© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 1 Alun Lewis Oil Spill Consultant Different aspects of oil spill dispersants.

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 2 Purpose of Workshop “To develop decision trees and guidance for dispersant use in the Netherlands EEZ of the North Sea”  Having a national policy regarding dispersant use does not imply that dispersant use will be automatically allowed in all (or perhaps any) areas of the Netherlands EEZ  The guidance will provide the framework for rational decisions to be made

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 3 Important points  Dispersants are used to remove oil from the surface of the sea –If dispersed in deeper water, the spilled oil will not drift into shallow water where most damage is caused –Coastal habitats will not be polluted with oil  Successful use of dispersants inevitably means that oil is transferred into water column –Damage caused by dispersed oil is not inevitable –Dispersion followed by adequate dilution causes relatively little effect

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 4 Three main questions about dispersants 1. Will dispersants work? –Sometimes, but not every time and not under all circumstances 2. Will dispersing the oil do more good than harm? –Any oil spill response that causes more damage than the spilled oil is pointless. If dispersion of oil would cause more harm than good, don’t do it! 3. How should dispersants be used? –Dispersant “approval” –Strategic and operational issues

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 5 1. Will dispersants work?  Dispersion of spilled oil is a natural process caused by wave action –Low viscosity oils in very rough sea conditions naturally disperse (e.g. the Braer incident in 1993) –But natural dispersion stops when an oil ‘weathers’  Adding dispersant enhances this natural process –Higher viscosity oils in calmer sea conditions will disperse when dispersant is added  There are limits to dispersant capabilities –High viscosity oils cannot be dispersed –Limiting viscosity depends on sea-state

Workshop on the use of oil spil dispersants in the North Sea 5 0 Water depth (m) 1 4 2 3 Emulsification Natural dispersion

Workshop on the use of oil spil dispersants in the North Sea Emulsification 5 0 Water depth (m) 1 4 2 3 Natural dispersion

Workshop on the use of oil spil dispersants in the North Sea 5 0 Water depth (m) 1 4 2 3

Workshop on the use of oil spil dispersants in the North Sea 0.5 0 Oil layer thickness (mm)

Workshop on the use of oil spil dispersants in the North Sea 0.5 0 Oil layer thickness (mm) After many hours…

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 26 The effect of dispersants  The active ingredients in dispersants (the surfactants) greatly reduce the high interfacial tension between oil and water  Surfactants act as a bridge between the oil and water – The chemical barrier between oil and water is almost totally removed  Mixing of the dispersant-treated oil and water by waves causes very small oil droplets to be formed – These will not float out anywhere near as fast

Workshop on the use of oil spil dispersants in the North Sea Chemically enhanced dispersion 5 0 Water depth (m) 1 4 2 3 Spray dispersant onto spilled oil

Workshop on the use of oil spil dispersants in the North Sea Dispersant enhanced dispersion 5 0 Water depth (m) 1 4 2 3

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 44 Dispersion of small oil droplets  Small dispersed oil droplets will be rapidly diluted by the water motion that exists under waves – They are kept in top few metres by water motion under all waves (not just breaking waves) – As they rise up due to limited buoyancy, they are then pushed back down again into the water – Normally penetrate only the top 10 metres of water, but can go deeper in rougher seas – Small dispersed oil droplets do not sink to the bottom – Dispersed oil is rapidly biodegraded to a large extent by natural micro-organisms in the sea

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 45 1. Will dispersants work?  Consider this question first – If a dispersant does not work there is no point considering the potential consequences (positive and negative) of dispersing the oil  Decision-tree based on: – Should dispersants be used on the spilled oil? – Can the spilled oil be dispersed? – For how long will it be dispersible? – Are the sea conditions suitable for dispersion?

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 46 1.Should dispersants be used on the type of spilled oil? 2.Is the spilled oil of a type that is dispersible? 3.Is the oil likely to be within the time “window of opportunity’ for dispersant use? 4.Are the sea conditions suitable for dispersion? DO NOT USE DISPERSANT USE DISPERSANT NOYESOR YES ORNO YESORNO YESORNO

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 47 Oil type DISPERSE?WHY? GasolineNO Dispersants would work, Kerosene (Jet fuel) NO but would force toxic Marine Gas Oil NO components of oil into Marine Diesel Oil NO water column Crude oil (paraffinic) YES Until the time Crude oil (naphthenic) YES “Window of opportunity” Crude oil (asphaltic) YES runs out Crude oil (waxy) MAYBE Pour Point? Hydraulic oil NO Lube oil NO IFO-30YES Until the time IFO-80YES “Window of opportunity” IFO-180YES runs out IFO-380MAYBE Only at high sea temperature or rough sea IFO-500NO Viscosity too high IFO-700NO

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 48 Is the spilled oil dispersible? Oil type DISPERSIBLE FOR HOW LONG? Crude oil (paraffinic) YES Until the time Crude oil (naphthenic) YES “Window of opportunity” Crude oil (asphaltic) YES runs out Crude oil (waxy) MAYBE Pour Point? IFO-30YES Until the time IFO-80YES “Window of opportunity” IFO-180YES runs out IFO-380MAYBE Only at high temperature or rough sea

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 49 Oil “weathering” and the “window of opportunity” for dispersant use  Crude oils and residual fuel oils are not pure chemicals –Consist of an almost infinitely variable mixture of hydrocarbons  Each individual crude oil and fuel oil will ‘weather’ at a specific rate that depends on: –Temperature (mainly sea temperature) High temperature causes rapid evaporation of volatile components and therefore rapid viscosity increaseHigh temperature causes rapid evaporation of volatile components and therefore rapid viscosity increase –Wind speed and sea state High wind speed and rough seas cause high rate of natural dispersion, but also rapid emulsificationHigh wind speed and rough seas cause high rate of natural dispersion, but also rapid emulsification

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 50 The problem of “knowns and unknowns” After Donald Rumsfeld  Does the “window of opportunity” for dispersant use have to be determined precisely for every single oil that is transported through the Netherlands EEZ of the North Sea? –No A great deal of information is already available and can be usedA great deal of information is already available and can be used –Oil spill response is often about informed judgements, not scientific precision EMSA recently sponsored the development of a simple tool that gives an indication of the window of opportunity based on available informationEMSA recently sponsored the development of a simple tool that gives an indication of the window of opportunity based on available information

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 51 Viscosity limits for dispersion  There are no accurate general oil viscosity limits for dispersion. However, with a good dispersant: Dispersion usually possible up to 5,000 cSt Dispersion sometimes possible between 5,000 and 10,000 cSt Dispersion unlikely when viscosity above 10,000 – 20,000 cSt

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 52 Sea conditions & wind speed for dispersion  Dispersants require some breaking wave action to work well –Wind speed of at least 7 knots (Beaufort Force 2 to 3) for rapid dispersion of oil –If sea is very calm and dispersant is applied there will be no rapid dispersion, but this will happen when and if the sea gets rougher  Conditions can be too rough for effective dispersant spraying –Spilled oil becomes submerged by waves for a lot of the time

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 53 Beaufort Force 2 – Light breeze – 4 to 6 knot wind No breaking waves: Dispersant can be sprayed, but will not cause rapid dispersion of spilled oil

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 54 Beaufort Force 7 – Near Gale - 28 to 33 knot wind Starting to get too rough, but if the crew can do it, dispersant spraying still possible

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 56 Information needed for the Netherlands EEZ of the North Sea  Crude oil and residual fuel oil types transported –“Safety at Sea” project has already identified major imports, exports and trades in crude oils and Heavy Fuel Oils  Typical sea temperature range –Summer and winter temperatures at key locations  Statistical wind speed frequencies –Wind roses at key locations All of this information is available somewhere

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 57 2. Will dispersing the oil do more good than harm? If the dispersant would work, i.e. disperse the spilled oil, will the use of dispersant reduce the overall damage that would have been caused by the oil spill? There is no generic answer of “Yes” or “No” It all depends on the specific circumstances of the oil spill

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 58 Benefits and Risks of dispersant use  Dispersing the spilled oil into the water column can be beneficial –Spilled oil is removed from the sea surface and will not drift ashore or into shallow water where it does most damage  Dispersing the spilled oil into the water column may pose a risk to some marine organisms –Risk of harm is an effect of exposure and can be small if dilution is sufficient  Does the potential benefit justify the potential risk? –Net Environmental Benefit Analysis (NEBA)

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 59 Over-simplification can lead to incorrect conclusions  The decision to use, or not to use, dispersants is sometimes seen as a simple balance between: –The impact on resources most harmed by spilled oil on the sea surface and the coast Seabirds, coastal species and habitats, tourist beaches, etc.Seabirds, coastal species and habitats, tourist beaches, etc. –The impact on resources most harmed by dispersed oil Marine organisms, i.e. fish and shellfishMarine organisms, i.e. fish and shellfish  Use dispersants and the seabirds “win” –but the fish “lose”  Do not use dispersants and the fish “win” –but the birds “lose”

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 63 But it is often much more complicated than that  The ‘choice’ is often not simply between the effects on the ‘resources’ of: –Spilled oil on the sea surface –Dispersed oil in the water column  Spilled oil does damage in various ways to various organisms and resources –Not all resources will be present, or in equal proportion, or are of equal priority –Response actions can only modify some of the impacts of spilled oil  Provided that there is adequate dilution, in many circumstances dispersed oil will cause only limited and temporary effects

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 64 Damage caused by spilled oil  The damage caused by oil spills may be caused by: –Water-soluble crude oil components Exert toxic effects on marine organismsExert toxic effects on marine organisms –Spilled oil on the surface of the sea Contaminates the plumage of seabirdsContaminates the plumage of seabirds –Spilled oil that drifts into shallow water and ashore Smothers some coastal organisms,Smothers some coastal organisms, Poisons some benthic organismsPoisons some benthic organisms Pollutes benthic and coastal habitatsPollutes benthic and coastal habitats Pollutes socio-economic resources such as fishermen’s nets and tourist beachesPollutes socio-economic resources such as fishermen’s nets and tourist beaches –Dispersed oil in the water column Ingested by some organisms, especially filter-feeder shellfishIngested by some organisms, especially filter-feeder shellfish

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 65 “Toxic effects”  Lethal or sub-lethal –Mortality (death) is a very unsubtle indicator of toxicity –Sub-lethal effects can alter feeding or breeding behaviour  Acute or chronic –Short-term, non-persistent or long-term and persistent  Reversible or irreversible –‘Tainting’ of fish flesh is reversible, carcinogenic effects are not  Effects on individuals or populations? –Some individuals may be damaged / killed, but is the species population affected? Toxic effects are proportional to exposure (Concentration and period of exposure)

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 66 Physical effects of dispersant use  Water-soluble crude oil components  Spilled oil on the surface of the sea  Spilled oil that drifts into shallow water and ashore  Dispersed oil in the water column Maybe increased (if used very soon after spill) ReducedReducedIncreased

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 67 Consequences of dispersant use  Water-soluble crude oil components –Toxic effects on marine organisms  Spilled oil on the surface of the sea –Contaminates the plumage of seabirds  Spilled oil that drifts into shallow water and ashore –Smothers some coastal organisms –Poisons some benthic organisms –Pollutes benthic and coastal habitats –Pollutes socio-economic resources such as fishermen’s nets and tourist beaches  Dispersed oil in the water column –Ingested by some organisms, especially filter-feeder shellfish Maybe increased (if used very soon after spill) ReducedReducedReducedReducedReducedIncreased

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 68 Dispersant use and fisheries  Dispersant use is often of great concern to fishermen –The concern is that dispersing the oil into the water column will inevitably harm the fish stocks –The concern is both financial (short-term and long-term) and ecological  Most importantly, oil spills pose a threat to public health through contamination of the food chain –Fishing bans introduced when oil spills happen –The implications of dispersant use need to be taken into account

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 69 Marine ecological habitats and their inhabitants  Pelagic – open water, upper layers –Roundfish: Herring, mackerel, sardines, sprats, bass, mullet  Demersal – near the sea bed –Flatfish: Dover sole, plaice, flounder, turbot, monkfish and rays  Benthic – on (and in) the seabed –Flat fish; plaice, rays –Crustaceans: Lobster, crabs, crawfish, Nethrops and shrimp –Molluscs: Cockles, mussels, scallops, oysters, clams, whelks, periwinkles, cuttlefish & squid

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 70 Effects of oil spills on fish  There is no evidence to date that any oil spill has killed sufficient numbers of adult fish, or early stages, in the offshore open ocean to significantly affect the population  The potential for damage is greater in inshore waters –Adult fish swim away from spilled oil (if they can)  Fish plankton can be affected –But fish ‘over-produce’ larvae in huge numbers to overcome predation  Oil-polluted sediments can have an adverse effect on benthic species (bottom-dwellers, such as flatfish)  Oil spills do affect inshore shellfish beds

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 71 Dispersants and fisheries  Do not use dispersants: –In shallow water (less than ~ 10m) where dispersed oil at high concentration will come into contact with the seabed However, dispersant use reduces the tendency of dispersed oil to stick to sediment and persistent oil pollution of sediments will be lessened if dispersants are usedHowever, dispersant use reduces the tendency of dispersed oil to stick to sediment and persistent oil pollution of sediments will be lessened if dispersants are used –Near inshore fish spawning areas and nurseries –Near shellfish beds –Near aquaculture facilities

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 72 1. What resources are at risk of damage by spilled oil? 2. Are the resources more sensitive to: (a) Dispersed oil (a) Dispersed oil (b) Spilled oil on the surface (b) Spilled oil on the surface (c) Oil that drifts ashore (c) Oil that drifts ashore 3. Is the water deep enough for dispersion without threatening benthic organisms? 4.Is the spilled oil far enough away from shore for dispersion? 5. Is the spilled oil far enough away from resources particularly sensitive to dispersed oil? USE DISPERSANT KNOWNUNKNOWNYESNOOR NOYESOR YESNOOR YESNOOR YESNOOR YESNOOR DO NOT USE DISPERSANT

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 73 Every question poses another question  What water depth is sufficient for dispersion? –Dispersed oil is slightly buoyant so will tend to stay in upper water layers, the well-mixed zone –10 metre penetration is typical in moderate sea states (Beaufort Force wind speed 3 to 7)(Beaufort Force wind speed 3 to 7) –Goes deeper in very rough seas –Diluted as it enters deeper water  What distance is far enough away for dispersion? –Depends on prevailing currents –0.5 nautical mile or 1 nautical mile are distances typically used

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 74 How to present all this information?  On marine charts as sensitivity maps  Include: –Coastal sensitivity to oil pollution based on shoreline type –Coastal ecology Habitat types and species populationHabitat types and species population Seasonal variationsSeasonal variations –Marine ecology sensitivity maps Commercial fisheriesCommercial fisheries Sea bed types mapped by MESH will give an indication of marine habitats and probable speciesSea bed types mapped by MESH will give an indication of marine habitats and probable species –10 and 20 metre water depths –Particularly sensitive resources ecological and socio-economic resourcesecological and socio-economic resources RETURN TO THIS LATER

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 76 Dispersant “approval” and the law  Dispersant “approval” –There are two separate issues: Dispersant product approval (an “approved” dispersant list)Dispersant product approval (an “approved” dispersant list) Dispersant use approval (when and where dispersants can be used)Dispersant use approval (when and where dispersants can be used)  Legislation and regulation of dispersant use –Why is this needed? –Depends on national laws and regulations controlling the release of chemicals into the sea

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 77 Dispersant “approval”  Two separate issues (often confused): –Dispersant product approval Need to ensure that dispersant is of:Need to ensure that dispersant is of: –Maximum permitted toxicity –Minimum permitted effectiveness –Dispersant use approval Need to ensure that the use of dispersant does not cause more harm than good, i.e. make the oil spill damage worse, rather than betterNeed to ensure that the use of dispersant does not cause more harm than good, i.e. make the oil spill damage worse, rather than better

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 78 Dispersant product approval  Not incident- or site-specific; is national  Toxicity testing –Need not involve oil; aim is to ensure that the dispersant is not too toxic for use –Conduct a simple, standardised toxicity test (e.g.96 hour LC 50 procedure) on some marine species –Not a simulation of dispersant use at sea  Effectiveness testing –Use a ‘typical’ oil in an easy-to-repeat test –Not a realistic simulation of dispersion at sea –Set “pass mark”

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 79 Dispersant use approval  Is incident- and site-specific  No toxicity testing involved –Judgement of whether dispersed oil would cause a hazard based on knowledge of: water depthwater depth water flowwater flow sensitivity to dispersed oil of resources near spill locationsensitivity to dispersed oil of resources near spill location –Use the marine charts containing relevant information to define dispersant use and non-use zones

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 80 Dispersant use zones used in France  Uses spill amount, distance and water depth to produce maximum permitted dispersed oil concentration of 10 ppm Spilled oil (tonnes) Distance from shore (nautical miles) Water depth (metres) 100.55 1001.010 10002.515

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 81 Land Dispersant use permitted on Up to 10 tonnes oil 10 - 100 tonnes oil 100 - 1000 tonnes oil More than1000 tonnes oil

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 83 How to build up dispersant use / non-use zones 1.General limits set by water depth –Define water depth where dispersant use will not be allowed under any circumstances red zone For example, less than 10 metres*For example, less than 10 metres* –Define water depth where dispersant use will be permitted without restriction green zone For example, 20 metres* or moreFor example, 20 metres* or more –Zone in between is amber zone *Water depths based on charts will be LAT (Lowest Astronomical Tide) and real water will almost always be deeper and real water will almost always be deeper

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 84 How to build up dispersant use / non-use zones 2.Put coastal and marine sensitivities on chart –Shoreline types, habitats species populations –Establish priorities for protection –Decide what is more sensitive to: Spilled oil on the sea surfaceSpilled oil on the sea surface Dispersed oilDispersed oil 3.Modify size and position of zones to reflect sensitivities and protection priorities –Try to eliminate amber zones where possible

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 85 How to build up dispersant use / non-use zones 4.Consider water movement caused by ebb and flood of tides –Restrict dispersant use to prevent dispersed oil coming onto mudflats with the tide –Only allow spraying when tide is going out

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 86 Conclusions  There are several sets of “decision trees” that could form guidance for decisions about dispersant use in the Netherlands EEZ of the North Sea  This information should not stand alone, but be part of the Netherlands National Contingency Plan (NCP) –The essential part is a comprehensive sensitivity map / chart of the Netherlands EEZ of the North Sea –This enables rational decisions to be made about any oil spill response (including dispersant use)

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 87 The simple decision making process can then be reduced to: 1. Will dispersants work? –Consult subsidiary decision trees 2. Will dispersing the oil do more good than harm? –Consult dispersant use / non-use zones on charts 3. How should dispersants be used? –Approved dispersants available? YESNOOR DO NOT USE DISPERSANT YESNOOR YESNOOR USE DISPERSANT

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 88 But how could we actually use dispersants? See later: STRATEGIC AND OPERATIONAL ASPECTS OF THE APPLICATION OF DISPERSANT BY AIRCRAFT Chris Francis

© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 1 Alun Lewis Oil Spill Consultant Different aspects of oil spill dispersants.

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© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 1 Alun Lewis Oil Spill Consultant Different aspects of oil spill dispersants.

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Presentation on theme: "© 2003 By Default! A Free sample background from www.powerpointbackgrounds.com Slide 1 Alun Lewis Oil Spill Consultant Different aspects of oil spill dispersants."— Presentation transcript:

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