tno environment, energy and process innovationworkshop participants: name first name country company...

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TNO Environment, Energy and Process Innovation Department for ecological risk studies P.O. Box 57 1780 AB Den Helder The Netherlands http://www.mep.tno.nl

Ministry of Transport, Public Works and Water Management North Sea Directorate

P.O. Box 5807 2280 HV Rijswijk

The Netherlands http://minvenw.nl

Operational Response Guidelines

Operational guidelines to policy makers and responders to marine pollution

2002 – 2003

European Commission Directorate General XI Environment, Nuclear safety and Civil Protection Rue de la Loi 200 –B – 1049 Brussels http://europa.eu.int/comm/dg11/index_en.htm Belgium

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This report was prepared on behalf of the European Commission who asked TNO-MEP to perform a study with reference to the call for proposals 2001 in the field of Community cooperation against accidental or deliberate marine to promote a “Net Environmental – Economic Benefit Analysis of the operational response options. Authors: W. Koops, I. van der Velde and R. de Vos TNO Environment, Energy and Process Innovation Department for Ecological Risk Studies This document is the product of two workshops the first held on 27 and 28 of June 2002 and the second on 28 and 29 of November at Schiphol Amsterdam. Workshop participants: Name First

name Country Company Workshop

1 2 Backus Bert Netherlands Ministry of Transport, Public Works and Water

Management, North Sea Directorate Yes No

Bluhm Bernd Germany Bundesministerium fur Verkehr, Bau- und Wohnungswesen

Yes No

Bullimore Blaise United.Kingdom. Countryside Council for Wales Yes Yes Clonan Eugene Ireland Irish Coast Guard, Department of

Communications Yes Yes

Dicks Brian United.Kingdom. ITOPF No Yes Gutiérrez, de la Torre

Laura Spain E.P.E. Sociedad de Salvamento y Seguridad Maritima

Yes No

Hodges Jane United.Kingdom Pembrokeshire Coast National Park Yes Yes Huisman Sjon Netherlands Ministry of Transport, Public Works and Water

Management, North Sea Directorate Yes Yes

Kerambrun Loic France Centre de documentation de _echerché et d´experimentations sur les pollutions accidentelles des eaux

Yes Yes

Koops Wierd Netherlands TNO-MEP, Oil Research Group Yes Yes Rasmussen Carsten,

Aagaard Denmark Danish Navy Yes Yes

Schallier Ronny Belgium Royal Belgian Institute for Natural Sciences, management Unit North Sea

Yes No

Singsaas Ivar Norway Sintef No Yes Sleebos Sonja Netherlands TNO-MEP, Internal and external

communication Yes Yes

Valente Raul Portugal Direccao General Auroridade Martima Yes No Veen, van der Dennis Netherlands Ministry of Transport, Public Works and Water

Management, North Sea Directorate Yes Yes

Velde, van der Inge Netherlands TNO-MEP, Oil Research Group Yes Yes Vos de Ronald Netherlands TNO-MEP, Oil Research Group Yes Yes Wunderlich Michael Germany Bundesanstalt fur Gewasserkunde Yes Yes Although, during the two workshops, grateful use has been made of the technical input and comments of the participants, the text of this document does not necessarily reflect the personal opinion of each individual participant. Contract: No. Sub 01/326398 concerning the project entitled “Net Environmental Economic Benefit Analysis”

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Table of contents

Table of contents TABLE OF CONTENTS..........................................................................................................................3

INTRODUCTION.....................................................................................................................................5

USING THE OPERATIONAL RESPONSE GUIDELINES ..................................................................6

GENERAL BACKGROUND INFORMATION ON OIL RESPONSE GROUP G ...........................7

Description of spilled oil G1.............................................................................................................8 Mass balance of an oil spill G2 ......................................................................................................11 Factors affecting response to marine spills G3 ...............................................................................12 A generalised ranking (preference of response option) G4..............................................................16

RESPONSE OPTIONS GROUP R .....................................................................................................18

Mechanical recovery with dynamic systems R1...............................................................................19 Mechanical recovery using static systems (skimmers, mobs, weirs) R2............................................22 Use of dispersants by spraying R3..................................................................................................25 Mechanical dispersion (adding extra energy) R4............................................................................29 In-situ burning R5..........................................................................................................................31 Monitoring and leave to natural processes R6................................................................................33 Sorbents R7...............................................................................................................................35 Shoreline cleanup (let the pollutant wash ashore) R8......................................................................37

SPILL SCENARIOS GROUP S..........................................................................................................40

SPILL VOLUME SV.......................................................................................................................... 42 Very small spills SV 1.....................................................................................................................43 Small spills SV 2........................................................................................................................44 Medium spills SV3.........................................................................................................................45 Large spills SV4.........................................................................................................................46 Very large spills SV 5.....................................................................................................................47 Huge spills SV 6............................................................................................................................48

SPILL LAYER THICKNESS ST.............................................................................................................. 49 Spill layer thickness <0.01 mm ST1................................................................................................50 Spill layer thickness 0.01- 0.1 mm ST2 ...........................................................................................51 Spill layer thickness 0.1-1 mm ST3 .................................................................................................52 Spill layer thickness 1-10 mm ST4 ..................................................................................................53 Spill layer thickness 10-100 mm ST5 ..............................................................................................54 Spill layer thickness >100 mm ST6.................................................................................................55

SPILL PHYSICAL FORM SP................................................................................................................... 56 Sheen SP 1............................................................................................................................57 Fragmented oil (coverage < 1%) SP 2 ...........................................................................................58 Patches (lumps >1 m2) SP 3 ...........................................................................................................59 Ribbons SP4.............................................................................................................................60 Slicks (homogeneous) SP 5............................................................................................................61 Submerged oil SP 6........................................................................................................................62

SPILL OIL TYPES SO.......................................................................................................................... 63 Light volatile products SO1............................................................................................................64 Moderate to heavy oils SO2............................................................................................................65 Heavy oils and emulsions SO3........................................................................................................66 Residual oils and solid emulsions SO4............................................................................................67

SPILL LOCATIONS SL......................................................................................................................... 68 Open sea SL 1 ............................................................................................................................69 Coastal area SL 2........................................................................................................................70 Partially enclosed water body SL 3................................................................................................71 Estuaries SL 4 ............................................................................................................................72

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Lakes SL5 .....................................................................................................................................73 Rivers (strong current/velocity) SL6 ...............................................................................................74 Canals SL 7 ............................................................................................................................75 Harbour (sheltered port area) SL 8 ................................................................................................76 Port (area to open sea) SL 9...........................................................................................................77

SPILL WEATHER/SEA STATE SW ......................................................................................................... 78 Sea state 1 SW 1 ...........................................................................................................................79 Sea state 2 SW 2.......................................................................................................................80 Sea state 3 SW 3 ...........................................................................................................................81 Sea state 4 SW 4 ...........................................................................................................................82 Sea state 5 SW 5 ...........................................................................................................................83

SPILL CURRENT SC .......................................................................................................................... 84 No current SC1.............................................................................................................................85 Low current SC 2 .......................................................................................................................86 Medium current SC 3 .....................................................................................................................87 Strong current SC 4........................................................................................................................88

GENERAL REFERENCES....................................................................................................................89

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INTRODUCTION

INTRODUCTION Background This document is the result of the workshops following the call 2001 for proposals in the field of Community co-operation against accidental or deliberate marine pollution requested for studies to promote a “Net Environmental – Economic Benefit Analysis” of the operational response options. The result of this study is a comprehensive report, including operational guidelines to policy makers and responders to marine pollution with the objective to support and supplement Member States. These Operational Response Guidelines (ORG) present the information in a similar format to the Impact Reference System (IRS) in the form of a set of reference cards (fiches). The IRS is an integral part of the Community Information System (C.I.S.) for the control and reduction of pollution and covers the effects of oil in the marine environment. This form of presentation was considered to be more appropriate and useful than detailed information duplicating existing published literature. It also linked up to the IRS. Purpose The purpose of the Operational Response Guidelines is to enable policy makers and responders to marine pollution to assess the most appropriate at sea response options in terms of efficiency and costs and to asses environmental benefit from these actions. They are intended to aid decision-making in the event of an oil spill and to enable Member States to develop the most appropriate response strategy to a range of different oil spill scenarios, as a part of the contingency planning process, hence ensuring optimum response in terms of NEEBA. The aim is to define the procedures for selecting the recommended response option/s amongst the various response options currently available in the case of accidental or deliberate marine pollution by oil. The intention is to enable policy maker/responder to facilitate a more thorough decision making process using the most appropriate response options. The operational response guidelines are designed to interface with or be used as an input to combine with local information on sensitivity of the area, spill behaviour and available response means and mobilisation times. Users of these guidelines should always consult national and local contingency plans to identify the most appropriate and successful response to minimise damage, whether that be environmental, ecological, recreational or financial. Contingency plans will give the responder information on sensitivity mapping, the range and limitation of cleaning methods, priority areas defined, strategy for shore and at sea clean up defined, and where wastes can be legally held and disposed of. Scope The Operational Response Guidelines provide guidance to respond to at sea oil spills. The ORG covers the present response options used by the different Member States. The information is presented so decision-makers can use it for a variety of oil spill situations; from small operational spillage’s to large accidental or deliberate spills. The ORG does not provide biological effects of hydrocarbons on marine and estuarine organisms. The IRS, which is part of the C.I.S. for the control and reduction of pollution, covers these effects of oil in the marine environment. Such additional information is essential to decide on the most appropriate response. The ORG should therefore be used in conjunction with the IRS and other sources of (site-specific) information and data.

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USING THE OPERATIONAL RESPONSE GUIDELINES

USING THE OPERATIONAL RESPONSE GUIDELINES The table of contents and the index provide an entry to the guidelines. Each of the reference cards (fiches) listed can be used as a source of information on a response option The first 4 fiches (G1 to G4) deal with General issues and provide background information on:

• Description of spilled oil G1 • Mass balance of an oil spill G2 • Factors affecting optimal response to marine spills (safety aspects) G3 • A generalized ranking (preference of response option G4

The next group of 8 fiches (R1 to R8) provides brief notes on the most frequently used Response options (short description/aim, most applicable spill types, window of opportunity, cost aspects).

• Mechanical recovery with dynamic systems R1 • Mechanical recovery using static systems (skimmers, mobs and weirs) R2 • Use of dispersants R3 • Mechanical dispersion (adding extra energy) R4 • In-situ burning R5 • Monitoring and leave to natural processes R6 • Use of sorbents R7 • Shoreline clean up (let the pollutant wash ashore) R8

The final group of fiches covers all type of spill situations (S). The scenarios mentioned in this document are general scenarios, the response options are the best technical feasible. Local legislation or other limiting conditions may apply.

• Spill Volume scenario’s SV1 to SV6 • Spill layer Thickness ST1 to ST6 • Spill Physical form SP1 to SP6 • Spill Oil type SO1 to SO4 • Spill Location scenarios SL1 to SL9 • Spill Weather/sea state SW1 to SW5 • Spill Current SC1 to SC4

In an actual spill situation, it is recommended that the spill situation fiches (S fiches) should be consulted in addition to the relevant response fiches (R fiches). The general fiches provide basic information for understanding of oil spill response and may be used for better understanding of the problem. For more thorough decision-making on the most appropriate response, the use of a Net Environmental Economic Benefit Analysis method (NEEBA) is advisable. The Operational Response Guidelines has therefore been designed to interface with or be used as input to this decision-making model. Such NEEBA models need to combine local information on the sensitivity of the area, spill behaviour and available response means and mobilization times. The decision making process should take into account the ecological characteristics of communities liable to be affected; the physical characteristics of the potential spill site; human use of environmental resources; details of proposed clean up method/operations. In reaching an optimum clean up response, the advantages and disadvantages of the proposed clean up strategy versus. those of natural clean up should be considered with reference to ecological value and human use of environmental resources. It must be stated that the optimum response often cannot avoid some disadvantages. Users of these guidelines should always consult national and local contingency plans to identify the most appropriate and successful response to minimize damage, whether that be environmental, ecological, recreational or financial. Contingency plans will give the responder information on sensitivity mapping, the range and limitation of cleaning methods, priority areas defined, strategy for shore and at sea clean up, and where wastes can be legally held and disposed of.

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General Background information on oil response Group G

General Background information on oil response Group G The following 4 fiches (G1 to G4) deal with General issues and provide background information on: Description of spilled oil Mass balance of an oil spill Factors affecting response to marine spills A generalized ranking (preference of response option)

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Description of spilled oil G1

Description of spilled oil G1 Floating oil slicks should be systematically characterized. Simple “codes” have been developed as standard terminology for the description of oil pollution. In addition, a “surface appearance-colour code” is described as an estimate of the “volume-per-unit-area” associated with various oil slicks. It is also recognized that floating oil slicks are constantly changing. The location, area coverage, shape, physical properties and chemical properties of a floating oil layer/slick are altered at different rates and to different degrees, depending upon the oil type and many other environmental factors. A useful description of an oil spill would normally include its source, the nature of the release, the location, the oil type and the resulting geometry and condition of any resulting oil slicks. An oil slick is described in the ORG by means of:

Volume SV Layer thickness ST Oil type SO Physical form SP

Characterizing the oil slick on the base of upper mentioned categories is mentioned below. Spill volume The volume of spilled oil is classified in ORG in the following categories:

SV1. Very small < 0.1 m3 SV2. Small 0.1 – 1 m3 SV3. Medium 1 – 10 m3 SV4. Large 10 – 100 m3 SV5. Very large 100 – 1,000 m3 SV6. Huge > 1,000 m3

Spill layer thickness Layer thickness of the spilled oil is classified in ORG in the following categories:

ST1. < 0.01 mm ST2. 0.01 – 0.1 mm ST3. 0.1 – 1 mm ST4. 1 – 10 mm ST5. 10 – 100 mm ST6. > 100 mm

With average oil thickness it is possible to make rough estimates of area polluted, oil film thickness, percent coverage, percent water content. However, even the most experienced individual with a “calibrated eye” will find it difficult. The percent of coverage provides a numerical estimate of the percentage of the designated area that consists of an average oil thickness.

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The magnitude of an oil spill or the area covered by an oil slick depends on the volume and type of oil (SO) and will result in a layer thickness. An oil slick will get larger and larger the longer it floats on the water surface. The magnitude of an oil spill can roughly be classified by means of oil volume and layer thickness. To help with such estimations Table 1 is provided, in which the average thickness is plotted for a broad range of oil spill volumes and their corresponding appearances. The areas and volumes are provided as logarithmic scales with a variety of units.

10-4 – 10-3 mm 10-3 – 10-2 mm 10-2 – 10-1 mm 10-1 – 1 mm 1 – 10 mm 10 – 100 mm

Film Very light Light Moderate Heavy Very Heavy 0,1 – 1 m3/km2

1 – 10 m3/km2

10 – 100 m3/km2

100 – 1000 m3/km2

1000 – 10000 m3/km2

10000- 100000 m3/km2

Sheens

Fluid fresh oil Emulsions

Stable oil layer thickness (equilibrium)

Tar balls

Most crude oils are dark blue to black

Table 1 Oil layer thickness descriptions. Table 2 lists the colours/appearances that are normally characteristic of different thickness and volume. These are based on standard codes developed at the Bonn Agreement colour/appearance code workshop in Horten, Norway. Five colours/appearances are used to estimate the quantity of oil in a slick. CODE Description Layer thickness

interval (µm) Litres per km2

1 Sheen < 0.3 300 2 Rainbow 0.3 – 5.0 300 – 5000 3 Metallic 5.0 – 50 5000 –5,0000 4 Discontinuous true oil colour 50 – 200 50,000 – 200,000 5 Continuous true oil colour More than 200 More than 200,000

Table 2 New colour/appearance code table as proposed by experts of the Bonn Agreement working Group (2001). This is to be known as the new Bonn Agreement colour-appearance code as the description of apparent colour in the previous Bonn Agreement colour-appearance code has partly been replaced by a description of an appearance. With these codes the quantity of oil at the time of observation can be visually estimated during daylight hours. Spill oil type Oil types are roughly defined accordingly to the IRS 1998 EU document:

SO1. Light volatile products: (non-persistent, viscosity 0.5-2.0 cSt, density <800 kg/m3, light distillates with high evaporation rates, highly soluble in water)

SO2. Moderate to heavy oil: (viscosity 4-8 cSt, density 800-950 kg/m3, up to 50% can evaporate, moderate soluble in water)

SO3. Heavy oil and emulsions: (viscosity 8 cSt to semi-solid (avg. 275), density 950-1,000 kg/m3, high viscous, limited spreading, low solubility in water)

SO4. Residual and solid emulsions: (viscosity solid, density >1,000 kg/m3, sometimes semi-solid, limited spreading, very low soluble in water)

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Spilled oil is subject to emulsification: the extent of water-in-oil emulsion (typical water contents are between 5 and 75 %). Through emulsification (water content >60 %) the colour of the oil slick will change into red brown (therefore an emulsion is often called a chocolate mousse). Three types of emulsion can be distinguished: Unstable emulsions usually persist only a few hours after mixing stops. These emulsions readily separate into oil and water due to insufficient water particles interactions. However, the oil may retain small amounts of water, especially if the oil is viscous. Stable emulsions will persist for days, weeks and longer. They show visco-elastic properties and their viscosities are at least three orders-of-magnitude greater than that of the fresh oil. Many stable emulsions increase in viscosity over time. Meso-stable emulsions are probably the most commonly formed emulsions in the field. They may be red or black in appearance and have properties between stable and unstable emulsions. It is suspected that these emulsions either lack sufficient asphaltenes to render them completely stable or contain too many destabilizing materials such as smaller aromatics. The viscosity of the oil may be high enough to stabilize some water droplets for a period of time. Meso-stable emulsions may also degrade to from layers of oil and stable emulsions. Spill physical form With respect to the physical form a distinctions can be made in:

SP1. Sheen SP2. Fragmented semi solid oil (coverage < 1%) SP3. Patches (lumps > 1m2) SP4. Ribbons (length >>> width) SP5. Slicks (homogeneous) SP6. Submerged oil

Figure 1 represents some of these physical forms:

Figure 1 Possible physical natures of oil slicks In summary, an oil slick can be described in the following terms :

• Volume, area and layer thickness of spilled oil • Oil type (from light to very heavy products, crude’s and emulsions) • Appearance/colour (sheen, metallic, true oil colour etc) • Physical form (from tar balls, windrows to continuous spots).

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Mass balance of an oil spill G2

Mass balance of an oil spill G2

In the initial stage of an oil spill, the partitioning of oil between the atmosphere and the water column is important. This equilibrium primarily depends on the vapour pressure and the solubility of the different components in the oil. Components with a high boiling point have a low vapour pressure. The bulk of the spilled oil, which remains on the water surface, consists of components that are non-soluble, or hardly non evaporative and have relatively high boiling points (the fraction C15 and higher). This oil will spread and move on the water surface over a period of time. Small amounts may continue to evaporate (the fraction C10 to C15) and, depending on the sea state, turbulence and quantity spilled, part or all of the remaining oil will naturally disperse or wash ashore. See Figure 2 for a schematic diagram of the partitioning of oil. Components with a low boiling point will mostly end up into the air and water-soluble components with a high boiling point will end up in the water column. Biotic and abiotic processes will degrade components, which dissolve in the water, depending on the speed of degradation they will remain for a shorter or longer period in the water column. The soluble fraction is unimportant with regard to volume/mass balance (not more than 1 to 2%), but will influence the toxicity and physical properties such as surface tension and viscosity. Components with a low boiling point will evaporate into the air. This is mainly the C1 to C10 fractions including the volatile aromatic BTEX compounds (e.g. Benzene, Toluene, Ethyl benzene and Xylene). Small Poly Aromatic Hydrocarbons (PAH in the C10 to C15 range) will also evaporate and only a small part of these PAH will dissolve.

> C 1 5

C 1 0 – 1 5

C 1 – 1 0

P A H

B T E X

W A FO W D

W a t e r c o l u m n

Air

R e c o v e r e d

washed a shore

Short t erm L o n g t e r m

Water sur face

WAF = Water Accommodated Fraction OWD = Oil Water Dispersion Figure 2 Schematic representation of the partitioning of oil after spilled Depending on the type of oil the different fractions mentioned above will be present in different quantities and will each follow its own route in the aqueous environment. Another way to classify the oil is to classify it in oil types (see SO fiches).

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Factors affecting response to marine spills G3


The following factors are used/considered in the spill response(R fiches). and spill scenario’s (S fiches). These factors determine the adequacy and efficiency of the response.

Factor

Description

Area polluted The most important factors influencing the degree of ecological damage of the residual oil on the water surface are: area polluted and retention time of the oil slick on the water surface. The larger the area covered by the oil and the longer oil will stay on the water surface the more chance that vulnerable environmental resources (birds and other marine wildlife) get into contact with the oil. Response to the remaining oil must therefore, aim at either reducing the surface covered by the oil or reducing the retention time of an oil slick on the water surface. The gravity of the effects is also related to the bird density in the area polluted.

Behaviour After release, the oil will immediately weather. In the initial stage of a spill, the most important weathering processes are evaporation and natural dispersion. Due to evaporation, the light components will disappear into the air. Only a very small fraction of the oil will dissolve into the water column. Especially with small operational spillages, the lighter fraction (up to C10) will rapidly evaporate. This fast evaporating fraction also includes the toxic BTEX components. Experiments on plants and organisms have shown that severe toxic effects are associated with these compounds with low boiling points, particular the mono aromatics such as the BTEX. These components are, however, not combatable as they disappear very fast. No response option can prevent that these toxic components (up to C10) get into the environment (mostly into the air compartment).once spilled.

Coverage with oil

Coverage with oil provides a numerical estimate of the percentage of the designated area that consists of an average oil thickness.

Currents The critical current velocity for many crude oils and refined products ranges from 0.7 (0.34 m/s) to 1.2 knots (0.58 m/s). Generally 0.7 knots (0.34 m/s) is accepted as a conservative estimate. Entrainment loss determines how fast a boom or a sweeping system can be towed or the maximum current in which it will be effective. In strong currents, a head wave often builds upstream of the boom. At high current velocities, turbulence occurs at the downstream side of the head wave. Due to turbulence oil droplets can break away from the head wave, become trapped in the flowing water and pass under the boom. Unless the head wave is a considerable distance up stream, oil droplets will not have time to resurface to be contained by the boom. The amount of oil lost in head wave failure depends on the thickness of the oil in the head wave, which is a combination of the water velocity and the specific gravity /density of the oil. The velocity at which the head wave becomes unstable and droplets of oil begin to strip off, is called critical velocity. At this velocity, droplets are entrained in the water streamline and flow under the boom.

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Effects

The main aim of responding to an oil spill, is to minimize the potential impact of oil on human health and the environment. Little can be done to minimize the effects of volatile components, due to the rapid evaporation and natural dispersion. Particularly in case of smaller operational spillages, the BTEX components will disappear from the water surface in minutes to hours. The residual floating oil mainly poses a threat to birds, as these live at the water interface. Especially swimming ducks and diving birds are at risk. Oiled birds usually die. The threshold value for floating oil on the water surface, independent of the composition, is 25 ml per m2.

Emulsification The extent of water in oil emulsion (typical water contents are between 5 and 85 %). Through emulsification (water content >60 %) the colour of the oil slick will change into red-brown (therefore, an emulsion is often called a chocolate mousse). Emulsification (water-in-oil) increases the viscosity of the oil and, thereby, reduces the capacity of pumps. Also the effectivity of dispersants is limited as more water is emulsified into the oil. Another effect of emulsification is the excess of water when emulsified oil is recovered. There are three kinds of emulsions: unstable, stable and meso-stable emulsions. The difference between those emulsions is they remain on the water surface. The most commonly formed emulsions are the meso-stable emulsion. Emulsification is often a result of large droplets that resurface and entrain water.

Flash point An important criterion, with regard to safety requirements on board oil recovery vessels, is the flashpoint of the oil. When the flashpoint of the oil is below 61°C, the safety regulations for the recovery vessels are very stringent (similar to tanker regulations). The flashpoint depends on the composition of the oil. After a spill, the light components quickly evaporate and the flashpoint increases. Model calculations and experiments have shown that the thickness of an oil layer is the prime factor determining the speed of flashpoint increase. As an operational rule of the ‘thumb’ it was concluded that the time (hours) that will elapse until oil in a slick will pass the value of 60 °C is approximately 2 to 6 times the layer thickness (in mm). Thus, for an average free-floating slick of 0.2 mm, it will take 0.4 to 1.2 hour of evaporation time before the flashpoint passes 60°C. Specially equipped recovery vessels, the so-called “first line oil recovery vessels”, complying with the most stringent safety regulations remain necessary. Also, when oil is concentrated – by floating booms or natural barriers- the layer thickness may rapidly increase, with a corresponding decrease in evaporation as a result. This is particular important when fresh oil is concentrated close to the point of release.

Layer thickness The layer thickness plays a very important role, as the evaporation is proportional to the oil-air area of a certain volume of oil. The same amount of oil but spread over twice as large an area, will evaporate roughly twice as fast. An oil slick must have a minimum layer thickness of 2 mm to burn on water.

Mixing capacity water body

In case the natural dispersion of oil is enhanced by adding extra energy, or by applying dispersants, it is important that the oil is rapidly diluted in the water, in order to keep the negative toxic effects to a minimum.

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Mobilization time

The time for a ship/aircraft to get on scene depends on the time to be ready to go and the time to reach the location of the spill. Assuming that the speed of a vessel is about 10 miles/hour, it may take hours to get on the scene of operation. Ships equipped with mechanical recovery facilities or equipped with dispersants normally need the same time to get on scene only the dispersant spraying speed (the encounter rate) is faster. The mechanical adding of extra energy is an option that could be deployed faster as there is less time required, also ships already in the neighbourhood of the spill, could be used. Aircrafts of course are much faster.

Oil type Four oil types, are distinguished that determine the behaviour of an oil spill in the marine environment and the best-suited response. These oil types are: (1) Light volatile products; (2) Moderate to heavy oil; (3) Heavy oils to emulsions; (4) Residual oils and solid emulsions.

Persistence

Hydrocarbons normally biodegrade to water and CO2. Some oil components, however, biodegrade very slowly. Oils that stay long in the aqueous environment due to their slow biodegradation, are called persistent. Such oils should be recovered from the environment instead of enhancing the natural dispersion.

Quantity spilled It is very important to estimate the quantity of an observed spill, before deciding upon the most adequate response. On the basis of the estimated quantity one can determine if a slick is technically combatable and which method is the “best / proper ” response option. To decide if the slick is also operationally combatable, besides quantity/layer thickness, other factors have to be taken into account such as meteorological conditions, mobilisation times, potential threat and weather forecast.

Spill location The location determines the type of response means that can be used. Water depth, wave height and sensitivity of the area are important factors in this respect. The spill location also plays a role in the mobilization time. From a logistic point of view, response options using an aircraft or helicopter can be much faster on scene and their encounter rate is also higher. Single engine aircraft are limited in the distances they are allowed to go from the shoreline.

Spill magnitude The spill size mainly determines the amount of equipment (capacity) that needs to be mobilized. In case of dynamical recovery systems, the encounter rate will be determined by the dimension of the spill (area polluted and the layer thickness). In case of chemically dispersing the oil the spill size (total area) becomes very important for the dilution factor. Increasing spill size results in a decreasing dilution factor. Spill magnitude determines the encounter rate of most response options.

Spill nature and conditions

The following physical forms of a spill can be distinguished: (1) Sheen; (2) Fragmented oil semi solid oil (coverage <1%); (3) Patches (lumps>1 m2); (4) Ribbons; (5) Slicks; (6) Submerged oil The spill nature and conditions are very important in deciding which response option is most adequate.

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Temperature The temperature determines the vapour pressure of each hydrocarbon component in the oil. The vapour pressure increases approximately a factor 1.5 for each 10 degrees temperature increase. Evaporation is proportional to the vapour pressure. This explains why the light components (short hydrocarbon chain length and high vapour pressure) disappear faster from an oil slick than the longer chain length hydrocarbons with much lower vapour pressures. As an example C5 (pentane) will evaporate about 12 times faster than C7 (heptane).

Viscosity Viscosity of the oil is an important property that determines which type of response can be applied. Spraying dispersants is limited by high viscosity of the oil. The efficiency of mechanical oil recovery equipment is often also reduced as the oil viscosity increases. The threshold of oil with a high viscosity is a viscosity higher than 5.000 cSt.

Water depth Water depth is important with respect to dilution in the case of enhancing the natural dispersion of oil into the water column. For that reason some countries restrict the use of dispersants to a certain water depth. (Oil recovery) vessels are limited by their draft. Near the coast and in shallow waters only vessels with little draft can be applied.

Wave height For booms as well as for sweeping systems, containment failure occurs in choppy seas when oil splashes over the barrier’s freeboard. Splash over failure may occur if wave height is greater than the boom freeboard and the wavelength to height ratio is less then 10:1. Gentle swell on the other hand even when the wave height is much larger than the freeboard, will not be a problem for most booms and sweeping systems. Deploy ability is the condition in which the response options can safely and usefully be deployed. The factor that determines the deploy ability for sea going response operations is the state of the sea, i.e. the wave height. Response option with an aircraft or helicopter therefore score a high deploy ability with respect to sea state/wave height. Mechanical recovery methods are limited by maximum wave heights, while enhancing the dispersion is limited by a minimum wave height (mixing energy).

Weathering stage

In most spill situations and in particular for smaller spillages the remaining oil on the water surface exists out of components >C15 and depending the elapse time after release a smaller or larger part of the C10 – C15 components. In the water column a very small fraction of the oil will dissolve. Oil toxicity is reduced as oil weathers. The main problem of weathered oil (emulsion), however, is the smothering effect. The oil will stick to organisms and in particular birds.

Weather An oil slick on the water surface will not stay in its original position but will move under the influence of external factors. The main causes of these transport processes are wind and currents. The transport of a slick on the water surface is an important factor. One must be able to forecast where the slick can be found at what time. The major currents move normally parallel to the coastline. A slick will normally be moved parallel to the coastline by the currents. Onshore wind direction determines when an oil slick will reach the coast. The movement of a slick is about 3% of the wind speed, measured at 10 metres height. In general also the sea state (combination of wind induced waves, current induced waves, tide, current) determines the response option, but also the oil slick shape and position play an important role.

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A generalised ranking (preference of response option) G4


The “window of opportunity” of some methods overlap each other, therefore a priority ranking needs to be made. What method will have preference in a particular spill scenario, where more than one option is possible. There are different ways to rank the options in order of priority. Ranking could be based upon economics (cheapest method first), environmental point of view (most oil out of the environment first), or could be based on operational considerations (availability, mobilization time etc.). Also a combination is possible, depending on the time of year, or spill size. Organizations responsible for combating spills may have a different approach on how to deal with a particular spill. The reasons for attempting to combat an oil spill while it is still at sea are to protect; individual organisms, resources in the vicinity of the slick, the marine environment in general and to minimise the quantity of oil, which comes ashore or enters estuaries. Everything possible should be done to prevent oil to wash ashore on mud flats and salt marshes as they constitute the most ecological sensitive parts and are difficult, if not impossible, to clean up. In order to decide whether or not a response is necessary, or what sort and extent of response is appropriate, the threat posed by the oil must be evaluated. This requires techniques for predicting the behaviour of the oil, which in turn will rely on timely and adequate information about the type and quantity spilled, the location of the spill and weather conditions. Advice on sensitive resources likely to be impacted by the spill will also be needed. Because of the considerable uncertainty which usually surrounds a spill, and the difficulty of predicting the damage, the assessment of the threat will be tentative at first, becoming more firm as information becomes available. The response teams, however, will not be able to await a firm assessment and an element of expert judgement will normally be necessary during at least the first stages of the response. Oil slicks can be technically and/or operationally combatable. Apart from location and weather conditions, the quantity of oil plays an important role in the decision whether the oil could be combated or not. A technically combatable slick is an oil slick, which should be recovered, or treated if at that moment a response mean is on scene. A technically combatable slick can be determined on the basis of volume/layer thickness of oil present and depends on the treat of the spill and the availability of appropriate means. In case of an operationally combatable slick, besides quantity/layer thickness also other factors have to be taken into account, such as meteorological conditions, mobilisation times, potential threat and weather forecast. At present, it is generally accepted for the recovery of oil at sea, that the quantity of oil must be in excess of 1 to 10 m3 (depending on the type of oil) or the polluted area must be more than 1 to 10 km2 in order to determine the slick as “operationally combatable at sea”. To determine the quantity of an oil slick, the colour or appearance code (Table 2) can be used as a guide to estimate oil film thickness. In pollution observation reports the percentage of covered area and a percentage per discriminated colour need to be filled out under “description of the pollution”. Operational spillages are in the range of litres to several m3. In the next paragraph the different response options available and the factors that determine the most appropriate response will be discussed. In order to evaluate oil response options the following criteria are often used: • Deployment ability • Applicability • Capacity • Removed oil ratio • Mobilization time • Costs.

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Deployment ability: The conditions in which the response option can safely and usefully be deployed. The factor that mainly determines the deployment ability for sea going response operations is the sea state or wave height. Applicability: The type of pollutant, which can be handled by the selected response option. Viscosity is an important property of the oil in this respect and problems with debris also could play a role. Capacity: On one hand determined by an encounter rate (mostly speed (m/s) x width (m)) and on the other hand limited by a storage capacity for the recovered oil, or, in case of treatment with chemicals, the load of chemicals that can be taken out to the site. Removed oil ratio: The amount of the oil recovered from the marine environment in relation to the amount spilled. Mobilization time: A combination of the time to make a system ready for use and the sailing/flying time to get on scene. Costs: A combination of investment costs (including regular replacement, depreciation) and the operational costs in an actual situation. Most countries give preference to the response option that recovers as much oil as possible out of the marine/aquatic environment. That is why the dynamic and the stationary recovery response options have the highest priority (first line defense) in most countries. However mechanical recovery is not always the “best” option, if we take into account the high costs and the limited amount of oil that can be recovered. Especially in case of bad weather conditions and/or due to the long arrival time to the spill site before recovery can start, a low volume of oil can be recovered. Net environmental economic benefit recognizes that in some instances an oil spill response action might protect one resource at the potential expense of another. The decision process should take into account the ecological characteristics of communities liable to be affected; the physical characteristics of the potential spill site and human use of environmental resources and details of proposed clean up method. In reaching an optimum clean up response, the advantages and disadvantages of the proposed clean up strategy Vs those of natural clean up should be considered with reference to ecological value and human use of environmental resources. It must be stated that the optimum response often cannot avoid some disadvantages.

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Response options Group R

Response options Group R A group of 8 fiches (R1 to R8) provides brief notes on the most frequently used Response options for oil floating on the water surface (short description/aim, most favourable spill types, window of opportunity)

R1. Mechanical recovery with dynamic systems (sweeping systems) • Dynamic skimmer systems • Dynamic net systems

R2. Mechanical recovery using skimmer in the static way (skimmers with or without booms)

• Weir/ direct suction principle • Brush Vacuum principle • Adhesive Disk/ Drum principle • Vertical or horizontal adhesive bands (endless adhesive rope) • Conveyor belt principle • Drum/ grabber/bucket principle

R3. Use of dispersants by spraying

• Aircraft • Vessel • Hand held

R4. Mechanical dispersion

• Any vessel

R5. In-situ burning

R6. Monitoring and leave to natural processes

R7. Use of sorbents

R8. Shoreline clean up • Let the pollutant wash ashore

Although the last response option is not primarily intended for response to spills at sea. there are situations in which response at sea is technical not feasible with the other options mentioned and shoreline clean-up is the only option left. In this context the feasibility of shoreline clean-up may be feasible, depending on circumstances.

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Mechanical recovery with dynamic systems R1


Dynamic skimmer Sweeping arm system Dynamic skimmer Multipurpose vessel Description/aim Mechanical recovery removes the oil from the marine /aquatic environment. It is mainly designed for use on open water. Sweeping systems, like the sweeping arm attached to the side of a vessel or towed booms, sweep dynamical through an oil slick and collect the oil from the water surface. The main principle of this type of mechanical recovery is to dynamically concentrate the oil on the water surface and recover it into a storage tank. In recent years dynamic systems have enjoyed increasing popularity because, in contrast to stationary systems, they function much more efficient on open waters with current. They can be divided into four categories:

• Self-contained oil pollution recovery vessels, which have a built-in oil removal system and storage facility

• Multi-purpose vessel that can be equipped with dynamic recovery systems units on board • Combined skimmer systems using oil booms • Combined recovery systems using nets (dynamic net systems)

Another distinction that can be made is between vessels that meets the requirements for removal of all types of oil (tanker class, first line oil recovery) and vessels that only can recover oils with a flashpoint higher than 60 °C (second line oil recovery). The advantages of mechanical recovery with dynamic systems are:

• Mechanical recovery removes the oil from the marine environment • High encounter rate (follows the oil)

The disadvantages of mechanical recovery with dynamic systems are:

• The main problem with recovery operations remains; the speed with which equipment can be deployed (sailing time to spill location)

• Decreasing efficiency with increasing wind force, sea state • Keeping dedicated/specialized vessels on permanent stand-by is expensive • Cleaning of vessel and equipment after recovery operation • Special guidance needed for better recovery of the oil (aerial guidance) • Large volumes of oil/water mixture recovered

Recovery capacity The capacity of a dynamic recovery system is determined by: the sailing speed, sweeping width, layer thickness of the oil, sweeping effectiveness, pumping capacity, separation capacity and storage capacity. The maximum sweeping speed depends on the sweeping angle; the smaller angles the higher speed through the water can be sustained, before oil escapes underneath the system The encounter rate is determined by sweeping speed times sweeping width times layer thickness. In optimum dynamic oil recovery systems above mentioned variables must be adjusted to one another as efficiently as possible. There is no sense in using a dynamic system with a small storage tank for the recovered oil if the expected encounter rate is very high or if the pump capacity is very high. Practical experiences have shown that an average retention time > 20 minutes suits sufficient separation of oil droplets. This means that the maximum pump capacity is determined by the storage/separation tank size of the ship deploying the recovery system.

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The encounter rate of sweeping systems can be extended by the use of oil booms to increase the sweeping width. Costs The operational costs of dynamic systems are mainly determined by the cost of the vessel(s) and the costs of the recovery system. Built-in oil removal systems are more expensive than multipurpose vessels able to take or accommodate sweeping units on board. A dedicated vessel with permanent storage capacity on board is costly. Guidance from the air will be needed to evaluate the recovery results but will also increase the cost for the recovery operation Conclusion The mechanical recovery options at sea are mainly designed to be used for larger spills (>10m3). For smaller spillages (<0.1 – 10 m3) this method is relatively expensive and can be ineffective, depending on the oil type. Mechanical recovery with dynamic systems will mostly not remove all the oil from the water surface. Continuous spreading of the oil slick and turbulence at the water surface are the main reasons for incomplete recovery. Reduction of the negative environmental and/or economic effects will mainly be achieved if the water surface can be cleaned quickly. Reducing the amount of oil on the water surface will speed up the natural dispersion of the remaining oil. Mechanical recovery methods work best in calm conditions and effectiveness is decreased as sea state increases. In heavy sea conditions, sea state/wind forces in excess of 5 Beaufort, recovery at sea is not effective.

Definition of technical feasibility ++ Will be very effective - Ineffective or no practical application + Moderately effective - - Counter productive +/- May be feasible, depending on circumstances

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Description

Spill volume Dynamic skimmer systems

Dynamic net systems

SV1 Very small spills (<0.1 m3) - - SV2 Small spills (0.1 – 1 m3) - +/- SV3 Medium spills (1 – 10 m3) +/- ++ SV4 Large spills (10 – 100 m3) ++ +/- SV5 Very large spills (100-1,000 m3) ++ +/- SV6 Huge spills (>1,000 m3) ++ +/-

Spill thickness ST1 <0.01 mm - - ST2 0.01-0.1 mm +/- - ST3 0.1-1.0 mm ++ +/- ST4 1.0-10.0 mm ++ ++ ST5 10.0-100.0 mm ++ ++ ST6 >100.0 mm ++ ++

Physical form SP1 Sheen - - SP2 Fragmented oil (coverage <1 %) + ++ SP3 Patches (lumps >1m3) ++ ++ SP4 Ribbons ++ - SP5 Slicks (homogenous) ++ +/- SP6 Submerged oil - +/-

Spill oil type SO1 Light volatile products ++ - SO2 Moderate to heavy oils ++ - SO3 Heavy oils and emulsions ++ + SO4 Residual oil and solid emulsions + ++

Spill location SL1 Open sea ++ ++ SL2 Coastal area (non-sheltered) ++ ++ SL3 Partially enclosed water body ++ ++ SL4 Estuaries ++ ++ SL5 Lakes ++ ++ SL6 Rivers ++ ++ SL7 Canals ++ ++ SL8 Harbours (sheltered port area) +/- +/- SL9 Port (area to open sea) ++ ++

Spill weather/sea state SW1 Sea state 1 (wind speed 0 – 2 m/s, wave height 0 – 0.4 m) ++ ++ SW2 Sea state 2 (wind speed 2 – 7 m/s, wave height 0.4- 1.7 m) ++ ++ SW3 Sea state 3 (wind speed 7 – 12 m/s, wave height 1.7 – 3.0 m) ++ ++ SW4 Sea state 4 (wind speed 12 – 18 m/s, wave height 3.7 – 4.3 m) - - SW5 Sea state 5 (wind speed >18m/s, wave height >4.3 m) - -

Spill site current SC1 No current (hardly any dilution) ++ ++ SC2 Low to 0.34m/s (little dilution) ++ ++ SC3 Medium 0.34 – 0.58m/s (medium dilution) ++ ++ SC4 High >0.58m/s (large dilution) + +

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Mechanical recovery using static systems (skimmers, mobs, weirs) R2


Disk skimmer Vertical adhesive band Conveyor belt Weir skimmer Description/aim The static mechanical recovery option removes the oil from of the marine/aquatic environment. Booms in combination with skimmers are used to concentrate the oil and to recover the oil from the water surface. Skimmers can be divided into three main groups:

• skimmers using the flow properties of oil and/or oil-water mixture; • skimmers using the adhesion of oil; and • bucket systems that pick up the oil or scoop the oil from the water surface.

Within the first group, which exploit the flow properties, we can distinguish the following principles: vacuum, weir and conveyer belt. Skimmers that make use of the adhesion property of oil can be further divided into: disc/drum type, vertical or horizontal band/rope type and brush. Skimmers that make use of the adhesive property of oil are generally very suitable for thin types of oil. They have the advantage that they entrain little free water; the oil is removed in the pure form. The third group, the bucket systems, like conveyor belt and grabber are also able to remove solid oil from the water surface. With a conveyor belt and the brush principle, oil can be removed in two ways: it can be scooped from the water and the oil may adhere to the belt or brush. In summary the following principles can be distinguished:

• Vacuum principle • Adhesive Disk/Drum principle • Vertical or horizontal adhesive bands (endless adhesive rope) • Conveyor belt principle • Weir/ direct suction principle • Brush principle • Drum/ grabber principle

Many countries use skimmers to remove spilled oil from the marine / aquatic environment. There are hundreds of different commercial skimmers available on the market. They use one or a combination of the principles to recover the oil as mentioned above. Skimmers are available in different sizes and capacities depending on the area/ spill situation in which one wants to use them. The advantages of static mechanical recovery using booms and skimmers are:

• Removes oil directly from the marine environment • Can be used in shallow waters • Fairly good pickup rate in thick accumulations of oil with the appropriate type of skimmer • Can be used under piers, ponds, and parallel to shorelines during beach cleaning

The disadvantages of static mechanical recovery using booms and skimmers are:

• Recovery rate influenced by wave height, oil viscosity • Recovery efficiency decreases rapidly in thin slicks or oil scattered over a large area • Oil has to be brought towards the skimmer • Recovery depends on boom, pump and hoses. If one piece of equipment fails, the whole system fails • Cleaning equipment after recovery operation • Guidance from the air required for optimal recovery

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Recovery capacity The capacity of skimmers is mainly determined by the pumping system used to transport the oil to the storage tank. Pump capacities are very sensitive to the viscosity and layer thickness of the oil. The encounter rate of static oil recovery systems is difficult to calculate as many factors determine the amount reaching the skimmer. The use of booms to concentrate the oil and any wind drift which moves the oil towards the skimmer both influence the encounter rate. The term capacity does not mean the same thing for all skimmers. On the one hand it may refer to the quantity of oil encountered by a system; on the other hand it may mean the capacity for transport to the storage facility. Cost Costs of skimmers and booms vary considerably. Sea/ocean going skimmers are very expensive, while small units suitable for ports or inland water are less expensive. Guidance from the air will be needed to evaluate the results. Conclusion The success or failure of static oil recovery systems depends in the first instance on the speed at which skimmers and booms are launched and to what degree the spreading of the oil can be controlled. Because there is great variety in skimmers, the type of skimmer that can be used effectively depends on a number of factors, such as:

• Spill quantities • The type properties of the oil • The local conditions: water depth, current (the critical velocity is 0.58m/s) • The weather/sea state condition: up to sea state 3

In view of the fact that so many factors play a role in the oil removal process, different type of and sizes of skimmers need to be stand-by for different situations, each with its own specific application. Most skimmers are best suited for calm water, since their effectiveness is sharply reduced by wave action. There are some differences between the different skimmer principles. Disk/drum skimmers and all adhesive skimmers have the advantage that they are very useful on light and moderate oils and can also be used for very small spills as they recover pure oil without water. The endless rope, which is also an adhesive skimmer, and in particular the vertical version of the endless rope, has the advantage that it can be used in higher wave conditions as well. The main advantage of the conveyor belt/drum, or any other bucket system, is that it can handle solid materials and debris which makes it very useful in harbour areas. Weir systems have high recovery capacities and as they often recover an excess of water, they can handle heavy and residual oils using the water as a carrying phase. Brush skimmers can be used on heavy, high viscous and solid oils. Remark It is emphasized that the ability to recover oil efficiently by using stationary skimmers, declines dramatically from wind force 4 Beaufort onwards. Large skimmers may still be useful, although their stability in waves is affected.


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Description

Spill volume Vacuum Disk,

drum Endless

rope Conveyer

belt Weir Brush Drum,

Grabber 1 Very small spills (<0.1 m3) ++ +/- +/- - +/- - - 2 Small spills (0.1 – 1 m3) ++ + + + + + + 3 Medium spills (1 – 10 m3) + + + + + + + 4 Large spills (10 – 100 m3) +/- ++ ++ ++ ++ + ++ 5 Very large spills (100-1,000 m3) - ++ ++ ++ ++ ++ ++ 6 Huge spills (>1,000 m3) - +/- +/- ++ +/- +/- +/-

Spill thickness 1 <0.01 mm - +/- +/- - - - - 2 0.01-0.1 mm ++ ++ ++ +/- +/- +/- +/- 3 0.1-1.0 mm ++ + + + + + + 4 1.0-10.0 mm + ++ ++ ++ ++ + ++ 5 10.0-100.0 mm +/- ++ ++ ++ ++ ++ ++ 6 >100.0 mm +/- ++ ++ ++ ++ ++ ++

Physical form 1 Sheen - - - - - - - 2 Fragmented oil (coverage < 1%) - - - +/- +/- +/- +/- 3 Patches - - - ++ ++ + + 4 Ribbons (length>>>width) - ++ ++ ++ ++ ++ ++ 5 Slicks - + + + + - - 6 Submerged oil - - - +/- - - +/-

Spill oil type 1 Light volatile products ++ + + - + - - 2 Moderate to heavy oils ++ ++ ++ + ++ + +/- 3 Heavy oils +/- +/- +/- ++ ++ ++ ++ 4 Residual oil - - - ++ +/- ++ ++

Spill location 1 Open sea +/- ++ ++ + ++ ++ ++ 2 Coastal area +/- ++ ++ ++ ++ ++ ++ 3 Partially enclosed water body ++ ++ ++ ++ ++ ++ ++ 4 Estuaries +/- ++ ++ ++ ++ ++ ++ 5 Lakes ++ ++ ++ ++ ++ ++ ++ 6 Rivers +/- ++ ++ ++ ++ ++ ++ 7 Canals ++ ++ ++ ++ ++ ++ ++ 8 Harbour sheltered port area ++ ++ ++ ++ ++ ++ ++ 9 Port area to open sea +/- ++ ++ ++ ++ ++ ++

Spill weather/Sea State 1 Sea state 1 (wind speed 0-2 m/s) ++ ++ ++ ++ ++ ++ ++ 2 Sea state 2 (wind speed 2- 7 m/s) + + ++ + ++ + + 3 Sea state 3 (wind speed 7-12 m/s) +/- +/- ++ +/- ++ +/- +/- 4 Sea state 4(wind speed 12-18 m/s) - - - - - - - 5 Sea state 5 (wind speed >18 m/s) - - - - - - -

Spill site current 1 No current (hardly any dilution) ++ ++ ++ ++ ++ ++ +++ 2 Low to 0.34 m/s (little dilution) ++ ++ ++ ++ ++ ++ ++ 3 0.34 – 0.58 m/s (medium dilution) + + ++ ++ ++ ++ ++ 4 High >0.58m/s (large dilution) - - - - - - -

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Use of dispersants by spraying R3


Single engine aircraft Airplane spray path Spray vessel Vessel spray path Description/aim Dispersants are a group of chemicals designed for spraying on oil slicks, in order to accelerate the process of natural dispersion. Dispersants are mixtures of surfactants in one or more solvents, specifically formulated to enhance the rate of this natural process and specially designed for seawater (in fresh water dispersants do not work). The use of dispersants is widespread for combating pollution at sea. Improvements in dispersants have led to renewed interest in their use. The use of dispersants can, under favourable conditions, bring about the complete dispersion of the oil. The oil will enter the water column as very small droplets and concentrations will quickly drop to very low levels due to dilution. Unfavourable conditions for applying dispersants are shallow waters and thick oil layers, as both will result in too high concentrations of oil in the water column underneath the slick. Also a calm condition at sea is an unfavourable condition, because some energy by wave action is needed for the dispersion process. The window of opportunity for using dispersants is one or two days, because viscosity of weathered oil will become too high to disperse. Their purpose/use is intended to minimize the damage caused by floating oil, for example to birds or sensitive shorelines by converting floating oil into small droplets dispersed in the water column. Spraying dispersants may be the only means of removing oil from the sea surface, particularly when mechanical recovery is not possible due to high turbulence at the water surface. Spraying can be done either by aircrafts or by vessels and handheld equipment. In the next part of this section the different spraying methods are explained. Aircraft In general two categories of aircraft are used: those designed for agricultural or/and pest control operations which require minor modification for dispersant application, and those which have been specifically adapted for the application of spraying dispersants. Several types of helicopter have also been converted, although most are able to carry the so-called ‘slung bucket’ spray systems without the need for modifications. The choice of aircraft will be primarily determined by the size and location of the spill, although local availability will also be a crucial factor. The endurance, fuel consumption, turn around time, payload and the ability to operate from short or improvised landing strips are all important factors. In addition, the aircraft should be capable of operating at low altitude and relatively low speeds (50-150 knots) and be highly maneuverable. Distinctions are made in aircraft by payload capacity of the dispersant since this is the crucial factor in spill situations.

• Small fixed wing aircraft, including small helicopters (single engine) o Payload up to 1000 litres o Examples: Piper, Cessna, and Islander

• Medium aircraft, and larger helicopters (multi engine) o Payload 1000 – 5000 litres o Examples: Canadair, DC3, Huey, Sea King

• Large aircraft o Payload >5000 litres o Examples: DC6 and Hercules

The advantages of aerial spraying of dispersants are:

• Reduces the threat of an oil slick to surface organisms • Reduces the amount of oil that can wash ashore

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• Better overview, more selective spraying than from a vessel • Fast response option and turn around • High capacity • Not influenced by current, rocks and shallow waters • Movement of dispersed oil only by current, not by wind anymore • Increased availability of the oil to natural degradation

The disadvantages of aerial spraying of a dispersant are:

• Oil transfer from sea surface to the water column • Oil stays in the marine environment • Increases the threat in subsurface organisms by temporarily enhancing the concentration of toxic oil

fraction entering the water column • Tainting of fish and shellfish • Effectiveness of treatment is limited by increasing viscosity of the oil (oil type weathering • Extra input to the environment of chemicals additional to the oil • Not effective below sea state 1

Capacity The capacity of aerial spraying is determined by the amount of dispersants that can be taken on board and the flying speed of the airplane. The encounter rate is determined by the spraying width, the spraying speed and the layer thickness. The dispersant to oil ratio is 1: 5 down to 1: 50 depending on the layer thickness differences the type of oil and the type of dispersant. Costs The operational cost of applying dispersants is a combination of the costs of the airplane and the dispersants used. Vessels / Handheld equipment Methods for dispersant application from (sea going) vessels include spraying through a set of nozzles fixed on outboard riggers and spraying from modified fire monitors. The dispersants are released while the vessel is sailing through the oil slick. The vessels propellers and the bow waves achieve additional mixing. From such a vessel breaking board can also be applied to increase the mixing. Spraying with handheld equipment (crop dusters) can be used in small vessels/ dinghy’s or from the shoreline. The advantages of spraying dispersant from a vessel / handheld equipment are:

• Direct input mechanical energy by vessels propellers and bow waves • A vessel can take relatively large amounts of dispersants on board • At the spill site direct monitoring of effectiveness, • Better consideration of the of amount dispersant that should be sprayed • Small local spills in hard to reach places (under wharfs) can be reached with handheld equipment

The disadvantages of spraying dispersant from a vessel are:

• Oil stays in the marine environment • Vessels are slow with respect to arrival time on scene • Vessels are expensive • A vessel is influenced by current, rocks and shallow waters • Mixing energy is required • Oil is difficult to locate from boat

Capacity The capacity of the dispersant method is determined by the amount of dispersant that can be taken on board and the encounter rate of the vessel. The encounter rate is determined by the spraying width, the spraying speed and the oil layer thickness. The dispersant to oil ratio is 1: 5 down to 1: 50 depending on the layer thickness differences and the type of oil. Costs

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The operational costs of applying dispersants are a combination of the costs of the vessel and the dispersants used Conclusion Dispersant removes the oil from the water surface into the water column and, thereby reducing the impact on birds and coastline. Dispersants also have the ability to treat a lot of oil with a relatively small amount Chemical dispersion is limited by; minimum turbulence of the water and water mixing, the location, weathering process, and the type of oil. Use of dispersant, by spraying can be a fast response when using aircrafts for spraying the dispersants over the oil. Small, medium and large aircrafts are best used in the range 1-100 m3, >1 m3 and >100 m3 respectively. Handheld spraying equipment is best suited to small spillages. Vessels are mostly moderate effective, due to their mobilization time. The mobilization time of vessels is often much longer than the mobilization time of aircrafts in the case of spills at sea. Oil slicks are often not homogeneously spread over the polluted area. The capacity (encounter rates of spraying dispersants) depends heavily on the layer thickness and coverage. Clean places (no oil coverage) should be avoided in spraying operations. Also other social and political factors could influence the use of dispersants.


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Description Spill magnitude

Small aircraft

Medium aircraft

Large aircraft

Vessel Hand held

SV1 Very small spills (<0.1 m3) - - - + ++ SV2 Small spills (0.1 – 1 m3) +/- - - +/- ++ SV3 Medium spills (1 – 10 m3) ++ ++ - + + SV4 Large spills (10 – 100 m3) ++ ++ + + +/- SV5 Very large spills (100-1,000 m3) +/- ++ ++ + - SV6 Huge spills (>1,000 m3) +/- ++ ++ + -

Spill thickness ST1 <0.01 mm - - - + ++ ST2 0.01-0.1 mm - - - +/- ++ ST3 0.1-1.0 mm ++ ++ ++ ++ +/- ST4 1.0-10.0 mm + + + + - ST5 10.0-100.0 mm - - - - - ST6 >100.0 mm - - - - -

Physical form SP1 Sheen -- -- -- - +/- SP2 Fragmented oil (coverage < 1%) - - - - - SP3 Patches - - - - - SP4 Ribbons (length>>>width) ++ + - + ++ SP5 Slicks + ++ ++ ++ +/- SP6 Submerged oil - - - - -

Spill oil type SO1 Light volatile products - - - - - SO2 Moderate to heavy oils ++ ++ ++ ++ ++ SO3 Heavy oils +/- +/- +/- +/- +/- SO4 Residual oil - - - - -

Spill location SL1 Open sea - ++ ++ ++ - SL2 Coastal area + + ++ + - SL3 Partially enclosed water body - - - - - SL4 Estuaries +/- +/- +/- +/- - SL5 Lakes - - - - - SL6 Rivers (strong current/velocity) (freshwater) +/- - - +/- +/- SL7 Canals (no-low current/velocity) - - - - - SL8 Harbour sheltered port area - - - +/- + SL9 Port area to open sea + +/- - +/- +

Spill weather/Sea State SW1 Sea state 1 (wind speed 0 – 2 m/s) - - - - - SW2 Sea state 2 (wind speed 2 – 7 m/s) ++ ++ ++ ++ ++ 3SW Sea state 3 (wind speed 7 – 12 m/s) + + ++ + + SW4 Sea state 4 (wind speed 12 – 18 m/s) - - +/- - - SW5 Sea state 5 (wind speed >18m/s) -- -- -- - -

Spill site current SC1 No current (hardly any dilution) +/- +/- +/- +/- +/- SC2 Low to 0.34m/s (little dilution) +/- +/- +/- +/- +/- SC3 Medium 0.34 – 0.58m/s (medium dilution) + + + + + SC4 High >0.58m/s (large dilution) ++ ++ ++ ++ ++

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Mechanical dispersion (adding extra energy) R4


Adding extra energy Breaker boards Typical slick appearance Spills disappear naturally Description/aim Natural dispersion of spilled oil can result from agitation caused by wave action. Agitation will cause an increase of the surface between water and the oil (increase of smaller droplets). This process of agitation does not happen for all oil types (SO). It is slower and less efficient than the application of dispersant chemicals. In some circumstances, the addition of extra mechanical energy from the propellers, or bow wave of vessels may assist this process, for example in relatively calm (but not flat calm) conditions and after the application of chemicals. This response method is only effective at small amounts of light oil (in particular thin oil layers). For large amounts and other kind of oils, this response method should not be considered. The advantages of using mechanical dispersing of oil are:

• Fast response method, as use can be made of any available boat • It reduces the possibility of contamination of sea birds and mammals with oil • Enhances the oil biodegradation without additional chemicals • Enhances natural dispersion • Low costs • No special skills required, other than knowing the limitations of the technique

The disadvantages of mechanical dispersing use are the following: By introducing the oil into the water column, it may adversely affect some marine organism

• Is less effective in calm sea conditions as a minimum background mixing energy is needed • Use is limited to medium/light oils in small volumes and thin layers • Ineffective on weathered and viscous oils. May be highly counterproductive if misapplied to these oils

by breaking the oil to small fragments, which are more difficult to contain and recover. • Unable to add significant energy in rough seas

Capacity The capacity of mechanically adding energy is determined by the vessels speed times bow wave width (approximately 4 times vessel width) times layer thickness times efficiency factor. The efficiency factor depends on the number of times one has to repeat the same treated path before the slick has completely disappeared from the water surface. Costs The operational costs of this method depend on the hiring cost of a vessel, and the opportunity that it can be on scene very fast. Little experience is required. Guidance from the air will be needed to evaluate the results. Conclusion This technique is, however, not a main stream clean up technique and can easily cause more problems if misapplied. This technique should be used only with great caution. The mechanical dispersion option should primarily be used for spills between 0,1 and 10 m3 of thin layer oil slicks and low to medium viscous oils. Mechanical dispersion is a relatively cheap and effective way to enhance the dispersion process. Reducing the retention time of the oil slick on the water surface by enhanced dispersion results in less negative effects to birds. This response option is also applicable, when the major part of the oil is removed mechanical, to treat the remaining floating oil.


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Description Spill volume

Vessel of opportunity

SV1 Very small spills (<0.1 m3) ++ SV2 Small spills (0.1 – 1 m3) ++ SV3 Medium spills (1 – 10 m3) + SV4 Large spills (10 – 100 m3) +/- SV5 Very large spills (100-1,000 m3) - SV6 Huge spills (>1,000 m3) -

Spill Thickness ST1 <0.01 mm ++ ST2 0.01-0.1 mm + ST3 0.1-1.0 mm - ST4 1.0-10.0 mm - ST5 10.0-100.0 mm -- ST6 >100.0 mm --

Physical form SP1 Sheen/Rainbow (silvery/grey) ++ SP2 Tar balls - SP3 Patches - SP4 Ribbons of oil ++ SP5 Slicks + SP6 Submerged oil - Spill oil type SO1 Light volatile products +/- SO2 Moderate to heavy oils +/- SO3 Heavy oils -- SO4 Residual oil -

Spill location SL1 Open sea ++ SL2 Coastal area + SL3 Partially enclosed water body + SL4 Estuaries - SL5 Lakes - SL6 Rivers +/- SL7 Canals - SL8 Harbours (sheltered port area) +/- SL9 Port (area to open sea) +/-

Spill weather/sea state SW1 Sea state 1 (wind speed 0 – 2 m/s, wave height 0 – 0.4 m) - SW2 Sea state 2 (wind speed 2 – 7 m/s, wave height 0.4- 1.7 m) ++ SW3 Sea state 3 (wind speed 7 – 12 m/s, wave height 1.7 – 3.0 m) ++ SW4 Sea state 4 (wind speed 12 – 18 m/s, wave height 3.7 – 4.3 m) +/- SW5 Sea state 5 (wind speed >18m/s, wave height >4.3 m) -

Spill site current SC1 No current (hardly any dilution) +/- SC2 Low to 0.34 m/s (little dilution) +/- SC3 Medium 0.34 – 0.58 m/s (medium dilution) + SC4 High >0.58 m/s (large dilution) ++

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In-situ burning R5

In-situ burning R5

Oil burn Fire resistant boom Smoke Fire on board Description/aim In-situ burning (ISB) involves the controlled combustion of spilled oil. While ISB is commonly used in conjunction with waterborne spills, controlled combustion may also involve spills along or on shorelines, in wetland areas, on dry land, or even in containers (e.g., vessels, barges, etc.). In-situ burning generally involves the deliberate ignition of spilled oil (or oil that is about to be spilled) in order to eliminate the oil before it spreads over large areas, makes contact with shorelines, and/or impacts sensitive resources. This fiche focuses on the controlled burning of oil in open-water, marine environments. Any attempts to burn oil can result in production of considerable volumes of smoke, which has aesthetic and air pollution implications. The advantages of in-situ burning are:

• High elimination rates; and high efficiency depending on oil type and spill conditions • Minimum recovery & storage • Minimum disposal & cleanup. Disposal would involve only the unburned oil and residue • Fixed burning continuous spill sources in relatively low currents allow for safe and effective burning

in a boom nearby • Minimum water depth constraints. Only enough water needed to accommodate the draft requirements

of the boom towing vessels. Shallow-water burns are possible without boats • Maybe useful option in ice

The disadvantages of in-situ burning are:

• Smoke plume or “visual impact” • Oil layer must be sufficiently thick to support combustion (i.e., at least 2-3 mm, and preferably 10 cm

or more), it must be relatively low in water content (i.e., <20%-30%) and it must contain sufficient volatiles to allow ignition and sustained combustion

• Same sea state constraints as using booms in combination with skimmers • Cannot be used near stricken vessels or coastal communities where secondary fires may initiated • Atmospheric pollution. Secondary pollution by SOx and NOx as well as CO2 (greenhouse gas) • Human safety risks • Residue may sink into the water column

Capacity Need for containment. Because of the above thickness constraints, and the tendency for oil to spread quickly, fire booms or other barriers are necessary to contain and thicken the oil throughout the combustion process. Conclusion ISB is not a very environmental sustainable solution. It may be useful in special circumstances. Limited window of opportunity. Because of the weathering and emulsification that occurs rapidly at sea, burning must be conducted as early as possible (preferably within the first 12 to 24 hours of exposure). Very calm seas may extend “window” to 48 hours or more. For spills in cold climates, particularly when trapped on, in or under ice/snow, burning may be conducted months or even years later.


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In-situ burning R5


In-situ burning

SV1 Very small spills (<0.1 m3) - SV2 Small spills (0.1 – 1 m3) - SV3 Medium spills (1 – 10 m3) - SV4 Large spills (10 – 100 m3) +/- SV5 Very large spills (100-1,000 m3) +/- SV6 Huge spills (>1,000 m3) +/-

Spill Thickness ST1 <0.01 mm - ST2 0.01-0.1 mm - ST3 0.1-1.0 mm - ST4 1.0-10.0 mm ++ ST5 10.0-100.0 mm ++ ST6 >100.0 mm ++

Physical form SP1 Sheen - SP2 Fragmented oil (coverage < 1%) - SP3 Patches +/- SP4 Ribbons (length>>>width) - SP5 Slicks +/- SP6 Submerged oil -

Spill oil type SO1 Light volatile products - SO2 Moderate to heavy oils +/- SO3 Heavy oils and emulsions +/- SO4 Residual oils and solid emulsions -

Spill location SL1 Open sea +/- SL2 Coastal area +/- SL3 Estuaries +/- SL4 Partially enclosed water body +/- SL5 Lakes - SL6 Rivers (strong current/velocity) - SL7 Canals (no-low current/velocity) - SL8 Harbour sheltered port area - SL9 Port area to open sea -

Spill weather/sea state SW1 Sea state 1 (wind speed 0 – 2 m/s, wave height 0 – 0.4 m) +/- SW2 Sea state 2 (wind speed 2 – 7 m/s, wave height 0.4- 1.7 m) +/- SW3 Sea state 3 (wind speed 7 – 12 m/s, wave height 1.7 – 3.0 m) - SW4 Sea state 4 (wind speed 12 – 18 m/s, wave height 3.7 – 4.3 m) - SW5 Sea state 5 (wind speed >18m/s, wave height >4.3 m) -

Spill site current SC1 No current (hardly any dilution) +/- SC2 Low to 0.34 m/s (little dilution) +/- SC3 Medium 0.34 – 0.58 m/s (medium dilution) +/- SC4 High >0.58 m/s (large dilution) -

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Monitoring and leave to natural processes R6


Always monitoring needed Models are very helpful No need to recover sheens IR images are very helpful Description/aim Leave the oil to dissipate naturally. It is the only option when no active option can be applied, but can also be applied when it has good prospects. At the right combination of oil type, location and natural conditions the slick will dissipate without human intervention. This approach is normally applicable to smaller slicks of lighter oils. It needs constant monitoring. The advantages of natural dissipation are

• Low costs The disadvantages of natural dissipation are

• Leaves oil in the marine environment • Perception by the public • Costs of monitoring

Capacity The capacity of the natural dissipation mainly depends on the sea state. The more turbulent the water surface is, the faster the oil will disappear into the water column and finally biodegrade. The time needed before the oil slick will disappear from the water surface, can be predicted with computer models, which include wind force, wave height, temperature, type of oil, etc. Cost The costs are mainly determined by the fly hours of the plane used for monitoring. Conclusion The monitoring and leave to natural processes option can be applied as first line of defence in case of small spillages of light, volatile oils up to 1m3 with a low layer thickness. Preferably in open sea with a sea state higher than 3 and medium to strong currents in order to have appropriate dilution.


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Description Monitoring Spill volume

SV1 Very small spills (<0.1 m3) ++ SV2 Small spills (0.1 – 1 m3) ++ SV3 Medium spills (1 – 10 m3) + SV4 Large spills (10 – 100 m3) +/- SV5 Very large spills (100-1,000 m3) - SV6 Huge spills (>1,000 m3) -

Spill thickness ST1 <0.01 mm ++ ST2 0.01-0.1 mm ++ ST3 0.1-1.0 mm +/- ST4 1.0-10.0 mm - ST5 10.0-100.0 mm - ST6 >100.0 mm -

Physical form SP1 Sheen ++ SP2 Fragmented oil (coverage < 1%) - SP3 Patches - SP4 Ribbons (length>>>width) +/- SP5 Slicks +/- SP6 Submerged oil -

Spill oil type SO1 Light volatile products ++ SO2 Moderate to heavy oils + SO3 Heavy oils +/- SO4 Residual oil -

Spill location SL1 Open sea ++ SL2 Coastal area + SL3 Partially enclosed water body - SL4 Estuaries + SL5 Lakes - SL6 Rivers (strong current/velocity) + SL7 Canals (no-low current/velocity) - SL8 Harbour sheltered port area - SL9 Port area to open sea +/-

Spill weather/sea state SW1 Sea state 1 (wind speed 0 – 2 m/s, wave height 0 – 0.4 m) +/- SW2 Sea state 2 (wind speed 2 – 7 m/s, wave height 0.4- 1.7 m) +/- SW3 Sea state 3 (wind speed 7 – 12 m/s, wave height 1.7 – 3.0 m) + SW4 Sea state 4 (wind speed 12 – 18 m/s, wave height 3.7 – 4.3 m) ++ SW5 Sea state 5 (wind speed >18m/s, wave height >4.3 m) ++

Spill site current SC1 No current (hardly any dilution) +/- SC2 Low to 0.34 m/s (little dilution) +/- SC3 Medium 0.34 – 0.58 m/s (medium dilution) + SC4 High >0.58 m/s (large dilution) ++

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Sorbents R7

Sorbents R7

Adsorption boom Adsorption booms with skirt Various sorbents Loose material sorbents Description/aim The purpose of using sorbents for treating oil spills, is to enhance the removal of oil form water surface, land surface, beach, objects and equipment. Sorbents can be used to recover oil through the mechanism of absorption, adsorption or both. Absorbents allow oil to penetrate into pores in the material they are made of, while adsorbents attract oil to their surfaces but the oil does not penetrate into the material. Oil in absorbents cannot be squeezed out or leak out of the absorbent, while the oil can be squeezed or leak out when attached to adsorbents. Absorbents can be divided into three basic categories: natural organic sorbents (i.e. peat moss, straw, hay, etc.), inorganic sorbents (clay, perlite, glass, wool, etc.) and synthetic sorbents (polyurethane, polyethylene, nylon fibres, etc.). Only a few products meet the definition of a true absorbent. Sorbents are available in various types (mats, booms, loose material, pillows, etc.) and sizes. The advantages of sorbents are:

• Creates a physical barrier around the leading edge and immobilizes small amounts of free oil that cannot be removed from inaccessible sites

• Sorbent mats are designed to be deployed in any situation where covering of the surface of a body of water is desirable

• Natural products are generally available • Synthetic sorbents have high absorbing capacity for oil as well as chemicals • Synthetic sorbents are less sensitive for mechanical forces

The disadvantages of sorbents are:

• After removal leaking oil • Not all synthetic sorbents are biological degradable • Waste disposal

Capacity Depends on the type of sorbent that is used. Sorbents can absorb 5 to 20 times their own weight. Some organic sorbents take up more water and take up relatively less oil than synthetic sorbents. Costs Costs depend on the types of sorbent in relation to their capacity. Organic products are relatively cheap. Synthetic sorbents are more expensive. Conclusion Sorbents are normally used to recover smaller amounts of liquid oil. Sorbents are often used as a barrier to concentrate the oil and at the same time to recover the oil by sorption. Some sorbents are designed for light oil to moderate oil. Each product has its own specification and window of opportunity which types of oil it can absorb.


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Sorbents R7


Sorbents

SV1 Very small spills (<0.1 m3) ++ SV2 Small spills (0.1 – 1 m3) ++ SV3 Medium spills (1 – 10 m3) +/- SV4 Large spills (10 – 100 m3) +/- SV5 Very large spills (100-1,000 m3) - SV6 Huge spills (>1,000 m3) -

Spill thickness ST1 <0.01 mm ++ ST2 0.01-0.1 mm ++ ST3 0.1-1.0 mm +/- ST4 1.0-10.0 mm +/- ST5 10.0-100.0 mm - ST6 >100.0 mm -

Physical form SP1 Sheen ++ SP2 Fragmented oil (coverage < 1%) -- SP3 Patches -- SP4 Ribbons (length>>>width) ++ SP5 Slicks ++ SP6 Submerged oil -

Spill oil type SO1 Light volatile products ++ SO2 Moderate to heavy oils ++ SO3 Heavy oils - SO4 Residual oil --

Spill location SL1 Open sea - SL2 Coastal area +/- SL3 Estuaries + SL4 Partially enclosed water body + SL5 Lakes ++ SL6 Rivers (strong current/velocity) +/- SL7 Canals (no-low current/velocity) ++ SL8 Harbour sheltered port area ++ SL9 Port area to open sea +/-

Spill weather SW1 Sea state 1 (wind speed 0 – 2 m/s, wave height 0 – 0.4 m) ++ SW2 Sea state 2 (wind speed 2 – 7 m/s, wave height 0.4- 1.7 m) + SW3 Sea state 3 (wind speed 7 – 12 m/s, wave height 1.7 – 3.0 m) +/- SW4 Sea state 4 (wind speed 12 – 18 m/s, wave height 3.7 – 4.3 m) -- SW5 Sea state 5 (wind speed >18m/s, wave height >4.3 m) -

Spill site current SC1 No current (hardly any dilution) ++ SC2 Low to 0.34 m/s (little dilution) ++ SC3 Medium 0.34 – 0.58 m/s (medium dilution) +/- SC4 High >0.58 m/s (large dilution) -

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Shoreline cleanup (let the pollutant wash ashore) R8


Coastline best barrier Tar balls easy to clean-up Hand tools Manual/mechanical cleanup Description/aim The response option “shoreline cleanup” (let the pollutant wash ashore) is an option for spills of heavy viscous oils. This option should certainly be considered, as the other response options are often ineffective in the case of heavy and/or submerged oil. Case histories show, that floating/ submerged heavy (fuel) oils are very persistent and will in most cases wash ashore sooner or later. Two concepts are relevant with respect to “shoreline cleanup”. (1) possibility of moving a damaged vessel closer to the shore so that, if the heavy persistent oil will be released and comes to shore, it will impact a shorter length of coastline, and (2) if heavy persistent oil is spilled offshore it may be better not to take the ineffective options of trying to recover or treat it at sea, but rather let it come ashore where it can be dealt with in a more cost-effective manner. Optimisation of the first concept of shore line clean up means that a tanker should be brought to a favourable place as close as possible to the coastline where in case of leakage the oil will wash ashore fast without risking spreading out at sea. It is advised to let the oil wash ashore under controlled conditions. This is possible with a damaged tanker still containing and leaking heavy oil. When oil slicks are drifting towards the coast, the shoreline functions as barrier and floating oil will be concentrated on the flood line. The concentrated oil can be recovered from the shoreline. When mangrove swamps and certain wetlands are present, it would be a priority to prevent shoreline cleanup, because this can result in a major damage to these ecosystems. In these cases, it would be a priority to attempt to prevent the oil from impacting the shoreline, i.e. using deflective booms to direct oil to sacrificial areas. The second concept of shoreline clean up may be intrinsically quite damaging to the area and shoreline and the benefits of cleaning an area must be balanced carefully against the drawbacks of damage caused by the cleanup. Natural dissipation, dispersion, containment and recovery, flushing, absorption and mechanical or manual clearance are all viable techniques. The choice of methods will depend on the type of shoreline. Each of these options has its own problems. The main problem with shoreline cleanup, which also applies to the recovery and the use of adsorbents, is the disposal of the recovered material. In some areas this will be the most difficult part of the operation. Sometimes it may be possible to reduce the amount of material to be disposed off by washing it and returning cleaned material to the beach. When the oil has to come ashore, the options available and the associated problems are quite different. The approach to consider, "let the oil wash ashore", firstly needs preparation in the form of coastal sensitivity mapping. What are favourable places to let the oil wash ashore, knowing that the heavy viscous oil has to be recovered from the shoreline effectively and as fast as possible to prevent further pollution. This should be done during contingency planning and reconfirmed at the start of the cleanup operation. The second, and probably the most difficult part is the decision making process in getting permission from a municipality to bring a leaking tanker closer to their coast line. This needs to be clearly worked out in advance. The advantages of shoreline clean up are:

• Hard sandy beaches can be cleaned mechanically • Can be used at all wind forces • Oil concentrates on coast line

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The disadvantages of shoreline clean up are: • Access sometimes difficult • High costs to clean shoreline • Disposal of collected material often difficult • Some shorelines can not be cleaned at all without destroying their resource value • Waste treatment is costly

Capacity Depends on accessibility of the coastline, type of oil and many other factors such as, concentration, type of shoreline, degree of burying, etc. Costs The costs associated with shoreline clean up involve the standing charge of maintaining specialist equipment on stand-by (though most of the equipment used will be standard civil engineering equipment and will not need to be kept on stand-by) and the cost of deploying manpower and equipment. In addition, there will be costs associated with the disposal of oily wastes. The costs for clean up will vary considerably depending on the nature of the coastline and type of pollution, from a few hundred Euro/m3 to several thousand Euro/m3 oil recovered. At the time of the clean-up operation, the costs will depend on the nature of the coastline and the type of response selected. However, as indicated above, the type of coastline will be the main factor in selecting the response technique. Guidance from the air will be needed to evaluate the results. Conclusion The efficiency of the recovery operation depends heavily on the type of coastline, the oil concentration, the accessibility of the area and the properties of the oil. For each type of oil another clean-up techniques should be used. The shoreline cleanup option is in particular a response option to be considered in the case of very viscous/solid oils or floating/ submerged heavy fuel oil, which cannot be treated efficiently with chemicals and also when the chance of mechanical recovery is limited. Two concepts are relevant for shoreline cleanup. Damaged ships that still have heavy (fuel) oils on board should, in some cases, be brought as close to shore as possible. This will result in a shorter length of coastline polluted in case of a leakage. To optimise this response option, one should try to let the oil wash ashore under controlled conditions and select a landing site (beach) that can easily be cleaned. The option of bringing (towing) a ship in distress to the coastline with the objective to keep the possible treated area limited appears to be difficult. Rate of success is depending on political decisions and the capability of available vessels to tow the ship in the direction of the selected coastal area. The second option is to recover oil from the shoreline under certain circumstances. It depends on the coastline type – for example, heavy oil in a mangrove swamp or certain wetlands can be a major problem to cleanup and can result in major environmental damage. Mechanical recovery is less effective for heavy oils in particular when such oil slicks are scattered over a large area or are submerged. Factors that need to be considered in the decision-making process are economic, environmental and political. The decision-making process for both options is highly complex and may be subject to more detailed risk assessment, investigation and implementation in Net Environmental – Economical Benefit Analysis tools. Sensitivity ranking of the coastline is in this respect a very important preparative aspect.


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Sorbents

SV1 Very small spills (<0.1 m3) +/- SV2 Small spills (0.1 – 1 m3) +/- SV3 Medium spills (1 – 10 m3) +/- SV4 Large spills (10 – 100 m3) +/- SV5 Very large spills (100-1,000 m3) +/- SV6 Huge spills (>1,000 m3) +/-

Spill thickness ST1 <0.01 mm +/- ST2 0.01-0.1 mm +/- ST3 0.1-1.0 mm +/- ST4 1.0-10.0 mm +/- ST5 10.0-100.0 mm +/- ST6 >100.0 mm +/-

Physical form SP1 Sheen +/- SP2 Fragmented oil (coverage < 1%) +/- SP3 Patches +/- SP4 Ribbons (length>>>width) +/- SP5 Slicks +/- SP6 Submerged oil

Spill oil type SO1 Light volatile products +/- SO2 Moderate to heavy oils +/- SO3 Heavy oils +/- SO4 Residual oil +/-

Spill location SL1 Open sea +/- SL2 Coastal area +/- SL3 Estuaries +/- SL4 Partially enclosed water body +/- SL5 Lakes +/- SL6 Rivers (strong current/velocity) +/- SL7 Canals (no-low current/velocity) +/- SL8 Harbour sheltered port area +/- SL9 Port area to open sea +/-

Spill weather SW1 Sea state 1 (wind speed 0 – 2 m/s, wave height 0 – 0.4 m) +/- SW2 Sea state 2 (wind speed 2 – 7 m/s, wave height 0.4- 1.7 m) +/- SW3 Sea state 3 (wind speed 7 – 12 m/s, wave height 1.7 – 3.0 m) +/- SW4 Sea state 4 (wind speed 12 – 18 m/s, wave height 3.7 – 4.3 m) +/- SW5 Sea state 5 (wind speed >18m/s, wave height >4.3 m) +/-

Spill site current SC1 No current (hardly any dilution) +/- SC2 Low to 0.34 m/s (little dilution) +/- SC3 Medium 0.34 – 0.58 m/s (medium dilution) +/- SC4 High >0.58 m/s (large dilution) +/-

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Spill scenarios Group S

Spill scenarios Group S Response strategies are often focussed on large spills due to accidents with tankers or platforms. In case of such accidents large amounts of oil could escape into the sea. Such large spills are ‘however, rare. Operational spillages on the other hand happen quite often and are mostly very small. There are several decisions, which must be made when responding to oil spillages. During the initial stage of a spill the seriousness of the pollution must be analysed to assess the treat to humans, human-properties, coastal amenity and the aquatic environment. The need for immediate action to prevent or reduce further damage must be considered. In addition the costs of responding to a spill must be taken into account as well. The correctness of the decisions taken by the responsible authorities can significantly affect the outcome of the response action(s) and also the public opinion about the efficiency of the responsible authorities. This underlines the importance of preplanning to support decision-making when dealing with various spill scenarios. Such preplanning must be applicable to a wide range of spills and should be discussed and agreed upon with all parties involved. The following group S fiches covers designated types of spill situations/scenarios that determine the most suitable response. Spill volume scenarios (SV1 to SV6)

SV1. Very small spills (< 0.1 m3) SV2. Small spills (0.1 – 1 m3) SV3. Medium spills (1 – 10 m3) SV4. Large spills (10 – 100 m3) SV5. Very large spills (100 – 1000 m3) SV6. Huge spills (> 1000 m3)

Spill layer thickness scenarios (ST1 to ST6)

ST1. <0.01 mm ST2. 0.01- 0.1 mm ST3. 0.1– 1 mm ST4. 1 – 10 mm ST5. 10 – 100 mm ST6. >100 mm

Spill physical form scenarios (SP1 to SP6)

SP1. Sheen SP2. Fragmented oil (coverage < 1%) SP3. Patches (lumps > 1 m2) SP4. Ribbons (length >>> width) SP5. Slicks (high oil coverage) SP6. Submerged oil

Spill oil type (SO1 to SO4)

SO1. Light volatile products SO2. Moderate to heavy oils SO3. Heavy oil and emulsions SO4. Residual oil and solid emulsions

Spill locations (SL1 to SL9)

SL1. Open sea SL2. Coastal area SL3. Estuaries SL4. Partially enclosed water body SL5. Lakes

41

Spill scenarios Group S

SL6. Rivers (strong current/velocity) SL7. Canals (non-low current/velocity) SL8. Harbour sheltered port area SL9. Port area to open sea

Spill weather scenarios (SW1 to SW5)

SW1. Sea state 1, (wind force 0-2) SW2. Sea state 2, (wind force 2-4) SW3. Sea state 3, (wind force 4-6) SW4. Sea state 4, (wind force 6-8) SW5. Sea state 5, (wind force >8)

Spill current (SC1 to SC4)

SC1. No current SC2. Low current (<0.34 m/s) SC3. Medium current (0.34 – 0.58 m/s) SC4. Strong current (>0.58 m/s)

Use of the S fiches The first step is to gather as much information as possible from the spill (spill scenario information as shown above). Any spill is a combination of different S fiches; the more criteria known, the better the optimal response option can be chosen. The tables in the S fiches show the technical feasibility of the different response options mentioned in the R fiches, A distinction has been made in the following feasibility descriptions:

Feasibility description Feasibility score Will be effective ++ 3 Moderately effective + 2 May be feasible, depending on circumstances +/- 1 Ineffective or no practical application - 0 Counter productive -- 0

A computer program has been developed to show the results (feasible response options) of complicated scenario’s. The following 7 criteria together form a spill scenario.

1. Volume scenario’s SV1 to SV6 2. Layer thickness ST1 to ST6 3. Physical form scenarios SP1 to SP6 4. Oil type scenarios SO1 to SO4 5. Location scenarios SL1 to SL9 6. Weather/sea state scenarios SW1 to SW5 7. Current SC1 to SC4

The scores can be found in the tables of the corresponding S fiches. For instance wind force 6 can be looked up on S fiche SW4. This fiche shows the technical feasibility of each response option at wind force 6. The computer model uses per response option the product of the scores of each criteria, thus any score 0 will result in a final score of 0. A final score of 0 means that for such a scenario this response option is ineffective, or has no practical application, or could even be counter productive. The higher the score the more feasible the response option will be. However, any score above 0 result in an option that needs to be considered. In case a criteria is unknown a score of 1 will be applied.

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Spill volume SV

Spill volume SV Spill volume scenarios (SV1 to SV6) The following spilled oil volume scenarios can be distinguished:

SV1. Very small spills < 0.1 m3 SV2. Small spills 0.1 – 1 m3 SV3. Medium spills 1– 10 m3 SV4. Large spills 10 – 100 m3 SV5. Very large spills 100 – 1000 m3 SV6. Huge spills > 1000 m3

SV1 Very small spill SV2 Small spill

SV3 Medium spill SV4 Large spill

SV5 Very large spill SV6 Huge spill (Amoco Cadiz)


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Very small spills SV 1

Very small spills SV 1

Definition: Fiche no. Classification Volume spilled (m3) Layer thickness Coverage SV1 Very small spills < 0.1 Thin Low

Scenario definition Volume of spilled oil < 0.1 m3, mainly operational spills. Thin layer thickness or very low coverage of oil. Behaviour aspects Depending on the type of oil, these volumes of spilled oil will normally disappear from the water surface rapidly. SO types 1 and 2 in less than one hour to a couple of hours, SO types 3 and 4 in half a day to weeks. Effects if no response takes place Due to natural dispersion and evaporation SO 1 and 2 oil types will disappear from the water surface within hours;. SO 3 and 4 will remain on the water surface for a longer period of time. The effect of such spillages depends on the retention time of the oil slick on the water surface and the exposure to wildlife. Due to the natural dispersion some oil will enter the water column. However, this will result in very low oil concentrations in the water column. In deep-water (several meters) effects to water organisms are not likely to happen. Response Very small spillages are hardly operationally combatable, because their residence time on the water surface is shorter than the mobilisation time of the equipment. The combat ability increases with higher SO types. Response options for very small spills Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems - 0

Dynamic net systems - 0

R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) +/- 1 Endless rope +/- 1 Conveyor belt - 0 Weir +/- 1 Brush - 0 Drum, grabber - 1 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel +/- 1 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3 R7 Sorbents ++ 3 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1


44

Small spills SV 2

Small spills SV 2

Definition: Fiche no. Classification Volume spilled (m3) Layer thickness Coverage SV2 Small spills 0.1 – 1 Thin Low

Scenario definition Volume of spilled oil 0.1 to 1.0 m3, mainly operational spills. Thin layer thickness or low coverage of oil. Behaviour aspects Depending on the type of oil, these volumes of spilled oil will normally disappear from the water surface in short time. SO types 1 and 2 in less than one hour to a couple of hours, SO types 3 and 4 in half a day to weeks. Effects if no response takes place Due to natural dispersion and evaporation SO 1 and 2 oil types will disappear from the water surface within hours; SO 3 and 4 will remain on the water surface for a longer period of time. The effect of such spillages depends on the retention time of the oil slick on the water surface and the exposure to wildlife. Due to the natural dispersion some oil will enter the water column. However, this will result in very low oil concentrations in the water column. In deep-water (several meters) effects to water organisms are not likely to happen. Response Small spillages are usually not operationally combatable, because their residence time on the water surface is shorter than the mobilisation time of the equipment. The combat ability increases with higher SO types Response options for small spills Technical

feasible Score


Dynamic net systems +/- 1

R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) + 2 Endless rope + 2 Conveyor belt + 2 Weir + 2 Brush + 2 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft - 0 Large aircraft - 0 Vessel +/- 1 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3

R7 Sorbents ++ 3 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1


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Medium spills SV3

Medium spills SV3

Definition: Fiche no. Classification Volume spilled (m3) Layer thickness Coverage SV3 Medium spills 1– 10 Thin- medium medium

Scenario definition Volume of spilled oil 1.0 to 10 m3, mainly accidental spills. Behaviour aspects Depending on the type of oil, these volumes of spilled oil will normally disappear from the water surface rapidly. SO types 1 and 2 in less than one hour to a couple of hours, SO types 3 and 4 in half a day to weeks. Effects if no response takes place Due to natural dispersion and evaporation SO1 and SO2 oil types will disappear from the water surface within hours. SO3 and SO4 will remain on the water surface for a longer period of time. The effect of such spillages depends on the retention time of the oil slick on the water surface and the exposure to wildlife: with this volume some limited effects can be expected. Due to the natural dispersion some oil will enter the water column. This will result in low oil concentrations in the water column. In deep-water (several meters) severe effects to water organisms are not likely to happen. Response Medium spillages are usually not operationally combatable, because their residence time on the water surface is shorter than the mobilisation time of the equipment. However, if mobilization time is low this volume of oil can be operational combatable (Depending on oil type). Response options for medium spills Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems +/- 1 Dynamic net systems ++ 3 R2 Mechanical recovery using static systems Vacuum + 2 Disk, drum (oleophilic) + 2 Endless rope + 2 Conveyor belt + 2 Weir + 2 Brush + 2 Drum, grabber + 2 R3 Use of dispersants by spraying Small aircraft ++ 3 Medium aircraft ++ 3 Large aircraft - 0 Vessel + 2 Hand held + 2 R4 Mechanical dispersing the oil Any vessel + 2 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion + 2 R7 Sorbents +/- 1 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1


46

Large spills SV4

Large spills SV4

Definition: Fiche no. Classification Volume spilled (m3) Layer thickness Coverage SV4 Large 10 – 100 Medium Medium-large

Scenario definition Volume of spilled oil 10 to 100 m3; accidental spills. Behaviour aspects Depending on the type of oil, these volumes of spilled oil will normally disappear from the water surface by evaporation and dispersion. Depending on the turbulence at the water surface, light oils (SO1 and SO2) will disappear from the water surface in less than a day by evaporation and natural dispersion. The heavier oils (SO3 and SO4) will persist on the water surface for a longer time less than 8 hours to several days on calm water surfaces. Effects if no response takes place Approximately 50-60% of volatile to moderate oils (SO1 and SO2) will evaporate; the remaining oil will be naturally dispersed. Approximately 0-40% heavy to residual oil (SO3 and SO4) will evaporate, while hardly any dispersion occurs. The effect of this spill volume depends on the retention time of the oil slick on the water surface and the exposure to wildlife; effects can be expected. Due to the natural dispersion some oil will enter the water column, which will result in low oil concentrations in the water column. In deepwater (several meters) serious effects to water organisms are not likely to happen. Response Large spills are usually operationally combatable. Such spills stay on the water surface long enough to make mobilisation of response equipment possible. Technically, most response options are feasible to deal with this spill volume as is shown in the table below. Response options for large spills Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems ++ 3 Dynamic net systems +/- 1 R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush + 2 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft ++ 3 Medium aircraft ++ 3 Large aircraft + 2 Vessel + 2 Hand held +/- 1 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion +/- 1

R7 Sorbents +/- 1 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1


47

Very large spills SV 5

Very large spills SV 5

Definition: Fiche no. Classification Volume spilled (m3) Layer thickness Coverage SV5 Very large 100 – 1,000 Large Large

Scenario definition Volume of spilled oil 100 to 1,000 m3, accidental spills. Behaviour aspects Light oils (SO1 and SO2) may disappear from the water surface by evaporation and natural dispersion when mixing energy is high (rough weather). Normally this size of spill remains longer on the water surface and part of it will wash ashore. SO3 and SO4 oil types will stay on the water surface and only a small part will naturally disperse. Effects if no response takes place The effect of this spill volume depends on the retention time of the oil slick on the water surface and the exposure to wildlife; major effects can be expected. Due to natural dispersion oil will enter the water column, which will result in medium oil concentrations in the water column. Even in deep-water (several meters) some effects to water organisms can be expected. Depending on conditions (wind and currents), part of the oil may wash ashore and affect coastal activities (recreation, mariculture). Response Very large spills are operationally combatable at sea. Such spills stay on the water surface, which makes mobilisation of response equipment possible. Technically, most response options are feasible to deal with this spill volume. Response options for very large spills Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems ++ 3


R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel + 2 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion - 0

R7 Sorbents - 0 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1


48

Huge spills SV 6

Huge spills SV 6

Definition: Fiche no. Classification Volume spilled (m3) Layer thickness Coverage SV6 Huge > 1,000 Very large Very large

Scenario definition Volume of spilled oil > 1,000 m3; accidental spills. Behaviour aspects Light oils (SO1 and SO2) may disappear from the water surface by evaporation and natural dispersion when mixing energy is high (rough weather). Normally this size of spill remains longer on the water surface and part of it will wash ashore. SO3 and SO4 oil types will stay on the water surface and only a small part will naturally disperse. Effects if no response takes place The effect of this spill volume depends on the retention time of the oil slick on the water surface and the exposure to wildlife; major effects can be expected. Due to natural dispersion large quantities of oil will enter the water column. This can result in, lethal oil concentrations in the water column. In deep-water effects to water organisms are less than in shallow waters. Onshore-directed winds will transport the remaining oil to shore where long lengths of coastline can be polluted. Response Huge spills volume is operationally combatable at sea. Despite all efforts at sea, this spill volume often needs to be treated on the coast as well. Technically, most response options are feasible to deal with huge spills, but few are really effective, most times more response options should be deployed. Response options for huge spills Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) +/- 1 Endless rope +/- 1 Conveyor belt ++ 3 Weir +/- 1 Brush +/- 1 Drum, grabber +/- 1 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel + 2 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion - 0


49

Spill layer thickness ST

Spill layer thickness ST Spill layer thickness scenarios (ST1 to ST6)

ST1. <0.01 mm ST2. 0.01- 0.1 mm ST3. 0.1– 1 mm ST4. 1.0 – 10 mm ST5. 10 – 100 mm ST6. >100 mm

ST1 <0.01 mm ST2 0.01- 0.1 mm

ST3 0.1– 1 mm ST4 1.0 – 10 mm

ST5 10 – 100 mm ST6 >100 mm


50

Spill layer thickness <0.01 mm ST1

Spill layer thickness <0.01 mm ST1 Definition:

Fiche no. Classification Layer thickness (mm) Volume/area ST1 Film -Very light < 0.01 <10m3/km2

Scenario definition Very light oil spill. Thin layer of oil, often representing sheen/rainbow colours. In many cases due to operational spillages. Behaviour aspects Depending on the type of oil, this layer thickens of spilled oil will normally disappear from the water surface rapidly. SO types 1 and 2 in less than one hour to a couple of hours, SO types 3 and 4 in half a day to weeks. Effects if no response takes place Due to natural dispersion and evaporation SO 1 and 2 oil types will disappear from the water surface within hours;. SO3 and 4 will remain on the water surface for a longer period of time. The effect of such spillages depends on the retention time of the oil slick on the water surface and the exposure to wildlife. Due to the natural dispersion some oil will enter the water column. However, this will result in very low oil concentrations in the water column. In deep-water (several meters) effects to water organisms are not likely to happen. Response Spillages with a layer thickness <0.01 mm are hardly operationally combatable, because their residence time on the water surface is shorter than the mobilisation time of the equipment. The combat ability increases with higher SO types. Response options for spills with a layer thickness <0.01 mm Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) +/- 1 Endless rope +/- 1 Conveyor belt - 0 Weir - 0 Brush - 0 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel + 2 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3



51

Spill layer thickness 0.01- 0.1 mm ST2

Spill layer thickness 0.01- 0.1 mm ST2

Definition: Fiche no. Classification Layer thickness (mm) Volume/area ST2 Light 0.01-0.1 10 - 100 m3/km2 Scenario definition Light oil spill. Layer thickness of spilled oil 0.01 to 0.1 mm, mainly operational spills. Behaviour aspects Depending on the type of oil, this layer thickness of spilled oil will normally disappear from the water surface rapidly. SO types 1 and 2 in less than one hour to a couple of hours, SO types 3 and 4 in half a day to weeks. Effects if no response takes place Due to natural dispersion and evaporation SO 1 and 2 oil types will disappear from the water surface within hours; SO 3 and 4 will remain on the water surface for a longer period of time. The effect of such spillages depends on the retention time of the oil slick on the water surface and the exposure to wildlife. Due to the natural dispersion some oil will enter the water column. However, this will result in very low oil concentrations in the water column. In deep-water (several meters) effects to water organisms are not likely to happen. Response Spillages with a layer thickness between 0.01 and 0.1 mm are usually not operationally combatable, because their residence time on the water surface is shorter than the mobilisation time of the equipment. The combat ability increases with higher SO types Response options for spills with an layer thickness between 0.01 -0.1 mm Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems +/- 1


R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt +/- 1 Weir +/- 1 Brush +/- 1 Drum, grabber +/- 1 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel +/- 1 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel + 2 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3



52

Spill layer thickness 0.1-1 mm ST3

Spill layer thickness 0.1-1 mm ST3

Definition: Fiche no. Classification Layer thickness (mm) Volume/area ST3 Moderate 0.1-1 100 - 1000 m3/km2

Scenario definition Moderate oil spill. Layer thickness of spilled oil 0.1 to 1.0 mm, mainly accidental spills. Behaviour aspects Depending on the type of oil, this layer thickness of spilled oil will normally disappear from the water surface rapidly SO types 1 and 2 in less than one hour to a couple of hours, SO types 3 and 4 in half a day to weeks. Effects if no response takes place Spillages with a layer thickness between 0.1 and 1 mm will remain on the water surface for a longer period of time. The effect of such spillages depends on the retention time of the oil slick on the water surface and the exposure to wildlife: with this layer thickness effects can be expected. Due to the natural dispersion some oil will enter the water column. This may result in low oil concentrations in the water column. In deep water (several meters) severe effects to water organisms are not likely to happen. Response Spillages with a layer thickness between 0.1 and 1 mm are usually operationally combatable because these spillages remain on the water surface for a longer period of time. Technically, most response options are feasible to deal with above mentioned layer thickness of oil. Response options for spills with a layer thickness between 0.1 and 1 mm Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) + 2 Endless rope + 2 Conveyor belt + 2 Weir + 2 Brush + 2 Drum, grabber + 2 R3 Use of dispersants by spraying Small aircraft ++ 3 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel ++ 3 Hand held +/- 1 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion +/- 1



53

Spill layer thickness 1-10 mm ST4


Definition: Fiche no. Classification Layer thickness (mm) Volume/area ST4 Heavy 1-10 1,000 – 10,000 m3/km2

Scenario definition Heavy oil spill. Layer thickness of spilled oil 1 to 10 mm Behaviour aspects Light oils (SO1 and SO2) spillages with a layer thickness of 1 to 10 mm may disappear from the water surface by evaporation and natural dispersion when mixing energy is high (rough weather). Normally this layer thickness of oil remains longer on the water surface and part of it will wash ashore. SO3 and SO4 oil types will stay on the water surface, only a small part will naturally disperse. Effects if no response takes place The effect of this spill layer thickness depends on the retention time of the oil slick on the water surface and the exposure to wildlife; major effects can be expected. Due to natural dispersion oil will enter the water column, which will result in medium oil concentrations in the water column. Even in deep-water (several meters) some effects to water organisms can be expected. Depending on conditions (wind and currents), part of the oil may wash ashore and affect coastal activities (recreation, mariculture). Response Spillages with a layer thickness between 1 and 10 mm are usually operationally combatable because these spillages remain on the water surface for a longer period of time. Technically, most response options are feasible to deal with above mentioned spill layer thickness. Response options for spills with a layer thickness between 1 and 10 mm Technical

feasible Score


Dynamic net systems ++ 3

R2 Mechanical recovery using static systems Vacuum + 2 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush + 2 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft + 2 Medium aircraft + 2 Large aircraft + 2 Vessel + 2 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning ++ 3 R6 Monitoring and leave to natural dispersion - 0



54



Definition: Fiche no. Classification Layer thickness (mm) Volume/area ST5 Very heavy 10-100 10,000 – 100,000 m3/km2

Scenario definition Very heavy oil spill. Layer thickness of spilled oil 10 to 100 mm, accidental spills. Behaviour aspects Light oils (SO1 and SO2) may disappear from the water surface by evaporation and natural dispersion when mixing energy is high (rough weather). Normally this layer thickness remains longer on the water surface and large part of it will wash ashore. SO3 and SO4 oil types will stay on the water surface and only a small part will naturally disperse. Effects if no response takes place The effect of this oil layer thickness depends on the retention time of the oil slick on the water surface and the exposure to wildlife; major effects can be expected. Due to natural dispersion oil will enter the water column, which will result in medium oil concentrations in the water column. Even in deep-water (several meters) some effects to water organisms can be expected. Depending on conditions (wind and currents), large part of the oil may wash ashore and affect coastal activities (recreation, mariculture). Response Oil spills with a layer thickness between 10 and 100 mm are operationally combatable at sea. Such spills stay on the water surface, which makes mobilisation of response equipment possible. Technically, a number of response options is feasible to deal with oil spills with layer thickness range. Response options for spills with a layer thickness between 10 and 100 mm Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning ++ 3 R6 Monitoring and leave to natural dispersion - 0



55

Spill layer thickness >100 mm ST6

Spill layer thickness >100 mm ST6

Definition: Fiche no. Classification Layer thickness (mm) Volume/area ST6 Extremely heavy >100 > 100,000 m3/km2

Scenario definition Extremely heavy oil spill. Layer thickness of spilled oil > 100 mm; accidental spills of heavy oil, or concentrated oil in enclosed area. Behaviour aspects Normally this layer thickness remains longer on the water surface and large part of it will wash ashore. SO3 and SO4 oil types will stay on the water surface and only a very small part will naturally disperse. Effects if no response takes place The effect of this spill layer thickness depends on the retention time of the oil slick on the water surface and the exposure to wildlife; major effects can be expected. Due to natural dispersion large quantities of oil may enter the water column. This can result in, lethal oil concentrations in the water column. In deep-water effects to water organisms are less than in shallow waters. Onshore directed winds will transport the remaining oil to shore, where long lengths of coastline can be affected. Response Oil spill with a layer thickness in excess of 100 mm are operational combatable at sea. Despite all efforts at sea, this spill volume often needs to be treated on the coast as well. Technically, a number of response options is feasible to deal with these huge spills. Response options for spill with a layer thickness >100 mm Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning ++ 3 R6 Monitoring and leave to natural dispersion - 0


56

Spill physical form SP

Spill physical form SP Spill physical form scenarios (SP1 to SP6)

SP1. Sheen SP2. Fragmented oil (coverage < 1%) SP3. Patches (lumps > 1 m2) SP4. Ribbons (length >>> width) SP5. Slicks (high oil coverage) SP6. Submerged oil

SP1 Sheen SP2 Fragmented oil (coverage < 1%)

SP3 Patches (lumps > 1 m2) SP4 Ribbons (length >>> width)

SP5 Slicks (high oil coverage) SP6 Partly submerged oil


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Sheen SP 1

Sheen SP 1

Definition: Fiche no. Classification Viscosity Persistency Encounter SP1 Sheen Low-medium Very low Very low

Scenario definition The appearance colour of this spill type is a combination of grey silvery and rainbow sheen. These appearances represent a layer thickness up to 0.005 mm. The amount of oil may be as much as 5000 liters per km2. Behaviour aspects Sheens will normally disappear quickly from the water surface due to evaporation and natural dispersion. This may occur to be in less than one hour to a couple of hours (at calm water surfaces). Effects if no response take place Sheens will disappear from the water surface quickly. The effects of sheens depend on the retention time on the water surface and the exposure to wildlife. As ‘sheen’ appearance/colour represents a layer thickness less than the effect threshold layer thickness for wildlife (birds), no effects are expected. Due to the natural dispersion some oil will enter the water column. However, this will result in very low oil concentrations in the water column. Response Sheen spillages are normally not operationally combatable. Usually the residence time of the sheen is much less than the mobilization time of equipment. Due to the thin layer, the efficiency of combat is also low. Technically, only a few response options are feasible to deal with sheens. Response options for sheens Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt - 0 Weir - 0 Brush - 0 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3



58

Fragmented oil (coverage < 1%) SP 2

Fragmented oil (coverage < 1%) SP 2

Definition: Fiche no. Classification Viscosity Persistency Encounter SP2 Fragmented oil Very high/solid Very high Low

Scenario definition Fragmented oil, are small ‘semi’ solid lumps (diameter a few centimetre to several tens of centimetres) of very viscous to almost solid oil. These tar balls are normally scattered over a large area at sea with a low oil coverage percentage (< 1%). Tar balls are floating at, or just below, the water surface and are difficult to observe from the air. Behaviour aspects Fragmented oil is very persistent, weathered oil that will finally wash ashore or sink to the sea floor. When washed ashore this fragmented oil concentrates at the flood line and may pick up sediment. Effects if no response take place The physical form of fragmented oil is very persistent. When washed ashore tar balls concentrate at the flood line and, in case of sandy beaches, will be buried under the sand in time. When washed back to the sea, they will sink to the sea floor due to the increased density by picking up sediment from the coastline. Response The best way to treat fragmented oil to is let them concentrate first ashore or by the use of oil booms. Technically, only a few response options are feasible to deal with fragmented oil Response options for fragmented oil spills Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems + 2


R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt +/- 1 Weir +/- 1 Brush +/- 1 Drum, grabber +/- 1 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion - 0



59

Patches (lumps >1 m2) SP 3

Patches (lumps >1 m2) SP 3

Definition: Fiche no. Classification Viscosity Persistency Encounter SP3 Patches Very high/solid Very high Low to medium

Scenario definition Patches are large lumps (diameter a few metres to several tens of metres, > 1 m2) of very viscous to almost solid oil. Patches normally are scattered over a large area at sea, resulting in a low oil coverage percentage. Patches are floating almost submerged at the water surface and are difficult to observe from the air. Behaviour aspects Patches consist of very persistent, weathered oil that will finally wash ashore or sink to the sea floor. When washed ashore patches concentrate at the flood line and pick up sediment. Effects if no response take place Such type of oil spillages is very persistent. Oil patches may finally wash ashore, or sink to the sea floor. When washed ashore, patches concentrate at the flood line. Response The best way to recover patches at sea is to concentrate them first by the use of oil booms or recover the patches from the shoreline after they wash ashore. Technically a number of response options are feasible to deal with oil patches. Response option for oil patches Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion - 0



60

Ribbons SP4

Ribbons SP4

Definition: Fiche no. Classification Viscosity Persistency Encounter SP4 Ribbons Low -medium Low - medium Low

Scenario definition Ribbons are defined as oil slicks with a length - width ratio in excess of 10. Such spills could arise from continuous leakages and often have a relatively low coverage. Behaviour aspects Ribbons arise from various types of oil. Therefore, their behaviour depends on the type of oil and total quantity spilled. Effects if no response take place Ribbons will break up in windrows. Depending on oil type, the trail will disappear due to natural dispersion and evaporation (SO1 and 2) or form tar balls (SO3 and 4), which will finally wash ashore. Response Technically, there are several response options feasible to deal with ribbons. Response option for ribbons Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) + 2 Endless rope + 2 Conveyor belt + 2 Weir + 2 Brush - 0 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft ++ 3 Medium aircraft + 2 Large aircraft - 0 Vessel + 2 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion +/- 1



61

Slicks (homogeneous) SP 5

Slicks (homogeneous) SP 5

Definition: Fiche no. Classification Viscosity Persistency Encounter SP5 Slicks Variable Low -high High

Scenario definition In contrast with ribbons, slicks are characterized by a length -width ratio less than 10. Such spills arise from instantaneous leakages and result in a relatively large coverage. Behaviour aspects Slicks arise from various types of oil. Therefore, their behaviour depends on the type of oil and quantity spilled. Effects if no response take place Depending on oil type and spill size, slicks will disappear due to natural dispersion and evaporation (light to medium oils, SO1 and SO2) or form emulsions (heavy oils, SO3 and SO4), which may finally wash ashore. Response Technically, most response options are feasible. Response options for slicks Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft + 2 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel ++ 3 Hand held +/- 1 R4 Mechanical dispersing the oil Any vessel + 2 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion +/- 1



62

Submerged oil SP 6

Submerged oil SP 6

Definition: Fiche no. Classification Viscosity Persistency Encounter SP6 Submerged oil Very high Very high Low to medium

Scenario definition Submerged oils mostly high viscous heavy oils with a density almost equally to the water density. These oil types are difficult to observe from the air as they just flow underneath the water surface. Behaviour aspects Submerged oils do not evaporate anymore and are therefore very persistent. Submerged oils mostly are heavy oils (SO3 and SO4), which do not disperse naturally. Such oils may wash ashore and pick up sediment or sink to the sea floor. Effects if no response take place Submerged oil is very persistent. Submerged oil therefore will finally wash ashore, or sink to the sea floor. Response Technically only a few response options are feasible. Generally, however, it is difficult to treat submerged oil. Response option for submerged oils Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt - 0 Weir - 0 Brush - 0 Drum, grabber +/- 1 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion - 0


63

Spill oil types SO

Spill oil types SO Spill oil type (SO1 to SO4)

SO1. Light volatile products SO2. Moderate to heavy oils SO3. Heavy oil and emulsions SO4. Residual oil and solid emulsions

SO1 Light volatile products SO2 Moderate to heavy oils

SO3 Heavy oil and emulsions SO4 Residual oil and solid emulsions


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Light volatile products SO1

Light volatile products SO1

Definition: Fiche no. Classification Volatility Natural dispersion Stickiness SO1 Light volatile products Very high High Low

Scenario definition Light volatile oils are mostly light products such as petroleum spirit, gasoline, kerosene, automotive diesel, etc. This type of oil has a low viscosity, is not sticky and is non-persistent. Behaviour aspects Light volatile oils will evaporate completely and are also naturally dispersed easily. This type of oil will spread rapidly to form sheens. Many of these products are highly toxic and ,therefore, health and safety aspects must be considered. Effects if no response take place Light volatile products will disappear from the water surface in short time, due to high rates of evaporation and high dispersability. As dispersion is a function of volume spilled and turbulence of the water surface, the lifetime of such spillages on the water surface can approximately be predicted. Response Technically, a few response options are feasible. Response options for light volatile products Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) + 2 Endless rope + 2 Conveyor belt - 0 Weir + 2 Brush - 0 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3



65

Moderate to heavy oils SO2

Moderate to heavy oils SO2

Definition: Fiche no. Classification Volatility Natural dispersion Stickiness SO2 Moderate to heavy oils < 50% Moderate Slightly to moderately

Scenario definition Moderate to heavy oils are mostly crude oils and intermediate products such as marine diesel, gas oil, light fuel oil, light lubricating oil, etc. This type of oil is slightly to moderately sticky, persistent and low to moderately viscous. Behaviour aspects Up to 50% of moderate to heavy oils may evaporate, but it will disperse naturally only to a limited extent. This type of oil tends to form water-in-oil emulsions with limited spreading. Effects if no response take place In case of large spills, this type of oil tends to form water-in-oil emulsions. Small spills of this type of oil will disappear from the water surface due to evaporation and natural dispersion. As dispersion is a function of volume spilled and turbulence on the water surface, the lifetime of such spillages on the water surface can approximately be predicted. Response Technically, several response options are feasible. Response options for moderate to heavy oils Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt + 2 Weir ++ 3 Brush + 2 Drum, grabber +/- 1 R3 Use of dispersants by spraying Small aircraft ++ 3 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel ++ 3 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion + 2



66

Heavy oils and emulsions SO3

Heavy oils and emulsions SO3

Definition: Fiche no. Classification Volatility Natural dispersion Stickiness SO3 Heavy oils and emulsions <20 % Low Very sticky

Scenario definition Heavy oils and emulsions are characterized by high densities, typically in the range of 900–1020 kg/m³ at 15 °C, and by relatively high viscosities (5,000 to 30,000 cSt at 15ºC). Behaviour aspects When heavy oil comes ashore, it tends to become firmly attached to any solid surface. However, heavy viscous oil does not penetrate sandy beaches and usually can easily be removed. Effects if no response take place Heavy oils are very persistent and if not completely recovered at sea, can wash ashore after months, with major effects on the environment. Response Spills of persistent heavy (fuel) oils are among the most difficult to combat. Skimming devices are often not able to handle highly viscous or solidifying oils that may have floating debris incorporated. High density and low buoyancy further hamper recovery attempts at sea. Heavy fuel oil is often floating just below the water surface, which makes it difficult to see from the recovery vessels and greatly reduces the efficiency of mechanical recovery. Viscosity is of great importance in any action to deal with an oil slick, since it has a decisive influence on the pump capacity. It should also be realized that heavy (fuel) oil recovered into a storage tank, is very difficult to unload if there is no heating system in the tank to reduce the viscosity. Technically, a number of response options is feasible. Response options for heavy oils and emulsions Technical

feasible Score


Dynamic net systems + 2

R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) +/- 1 Endless rope +/- 1 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft +/- 1 Large aircraft +/- 1 Vessel +/- 1 Hand held +/- 1 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion +/- 1



67

Residual oils and solid emulsions SO4

Residual oils and solid emulsions SO4

Definition: Fiche no. Classification Volatility Natural dispersion Stickiness SO4 Residual oils and solid emulsions None None to very low Very sticky to solid

Scenario definition Residual oils and solid emulsions are mostly bunker and heavy fuel oils, or weathered crude oil in the form of tarry lumps, asphalt, etc. This type of oil is very sticky to semi solid. Behaviour aspects Residual oils and solid emulsions hardly will evaporate or disperse. These oils are very persistent. This type of oil does not spread out further. Weathered oil will form tarry lumps at low temperature, but when exposed to sun may become “fluid”. Effects if no response take place Due to it’s persistency, this type of oil will mostly wash ashore, or sink to the sea floor. Response The limitations of containing and recovering spilled residual oil and solid emulsions at sea are well known. Skimming devices and their appendages are often not able to handle these highly viscous or solidifying oils that often have floating debris incorporated. For this reason special skimmers (R2) are used in spills with this type of oil. High density and low buoyancy further hamper recovery attempts at sea. Heavy (fuel) oil is often floating just below the water surface, which makes it difficult to see from the recovery vessels and greatly reduces the efficiency of mechanical recovery. Viscosity is of great importance in any action to deal with an oil slick, since it has a decisive influence on the pump capacity. It should also be realized that heavy (fuel) oil recovered into a storage tank, is very difficult to unload if there is no heating system in the tank to reduce the viscosity. Technically, only a few response options are feasible. Response options for residual oils and solid emulsions Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems + 2


R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt ++ 3 Weir +/- 1 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion - 0


68

Spill locations SL

Spill locations SL Spill locations (SL1 to SL9) SL1. Open sea SL2. Coastal area SL3. Estuaries SL4. Partially enclosed water body SL5. Lakes

SL6. Rivers (strong current/velocity) SL7. Canals (non-low current/velocity) SL8. Harbours; (sheltered port area) SL9. Port; (area to open sea)

SL1 Open sea (Bravo Blow out) SL2 Coastal area

SL3 Estuaries SL4 Partially enclosed water body

SL5 Lakes SL6 Rivers (strong current/velocity)

SL7 Canals (non-low current/velocity) SL8/SL9 Harbour/Port


69

Open sea SL 1

Open sea SL 1

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL1 Open sea Medium/tide High High Low –medium

Scenario definition Open sea is defined as a large water surface at such a distance from any coastline that a spill in such a location allows sufficient time to respond before the oil can wash ashore. Open sea also means that the conditions on scene are representative for sea conditions in particular current/tide and wave heights. Behaviour aspects At sea, wind and currents will move the oil slick. Tide will change the current direction and velocity regularly. Normally, the residual current is parallel to the coastline and wind determines the movement towards the coastline. Effects if no response take place Depending on the type of oil and the weather conditions, oil will partially evaporate and disperse naturally at sea, or forms more persistent water-in-oil emulsion or tarry residue. The distance from the coastline in the wind direction determines the retention time at sea and the place where oil may wash ashore. As wind direction can change, a precise prediction is often difficult. Heavy oils, tarry lumps and water-in-oil emulsions are often submerged and are only transported by current and hardly by wind. Response Sea conditions are often rough and this plays an important role in the decision which equipment can be used. The response equipment needs to be sea worthy. Technically, most response options are feasible. Response options for open sea Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt + 2 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel ++ 3 Hand held - 0 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion ++ 3



70

Coastal area SL 2

Coastal area SL 2

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL2 Coastal area Medium High Medium/low High

Scenario definition Coastal area is defined as a large water surface at such a distance from the coastline that there is little time to respond before the oil can wash ashore. Coastal area also means that the conditions on scene are representative for open sea conditions, particularly current/tide and wave heights. Behaviour aspects Wind and currents will move the oil slick. Tide changes the current direction and velocity regularly. Normally, the residual current is parallel to the coastline and wind determines the movement towards the coastline. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate and disperse naturally, or forms a more persistent water-in-oil emulsion, or tarry residue. The distance from the coastline in the wind direction determines the retention time on the water surface and the location where oil washes ashore. As wind direction can change, a precise prediction is often difficult. Submerged oils are only transported by current and hardly by wind. Response Coastal area conditions are often rough. This is important with regard to the decision which equipment can be used. Water depth may be a limiting factor in coastal areas. Technically, a number of response options is feasible. Response option for coastal areas Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt + 2 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft + 2 Medium aircraft + 2 Large aircraft ++ 3 Vessel + 2 Hand held - 0 R4 Mechanical dispersing the oil Any vessel + 2 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion + 2



71

Partially enclosed water body SL 3

Partially enclosed water body SL 3

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL3 Partially enclosed Site specific Site specific Site specific High

Scenario definition A partially enclosed water body is a large water surface, with a surface area of a few square kilometres. A spill in such a location allows little time to respond before the oil can wash ashore. Examples of partially enclosed water bodies are fjords and bays. Each of these water bodies has its own characteristics. A single definition can, therefore not be defined. Behaviour aspects Depending wind direction oil spills in partially enclosed water body will remain in the enclosed area. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate. Only limited natural dispersion will take place a in an enclosed water body. Spills may form a more persistent water-in-oil emulsion or tarry residue. Because of, the high coastline to surface area ratio, an enclosed water body is highly vulnerable. Response Technically, feasible response options are limited to mechanical recovery and use of sorbents Response options for enclosed water bodies Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion - 0

R7 Sorbents + 2 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1


72

Estuaries SL 4

Estuaries SL 4

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL4 Estuaries Very high Medium-high Low/very low Very high

Scenario definition Estuaries are defined as semi-enclosed bodies of coastal water having a free connection with the open sea, in which the seawater is measurably diluted with fresh water derived from a river. Extensive sand- and mudflats, derived from marine and/or river-borne sediments, characterize many estuaries. Behaviour aspects In an estuary, wind and currents will move the oil slick. Tide changes the current direction and velocity continuously; the main current is for a seaward direction. Sand- and mudflats in combination with the tide often determine the destination of a spill. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate and disperse naturally, or forms a more persistent water-in-oil emulsion or tarry residue. Sand- and mudflats determines the retention time on the water surface and the place where oil wash ashore or will remain on the sand- and mudflats. Response Estuarine conditions are often rough (strong currents, turbulence) this plays an important role in the decision which equipment can be used. Another impotent aspect is the water depth (sand- and mudflats). Response ship(s) as well as response equipment need to be sea worthy in estuaries and should have a limited draft. Technically, several response options are feasible. Response options for estuaries Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft +/- 1 Large aircraft +/- 1 Vessel +/- 1 Hand held - 0 R4 Mechanical dispersing the oil Any vessel + 2 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion + 2



73

Lakes SL5

Lakes SL5

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL5 Lakes Low/medium Medium Medium/Low High

Scenario definition Lakes are defined as semi enclosed fresh water bodies, connected with other surface waters by channels or rivers. A spill in such a location allows little time to respond before the oil impacts the shores. Lake conditions are representative for large open waters: low to medium current, no tide and medium wave heights. Behaviour aspects In lakes, mainly wind will move the oil slick. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate and disperse naturally or forms a more persistent water-in-oil emulsion or tarry residue. Response Response ship(s) as well as response equipment do not need to be sea worthy in lakes, but should have a limited draft and, be usable in medium wave conditions. Due to the depth and the high sensitive (aqueous) environment dispersants cannot be used. Technically, mainly mechanical response options are feasible. Response options for lakes Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion - 0



74

Rivers (strong current/velocity) SL6

Rivers (strong current/velocity) SL6

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL6 Rivers High/very high Low Medium-Low High

Scenario definition Rivers are defined as narrow enclosed water bodies with high to very strong currents. Drainage characteristics may vary through the year. The relative approximate of opposing riverbanks allow for very limited time to respond before the oil or part of the oil impacts the banks. Specific conditions are: narrow water, high to very strong currents absence of tide and low wave heights. Behaviour aspects In rivers, the current will move the oil slick down stream. Local turbulence and wind may cause stranding of oil along the banks. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate and disperse naturally, or forms a more persistent water-in-oil emulsion or tarry residue. Due to the current and limited absorption capacity of the banks, banks may be polluted for considerable lengths. Response Response ships, as well as response equipment should have a limited draft and be usable in medium wave conditions. The most important aspect in rivers is the strong current, which is an limiting factor for adequate response. Technically, several response options are feasible. Response options for rivers Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft - 0 Large aircraft - 0 Vessel +/- 1 Hand held +/- 1 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion + 2



75

Canals SL 7

Canals SL 7

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL7 Canals Non/low Low Medium Medium

Scenario definition Canals are defined as (non natural, man made) narrow enclosed bodies of fresh water with no or low currents. Canals usually are much smaller than rivers, allowing for very limited time to respond before the oil, or part of the oil washes on the banks. Specific conditions for narrow waters in particular are the absence of strong currents and tides and low wave heights. Behaviour aspects In canals mainly wind will move the oil slick.. The wind direction determines which bank/shore line will be most affected. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate. Limited amounts will disperse naturally. As thet absorption capacity of the banks is limited, considerable length of bank may be polluted. Response Response ships, as well as response equipment should have limited draft. The most important aspect in canals is the shipping traffic, which is the limiting factor for adequate response. Technically, several mainly mechanical response options are feasible. Response options for canals Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion - 0



76

Harbour (sheltered port area) SL 8

Harbour (sheltered port area) SL 8

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL8 Harbour Non-low Low Medium-Low Low

Scenario definition Harbours (sheltered port areas) are defined as narrow enclosed water bodies with no or low currents. Sometimes tidal influence may be present. Harbours are narrow water surfaces at such a distance from banks that a spill in such a location allows very limited time to respond before the oil or part of the oil washes on the banks. Representative conditions are limited currents and low wave heights. Behaviour aspects In harbours mainly wind will move the oil slick. The wind direction determines which bank/shore line the oil will hit. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate. Limited amounts may disperse naturally. Due to wind and limited absorption capacity of the banks some length of bank could be polluted. Response Response ships should be small and manoeuvrable. Booms may be used to concentrate the spill and prevent spreading. Most important aspect in harbours is the shipping traffic, which is the limiting factor for adequate response. Technically, several response options are feasible. Response options for harbours Technical

feasible Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems +/- 1


R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel +/- 1 Hand held + 2 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion - 0



77

Port (area to open sea) SL 9

Port (area to open sea) SL 9

Definition: Fiche no. Classification Current Waves Water depth Vulnerability SL9 Port Medium Medium - high Medium-deep Low

Scenario definition Ports (area to open sea) are defined as open water with currents and tide. Conditions on scene are representative for coastal waters, in particular with respect to current and wave heights. Behaviour aspects In ports, current and wind will move the oil slick. The wind direction determines which bank/shoreline the oil will hit. Effects if no response take place Depending on the type of oil and the weather conditions, oil floating on the water surface will partially evaporate and partially disperse naturally. Response Response ships as well as response equipment need to be sea worthy and should be usable in medium to high wave conditions. Most important aspect in ports is the shipping traffic, which is the limiting factor for adequate response. Technically, most response options are feasible. Response options for ports (area to open sea) Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft + 2 Medium aircraft +/- 1 Large aircraft - 0 Vessel +/- 1 Hand held + 2 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion +/- 1


78

Spill weather/sea state SW

Spill weather/sea state SW Spill weather scenarios (SW1 to SW5)

SW1. Sea state 1, (wind force 0-2) SW2. Sea state 2, (wind force 2-4) SW3. Sea state 3, (wind force 4-6) SW4. Sea state 4, (wind force 6-8) SW5. Sea state 5, (wind force >8)

One can make a response option choice on the basis of sea state, wind force or the associated wave height, not only at the time the spill starts but also during and foreseeing the clean up operation When these SW fiches are used one should not only look at the wind force but especially at the wave height, which may be the result of past windforce. Wind induced waves play a much more important role than swell.


79

Sea state 1 SW 1

Sea state 1 SW 1

Definition: Fiche no. Classification Wind speed (m/s) Wave height (m) SW1 Sea state 1 Beaufort 1-2 (0–2) 0–0.4

Scenario definition Wind: Calm, light air, up to light breeze. Effects observed at this sea state could be:(1) sea like mirror; Beaufort 0, or (2) ripples with appearance of scales, no foam crests; Beaufort 1, or (3) small wavelets, crests of glossy appearance, not breaking; Beaufort 2. Behaviour aspects Due to limited turbulence, the natural dispersion will be very limited to nil. Light crude oil and light oil products will only disappear by evaporation and the retention time of dispersible and heavy oils at the water surface is very long. Effects if no response take place Depending on the type of oil, oil floating on the water surface will partially evaporate and little oil will disperse naturally, form a more persistent water-in-oil emulsion, or tarry residue. Due to the very long retention time at the water surface, damage to wildlife and the coastline is very likely. Response The most important aspect is the low water surface turbulence that makes response options like mechanical recovery favourable and the use of dispersants and mechanical dispersion less effective. Response options for sea state 1 condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft - 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion +/- 1



80

Sea state 2 SW 2

Sea state 2 SW 2

Definition: Fiche no. Classification Wind speed (m/s) Wave height (m) SW2 Sea state 2 Beaufort 3-4 (2-7) 0.4–1,7

Scenario definition Wind: Gentle breeze up to moderate breeze. Effects observed at this sea state could be: (1) large wavelets, crests begin to break, scattered whitecaps; Beaufort 3 or (2) small waves, becoming longer, numerous whitecaps; Beaufort 4. Behaviour aspects Due to limited turbulence, the natural dispersion will be limited. Light crude oil and light oil products will only disappear by evaporation and the retention time of dispersible and heavy oils at the water surface is long. Effects if no response take place Depending on the type of oil, oil floating on the water surface will partially evaporate and some oil will disperse naturally, form a more persistent water-in-oil emulsion, or tarry residue. Due to the long retention time at the water surface, damage to wildlife and the coastline is very likely. Response At the high end of this scenario (Beaufort 4), the use of mechanical recovery becomes less effective and the use of dispersants or mechanical dispersion more favourable. At the low end (Beaufort 3), the most important aspect is the low water surface turbulence that makes response options like mechanical recovery favourable and the use of dispersants and mechanical dispersion less effective. Response options for sea state 2 condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum + 2 Disk, drum (oleophilic) + 2 Endless rope ++ 3 Conveyor belt + 2 Weir ++ 3 Brush + 2 Drum, grabber + 2 R3 Use of dispersants by spraying Small aircraft ++ 3 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel ++ 3 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion +/- 1



81

Sea state 3 SW 3

Sea state 3 SW 3

Definition: Fiche no. Classification Wind speed (m/s) Wave height (m) SW3 Sea state 3 Beaufort 5-6 (7-12) 1,7–3,0

Scenario definition Wind: Fresh breeze up to strong breeze. Effects observed at sea could be: (1) moderate waves, taking longer form, many whitecaps, some spray; Beaufort 5, to (2) larger waves foaming, whitecaps everywhere, more spray; Beaufort 6. Behaviour aspects Due to high turbulence the natural dispersion will be substantial. The retention time of dispersible oil at the water surface is intermediate to short. Effects if no response take place Depending on the type of oil, oil floating on the water surface will partially evaporate and disperse naturally, can form a more persistent water-in-oil emulsion or tarry residue (SO3 and SO4). Depending the retention time at the water surface, damage to wildlife and the coastline is likely. Response Response ships as well as response equipment should be usable in rough sea conditions. Severe water surface turbulence makes response options like the use of dispersants and mechanical dispersion favourable and mechanical recovery less effective. Technically a number of response options is feasible. Response options for sea state 3 condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum +/- 1 Disk, drum (oleophilic) +/- 1 Endless rope ++ 3 Conveyor belt +/- 1 Weir ++ 3 Brush +/- 1 Drum, grabber +/- 1 R3 Use of dispersants by spraying Small aircraft + 2 Medium aircraft + 2 Large aircraft ++ 3 Vessel + 2 Hand held + 2 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion + 2 R7 Sorbents +/- 1 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1


82

Sea state 4 SW 4

Sea state 4 SW 4

Definition: Fiche no. Classification Wind speed (m/s) Wave height (m) SW4 Sea state 4 Beaufort 7-8 (12 – 18) 3,0 – 4,3

Scenario definition Strong to heavy winds. Effects observed at sea could be:(1) sea heaps up, white foam from breaking waves begins to be blown in streaks; Beaufort 7 or (2) moderately high waves of greater length, edges of crests begin to break into spindrift foam is blown in well marked streaks; Beaufort 8. Behaviour aspects Due to severe turbulence the natural dispersion will be predominant. The retention time of dispersible oil at the water surface is short Effects if no response take place Depending on the type of oil, oil floating on the water surface, will partly evaporate and disperse naturally or can form a more persistent water-in-oil emulsion or tarry residue. Depending the retention time at the water surface, damage to wildlife and the coastline is less likely in the case of non persistent oils. Response Response ships as well as response equipment should be usable in very rough sea conditions. The most important aspect is the very severe water surface turbulence that makes most response options ineffective. Technically, only a few response options may be feasible. Response options for sea state 4 condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt - 0 Weir - 0 Brush - 0 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft - 0 Medium aircraft - 0 Large aircraft +/- 1 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3



83

Sea state 5 SW 5

Sea state 5 SW 5

Definition: Fiche no. Classification Wind speed (m/s) Wave height (m) SW5 Sea state 5 >Beaufort 8 (> 18) >4,3

Scenario definition Gale storm up to hurricane winds. Effects observed at this sea state could be (1) high waves, sea begins to roll, dense streaks of foam, spray may reduce visibility; Beaufort 9, or (2) very high waves with overhanging crests, sea takes white appearance as foam is blown in very dense streaks, rolling is heavy and visibility reduced; Beaufort 10, (3) exceptionally high waves, sea covered with white foam patches, visibility still more reduced; Beaufort 11, (4) air filled with foam, sea completely white with driving spray, visibility greatly reduced; Beaufort >11. Behaviour aspects Due to very severe turbulence the natural dispersion will be predominant. The retention time of dispersible oil at the water surface is very short. Effects if no response take place Depending on the type of oil, oil floating on the water surface will mainly disperse naturally, or form a more persistent water-in-oil emulsion or tarry residue (SO3 and SO4). Depending the retention time at the water surface, damage to wildlife and the coastline is limited in the case of non persistent oils. Response The most important aspect is the very severe water surface turbulence that makes any response ineffective, or dangerous. The only active option is to monitor. Response options for sea state 5 and higher condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt - 0 Weir - 0 Brush - 0 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft -- 0 Medium aircraft -- 0 Large aircraft -- 0 Vessel - 0 Hand held - 0 R4 Mechanical dispersing the oil Any vessel - 0 R5 In situ burning - 0 R6 Monitoring and leave to natural dispersion ++ 3

R7 Sorbents -- 0 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1

84

Spill current SC

Spill current SC Spill current (SC1 to SC4) For current conditions at the spill site, four scenarios are defined:

SC1. No current SC2. Low current (<0.34 m/s) SC3. Medium current (0.34 – 0.58 m/s) SC4. Strong current (>0.58 m/s)


85

No current SC1

No current SC1

Definition: Fiche no. Classification Speed (m/s) Dilution SC1 No current Zero Very limited

Scenario definition No water movement. Enclosed water spaces like canals and lakes. Hardly any dilution. Behaviour aspects As there is no current, a slick of oil will only be moved by wind. Effects if no response take place Depending on the type of oil and wind force, oil floating on the water surface will evaporate and disperse naturally, or forms a more persistent water-in-oil emulsion or tarry residue. Transport of the oil is only affected by the wind force and direction. The oil will move with approximately 3% of the wind speed. Dilution of dispersed oil is very limited, resulting in higher oil concentrations in the top water column. Response The absence of current is the ideal situation for mechanical recovery using booms and the use of dispersants and mechanical dispersion less effective. Response options for no current condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft +/- 1 Large aircraft +/- 1 Vessel +/- 1 Hand held +/- 1 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion +/- 1



86

Low current SC 2

Low current SC 2

Definition: Fiche no. Classification Speed (m/s) Dilution SC2 Low current <0.34 Limited

Scenario definition The water movement is limited. Little dilution occur. Behaviour aspects As there is limited current, a slick of oil will mainly be moved by the wind and only marginally by current. Effects if no response take place Depending on the type of oil and wind force, oil floating on the water surface will evaporate and disperse naturally, or forms a more persistent water-in-oil emulsion or tarry residue. Transport of the oil is only affected by the wind force and direction. The oil will move with approximately 3% of the wind speed. Dilution of dispersed oil is limited, resulting in low to medium oil concentrations in water column depending on the total water depth. Response Limited current is a workable situation for static or dynamic mechanical recovery. Technically, there are several response options feasible. Response options for low current condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum ++ 3 Disk, drum (oleophilic) ++ 3 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft +/- 1 Medium aircraft +/- 1 Large aircraft +/- 1 Vessel +/- 1 Hand held +/- 1 R4 Mechanical dispersing the oil Any vessel +/- 1 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion +/- 1



87

Medium current SC 3

Medium current SC 3

Definition: Fiche no. Classification Speed (m/s) Dilution SC3 Medium current 0.34 – 0.58 Good

Scenario definition The water movement is medium (0.34 to 0.58 m/s) resulting in good dilution. Behaviour aspects As there is medium current, a slick of oil will be moved by the wind as well as by the current. Dilution of dispersed oil is good resulting in low to very low oil concentrations in the water column depending on the total water depth. Effects if no response take place Depending on the type of oil and wind force, oil floating on the water surface will evaporate and disperse naturally, or forms a more persistent water-in-oil emulsion or tarry residue. Transport of the oil is affected by the wind and current force and direction. Response Medium current is a workable situation for mechanical recovery using dynamic skimmers. Booms will have problems with currents approximating the critical speed of 0.5 m/s. Technically, there are several response options feasible. Response options for medium current condition Technical

feasible Score



R2 Mechanical recovery using static systems Vacuum + 2 Disk, drum (oleophilic) + 2 Endless rope ++ 3 Conveyor belt ++ 3 Weir ++ 3 Brush ++ 3 Drum, grabber ++ 3 R3 Use of dispersants by spraying Small aircraft + 2 Medium aircraft + 2 Large aircraft + 2 Vessel + 2 Hand held + 2 R4 Mechanical dispersing the oil Any vessel + 2 R5 In situ burning +/- 1 R6 Monitoring and leave to natural dispersion + 2



88

Strong current SC 4

Strong current SC 4

Definition: Fiche no. Classification Speed (m/s) Dilution SC4 Strong current > 0.58 Very high

Scenario definition The water movement is high (velocity > 0.58 m/s), resulting in high dilution. Behaviour aspects As there is strong current, a slick of oil will be moved by the wind as well as by the current. Dilution of dispersed oil is very high resulting in very low oil concentrations in the water column depending on the total water depth. Effects if no response take place Depending on the type of oil and wind force, oil floating on the water surface will evaporate and disperse naturally, or forms a more persistent water-in-oil emulsion or tarry residue. Transport of the oil is affected by the wind and current force and direction. Dilution of naturally dispersed oil is very fast resulting in very low oil concentrations in the water column depending on the water depth. Response Strong current is not a workable situation for mechanical recovery using static skimmers and or booms. Booms will have problems with currents higher than the critical speed of 0.5 m/s. Technically only dynamic systems and dispersion are feasible. Response options strong current condition Technical

feasibility Score

R1 Mechanical recovery using dynamic systems Dynamic skimmer systems + 2 Dynamic net systems + 2 R2 Mechanical recovery using static systems Vacuum - 0 Disk, drum (oleophilic) - 0 Endless rope - 0 Conveyor belt - 0 Weir - 0 Brush - 0 Drum, grabber - 0 R3 Use of dispersants by spraying Small aircraft ++ 3 Medium aircraft ++ 3 Large aircraft ++ 3 Vessel ++ 3 Hand held ++ 3 R4 Mechanical dispersing the oil Any vessel ++ 3 R5 Burning the oil Fire boom - 0 R6 Monitoring and leave to natural dispersion ++ 3 R7 Sorption - 0 R8 Shoreline clean up (let the pollutant wash ashore) +/- 1

89

General references

General references Allen A.A., D.H. Dale, 1997, Oil slick classification: a system for the characterization and documentation of oil slicks, Proceedings of 1977 International Oil Spill Conference, p315-322. Cormack D., 1999, Response to Marine Oil Pollution- Review and Assessment. Kluwer Academic Publishers, Dordrecht. Schulze R., V. Keith, C. Purcell, 1997, World Catalogue of Oil Spill Response Products, Port City Press, Baltimore, Maryland. O’Sullivan A.J.,T.G. Jacques, 1998, Impact Reference System, Effects of Oil in the Marine Environment: Impact of Hydrocarbons on Fauna and Flora.

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