TL: Fixed Link across the Sound: Environmental consequences SO: Greenpeace Denmark (GP) DT: 1991 Keywords: Baltic Construction Effects Scandinavia Cars Transportation / prepared for Greenpeace Denmark by John Bagh, CASA Center for Alternative Social Analysis Linnsgade 25, 3. DK-1361 Copenhagen K Denmark Contents page Introduction and Executive Summary 1 1. Project presentation 3 2. The theoretical zero solution 6 3. Possible consequences without a zero solution 6 4. Calculated consequences of the outlined zero solution 8 5. Description of the design period 8 6. Possible consequences of changed current conditions 11 7. Sediment dispersal caused by dredging operations 13 8. Environmental consequences of sediment spillage 15 9. Immersed tunnels - an environmental alternative? 17 10. The Greenpeace View by Jesper Grolin 20 References 21 Introduction and Executive Summary This report was prepared for Greenpeace International on the basis of the CASA report "resundsforbindelser" [Fixed Links across the Sound] and the CASA memorandum "resundsforbindelsens miljkonsekvenser" [Environmental consequences of a fixed Link across the Sound] (ref. 22). The present report deals with the environmental impact on the Sound and the Baltic Sea of a fixed link across the Sound as outlined in the project proposal KM.4.2 (Alignment 2). It presents a critical review of the background material which has formed the basis of the decision behind the preliminary design of the project. Furthermore, the report evaluates the most recent proposals for an immersed tunnel as an alternative to the combined fixed link KM.4.2. The present report shows that the proposed projects for a fixed link across the Sound that have been considered by the Ministry of Transport offer several 'choices' in terms of environmental problems. The environmental consequences have not been adequately investigated. To take one example, calculations of oxygen conditions in the Sound were made on the basis of a zero solution where no redistribution of flows in the Sound takes place, although this is the case in all of the proposed solutions (ref. 3). On the whole, the entire background material fails to correspond to the conditions on which the individual studies were based. In connection with the recent discussion of immersed tunnels it is remarkable that dredging operations in the limestone layers of the Sound are suddenly regarded as a serious environmental problem when in fact the adopted KM.4.2., which is described as being "environmentally fully acceptable" (ref. 17), will require the excavation of even greater amounts of limestone. Given the Swedish demand for a zero solution, this "fully acceptable solution" will require the removal of at least 0.9 mill. m3 more limestone than would the immersed tunnel. As a considerable part of these excavations would uncover large expanses of limestone deposits, the subsequent environmental consequences would in all probability be comparably greater. Although CASA shares the widespread scepticism towards the extensive dredging operations required by the construction of an immersed tunnel, it must be noted that the adopted KM.4.2 solution will cause even greater environmental disturbances. The only way K.M.4.2. can reduce these disturbances in the Sound is by accepting a degradation of conditions in the Baltic Sea, i.e. by invalidating the Swedish demand for a zero solution. It is therefore remarkable that the only ecologically neutral solution - a bored tunnel - has not been investigated. Such a tunnel would in no way interfere with the aquatic environment and would thus have no environmental impact on the Sound or the Baltic. 1. Project presentation Project KM.4.2, which has been agreed upon by the Danish and the Swedish governments, is a combined link, i.e. a combination of bridge and tunnel constructions. The adopted design consists of the following elements: An immersed tunnel extending from a man-made peninsula near Kastrup, under Drogden, to an artificial island. The tunnel would include facilities for trains as well as for automobiles. The combined railway and motorway feeds from this island onto a low-level bridge south of the island of Saltholm. Due to the height requirements for ship passage, the low-level bridge would be succeeded by an elevated bridge across Flinterenden. This elevated bridge would abut to land in Sweden, near Lernacken, south of Limhamn. Fig. 1:Illustration of the projected alignment called 'alignment 2'. (ref. 2, p. 9) [illustration only in print edition] A construction of this design will affect the environment in a number of ways both during the construction works as well as after the completion of the link. According to available background reports, this impact is presumed to be minimal, as shown by the tables below (Figs. 2 & 3). They contain calculations of changes in hydrographic conditions in the Bornholm Basin and the central Baltic, respectively, which would be caused by the establishment of the fixed link across the Sound. The tables indicate, firstly, what effects the bridge would have on the Baltic in terms of salinity and oxygen supply and, secondly, how these effects may be reduced by compensatory measures. These measures will take the form of compensatory dredgings, for which two methods have been recommended, i.e. flat and fairway dredging. Flat dredging attempts to create the same cross-section and thereby ensure the same volume of water exchange by deepening the bottom along the alignment, thereby eliminating the increased flow resistance created by the bridge components. Fig. 2:Hydrographic conditions in the Bornholm Basin. AssumptionsAlign- mentSalinity, top layer KSalinity, bottom layer KThermo- cline depth mThermo- cline stability %Oxygen addition to bottom layer % Without KM.4.2 (basis of calculation) Incl. KM.4.2 and flat dredging (11.5 mill. m3) Incl. KM.4.2 and fairway dredging to level -7.6 Incl. KM.4.2 without compen- satory dredging [table only in print edition] 2 2 2 7.70 7.70 7.70 7.67 13.30 13.30 13.32 13.28 49.77 49.77 49.82 49.81 100 100 100.13 100.05 100 100 99.56 99.47 (ref. 2, p. 14) Fig. 3:Hydrographic conditions in the Central Baltic. Assumptions Alignment Salinity, top layer Salinity, bottom layer Thermo-cline depth mThermo- cline stability %Oxygen addition to bottom layer % Without KM.4.2 (basis of calculation) Incl. KM.4.2 and flat dredging (11.5 mill. m3) Incl. KM.4.2 and fairway dredging to level -7.6 Incl. KM.4.2 without compen- satory dredging [table only in print edition] 2 2 2 7.00 7.00 7.00 6.97 11.00 11.00 11.01 10.97 71.00 71.00 71.02 71.14 100 100 100.11 99.90 100 100 99.77 99.99 (ref. 2, p. 15) The components are, as shown in Fig. 1, a man-made peninsula, an artificial island, bridge piers, and a ramp on the Swedish side. Fairway dredging, which will be carried out in the Drogden channel, compensates exclusively for the inflow of salt water into the Baltic while the total volume of the water exchange through the Sound would be reduced, causing a reduction of the oxygen supply to the Baltic. Drogden is a shallow channel constituting a threshold against the inflow of the heavier salt water to the Baltic. This is described in further detail in the following. The calculated changes in terms of salinity and oxygen supply are slight in comparison to natural variations (ref. 1, p. 11). However, given the assumptions, the calculations are not very reliable for the following reasons: Firstly, because the alignment has not yet been finally decided upon with respect to construction. It is therefore not yet possible to determine the actual consequences of the fixed link. Secondly, the factors involved in flat dredging which might lead to a zero solution are subject to definition. A zero solution has been defined on the assumption that the same values may be applied as those on which the calculations were based. However, as this report will show, the calculated dredged volumes (11.5 mill. m3) are not sufficient to ensure a zero solution. The model for a zero solution has therefore yet to be designed. Thirdly, the simulations carried out using the hydrodynamic model (MIKE 21) and which reveal the inadequacy of the projected dredgings, were made on the basis of sub-average flow conditions. It is certain that the hydraulic resistance will increase at increased flow velocities. Hence the outlined solution will in practice be further from a zero solution than indicated by the results presented. In the following, we shall review the most important assumptions underlying the environmental evaluations made, as these assumptions determine what the investigations support. This is important, since the Swedish decision as to a fixed link was made on the condition that a combined bridge/tunnel solution would comply with a zero solution, i.e. have no environmental impact on the Baltic. This requires that water exchange (including oxygen supply) as well as the inflow of saline bottom water remains the same after the establishment of the link. 2. The theoretical zero solution As mentioned, a construction project of these proportions will increase flow resistance in the Sound, due to the flow energy loss created by the construction elements. Calculations and corrections of this have been attempted in background reports. The flow resistance of bridge piers and artificial constructions is calculated theoretically. On this basis, it is determined how extensive compensatory excavations are needed to attain a theoretical zero solution. The uncertainty of such calculations is stated to be approx. 10 per cent (ref. 12, p. 17), which is of particular relevance to the calculated resistance of the bridge and its deduced consequences. Subsequently, the topography of the Sound is simulated, taking into account the theoretically calculated excavations. This topography is the basis for the calculations of flow changes in the Sound, which will be dealt with later. 3. Possible consequences without a zero solution This theoretical zero solution is, purely by definition, presented in Figs. 2 and 3 indicating the calculated compensatory dredging. If the resistance created by the bridge and artificial island is not reduced, the impact on the eco-systems of the Baltic will be catastrophic. These waters are already particularly sensitive because of the special sea currents to and from the Baltic. These currents consist of a mixture of (heavy) saline water in the bottom layer and (light) fresh water in the top layer. Precipitation and river outfalls continuously supply the Baltic with fresh water which is exchanged with a mixture of fresh and salt water from the top (light) layer of the Kattegat and the Skagerrak. Other conditions, however, apply to the (heavy) saline water in the bottom layer. Due to their greater specific gravity, these volumes of water can only occasionally pass over the Drogden threshold (where the construction is to be situated) and near Daars (south of Lolland-Falster). Such saline breakthroughs are extremely rare, occuring at 10-15 year intervals and caused by a combination of various meteorological circumstances, typically during a heavy storm combined with favourable tidal movements. (The most recent occurrence was in 1977 (ref. 4, p. 16).) It is therefore essential that these saline breakthroughs - when they occur - are not exposed to further impediments. Any increased resistance, delaying the onset of a posssible inflow, may thus reduce or completely eliminate an inflow of salt water.In view of the fact that such inflows occur very rarely, and for very short periods of time, any delay would be fatal, as the meteorological and flow conditions which otherwise permit the inflow of salt water may change prior to a breakthrough. Dansk Hydraulisk Institut [Danish Institute of Hydraulics] concludes: "With respect to the time shifts with which the phenomena occur in the individual cases, the effect of these must be evaluated on the basis of a prolonged, more varied design period. The present results do not preclude that the delay occurring in case 4 (alignment 2 without compensatory dredging - ed.) may imply that flooding of the Drogden threshold will not occur under naturally varying wind and current conditions, should the current have time to change before the onset of the flooding". (ref. 3, p. 13) As this saline water is vital to the eco-system of the Baltic, particularly for the cod stocks, it is essential to ensure that these rare breakthroughs are not exposed to any additional resistance. The cod is particularly sensitive to slight changes in oxygen and salinity balances because it spawns in the free-moving water bodies in the saline intermediate layer of the Baltic. The spawn sinks through the water column and comes to a stop (due to the specific gravity) in a layer with a salinity of approx. 1 per cent. As the breakthroughs of saline water are the sole oxygen supply of the deep layers, the oxygen content is usually low here. If the salinity is low at the bottom layer, the spawn will sink to the bottom and die, or sink to a layer even more deficient in oxygen (ref. 4, p. 12). Thus, the relationship between oxygen content and salinity is significant for the survival of the cod. The cod is, of course, but one of several fish species in the Baltic; but any change in the number of cod in these waters would affect other fish species: "For example, a reduced cod population implies a reduced consumption of herring and sprat, which may lead to a decrease of the zooplankton population, as these are eaten by herring and sprat. As the zooplankton eats phytoplankton, a reduced zooplankton population may result in an increased biomass of phytoplankton, increased sedimentation of organic matter, and thus less oxygen in the water of the bottom layer. A reduced population of common mussel would further aggravate this effect, since the common mussel, like the zooplankton, subsists on filtering phytoplankton from the free volumes of water. Other commercially important species such as herring, sprat, plaice, dab, and turbot, will have the boundaries of their ranges moved southwards and westwards by a decreased salinity, while species such as the bleak, now limited to the northern part of the Baltic, will be favoured". (ref. 4, p. 21) The search for a zero solution is important, not least because the Baltic also confronts other threats to its environment. 4. Calculated consequences of the outlined zero solution The projected link will increase the specific resistance in the Sound by 3.7 per cent at northward current, and 5.3 per cent at southward current (ref. 2, p. 12). This increased resistance is to be eliminated by compensatory dredging. In the calculation of the effects of the Link across the Sound an attempt has been made to evaluate whether a zero solution has been attained by simulating hydraulic movements over a period of 14 days (called the 'design period') by means of EDP tools (MIKE 21). The result of these simulations reveals a 1.2 per cent reduction of the present water exchange despite a simulated flat dredging of 11.5 mill. m3. Consequently, the resistance of the bridge will, according to these simulations, only be reduced by two-thirds. Hence, the zero solution has not been attained. The background material admits to the uncertainty, noting that: "The total flow in the Sound during the simulation period (the design period) will be reduced somewhat. The flat dredgings will thus not compensate sufficiently to render the flow completely identical to that of the point of departure. This is, however, possible and will require several adjustments in a subsequent phase of detailed planning. However, it is not possible to interpret from the calculations how much additional dredging will be required". (ref. 2, p. 22) There is, however, reason to suspect that the actual reduction is greater than the calculated 1.2 per cent, this percentage being a product of the choice of design period. In the following, we shall explain why this period is not representative for an evaluation of the hydraulic resistance of the bridge construction. 5. Description of the design period The afore-mentioned model calculations on which e.g. the determination of altered flow conditions were based, were made on the assumption of a period of 14 days (14th to 28th June 1990) where current and wind conditions were calculated according to existing forecast models. This design period was selected as a 'conservative' basis for the calculations, i.e. a period in which conditions for maintaining oxygen content in the bottom layer of the Baltic are unfavourable (ref. 20, p. 5). Therefore, a period of light wind and current was chosen (the wind in this period being 5 m/s on average, and max. 10 m/s). There are no detailed accounts of current velocities in this period; it is merely mentioned that: "The period from the 14th to 18th June covers a relatively quiet period; from the 19th to 23rd June the current is mainly northerly; and from the 24th to 28th June the current is mainly southerly". (ref. 3, p. 3) However, other background reports permit a more comprehensive picture of the current during the design period. It is thus indicated that: ".... the current velocity is between 0.5 and 0.6 m/s during only 5 per cent of the period, and that only by northerly current". (ref. 5, p. 10) The current velocity is 0.6-0.7 m/s for a short period in the narrow cross- section between Amager and the artificial island (ref. 2, p. 29) solely as a consequence of a simulation of the bridge link. A consideration of corresponding yearly mean values will cast grave doubt on the general status of the design period. The yearly mean value for the Sound is: 0.79 m/s for northerly current, 0.54 m/s for southerly current (ref. 6). It appears from this that the highest velocities during the design period do not match the yearly mean value for northerly current. Moreover, the current is (in terms of time): 60 per cent northerly, 35 per cent southerly, 4 per cent 0, 1 per cent diffuse (ref. 6). It is pointed out that current velocities up to 2.57 m/s have been measured. These data are based on measurements over a 30-year period. As regards the calculations of flow conditions, the design period is mentioned as being short but typical (ref. 3, p. 7). However, what is typical here can only be the direction, not the velocity. On the surface, it would seem laudable to choose atypically low current velocities in order to ensure the least favourable basis for calculations of effects on water quality. However, other parts of the background material note that: "The blocking effect is greatest at high-volume flow". (ref. 3, p. 4), and that "The greater the current velocity, the more significant is any change of hydraulic resistance". (ref. 7, p. 4) This is likewise illustrated by the following figure simulating the flow across Drogden during the design period. Fig. 4:The figure shows the flow across Drogden (ref. 19, fig. 10). [only available in print edition] Fig. 4 shows that the deviation between the different cases does not become apparent until the flow, and thus the current velocity, reaches a certain level. ------- case 5 (flat dredging) ....... case 4 (without compensation) _______ case 1 (present conditions) This emphasizes the significance of the design period in determining the increase of resistance caused by the construction of the bridge. As the flow is an important factor in a simulation of flow alterations caused by the establishment of the fixed link, the light current conditions employed in such a simulation raise serious doubts about its results. Thus, there is reason to suspect that the actual resistance of the bridge is greater than 1.2 per cent, and that the removal of 11.5 mill. m3 of seabed will not reduce the resistance to one-third. CASA has, in an earlier report, pointed to the significance of the light flow conditions of the design period, and this has lead to queries by the Parliamentary Transport Committee concerning the justification of the design period chosen. The subsequent replies have merely reiterated the claim of the background reports: That the design period was chosen on the basis of the least favourable conditions for water quality in the Baltic, where the oxygen content is low due to inadequate water exchange. However, no explanation has yet been given as to why the same period of weak flow conditions is applied to elucidate the changes the bridge would otherwise cause (ref. 13, pp. 2-3). 6. Possible consequences of changed current conditions The application of weak current conditions in the simulation of the bridge's impact reveals a certain lack of knowledge as to which areas will be particularly susceptible to change when the bridge is established. In the afore- mentioned report, CASA has noted that the currents around the Middelgrund show increasing tendencies even at slight flow velocities. As will be seen from the following differential plotting (Fig. 5), there are, even at the highest current velocities applied (0.7 m/s), increased velocities near the Middelgrund. However, the yearly mean value for northerly currents is, as mentioned, 0.79 m/s, indicating that the current velocity is often higher. This may imply that under unfavourable conditions, the bottom of the Middelgrund would be churned up and eroded. This is unfortunate, as great volumes of sludge contaminated with mercury, originally dredged in the port of Copenhagen, are deposited here. According to the environmental authorities, the sludge dumped at Middelgrund may contain up to 16 tons of mercury (ref. 14). For this reason, fishing of non-migratory fish species (e.g. flounder) is prohibited in this area. Were this mercury to be dispersed, this prohibition would have to be extended. Fig. 5:The figure is a differential plotting. This means that areas which are covered by dots are not affected before or after the establishment of the link. The lines are velocity vectors the length and direction of which indicate changes in velocity and direction caused by the construction of the bridge. This plotting concerns the so-called alignment 2, with flat dredging corresponding to current conditions prior to the establishment of the link. (ref. 3, fig. 23) While it is not certain that this area will be eroded away, preliminary studies carried out to date indicate a lack of knowledge of changes in flow conditions at high current velocities. In a reply to the Parliamentary Transport Committee, the Agency of Environmental Protection claimed that the Middelgrund would not be affected by the bridge link (ref. 13, pp. 3-4). This claim was motivated by a figure containing so-called isolines, indicating limits for changes in current velocities. This figure, however, is far less detailed than the differential plotting above. Moreover, it was based on the weak current conditions of the design period already mentioned. Thus, the reply does not give any idea of the changes which would occur under stronger (normal) current conditions, and therefore no indication of whether the Middelgrund will be affected by the bridge. The establishment of the fixed link on the present basis thus amounts to "groping in the dark", at least from an environmental point of view. New studies, carried out under more realistic flow conditions, may do away with some of the uncertainties; but according to the laws of physics, the results of such studies will, under most circumstances, reveal adverse environmental consequences, apart from oxygen conditions in the Sound. As far as the marine environment is concerned, the combined link is therefore far from environmentally neutral. 7. Sediment dispersal caused by dredging operations The sediment dispersal is presumed to be concentrated around construction and dredging sites. However, this is only realistic when applying the afore- mentioned design period. It should be added that even under light flow conditions, the sedimentation area would extend relatively far to the north (ref. 8, p. 5). It is quite possible that prolonged periods of strong northerly current will cause the sediment shadow to form a 'plug' between Helsingr and Helsingborg. We shall return to this later with an overall elaboration on the impact of the sediment dispersal on the environmental conditions in the Sound. In the official report, the dispersal is calculated on the basis of a total sediment spillage of 5 per cent, which narrows the choice of tools to excavators and bucket dredgers. The latter method must be regarded as unsuitable for operation in the hard limestone layer (ref. 9, p. 7). This leaves 3 dredging methods, i.e. back-hoe excavator, grab dredger, and suction cutter. All these methods give varying degrees of spillage depending on how they are operated and how strong the currents are in the area concerned. DHI presents two possible solutions: "1. Dredging by suction cutter and transportation of the material to an island or landfill. Washed-out fine particles are deposited in sedimentation basins with sufficient holding time to retain the silt fractions. 2. Dredging by back-hoe excavator and transportation of the material to an island or landfill by hopper. Alternatively, all dredged material is deposited at an aquatic dumpsite". (ref. 9, pp. 8-9) Fig. 6: The figure shows the net sedimentation in the final phase of the dredging period. (ibid.) Rules exist for the conditions under which the dredging operations must take place. They include mixing in order to ensure recovery, optimum concentrations, etc. As mentioned, the report considers dredging by suction cutter to be environmentally acceptable, provided sedimentation basins are used. The report also considers that environmental pollution during the dredging process itself can be minimized by means of various types of curtains (ref. 9). However, this is not consistent with experiences from the construction of the Great Belt bridges, where sediment spillages of up to 45 per cent were ascertained (cf. 'Ingeniren', 1st March 1991). Furthermore, it appears from a memorandum by experts from a Dutch contracting company (ref. 10) that sedimentation of dredged material is not the only problem. Considerable volumes of waste spoil will be left behind by the cutter; cf. the following: "Approximately a quarter to a fifth of the material being cut loose or disintegrated by the rotating cutter is left behind on the bottom as spill. This relatively loose material is due to be eroded rather easily by currents and may be the cause of long term dispersion". (ref. 10, p. 15) This is due to the fact that the cutter head usually breaks up more bottom material than the suction pipe can manage to suck up. Danish advisers recommend the use of the afore-mentioned curtains in order to prevent this spillage. However, the contractors do not share this opinion: "Mitigating measures such as placement of silt curtains are not very practical around a cutter suction dredger and not very effective because the largest amount of dispersed soil is present near the sea bottom". (ibid.) According to this source, this dredging method is unreliable at increased flow velocities, because the current will disperse the waste spoils. Considerable spillage has indeed been experienced in construction of the Great Belt bridge. A/S Storeblt has stated that the construction of the two artificial islands which are to hold the anchor blocks of the elevated bridge entails an average spillage of 27 per cent (ref. 11). 8. Environmental consequences of sediment spillage The extensive dredging operations will disturb fish and fauna. This is because the considerable spillage creates 'clouds' of sediment (fine clay and silt particles) which will 'shade' from the light the plants and organic material which consume large quantities of oxygen upon decomposing. This spillage, when settled, will cover and suffocate a large proportion of the fauna present on the bottom. As these 'sediment plumes' are dispersed by the current over large areas, they will affect the bottom fauna of a considerably larger area than the dredging site itself. Experiences from the Great Belt indicate that e.g. the common mussel is seriously disturbed by dredging operations. Thus, the entire 1990 year class is missing. This has led to a reduction of the mussel stocks of 80 per cent and 20 per cent near Sprog and Halsskov respectively. As the common mussel is the most important food of the eider, the bird population on Saltholm will also be affected by the dredging operations. Moreover, the sediment plumes will frighten not only the non-migratory fish species of the Sound but also for example the herring species crossing and/or staying in the Sound during their migrations between spawning and feeding grounds. If the migrations of these fish species are disturbed it may lead to their total disappearance from surrounding waters. Apart from this, dredging operations will be conducted near bottom areas which are vital spawning and nursery grounds for many fish species, and important foraging sites for numerous species of birds living on Saltholm. This applies especially to grasswrack meadows and mussel beds to the south-west of Saltholm. Fig. 7:Bottom fauna in the proximity range of affected areas. (ref. 2, p. 46) As shown in Fig. 6, important areas will be affected by compensatory dredging as well as by the components of the link. Even greater areas will be impacted if the Swedish demand for a true zero solution is to be realised, as the 11.5 mill. m3 referred to are insufficient to attain this objective. The background material predicts that the affected mussel banks etc. may be expected to re-establish themselves after construction is concluded (ref. 2, p. 6). Comparison with the Great Belt operations is not yet possible, as the bottom here is still lifeless after the dredging operations (cf. Greenpeace video, May 1991). But the re-establishment of the original fauna must be considered to be more difficult in the Sound, particularly where flat dredging is undertaken. This dredging activity will uncover extensive limestone deposits upon which fauna cannot fasten. Furthermore, these limestone deposits are of varying hardness. Once dredging operations have been conpleted, some areas will therefore continue to erode for a long time. This will lead to sediment plumes and, consequently, further affect fish and fauna in the surrounding waters. Flat dredging will uncover an expanse of 4.2 km2 of limestone (ref. 2, p. 45). If the limestone deposits are easily soluble, sediment plumes caused by the subsequent erosion may well prove as harmful as the dredging activity itself. 9. Immersed tunnels - an environmental alternative? Because of the afore-mentioned environmental consequences, alternative projects which may reduce these disadvantages have been proposed from several quarters. Two proposals have been given urgent attention by the DSB [Danish State Railways] and the Road Directorate. These proposals are based on economic as well as environmental considerations. Staff members of the consultancies DHI and LIC, which are responsible for the major part of the source material of this report, mention that: "From an environmental point of view, the tunnel solution is attractive by virtue of its reduced interference with the water flow. If the tunnel is carried the whole way across under Drodgen and Flinterenden, compensatory dredgings can be reduced or even completely avoided, with consequent environmental and economic advantages". (ref. 15) It appears from this that the argument in favour of the proposal of an alternative solution is founded on the environmental effects emphasized in the present report. However, this is not reflected in the proposed alternative. With respect to the stretch from Amager to the artificial island, the proposal corresponds to the afore-mentioned KM.4.2 project. But here the similarity ends. The artificial island would be extended from 2.5 km to 4.75 km, allegedly for economic reasons (ref. 15). This would lead to a further reduction of the water flow as compared to KM.4.2, and would therefore require even more extensive compensatory excavation. The alignment continues after the artificial island as an immersed tunnel (ref. 16), thus avoiding the friction which would be caused by the bridge piers of KM.4.2. In the combined bridge/tunnel solution, however, the bridge piers are responsible for only one-third of the total friction, whereas the bridge platforms on Amager and the artificial island constitute 67 per cent of the total friction of the construction (ref. 2, p. 13). A 90 per cent extension of the artificial island in this tunnel project will constitute a solution even more unacceptable solution than KM.4.2, despite the shallow depth at which the island is situated. This is not only due to the increased friction caused by the island, but also the additional dredging activities required for the construction of the immersed tunnel. Such activities will aggravate the environmental disturbances caused by the already unacceptable construction and compensatory measures, and would, as mentioned, be of far greater proportions due to the size and consequent blocking effect of the island. Moreover, the artificial island will cover an even larger proportion of the bottom fauna which is of vital importance for birds as well as for fish. Therefore the project is, from an environmental point of view, totally unacceptable. However, yet another project proposal has been submitted to the Minister for Transport in which the artificial island is left out altogether, thus considerably reducing construction-induced friction, while at the same time covering much smaller areas of important bottom fauna (ref. 16, pp. 13-19). The Ministry of the Environment has criticised this project, firstly because the large volumes of bottom sediment to be removed (8 mill. m3, ref. 16, p. 17) cannot be directly used in the construction and so will have to be dumped (deposited), and secondly because it is estimated that 80 per cent of the material will be limestone. Thus, it must be expected that: "... an environmentally appropriate handling of the volumes removed might prolong the construction time considerably. Dredgings over a longer period of time might therefore have greater negative effects on biological conditions, including fisheries in the Sound". (ref. 16, p. 17) The concern with dredging in the limestone layers is explained in further detail in a memorandum presented by the Parliamentary Transport Committee (ref. 17, pp. 3-4). CASA shares this concern, but notes that this apparent scepticism towards dredging in limestone has not been taken into account in the environmental studies of KM.4.2, even though this project requires the excavation of at least 6.2 mill. m3 of limestone in order to secure a zero solution for the Baltic Sea. As 80 per cent of 8 mill. m3 corresponds to 6.4 mill. m3, the difference between the two proposed projects, in terms of limestone dredging operations, is 0.2 mill. m3. However, this compares the entire tunnel project to the compensatory dredging for KM.4.2. To the latter project must be added dredging for the 2 km long immersed tunnel under Drogden. On the assumption that the volume of limestone to be excavated for these 2 km corresponds to the 6.4 mill. m3 to be handled in the tunnel project's 14.4 km, a further 1.11 mill m3 must be added to the compensatory dredging of 6.2 mill. m3 for KM.4.2. The adopted alignment thus requires the excavation of at least 7.3 mill. m3 of limestome; or 0.9 mill. m3 more than the amount which renders the tunnel solution problematic. This is assuming that a zero solution for the Baltic Sea, as demanded by Sweden, is to be achieved. A proposal for KM.4.2 exists whereby the compensatory dredging is reduced by lengthening the tunnel (ref. 18). This, however, will be of no appreciable significance if limestone is the problem. If the tunnel is extended, additional excavation in the limestone layer will be required in order to accommodate the tunnel. The new projects do not indicate whether the concern with excavating in limestone is prompted by the fact tunnel excavation will encounter different types of limestone (deeper layers) than will flat dredging. ********** 10. The Greenpeace View by Jesper Grolin, Greenpeace International As has been shown, the official assessment of the environmental impact of the proposed KM. 4.2. solution leaves a number of questions open. They concern both the exact nature and extent of the environmental impacts and the choice between such impacts. The CASA report shows that none of the compensatory measures considered leave the Baltic unaffected. Hence, in Greenpeace's view, it is important for the HELCOM Environmental Committee to request clarification on exactly what the effects of the various compensatory measures will be and, subsequently, to advise the Danish and Swedish governments on the acceptability of these measures. In Greenpeace's view, the Swedish demand for a zero solution must constitute the point of departure for the considerations by the HELCOM Environmental Committee. Given the present state of knowledge, Greenpeace finds that only a bored tunnel can fulfil the requirements for a zero solution. Hence, Greenpeace finds it odd indeed that a bored tunnel is the only option for a fixed link across the Sound which has not been considered in the context of the present Danish-Swedish agreement. Between the two options which have been considered, namely an immersed tunnel and a combined motorway/railway bridge, an immersed tunnel is - as also shown in this report - clearly the lesser of two evils environmentally. Hence, the fact that such a tunnel solution has been rejected by both the Danish and Swedish governments can only be taken to mean that the two governments assign secondary priority to the protection of the Baltic environment in the establishment of the fixed link across the Sound. This is not only a contradiction of the Precautionary Principle, according to which the environment should always be given the benefit of the doubt. It is also a violation of the commitment undertaken in the 1990 Baltic Sea Declaration to do everything possible to restore the ecological balance of the Baltic. References 1. Milj resund, 1991 [Environment, the Sound, 1991] Trafikministeriet [Ministry of Transport] 2. Vurdering af ndret [Evaluation of modified liniefring layout] COWI/VKI, Jan. 1991 3. Miljhydraulik - Del 4 [Environmental hydraulics - part 4 (Liniefring 2) (layout 2)] COWI/VKI, 11. Jan. 1991 4. stersens vandmilj [Aquatic environment of the Baltic] COWI/VKI, Dec. 1990 5. Miljhydraulik - Del 4 [Environmental hydraulics - part 4] COWI/VKI, 12. Nov. 1990 6. Frigivelse af metaller [Liberation of metals from fra sediment .... sediment ....] DMU, 1990 7. resundsforbindelsen: [The Link across the Sound: Stormflodsanalyse analysis of floods] DHI, May 1991 8. Sedimentspredning [Sediment dispersal] MIKE 21 TD DHI/LIC, 1990 9. Vurdering af udfrel- [Evaluation of methods in relation sesmetoder i.f.t. to environmental impacts] miljpavirkninger DHI/LIC, 1990 10. Environmental impact of dredging operations Delft, June 1988 11. Storeblt og miljet [The Great Belt and the environment] Storeblt, April 1991 12. Beregning af kompen- [Calculations of compensation sationsafgravninger deepenings and their effect og effekten p ster- on the hydrography of the sens hydrografi Baltic] DHI/LIC, 1990 13. Svar til Trafikudvalg [Reply to Transport Commission L 178, bilag 67 L 178, appendix 67] Trafikministeriet, [Ministry of Transport] 28. May 1991 14. Kvikslv i sediment i [Mercury in sediment in the Kbenhavns havn harbour of Copenhagen] VKI, 1987 15. Berlingske Tidende, [Daily newspaper] 18th June 1991: Indlg, J.S. Mller & [Article by J.S. Mller N.E. Ottesen Hansen & N.E. Ottesen Hansen] 16. Oversigt over diverse [Review of various proposals forslag for fast for- for a permanent link across bindelse over resund the Sound] Miljministeriet, [Ministry of Environmental 26. June 1991 Protection] 17. Notat L 178 bilag 187 [Memorandum L 178, appendix 187] Trafikministeriet [Ministry of Transport] 18. Supplerende bereg- [Supplementary calculations ninger af kompensa- of compensation deepenings ...] tionsafgravninger ... COWI/VKI, 26. Feb. 1991 19. DHI/LIC Engineer- [Concept studies marine env./ ing A/S marine biology/hydraulics Konceptstudier Part 4, Flow conditions, Havmilj/marin- 1990] biologi-miljhydro- lik, del 4, Strmfor- hold, 1990 20. DSB/UD: Modelbe- [DSB/UD: Model calculations regninger af of the effects on oxygen effekten p conditions in the Sound, iltforhold i 1990.] resund 1990 21. resundsfor- [Fixed links across the bindelser, CASA, Sound, CASA, May 1991] maj 1991 22. resundsfor- [The environmental impact bindelsens milj- of the fixed link across konsekvenser, the Sound, CASA 1991] CASA, 1991