- Email: [email protected]
The cost of oil spills
Volume 12/Number 1l/November 1981 body of water? Superimpose the variability of some important factors with time: salinity changes in an estuary for example or changes in the particulate loading, and reliable prediction becomes impossible with our present level of understanding, Nevertheless, 'assimilative capacity' is a plausible concept, if only because it is self-evident that such a capacity must exist. But perhaps the concept should act primarily as an incentive for research on the multiplicity of
factors that influence the biological effects of toxic effluents, rather than being pressed into service by those who controleffluent discharges. In spite of thesearguments the Crystal Mountain Workshop was prepared to consider the U.S. Coastal Waters as an 'underutilized' and 'renewable resource'; a point of view which presupposes that it is possible to calculate "assimilative capacity".
A . R . D . STEBBING
Marine Pollution Bulletin, Vol. 12, No. 11, pp. 363-367, 1981 Printed in Greal Britain
~ _ ~ ~ f ~ _ ) @ ~ ~
0025-326X/81/110363~5 $02.00/0 © 1981 Pergamon Press Ltd.
I
Viewp°int is a c°lumn which all°ws auth°rs t° express their own opinions about current events.
The Cost of Oil Spills* I. C. W H I T E and J. A. NICHOLS Dr White and Mr Nichols are on the staff of the International Tanker Owners Pollution Federation Ltd., which was established in 1968 to administer the Tanker Owners Voluntary Agreement concerning Liability for Oil Pollution (TOVALOP). Members of the Federation's technical staff attend major oil spills from tankers around the world to advise on clean-up techniques and also give advice on contingency planning. This paper was presented at a recent OECD seminar on the Economic Consequences of Oil Spills, the proceedings of which are to be published. In comparing the costs of major oil spills little or no attempt is usually made to explore the reasons for the considerable differences that are identified. Table 1 provides an analysis of the approximate costs and claims resulting from selected major oil spills from tankers in different parts of the world in order to demonstrate the variation that can occur in the cost of individual elements and of the whole incident. This paper describes some of the practical factors that contribute to this variation. These will be considered under three broad and inter-related headings, viz.: (1) Nature of the incident; (2) Clean-up response; (3) Damage. No attempt is made to discuss the legal aspects of compensation or to review the literature on the subject, Similarly, clean-up techniques, effects of oil pollution and the response arrangements of different countries will not be discussed indetail. It is hoped that the general points outlined in this paper will highlight some of the practical factors that need to be
considered when discussing the economic consequences of major oil spills and demonstrate that analyses of oil spill costs solely in terms of the amount spilled need to be viewed with caution.
Nature of the Incident
Oil type All oils are a complex mixture of components with differing physical, chemical and biological properties. When an oil is spilled on to the surface of the sea it undergoes a number of changes, some of which enhance its natural dissipation whilst others cause it to persist. The fate and effects of an oil type and the clean-up requirements will depend primarily, therefore, upon the combined physical and chemical properties of its components. Thus light refined products, such as gasoline, kerosene and some light .crude oils which are highly volatile materials with low viscosities, do not persist on the surface of the sea for any significant length of time due to rapid evaporation and natural dispersion. Spills of these materials therefore do not normally require a clean-up response. Heavy crude and *The viewsexpressedare those of the authors and do not necessarily reflectthoseoftheindividualDirectorsandMembersoftheInternational residual fuel oils on the other hand may be expected to Tanker Owners PollutionFederationLimited. persist on the sea due to their greater proportion of involatile 363
Marine PolLution Bulletin TABLE 1 Analysis of claims resulting from selected oil spills from tankers. (N.B. In some cases the rounded figures represent amounts claimed rather than compensation awarded.)
Type of oil
Estimated amount spilled (tonnes)
Clean-up claim (£) At sea On shore
Year
A
1975
Crude
2000
92100
32 900
B
1976
Heavy fuel
1000
0
4 000 000
C
1977
Crude and heavy fuel
30 000
282 300
427 600
800
710 700
24
A
1978
Heavy fuel
7500
2 665 200
958 200
13 900
3 637 300
485
A
1978
Heavy fuel
1100
300 000
2 700 000
2455
D
1979
Crude
300
0
758 500
808 800
2696
E
1979
Crude
150
800 000
3 000 000
3 800 000
25 333
F
1980
Crude
70
107 000
1529
2 400 000
59 200
components and high viscosity. Such oils are also resistant to many clean-up techniques and large spills frequently cause widespread contamination of coastlines requiring extensive and costly clean-up operations, The nature of the damage caused will also vary according to the type of oil spilt. Light refined products tend to be more toxic and may cause mortalities of marine plants and animals. Such effects will, however, be localized due to the low persistence of the oil on the water surface. These oils may also constitute a fire hazard if spilt in confined situations and may result in a wide variety of third party claims due, for example, to temporary closure of port areas or nearby industry. Persistent crude and fuel oils, whilst generally of lower toxicity, will constitute a threat to seabirds and other organisms that become physically coated. By the widespread contamination of shorelines and structures they will also usually cause considerable amenity damage,
Location The location of a spill can have a considerable bearing on the costs since it will determine the resources threatened and the clean-up response required, All oils, if they remain at sea long enough, will dissipate through natural processes and may in such cases pose a significant threat only to seabird concentrations. Even major spills of persistent residual fuel oil off the coast may never affect shorelines if offshore winds and currents prevail. In such cases it would not be necessary to mount an active response beyond surveillance of the slick to monitor its movement and breakdown. Conversely, a large spill of a light refined product in a confined situation may necessitate a clean-up response to counter the threat of fire and explosion, Socio-economic factors and resources at risk (e.g. amenities, fisheries, marine life, sea birds and industry) will also vary within and between countries. Some areas will be of high national or even regional importance due to the presence of one or a combination of these resources whereas other areas will only rank as locally important. Seasonal differences will also occur. These variations will not only have implications for the degree of the damage caused but will also help determine the nature and extent of the clean-up operation. The physical characteristics of the spill site (e.g. prevailing winds, tidal range, currents, water depth) will also be important since they will have a considerable beating on the 364
50 300 47 800
Damage claim (£) Total claim (£)
Cost per tonne of oil (£)
Country
None -
None
125 000
63
4 000 000
4000
feasibility of mounting both a clean-up response at sea and a successful salvage operation. They will also help determine the extent of shoreline contamination. Similarly the vulnerability of shorelines, the extent to which they are selfcleaning, the feasibility of undertaking manual clean-up (e.g. accessibility, likelihood of clean-up causing more damage than the oil itself), the availability and cost of local labour and many other site-specific factors will influence the cost of oil spill clean-up.
Otherfactors The rate of spillage as well as the total quantity spilled is important in determining the extent of contamination, ease of clean-up, degree of damage and resulting costs. For example, the clean-up operation required in response to a single large release of oil may be considerable but could be completed in a matter of weeks. The associated damage to marine resources and amenities may also be short-term. However, the same quantity of oil lost over several months from a damaged vessel or oil rig close to the coast may require the maintenance of a major clean-up effort, repeated cleaning of amenity areas and long-term effects on natural resources and tourism. Such a situation would also probably call for costly threat removal measures. Removal of the remaining cargo from a damaged tanker not only makes economic sense but is the most effective way of minimizing further pollution. Whilst this can be a relatively straightforward operation in the case of a vessel that remains afloat, it becomes difficult and costly if the vessel sinks in exposed offshore waters. The difficulty of the operation can be increased further if the cargo is viscous oil. The costs of such operations often far exceed the costs of the sea and shore clean-up operations. Whilst the justification for instituting such measures will depend upon an evaluation of the threat posed to the coast by the remaining cargo, the inclusion of such costs in spill statistics on clean-up without qualification is likely to give rise to bias and misunderstanding. The analysis of oil spill costs can be further complicated when a major proportion of the oil 'lost' is burnt. Published spill statistics for such incidents frequently show considerable variation depending upon whether the proportion of the oil estimated to have been burnt is included or not. Burning has a more practical complication: the remaining highly persistent tarry residue is very difficult to deal with and often results in high clean-up costs. Burning can also give rise to secondary pollution such as smoke, 'oily rain'
Volume 1 2 / N u m b e r l l / N o v e m b e r 1981
and sulphur dioxide emissions, which may result in third party claims,
Clean-upResponse Clean-up policy As a general rule, most countries have followed the policy that every attempt should be made to deal with oil spills at sea, thus preventing the damage, high clean-up costs and public outcry that are often associated with extensive pollution of inshore waters and shorelines. As already discussed, oil spills will on occasions dissipate naturally and not pose a threat to coastal resources. Even oil on shorelines will on occasions be best left to natural processes. The decision not to respond, however, is a diffcult one, especially as it may be viewed by the public, politicians and media as a sign of incompetence. An active response is therefore usually adopted even when technical opinion is agreed that it is not justified and it will have no practical benefit. Insomecasesthehighcostsofimplementingatechnically unjustified response can be exacerbated by an increase in the problems of dealing with the oil subsequently or by increasing the damage caused, Technical limitations of the "at-sea"response Whilst the priority attention and large financial investment that has historically been given to the 'at-sea' response (often to the detriment of the 'on-shore' response) is clearly founded on a laudable concept, it has rarely, if ever, been demonstrated as being realisticduring a major oil spill. The failure of this strategy is due largely to the fact that oil spilt on to the surface of the sea spreads rapidly and covers an area too great to be countered by available techniques. Add to this the limitations on containment and collection systems imposed by winds, waves and currents and the problems posed by the rapid formation of water-inoil emulsions (mousse) on the effectiveness of chemical dispersants and the pumping arrangements of recovery devices and it is apparent why an 'at sea' response is only likely to be partially successful in preventing shoreline pollution in a major spill close to the coast, Benefits of the "at-sea"response The actual cost and effectiveness of an 'at-sea' response will depend upon many factors including the nature of the incident; the availability of trained personnel and required equipment and materials; the number of vessels, aircraft and specialized equipment employed; and, perhaps most importantly, the effectiveness of the controlling organization and pre-spill planning. It is, however, useful to examine the likely benefits of an 'at-sea' response in general terms, It is frequently assumed that any oil dealt with at sea will reduce shore contamination and costs associated with cleanup. This will depend, however, upon the circumstances of the incident and the conduct of the operation. Consider, for example, a spill of 5000 tonnes of a medium crude oil, the fate of which might be as follows: 30°7o by volume would evaporate rapidly and be removed. Ifit is assumed that 30% of the remaining 3500 tonnes (1050 tonnes) is dealt with effectively at sea (a very optimistic figure by past experience) before stranding or emulsion formation renders further treatment impossible, 2450 tonnes will remain. This will typically form a water-in-oil emulsion to the extent that each
tonne of oil will take up some four tonnes of water. The result will therefore be some 12 250 tonnes of mousse, over double the quantity of oil originally spilt despite the apparently successful clean-up at sea. Of course, the quantity of mousse would be proportionately greater if no attempt had been made to combat the oil at sea. What is more important is that if, as is quite likely, the 'at-sea' treatment did not reduce the length of coastline eventually contaminated then it is highly questionable whether the shore clean-up operations will have been eased, or costs significantly reduced, bearing in mind such operations are often labour-intensive and involve the large scale removal of sand and debris in addition to the mousse. The main incentive for an offshore clean-up response and related programme of coastal protection by using booms should not therefore be to reduce clean-up costs per se but to prevent damage to specific resources which may either have commercial value or be of ecological importance. This approach, however, demands a high level of pre-spill planning to identify priorities for protection and an appropriate response strategy; an understanding of the limitations of the techniques available and a very high degree of control during clean-up operations. The more usual approach is for the limited resources available to be spread thinly in an attempt to protect all the coastline with little ornoresultantbenefit.
Shore clean-up It is often assumed that shore clean-up is much more costly than offshore clean-up. Valid comparisons are virtually impossible as no two incidents are identical and offshore clean-up is usually incomplete, leaving the bulk of the oil to be dealt with on the shore. However, case histories and calculations of the relative costs per tonne of oil 'removed' (as an index of success) demonstrate that offshore clean-up can be relatively more expensive. One reason for this is that shore clean-up often relies on manual recovery methods and locally available equipment which can be cheap in contrast to offshore clean-up which, for even limited success, requires considerable amounts of expensive equipment, vessels and aircraft which may have to be obtained from a distance. However, one of the most important factors determining the costs of shore clean-up in any spill is the extent to which cleaning is required or, how clean is clean? The standards of clean-up vary from country to country and from area to area and are related to the nature of the shoreline contaminated, its usage and national attitudes. Thus, amenity beaches oiled during the holiday season will be required to be cleaned rapidly to a high level to permit their use whereas salt marshes and mangrove swamps may be better left to clean themselves naturally in view of their sensitivity to physical disturbance. This simple distinction overlooks many intermediate situations and the complications brought about by the type and amount of oil involved, the time of year, prevailing weather conditions (e.g. ice)~ and the pressures exerted by the public, politicians, the media and sectional interests. In some situations this latter aspect will result in a demand for as near total clean-up as is humanly possible, leaving nothing to natural processes. This is not only a labour-intensive operation of diminishing returns, requiring individual rock 365
Marine Pollulion Bulletin
and stone cleaning in extreme cases, but has to be balanced against the environmental damage it will cause. Whether such extreme clean-up measures are justified is debatable but will depend upon the particular circumstances of the incident. The cost of disposing of collected and oily debris will also vary considerably from area to area. The availability of a suitable land fill site near to the area being cleaned can be a low cost option compared to a situation where long distance transport of material and specialized treatment of large quantities of material is necessary. Techniques and equipment to separate stranded oil from sand and other debris on-site, thereby minimizing transport problems and permitting treatment of the liquid oil alone, may minimize the costs of disposal and be yet another factor that will cause the cost per tonne of oil spilled to vary from country to country,
Damage This is possibly the most complex aspect of the cost of oil spills. For the purpose of this paper a distinction is made between quantifiable economic damages as a direct result of an oil spill (e.g. loss of income from fishing, tourism) and damage to natural resources not owned or commercially exploited (e.g. seabirds). The prime difference between the two categories is that in the former, the resource or product is commercially exploited and can be ascribed a definite value. Even in such cases, the calculation of the extent and magnitude of any loss and substantiation of a cause/effect relationship may present considerable difficulties. Whilst reference to pre-spill production or earnings is a valuable starting point for the quantification of any loss, correlation of this data with a given spill is open to uncertainties due to the influence of other factors that are difficult or impossible to quantify e.g. duration of the effect, losses brought about by natural factors. These difficulties tend to be small, however, compared with those faced when attempting to calculate the value of a natural resource which is not commercially exploited and about which little is known.
Natural resourcedamage Changes in the species composition and fluctuations in numbers is a fundamental feature of all plant and animal populations and communities, whether commercially exploited or not. A 'normal' situation, therefore, as regards any particular natural habitat is a dynamic one which is very difficult to define with any precision at a single point in time even with the benefit of detailed study over many years. The ability of a habitat to recover from a disturbance will depend upon the recovery potential of the individual species, Abundant organisms with highly mobile planktonic larvae produced regularlyinlargenumbersmayrepopulateanarea rapidly whereas long-lived, slowly maturing species with low reproductive rates will take many years to reappear in numbers and age distribution comparable to the pre-spill situation. Whilst the significance of natural resource damage caused by an oil spill will depend largely upon the recovery potential of the individual species and the indirect impact on commercial species, it is pertinent to view such damage in the perspective of the not uncommon catastrophes caused by purely natural factors, such as severe climatic 366
conditions. All these considerations combine to ensure that" crucial terms in the discussion of natural resource damage such as 'normal' and 'recovery' can rarely be defined with precision in most situations. It can be strenuously argued that damage to natural resources that neither have any owner nor recognize any boundary is not compensatable and that some degree of environmental disturbance is one of the inevitable consequences of man's activities in the marine environment whether that be through fishing, industrial development, permitted pollutant discharges, or the pursuance of recreational activities. This should not be taken to be a demand for freedom to pollute; it is merely a call for a realistic appraisal of the benefits and the disadvantages to society of the marine production and transport of oil, and a request that damage caused by oil spills should not be singled out for 'special' treatment on merely emotive grounds. Indeed it could be argued that if compensation were available for damage to all natural resources this would do little to prevent pollution and the costs would ultimately pass on to the consumer.
Calculation of natural resource damage Assuming that environmental damage should be compensated, what are the technical and scientific problems? Almost invariably detailed knowledge of the resource prior to the spill will be lacking. Difference of opinion on the extent of the damage, the recovery potential of the resource and the long-term effects is therefore an almosl~ inevitable starting point even when a study programme has been instituted following the incident. It will frequently be argued that an oil spill has caused damage to the ecosystem as a whole and that since the basis of the food web leading to commercial species has been damaged this will result in an economic loss in the future. Such views are often speculative and ignore the natural recovery potential of the environment. Faced with a lack of basic scientific agreement on the damages caused by an oil spill and the lack of an easily defined 'value' it is hardly surprising that controversy exists. Further complications can arise when parts of the environment that previously have been destroyed to make way for other developments are suddenly regarded as the most important natural resource the country possesses and fundamental to the survival of valuable commercial fisheries. An attempt is then made to calculate the value of the resource. In the absence of data from detailed pre- and postspill investigations and any direct market value, calculations are frequently based on assumptions that give a false impression of scientific precision and are seemingly carried out with the sole aim of justifying a compensation figure selected in advance. Thus, attempts have been made to cost the damage on the basis of the calorific value of the resources affected, the unit value of each animal above a certain size allegedly killed, the quantity of oxygen theoretically consumed from the water during the natural degradative process, the estimated cost of restoring the environment to its pre-spill condition. All are based more on theory than on facts from the particular spill and all require sweeping assumptions regarding interactions between species and relationships with some generally arbitrarily chosen economic value. All
Volume 12/Number l l/November
1981
have in common the fact that they result in enormous claims for compensation that appear to have little relation to the nature and extent of the damage or to the use to which the money might be put. Even the apparently realistic concept of replacement is rarely feasible as the damage can often only be repaired by natural processes. Sensitive environments such as salt marshes and mangroves might also suffer more serious damage by the physical disturbance caused by attempts at restoration. Replacement of damaged plants and removal of contaminated substrate might also result in an aesthetically pleasing environment that belies the damage caused to the physical structure of the area and to the animal populations in the substrate that cannot be readily transplanted from elsewhere, If any compensation obtained for natural resource damage is unlikely to be usable to assist recovery then what is it likely to be used for? Its use for funding future research, oil spill combat arrangements or its payment to international environment agencies has been proposed, None is likely to be universally acceptable with the result that
any compensation so obtained is unlikely to be used to the benefit of the area damaged or the environment in general. All the above considerations lead to the view that such calculations can be regarded as an elaborate method of calculating a penalty to be levied by the State on the polluter. It requires international agreement to decide the extent to which society as a whole wishes to pay for such penal measures.
Conclusions An attempt has been made to highlight some of the practical problems that should be taken into account when discussing the economic consequences of major oil spills. Whilst a comprehensive review has not been attempted it is hoped that sufficient of the technical and scientific difficulties have been elucidated to illustrate that oil spill clean-up and damage assessment are not and are never likely to be precise arts. A similar lack of precision must be accepted when analysing costs.
MarinePollutionBulletin,Vol. 12, No. I I, pp. 367-371, 1981
0025-326X/81/1103674)5 $02.00/0 © 1981 Pergamon Press Ltd.
Printed in Great Britain
Mercury in Coastal and Estuarine Sediments of the Northeastern Irish Sea J. E. RAE* and S. R. ASTON t
Department of Environmental Sciences, University of Lancaster, Lancaster LA1 4 YQ, UK *Present address: t Present address:
Department of Geology, University of Reading, Reading, RG6 2AB, UK International Laboratory of Marine Radioactivity, Music OcOanographique, Monaco
Mercury concentrations in surface intertidal sediments from estuarine and coastal environments of the Northeastern Irish Sea are reported. This region has two inputs of mercury contaminated effluents from chlor-alkali factories, and localized mercury contamination of sediments fairly similar to that reported for the Rhine has been found in the Wyre estuary. The present results for the Mersey estuary agree well with others reported in the lierature. Coastal sediments are much less contaminated than the estuarine deposits, and in all the environments studied strong correlations between mercury concentration, total organic carbon and < 63/~m grainsize fraction contents have been found,
Earlier studies have demonstrated the importance of superficial sediments in the removal of natural and pollutant mercury from natural waters, and their importance as indicators of mercury pollution (Klein & Goldberg, 1970; Appelquist etal., 1972; Hugger etal., 1972; Andren, 1973; Aston et al., 1973). The Northeastern Irish Sea receives
mercury inputs from natural weathering, sewage disposal and industrial effluents. The major industrial use of mercury is the chlor-alkali industry (D.O.E., 1976), and two chlor-alkali factories using the moving mercury electrode method for the electrolysis of brine operate in this region. Mercury contaminated effluents from these factories are discharged to the estuaries of the rivers Mersey and Wyre (Fig. 1), and the concentrations of mercury in the sediments of the Mersey estuary have been reported (Craig & Morton, 1976; Bartlett et al., 1978; Bartlett & Craig, 1981). The present paper reports and comments on the concentrations of total mercury in intertidal sediments in several coastal and estuarine environments of the Northeastern Irish Sea, with particular attention to the sediments of the Wyre estuary which has not received attention in the literature.
Sampling and Analysis Most surface sediment samples were collected at lowwater by removing the uppermost 1 cm of sediment over an 367
factors that influence the biological effects of toxic effluents, rather than being pressed into service by those who controleffluent discharges. In spite of thesearguments the Crystal Mountain Workshop was prepared to consider the U.S. Coastal Waters as an 'underutilized' and 'renewable resource'; a point of view which presupposes that it is possible to calculate "assimilative capacity".
A . R . D . STEBBING
Marine Pollution Bulletin, Vol. 12, No. 11, pp. 363-367, 1981 Printed in Greal Britain
~ _ ~ ~ f ~ _ ) @ ~ ~
0025-326X/81/110363~5 $02.00/0 © 1981 Pergamon Press Ltd.
I
Viewp°int is a c°lumn which all°ws auth°rs t° express their own opinions about current events.
The Cost of Oil Spills* I. C. W H I T E and J. A. NICHOLS Dr White and Mr Nichols are on the staff of the International Tanker Owners Pollution Federation Ltd., which was established in 1968 to administer the Tanker Owners Voluntary Agreement concerning Liability for Oil Pollution (TOVALOP). Members of the Federation's technical staff attend major oil spills from tankers around the world to advise on clean-up techniques and also give advice on contingency planning. This paper was presented at a recent OECD seminar on the Economic Consequences of Oil Spills, the proceedings of which are to be published. In comparing the costs of major oil spills little or no attempt is usually made to explore the reasons for the considerable differences that are identified. Table 1 provides an analysis of the approximate costs and claims resulting from selected major oil spills from tankers in different parts of the world in order to demonstrate the variation that can occur in the cost of individual elements and of the whole incident. This paper describes some of the practical factors that contribute to this variation. These will be considered under three broad and inter-related headings, viz.: (1) Nature of the incident; (2) Clean-up response; (3) Damage. No attempt is made to discuss the legal aspects of compensation or to review the literature on the subject, Similarly, clean-up techniques, effects of oil pollution and the response arrangements of different countries will not be discussed indetail. It is hoped that the general points outlined in this paper will highlight some of the practical factors that need to be
considered when discussing the economic consequences of major oil spills and demonstrate that analyses of oil spill costs solely in terms of the amount spilled need to be viewed with caution.
Nature of the Incident
Oil type All oils are a complex mixture of components with differing physical, chemical and biological properties. When an oil is spilled on to the surface of the sea it undergoes a number of changes, some of which enhance its natural dissipation whilst others cause it to persist. The fate and effects of an oil type and the clean-up requirements will depend primarily, therefore, upon the combined physical and chemical properties of its components. Thus light refined products, such as gasoline, kerosene and some light .crude oils which are highly volatile materials with low viscosities, do not persist on the surface of the sea for any significant length of time due to rapid evaporation and natural dispersion. Spills of these materials therefore do not normally require a clean-up response. Heavy crude and *The viewsexpressedare those of the authors and do not necessarily reflectthoseoftheindividualDirectorsandMembersoftheInternational residual fuel oils on the other hand may be expected to Tanker Owners PollutionFederationLimited. persist on the sea due to their greater proportion of involatile 363
Marine PolLution Bulletin TABLE 1 Analysis of claims resulting from selected oil spills from tankers. (N.B. In some cases the rounded figures represent amounts claimed rather than compensation awarded.)
Type of oil
Estimated amount spilled (tonnes)
Clean-up claim (£) At sea On shore
Year
A
1975
Crude
2000
92100
32 900
B
1976
Heavy fuel
1000
0
4 000 000
C
1977
Crude and heavy fuel
30 000
282 300
427 600
800
710 700
24
A
1978
Heavy fuel
7500
2 665 200
958 200
13 900
3 637 300
485
A
1978
Heavy fuel
1100
300 000
2 700 000
2455
D
1979
Crude
300
0
758 500
808 800
2696
E
1979
Crude
150
800 000
3 000 000
3 800 000
25 333
F
1980
Crude
70
107 000
1529
2 400 000
59 200
components and high viscosity. Such oils are also resistant to many clean-up techniques and large spills frequently cause widespread contamination of coastlines requiring extensive and costly clean-up operations, The nature of the damage caused will also vary according to the type of oil spilt. Light refined products tend to be more toxic and may cause mortalities of marine plants and animals. Such effects will, however, be localized due to the low persistence of the oil on the water surface. These oils may also constitute a fire hazard if spilt in confined situations and may result in a wide variety of third party claims due, for example, to temporary closure of port areas or nearby industry. Persistent crude and fuel oils, whilst generally of lower toxicity, will constitute a threat to seabirds and other organisms that become physically coated. By the widespread contamination of shorelines and structures they will also usually cause considerable amenity damage,
Location The location of a spill can have a considerable bearing on the costs since it will determine the resources threatened and the clean-up response required, All oils, if they remain at sea long enough, will dissipate through natural processes and may in such cases pose a significant threat only to seabird concentrations. Even major spills of persistent residual fuel oil off the coast may never affect shorelines if offshore winds and currents prevail. In such cases it would not be necessary to mount an active response beyond surveillance of the slick to monitor its movement and breakdown. Conversely, a large spill of a light refined product in a confined situation may necessitate a clean-up response to counter the threat of fire and explosion, Socio-economic factors and resources at risk (e.g. amenities, fisheries, marine life, sea birds and industry) will also vary within and between countries. Some areas will be of high national or even regional importance due to the presence of one or a combination of these resources whereas other areas will only rank as locally important. Seasonal differences will also occur. These variations will not only have implications for the degree of the damage caused but will also help determine the nature and extent of the clean-up operation. The physical characteristics of the spill site (e.g. prevailing winds, tidal range, currents, water depth) will also be important since they will have a considerable beating on the 364
50 300 47 800
Damage claim (£) Total claim (£)
Cost per tonne of oil (£)
Country
None -
None
125 000
63
4 000 000
4000
feasibility of mounting both a clean-up response at sea and a successful salvage operation. They will also help determine the extent of shoreline contamination. Similarly the vulnerability of shorelines, the extent to which they are selfcleaning, the feasibility of undertaking manual clean-up (e.g. accessibility, likelihood of clean-up causing more damage than the oil itself), the availability and cost of local labour and many other site-specific factors will influence the cost of oil spill clean-up.
Otherfactors The rate of spillage as well as the total quantity spilled is important in determining the extent of contamination, ease of clean-up, degree of damage and resulting costs. For example, the clean-up operation required in response to a single large release of oil may be considerable but could be completed in a matter of weeks. The associated damage to marine resources and amenities may also be short-term. However, the same quantity of oil lost over several months from a damaged vessel or oil rig close to the coast may require the maintenance of a major clean-up effort, repeated cleaning of amenity areas and long-term effects on natural resources and tourism. Such a situation would also probably call for costly threat removal measures. Removal of the remaining cargo from a damaged tanker not only makes economic sense but is the most effective way of minimizing further pollution. Whilst this can be a relatively straightforward operation in the case of a vessel that remains afloat, it becomes difficult and costly if the vessel sinks in exposed offshore waters. The difficulty of the operation can be increased further if the cargo is viscous oil. The costs of such operations often far exceed the costs of the sea and shore clean-up operations. Whilst the justification for instituting such measures will depend upon an evaluation of the threat posed to the coast by the remaining cargo, the inclusion of such costs in spill statistics on clean-up without qualification is likely to give rise to bias and misunderstanding. The analysis of oil spill costs can be further complicated when a major proportion of the oil 'lost' is burnt. Published spill statistics for such incidents frequently show considerable variation depending upon whether the proportion of the oil estimated to have been burnt is included or not. Burning has a more practical complication: the remaining highly persistent tarry residue is very difficult to deal with and often results in high clean-up costs. Burning can also give rise to secondary pollution such as smoke, 'oily rain'
Volume 1 2 / N u m b e r l l / N o v e m b e r 1981
and sulphur dioxide emissions, which may result in third party claims,
Clean-upResponse Clean-up policy As a general rule, most countries have followed the policy that every attempt should be made to deal with oil spills at sea, thus preventing the damage, high clean-up costs and public outcry that are often associated with extensive pollution of inshore waters and shorelines. As already discussed, oil spills will on occasions dissipate naturally and not pose a threat to coastal resources. Even oil on shorelines will on occasions be best left to natural processes. The decision not to respond, however, is a diffcult one, especially as it may be viewed by the public, politicians and media as a sign of incompetence. An active response is therefore usually adopted even when technical opinion is agreed that it is not justified and it will have no practical benefit. Insomecasesthehighcostsofimplementingatechnically unjustified response can be exacerbated by an increase in the problems of dealing with the oil subsequently or by increasing the damage caused, Technical limitations of the "at-sea"response Whilst the priority attention and large financial investment that has historically been given to the 'at-sea' response (often to the detriment of the 'on-shore' response) is clearly founded on a laudable concept, it has rarely, if ever, been demonstrated as being realisticduring a major oil spill. The failure of this strategy is due largely to the fact that oil spilt on to the surface of the sea spreads rapidly and covers an area too great to be countered by available techniques. Add to this the limitations on containment and collection systems imposed by winds, waves and currents and the problems posed by the rapid formation of water-inoil emulsions (mousse) on the effectiveness of chemical dispersants and the pumping arrangements of recovery devices and it is apparent why an 'at sea' response is only likely to be partially successful in preventing shoreline pollution in a major spill close to the coast, Benefits of the "at-sea"response The actual cost and effectiveness of an 'at-sea' response will depend upon many factors including the nature of the incident; the availability of trained personnel and required equipment and materials; the number of vessels, aircraft and specialized equipment employed; and, perhaps most importantly, the effectiveness of the controlling organization and pre-spill planning. It is, however, useful to examine the likely benefits of an 'at-sea' response in general terms, It is frequently assumed that any oil dealt with at sea will reduce shore contamination and costs associated with cleanup. This will depend, however, upon the circumstances of the incident and the conduct of the operation. Consider, for example, a spill of 5000 tonnes of a medium crude oil, the fate of which might be as follows: 30°7o by volume would evaporate rapidly and be removed. Ifit is assumed that 30% of the remaining 3500 tonnes (1050 tonnes) is dealt with effectively at sea (a very optimistic figure by past experience) before stranding or emulsion formation renders further treatment impossible, 2450 tonnes will remain. This will typically form a water-in-oil emulsion to the extent that each
tonne of oil will take up some four tonnes of water. The result will therefore be some 12 250 tonnes of mousse, over double the quantity of oil originally spilt despite the apparently successful clean-up at sea. Of course, the quantity of mousse would be proportionately greater if no attempt had been made to combat the oil at sea. What is more important is that if, as is quite likely, the 'at-sea' treatment did not reduce the length of coastline eventually contaminated then it is highly questionable whether the shore clean-up operations will have been eased, or costs significantly reduced, bearing in mind such operations are often labour-intensive and involve the large scale removal of sand and debris in addition to the mousse. The main incentive for an offshore clean-up response and related programme of coastal protection by using booms should not therefore be to reduce clean-up costs per se but to prevent damage to specific resources which may either have commercial value or be of ecological importance. This approach, however, demands a high level of pre-spill planning to identify priorities for protection and an appropriate response strategy; an understanding of the limitations of the techniques available and a very high degree of control during clean-up operations. The more usual approach is for the limited resources available to be spread thinly in an attempt to protect all the coastline with little ornoresultantbenefit.
Shore clean-up It is often assumed that shore clean-up is much more costly than offshore clean-up. Valid comparisons are virtually impossible as no two incidents are identical and offshore clean-up is usually incomplete, leaving the bulk of the oil to be dealt with on the shore. However, case histories and calculations of the relative costs per tonne of oil 'removed' (as an index of success) demonstrate that offshore clean-up can be relatively more expensive. One reason for this is that shore clean-up often relies on manual recovery methods and locally available equipment which can be cheap in contrast to offshore clean-up which, for even limited success, requires considerable amounts of expensive equipment, vessels and aircraft which may have to be obtained from a distance. However, one of the most important factors determining the costs of shore clean-up in any spill is the extent to which cleaning is required or, how clean is clean? The standards of clean-up vary from country to country and from area to area and are related to the nature of the shoreline contaminated, its usage and national attitudes. Thus, amenity beaches oiled during the holiday season will be required to be cleaned rapidly to a high level to permit their use whereas salt marshes and mangrove swamps may be better left to clean themselves naturally in view of their sensitivity to physical disturbance. This simple distinction overlooks many intermediate situations and the complications brought about by the type and amount of oil involved, the time of year, prevailing weather conditions (e.g. ice)~ and the pressures exerted by the public, politicians, the media and sectional interests. In some situations this latter aspect will result in a demand for as near total clean-up as is humanly possible, leaving nothing to natural processes. This is not only a labour-intensive operation of diminishing returns, requiring individual rock 365
Marine Pollulion Bulletin
and stone cleaning in extreme cases, but has to be balanced against the environmental damage it will cause. Whether such extreme clean-up measures are justified is debatable but will depend upon the particular circumstances of the incident. The cost of disposing of collected and oily debris will also vary considerably from area to area. The availability of a suitable land fill site near to the area being cleaned can be a low cost option compared to a situation where long distance transport of material and specialized treatment of large quantities of material is necessary. Techniques and equipment to separate stranded oil from sand and other debris on-site, thereby minimizing transport problems and permitting treatment of the liquid oil alone, may minimize the costs of disposal and be yet another factor that will cause the cost per tonne of oil spilled to vary from country to country,
Damage This is possibly the most complex aspect of the cost of oil spills. For the purpose of this paper a distinction is made between quantifiable economic damages as a direct result of an oil spill (e.g. loss of income from fishing, tourism) and damage to natural resources not owned or commercially exploited (e.g. seabirds). The prime difference between the two categories is that in the former, the resource or product is commercially exploited and can be ascribed a definite value. Even in such cases, the calculation of the extent and magnitude of any loss and substantiation of a cause/effect relationship may present considerable difficulties. Whilst reference to pre-spill production or earnings is a valuable starting point for the quantification of any loss, correlation of this data with a given spill is open to uncertainties due to the influence of other factors that are difficult or impossible to quantify e.g. duration of the effect, losses brought about by natural factors. These difficulties tend to be small, however, compared with those faced when attempting to calculate the value of a natural resource which is not commercially exploited and about which little is known.
Natural resourcedamage Changes in the species composition and fluctuations in numbers is a fundamental feature of all plant and animal populations and communities, whether commercially exploited or not. A 'normal' situation, therefore, as regards any particular natural habitat is a dynamic one which is very difficult to define with any precision at a single point in time even with the benefit of detailed study over many years. The ability of a habitat to recover from a disturbance will depend upon the recovery potential of the individual species, Abundant organisms with highly mobile planktonic larvae produced regularlyinlargenumbersmayrepopulateanarea rapidly whereas long-lived, slowly maturing species with low reproductive rates will take many years to reappear in numbers and age distribution comparable to the pre-spill situation. Whilst the significance of natural resource damage caused by an oil spill will depend largely upon the recovery potential of the individual species and the indirect impact on commercial species, it is pertinent to view such damage in the perspective of the not uncommon catastrophes caused by purely natural factors, such as severe climatic 366
conditions. All these considerations combine to ensure that" crucial terms in the discussion of natural resource damage such as 'normal' and 'recovery' can rarely be defined with precision in most situations. It can be strenuously argued that damage to natural resources that neither have any owner nor recognize any boundary is not compensatable and that some degree of environmental disturbance is one of the inevitable consequences of man's activities in the marine environment whether that be through fishing, industrial development, permitted pollutant discharges, or the pursuance of recreational activities. This should not be taken to be a demand for freedom to pollute; it is merely a call for a realistic appraisal of the benefits and the disadvantages to society of the marine production and transport of oil, and a request that damage caused by oil spills should not be singled out for 'special' treatment on merely emotive grounds. Indeed it could be argued that if compensation were available for damage to all natural resources this would do little to prevent pollution and the costs would ultimately pass on to the consumer.
Calculation of natural resource damage Assuming that environmental damage should be compensated, what are the technical and scientific problems? Almost invariably detailed knowledge of the resource prior to the spill will be lacking. Difference of opinion on the extent of the damage, the recovery potential of the resource and the long-term effects is therefore an almosl~ inevitable starting point even when a study programme has been instituted following the incident. It will frequently be argued that an oil spill has caused damage to the ecosystem as a whole and that since the basis of the food web leading to commercial species has been damaged this will result in an economic loss in the future. Such views are often speculative and ignore the natural recovery potential of the environment. Faced with a lack of basic scientific agreement on the damages caused by an oil spill and the lack of an easily defined 'value' it is hardly surprising that controversy exists. Further complications can arise when parts of the environment that previously have been destroyed to make way for other developments are suddenly regarded as the most important natural resource the country possesses and fundamental to the survival of valuable commercial fisheries. An attempt is then made to calculate the value of the resource. In the absence of data from detailed pre- and postspill investigations and any direct market value, calculations are frequently based on assumptions that give a false impression of scientific precision and are seemingly carried out with the sole aim of justifying a compensation figure selected in advance. Thus, attempts have been made to cost the damage on the basis of the calorific value of the resources affected, the unit value of each animal above a certain size allegedly killed, the quantity of oxygen theoretically consumed from the water during the natural degradative process, the estimated cost of restoring the environment to its pre-spill condition. All are based more on theory than on facts from the particular spill and all require sweeping assumptions regarding interactions between species and relationships with some generally arbitrarily chosen economic value. All
Volume 12/Number l l/November
1981
have in common the fact that they result in enormous claims for compensation that appear to have little relation to the nature and extent of the damage or to the use to which the money might be put. Even the apparently realistic concept of replacement is rarely feasible as the damage can often only be repaired by natural processes. Sensitive environments such as salt marshes and mangroves might also suffer more serious damage by the physical disturbance caused by attempts at restoration. Replacement of damaged plants and removal of contaminated substrate might also result in an aesthetically pleasing environment that belies the damage caused to the physical structure of the area and to the animal populations in the substrate that cannot be readily transplanted from elsewhere, If any compensation obtained for natural resource damage is unlikely to be usable to assist recovery then what is it likely to be used for? Its use for funding future research, oil spill combat arrangements or its payment to international environment agencies has been proposed, None is likely to be universally acceptable with the result that
any compensation so obtained is unlikely to be used to the benefit of the area damaged or the environment in general. All the above considerations lead to the view that such calculations can be regarded as an elaborate method of calculating a penalty to be levied by the State on the polluter. It requires international agreement to decide the extent to which society as a whole wishes to pay for such penal measures.
Conclusions An attempt has been made to highlight some of the practical problems that should be taken into account when discussing the economic consequences of major oil spills. Whilst a comprehensive review has not been attempted it is hoped that sufficient of the technical and scientific difficulties have been elucidated to illustrate that oil spill clean-up and damage assessment are not and are never likely to be precise arts. A similar lack of precision must be accepted when analysing costs.
MarinePollutionBulletin,Vol. 12, No. I I, pp. 367-371, 1981
0025-326X/81/1103674)5 $02.00/0 © 1981 Pergamon Press Ltd.
Printed in Great Britain
Mercury in Coastal and Estuarine Sediments of the Northeastern Irish Sea J. E. RAE* and S. R. ASTON t
Department of Environmental Sciences, University of Lancaster, Lancaster LA1 4 YQ, UK *Present address: t Present address:
Department of Geology, University of Reading, Reading, RG6 2AB, UK International Laboratory of Marine Radioactivity, Music OcOanographique, Monaco
Mercury concentrations in surface intertidal sediments from estuarine and coastal environments of the Northeastern Irish Sea are reported. This region has two inputs of mercury contaminated effluents from chlor-alkali factories, and localized mercury contamination of sediments fairly similar to that reported for the Rhine has been found in the Wyre estuary. The present results for the Mersey estuary agree well with others reported in the lierature. Coastal sediments are much less contaminated than the estuarine deposits, and in all the environments studied strong correlations between mercury concentration, total organic carbon and < 63/~m grainsize fraction contents have been found,
Earlier studies have demonstrated the importance of superficial sediments in the removal of natural and pollutant mercury from natural waters, and their importance as indicators of mercury pollution (Klein & Goldberg, 1970; Appelquist etal., 1972; Hugger etal., 1972; Andren, 1973; Aston et al., 1973). The Northeastern Irish Sea receives
mercury inputs from natural weathering, sewage disposal and industrial effluents. The major industrial use of mercury is the chlor-alkali industry (D.O.E., 1976), and two chlor-alkali factories using the moving mercury electrode method for the electrolysis of brine operate in this region. Mercury contaminated effluents from these factories are discharged to the estuaries of the rivers Mersey and Wyre (Fig. 1), and the concentrations of mercury in the sediments of the Mersey estuary have been reported (Craig & Morton, 1976; Bartlett et al., 1978; Bartlett & Craig, 1981). The present paper reports and comments on the concentrations of total mercury in intertidal sediments in several coastal and estuarine environments of the Northeastern Irish Sea, with particular attention to the sediments of the Wyre estuary which has not received attention in the literature.
Sampling and Analysis Most surface sediment samples were collected at lowwater by removing the uppermost 1 cm of sediment over an 367