Oil Spill Response Preparedness in the Alaska Beaufort Sea
Nick W. Glover
Supreme Petroleum Council
Abu Dhabi, UAE

David Dickins, P. Eng.
DF Dickins Associates
La Jolla, CA USA

This paper is a reprint of material originally published by the same authors at the Symposium on Oil Spill Prevention andReadiness, Valdez, AK, October 1996 and at the 1999 International Oil Spill Conference, Seattle, WA

ABSTRACT
Following the wake of legislation and regulation promulgated in response to the 1989 Exxon
Valdez oil spill in pristine Prince William Sound, Alaska, the oil spill response industry worldwide
experienced exponential growth. To fulfill compliance obligations many oil exploration, production andtransportation companies purchased large stores of additional equipment without full consideration forthe suitability of the equipment for the types of oils to be encountered, the environment in which theequipment would operate, or the tactics that would be utilized in a response. These reactive measures
were not the result of poor judgement or mismanagement but rather the enforcement of regulatorycompliance without the benefit of sufficient relative data and experience. However, the outcome ofincreased regulatory pressure and the enhanced environmental awareness within the oil and gas industry
was a business environment that demanded change.
The evolution of oil spill response preparedness on the North Slope of Alaska represents amodel of change based on almost thirty years of practical experience with offshore and onshore drillingand production operations in all types of challenging sea and ice conditions. The current North Slope
response action plans are founded in this experience, intense field training, and the investigation andground truthing of related research and development projects.
1.0

INTRODUCTION

The first Alaska North Slope oil spill response organization was originally established in
Prudhoe Bay in 1979 under the name of ABSORB, an acronym for Alaskan Beaufort Sea Oilspill
Response Body, to support offshore exploration ventures in the Alaskan Beaufort Sea. In 1983
ABSORB as reorganized into Alaska Clean Seas (ACS) and was defined by the following
organizational objectives (Shafer, 1990):
1)
to develop spill response technology for the area,2)
to acquire an appropriate inventory of the best available
countermeasure equipment and materials,
3)
to maintain the equipment and materials in a high state ofreadiness, and

1 of 28

4)
to provide spill response training for personnel of member
companies and their contractors.
Hindsight would prove that the organization was active in some of the initial arctic oil spill
research and development projects but the primary purpose of the organization was to inventory andmaintain response equipment to support the offshore exploration program. In 1989, ACS provided nodirect spill response manpower to the offshore operators and provide no assistance whatsoever to theonshore exploration and production operations that were growing rapidly. It was not until 1990 that theNorth Slope oil spill cooperative, ACS, expanded it’s mission to include the provision of response
manpower and incident management for both offshore and onshore operations. The operational role of
ACS combined with the intense state and federal scrutiny of Alaska’s oil spill contingency plansprovided the catalyst for an evolution of response preparedness on the North Slope of Alaska..
The primary purpose of this paper is to summarize the arctic arctic effects on oil fate andbehavior and to describe response preparedness the spill response strategies, tactics and equipment thatare utilized effectively across the range of Arctic environmental conditions.
2.0

OIL FATE AND BEHAVIOR IN ICE COVERED WATERS

The comprehensive understanding of oil fate and behavior in arctic condition is of paramountimportance to developing effective oil spill response strategies and tactics. This knowledge was also
key to the creation of a practical, fit-for-purpose, inventory of oil spill response equipment on the North
Slope. The physical distribution and condition of spilled oil under, within, or on top of the ice plays amajor role in determining the most effective response strategies at any time of the year and the mostappropriate inventory to bring into combat operations.
Strategies and techniques for dealing with oil in ice have been studied intensively in the UnitedStates, Canada and Norway for many years. The most significant scientific knowledge was gained
through a number of Canadian field studies aimed at gaining approvals for offshore Beaufort Sea
exploration beginning in 1976. These field studies and others in Alaska and most recently in Norway
have looked at the behavior of fresh and emulsified crude oil, with and without gas, in a variety of ice
conditions including landfast and broken pack ice (e.g., McMinn, 1972; Norcor, 1975; Buist andDickins, 1981; Nelson and Allen, 1982; S. L. Ross, 1987; Vefsnmo and Johannessen, 1994).
Dickins and Fleet (1992) contains a comprehensive summary of all known references on the subject ofoil-in-ice fate and behavior, including analytical studies, tank and basin tests, spills of opportunity, andexperimental spills at sea.
The fate and behavior of oil in ice covered waters is governed by a number of important
processes, several of which are illustrated in Figure 2-1 (after Bobra and Fingas, 1986) and discussed
below.
• Spreading. In Arctic waters during early and late summer, oil spills tend to spread
less and remain slightly thicker than in temperate waters (such as the Gulf of Mexico)
partly because oil is more viscous in cooler waters, but mostly due to the presence of
broken ice and brash ice, respectively. In high concentrations (greater than 5/10), oilspreading tends to be limited to the spaces between the floes. There are a number ofmodels that predict the spreading of oil as a function of ice concentration. These are

2 of 28

•

•

•

•

•

based largely on the results of a field trial off the east coast of Canada (Ross andDickins, 1987). In general, oil spilled under stable landfast ice will not spreadbeyond hundreds of feet from the spill source, based on currents and projectedunder-ice storage capacity (see ice storage below). The maximum expected underice currents in the Beaufort Sea nearshore are extremely low. In a March 1996
study inside the barrier islands, no currents were detected under the ice over a periodof five days (Intec, 1996a). In the extreme case, any tidal currents present are
expected to be much lower than the minimum threshold of 0.5 feet per second(ft/sec) necessary to initiate and maintain any transport of oil under solid ice (Cox and
Schultz, 1980).
Evaporation of volatile components occurs with any oil resting on the water or ice
surface. Evaporation rates of oil slicks are influenced by wind speed, slick thickness
and environmental temperatures. Laboratory testing of oils from the North Slope
indicates that the initial evaporative loss, by volume, within the first 48 hours can be
expected to range between 16 and 30% depending on the oil tested. (Buist, 1994)
Dispersion is a process by which small oil droplets are driven under the surface bywaves and turbulence and remain suspended in the water column. Dispersion rates
depend largely on sea state, oil viscosity, interfacial tensions, and the tendency of theoil to emulsify. The formation of stable water in oil emulsion generally stops thenatural dispersion of a slick.
Entrainment and rapid immobilization of oil spilled beneath growing ice
essentially stops all weathering processes (Buist and Dickins, 1981; Norcor, 1975;
Allen and Nelson, 1981). The implications of this are significant. When responsecrews pump or burn oil brought to the surface from a trapped layer under or within
the ice, they will be dealing with almost fresh crude, even months after the spill
occurred.
Ice Storage. Natural variations in first-year ice thickness provide huge natural“reservoirs” to effectively contain oil spilled underneath the ice within a small area.
Under-ice storage capacities have been estimated to be as high as one million barrels
per square mile from surveys in late winter near West Dock (Kovacs et al., 1981).
The implication here is that any mid-winter spill that may for whatever reason occur
beneath the ice would be naturally contained within a relatively small area whencompared to an identical volume spill on open water
Vertical migration of oil through the melting ice starts in the spring (Norcor, 1975;
Buist and Dickins, 1981). Beginning as early as the last week in May and continuing
through breakup, oil will naturally rise to the surface from wherever it is trapped
within or beneath the ice. The timing of this process will dictate appropriate response
strategies to deal with any accidental spill that may have become trapped within theice during the previous winter months.

3 of 28

Figure 2-1
Illustration of Oil and Ice Processes
3.0

SEASONAL EFFECTS ON OIL BEHAVIOR

In addition to understanding the fate and behavior process, arctic oil spill responders must also
have a comprehensive understanding of how oil will behave during any of the seasonal ice and snow
conditions present in their area of operations. The following section describes the anticipated oil
behavior impacts attributed to the Alaskan North Slope ice seasons.
3.1

Winter, Oil Spills Beneath Solid Floating Ice

A solid ice surface is present in the nearshore area of the Alaskan North Slope for over 7
continouous months every year. The behavior of oil spilled under solid ice covers has been the subjectof numerous field, laboratory and analytical studies. The two largest field experiments took place in the
Canadian Beaufort Sea in 1974-75 and 1980 (Norcor 1975; Dickins and Buist, 1981). The Norcor
project involved eight spills of two different crude oils totaling 330 barrels under ice ranging in thickness
from 17 to 70 inches. An experiment sponsored by Dome Petroleum and supported by ABSORB(Dickins and Buist, 1981) simulated a subsea blowout by injecting compressed air and Prudhoe Bay
crude oil under landfast ice. One of the Dome releases was predominantly oil alone and can be used inconjunction with the Norcor results to accurately describe the interaction of oil with the ice during winterand spring conditions right up to breakup. It is convenient to separate the discussion seasonally into:• Winter ice contamination and oil encapsulation (October to April), and• Spring oil migration and surface appearance (April to July).

4 of 28

3.1.1Winter Ice Contamination And Oil Incorporation

Oil released into the water column under a floating solid ice cover will rise and gather in poolsor lenses at the bottom of the ice sheet. Based on Stokes Law, the terminal rise velocity of a 0.4-inch
diameter oil particle, with a density of 0.850 g/ml, is about 0.75 ft/sec in seawater. Typical under-ice
currents within the North Slope barrier islands are unlikely to exceed 0.5 ft/sec. As a result, almost allof the oil will contact the ice under surface within a few feet of the vertical center of a release.
Winter under-ice currents, in the coastal area of the Beaufort Sea, will not spread spilled oil
beyond the initial point of contact with the ice under surface. Several studies have provide empirical
data to indicate that the roughness values typical of undeformed first-year sea ice will trap oil in place.
The threshold current speed needed to initiate and sustain movement of an oil lens or pool along the ice
under surface is approximately 0.7 ft/sec, well above the highest currents measured in the near coastal
areas associated with Alaskan North Slope oil exploration and development (Cammaert, 1980;
Norcor 1975; Rosenegger, 1975).
Two physical factors that act to naturally limit the area contaminated by oil under ice are naturaldepressions related to variability in snow depth, and rapid incorporation of the oil by new ice growtharound and beneath the oil layer. Ice naturally develops an undulating bottom surface in response tosnow drift patterns on the surface. Researchers have investigated the holding capacity of ice covers by
mapping the under-ice topography and calculating the potential for oil containment (e.g., Kovacs et al.,1981). Results indicate that typical under-ice containment capacities for first-year landfast ice
representative of the Prudhoe Bay area within the barrier islands, range from 0.012 barrels per squarefoot (bbls/ft2) for 25-inch thick ice in December to 0.026 bbls/ft 2 for 60-inch thick ice in April(equivalent to about one million barrels per square mile). As the natural containment increases with ice
thickness, the area needed to contain a given spill volume decreases steadily throughout the winter, as
shown in Figure 3-1.

Figure 3-1
Predicted Radii of Spills of a Given Volume Spilled Under Landfast Ice

5 of 28

(Dickins, 1985)
Based on these containment capacities, a 10,000 barrel spill from the Northstar sub-sea
pipeline source beneath the ice surface in April would be naturally contained within a diameter ofapproximately 320 feet. Natural variations in ice thickness comprise the most important physicalcharacteristic limiting the spreading of oil from a sub-surface release. In the case of a small leak, theformation of a lip of new ice at the outer perimeter of the spilled oil will also act to further limit spreadingin the case of unusually smooth ice.
In a batch release, new ice will completely encapsulate the oil layer within 18 to 72 hours,
depending on the time of year from December to late April (Dickins and Buist, 1981). Oil spilled under
the ice after May 1 may not become encapsulated due to the seasonal warming of the ice layer.
With a chronic leak that occurs over a long period of time, new ice is prevented fromimmediately growing directly as a hard layer beneath the oil pocket due to the continuing arrival of freshoil. Ice crystals present in the water at the oil/ice interface will probably be incorporated to provide aslush/oil mixture that gradually thickens the longer the spill source remains undetected. At the same time,
new ice growing around the perimeter of the contaminated area will progressively contain the oil. The
end result for most of the winter will be a cylinder of liquid oil and slush deepening as the surrounding ice
grows. In the case of a chronic leak spanning the April to June period, the contaminated area will
increase as the ice growth rate slows down. The final trapped oil geometry in this situation would be
similar to chronic leaks in mid-winter, except that the oil pocket will assume the shape of an inverted
truncated cone, with the largest diameter at the deepest depth and the angle of the cone increasing as
new ice growth diminishes. Once the spill source is detected and the flow stopped, new ice will begin
to form beneath the oil within several days (December to April).
3.1.2

Spring Oil Migration And Surface Appearance

Oil that has released under on within the ice during the early to mid-winter season will become
encapsulated and remain trapped until late-winter, at which time a process of vertical migration will
begin due to the gradual warming of the ice sheet.
The rate of vertical migration depends on the degree of brine drainage within the ice (a functionof internal temperature), oil pool thickness, and oil viscosity. During the period from November to
February when the sheet is cooling and growing rapidly, there are very few passages for the oil topenetrate. Vertical migration of the oil in this period is limited to several inches of initial penetration
through the porous skeletal layer of individual ice crystals at the ice/water interface.
The internal ice temperature reaches it’s minimum typically in late February. As ice
temperatures gradually increase in April and May the brine trapped between the columnar ice crystals
will drain out of the ice, leaving vertical channels for the oil to eventually rise to the surface. The firstevidence of natural oil appearance on the surface can be observed in mid to late May or may bedelayed until the first week in June, depending on air temperatures. Oil released under six feet of ice in
one experiment on May 21 reached the ice surface within one hour (Norcor, 1975).
The rate of oil migration increases rapidly once daily air temperatures remain consistently above
freezing. During the same experiment mentioned above, up to 50 percent of the oil originally trapped

6 of 28

within the ice became exposed on the ice surface between June 10 and June 20. Oil slick thickness inthe melt pools on the surface increased from 0.04 inches to over 0.4 inches during a one-week period.
Natural melt of the ice from the surface down acts as a competing process to expose
encapsulated oil When this melt reaches the level where the ice was growing at the time of the spill, theoil is exposed. In most situations of a concentrated thick oil layer encapsulated in the ice, natural
migration will bring most of the oil to the surface before the surface melts down to meet it.
When oil reaches the ice surface, it lies in melt pools or remains in patches on the melting ice
surface after the surface waters have drained. The heat absorbed by the dark oil on the surface further
serves to enhance surface melting into pools where the oil is present. Winds act to herd the oil into
thicker layers against the edges of individual pools. This concentrated presence of oil can be effectively
recovered or burned in-situ if seasonal conditions pose a safety risk to responders attempting toconduct mechanical recovery operations (refer to In-Situ Burning discussion in Section 4.3).
Any oil remaining in or on the ice at final breakup and disintegration of the ice cover will be
released slowly into the water as thin slicks and sheens.
3.2

Winter, Spreading Oil on Top of Ice and Snow

The resulting area of contamination from a release of oil on top of ice will be influenced by anumber of site specific factors, such as, wind speed, surface roughness and the amount of snow cover in
the area of the release. Other factors associated with an individual release may have an even greater
potential to influence the total area of contamination. For instance, a release from a high pressure
pipeline versus a tank rupture has a greater potential to spread the contamination to a larger area.
Likewise, if a breach of a high pressure pipeline directed the escaping oil toward the ground the overall
impacted area would be less than if the breach directed the escaping oil high into the air where windconditions could potentially spread the contamination for miles.
A number of process equations are available to predict the spreading behavior of oil in snow
(Belore and Buist, 1988). Key behavioral factors associated with oil spilled on snow can besummarized as follows (after Wotherspoon, 1992):• Oil evaporation rates in snow are substantially reduced compared with oil slicks on
open water;• Oil mixed with snow does not readily form emulsions; and• Once ignited, there are no appreciable differences between burning oil in snow or oil
in water.
Demonstrations conducted during the 2000 International Oil & Ice Conference
effectively illustrated how oil absorbed into the surface snow layer or lying on the surface ice
could be effectively recovered through mechanical means or even stockpiled and burned. Oilcontaminated snow can be piled into a volcano like shape with a strong indentation in the denterof the pile. Utilizing ignitors to create an intense heate source in the center of the contaminatedsnow pile will cause impregnated oil to be released toware the water pool in the center where it
is consumed and serves to sustain the burn until oil quantities are no longer sufficient to support
combustion.

7 of 28

3.3

Late Spring/Early Fall, Oil Spills in Broken Ice conditions

Oil spilled beneath broken ice would rise to the surface and either collect in the interstices or
openings between individual floes or be trapped underneath the floes themselves. Oil spilled on thesurface would likewise adhere to the ice surface or become wind herded against the ice edges andwould eventually be frozen in place on the surface of the ice unless disturbed by extreme windconditions causing the ice to break up and become rafted. During the primary period of broken ice inthe spring, oil released beneath the floes will naturally migrate through the rotting ice and appear on theice surface within a matter of hours (refer to the above discussion of the spring oil migration process).
Oil released into spring broken ice conditions would be contained in the openings between floes andcoat the surrounding ice edges and float in surface pools. As spring melt continues the area ofcontamination would increase. For the case of oil trapped within or under newly forming pancakes or
sheet ice in the fall, the likely fate will be rapid entrapment, with new ice quickly growing beneath the oil
as already discussed. The fate of oil trapped between floes will depend largely on the ice concentration,
air temperatures and local wind effects.
During freezeup, the oil will most likely be entrained in the solidifying grease ice and slush
present on the water surface prior to forming sheet ice. Storm winds at this time often break up anddisperse the newly forming ice, leaving the oil to spread temporarily in an open water condition until
incorporated in the next freezing cycle (within hours or days depending on the air and watertemperatures at the time). Ice drift rates at this time of year are highly variable, but a daily average offive nautical miles per day can be expected in October, decreasing as the ice thickens and stabilizes in alandfast condition through November.
At breakup, ice concentrations are highly variable from hour to hour and over short distances.
In high ice concentrations (greater than 5/10), the oil is effectively prevented from spreading and iscontained by the ice. As the ice cover loosens, more oil is able to escape into larger openisngs as thefloes move apart. Eventually, as the ice concentration decreases to less than 3/10, the oil on the water
surface behaves essentially as an open water spill, with localized oil patches being temporarily trappedby wind against individual floes. Any oil present on the surface of individual floes will move with the ice
as it responds to winds and nearshore currents.

4.0

PLANNING AND RESPONSE STRATEGIES

Response planning and strategies for oil spills in ice have been developed over twenty years ofactual experience with North Slope drilling and production operations. The techniques discussed in thisdocument have been demonstrated and applied in real spill situations. The following sections describe:• methods and applicability of surveilling and monitoring oil spills invarious
ice and open water conditions,• the influence of various ice conditions on the logistics of mounting aneffective response operation and determining the best cleanup strategies,• the effective use of in-situ burning as a response option in various oil and ice
conditions, and

8 of 28•
4.1

a summary of seasonal response strategies based on ice conditions.

SURVEILLANCE AND MONITORING

Surveillance and monitoring involves the techniques and systems available to detect, map, andtrack oil spilled into the Beaufort Sea from any source connected with the current North Slope
production facilities and pipelines.
4.1.1

Surveillance and Monitoring Systems

One of the initial actions that must be implemented for any oil spill is to determine the initialextent of contamination and in the case of spills on water or in moving ice to continually locate and track
oil as it migrates. Numerous systems and specific equipment have been developed to detect and trackoil spills on open water and ice through experience in southern areas, arctic field trials, and laboratory
research (summarized in Wotherspoon, 1992). Common techniques and equipment available to ACS
include a combination of the following:• Satellite tracking buoys are designed to follow the movement of the oil slick in
response to winds, surface currents, and ice movements. Using the new Global
Positioning System (GPS), these "Slicktrackers" are capable of delivering real-time
positions to computers in the command center with accuracy of better than 150 ft.
(Costanzo, 1994). ACS maintains an inventory both the Trimble Sliktrak buoys andMetocean satellite ice beacons in their existing inventory. The Metocean beacons
are capable of being deployed under virtually all ice conditions and providing alocation signal for months after their initial release.
• Radio tracking buoys are similar in design and use to the satellite tracking systems
but utilize a small radio transmitter built into the buoys to emit burst signals. Thesesignals are then tracked by the receiving equipment which can be placed onboard
vessels of opportunity, fixed wing or rotary wing aircraft. An inventory of Orion
radio tracking buoys are maintained by ACS on the North Slope.
• Airborne reconnaissance is conducted with visual observers, still and video
cameras, infrared and ultraviolet sensors, laser fluorosensors, and radar. Trained
visual observers are used, together with more sophisticated remote-sensing
equipment to enhance the information (helping to differentiate between natural "slicklike" targets such as silt on the ice, cloud shadows on water, and wind patches, andto map both the thick and thin parts of the slick).
Optical methods (still and video cameras) are useful for recording overall spill
location and slick boundaries in reasonable light conditions. They do not provide agood indication of slick thickness and can cause confusion in low light conditions.
Infrared (IR) systems are highly effective in documenting offshore slicks
through temperature differences between the oil and water. UV systems are more
expensive and used primarily in conjunction with IR to differentiate between thickand thin sections of the slick.

9 of 28

ACS has immediate access to a variety of helicopters and fixed wing aircraft
to map any slicks observed on the water in the project area. The ARCO Twin Otter,located on the North Slope, is equipped with a Forward Looking InfraRed (FLIR)
thermal imaging system. The system is a gyro-stabilized, microprocessor-based
system that provides state-of-the-art digital image processing. An onboard computer
system is capable of processing the digital information and combining these images
with environmental data and GPS information simultaneously collected by othershipboard instruments. The images shown below, in Figure 4-1, depict two (2)crude oil storage tanks on the North Slope. The image on the left shows two tanksof which the tank on the right is full and thus give a brighter image. The image on theright is a close up of the other tank in the left hand image and clearly indicates thetank is approximately 25% full. In addition, the U.S. Coast Guard operates
specialized UV/IR and Side Looking Airborne Radar-equipped aircraft forsurveillance of large spills over wide ocean areas (known as the "Aireye").

Figure 4-1
Infrared Photography of Crude Oil Storage Tanks(Source: ARCO Aviation, 1995)• Handheld GPS units are used extensively on the North Slope to document
locations and extent of spill sites. ACS maintains an inventory of Garmin 45
handheld GPS units at each of the operating oilfields on the North Slope.
Responders are trained in the use of these units and as such they are used frequently
to support daily work activities. During previous spill events GPS data has beenused in conjunction with survey crews to delineate areas of contamination under
extreme winter conditions.
• Portable Current Meters are available and have been used to determine bothcurrent speed and direction under both summer and winter conditions. Information
gathered by current meters is extremely important to produce accurate computermodeling.

10 of 28• Underwater Lights have been researched, field tested and found to be very
effective in locating oil under ice. The systems utilized by the NSSRT consist of ahigh intensity quartz halogen light fixture attached to a long handle. The assembly is
lowered through a hole augered through the ice and illuminated once it is placed in
the water. Once the snow cover is removed the lighting clearly indicated areas of oil
accumulation.
4.1.2

Surveillance During Arctic Ice Season

When drifting ice concentrations are less than 5/10 the process of detection and mapping isbasically the same as open water. As ice concentrations increase to greater than 6/10, visual detectionof oil in small openings and leads becomes more difficult. These problems are magnified in October andNovember by conditions of frazil ice, thin moving ice and decreasing daylight. There are a number ofpossible approaches to tracking and mapping oil under these conditions. Experimental airborne systems
such as the laser fluorosensor and IR sensors have shown potential for detecting oil on or amongst ice
floes. Satellite beacons are available for airborne deployment and do not require aircraft to land on theice. As of April 1996, daily satellite coverage is now available for offshore ice conditions independentof daylight, cloud cover, or fog (Canadian Radarsat). The satellite lacks the resolution to detect small
oil slicks directly, but it can provide a clear picture of the ice conditions in the vicinity of the oil whenused in combination with tracking buoys.
As the ice sheet stabilizes and thickens a number of resources may be utilized to approach an
offshore spill site. Small one and two man All Terrain Vehicles (ATV’s) (i.e., snowmachines, 4wheelers, ARGO tracked vehicles) are available across the North Slope to support reconnaissance andsurvey teams. In December, as thicker ice forms, it is possible to land by helicopter and confirm any
sightings of oil. Once the ice is stabilized and landfast out to the barrier islands, any oil spilled will either
lie trapped within, under, or, in the case of a coastal blowout incident, lie mixed with snow on top of theice surrounding the island.
The primary techniques for detecting oil on top of the ice are visual observation or opticalcameras. During the winter, oil on the ice surface may be covered by drifting snow, and it may become
necessary to map any suspected contaminated area with radial trenches or a grid pattern shovelingdown to the bare ice. This process will clearly reveal the extent of snow contamination through visualinspection of the trench walls.
In May and early June, optical and visual methods work well in mapping oil on the surface.
Oiled snow will melt faster than the surrounding snow due to the increased heat absorption in late May.
As the melt progresses, sediment on the ice (particularly in the river overflood area) and the light anddark patterns characteristic of a deteriorated ice surface appearance can easily be confused withweathered oil. Oiled ice tends to melt slightly faster than the surrounding ice, and these differences canstill provide visual clues to the location and extent of oiling (Norcor, 1975; Dickins and Buist, 1981).
Oil remaining trapped beneath or within the ice at the end of the growth cycle becomes mobile
as the ice sheet warms in April. For a known area of trapped oil, the rate of vertical migration of the oil
within the ice can be monitored by regular core samples (starting weekly in April and progressing todaily by mid-May). At the same time, the degree of weathering of the surfaced oil can be monitored bycollecting samples for lab analysis.

11 of 28

4.2

Influence of Ice Conditions on Cleanup Strategies

Ice in one form or another can be encountered in the vicinity of the North Slope oilfields at any
time of the year. Of all the factors affecting the choice of response actions to deal with a marine spill
originating from coastal facilities or pipeline river crossings, ice and weather conditions largely determine
workable strategies and control the eventual outcome. Examples of important ice conditions include
thickness, stability, bearing capacity and concentration.
Ice thickness dictates the available site access and load-bearing capacity for staging
equipment and surface travel to and from the spill site. Depending on location and time of year, sea ice
will support heavy equipment, such as trenchers, end-dumps, backhoes, ditch witches, and bladders for
temporary storage and/or transport of liquid oil pumped from within the ice. Figure 4-2 illustrates thecorrelation between ice thickness and loading capacity.
During a typical winter, ice roads will be available or can be constructed to support oil spillrecovery operations from late December to late April. By early May the ice surface is normally too
deteriorated to maintain the ice road in a usable state. The ice sheet itself usually retains enough stability
and thickness until early June to support heavy loads at the spill site itself; the problem during thisperiod becomes one of access to and from shore. On-ice operations from early June to breakup will
depend on day to day conditions and may require continuous helicopter or Air Cushion Vehicle (ACV)support to ensure the safety of work crews.

12 of 28

MINIMUM THICKNESS TO
SUPPOR T LOADS ON SEA ICE

Figure 4-2
Load Bearing Capacities of Sea Ice (Source: ACS Techincal Manual)
Helicopters, ACV’s and airboats can be used during the shoulder seasons of freezeup or
breakup to transport limited payloads of personnel and equipment to an offshore spill site. ACS has acontract in place to utilize a high speed, turbine powered ACV currently located at West Dock inPrudhoe Bay. The unit has a cargo payload of 30 tons and can be operational within four (4) hours ofcrew arrival in Prudhoe Bay.
Bottom founded ice refers to the condition where a portion of the fast ice becomes thickenough to rest on the bottom in shallow water. This condition is commonly encountered between the
shore and the barrier islands after mid-February. Winds have a great effect on water levels throughout
the study area, even in the winter; westerly storms can create a one to two foot increase in water levels
and lift the ice sheet off the bottom temporarily during mid-winter (Coastal Frontiers in Intec, 1996a).
After March, much of the ice in Simpson Lagoon rests firmly on the seabed with an attached layer offrozen sediment at the ice/bottom interface. Figure 4-3 shows a typical transitional cross-section for
arctic sea ice. It is important to note that in the nearshore area of Prudhoe Bay the bottom founded
condition could extend for 2 - 5 miles offshore to contact the barrier islands. The implications of this"bottom-founded" condition are that crews may have to trench completely through the ice and recover
oiled sediments encapsulated within or lying under the ice. The capability to perform this operation wasdemonstrated by BPXA during a trenching test in April 1996.

13 of 28

Figure 4-3
Typical Arctic Sea Ice Cross Section
Ice Stability is closely linked to thickness and refers to the potential for large ice movements in
response to storm winds. Periods of most concern for oil spill response are freezeup from Octoberthrough December, and breakup in June and July. During October and November, the ice is less than
two feet thick and easily broken up by sustained storm winds predominantly from the east-northeast(Vaudrey - internal project memorandum, May 1996) . By late December, once the first-year ice hasreached approximately three feet in thickness, ice becomes relatively stable and remains so until lateJune. There are exceptions, such as February 1989 when 90- to 100-knot southwesterly winds drove
most of the landfast ice from inside the barrier islands 20 to 30 nautical miles offshore (Vaudrey , 1996).
Once the ice has deteriorated during spring melt, another short period of instability occurs
during the transition from a continuous ice cover to predominantly open water. The ice normally melts
in-situ in the shallow waters near the coastline by mid- to late June. Further offshore the fast ice
becomes unstable and susceptible to wind-induced breakup in early July (Vaudrey, 1996).
During these "unstable" months, response operations may encounter the possibility of oil trappedin, or on top of the ice, moving 10 miles or more in a 24-hour period of sustained storm winds. The oil
location can be tracked accurately on an almost real-time basis by deploying Global Positioning System(GPS) beacons reporting to satellites. During dynamic broken ice conditions following freezeup andpreceding breakup, helicopter-supported burning operations with the Heli will likely be the mosteffective response strategy.
Ice concentration refers to the area of surface water covered by ice, and is described by an
ice-to-water ratio expressed in tenths. Ice concentrations dictate not only the extent to whichconventional open water oil recovery systems can be used in deeper water, but also the extent to which
the natural containment offered by the ice will limit spreading and allow direct in-situ burning (S. L. Ross
and D. F. Dickins, 1987). The period when the choice of cleanup strategy will be most affected bydrifting ice stretches from approximately July 4 (±2 weeks), the average dates when breakup occurs in
the vicinity of the barrier islands, to July 22 (±7 days), the average dates when ice concentrations fall toless than or equal to 3/10. The value of 3/10 is significant in that it represents a generally accepted

14 of 28

upper limit for deploying conventional booms and skimmers without unacceptable interruption fromdrifting ice (S. L. Ross, 1983; Shell et al., 1983).
The period from first breakup in early July to approximately mid-July provides a two-weekwindow when the ice cover is likely to remain in concentrations of 7/10 to 9/10, high enough to support
natural burning with aerial ignition from helicopters. Ice concentrations between 3/10 and 6/10
represent the greatest problem for oil spill cleanup. Conventional booms may be collapsed, overrun, or
damaged by drifting ice. At the same time there is insufficient ice to naturally contain the oil into
sufficiently thick patches to burn in-situ without firebooms. Fortunately this troublesome range ofconcentrations is short lived; concentrations normally fall from 5/10 to 3/10 in less than one weekduring breakup (Vaudrey, 1996).
The period of ice overflood introduces a special set of circumstances in modifying the oil
behavior and complicating cleanup efforts for a period of 10 days to two weeks. From late May to
mid-June, a large proportion of coastal waters within the ACS area of operation is incorporated within
the spring overflood from the Sagavanirktok, Putuligayuk, and Kuparuk Rivers (Vaudrey, 1996).
Figure 4-4 represents the areas of spring overflood. Not only is surface access difficult at this time, but
any oil surfacing through the ice is potentially free to spread on the surface waters. After a short periodof five to 10 days, the overflood waters drain through natural holes in the ice (in some cases creating pits
called strudel scours in the seabed). Some surface oil, if not contained or recovered, may be
redistributed under the ice during the process of surface drainage. As the overflood drains, the sea ice
lifts off the bottom and quickly melts to provide open water nearshore a month or more ahead of theoffshore areas.

15 of 28

0

6

18

scale in miles

Figure 4-4
Areas of Spring Overflood Near North Slope Oilfields
4.3

In-situ Burning, A Response Option

Mechanical recovery is considered a primary means of response for both fresh crude andemulsified oil in calm to moderate seas with ice concentrations of less than 3/10. For spills over solid
ice, response actions are very similar to terrestrial spills and therefore mechanical recovery is also
considered the primary response option. The actual efficiencies of mechanical recovery are highlyvariable, depending on skimmer design, oil viscosity, pour point, and degree of emulsification.
Environmental conditions also play an important role in determining efficiencies of mechanical recovery
operations. In some cases, such as the periods of freezeup and breakup, the environmental conditions
limit the use of mechanical containment and recovery. Recent developments and greater understandingof the residual effects of in-situ burning have increased the window of opportunity for in-situ burning andgained acceptance within the State of Alaska as a viable response option.
In-situ burning in open water, using fireproof booms, offers the potential of achieving almost
complete oil removal from the water under a wide range of conditions (fresh to lightly-emulsified oil,seas less than three to five feet, and winds less than 20 knots). Burning is considered as a provenresponse technique that, depending on circumstances, would be used together with mechanicalrecovery to substantially increase the overall oil removal rate. Comprehensive guidelines are available toestablish procedures for requesting, evaluating, and authorizing the use of in-situ burning during an actual
response (Alaska Regional Response Team, May 1994).

16 of 28

In-situ burn efficiencies in the range of 95 to 98 percent have been demonstrated in a wide
variety of tests and field trials in Alaska, Alabama, Norway, and the Canadian East Coast, and have
involved test basins, experimental crude oil spills in ice, and open ocean trials with actual oil(summarized in Buist et al., 1994). High removal rates of 60 to 80 percent have also been achieved in
more extreme conditions with up to 50 percent oil/water emulsions, stronger winds and oil on slush ice
in leads. A fire boom was used successfully during the Exxon Valdez response to remove an estimated360 barrels of crude in 75 minutes (Allen, 1991). Two successful burns were recently carried out in the
United Kingdom using harbor fire boom under adverse conditions of five-foot seas and 15-knot winds(Allen pers. comm. June 1996).
Extensive scientific measurements of large scale burns at sea by U.S. and Canadian scientists
in 1993 have conclusively demonstrated that with appropriate guidelines and safe distances, in-situ
burning poses no significant human health or other environmental risk, either from smoke inhalation, or
toxic compounds associated with the smoke (Fingas et al., 1995). There are three emissions ofpossible concern to regulatory agencies and local residents:• Respirable particulates in the smoke. Measurements have found that the groundlevel concentrations fall below human health limits within a thousand feet downwindof the burn. Concentrations in the plume fall below ambient air quality standards
within several miles (Buist, per. comm. September 1996)• Volatile organic compounds. Levels have been found above normal backgroundas far as 1,500 feet from the fire, but even those slightly elevated levels were still
lower when burning than when the oil slick was left on the water.
• Polycyclic aromatic hydrocarbons (PAH). Extensive monitoring of large scale oilburns has shown that in-situ burning actually removes PAHs and that the sootcontains PAHs at lower levels than the original oil. Results from water analyses
similarly showed that in-situ burning did not adversely affect the underlying watercolumn beyond those effects already associated with the unburned oil slick in the
Newfoundland trials (Daykin et al., 1994).
In addition to removing almost all oil present from the water surface, burning eliminates the needfor storage and disposal. The taffy-like residue survives in small volumes (typically one to ten percent of
the original oil volume). The residue can be manually recovered from the ice surface and deposited inopen top barrels or portable tanks with shovels and pitchforks (Norcor, 1975; Dickins and Buist,
1981). Concerns have been expressed about residues sinking after the burn, and this subject is being
studied. It is not likely that residues from naturally contained slicks, such as in melt pools or win-herded
against ice edges, will sink (Buist et. al., 1995: Trudel et. al., 1996). A comprehensive summary andevaluation of the state of knowledge surrounding the burning of oil spills at sea is provided by Buist et al.
(1994).
The Alaska North Slope Operators currently maintain in excess of 14,000 feet of fire boom,
and six Heli-torches (Figure 4-5) for airborne ignition of oil either within a boom, trapped in broken ice,or lying in melt pools on the ice surface.

17 of 28

Figure 4-5
Heli-torch Ignition System
In summary, ht e expected removal effectiveness for an offshore open water or broken ice
response is highly variable and depends on a large number of factors including timing, weather and sea
conditions, degree of emulsification, and slick conditions. Very few historical response operations haveachieved better than five to 15 percent using mechanical systems (excluding natural processes).
Increased levels of preparedness and equipment resources can improve on these numbers.
Using a combination of mechanical recovery and burning downwind of a surface blowout, Gulf
Canada (1990) calculated removal rates of up to 80 percent of the oil present under ideal conditions.
When environmental factors (visibility, waves, ice, and response times) were included in the final
analysis, the expected effectiveness fell to between 30 and 40 percent. Given the high level ofreadiness on the North Slope, it is possible that crews can achieve equivalent or even better, especiallywith the growing acceptance of in-situ burning as a response option.

18 of 28

4.4

Seasonal Response Techniques

The following sections describe strategies and techniques for dealing with oil spilled in different
combinations of ice and open water, drawing on experience with past spills (both accidental andexperimental) and knowledge of the expected fate and behavior of oil in ice.
4.4.1

Fall and Early Winter Response (October to December)

There are limited mechanical options for recovering large volumes of oil spilled under or among
new and young ice in the fall months of October and November. A "Foxtail" rope mop style skimmer
can be deployed by crane over the side of a response barge or vessel to recover localized oil patches
trapped in water and slush between floes. This is one of the few skimmers able to recover oil fromleads and openings in heavy ice conditions (Counterspil, 1992). Additionally there are 37 portable rope
mop skimming systems within the North Slope response equipment inventories could be placed into
service as required. In areas of heavy oil concentration near the coastline or in available open water
leads other portable skimming systems could be utilized. These would include vacuum, drum and disctype skimmers. It is possible to utilize weir type skimmers under building ice conditions as long as theskimmers are equipped with mechanical systems to handle debris and ice. Any skimming operations will
likely be curtailed by thicker, more concentrated ice within one to two weeks of initial freezeup.
In the beginning of the ice growing season many of the spill response vessels would remain
operational. The jet powered vessels will become inoperative as the brash ice and slush thickens andbegins to interfere with the exposed mechanical parts of the jet systems. Outboard powered vessels will
also be taken out of service when the thickness of the forming ice begins to clog the water intake portson the lower units. Screw driven vessels along with the tug and barge systems will have the longest
sustainable operational period.
The most effective sustainable strategy during freezeup conditions will likely utilize in-situ burning,with the ice providing natural containment and Heli-torches providing a remote ignition source. A
number of tests have shown the feasibility of burning oil trapped in leads with and without the presenceof brash ice and slush (Brown and Goodman, 1987; SL Ross and D. F. Dickins, 1987). Depending
on conditions, removal efficiencies over 90 percent are readily achievable. Weathering the oil up to 20
percent had no significant effect on the results. As the ice growth continues, oil spreading andconveyance processes will decelerate and eventually cease. Ultimately the oil will be incorporated into
the new ice formation.
The oiled ice may move short distances (thousands of feet) in October before becoming landfast.
Oil, during this time, is effectively trapped within the ice and contained from spreading until response
teams can gain access. During the early stages of freezeup, the fringe of new landfast ice protects theshoreline from oiling.
Satellite tracking beacons will be deployed at the spill source to monitor the drift of any oiled ice
away from the spill site. If this ice subsequently becomes incorporated as part of the landfast zone somedistance from the original spill location, conventional winter response procedures can be followed byusing helicopters, ATV’s, and ACV’s to ferry personnel and equipment to the site. Due to thetemperatures, remote locations and darkness involved in these type of operations, personnel safety

19 of 28

considerations will require additional attention. Resources such as personnel shelters, portable lighting,portable heaters and restroom facilities will be required along with the initial response resources.
The contaminated area will be located through visual observation of surface oiling and boring
holes in the ice on a grid pattern to locate sub-surface accumulations of oil. Using underwater lighting
the extent of contamination will be marked and recorded. It may become necessary to auger additionalholes, in a radial pattern, from a known contaminated location to complete the delineation process.
Handheld GPS units will be used to record the exact locations of both surface and sub-surface pools.
Recovery operations on early season, but landfast, ice are very similar to remote terrestrial spill
response actions once the oil is brought to the surface. Teams would be set up to trench, slot and bore
into sub-surface oil pools to gain access to the oil. Surface oil would be bladed into bermed recovery
trenches. Skimmers will recover oil into portable tanks or into small, 500 gallon, airliftable bladders forhelicopter transport to shore. Ice blocks cut from the landfast sheet could also be used to build
containment reservoirs until surface transportation becomes feasible. Figure 4-6 represents a typicalrecovery operation on solid ice. Logistics constraints may demand that in-situ burning be utilized as theprimary recovery option. If there were concerns over the ability to muster adequate resources to thesite or if recovered product could not be transported back to shore within acceptable timeframes,
burning operations would be the most effective option. In all recovery operations, mechanical or in-situ
burning, the site would be thoroughly cleaned during the demobilization operations.

Recovery of Oil on Ice with Small Skimmers

Figure 4-6
Typical Solid Ice Recovery Operations
4.4.2

Mid-winter Response (January to April)

20 of 28

Current technology is considered capable of successfully cleaning up oil spilled onto solid ice.
Although more difficulties are expected in terms of initial detection, a similar successful outcome isexpected for oil spilled under the ice from offshore winter exploration projects (MMS, 1996).
By late December, the landfast ice is normally stable along the entire length of the pipeline out tothe barrier islands (Vaudrey, 1996). From this time until late May, cleanup operations dealing with spills
originating from either offshore exploration or a shoreline production facility can utilize the ice cover as
an secure operating platform for support equipment, including trucks, bladders and portable trenchingequipment. Depending on location, this period of on-ice operation can be extended in some years.
For example, the ice cover in the near shore areas can often support lightweight vehicles by November,and in many years the ice near the barrier islands (although deteriorated) can still support substantial
loads and work crews into late June. While stable winter ice allows for greater access winter arctic
conditions may control feasibility of cleanup operations. Extreme low temperatures present a hazard tooperating heavy equipment and other hydraulic systems. In order to maintain personnel safety andreduce the risk of further contamination through hydraulic failure the North Slope operators have set atemperature limit of -45°F for all heavy equipment operations.
In the case of a known reservoir of oil trapped within the ice sheet in mid-winter, direct pumping
and ice road haul operations will result in almost complete removal of the spilled oil. Larger equipment
would be utilized to gain access to sub-surface pools. In order to eliminate the volume of contaminated
ice the upper layer of ice can be removed prior to exposing the oil pool. Ice roads and pads can bebuilt to allow heavy equipment and vacuum trucks direct access to the oil pools. These trucks would
recover oil directly into attached 300 barrel insulated tankers for transportation to waste disposal
facilities. During extremely cold periods it may be necessary to use steam wands on the oil pools tofacilitate recovery. Additionally, it may become necessary to load 200 to 300 gallons of hot water into
the vacuum tanks from shoreside facilities to maintain internal tank temperatures during recovery andtransport periods.
The logistics are also quite feasible, even without the benefit of an ice road. For example, four
Rollagons hauling bladders for 20 hours per day could transport 20,000 barrels in 15 days from a site
10 miles from shore. This sample calculation assumes a five mph average vehicle speed and a one-hourturnaround. Larger trucks operating on an improved ice road or high speed ACV’s could achieve over
five times as much productivity through greater speeds and loads. Even greater volumes could be dealt
with by adding more equipment over a longer period, or by burning at the site. Final cleanup in June will
use selective burning of oil on melt pools followed by manual recovery of any residue. It is estimatedthat the remaining oil available to enter the marine environment (after all mechanical recovery andevaporation) be less than 10 percent of the original spill volume.
The choice and application of the two primary winter waste handling options of burning in-situ
or removal to shore (Figure 4-7) depend on both time of year and water depth. Once an encapsulated
oil layer is delineated drilling or trenching would be conducted to expose the oil layer for recovery.
Snow melters can be placed on site or at shoreside positions to melt contaminated snow and ice.
Recovered oil can then be trucked to designated disposal wells for reinjection or to a designatedproduction facility for reprocessing. Burning on-site could become the preferred option late in winterwhen there may be insufficient time to transport the recovered oil to shore prior to breakup.

21 of 28

Burning of Oil on Ice andMechanical Removal of Oiled Snow

Figure 4-7
Winter Oilspill Waste Handling Operations
In the case of bottom founded ice encapsulating an oil pool, responders could trench andremove all of the ice blocks and cuttings in very shallow water (zero to four feet). After March it may
be possible to operate within a dry trench in many areas. There may still be a thin layer of frozen soil at
the ice/seabed interface. It may be necessary to penetrate this icy soil layer to release any oil
accumulated within the sediment. Recovered oiled seabed or trench material can be trucked to shore
for interim storage and final disposal.
A mid-winter blowout or pipeline rupture from either a coastline production facility or an
offshore winter exploration project could produce significant areas of surface contamination. Given thepredicted oil plume height and droplet size, the oil concentration on much of the surface area may beinsufficient for successful burning. Exceptions would be: (1) where surface procedures did not achieve
well control and the flow continued for more than a number of days; and (2) within a few thousand feetof the island where up to 4 mm of oil could accumulate over 10 days during periods of light winds. In
order to limit the spreading of thicker oil accumulations close to the well site, a snow berm will need tobe constructed as close as safely possible (Figure 4-8), with the priority being the east-northeast andwest-southwest quadrants (matching the predominant winds).

22 of 28

Containment Using Snow Berm

Figure 4-8
Snow Berm Construction for Winter Oilspill Containment
Plowing surface materials and removing the uppermost ice layer (2 - 4 inches) in the areas ofgross contamination would be conducted utilizing heavy equipment. In areas of lighter contamination
hand recovery operations would be conducted to reduce the total volume of solids recovered.
Previous winter responses on the North Slope have proven this method to be very effective inrecovering all visible traces of crude oil.
As long as the ice remains stable and strong enough to support heavy equipment, the cleanup
operation becomes an exercise in materials handling. In order to recover the oil, it is necessary to plow
and recover the contaminated snow from the ice surface. If the oil is not too weathered, it can berecovered for reprocessing at onshore facilities. Otherwise, contaminated snow and ice can be melted
and reinjected through approved disposal wells.
In rougher ice ridging and rubble, oil cleanup is still feasible, although more labor intensive.
Experiences in Canada with flare burner malfunctions offshore have resulted in minor spills in rough ice
close to the drilling structure. In those cases, a combination of local melting with torches and manualchipping and removal of the oiled ice was used to achieve a high percentage of overall recovery.
6.4.3

Spring Response (May to June)

The period between the first onset of surface snow melt and final deterioration of the landfast ice
provides the best opportunity for in-situ burning of oil that naturally appears on the surface, or remains
on the surface following a winter cleanup operation. However, this period also marks the end of easysite access with any heavy equipment.
In-situ burning is an efficient and effective method of removing oil from a solid ice cover in late
May and June, after ice roads have been closed to traffic. Tests have demonstrated that the oil on thesurface of the ice can be successfully ignited and burned even after weathering for several weeks. Wind
herding of the oil in small pools enables much thinner oil films to be burned than would otherwise be
possible (Dickins and Buist, 1981). Fresh crude must be approximately 0.04 inches thick for ignition to

23 of 28

take place, and weathered crudes in the range of 0.1 to 0.2 inches are readily ignitable. Weathering of
the oil is not as critical as once thought. Ongoing work by SINTEF in Norway has demonstrated that it
is possible to effectively burn fresh crudes with up to 40 percent emulsification (water in oil), albeit at a
reduced efficiency (Guenette and Sveum, 1995). ACS has conducted similar studies in the last few
years concentrating on emulsions made of Alaskan risk oils and seawater. During these studies bench
testing was conducted utilizing various emulsion breakers and gelled fuel mixtures to enhance ignition ofemulsions. Promising techniques from the laboratory were then re-evaluated during both small scale andmeso-scale testing, producing similar results to the SINTEF studies (Buist et. al., 1994)
Work in Alaska and elsewhere has proven that the Heli-torch is a highly effective tool in igniting
multiple oil pools over large areas (Allen, 1987). Slung beneath a helicopter, the Heli-torch is safe andefficient. Approved hand-held igniters can still be used by helicopter-transported field crews to ignite
isolated pools of oil. Burning efficiencies of approximately 97 percent have been achieved in numerous
large scale and meso-scale experiments.
In practical applications, values tend to be lower because a proportion of the oil is contained inpools too small and numerous to burn (refer to pool sizes shown in Table 5-1), and not all of the oil isavailable in sufficiently thick films. As a general rule it is considered practical to burn 80 percent of all
oil present in pools greater than 50 square feet, amounting to 68 percent of the total oil exposed on thesurface (Norcor, 1975; Buist and Dickins, 1981, Gulf Canada, 1990). Manual recovery of any burnresidue or thin unburned oil films on the ice may increase the overall recovery effectiveness by up to 10
percent. In addition, natural evaporation will remove an additional 30 percent of any oil lying on surface
melt pools prior to burning. Realistic estimates for the amount of residual oil remaining after all cleanup
and natural processes up to the point of final ice breakup range from 10 to 20 percent. With
appropriate safety precautions and a helicopter or amphibious vehicle in attendance, surface operations
on the ice can continue until within a few days of breakup.
The small amount of residue left after burning (typically a few percent of the oil available forburning) can be recovered manually with crews on the ice and transported to shore with helicopter
buckets.
As the ice begins to break up in mid-June nearshore, and in early July near the barrier islands,
the response options will depend on the ice concentration as discussed earlier. There will be a period ofseveral weeks when response operations will need to apply a mix of strategies over short periods as
conditions allow: booms and skimmers operated from shallow draft barges in light to moderate ice, insitu burning of thick oil trapped between the floes in heavier ice, and manual cleanup and pumping fromany ice rubble remaining attached to the island, as well as cleanup of any shoreline or gravel pad
surfaces that may have been affected.
As ice concentrations diminish to less than 3/10 by mid-July offshore and by mid-June in thenearshore areas, response operations will become increasingly less restricted by ice more able to rely
on traditional open water mechanical containment and recovery techniques (Figure 4-9).

24 of 28

Figure 4-9
Broken Ice Mechanical Containment and Recovery Operations
5.0

SYNOPSIS: OIL AND ICE SPILL RESPONSE IN THE BEAUFORT SEA

In summary, the knowledge gained through actual spills, drills, experimental field spills, tanktests, and analytical studies has led to the evolution of a number of practical response strategies andoptions to deal with a wide range of nearshore and offshore conditions expected in the Beaufort Sea
adjacent to the North Slope oilfields. Today's arctic spill contingency plans focus on multiple
countermeasure options to cope with different spill situations. In-situ burning in ice and with fireresistantbooms in open water are proven techniques, as is mechanical recovery with the latest generation ofcontainment and recovery equipment.
Each season presents different drawbacks and advantages for spill response. During freezeup
and breakup, drifting ice and limited site access tend to restrict the possible response options andsignificantly reduce recovery effectiveness. Mid-winter involves long periods of darkness and cold
temperatures but provides a stable ice cover that not only naturally contains the oil within a relatively
small area but also provides a safe working platform for oil recovery and transport. The summer open
water period provides the advantage of familiar response techniques but introduces the variability ofwind and waves and the challenge of containing an extremely mobile target.
For seven to eight months of the year, ice aids oil spill response in the Beaufort Sea. Solid ice
naturally contains and immobilizes oil for an extended period of time in the winter (up to 230 days
corresponding to the period of stable ice cover nearshore). The presence of solid landfast ice allows

25 of 28

response teams to mobilize the necessary resources and plan a coordinated winter response effort witha high probability of recovering a large percentage of the spilled oil. At the same time, the environmental
conditions present during the summer months are also much more favorable to offshore cleanup whencompared with many southern areas. For example, broken ice during breakup tends to limit oil
spreading and maintain the oil in thick patches amenable to burning in-situ with a Heli-torch. The
generally low to moderate sea states during the open water period increases the effectiveness of booms
and mechanical recovery systems.
Response planning supported by detailed sensitivity assessments, coastal classifications,computer tracking models, and regular training for the response team members provides the foundation
for an organized and timely response at any time of the year. This foundation is augmented throughcontinuous development of working relationships with other spill response organizations and responsecontractors within the State of Alaska. Further improvements are achievable as the North Slope
Operating Companies continue to support and participate in ongoing research and development of new
or enhanced response methodologies, systems and equipment dedicated to mitigating the effects ofoilspills in the arctic environment.
Recently, a great deal has been learned about Arctic offshore oil spill response through practicalexperience and research. In many respects, the Arctic offshore is a more favorable environment tocarry out an effective oil spill cleanup than many ice-free waters. This is not to say that spill cleanup in
an Arctic environment will ever be a simple operation, or that the impacts of spills in ice covered waters
can be dismissed. There are, however, many aspects of the natural ice environment that, if properly
understood, can be made to work in favor of a suc cessful offshore cleanup.

26 of 28

5.0

REFERENCES

Alaska Regional Response Team. In-situ Burn Guidelines for Alaska. App. 2, Annex F to the Unified Plan, May
1994.
Allen, Alan A., Test and Evaluation of the Helitorch for the Ignition of Oil Slicks. in proceedings of the 10th Arctic
and Marine Oil Spill Program Technical Seminar, Edmonton. 1987.
____Comparison of Response Options for Offshore Spills. in proceedings of the 11th Arctic and Marine Oil Spill
Program Technical Seminar, Vancouver. 1988.
____Controlled Burning of Crude Oil on Water Following the Grounding of the Exxon Valdez. ProceedingsInternational Oil Spill Conference, San Diego, 1991.
Allen, A. A. and W. G. Nelson. “Oil Spill Countermeasures in Landfast Sea Ice.” Proceedings, 1981 Oil Spill
Conference: Prevention, Behavior, Control, Clean-up: American Petroleum Institute, Atlanta, 1981.
Belore, R.C. and I.A. Buist. Modeling of Oil Spills in Snow. Proceedings of the Eleventh Arctic and Marine Oilspill
Program Technical Seminar, pp 9-29. 1988.
Bobra, A.M., and M.F. Fingas. The Behavior and Fate of Arctic Oil Spills. Water Science Technology, Vol. 18 No. 2,
pp 13-23, 1986.
Brown, H.M. and R.H. Goodman. In Situ Burning of Oil in Experimental Ice Leads. Esso Resources Canada Ltd.,Calgary. Environmental Studies Revolving Funds, Report No. 64, Ottawa. 1987.
Buist, I.A.. Spill Related Properties of Fresh and Weathered Alaskan Crude Oils. Alaska Clean Seas, 1994
Buist, I.A., S.L. Ross, B.K. Trudel, E. Taylor, A.A. Allen and A.B. Nordvik. The Science, Technology and Effects ofControlled Burning of Oil Spills at Sea. Marine Spill Response Corporation, Washington, D.C. 1994.
Cammaert A.B., Oil and Gas Under Ice Laboratory Study for Canadian Marine Drillling Limited and Environment
Canada, 1980.
Cox, J.C. and L.A. Schultz. The Transport and Behaviour of Oil Spilled Under Ice. Proceedings of the Third Arctic
Marine Oilspill Program Technical Seminar, Environment Canada, Ottawa, pp 45-61. 1980.
Costanzo, D. Trimble/Orion GPS Oil Spill Tracking Buoy Initial Field Trials. In: Proceedings 17th Arctic and Marine
Oil Spill Program Technical Seminar, Vancouver. 1994.
Counterspil Research Inc. Evaluation of the Foxtail Skimmer in Broken Ice. prepared for Canadian Petroleum
Association, Alaska Clean Seas, Canadian Coast Guard, CISPRI, Environment Canada, MSRC. Technical Report
Number 92-01 produced by Canadian Petroleum Association, Calgary. January 1992.
Counterspil Research Inc. State of the Art Review: Oil-in-Ice Recovery. Technical Report Number 92-02 produced
by Canadian Petroleum Association, Calgary. May 1992.
Daykin, M., A. Tang, G. Sergy, D. Aurand, Z. Wang and G. Shigenaka Aquatic Toxicity Resulting from In Situ
Burning of Oil-on-Water. In : proceedings seventeeth Arctic and Marine Oil Spill Program Technical Seminar,
Vancouver 1994.
Dickins, D. and I. Buist. Oil and Gas Under Sea Ice. prepared by Dome Petroleum Ltd. for COOSRA, Report CV-1,
Volumes I and II. , 1981.
D F Dickins Associates Ltd., and Fleet Technology Limited. Behaviour of Spilled oil at Sea (BOSS): Oil-in-Ice Fate
and Behaviour ; report submitted to Environment Canada, U. S. Minerals Management Service and American
Petroleum Institute. 1992 (DRAFT)
Fingas, Merv and Brian Mansfield, “Oil Spills and Oil Spill Cleanup; Spill Technology Newsletter, Volume 19(4),Environment Canada, 1994.
Guenette, C.C. and P. Sveum. In-situ Burning of Uncontained Crude Oil and Emulsions. Proceedings 18th Arctic andMarine Oilspill Program Technical Seminar, Edmonton. 1995.

27 of 28

Gulf Canada Resources Limited. Kulluk Drilling Program 1990-1992. submission to the Environmental Impact
Review Board, Calgary, Alberta May 1990.
INTEC; Design Basis; Northstar Development Project Preliminary Engineering, prepared for BP Exploration (Alaska),
Inc., Anchorage, Alaska; INTEC Project No. H-660.2 Technical Note TN340, Preliminary Draft dated June 13, 1996.
Kovacs, A., R.M. Morey, D.F. Cundy, and G. Decoff. Pooling of Oil Under Sea Ice. Proceedings, POAC 81: Sixth
International Conference on Port and Ocean Engineering under Arctic Conditions, Quebec, pp 912-922. 1981.
McMinn, LTJG T.J. Crude Oil Behavior on Arctic Winter Ice: Final Report. Office of Research and Development,
United States Coast Guard, Project 734108, Wash. D.C., NTIS Publication No. AP-754, 261 p , 1972.
Minerals Management Service. Beaufort Sea Planning Area Oil and Gas Lease Sale 144: Final Environmental
Impact Statement; U. S. Department of the Interior, , Alaska OCS Region, OCS EIS/EA MMS 96-0012; May 1996.
Nelson, W.G. and A.A. Allen. The Physical Interaction and Cleanup of Crude Oil with Slush and Solid First Year Ice.
Proceedings of the Fifth Arctic Marine Oil Spill Program Technical Seminar, pp 37-59. 1982.
NORCOR Engineering and Research Ltd. The Interaction of Crude Oil with Arctic Sea Ice. Prepared for the Beaufort
Sea Project, Department of the Environment, Victoria, Beaufort Sea Technical Report No. 27. 1975.
North Slope Operators Mutual Aid Agreement for Spill Response, among BPXA, ARCO and Alyeska, February, 1996
Oil industry task group (Shell, Sohio, Exxon, Amoco). Oil Spill Response in the Arctic–Part 1: An Assessment ofContainment Recovery and Disposal Techniques. Anchorage, April 1984.
Oil industry task group (Shell, Sohio, Exxon, Amoco).
Demonstrations in Broken Ice. Anchorage, April 1984.

Oil Spill Response in the Arctic–Part 2: Field

Oil industry task group (Shell, Sohio, Exxon, Amoco).
Documentation. Anchorage, April 1984.

Oil Spill Response in the Arctic–Part 3: Technical

Rosenegger, L.W. The Movement of Oil Under Sea Ice. Prepared by Imperial Oil Limited for the Beaufort Sea Project,
Department of the Environment Canada, Victoria, Beaufort Sea Technical Report No. 28. 1975.
Shafer, R.V.. Oilspill Response Under Breakup Conditions. Alaska Clean Seas Training Manual, 1990.
Shell et al., 1983 see entry under Oil Industry Task Group in Bibliography.
S.L. Ross Environmental Research Limited. Evaluation of Industry's Oil Spill Countermeasures Capability in
Broken Ice Conditions in the Alaskan Beaufort Sea. Prepared for Alaska Department of Environmental
Conservation. 1983.
S.L. Ross Environmental Research Limited and DF Dickins Associates Ltd. Field Research Spills to Investigate thePhysical and Chemical Fate of Oil in Pack Ice. Environmental Studies Revolving Funds, Report No. 062,
Ottawa, 1987
Vaudrey, K.D. Design Basis Ice Criteria for the Northstar Development. prepared for BP Exploration (Alaska) Inc.,
Anchorage by Vaudrey & Associates Inc., San Luis Obispo, California. April 1996.
Vefsnmo, S. and B.O. Johannessen. Exp erimental Oil Spill in the Barents Sea - Drift and Spread of Oil in Broken Ice.
In: Proceedings 17th Arctic and Marine Oil Spill Program Technical Seminar, Vancouver. 1994.
University of Alaska. Alaska Regional Profiles, Arctic Region. Arctic Environmental Information and Data Center,
1975
Wotherspoon & Associates. Detection of Oil in Ice & Burning of Oil Spills in Winter Conditions: State of the Art
Review. prepared for PROSCARAC Inc., Calgary, Alberta. March 1992.

28 of 28