Hazardous Materials

26.0     Hazardous material spills

26.0.1   This chapter of the Counter Pollution Manual deals with incidents involving Hazardous and Noxious Substances (HNS). It contains brief information for Operational Control Authorities (OCA) and On-Scene Co-ordinators (OSC) about the procedures to be followed, and possible measures to be taken, after notification has been received that an accidental spillage of bulk “chemicals” or packaged goods containing hazardous substances other than oil has occurred.

26.0.2   In this chapter, categories of chemical substances (based on their physico-chemical characteristics) are described according to their behaviour, together with the risks posed to human health and the environment so that the appropriate techniques for responding to the spill, and measuring and detecting the spill, can be selected.

26.0.3   The procedure that should be followed to assess the risks posed by a chemical spill and to decide on the most appropriate way to respond is outlined in the following flow diagram:

Figure 1  Flow diagram of general approach to a chemical spill

26.0.4   Once the hazardous substance that has been released has been identified (Name, UN number and/or IMDG class) an assessment of the potential risks can be made. If there is a reaction with water or air the reaction products also need to be taken into account.

26.0.5   Based on the state of aggregation, the density, solubility and vapour pressure, the behaviour class can be identified (see Figure 3 ). Once the behaviour class is known the potential hazards can be identified (see Figure 4 ).

26.0.6   For decision making purposes it is important to determine first the seriousness of the spill situation. Computer models in combination with on scene measurements and/or sampling can be used for this purpose. In sections 26.2 and 26.3 rules of thumb and back of envelope calculations are given to determine the contaminated area. By defining the seriousness of the situation, an informed decision can be made about the most appropriate way of responding to the situation. Use of the classification systems described in paragraph 26.1 is a fast and relatively simple way to select the most appropriate response action from those described in paragraph 26.6.

26.1   Categorisation of hazardous substances

26.1.1   Thousands of different chemical substances are transported by sea in bulk or in packaged form. Modern chemical tankers vary in size from 1 000 to 50 000 ton dead weight. Most tankers used to transport chemicals and dangerous goods are double hulled, in order to prevent the release of cargo in the event of a collision or grounding. A large tanker can contain up to 35 different tanks each containing a different chemical. Chemical tankers have to abide by specific regulations controlling the storage of substances. Packaged goods are often transported in containers with numerous different substances on board of one vessel. Less dangerous liquid cargoes are transported in single hull vessels.

26.1.2   The probability of an accident is limited but always present as recent ship incidents involving chemicals have shown. Dealing with individual chemicals during a chemical spill is complex and requires chemical expertise. Chemical substances have therefore been grouped in behaviour categories and hazard effect categories to facilitate decision making in the case of a chemical spill. This is in order to limit the number of standard response approaches to chemical spills. The choice of the appropriate approach is based on (1) short term behaviour of a spill released into the water and (2) the potential hazards of a possible release.

26.1.3   When gases, liquids or solids enter the marine environment various types of behaviour are possible. This depends on the solubility, density and vapour pressure of the substance involved.

Figure 2 Primary release forms of chemical substances spilled in the marine environment

26.1.4   Released substances can form gas clouds, evaporate from the water surface, float on the water surface, dissolve into the water column, sink to the bottom, or show combinations of these behaviour types. Physico-chemical properties such as solubility, density and vapour pressure mainly determine the short-term behaviour of the substances in the marine environment. Based on the short-term behaviour which is most relevant for response actions, released chemical substances can be divided into four major behaviour categories and ten sub-behaviour categories (see Figure 3).

Figure 3  Categories of chemical substances and the physico-chemical characteristics (density, vapour pressure and solubility) on which the categorisation is based. The density is specified as 1023kg/m³, this might vary in different locations depending on the salinity.

26.1.5   Human populations as well as the marine environment can be exposed to spilled hazardous chemical substances. Nine potential hazards can be distinguished when chemical substances enter the marine environment. The hazards are listed in Figure 4 and described accordingly for each behaviour category.

* G = Gases; E = Evaporators; F = Floaters; D = Dissolvers and S = Sinkers

Figure 4  Most relevant hazards of chemical substances within a behaviour category for humans and the marine environment

26.1.6   Substances released into the marine environment could pass into the air (gas clouds), onto the water surface (floaters), into the water column (dissolvers), to the water bottom (sinkers), or a combination of these. Each behaviour has its own relevant hazard aspects. For example, toxicity to human populations and explosivity are typical hazard aspects of substances which pass into the air after a release. Figure 5 gives some examples of chemicals in the different behaviour groups.

Figure 5  Examples of chemicals in the different behaviour groups

26.1.7   The advantage of such an approach is that it limits the response action plans that need to be worked out, and there is no need for an action plan for each separate chemical substance. In addition, training courses on how to deal with chemical spills are simpler and do not require a thorough knowledge of chemical substances. As long as one can put place a spilled chemical in the correct response category, it will be easier to take decisions on how to deal with the spilled substance.

26.1.8   Seven response categories are distinguished based on the behaviour class and the relevant hazard aspects (potential effects).

Figure 6  Summary of possible response categories

26.1.9   Lost packages could contain very dangerous substances which could escape into the water because of damage to the package or, in the long term, due to corrosion and therefore need to be recovered. Packages could float, submerge or sink. Their potential danger is dealt with in the same way as bulk substances. It should be recognized, however, that packaged chemicals would always be present in smaller volumes than bulk chemicals.

26.1.10 A scenario which is not covered by the response categories based on behaviour and potential hazards is the scenario in which chemicals react or where there is a potential danger for reaction. Polymerisation, reactions between different chemicals on board, reaction of chemicals with water or reaction caused by heat or fire are some examples. In all such circumstances, decision making is more complex as experts are required to predict the possible consequences of such reactions not only to the environment but also to the ship’s construction. Although a substance may not be particularly harmful in itself, the results of any reaction could be extremely dangerous. Information is therefore needed about the type of reaction products that are formed with water, acids, bases, metals, organic compounds, flammable substances, and oxidising and reducing agents. Other factors which must be taken into account when assessing the hazards associated with particular substances are the subsidiary phenomena that accompany these reactions, such as: formation of foam; formation of fog; change of colour; reactions in which poisonous or flammable substances are formed; fire; spattering; heat release.

26.1.11 It is of vital importance that people working in areas where dangerous chemicals are involved should be aware of the reaction risks involved.

26.1.12 Chapter 26 further deals with the steps to be taken in the case of an accidental spills of hazardous materials other than oil, e.g:

-        Notification/verification (see 26.2)

-        Initial measures (see 26.3)  

-        Hazard assessment (Situation analysis) (see 26.4)

-        Decision making (see 26.5)

-        Response actions (see 26.6)

A property glossary is given in chapter 26.9.

26.2   Notification and verification

26.2.1   Accurate information must be obtained as quickly as possible about the position of the casualty and other vessels involved, and about the type of substance released and its quantity. This information will need to be confirmed after the first report. Verification of the information can be obtained first by direct communication, via coastal radio station, with the master or pilot of the stricken vessel, and then by local reconnaissance, preferably by helicopter or aircraft with an expert from the competent operational control authority. Information can also be obtained or verified through the agent of the vessel, and also through the port authorities of the last port of call or the port of destination. Later, if it is safe to do so, a response vessel can be brought close to the casualty for further inspection.

26.2.2   A major problem at the initial stage of accidents involving hazardous materials is the lack of adequate information. Sometimes there is a problem in the precise identification of the cargo and loading plan. Much of the information contained in the initial report will be incorrect, and will need to be verified:

-                    obtain an accurate position for all vessels involved;

-                    confirm type and quantity of substances involved;

-                    confirm estimates of quantity of substance released;

-                    determine exact location of the released substance(s);

-                    determine if reactions are likely (polymerisation, between chemicals or with water).

26.2.3   This should be done by: direct communication with the casualty vessel via radio link; aerial reconnaissance by helicopter and experienced observers; an expert team on board a vessel based close to the casualty or contacts with ship owners, cargo owners, last port of call etc.

26.2.4   Determining the exact location of the discharged substance(s) is one of the first actions to be taken after a release of chemical(s) has occurred. The location of the release and its trajectory as a function of time needs to be determined. Local conditions at the spill site (i.e. weather, currents, wave heights, and water depth) have to be known, because these conditions will determine the fate and effects of a spill at sea.

26.2.5   The following are rules of thumb on how to determine the location of the spilled substance(s):

-        Gases or evaporators: The cloud will travel in the general direction of the prevailing wind. It will tend to broaden and become more diluted the further it travels, lessening the toxicity and the explosivity risks. The danger-zone associated with the cloud will be roughly elliptical or teardrop in shape. From the point of release, the cloud will move with the actual wind speed in the prevailing wind direction in a triangular area with an angle of 30-60°. The area defined from a 30° angle is the danger zone. The 60° angle can be used as an additional safety factor.

-        Floaters: From the point of release a slick will move at a rate of 3% of the actual wind speed in the prevailing wind direction and 100% of the tidal current speed in the tidal current direction.

-        Dissolvers: From the point of release the dissolved cloud in the water will move with the actual tidal current speed in the prevailing tidal current direction in a triangular area with an angle of 30-60°. The area defined from a 30° angle is the danger zone. The 60° angle is used as an additional safety factor.

-        Sinkers: From the point of release the sinker will move with the actual current speed in the current direction as long it is submerged and not on the seabed. The sinking speed can be roughly calculated using Stoke’s Law e.g. the sinking speed S (m/s) is a function of the gravitational force g (9,81 m.s^-2) times the density differences between water and oil Δρ (kg.m^-3) times the diameter size of the droplets/lumps d (m) to the power 2 divided by the dynamic viscosity of the water η ( 9.81x10^-3 kg.m^-1.s^-  at 20 ºC) times 18. The sinking time is the depth divided by the sinking speed.

26.2.6   The location and trajectory of a spill can be defined more precisely with the help of computer models. When the response team is in the vicinity of a spill, more precise identification of the spill needs to be assessed. This can either be done visually or by measuring and sampling techniques.

26.3   Initial measures

26.3.1   The activation of emergency measures depends on the nature of the chemical, the source location and the prevailing weather conditions, taking into account local hydrodynamic and meteorological information. High priority has to be given to the protection of involved ship(s) crew(s) and the safety of passing ships and emergency measures in order to minimise or eliminate further outflow of hazardous substances.

26.3.2   Certain measures may be necessary as emergency steps before the situation has been fully evaluated:

-                    decide whether or not there is an imminent threat to important resources or to human health;

-                    ensure appropriate protection for the crews of involved vessels;

-                    ensure the safety of passing vessels;

-                    alert responsible and relevant authorities;

-                    take necessary steps to minimise or eliminate further outflow.

26.3.3   In the initial stage of an accident where chemicals are involved it is also important to do “back of the envelope” worst case calculations to determine the largest area that can become affected by a harmful/damaging concentration. This is a rough estimate and prediction made on the basis of the first data available in order to establish a first basis for the initial response. Mathematical models should verify this calculation at a later stage in the incident as soon as more complete and accurate data becomes available.

Calculations for gas clouds
26.3.4   The worst case for gas clouds e.g. m³ of air polluted will be: the estimated amount of chemical spilled (in mg) divided by the MAC (Maximum Allowable Concentration) value (in mg/m³). To determine the area polluted one can assume an average height of the gas cloud of 10 m and divide the m³ air polluted by 10.

Calculations for clouds in the water column
26.3.5   The size (m²) of the worst case cloud in the water will be the estimated amount of chemical spilled (in kg) divided by 1% of the LC₅₀(96) value (mg/l) of the chemical involved and divided by assumed average depth (m) at the spill location.

Some initial response measures could be:

26.3.6   Stop or (partly) reduce release: The release can be either completely stopped or reduced. It is one of the most effective response methods if it can be applied. Since hazardous substances may be involved, response measures associated with the source of release may be particularly dangerous. Stopping the release and the overloading of cargo from the damaged tank/hold to an undamaged tank/hold or even to another vessel is one of the first options to consider. Holes in a damaged hull should be closed with the help of magnetic material, stoppers or any available material to close the hole. In the case of packages, nets can be used to prevent further losses and oversized drums can be used for damaged packages.

26.3.7   Change position of source: The main aim of changing the position of the source or cargo is to restrict the possible outflow or to reduce other hazards, simply by transferring the cargo (bulk or packaged goods) to a place where the threat posed by the substance is reduced. Methods applicable may include: removing containers from the deck; transhipping the cargo; towing the ship to a less vulnerable location.

26.3.8   Controlled release from source: Controlled release might be applied in order to reduce the dangers presented by the substance if there is risk of an uncontrolled release. Methods applicable may include destruction/explosion of the package or destruction/explosion of the ship.

26.3.9   Containment/diverting substance: Containment and diverting substances or packages from their course may enable them to be collected more easily. This method may also be used to prevent their further movement. Methods applicable may include using containment booms or using chemical booms (herders).

26.3.10 In the initial phase of the response, in the case of a ship accident in which chemicals are involved or potential losses in the marine environment are expected, the necessary measures need to be taken as quickly as possible in order to reduce or limit the effects.

26.3.11 In the case of gas clouds, a warning for aerial operations should be issued as soon as possible with an indication of the duration of the measure.

26.4   Hazard assessment

26.4.1   Risk assessments for the transport of chemicals and the hazard evaluation of a potential outflow must form part of the national ability to respond to major spills or pollution. The extent of the threat from the incident must be evaluated in order to identify the level and nature of response necessary.

26.4.2   The fate and effects of the released substance should be ascertained taking into account its behaviour, the local oceanography and meteorology, the proximity of sensitive organisms, habitats or resources, and their vulnerability to the chemicals involved.

26.4.3   Dividing the chemicals into different subcategories (E, ED, FE, F, FD, FED, DE, D, SD, and S) leads to a need for a relatively small number of generally applicable response options in the event of an accident. It is important to be aware of the hazards that chemicals can cause when released into the marine environment. The most important aspect of situation analysis is determining the hazards of an accidental spill in order to prepare a plan of action.

26.4.4   In the event of an accident at sea, pollutants may contaminate the air, the water surface, the water column and/or the sea floor and, indirectly, all the organisms in these compartments and other users of these compartments. The degree of seriousness depends amongst others on the properties of the substance released and the fate and transport of the substance in the marine environment.

26.4.5   Gases or evaporators will evaporate fast after release in or on the water and will form a gas cloud in the air. A gas cloud can be toxic or explosive or a combination of these. Inhalation of a gas or evaporator by humans or marine organisms on or near the water surface can lead to respiratory toxicity or carcinogenicity. Dense gases (heavier than air) will disperse much more slowly than gases that are lighter than air. An appreciable number of a wide range of industrial chemicals regularly transported by sea could form poisonous gas clouds if released into the marine environment. The presence of such clouds would pose a considerable threat to all those in the area. A distinction can be made between the severity of the effects caused by exposure to toxic substances i.e.

-        slight irritation, watering of the eyes and choking;

-        serious irritation, which stops when exposure ceases;  

-        damage to health;  

-        reversible damage to health;

-        irreversible damage to health;

-        death.

26.4.6   In the case of toxic gas clouds the inhalation risk presents the greatest hazard. The effect of exposure to toxins is principally determined by two factors (1) the period of exposure and (2) concentration in the atmosphere.

26.4.7   A vapour or gas cloud will drift with the wind, disperse and become diluted as a result of the turbulence in the atmosphere. The extent of the turbulence depends on the stability of the atmosphere and the roughness of the sea over which the cloud passes.

26.4.8   Floaters stay on the water surface for a certain period of time. There is little threat to the human population from hazardous substances as long as the substances float on the water surface. The pollution effects include external coating (birds) or direct toxic action to marine organisms, inhibition of natural reaeration of the waterway, and restriction of recreational and water supply uses. Even more problems arise when such a spill reaches the coast or when such a spill occurs in wintering or feeding areas for birds. In winter, many species of birds are extremely sensitive and small spills of persistent floating substances can affect the functioning of thousands of birds. Mammals can be smothered by a floating chemical, which can affect their respiratory system. However, mammals mostly tend to flee from floating layers of substances.

26.4.9   There are two main hazards associated with floaters: fire and dangers due to natural dispersion in the water column affecting the aquatic environment. Moreover, floaters may drift on the wind or current and can reach sensitive areas along the coast or wetlands. Little damage to fish is likely to be caused by hazardous substances as long as the substance floats on the surface. More problems arise when a spill occurs in or reaches shallow waters or when a spill happens in the breeding season for mammals and birds.

26.4.10 Dissolvers are substances which will quickly dilute into the water column after release. The greatest danger caused by dissolvers, due to their aquatic toxicity, is a high concentration of the hazardous substance in the water during the escape phase. In the open sea, the most seriously threatened animals are mammals (seals, porpoises, etc.), pelagic fish (herring, sprat, etc.) and zooplankton (especially larvae and eggs). In the open sea, however, most of the chemical will dilute quickly and a “no effect concentration” will soon be attained. Exceptions to this dilution phenomenon are the bio-accumulative and persistent substances that even at low concentrations must be considered harmful. Many fish species have rather restricted spawning areas in open sea, or in coastal areas. From there, eggs and larvae are transported with the currents to specific nursery areas. Often these nursery areas are productive tidal areas along the coast, such as estuaries. Spills in these areas may cause severe losses to the population, because the juvenile stages are generally much more sensitive than the adults and also occur in more concentrated numbers.

26.4.11 A dissolved chemical concentration in the water may have lethal effects. The higher the exposure concentration, the shorter the time it takes before lethal effects appear. In an actual spill situation the concentration in the water is not constant and will also decrease over time due to dilution in the water. Dissolved chemicals may cause acute effects if the concentration exceeds a certain level for a certain exposure time. At low concentrations, and/or at short exposure times, only limited effects may be expected.

26.4.12 Knowledge of water mixing characteristics will result in a better understanding of the risks to aquatic ecosystems as a result of acute pollution into the water column. The theoretical concentration of a particular spill scenario, assuming that the chemical has been dissolved into the water, can be calculated (Predicted Environmental Concentration (PEC)) and compared with toxicity effect threshold concentrations as given in 26.3.

26.4.13 Dilution of chemicals in estuaries and seawater is predominantly dictated by oscillations from wind and tide currents. The concentration in the water depends primarily on the mixing capacity (dilution rate) of the water body.

26.4.14 Due to the turbulence of the receiving water, the chemical will dilute in all directions and will at some point reach levels where no effects will occur. Hence, knowledge about the range and degree of mixing in relation to local hydrology is important for establishing criteria and standards that can be used for the risk assessment of dissolved substances.

26.4.15 The concentration primarily depends on the amount of substance spilled, and on the depth of the water. Secondly, the horizontal spread of the dissolved substance in the water determines the dilution and by that the concentration as a function of time. As a consequence, the initial concentration will be high, but the number of exposed organisms is limited, while later on there will be an enormous increase of exposed organisms due to the increased volume of water containing the diluted substance, but only at a much lower exposure concentration.

26.4.16 Spills in this group (Dissolvers) lead to a cloud/plume of dissolved substance that will drift away with the current. Often it is assumed here that organisms are exposed continuously to the cloud/plume, and that the concentration decreases in time as a result of dilution. This is a conservative assumption, since only planktonic organisms (algae, zooplankton) are transported with the water current; benthic organisms are fixed at one place and will only be exposed for the time it takes the polluted water volume to pass; for mobile organisms like fish, the exposure time is rather unpredictable, but will be shorter than ‘continuous’.

26.4.17 In waters with a high mixing energy, such as the North Sea , the risk of dissolved substances is much lower than in low mixing waters such as harbour areas. The PEC in the water column is determined by the initial dilution over the water column (from water surface to water bottom or mixing depth) followed by a horizontal dilution factor depending on specific hydrological conditions of the receiving water body.

26.4.18 Sinkers are substances that will sink to the seabed due to their density and stay on the sea floor for a certain period. Sinkers are generally hazardous to the marine environment due to aquatic toxicity, whereas direct danger to human beings is very limited. In the open sea, the most sensitive areas are the spawning grounds. Chemical spills may directly affect benthic fish and their predators. Mammals avoid pollution by sinkers and, therefore, mammals will be affected minimally. Pelagic fish also share this mechanism by avoiding pollution. Problems could occur when large quantities of bulk substances are released on the seabed. The major effect in such cases is the blanketing of the seabed, thereby covering the zoöbenthos. The contribution of zoöbenthos to the biomass of the food chain is prominent in coastal waters and intertidal zones. Spills in these waters can, therefore, cause severe losses to zoöbenthos and if the spill penetrates the sediment by bioturbation or otherwise, losses may occur over long periods.

26.5   Decision making

26.5.1   Once an accidental spill has occurred, the type and degree of damage to human health and the marine environment will to a considerable extent be a matter of chance. The type and degree of damage depends partly on fortuitous circumstances and partly on the actions taken to minimise damage. Each spill will have its own detrimental effects in the aquatic environment. The damage may range from insignificant to catastrophic. The primary aims of a chemical substance spill response are to:

-        protect human health and safety;

-        minimise environmental impacts; and

-        restore the environment, as far as is practicable, to pre-spill conditions.

26.5.2   The range of counter pollution measures to be applied will depend upon the location of the spill, type and quantity of the pollutant, the environmental sensitivity and biodiversity of the area affected. Good management and planning, as well as the response actions put into effect by the responsible authority can minimise the environmental impact of a chemical or hazardous substance spill.

26.5.3   Decision-making systems must be based on adequate information about: (1) Hazard analysis (kind of substance released, reaction ability, behaviour, potential outflow and potential impact) and (2) Response options (methods and techniques for minimising input and recovery of released substances; measures for maintaining safety of navigation; alerting measures for safety of adjacent populated areas and appropriate protection for response teams).

26.5.4   Decision-making must incorporate an evaluation of the threat posed by the released chemical to human health and the marine environment and related interests. Before decision-making can start, the following information about the (potential) spill(s) needs to be known:

-        the behaviour category and/or sub categories

-        the potential hazards  

-        the ability to reaction (polymerisation, reaction with water or with air etc)  

-         the spill location and predicted trajectory.

26.5.5   Once the dimensions and/or concentrations of the spill are known the impact of the spill can be assessed. The sensitivity of the area between the initial spill and its final destination also determines the seriousness of a spill. Once a spill or package has been localised, c