advantages and disad-
vantages should be considered:
Advantages
- A dispersed slick reduces the possibility of some portion of thick patches
of oil reaching the shoreline.
- Dispersant-treated oil will not adhere as readily to structures, sediment,
or marine organisms, assuming that the dispersant is successfully applied.
- Water in oil emulsions (chocolate mousse) that are difficult to cleanup
mechanically or disperse chemically can be reduced by application of
dispersants.
- Rapid aerial application can cover a large area.
Disadvantages
- Because dispersants will never remove all of the oil (approximately 30
percent), shorelines, birds, and fish will still be affected even if disper-
sants are used properly and effectively.
- Concentration of dispersed oil (and dispersants) is increased in the first
few meters of water.
- Increased exposure of biota to oil droplets and dissolved oil components
can result in toxicity to organisms in the upper (1 to 10 m) water column
(McAuliffe et al., 1980; McAuliffe et al., 1981; NRC, 1989).
- Application requires approvals not needed with recovery methods;
sufficient stockpiles of dispersants and application equipment are
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expensive to build and maintain; dispersant application is limited to a
narrow time window and sea energy.
42 Chemical Dispersant Use Around Coral Reefs and in Shallow Waters
A decreased volume of water in the water column means the concentration of dis-
persed oil per unit volume is increased in shallow water. Another concern is that the oil
may become incorporated into the sediments with release to the water column over a
period of months. Areas less than 1 meter deep are generally thought to be more sensi-
tive to dispersed oil, and*dispersants should be used in this case only when the tradeoffs
of leaving untreated oil arc known to be highly severe. An example of a sensitive shal-
low-water environment is a coral reef. Coral reefs are susceptible to oiling by direct
contact during low water and breaking wave action. Direct oiling of corals can be dead-
ly, and dispersant use to prevent such an occurrence should be considered. Evidence
exists that coral reefs are slightly more susceptible to dispersed oil than to floating oil
(LeGore et al., 1989). Increased sensitivity should be weighed against the possibility that
other habitats might be affected by the untreated oil, and the final decision should be
based on the least overall impact. The ASTM guidelines recommend the following
course of action:
Whenever an oil spill occurs in the vicinity of a coral reef, use of disper-
sants should be considered to prevent the bulk of the oil from reaching a
reef.
The decision to use dispersants to treat oil that is in direct contact with a
reef should be considered carefully and based upon the type of oil and
location on the reef.
Coral reefs in shallow waters are high-priority habitats and should be pro-
tected during oil spills; therefore, dispersant use on oil spills over these
reefs is not recommended, but oil in the vicinity should be slowed from
reaching the reef.
Dispersant use to treat oil over a reef should be considered only if the
water depth is 10 meters or greater.
Dispersants are not recommended on oil spills over reefs with low water-
exchange rates such as lagoons and atolls.
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4.3 Dispersant Use in Breeding Areas
Because breeding is a seasonal phenomenon, response plans for dispersant use (as
presented later in Section 5) should identify key species, times of year, and areas that
could be affected should an oil spill occur. Fish will breed in both shallow and deep seas
depending on the species, but usually within the top few meters of the water column.
Fish that reproduce only once per year could potentially have a whole generation elim-
inated in an affected area if spilled oil is present. It is unlikely, however, that all of the
breeding areas would be affected by a spill. Biologists are uncertain of the long-term
effects of dispersed oil on productivity, but laboratory studies have shown that exposure
to total petroleum hydrocarbon concentrations in the range of 0.01 to 1 ppm for more
than 7 days can cause abnormal development and decreased survival in larval fish and
crustaceans (U.S. EPA, 199la). The possibility of fish and larvae migrating into the oil
spill area should also be considered (NRC, 1989).
4.4 Dispersant Use in Bird Habitats
Bird populations are vulnerable to oil spills, but dispersants can be used to reduce
the amount of oil reaching the populations. Adult birds have a high mortality rate even
when they are moderately oiled, and birds coated with oil can carry the oil back to their
nests where the eggs can be contaminated by the transferred oil. These effects can be
reduced by moving the birds, mechanically removing the surface oil from the sea, or
chemically dispersing the oil into the upper water column before the oil reaches the
birds or their habitat (ASTM F 1010, 1986). Birds should not be sprayed with disper-
sant, as this will reduce water repellency of their plumage. Dispersant use to prevent oil
from reaching bird breeding and nesting areas is generally accepted, but other mitigating
factors such as dispersant effects on fish could cause controversy; therefore, all environ-
mental effects must be considered before the decision is made to use any chemical
dispersants.
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4.5 Intertidal Habitats
Intertidal habitats, which are found worldwide, can have much greater densities of
marine organisms and edible marine species than offshore areas. In addition, intertidal
habitats serve as nurseries and support sensitive life stages for various species. Recovery
and cleanup of oil in an intertidal zone are difficult and likely to cause considerable
adverse environmental impact (ASTM F 972, 1986; Hoff et al., 1993).
Some examples of sensitive intertidal habitats are mangroves and salt marshes.
Mangroves found in tropical and subtropical areas protect shorelines from storms and
currents. They also provide habitats and nurseries for shellfish such as lobsters and
prawns. Although this is one of the most vulnerable habitats to spilled oil (Gundlach et.
al., 1978), no active cleanup method has been proven effective for oiled mangrove forests
(API, 1985). Recent research is conflicting on the ability to clean previously oiled man-
groves (Baker, et al., 1993; Teas, et al., 1993), but oil already dispersed is less harmful to
mangroves than untreated oil. Dispersant operations should therefore be considered
even at the shallow fringe of a mangrove forest (ASTM, F 971, 1986).
Salt marshes are considered to be almost as vulnerable to spilled oil as are man-
groves. Because these marshes are located in sheltered areas, any mixing action from
the water is limited and dispersant effectiveness is low. Dispersants should be used off-
shore to protect salt marshes from spilled oil if the oil could potentially enter the area.
Because timing is important, dispersants should be applied as far away from the salt
marsh as possible and at a time when the tide starts to rise (ASTM F 1008, 1986).
4.6 Dispersant Use in Other Habitats
Dispersants are not generally found to greatly enhance cleanup of rocky, cobble,
or sandy beaches (Baker et al., 1993). The wave action on rocky beaches is helpful in
removing the oil and dispersing it naturally. API recommends natural cleansing as the
best cleanup option for rocky beaches (API, 1985). When these rocky beaches are home
to mollusks or barnacles (all very sensitive to oil), however, dispersants may be con-
sidered to prevent oil from reaching these sensitive areas (ASTM F 930, 1986); again,
timing is important.
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Sandy or cobble beaches may contain simple marine communities or complex
food sources in the organic-rich sediments. Again, natural cleansing is recommended for
these areas (ASTM F990 and F999, 1986). The habitats found there are equally sen-
sitive to disturbances from physical cleanup measures and to the problems created from
the presence of spilled oil. Decisions to use dispersants to keep the oil from reaching
these areas should be based upon whether these beaches are used by birds, mammals, or
spawning fishes (ASTM F 999, 1986). In order to expedite the decision-making process
concerning the use of dispersants, preapproval plans for dispersant use (discussed in Sec-
tion 5) are needed to identify specific shoreline areas where oiling might cause signifi-
cant harm.
Arctic areas (above 66 degrees north latitude) may not benefit from dispersant
use if low temperatures associated with these areas restrict the effectiveness of disper-
sants. Newer formulations of dispersants may be effective at lower temperatures. Safety
of response personnel is of greater concern in arctic areas where mishaps can have more
severe consequences due to hyperthermia. Therefore, the "no cleanup option" should be
considered in these areas unless a recovery operation can be safely and effectively imple-
mented (ASTM F 1012, 1986).
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SECTION 5
REGULATORY AND ADMINISTRATIVE ASPECTS
The Federal law 'pertaining specifically to oil spill response actions is the Clean
Water Act (CWA) as amended by the Oil Pollution Act of 1990 (OPA). The National
Oil and Hazardous Substances Pollution Contingency Plan, or simply the National Con-
tingency Plan (NCP), was promulgated pursuant to Section 311 of the CWA to regulate
all response activities. The OPA is a comprehensive statute designed to expand oil spill
prevention activities, establish new federal authority to direct responses to spills, improve
preparedness and response capabilities, ensure that shippers and oil companies are
responsible for impacts from spills that do occur, and establish an expanded oil pollution
research and development program. This section highlights the scope of these laws and
addresses the necessary steps for dispersant use.
5.1 National Contingency Plan
The NCP provides the foundation for the national planning and response system
concerning oil spills. According to the NCP, the On Scene Coordinator (OSC) has the
authority to direct the removal and cleanup efforts. The OSC, with the concurrence of
the Regional Response Team (RRT), determines whether dispersants or other chemical
or biological agents will be approved to respond to an oil spill. Where hazards to human
life are involved, the OSC has the authority to approve the use of dispersants unilateral-
ly. Coast Guard OSCs are assigned to the coastal and offshore zones, and EPA OSCs
are assigned to the inland zones. The boundaries of these zones are determined by EPA
and U.S. Coast Guard agreements identified in the Regional Contingency Plans (RCPs).
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5.1.1 Scientific Support
The NCP has identified certain organizations that are available to assist OSCs in
preparing response strategies. The Environmental Response Team (ERT) established by
EPA has expertise in biology, chemistry, hydrology, geology, and engineering and can
provide assistance and advice to the OSCs. Information may be obtained from the
ERT, U.S. EPA, Edison, New Jersey [Phone (908) 321-6740 or (908) 321-6660 (24
hours)].
Under Section 300.145(c) of ,the NCP, Scientific Support Coordinators (SSCs) are
generally provided by the National Oceanic and Atmospheric Administration (NOAA) in
coastal and marine areas and the Great Lakes, and by EPA in inland regions. NOAA.
has nine regional SSCs and a scientific support team that include expertise in environ-
mental chemistry, oil slick prediction and tracking, pollutant transport modeling, natural
resources at risk, environmental trade-offs of countermeasures and cleanup, and informa-
tion management. During a response, the SSC leads the scientific team that serves
under the direction of the OSC and is responsible for providing scientific support for
operational decisions and for coordinating on-scene scientific activity. Depending on the
nature of the incident, the team integrates expertise from governmental agencies, univer-
sities, community representatives, and industry to assist the OSC in evaluating the
hazards and potential effects of releases and in developing response strategies. OSC
requests for SSC support can be made directly to the SSC assigned to the area, to the
NOAA member of the Regional Response Team, or by calling NOAA's Hazardous Ma-
terials Response and Assessment Division in Seattle at (206) 526-6317.
5.1.2 NCP Product Schedule
Section 311(d)(2)(G) of the CWA, as amended by the OP A, requires that the
NCP include a schedule identifying dispersants, other chemicals, and other spill mitigat-
ing devices and substances, if any, that may be used in carrying out the NCP.
The use of dispersants, other chemical agents, and biological additives to respond to oil
spills in U.S. waters is governed by Subpart J of the NCP (40 CFR 300.900).
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Section 300.910 of Subpart J concerns the authorization of the use of products on
the NCP Product Schedule and specifies the conditions under which OSCs may authorize
the use of dispersants, other chemicals, and other spill control agents. Under existing
Section 300.910(a), OSCs may authorize the use of products on the Product Schedule,
with the concurrence of the EPA and state representatives to the RRT and, when prac-
tical, in consultation with the Department of Commerce and Department of Interior
natural resource trustees.
Sections 300.915 and 300.920 describe the data requirements and the process used
for adding a product to the Product Schedule. Currently under Subpart J, to list a prod-
uct on the Schedule, a manufacturer must submit technical data on the product to EPA.
Data on dispersants, surface collecting agents, and miscellaneous oil spill control agents
must include the results of the Revised Standard Dispersant Toxicity Test set for these
products in Appendix C of the NCP. Data on dispersants must also include the results
of the Revised Standard Dispersant Effectiveness Test. Conducted at the expense of the
manufacturer, these tests must be performed by a qualified laboratory.
The raw data and a summary of the results from these tests are then submitted to
EPA, where they are reviewed to confirm that the data are complete and that the spe'ci-
fied procedures were followed. This list is updated as EPA receives additions to the
schedule and verifies that the required data were submitted. Generally, EPA does not
confirm the data from independent tests. The data requirements for placement of a
product on the Product Schedule are designed to provide sufficient data for OSCs to
judge whether and in what quantities a product may be used to control a particular dis-
charge.
Inclusion of a product on the Product Schedule means only that the data submis-
sion requirements have been satisfied. The listing of a product on the Schedule does not
mean that the product is recommended or authorized for use on an oil discharge. In
addition, placement of a product on the Product Schedule does not imply that EPA has
confirmed the safety or effectiveness of the product or in any other way endorsed the
product for the use listed or for other uses. The purpose of the standardized testing
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procedures is to ensure that OSCs have comparable data regarding the toxicity, effec-
tiveness, and other characteristics of different products.
The standard toxicity test provides data on the relative toxicities of the dispersant
products on commonly used test species under standardized conditions. The Revised
Standard Dispersant Toxicity Test uses the saltwater mummichog (Fundulus heteroclitus')
and the brine shrimp (Artemia salina) as its required test species for fish and inverte-
brates, respectively. At the end of a specified test period, a median lethal concentration,
or LC50, is calculated using the observed mortalities of the organisms from the toxicity
tests. The LC50 is the concentration of a particular dispersant that is lethal to 50 per-
cent of the organisms over the course of the test. Using the LCSO's, the toxicity of a
dispersant can be compared to that of oil and a mixture of the two.
There is concern whether the two test species used in toxicity testing are commer-
cially available and easily cultured. Consequently, EPA is considering a change to the
fish species Menidia beryllinia. the silverside, and to the invertebrate species Mysidopsis
bahia. the mysid shrimp.
The current listing procedure does not include an effectiveness criterion; however,
such a criterion is being considered by EPA (Sullivan et al., 1993). The current list of
almost 50 dispersants would be greatly reduced if a laboratory effectiveness threshold of
50 percent ( + /-5 percent) were established. A current product schedule can be obtained
from the Emergency Response Division (5202G), Oil Pollution Response and Abatement
Branch, U.S. Environmental Protection Agency, Washington, D.C. 20460 (Hotline phone:
202-260-2342).
5.2 Oil Pollution Act
The OPA requires that Area and Regional Contingency Plans for oil spill
response be developed and that procedures regarding the use of dispersants on oil spills
be identified. Areas and regions for oil spill response and planning organizations are
designated in the OPA. There are 13 RRTs consisting of 10 regions, 2 territories, and
1 commonwealth.
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Section 4202(a)(4) of the OP A, which requires the establishment of Area
Committees, states that the Area Committees shall "work with state and local officials to
expedite decisions for the use of dispersants and other mitigating substances and de-
vces.
5.21 Response Planning
RRTs have been organized to provide regional planning and spill response. RCPs
developed by response team members and federal, state, and local officials provide gui-
dance material for a response to oil and hazardous material spills. These plans describe
federal and state authority to respond to spills and introduce protocols for chemical
dispersant use. Each office of the RRT Co-Chair has a copy of the RCP.
Area Contingency Plans (ACPs), unlike RCPs, are action plans that are specific to
oil. An ACP will define worst-case incidents and describe the actions necessary to
respond. The plan lists available equipment, location of the equipment, and personnel
that can be utilized during emergency situations.
5.22 Approval Plans for Dispersant Use
Dispersant use requires preplanning and the development of an approved plan.
The procedures to be followed for obtaining permission for the use of dispersants are
specified in RCPs. Regional response team members should develop a preapproval plan
for specific dispersants and oil types. If preapproval has not been established through a
prespill preapproval plan, the OCS may authorize the use of products on the Product
Schedule with the concurrence of the EPA and state representatives to the RRT and,
when practicable, in consultation with the Department of Commerce and Department of
v
Interior natural resource trustees. Valuable response time can be lost in this situation
because the RRT is unlikely to grant approval for dispersant use in less than 6 hours
after a spill. Thus, the preapproval plan allows quick decision making and quick action
in responding to specific oil spills.
Prespill plans identify acceptable and unacceptable potential dispersant-use zones
and seasons and take into consideration variations in state restrictions on dispersant use
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and authorization for use. Spill models may be incorporated to help predict landfalls
and to relate predicted landfalls with sensitivity maps.
Plans developed for dispersant preapproval should include at a minimum the
following information:
Descriptions of the types and volume of oil transported throughout the
region. ,
Discussion about the dispersibility of the types of oil transported through
the region.
Descriptions of sensitive areas that would be adversely affected should a
spill occur.
Descriptions of seasonal habits of fish and wildlife in the region.
Descriptions of the following types of information that must be collected
before a decision to use the dispersant can be made:
Circumstances of the spill and type of oil
Properties of the spilled oil
Weather conditions and spill trajectory (can be provided by NOAA),,
Descriptions of the dispersants available.
• Descriptions of the equipment to be used to apply the dispersants.
Descriptions of monitoring to be performed in the dispersant area.
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SECTION 6
APPLICATION OF DISPERSANTS
This section describes the application equipment and the logistics involved in
applying dispefsants. It provides sufficient detail to allow an OSC who has decided that
the use of dispersants is warranted to plan and conduct the dispersant spraying operation
in a manner that will achieve the maximum effect. This information is not intended as a
design guide for dispersant equipment. The application information presupposes that
commercially available and calibrated equipment are ready for deployment. Appendix A
contains information on equipment that may be available. The basic organizational
aspects of a spill response using dispersants are similar to recovery operations and are
-not discussed in detail here. Specific organizational aspects appropriate to dispersant use
will be discussed to supplement existing planning.
Two of the most significant hurdles to overcome in the effective use of dispersants
are the lack of a dispersant supply and insufficient availability of application equipment.
Proper planning should not only address the decision method for choosing dispersant
use, either alone or with other response strategies, but also identify the source for the
dispersant and the means to obtain the proper application equipment (USCG, 1993).
6.1 General Principles of Dispersant Application
Techniques used to apply dispersants on an oil slick are generally less controver-
sial than either the effectiveness of the dispersant or its environmental impacts. The
application often is not effective, however, because of poof mixing, the use of inadequate
application techniques (such as poor targeting and distribution of aerial sprays), the
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possibility that the oils were not dispersible, or poor formulation of the dispersant (NRC,
1989). Also, a major controversy concerns how to determine the field effectiveness of
the dispersant. Guidelines for determining dispersant effectiveness in the field are dis-
cussed in Section 7. Once the decision has been made to use dispersants, the technical
aspects of application are comparatively straightforward. Yet, there are often a myriad
of logistical problems, including getting enough equipment, getting dispersants and other
supplies and doing everything within a short (24-48 hour) timeframe.
The following general principles of dispersant application underpin all operational
and design considerations:
Apply dispersant without dilution. Although some boat spray systems may
contain equipment for dilution, predilution of the dispersant with sea water
appears to reduce its effectiveness. Dilution also requires additional un-
necessary mixing equipment.
Ensure contact of the dispersant with the oil to achieve effectiveness.
Dispersant that falls on the sea will be ineffective even if the slick
subsequently moves over the treated area.
Apply dispersant to the leading edge of a spill or the thickest part. The
leading edge or the dark windrows of oil in a slick contain the largest con-
centration of the oil even though their area may only represent a small
fraction of the total slick. By many estimates, 90 percent of the oil is gen-
erally found in 10 percent of the areal extent of the slick (Audunson, 1984).
Apply dispersants as soon as practical after the oil spill occurs. The least-
controversial aspect of dispersant effectiveness is that oil is less easily dis-
persed as it ages. Rapid response is the single most significant controllable
factor related to effectiveness when oil dispersants are used.
Apply dispersants as close to a continuing spill source as possible. The
dispersant will have the maximum effectiveness near the source, where the
oil is the freshest and thickest.
Do not apply dispersant to oil sheen. The silvery oil or even rainbow-col-
ored oil generally is less than 0.005 mm thick and may be as low as
0.001 mm thick. Sheens have a greater chance for natural dispersion and
have a lower efficiency for chemical dispersion since dispersant drops often
pass through the sheen without interaction.
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Observe the action of the dispersant from both the air and the surface.
The effectiveness of the dispersant in removing oil from the surface must
be observed throughout the application. Although visual observation
merely provide a subjective opinion of the effectiveness, it is the only guide
that is practical on a real-time basis. When the slick does not appear to be
affected by dispersant application, it is time to reassess the response (see
Section 7 for observation guidelines).
• Adjust application rate to achieve optimum effectiveness. Dispersants have
varying degrees of effectiveness depending on the crude oil, its age, and the
thickness of the slick. Adjustments in the field can result in the optimum
quantity of dispersant being used to achieve satisfactory dispersion.
Do not apply dispersants in the immediate vicinity of recovery operations.
Dispersant spraying near recovery equipment can render some equipment
ineffective. Many recovery devices rely on the ability of oil to adhere to
certain materials preferentially (e.g., moving belt skimmers). Dispersant
overspray landing on such equipment will reduce oil adherence to the
skimming device.
The aforementioned general principles may have exceptions in special cases, but such
cases are rare.
Similar to the general principles, the following rule of thumb can be used in the
planning stage and during the initial response. Dispersant application planning and the
initial response should be based on an application ratio of between 1:10 and 1:20 parts
of dispersant to oil. This range has been derived from laboratory studies and practical
observations and requires field adjustment to achieve optimal performance. In a spill
situation, the oil tends to spread rapidly and can achieve a thickness of 0.1 mm in a
matter of 1 or 2 hours (NRC, 1989). At this thickness, the 1:10 to 1:20 ratios translate to
about 50 to 100 liters per hectare (5 to 11 gallons per acre). Without specific knowledge
of slick thickness and dispersant effectiveness on the slick, the initial response effort
should first start with a higher, application rate and then be reduced until the optimum
rate is achieved.
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62 Marine Vessel Application
The use of marine craft was the only common method of dispersant application
until the 1980s. With the success at Bantry Bay of aerial spraying, more effort has been
put into the aerial application route (NRC, 1989). Marine vessels offer several
advantages over aircraft in the application of dispersants. In planning for spill response,
the following advantages should be weighed against the disadvantages inherent i.n marine
craft.
6.2.1 Advantages
Most coastal areas have a large pool of potentially suitable vessels and experi-
enced mariners. Mariners familiar with the vessels and the coastal region are often
readily available even in the absence of trained response teams. Vessels can be easily
chartered with full crews and necessary insurance in a very short period. The legal docu-
ments for chartering have been in place for years and are well known. Chartered vessels
of opportunity can be rigged with portable dispersant spraying equipment maintained in
the region or flown in from nearby depots. The rigging is not complex and can be done
quickly. Marine craft can provide flexibility in dispersant use. Because small vessels can
work comparatively closer to the shore, they are able to tackle smaller slicks and patches
with precise application. Large vessels containing thousands of gallons of dispersants can
be stationed and provisioned near a continuing source for days or even weeks at a time.
Support such as fuel, docks, provisions, and repairs for both small and large vessels are
common in most coastal areas.
6.2,2 Disadvantages
The major disadvantages of marine craft use are all related to their speed and the
inability of a boat captain to see the limits of the spill. Vessels that might be used to
spray dispersants generally have a top speed to get to the spill site of less than 25 knots
and while on station an application speed of less than 10 knots. These vessels can re-
quire 6 to 8 hours to get from port to the site of a spill even though the spill may be
only a few miles off shore but not near a port. Once at the spill site, the treatment capa-
city of marine craft is usually limited to approximately 15 to 60 acres per hour at 10
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knots, depending on the equipment (Appendix B). The area that can be treated is-often
limited by the travel .time between thicker patches of oil. As with any vessel spill
response, application of dispersants from boats can lead to nausea problems among
workers as a result of the combination of the rolling sea and odor of fresh crude. The
efficiency of an operation can be severely reduced in such circumstances.
6.2.3 Equipment
Equipment used to apply dispersants from marine craft is relatively simple and
consists of four basic components: dispersant storage, delivery pump, metering device,
and delivery system. The equipment should be built specifically for dispersant appli- .
cation to ensure compatibility in specifications between components. Thus, the pumps,
meters, booms, and nozzles or fans are designed to work as a system. The system is
designed for adaptation without modification to a particular set of vessel specifications.
The vessels that are suitable mounting platforms must be compatible with the delivery
system specifications. The equipment must have clear and concise instructions for instal-
lation and operation, especially if portable equipment is to be used on a vessel of oppor-
tunity.
Figure 6-1 shows a common dispersant delivery system that utilizes a boom
mounting arrangement. The length of the boom depends on the dimensions of the ves-
sel. Booms generally vary in length from 3 to 12 m (10 to 40 ft) long depending on the
vessel size. Booms may have nozzles mounted directly on the frame or mounted on
extension lines that hang from the boom. Nozzles should be from 2 to 3 m (6 to 9 ft)
from the sea surface. Smaller craft can have nozzles located closer to the sea surface,
and the nozzles need to be designed for that height. Booms must be short enough so
that the nozzles will not hit the sea surface as the vessel rolls during dispersant ap-
plication. As seas become higher, dispersant operations must be halted and booms
brought in and secured.
The nozzles and their mounting must be designed to provide a mean volume
dispersant droplet diameter on the order of 500 to 700 jum in a fan-shaped overlapping
pattern, as shown in Figure 6-2. Droplets that are smaller tend to blow on deck or away
46
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1. Dispersant tank
2. Pump
3. Electro valves
4. Telecommand
5. Spray arm
6. Front sprayer
Figure 6-1. Dispersant delivery system using a boom-mounted arrangement
(adapted from CONCAWE, 1988).
Figure 6-2. Spray arm system with overlapping spray pattern
(adapted from CONCAWE, 1988).
47
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from the intended target, and larger droplets penetrate through the slick. The booms on
the vessel are placed toward the bow so that the dispersant will strike the slick before
being disturbed by the bow wave. The equipment manufacturer may need to supply
more than one set of nozzles, depending on the dispersant viscosity or the distance to the
water.
An alternative to the boom system is a ducted fan system (Allen, 1985; Barbou-
teau, 1987). Nozzles spray dispersant into an air stream created by a powerful fan. The
resultant spray can accurately distribute the 500- to 700-^m droplets up to 24 meters (80
feet) from the boat. The system requires a higher degree of operational sophistication
because of the effects of wind on the spray pattern. The system may not be appropriate
for dispersant application if wind speeds exceed 15 knots (CONCAWE, 1988). On both
the boom and ducted fan systems, the dispersant flow rate must be calibrated at various
meter or pump settings. Since the vessel speed and dispersant flow rate determine the
application rate, the vessel master must be able to easily correlate the meter readings to
the vessel speed to determine the application rate per unit area. Usually the vessel is
maintained at a constant speed between 5 and 10 knots, and the dispersant metering
system is to be adjusted to maintain the flow at the desired rate. The calibration for a
particular spray system could consist of a set of six plots of dispersant controller settings
versus the areal application rate for ship speed at 1-knot intervals between 5 and 10.
knots.
6.2.4 Application
Prior to the commencement of a dispersant operation, the quantity of dispersant
on each vessel should be inventoried. Daily logs of dispersant use should be maintained
to enable a rough approximation of its effectiveness to be determined on a daily basis.
Inventory reconciliation can determine dispersant overuse and equipment malfunctions.
Application of dispersants from marine craft.requires direction from aircraft in
order to achieve the maximum benefit for oil spill control. Communication between the
vessel and the aerial observer requires appropriate radio equipment with compatible
channels. The aerial observer acts as the coordinator to direct vessels to the thicker
48
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patches of the slick and then provides feedback to the vessel on the effectiveness of the
operation as seen from the air. The airborne observer needs to provide the vessel
master with a description of the slick with respect to alignment and suggest a direction of
attack in order to allow the vessel master to make the approach as efficient as possible.
If multiple vessels have approached the slick in order to spray in a staggered formation,
it is even more important to have clear instructions from the aircraft observer to avoid
spraying already treated oil.
Upon instructions from the observer or by direct observation, the vessel master
should begin spraying at the preselected rate. On first approach to a spill, the rate may
be as high as 90 liters/hectare (10 gallons/acre). This rate may.be lowered, based on
the results seen by the aerial observer. As experience is gained with a particular slick,
adjustments can continue to be made around a narrower application rate as the oil ages
or as thicker patches are encountered.
The vessel normally must be kept at speeds of less than 10 knots to avoid having
the bow wave push away or submerge the oil before treatment and to avoid wind spray
of dispersant onto the deck of the boat. The vessel speed also must be reduced as winds
pick up and blow the dispersant on deck. Although dispersants are not toxic, they can
cause skin irritations and breathing difficulties if inhaled. Additionally, if decks become
coated with dispersants, they become slick and hazardous to movement. Sea conditions
resulting from winds measuring over a force of 5 on the Beaufort scale are generally not
conducive to dispersant operations. When seas reach this level, there is not only a
greater tendency toward natural dispersion but wave action exposes more open water
instead of oil.
6.3 Aerial Application
Generally, aerial application of dispersants is preferred to vessel application be-
cause it has been found to be an efficient method for treating large areas in a short time.
As equipment has become more available around the world, more:experience has been
gained in large-scale aerial dispersant application that has been translated into more
effective techniques and better equipment. Because the logistics of an aerial spray
49
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operation are significantly different from other types of response, they are covered in
greater detail below. Aerial application appears to have largely replaced marine vessel
application as the preferred method for larger spills. Figures 6-3 and 6-4 are photo-
graphs of helicopters with suspended buckets. Figures 6-5 and 6-6 show a Fked Wing
Folker F-27 and a C-130 with an ADDS pack respectively applying chemical .dispersant.
6.3.1 Advantages
Aircraft have the advantage of speed. They can move from a home base to a spill
location staging area in a matter of hours. From staging areas, aircraft can fly to the
actual spill site usually in a matter of minutes. This is a significant advantage in a rapid-
response application in which the effectiveness of the dispersant is time-dependent.
Dispersant application per unit time is another great advantage of aircraft because
of their speed. Appendix A contains tables showing the relationship of carrying capacity
of an aerial dispersant system to the area capable of being treated per unit time.. These-
tables show that even a small helicopter-borne spray device can usually outperform the
largest vessel. This ability is even more apparent when the slick is broken up in scat-
tered windrows that require significant vessel travel time between thicker patches.
6.3.2 Disadvantages
Only a limited number of aircraft, equipment, and personnel are capable of apply-
ing aerial dispersant. Dispersant-equipped aircraft may be located many hours of flight
time from a staging base. Compared with marine craft, aircraft of convenience are
generally not as available. Although portable equipment can be installed on certain
fixed- and rotary-wing equipment, other considerations often restrict its use to specific
aircraft. One of the major restrictions involves insurance and contracts. Unless contrac-
tual arrangements are made in advance, complications in reviewing the legal instruments
can negate all of the speed advantages of aircraft.
Another restriction is the availability of trained pilots and crew. Aerial ap-
plication requires special training for handling aircraft at low altitudes. Also, the related
50
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51
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Figure 6-5. Photograph of a fixed-wing F-27 applying chemical dispersant.
Figure 6-6. Photograph of a C-130 with ADDS pack.
52
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equipment generally requires a special crew and maintenance personnel. A high degree
of pilot skill is required to ensure that dispersant spray makes contact with the floating
oil.
Shoreside logistics involving an aerial spraying operation are more complex and
require a significant amount of preplanning. An efficient operation requires that facil-
ities be located as close to the spill as practical. Aviation facilities typically are not set
up to handle the special requirements described in the logistics section for a spray
operation (e.g., easy access by delivery crews, and utilities and water at loading site).
Further, it is difficult to target application to a nonuniform spill.
6.3.3 Equipment
Aerial spray equipment can be divided into three broad categories based on the
aircraft used: small fixed-wing, large fixed-wing; and rotary-wing (helicopters). The
small fixed-wing aircraft are similar to crop dusters. Such equipment specifically desig-
nated for handling oil spill dispersants is not commonly available in the United States,.
Although a crop duster can be used as an oil spill dispersant aircraft, it is not recom-
mended because the dispersant could be contaminated with residual pesticides and herbi-
cides and result in greater environmental problems unless the tanks are properly cleaned.
Even with clean tanks, a crop duster may have inappropriate nozzles and application
rates for use with dispersants and lack a radio for air-to-air communication.
Helicopters equipped with sling hooks can be used with special dispersant spray
buckets. Also, dispersant spray devices can be installed within the cabin of a Bell 212
helicopter. The helicopter-borne buckets are designed to carry from 200 to 3000 L (100
to 800 gal) and are self-contained. Generally smaller buckets that will hold three or four
drums of dispersant are more common since they can be used on a wider variety of
helicopters. The spray unit comes equipped with pumps, nozzles, and controls. These
systems can be transported to the staging area by truck or air and are ready for use upon
arrival.
The larger fixed-wing equipment is available in two types: a permanently
mounted unit installed in the aircraft and portable equipment. Only a few dedicated
53
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U.S. aircraft are equipped with permanently mounted units. These aircraft are on con-
tract to spill cooperatives and are on call at all times for spill response. The aircraft in
use are older piston-powered planes, such as DC6's, DC4's, or DC 3's with maximum
capacities of about 13,600 L (3,600 gal), 9,800 L (2,600 gal), and 5,700 L (1,500 gal)
respectively. Nozzles of specified sizes and spacing are attached to a spray unit on
booms mounted along the wings of the aircraft to provide spray droplets of the right size
to be effective at a specific air speed and altitude. Use of dispersants with substantially
different viscosities than the design viscosity can adversely affect the characteristics of the
spray, and hence the effectiveness of the dispersant.
Systems are available for C-130 (Hercules) type aircraft. The U.S. Air Force has
a recently developed system known as the Modular Aerial Spray System (MASS). The
Airborne Dispersant Delivery System (ADDS-Pack) is a commercially available system.
Both of these systems are designed to be mounted on a Hercules aircraft. Not
necessarily any Hercules aircraft of convenience can be used, but more than a few are
suitable. There may be contractual difficulties in using an aircraft of opportunity and
this must be considered in the spill planning phase. The booms are fixed to the spray
system and extend on either side of the aircraft. The spray units contain all pumps and
controls needed to make them self-contained. The MASS unit is capable of carrying
7,600 L (2,000 gal) of dispersant, and the ADDS-Pack can carry about 21,000 L (5,500
gal). Neither of these units have been used extensively on U.S. spills.
6.3.4 Logistics
An effective aerial spray operation often depends on numerous logistical local re-
strictions in the planning and execution phase. For example, some areas restrict the
transport of helicopter-slung loads over highways and commercial areas. Similarly, use
or access to commercial aviation facilities may be restricted without the normal airport
security clearances that often take significant time to obtain for support personnel. Pre-
planning on the local level must include such special considerations in order to avoid lost
time and disruptions during a response. The following discussion presents some of these
considerations, but planning must be done at a local level and in detail.
54
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The area coverage of an aerial dispersant operation depends on the aircraft turn-
around time-trie time it takes to travel from the staging area to the spill site, return, and
take off for another run. The actual application time represents only a small fraction of
the total turnaround time. The majority of the turnaround time is travel time and
ground time to prepare the aircraft for the return flight. Distance between the staging
area and the spill site can have a significant effect on the turnaround time, as can the
. ground activities. A staging area located as close as possible to the spill site is the best
choice, especially for helicopter application, since loaded helicopters fly at 100 knots or
less and carry much smaller loads. .
The staging area equipment must be compatible with the aviation equipment and
operated efficiently. Aviation equipment from aircraft fuel tanks to dispersant tanks may
require special fittings. Compatible fittings must be available on the ground-support
equipment in order to refill both dispersant and fuel tanks. Dispersant transfer from 55-
gallori drums can appreciably slow operations. Larger transfer tanks with high-capacity
pumps can reduce the ground time by an order of magnitude. Advance planning for
dispersant operations should consider the transfer capacity as a potential limitation to
operations and make provisions for portable tanks and suitable pumps to be brought to
the staging area.
The staging area should include sufficient space for the aircraft and dispersant
storage. The work area needs to be remotely located from other activities that can inter-
fere or pose hazards. Helicopters have much more versatility in this respect because
they allow areas to be selected that are removed from other activities. Fixed-wing air-
craft require an airport and do not have the same flexibility; they need a large work area
for turnarounds. The staging area needs to be equipped with communications that can
contact both the aircraft and other outside facilities. A source of washdown water is also
important to- deal with the frequent spills and drips of dispersant during loading opera-
tions. Dispersant can soften asphalt and make concrete slippery.
Aircraft refueling capability is necessary to maintain a continuous operation.
Older piston-driven aircraft require aviation gasoline that may not always be available in
sufficient .quantities at smaller airports. Helicopters use jet fuel. Provisions for obtaining
55
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fuel must take into account the type of aircraft to be used. Planning for dispersant
operations using helicopters offers the potential for operations from an offshore platform
close to the spill site. In this case, fuel and dispersant must be brought to the platform
to minimize turnaround time.
6.3.5 Application
Application from aircraft is based on the general principles outlined previously.
More skill is involved in aerial dispersant application because of the high speeds and low
altitudes demanded in such applications. Pilots must be trained and drilled in appli-
cation techniques. Maneuvers of fixed-wing aircraft flying at more than 150 knots at
15 m (50 ft) above the sea surface leave little room for error. A three-person crew
normally is used on a fixed-wing aircraft, and a two- or three-person crew is used with
helicopters. The pilot and copilot work together to maintain altitude and course. Di-
rections for commencing and halting spraying are supplied by the spotter aircraft and/or
the copilot to the crew member controlling the dispersant equipment. Because the en-
tire crew must operate as a team, they should be thoroughly familiar with the maneuvers.
Although the Air Force MASS system may be able to operate at altitudes over
30 m (100 ft), this system is still in the trial phase for dispersant application. Other
fixed-wing and rotary-wing equipment normally operate at 15 to 23 m (50 to 75 ft).
Higher-altitude operation may result in a fine spray over too wide an area to provide an
effective dispersant-to-oil ratio. This low-altitude operation is facilitated by the use of a
spotter aircraft to aid in alignment and to provide feedback on each run. The spotter is
in constant contact with the pilot or copilot to provide information on the position of the
aircraft in relation to the slick. The spotter can also provide the signal to commence
spraying. The spotter aircraft operates at a higher altitude and to the rear of the disper-
sant aircraft to enable the spotter to view the spray pattern and to direct subsequent runs
to adjust for wind drift and swath width.
Aircraft application of dispersant should be tailored to the slick conditions. When
treating the leading edge of a slick, the aircraft often will be flying perpendicular to the
wind. The flight path and alignment must be offset sufficiently to allow for wind drift
56
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and spreading of the swath that, depending on the equipment and altitude, may be in
excess of 30 m (100 ft). The swath width must be considered when aircraft are used to
treat windrows. Because a windrow may only have a width of 10 m (30 ft), a large air-
craft would waste considerable dispersant during spraying. In such a case, blanking of
some outer nozzles on the spray boom and/or smaller aircraft or marine vessels should
be considered if available.
57
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SECTION 7
DECISION PROCESS FOR DISPERSANT USE
Numerous oil spill response decision processes have been described in the liter-
ature (Fraser, 1989). The processes are usually illustrated in the form of a decision tree.
Appendix C provides example decision trees from the literature. Decision tree differ-
ences are due to their origin and purpose. Some decision trees are generated from dis-
persant use agreements and are a formal part of the agreement, whereas others detail
the steps involved in selecting a spill response mechanism. The published decision-
making steps differ in the level of detail and the extent of focus, e.g., coverage of oil
recovery, dispersant use, beach cleaning, and ecologic specifics.
A decision tree can become quite complex in an attempt to identify each aspect of
the decision process, including such details as spill size, sea state, weather conditions, and
environmental sensitivity. Such a decision tree is often quite informative, but somewhat
cumbersome to use, and it tends to submerge the basic considerations in a sea of detail.
A complex decision tree is desirable from a regulatory perspective when it functions as a
"pre-approval" for dispersant use. A detailed plan prepared prior to an event with input
from potentially concerned parties can specifically identify the steps that must be taken
prior to dispersant use. This agreement on the decision process prior to a spill can
relieve the OSC or the responsible party of the associated problems in addressing com-
peting concerns and trade-offs while trying to organize the response. The EPA com-
puterized decision process, which is presented in Appendix C, represents one of the more
detailed processes (Flaherty and Riley, 1987). A complex decision process has two major
problems: 1) The more detailed and rigid a decision process is, the more likely a
58
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situation will arise that does not correspond to the detailed decision steps, and 2) Such a
process is more difficult to prepare and maintain. Because the EPA computerized deci-
sion process has experienced both of these problems, the system is being reviewed (Cun-
ningham et al., 1989).
7.1 Simplified Decision Tree
Figure 7-1 provides a simplified version of a response decision procedure similar
to the International Maritime Organization/United Nations Environmental Program
(IMO/UNEP) guidelines (IMO, 1982). Its purpose is to illustrate the flow of response
decision making at the fundamental level. It is not meant to be a substitute for a
detailed decision process. The simplicity of the decision tree shown in Figure 7-1 has
both advantages and disadvantages. The decision steps shown are reduced to the basic
issues and provide an easy and flexible set of response actions. The process description
conforms to a general approach that is common to any marine spill event, but it does not
identify the specific inputs that are required to make the decision and proceed to the
next decision point. The reduction of the decision process to the fundamental elements
removes from the diagram some of the ancillary steps that go into the decision. The
process is focused on the basic question of which response or combination of responses
will provide the optimal environmental or economic protection. The absence of detail
requires the user to understand the significant number of considerations that are in-
volved with each step of the process. Some of these considerations are highlighted in the
Notes to The Decision Tree, but this is not a comprehensive list of items that covers all
contingencies. Development of detailed notes requires site-specific knowledge and com-
pliance with regulatory considerations that are applicable in the particular region.
The decision process shown in Figure 7-1 places more of the responsibility on the
OSC. The OSC, however, may have regulatory restraints that require the concurrence of
other parties in the various steps in the decision process. The regulatory regime that
controls dispersant use varies from region to region and can intersect the decision tree at
59
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Notes to the Decision Tree (Figure 7-1)
The use of this decision tree presupposes the availability of observational reports or other
factual data on which to make decisions. Observation and data gathering are considered fact
finding and information input and therefore are not considered as a decision step, but an
ongoing aspect of the spill event. No decision tree provides a substitute for experience and
judgment. The formal diagram is merely an aid to identify the key elements in the decision
process. The notes presented below supplement the decision tree diagram by identifying
some of the inputs and judgments necessary for a decision step.
100 In order to evaluate the threat, the following basic points need to be considered:
• Spill size/location - The spill must be large enough to have a coastal impact
if it moves toward shore, or be a threat to shallow-water offshore resources
(e.g., corals).
• Ecological sensitivity of coastal area - Wetlands, marshes, estuaries, and bird
breeding areas are extremely sensitive to oil and generally difficult to clean
by mechanical means without significant adverse impact. Review of
contingency planning maps will provide,this information.
• Economic concerns - Developed shorelines with a large tourist use can have
severe economic impacts on employment in the area if the beaches are
contaminated by oil fouling. Review of contingency planning maps will
provide this information.
« Oil movement - The potential path of the oil in the short term has to be
assessed immediately because the different responses may not all be
available in the short term. Preapproval plans for dispersant use often
discuss the coastal impact for a spill in a given area. As a quick estimate of
oil movement, forecasted wind conditions for a 24-hour period along with
current direction can be used to estimate the slick position using the vector
sum of 3 percent of the wind velocity plust 100 percent of the surface current
velocity to determine the location of the leading edge of a slick over the
course of the period.
105 In circumstances in which the threat is not immediate or the ecological and economic
impacts of landfall are small, an additional opportunity is available to marshal
response resources and produce more than one alternative. Spill modeling can
provide an estimation of the long-term movement of the spill to give the OSC further
information. Models available through NOAA or Regional Response Teams can
supply the probable path. The following possibilities can be assessed:
• Spill will not impact coastal areas before natural breakup.
• Spill will impact coastal region and will still be in a physical state or quantity
to cause significant adverse impact.
• • Spill will impact coastal region but is unlikely to cause significant adverse
impact.
• Long-term weather conditions will affect operations.
(continued)
61
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Figure 7-1. Notes to the Decision Tree (continued)
110 The feasibility of mounting a successful recovery operation will require a review of the
following factors at a minimum:
• Spill location in relation to recovery equipment and time to mobilize to
the site
Size of spill in relation to the amount of recovery equipment available
Storage barges or vessels available
Weather conditions over an extended time span
Sea state and currents
Trained personnel
115 Upon determination that recovery is a feasible response and has a significant
probability of successfully reducing environmental and ecological impacts, the OSC
must immediately mobilize recovery operations to maximize the potential for success.
In addition, the OSC should consider the supplementary use of dispersant.
120 The oil slick and physical conditions must be appropriate for dispersant use.
Determination of whether this is the case requires the following information to be
gathered and assessed:
Oil type
Age of oil
Size of spill
Thickness of spill
Sea state and winds
Spill location in relation to dispersant staging area
Type of dispersant available
The first two items need to be known to allow comparison with data on the
dispersibility of specific types of oil. The size of the spill permits judgment on
potential harm and potential for successful recovery. A small spill may not need
action, whereas a large spill near shore with a shore trajectory may not be treatable
prior to large-scale shoreline impacts. Sea state, weather conditions, and location of
the spill can all influence the feasibility of mounting a dispersant application effort.
130 Equipment must be available in a time frame that allows a response to have a
significant impact on the spill. The following information is useful in the assessment:
Time to mobilize equipment to spill location
Type of equipment available, i.e., boats or aircraft
Adequate dispersant stockpiles available to support operation
Staging area logistics support available
Equipment application rate sufficient to affect a spill prior to shoreline impact
Contracts and administrative details completed on equipment in time span
available
Trained personnel available
(continued)
62
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Figure 7-1. Notes to the Decision Tree (continued)
140 Under the current U.S. regulatory regime, dispersant use must either be preapproved
or approval must be obtained prior to its application on a spill. It is unlikely that
approval from the various parties involved can be obtained within a 24-hour period
and a significant application effort be mounted within a 24-hour period; therefore,
unless preapproval is in place, shoreline cleanup should be planned, in the event the
spill is unlikely to hit the coast for more than 24 hours, the OSC must evaluate the
factors from Block 120 and determine if the oil will still be amenable to chemical
dispersal in the time it may take to obtain approval. .
145 If dispersant use is not preapproved and it is more than 24 hours until the predicted
landfall, approval must be sought for dispersant use.
150 Preapproval plans will generally have quite specific requirements for dispersant use.
In some areas, additional approvals are needed from state authorities. The OSC must
ensure that the conditions for dispersant use have all been met prior to authorizing
the application of dispersants.
160 Dispersant application guidelines of the preapproval plans must be followed, and
other requirements set forth in the preapproval document must be implemented. The
specific requirements will vary between regions and with different locations within a
region.
170 Preparation for coastal cleanup for any spill that has a significant probability of
coastal impact is necessary under any response. Experience has shown that neither
chemical nor recovery methods have been highly successful in preventing shoreline
impacts; therefore, the OSC should make preparations for the coastal cleanup
activities during an off-shore response.
180 Spill monitoring to assess the response is necessary whether the response is
chemical, mechanical recovery, or no response. Upon finding a response is no
longer effective or conditions have changed, the OSC needs to determine if a new
course of action is prudent.
63
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different points. Thus, the apparent simplicity of the decision process presented in Fig-
ure 7-1 belies the complexity of the actual steps involved in decision making. An OSC
does not have the authority to proceed through the decision tree and implement disper-
sant use unilaterally except where human health and safety issues are directly involved.
The decision tree presented in Figure 7-1 focuses the process on the three basic
questions that need to be asked:
Could dispersant use reduce adverse impacts?
Is there a*suitable alternative to dispersant use?
Could a dispersant operation be implemented?
All other decisions are subordinate to these three and are based on increasingly subjec-
tive foundations. The actual use of dispersants will be controlled by site-specific environ-
mental considerations, regulatory controls, and the individuals involved in the process.
Monitoring Dispersant Effectiveness
As discussed previously, the OSC must make a continual assessment of the effec-
tiveness of the. response in a given spill situation after the decision has been made to
apply dispersants. This decision process can be based on visual observation or electronic
sensing methods. Visual observation has a major subjective component that can cause
significant variations in effectiveness claims between two observers (NRC, 1989). Fig-
ure 7-2 relates a general consensus oil appearance to thickness of the oil.
Electronic means such as the Side Looking Airborne Radar (SLAR), Ultraviolet/
Infrared Sensing or microwave sensing are the most common electronic sensing means
for monitoring an oil spill (Tennyson, 1992). Each of the electronic methods has its own
advantages and drawbacks and there is no consistent way to quantitatively determine
effectiveness (Descheves and Pullen, 1993; Choquet, et. al., 1993). Table 7-1 shows some
key features of various remote monitoring methods, including electronic sensing tech-
niques for monitoring oil slicks under various conditions. As noted in Section 3, fluoro-
metry may be used in conjunction with marine craft to sample the water under the slick.
However, actual analysis of the water does not offer the same versatility of movement
nor supply the same information as the remote sensing methods shown in Table 7-1.
64
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iooo H
Mousse
0.1 0.5 1 5 10 50 100
Approximate Layer Thickness (urn)
1000
Figure 7-2. Oil appearance as a function of thickness
(adapted from CONCAWE, 1988).
65
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The following spill observation guidelines should be used to determine the maxi-
mum effectiveness and application of dispersant use:
• Observations should be made from aircraft.
• Trained observers should be used to report on spill thickness and
dispersant effectiveness.
• The same observer should be used as much as practical.
• Video recording and photography should be employed to document visual
reports.
• Electronic data should be used to supplement visual observations whenever
possible (see Table 7-1).
• More than one type of electronic sensing should be used because of indi-
vidual method limitations.
The observer should vary his position and altitude in order to achieve the optimal van-
tage points for observing the effects of dispersant use on a slick. Light, clouds, sea state,
and angle of sun all affect the observation of oil on the sea. The observer should look at
differences in slick behavior between areas on which dispersant has been applied and
those that do not have dispersant application. Frequently, dispersion can be quickly seen
as a milky cloudiness in the water column where the dispersant has been applied. The
cloudiness varies with conditions and is generally yellow. The color can vary from whit-
ish to brownish. A brownish color generally indicates a more effective dispersion. If this
cloudiness does not appear, effectiveness was low. In clear water, a whitish cloud could
indicate just a mixture of dispersant and water.
The slick itself may change colors from black to brown within minutes of dis-
persant application, indicating partial effectiveness (McAuliffe, 1980; McAuliffe, 1981).
In addition, a slick may break into smaller patches within 30 minutes to an hour after
dispersant application. The observer should also keep in mind that dispersion is not
instantaneous. In the absence of wind or current changes, such patches are indicative of
67
-------
a dispersant that is moving oil droplets into the water column. Electronic sensing can be
used to support visual observations. The SLAR unit can indicate qualitatively whether
the slick has disappeared appreciably, but it cannot yield any quantitative information on
the thickness of the remaining slick. Microwave sensing under specific conditions can
determine both the disappearance of floating oil and a relative reduction in thickness.
A spill should be continually observed because even areas that initially show no
apparent effect from treatment may soon show dramatic changes in only a few hours in
comparison with untreated oil areas. Thus, decision making on the efficacy of a disper-
sant response should not be made immediately, but rather after a period of hours.
68
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SECTION 8
PRACTICAL CONSIDERATIONS FOR DISPERSANT USE
During an oil spill, a confluence of competing interests must be balanced. The
news media likely will be on the scene requesting statements on any action that is being
taken to respond to a spill event. Various interested parties such as representatives of
the vessel owner, the cargo owner, local fishing interests, businesses dependent on tour-
ism, local/state/federal government agencies, environmental organizations, equipment
vendors, and cleanup companies will appear on the scene and advocate their position to
both the OSC and the press. Often the various groups approach spill response from a
different base with different objectives. Decision making, management, and organization
of a spill response are made more difficult by maintaining open communication with the
various interest groups; but eventually the effort to maintain the interaction and develop
it organizationally can result in a much more effective response. Management and
organization of oil spill responses have been studied (Cohn et al., 1991; Noble, 1991),
but there are no tested paradigms that account for the rapid action and public input
required in a crisis situation.
Under the Federal government's spill response policy and regulatory environment,
the OSC has limited authority to take action. Although the OSC has authority to act
unilaterally in cases directly involving human health and safety issues, the various federal
agencies and the affected states must reach agreement (or at least lack of opposition) for
a response involving oil spill dispersants. The burden of achieving the consensus has not
been found to be unduly cumbersome or time consuming in two of the cases reported in
the literature (Cunningham et al., 1991); this is a small sample, however, and the actual
ability to obtain a consensus in a short period of time remains uncertain. Thus, it is
69
-------
important that the ground work be done prior to the need to use dispersants, This can
be achieved either through a preapproval process or through a more informal means
during a spill (Walker and Henne, 1991).
Misconceptions concerning the use of dispersants must be addressed. These range
from the idea that all dispersants are effective in any spill situation if used soon enough,
to the concern that the ecologic adverse impact of dispersant use is far worse than the
adverse impact caused by the spilled oil.
Unless the decision process is communicated and explained to the news media
and the various interest groups, significant pressure can arise to change the decision.
For example, the press and the public may consider dispersion of a spill by wind and
waves as acceptable or even desirable. In the event the decision is made to use disper-
sants, the similarity of dispersant action to natural action should be emphasized.
Another misconception that may be faced during a spill response is the concept
that all dispersants included on the NCP Product Schedule are equally effective. Data
on the relative effectiveness of dispersants are available, but these are based on labora-
tory analyses with a single crude oil and the results are not directly transferable to the
field. Further, many dispersants show an extremely low effectiveness (less than 10 per-
cent), even under ideal laboratory conditions. Dispersant performance is summarized in
Table B-9 of Appendix B. Based on information from the RCP, the OSC must evaluate
the dispersant(s) available and determine whether the dispersant is likely to produce the
desired results with the equipment available and the type of oil on the water.
Potential liability questions should be given consideration in addition to the ques-
tions related to dispersant effectiveness, environmental trade-offs, and the logistics of
responding to an oil spill. In the aftermath of an oil spill, there are generally a number
of legal actions. There may be civil penalties for adverse impacts, fines for regulatory
infractions, and civil suits between affected parties and the responsible party. The use or
nonuse of dispersants can complicate the picture, with the responsible party claiming that
a nonuse decision by the OSC greatly contributed to the resulting adverse impacts caused
by the spilled oil. Similarly, persons dependent on fisheries may claim harm as a result
70
-------
of the effects of the dispersed oil on the breeding of fish stocks. Either situation is dif-
ficult to prove or disprove but can result in a more burdensome legal aftermath. The
spill response will be questioned no matter what actions are implemented; therefore, it is
prudent to ensure that as much agreement as practical is reached prior to implemen-
tation of a response. Unanimity among the potentially affected parties is ideal, but is
unlikely to be achieved. A balance between agreement and an effectual response is
usually the best that can be achieved in dispersant use decisions.
With the multitude of problems that can arise in the U.S. legal environment and
the strong antipathy toward the use of dispersants that has developed among some inter-
ested parties, the OSC should reflect carefully on dispersant use and be ready for criti-
cism. Two considerations guide the decision-making process affecting an actual disper-
sant use situation:
There is a reasonable probability of measurable success (e.g., preventing oil
from reaching a beach or breeding area).
Consensus agreement has been reached between potentially affected
parties that dispersant application is worthy of being evaluated as a
response.
Measurable success, even if it is not complete, will vindicate the decision to use a
dispersant. Although it may not be required, a consensus agreement will help to defuse
critics who challenge a response that does not achieve success. Numerous other con-
siderations will come into play in a response involving the prospect or the actual use of
dispersants. It is beyond the scope of this document to attempt to identify all of the
possibilities. The final decision will be based on the experience, understanding, and
knowledge of the decision makers and their risk tolerance.
71
-------
APPENDIX A
DESCRIPTION OF VESSEL AND
AIRCRAFT APPLICATION EQUIPMENT
Vessel Application Equipment
Marine vessel application equipment is described on Pages A-2 through A-4.
Table A-l presents spraying capabilities of marine vessels ranging in size from small
fishing boats to much larger offshore supply vessels. Figure A-l illustrates spraying
equipment. Manufacturer specifications are included in Table A-2.
Aircraft Application Equipment
Aircraft spraying capability is presented in Table A-3. Figure A-2 illustrates an
airborne dispersant delivery system. Manufacturer specifications for a dispersant delivery
system for aircraft are included on pages A-7 through A-9.
72
-------
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73
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cr
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TABLE A-2. DISPERSANT SPRAYING EQUIPMENT
Spray Equipment
DSE-B
DSE-M
DSE-S
Type
Bay
Manual
Seagoing
. . Swath, ft
30
10
80
Weight, Ib
1100
30
2000
Source: PETRO Boom, 1993.
Spray equipment packages include blending skid, spraying arms, suction and dis-
charge hoses with quick-connect fittings, support columns, and other related components
necessary to operate the spraying unit.
75
-------
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77
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SPECIFICATIONS OF USAF MODULAR AERIAL SPRAY SYSTEM
Aircraft Compatibility: C-130 E/H modified by T.O. 1C- 130- 123
Configuration: Three modules - four 500-gal tanks, one 250-gal flush tank
(Two tanks are stainless steel, and two are aluminum).
Two Modules - Two 500-gal tanks, one 250-gal flush tank.
Power Source: Electric, 28- Volt d.c. from aircraft
Dry Weight: Three modules - 8981 Ib; Two modules - 6412 Ib
Applications: High volume (HV) - 100 to 1600 gallons per minute
Low volume (LV) - 60 to 600 gallons per minute
Ultra low volume (ULV) - 0 to 60 gallons per minute
Liquid Payload: 2200 gallons
Nozzle Sites: ULV - 50 sites
LV - 42 sites
HV - 92 sites on two fuselage booms
Aircraft Attachment: Floor of aircraft with dual rail system
Attachment Time: 30 minutes
78
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The MASS was developed as a roll-on roll-off spray system for the
C-130. The spray system consists of four 500-gallon tanks for chemical appli-
cations at varying rates of 0 to 1600 gallons per minute. The MASS consists
of three modular platforms with interconnecting plumbing and electric cir-
cuits.
The MASS may be arranged in two or three module configurations
depending on the type of mission requirements (ULV, LV, and HV). In a
three-module configuration, the MASS consists of four 500-gallon chemical
tanks, one 220-gallon flushing tank, and the operator's console. This is the
primary configuration for LV/HV missions.
In a two-module configuration, the MASS consists of two 500-gallon
stainless steel tanks, one 220-gallon flushing tank, and the operator's console.
This configuration is used primarily for ULV missions.
The MASS venting system is totally enclosed and connected to the
aircraft venting system in order to vent all fumes outside the aircraft.
The operator's console is located on Module 1. All loading, mixing,
spray control, tank-flushing, and boom purging procedures are accomplished
from this control panel. Fluid is transferred between tanks for mixing, recir-
culation, and spray operations by use of electropneumatic actuators that con-
trol the opening and closing of butterfly valves; diverter valves are controlled
by the operator at the panel. Three centrifugal pumps provide output pres-
sure for mixing, transferring, recirculation, and spraying for LV/HV missions.
Each of the pumps can be controlled individually by the operator, depending
upon the flow rate desired. Two gear-driven pumps are used to provide pres-
sure for flushing and the ULV systems. A 220-gallon aluminum tank is also
located on Module 1. This tank stores the flushing agent used to clean the
chemical tanks and associated systems (main sump, ULV sump, wing and
fuselage filtering systems, and their respective wing lines and booms). All
systems used with chemicals are flushed upon completion of each sortie. The
flushing system has its own pump and filtering system, and all controls are
operated from the console. After the flushing is completed, this material is
sprayed over the target area. Then the booms are purged by the wing and
fuselage air purge systems.
Each MASS platform is built from modified cargo pallets to enhance
the loading and off-loading of the spray system. These pallets lock into the C-
130's dual rail system to secure the system after loading. The operator's con-
sole, pumps, cradles for flushing, and chemical tanks are all secured to these
modified pallets. The pallets are modified further to incorporate a l-Vfc-in. lip
around the entire pallet in order to catch any spillage of chemical or flushing
79
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APPENDIX B
CONVERSION FACTORS AND
CALCULATION TABLES
The following tables and figures present useful conversions and equivalents, oil
slick thickness and slick volume relationships, dispersant doses per volume of oil, marine
vessel dispersant spray data, area coverage by marine vessels at various speeds, aerial
dispersant spray data, the Beaufort wind scale, the NCP Product Schedule effectiveness
ranking, and API-recommended cleanup methods. Most of these tables were obtained
from the Oil Spill Chemicals Applications Guide (Exxon Chemicals, 1985).
80
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TABLE B-l. CONVERSIONS AND EQUIVALENTS
Gallons (U.S.) x 0.8327
Gallons (imperial) x 1.20
Gallons (U.S.) x 3.785
1 Barrel of petroleum
Liters x 0.264
Cubic Meters x 264.2
Feet x 0.3048
1 mile (statute)
1 nautical mile
Feet/minute x 0.0183
Feet/minute x 0.0114
Feet/second x 0.682
Kilometers/hour x 0.5396
Kilometers/hour x 0.6214
Knots x 1.852
Knots x 1.150
Knots x 0.5144
Miles/hour x 1.609
Miles/hour x 0.8690
Gallons (U.S.)/acre x 9.353
Bbl/acre x 39.27
Cubic meters/square kilometer
x 16.29
Liters/hectare x 0.1
1 acre
1 square mile (640 acres)
1 hectare
Hectares x 2.471
Metric ton crude
Square Kilometers x 247.1
= Gallons (imperial)
= Gallons (U.S.)
= Liters
= 42 Gallons (U.S.)
= Gallons (U.S.)
= Gallons (U.S.)
= Meters
= 5,280 feet (1,609.3 meters)
= 6,076 feet (1,852 meters)
= Kilometers/hour
= Miles/hour
= Miles/hour
= Knots
-= Miles/hour
= Kilometers/hour
= Miles/hour
= Meters/second
= Kilometers/hour
= Knots
= Liters/hectare
= Cubic meters/square kilometer
= Bbl/square mile
= Cubic meters/square kilometer
= 43,560 square feet
=2.59 square kilometers
= 10,000 square meters (0.01 km2)
= Acres
= 7.3 barrels (approximately)
= Acres
Source: Exxon Chemicals, 1985
and CRC, 1988.
81
-------
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82
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TABLE B-3. VOLUME OF OIL IN BARRELS PER ACRE THAT CAN BE TREATED
AT VARIOUS DOSES OF DISPERSANT
Dispersant-to-
oil ratio
1:1
1:2
1:4
1:10
1:20
1:30
1:50
1:100
Oispersant (gal
5
' 0.12
0.24
0.47
1.20
2.40
3.50
5.90
11.90
7
0.17
0.33
0.65
1.70
3.30
5.00
8.40
16.60
10
0.24
0.47
0.94
2.40
4.70
7.20
11.90
23.80
(U.S.)/acre)
20
0.48
0.94
1.80
4.70
9.40
14.30
23.80
47.70
50
1.20
2.35
4.70
12.00
23.50
36,00
59.50
119.00
Source: Courtesy of Exxon Chemical Company (Exxon Chemicals, 1985)
83 '
-------
TABLE B-4. WORKBOAT SPRAY DATA*
Time (min) to cover
one acre for various
swath widths (ft)
Acres/hour for various
swath widths (ftj
Knots
1
2
3
4
5
6
7
8
9
10
mph
1.15
2.30
3.45
4.60
5.75
6.90
8.05
9.20"
10.35
11.50
km/h
1.85
3.71
5.56
8.52
9.26
11.12
12.97
14.82
16.68
1&.53
21
10
7
5
4
3
3
2
2
?
?0
.48
.77
.17
.sa
.31
.59
.07
.69
.39
15
30
14.32
7.18
4.78
3.59
2.87
2.39
2.05
1.79
1.59
1.43
10
5
3
2
2
1
1
1
1
1
40
.74
.39
.59
.69
.16
.80
.54
.35
.20
.08
20
.2.
5.
8.
11.
13.
16.
19.
22.
25.
17.
79
57
37
15
92
71
54
30
10
91
30
4.19
8.36
12.55
16.71
20.90
25.10
29.27
33.52
37.74
41.96
40
5.59
11.13
16.71
22.30
27.78
33.33
38.96
44.44
50.00
55.55
a Basis: 6076 feet per nautical mile.
b Minutes to cover one acre = travel d'stance per acre in feet * speed in
feet per second x 60 (see Table B-6 for travel distance time per acre for
various swath widths).
Source: Courtesy of Exxon Chemical Company (Exxon Chemicals, 1985)
84
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TABLE B-5. MAXIMUM AREA COVERED IN 16 HOURS AT VARIOUS BOAT
SPEEDS FOR SWATH WIDTHS OF 30 AND 50 FEET3
Knots
1
2
3
4
5
6
7
8
9
10
30-ft
Acres
67
134
201
267
334
402
468
536
604
671
Swath
mi2
0.10
0.21
0.31
0.42
0.52
0.63
0.73
0.84
0.94
1.05
width
km2
0.27
0.54
0.81
1.08
1.35
1.63
1.89
2.17
2.44
2.71
50-ft
Acres
112
223
335
445
557
670
780
893
1007
1118
Swath
mi2
0.17
0.35
0.52
0.69
0.87
1.05
1.22
1.39
1.57
1.75
width
km2
0.45
0.90
1.35
1.80
2.25
2.71
3.16
3.61
4.07
4.52
Gallons per acre x acres = gallons per 16 hours (Boat size may restrict
load, thereby requiring reloading at chemical stock point with attendant
loss of transit time).
Source: Courtesy of Exxon Chemical Company (Exxon Chemicals, 1985)
85
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TABLE B-6. TRAVEL DISTANCE REQUIRED FOR SPRAY BOAT OR AIRCRAFT TO
APPLY DISPERSANT TO ONE ACRE OR ONE HECTARE
Total
feet
20
25
30
40
50
60
70
80
100
120
150
200
225
250
300
swath width
meters
6.10
7.62
9.14
12.19
15.24
18.29
21.34
24.38
30.48
36.58
45.72
60.96.
68.58
76.20
91.44
Travel
ft/acre3
2178
1742
1452
1089
871.
726
622
545
436
363
290
218
194-
174
145
distance
m/hectare
1639
1312
1094
820
656
547
469
410
328
273
219
164
146
131
109
a Distance in ft/acre = 43,560 -^ swath width in feet.
Distance m/hectare = 10,000 -r- swath width in meters.
Source: Courtesy of Exxon Chemical Company (Exxon Chemicals, 1985)-
86
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TABLE B-8. BEAUFORT WIND SCALE
Beaufort
No.
0
1
Description
Calm
*
Light air
Specifications
L: on land
S: at sea far from land
L: Calm; smoke rises vertically.
S: Sea like a mirror.
L: Wind; direction shown by smoke-drift
Speed equivalent at
height of 10 m
m s"1 Knots
0-0.2 1
0.3-1.5 1-3
Light breeze
Gentle breeze
Moderate breeze
Fresh breeze
Strong breeze
Near gale
Gale
but not by wind vanes.
S: Ripples resembling scales are
formed, but without foam crests.
Wind felt on face; leaves rustle;
ordinary vanes moved by wind.
Small wavelets, still short but more
pronounced: crests have glassy
appearance.
L: Leaves and small twigs in constant.'
motion; wind extends small flag. •
S: Large wavelets; crests begin to •
break; foam of glass appearance;
scattered whitecaps.
L: Raises dust and loose paper; small
branches are moved.
S: Small waves, becoming longer; fairly
frequent whitecaps.
L: Small trees in leaf begin to sway;
crested wavelets form on inland .
waters.
S: Moderate waves, taking a more pro-
nounced long form; many whitecaps.
L: Large branches in motion; whistling
heard in utility wires; umbrellas
used with difficulty.
S: Large waves begin to form; the white
foam crests are more extensive
everywhere (probably some spray).
L: Whole trees in motion; inconvenience
felt when walking against the wind.
S: Sea heaps up and white foam from
breaking waves begins to be blown in
streaks along direction of the wind.
L: Breaks twigs off trees; generally
impedes progress.
S: Moderately high waves of greater
length; edges of crests begin to
break into spindrift; foam is blown
in well-marked streaks along wind.
1.6-3.3
3.4-5.4
5.5-7.9
8-10.7
10.8-13.8
13.9-17.1
4-6
7-10
11-16
17-21
22-27
28-33
17.2-20.7 34-40
(continued)
-------
TABLE B-8 (continued)
Speed equivalent at
height of 10 m
Beaufort
No.
9
Description
Strong gale
Specifications
L: on land
S: at sea far from land m s'1
L: Slight structural damage occurs. 20.8-24.4
S: High waves; dense streaks of foam
along wind; crests of waves begin to
roll over; ^pray may affect
visibility.
Knots
41-47
10
Storm
11
Violent Strom
12
Hurricane
L: Seldom experienced inland; trees 24.5-28.4 48-55
uprooted; considerable structural
damage.
S: Very high waves with long overhang-
ing crests; foam, in great patches,
is blown in dense white streaks
along wind; sea takes on a white
appearance; tumbling of sea becomes
heavy and shocklike; visibility
affected.
L: Very rarely experienced; accompanied 28.5-32.6 -56-63
by widespread damage.
S: Exceptionally high waves (small- and
medium-sized ships may sometimes be
lost to view behind waves); sea is
completely covered with long white
patches of foam lying along the di-
rection of the wind; all edges of
•wave crests are blown into froth;
visibility affected.
L: Very rarely experienced; accompanied >32.7 >64
by widespread damage.
S: The air is filled with foam and
' spray; sea completely white with
driving spray; visibility very
seriously affected.
From: UNDERSTANDING OUR ATMOSPHERIC ENVIRONMENT by Neiberger. Copyright(c)
and Company. Reprinted with permission (Neiberger, et. al., 1982)
1982 by W. H. Freeman
89
-------
TABLE B-9. NCR PRODUCT SCHEDULE RANKING OF DISPERSANT
EFFECTIVENESS (APRIL 1993)
Product name
Effectiveness, X (25 mL, 2 h)
1 Corexit 9550
2 Slickgone MS
3 ' SX-100
4 Corexit 9527
5 Anteco Oil Spill Dispersant
6 tnipol IP 90 '
7 Corexit 9554
8 Hare Clearr 505 •
9 Gold Crew; Dispersant
10 Uitca EXP 5250-109
11: Stik-A-Uay
12 Uitconul 4016
IS Keos. AB3000
14- HJC-Sr
15 H.C. *t Dispersant
16- Uitconut 407S
17 OSO/LT
18 toxlgon-2000.
W Enersy tit
20 lioSolve
21 UeHnid 33 T6
22 Ec.o «tlan'tot AT-7
2T Ecology ptus-
24 YCC BtueClean-
25 Micro-Blaze- Out
26 Cold Clean 500
27 Finasol OSR-7
28 Petro Tite (C-H-.E.
29 Inprove Colloidal
30 Enersperse 1100
31 Kaxchem Dispersant K
32 Grancontrol-O
33 Simple Green
34 nurture Oil Dispersant
35 Witco EXP 5150-97
36 Jansolv-60
37 Petrotech FEII
109.00:
75.00
74.60
60-.00
59^.00:
51.00
42..70
it .60
39.00
37.70
32..QO.
23.30?
T8":.6Q.
W.OO
17.90
16-90
16.00
16.00
14.70
T1.00:
8.70
7.90
6.70
5.00
3.90
3.50
3.10
3.00
t.70
1.00
0.70
0.65
0'.30
0.26
0.23
The effectiveness data given above is that reported to EPA by the product manufa tuners. The
percent effectiveness is determined using the Revised Standard Dispersant Effectiveness Test.
as required by Subpart J of the MCP reflations. The data reported in the product schedule
is strictly that reported to EPA by the aanufacturer; EPA does not change the reported value
in any uay.
90
-------
ti !a
Q =
I
I
•o
91
-------
APPENDIX C
EXAMPLE DECISION TREES
92
-------
1000
1800
3000
Opening Remarks
1100
Aerial Surveillance
1200
Is Oil Visible on the
Water Surface?
-Yes-,
4100
No
Continue Surveillance
1300
Is Oil a Safety Hazard to
Personnel?
-No-i
1400
Yes
Attempt to
Remove .Hazards
7500
Will Oil Impact
Sensitive Areas?
4200
No
-Yes-,
Allow for Natural
Removal and Continue
Surveillance
rzoo
Is the Slick Greater
Than 0.05 mm Thick?
4300
No
-Yes—
Allow for Natural
Removal and Continue
Surveillance
-No-
-No-
-No-
Is the Sea State
Greater Than 3?
1900 N,°
Is the Oil Slick Greater
Than 0.50 mm Thick?
2000 Yes
Deploy
Mechanical Equipment
2300
Is the Mechanical
Equipment Effective?
2400 Yes
Continue with
Mechanical Recovery
and Surveillance
2600
Is the Sea State
Greater Than 5?
i
2500 Yes
Allow for Natural
Removal and Continue
Surveillance
2700
Is the Oil
Dispersible?
2600 Yes
Is the Use of Dispersants
Acceptable?
3200 Yes
Evaluate Dispersant
Availability
3300
Are Dispersants
Effective?
Vao — .
Kin
Mo
-No —
-Yes —
Prepare for Impact on w
Sensitive Areas and
Continue Surveillance
3400
Are
Dispersants Safe?
NO
3500 Yes
Obtain Approval for
, Dispersant Use
3550
Were Approval and
Concurrence Obtained
for Dispersant Use?
-No-
3400 Yes
Is the Spill Area Greater
Than 60 Acres?
-No-i
3700 Yes
Apply Dispersant by
Aerial Spray from
Fixed-Wing Aircraft
3/?00
Apply Dispersant
by Boat or
Helicopter Spray
3900
Is Dispersant
Effective?
NO
4000 Yes
Continue with Dispersant
Application and Continue
Surveillance
4400
Consider
Other Alternatives,
Prepare for Impact on
Sensitive Areas
Figure C-1. U.S. Environmental Protection Agency oil spill response decision tree.
(Flaherty and Riiey, 1987; NRC, 1989)
93
-------
Oil spilled
obtain location;
predict and observe imovernent
Moving offsore ,
. 1 .:
Moving onshore or ;
to sensitive areas j
Continue
observations
Obtain sea state,
winds, type of oil
i
Suitable b
skimmers
respond?
waves
Y
i
Leave alone;
natural dispersion
1
Small i
<1, 000 bbl (160m3) ,
ooms and Spray b<
? Jims to olanes ava
Wind and
3 OK?
is N
Mechanical0
recovery
• i
oil be ch
•dispe
• Est'ir
spill vc
i
Dats and
lable? Can
emically
rsed?
o Yesb
Spray
dispersants0
r
Clean shore or
sensitive habitats6
nate ;
>lume \
\
]
Larae ',
>1 , 000 bbl (160m3) r
Sufficient
mechanical equipment
available?3
f
Use available
equipment to assist at
critical locations
Large aircraft spray
N
*
Oil dispersible?
•I ,.
o Yesb
f
Spray ';
dispersants \
Clean shore or
sensitive habitats6
a It is unlikely that sufficient mechanical equipment will be available to clean up a large spill.
b With the approval of the federal on-scene coordinator and the concurrence of the EPA and the state(s).
c Small spills normally should be completely controlled, particularly if both mechanical and chemical methods are used. Under
some conditions, however, some oil may need to be removed from the shore.
d Large spills, particularly 10,000 to 30,000 bbl per day, will be difficult to control. Only large aircraft spray systems are suitable
and some oil may still strand, however, oil that is kept off the shore will lessen the adverse effects,
e Appropriate methods should be used to clean shorelines and sensitive habitat. See, for example, API (1985).
Figure C-2. API dispersant use decision diagram.
(API, 1986; NRC, 1989)
Reprinted courtesy of the American Petroleum Institute
94
-------
Oil spilled
I
Yes-
Can oil be left to disperse
and degrade naturally?
-No—i
Monitor
Reassessment
if necessary
r—Yes-
Is physical control and
recovery feasible?
-No—i
Implement
£
Yes-
Reassessment
Step A
Are control/recovery
actions adequate?
or partially
Can oil be chemically
dispersed?
Continue actions
Yes
No
StepB
•tep
Will adverse impacts
associated with chemical
dispersion be less than
those resulting without
chemical dispersion?
Monitor until
change in status
and consider
resource protection
techniques
Yes
No
Implement
dispersion
Was action
adequate?
Yes
No
Monitor until
change in status
and consider
resource protection
techniques
Figure C-3. Environment Canada dispersant use decision tree.
(Environmental Protection Service, 1984; Fraser, 1989)
95
-------
Oil Spilled
1
r
Determine
Oil Characteristics
Yes
Can the
Oil Be Effectively
Removed?
Can Oil Type
and Condition Be
Dispersed?
Do
Weather Cond.,Sea
State, etc., Permit
ispersion?
Will Disp.
ause Less Damage
Overall than the Oil Slic
Will Cause?
1
Remove Oil
Yes-
c
Job Done
Monitor and Leave Alone
(Consider alternative
containment techniques,
shoreline protection
techniques, warning to
fishermen, etc.)
Implement
(
Job Done
J
Figure C-4. IMO/UNEP - Example of a typical oil spill response decision procedure.
(IMO, 1982; Fraser, 1989)
96
-------
Oil moving onshore or
into critical area(s)?
Yes
Is physical control and
recovery feasible?
Yes—
Is action required
or desired?
Yes
No
No
Implement
Are control/recovery
actions adequate?
Yes
No
or partially
Continue
actions
Monitor
movements
Can oil type and
condition be chemically
dispersed?
Yes
No
Is a dispersion operation
possible?
-No-
Treat
onshore
Yes
No
Will impacts associated
with chemical dispersion
be less than those
resulting without
chemical dispersion?
-No-
Will vulnerable resources
or habitats be adversely
impacted without
dispersant use?
Yes
Yes
Request approval for use
of dispersants using
attached procedure
Figure C-5. State of Alaska dispersant use decision matrix.
(RRT Working Group, 1986; Fraser, 1989)
97
-------
No treatment
Oil fate
Impact on resources
Spill conditions
Treatment alternatives
Preliminary decision
Relative importance
of resources
Tactical use of
other resources
Chemical dispersion
Oilfate
Impact on resources
Real-time
verification
Final decision
Figure C-6. SLR dispersant use decision-making method.
(Trudel and Ross, 1987; F rase r, 1989)
98
-------
APPENDIX D
BIBLIOGRAPHY
Abbott, F. S., and the Ad Hoc Committee. 1984. Guidelines on the Use and
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Al-Mazidi, S. M., and O. Samhan. 1987. Oil Spill Incidents and Dispersant Applications
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American Society for Testing and Materials. F931. 1986. Standard Guide for
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99
-------
BIBLIOGRAPHY (continued)
American Society for Testing and Materials. F971. 1986. Standard Guide for Ecological
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American Society for Testing and Materials. F972. .1986. Standard Guide for
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American Society for Testing and Materials. F1008. 1986. Standard Guide for
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American Society for Testing and Materials. F1009. 1986. Standard Guide for
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American Society for Testing and Materials. F1012. 1986. Standard Guide for
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The Arctic.
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Anderson, J. W. 1985. Toxicity of Dispersed and Undispersed Prudhoe Bay Crude Oil
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100
-------
BIBLIOGRAPHY (continued)
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Audunson, T., 0. Johansen, J. Koines, and S. E. Sorstrom 1987. Injection of Oil Spill
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Baca, B. J., and C. D. Getter. 1984. The Toxicity of Oil and Chemically Dispersed Oil
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Baker, J. M., J. H. Crothers, D. I. Little, J. H. Oldham, and C. M. Wilson. 1984.
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101
-------
BIBLIOGRAPHY (continued)
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-------
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