MILJÖREDOVISNING BILAGA 12

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1 MILJÖREDOVISNING BILAGA 12 ASSESSMENT OF NAVIGATIONAL RISKS IN THE SWEDISH SOUTHERN SECTOR FOR NORD STREAM 2 ROUTES DOCUMENT ID:

2 Sweden s REPORT Date: Nord Stream 2 AG Reference: Peter Klockar SSPA Report No.: RE C Nord Stream 2 Report No.: Project Manager: Nelly Forsman Nelly.forsman@sspa.se Author: Nelly Forsman Björn Forsman Assessment of Navigational Risks in the Swedish Southern Sector for Nord Stream 2 Routes Nord Stream 2 AG is currently performing the preliminary engineering for the development of the Nord Stream 2 (NSP2) project. This consists of a future major offshore gas transportation system through the Baltic Sea between Russia and Germany with many similarities to the Nord Stream Project. NSP2 comprises the installation of two large diameter pipelines. In connection to the permit process of NSP2 in the Swedish sector, an assessment of potential navigational risks has been conducted. This report summarizes the findings and more extensive descriptions of corresponding main chapters are found in the appendices. AB SSPA Sweden AB Joakim Lundman Assistant Manager Maritime Operations Nelly Forsman Project Manager Maritime Operations SSPA SWEDEN AB YOUR MARITIME SOLUTION PARTNER HEAD OFFICE: P.O. Boa SE Gdteborg Sweden Tel: +46 (0) Fax: 46 (0) VISITING ADDRESS: Chalmers Tvdrgata 10 SE Gateborg. Sweden BRANCH OFFICE: Fiskargatan Stockholm. Tel: +46 (0) Fax: ) INTERNET: postmaster@sspa.se VAT NO: SE

3 Summary and recommendations The two existing Nord Stream pipelines, NSP1 have been in operation since 2011 transporting natural gas from Russia to Germany. Additional pipelines along the existing pipeline route are currently being investigated by Nord Stream 2 AG. As part of the application and permit process, the company has commissioned SSPA Sweden AB to conduct a maritime safety assessment of navigational risks in the Swedish southern sector for the NSP2 route. The planned NSP2, with two large diameter pipelines running parallel to the NSP1 pipelines, may be routed west or east of the existing NSP1 pipelines in the southern sector of the Swedish EEZ. SSPA has compared the two options, focusing on possible indirect risks imposed to navigating vessels by the presence of the pipeline. In particular potential delay of emergency anchoring of drifting vessels that have lost propulsion due to technical failure are addressed. Direct risks imposed by ships to the pipeline are not addressed. The present sea traffic situation is described thorough analysis of AIS data recorded in This data is combined with established trends and predictions to form a credible prognosis for the DW route ship traffic in The methodology applied in the study includes qualitative as well as quantitative modelling and calculations. A hazard identification workshop has been conducted for identification of possible hazards and risk scenarios. Systematic simulations of emergency anchoring have been performed with the SEAMAN software and the results are presented in track plots and time history diagrams. An event tree model is also prepared and presented to illustrate possible casual chains behind potential drifting grounding accidents and associated probabilities. Various, existing or possible future risk control options have been identified and included in the event tree model. The event tree model is also applied to illustrate effects of uncertain assumptions and modelling and to show the sensitivity of various model parameters. The output of the quantitative calculations indicates that the addressed indirect risks related to drifting grounding due to delayed emergency anchoring are very low. The comparative analysis between the present situation and a future situation with the planned NSP2 pipelines in place, clearly demonstrates that identified possible indirect maritime risks related to potential delay of emergency anchoring, will not be influenced. The simulations of emergency anchoring conducted as part of the risk analysis, show that there will be more than enough of time, available drifting distance, and favourable anchoring conditions for safe emergency anchoring within the designated emergency anchoring zones in leeward positions of the planned pipeline route. Comparative analysis of the two NSP2 route location options, show that the western option would affect areas with more favourable anchoring depth leeward of the existing pipeline, whilst the eastern option essentially influences areas with larger depth and less attractive anchoring areas windward of the pipeline. The eastern route option is thus recommended with respect to the indirect maritime risks addressed. 2 (38) SSPA Report No.: RE C

4 Table of contents Summary and recommendations Introduction Background Objective and scope Limitations Methodology Traffic analysis AIS-analysis of Potential grounders Traffic prognosis Hazard identification Hazid Addressed risks Accident statistics Identified risks imposed by NSP2 and comparative routing considerations Risk analysis Anchoring simulations Start positions Anchoring strategy Drifting and emergency anchoring simulations Results Quantitative analysis of grounding probability Probability of machinery failure Drift direction predominant wind direction Potential grounders Self-repair Failure of emergency anchoring Existing pipeline presence as hindrance for anchoring Potential impact of additional NSP2 pipelines along the existing Nord Stream Risk Control Options, RCO Comparative aspects of NSP2 route location options Designation of pipeline protection zone Emergency Towing Vessel, ETV Uncertainties and sensitivity analysis Basic comparative conclusion and quantitative risk modelling Sea traffic analysis and predicted future traffic (38) SSPA Report No.: RE C

5 6.3 Simulation of emergency anchoring Quantitative event tree modelling Sensitivity analysis Conclusion and recommendations References Appendix 1 Traffic analysis Appendix 2 Hazard identification Appendix 3 Anchoring simulations Appendix 4 Event tree 4 (38) SSPA Report No.: RE C

6 1 Introduction Since 2011 natural gas is transported through the offshore gas transportation system Nord Stream from Russia to Germany. The pipelines are routed on the seabed of the Baltic Sea and in Swedish Exclusive Economic Zone (EEZ) east and southeast of Gotland, see Figure 1.1. Additional pipelines along the existing pipelines are currently being investigated by Nord Stream 2 AG. The planned second pipeline project, NSP2, comprises the laying of two large diameter pipelines with many similarities to the existing Nord Stream project, NSP1. Figure 1.1 The Nord Stream route from Russia to Germany and the alternative routes for Nord Stream 2 which are now being investigated. 1.1 Background An extension of the Nord Stream pipeline system was first considered in 2012 and during the initial public consultations in 2013 the Swedish Agency for Marine and Water Management, the Swedish Transport Agency and the Swedish Maritime Administration expressed the need to assess the risks and consequences introduced by the presence of the two new pipelines along the buffer zones in proximity of Hoburgs Bank and Norra Midsjöbanken. The buffer zones are identified as areas designated for emergency anchoring between the deep water route and the banks. Results from a similar study performed for the first Nord Stream project indicated that the presence of the pipeline may influence the decision making of the master of a drifting vessel on where and when to find an appropriate place for emergency anchoring. 5 (38) SSPA Report No.: RE C

7 In 2012, when an extension project first was initiated, several alternative routes were considered. Since then Nord Stream 2 has performed a comprehensive route screening exercise. Based on considerations concerning e.g. environmental constraints, existing and planned infrastructures, ship traffic, munitions dumping sites, military areas, fishery, cultural heritage sites and seabed bathymetry, the number of routing alternatives have been reduced and now consist of two corridors in the area southeast of Gotland. Both corridors are broadly parallel to the existing NSP1 route, one on the east side of the existing pipelines and one on the west side. Figure 1.2 shows the centrelines of the two alternative corridors in the area southeast of Gotland. Figure 1.2 Sea chart of Swedish EEZ southeast of Gotland. The centrelines of the alternative Nord Stream 2 corridors are marked in green and blue. The existing gas pipelines are marked in pink. The dotted pink line west of the existing gas pipeline is a newly deployed telecom cable, Sea Lion. 1.2 Objective and scope The current risk analysis shall identify and analyse the indirect risks to the ship traffic triggered by the presence of the NSP2 pipelines along the Hoburgs Bank 6 (38) SSPA Report No.: RE C

8 and Norra Midsjöbanken. Based on the outcome of the previous study of indirect risks, the potential influence of the NSP2 pipelines presences on the decision making of the master of a drifting vessel on where and when to find an appropriate place for emergency anchoring is investigated particularly. Further risks identified in connection to NSP2 are assessed in relation to their assumed potential significance. The study is carried out for two alternative corridors with a width of m each. The specific positions within the corridor have not yet been specified and for the present study it is assumed that the NSP2 pipelines can be laid in any location within the relevant corridor. However, since NSP2 aim to route close to the existing pipelines a realistic worst case routing within the corridors is investigated. The nominal distance between the two NSP2 pipelines within the corridor is at this stage defined to be approximately 100 m Limitations Direct risks to the pipeline from ship-related threats, such as dropped objects, dropped anchors, dragging anchors and sinking ships are not within the scope of work. The study is limited to analyse the indirect risks to the ship traffic triggered by the presence of the NSP2 pipelines. The geographical area of analysis is restricted to the area between Hoburgs Bank and Norra Midsjöbanken southeast of Gotland in the Swedish EEZ. 1.3 Methodology Results from the previous study from 2009 of navigational risks of the existing Nord Stream pipelines have been used to identify possible changes of indirect risks and form basis for the current study. The risk assessment has been carried out as a risk analysis, following established risk analysis standards and according to the Formal Safety Assessment (FSA) methodology in applicable parts, see Figure 1.3. However, components related to cost benefit analysis are not included in the present study. The study is based on a traffic analysis where AIS data of vessels passages in the area in 2014 is used to form the basis for predicted traffic scenarios expected for The hazard identification phase included a Hazid-workshop where representatives from relevant authorities and relevant expertise participated. The reported risk identification process is followed by a qualitative analysis of probabilities and consequences. The analysis is supported by simulations of drifting vessels in order to investigate emergency anchoring situations and the potential impact of the NSP2 pipelines. Simulations were conducted for routing in both the western and eastern corridor in order to identify the most favourable route with respect to the impact on shipping. Possible risk control 7 (38) SSPA Report No.: RE C

9 options are identified and their potential effect to reduce risks is estimated. Based on the results, recommendations and conclusions are formulated and presented in the report. Formal Safety Assessment Definition of system subject to risk assessment Establishing the context, study basis Frequency/probability analysis Preventive measures Hazard identification Possible accidents scenarios Risk assessment Risk control options Cost-benefit assessment Consequence analysis Consequence reducing mitigating measures Risk evaluation, acceptance criteria, regulations, policies Ship traffic analysis and prognosis for 2025 AIS analysis, predicted development, and trends for 2025 Identification of possible maritime risks Hazid-workshop Accident statistics, pipeline damage incidents Emergency anchoring and groundings Quantitative analysis of grounding probability Event tree modelling Simulation of loss of propulsion, drifting and emergency anchoring and dragging Identification and evaluation of possible measures to reduce risks Cost-benefit not included in the current study Risk comparison with and without the new pipeline Results and recommendation Conclusion and recommendations Uncertainties and sensitivity analysis, and recommendations Figure 1.3 General structure of risk analysis and its application for the present study. 8 (38) SSPA Report No.: RE C

10 2 Traffic analysis Swedish Maritime Administration (SMA) compiles AIS data and publishes annual statistics on ship traffic as number of crossings at specific passage lines in Swedish waters. Figure 2.1 shows the number of ship passages in 2014 across passage lines near the area addressed by the current study. Figure 2.1 Number of ship passages in 2014 across SMA s passages lines in the area around Öland and Gotland (SMA, 2016). From the figure, it can be concluded that the main part of the ship traffic east of Gotland is passing in the fairway north of Hoburgs bank and Norra Midsjöbanken. This fairway is limited in depth and vessels having a draught of more than 12 m are therefore recommended to use the designated deep water (DW) route south of the banks. For the current study, the traffic in the DW route, crossing the passages line at Midsjöbankarna and Hoburgs bank DW, are considered to be of main interest. The graph in Figure 2.2 shows that the number of passages at Hoburgen- Hoburgs bank (purple) has decreased slightly during the last years, while the number of passages in the DW-route (Midsjöbankarna and Hoburgs bank DW) has increased slightly, except for (38) SSPA Report No.: RE C

11 Number of passages Gotland-Latvia Midsjöbankarna Hoburgs bank DW Hoburgen-Hob. bank Ölands södra grund Figure 2.2 Historical trend of number of passages across the passage lines around Gotland. The fairway north of the banks is preferred by most ships as it is the shortest route across the Baltic Sea. Large tankers, container vessels and large cruise ships are directed to the deep water route. The largest tankers operating in the Baltic Sea are Aframax with a draught of about 15 m when loaded. These are mainly calling Russian ports in the Gulf of Finland. Hence, these are loaded when heading south in the deep water route east of Gotland. 2.1 AIS-analysis of 2014 AIS data from 2014 have been extracted to calculate the number of passages at six different passage lines specifically defined for this study, see Figure 2.3. Passages across line 4 and 5 represent the traffic in the DW route and is of main interest for the current study. 10 (38) SSPA Report No.: RE C

12 Number of passages Figure 2.3 Traffic in 2014 crossing six defined passage lines (marked 1-6) in the areas around Norra Midsjöbanken and Hoburgs bank. The diagram in Figure 2.4 shows that the traffic is more intensive in the route north of the banks, across line 2 and 6. The southbound traffic in the DW route, line 4 and 5, is higher than the northbound. The opposite is valid for the shipping lane north of the banks, across line 2 and 6. This reflects the fact that the main part of the large vessels, particularly oil tankers, enters the Baltic Sea in ballast and leaves the Baltic in laden condition, passing the DW route southbound South bound North bound South bound North bound South bound North bound South bound North bound South bound North bound South bound North bound Bulk carrier Container vessel General cargo Ro-Ro Tanker Passenger Other Figure 2.4 North respectively south bound traffic across the passage lines defined in Figure (38) SSPA Report No.: RE C

13 2.1.1 Potential grounders The number of vessels that theoretically may be subject to drifting grounding on the banks, and hence the vessels that potentially could be affected by the presence of Nord Stream 2 pipeline in case of loss of propulsion and emergency anchoring, have been estimated in terms of potential grounders. According to the sea chart, the smallest depth at Hoburgs bank is 10.3 m and 9.3 m at Norra Midsjöbanken (SML 1945) (Swedish Maritime Administration, 2010). To take account for sea level variations as well as heel and roll motions of the vessels, a conservative margin of 1.3 m is applied for identification of the so-called potential grounders. For passage line 4, south of Hoburgs bank, vessels with draught larger than 9 m are identified as potential grounders. For Norra Midsjöbanken, line 5, vessels with draught larger than 8 m are identified as potential grounders. Based on data recorded in 2014 the number of potential grounders at Hoburgs bank were and at Norra Midsjöbanken, see Figure Bulk carrier Line 4 Container vessel General cargo Ro-Ro Line 5 Tanker Passenger Other Figure 2.5 Potential grounders, i.e. number of vessel passages with a draught larger than 9 m at passage line 4 and 8 m at passage line Traffic prognosis 2025 In a global perspective, an increased demand of seaborne transport work is likely to be partly handled by larger, more transport efficient ships that are capable of carrying larger quantities of goods (Trafikanalys, 2014). The anticipated increase in number of calls, and thereby passages, are hence restricted. However, the size of vessels entering the Baltic Sea is constrained mainly by the limited depth in the Kadetrenden, allowing a maximum draught of 14.5 to 15 m. The largest tankers that can transit the Kadetrenden fully loaded are of Aframax type with a carrying capacity of to tonnes. Since the overall size of vessels is increasing, it can be assumed that the 12 (38) SSPA Report No.: RE C

14 number of Aframax tankers will increase in the Baltic Sea, whilst the number of smaller tankers will decrease as result of economy of scale. Ramböll (Ramböll, 2016) has forecasted a continued trend towards larger ships with growth in most ship type segments until Growth in the cargo segment is predicted by 4% annually. Passenger and other sectors are also forecasted to follow the trend to 2025 with growth rates of 3.4% and 1.4% annually. Only tankers are forecasted a marginal decrease in frequency in the large ship segment (-0.4% growth). This decrease is due to the trend towards larger vessels, in combination with a weakening demand for oil import in Europe and a shift in Russian export through ESPO pipeline to Asian markets. The growth rates are based on the available AIS data to which statistical extrapolations were undertaken. Secondly, the growth rates as applied in the BTO (Baltic Marine Transport Outlook) 2030 model were applied to the various shipping sectors with 2014 AIS data serving as a base year. In order to derive a credible traffic scenario for 2025 in the area around the banks, the growth rates estimated by Ramböll have been applied to the traffic recorded at the six defined passage lines. Ramböll does not specify any specific figures for bulk carrier, container vessel, general cargo and Ro-Ro vessels, instead these are all expected to have the same growth rate; 4% as outlined for the cargo segment by Ramböll. Table 2.1 shows the predicted number of passages across the passage lines in Table 2.1 Forecasted traffic 2025 across the six passage lines, based on Ramböll's predicted growth rates with 2014 as a base year. Percentages increase compared to 2014 in parentheses. Number of passages Total (+37%) (+42%) 730 (+50%) 8804 (+26%) 8892 (+26%) (+43%) Bulk carrier Container vessel General cargo Ro-Ro Tanker Passenger Other With regard to the trend towards larger vessels and economy of scale effects, it is deemed reasonable to assume that the main part of the increase in number of container vessels will occur among the largest vessels. It is also reasonable to assume that vessels taken out of service may be replaced by larger vessels Even though the total number of tankers are expected to decrease, the number of large tankers are expected to increase. Based on these assumptions, the number of potential grounders is expected to increase until However, the size is restricted and no significant increase in maximum size is therefore 13 (38) SSPA Report No.: RE C

15 expected. As a conservative assumption, it is assumed that the main part of the increase of ship passages across line 4 and 5 will be potential grounders. The number of potential grounders in 2025 is thereby estimated to at Hoburgs bank and at Norra Midsjöbanken, implying an increase of about 35% from For the quantitative calculations in the event tree model an average of the value from both passage lines are used and in addition, northbound ships are also included in the total number of potential grounders. More detailed information on the traffic analysis is found in Appendix (38) SSPA Report No.: RE C

16 3 Hazard identification 3.1 Hazid The hazard identification or Hazid is the first step in the Formal Safety Assessment (FSA) process and its objective is to identify all potential hazards and risk scenarios associated with the planned activity. For this specific study, the Hazid partly relies on experience from corresponding risk assessment components conducted during preparations for the first Nord Stream pipeline project in 2009 (SSPA, 2009), but is in particular addressing potential hazards or altered risks related to the planned NSP2 project and its routing. Baseline conditions for the Hazid are reflected by today s conditions including the presence of the existing Nord Stream pipeline NSP1 and the Sea Lion cable, and proposed alternatives include optional routings of the NSP2 east or west of the corridor formed by the NSP1 and the Sea Lion cable. For each of these options, the NSP2 may be located at different distances (minimum 500 m) from the existing NSP1 or from the cable. The hazard identification component of this study included a Hazid workshop with invited expertise representing a wide range of relevant authorities and experienced navigators. More detailed information on the Hazard identification is found in Appendix Addressed risks Maritime risks associated with pipeline projects are categorised in two main categories: Direct risks imposed by ships to the pipe line, e.g. pipeline damage caused by dragging anchors or sinking ships. Indirect risks are risks that are imposed to navigating vessels by the presence of the pipeline and may e.g. involve cases where the presence of the pipeline delay emergency anchoring of drifting vessels that have lost propulsion due to technical failure. The first category, direct risks, is primarily an issue of concern for the pipeline owner whilst the second category, indirect risks, is related to societal risks and to maritime safety in particular. This navigational risk assessment is a part of the pipeline owner s permit application process and thus exclusively address potential indirect risks occurring when the pipeline is in place and in operation. Direct risks as well as risks associated with pipeline laying operations are covered by others. 15 (38) SSPA Report No.: RE C

17 3.3 Accident statistics No maritime accidents have been reported along the first Nord Stream pipeline where the presence of the pipeline affected the cause of, or the final consequences of the accident. One example of an indirect incident related to emergency anchoring and the presence of a pipeline was reported from offshore installation areas in the North Sea in The cargo vessel Vindö was drifting and dropped anchor to reduce its drifting speed. In order not to damage subsea pipelines the vessel was, however, requested to cut its anchor cables and luckily, it was able to avoid collision with the Caister platform with only 650 m clearance. 3.4 Identified risks imposed by NSP2 and comparative routing considerations At the Hazid workshop, different sections of the addressed DW route were subject to comparative considerations with regard to identified potential hazards and various aspects, such as critical wind directions, NSP2 route location options east or west of existing pipeline, and distance from existing pipeline and cable installation. This comparative analysis indicates that the NSP2 routing option east of the existing pipeline and cable corridor is considered preferable with respect to potential delay of emergency anchoring. This option does not restrict today s available emergency anchoring area in leeward positions of the existing pipeline and cable corridor where the anchoring conditions are considered more favourable than windward the corridor. Compared with routing in the western corridor, routing in the eastern corridor implies that the distance to the banks leeward of the pipeline and cable corridor becomes m longer. Anchoring between the existing pipeline and the planned NSP2 is not considered attractive under any circumstances and in order to make the total width of pipeline zone with anchoring restrictions as narrow as possible, it is considered favourable to locate the routing of the NSP2 as close as possible to the existing pipeline route. With respect to potential delay impact on emergency anchoring, it was thus found that NSP2 routing east of the existing Nord Stream pipeline and Sea Lion cable with a location of the NSP2 at shortest possible distance from the existing pipeline, is the most favourable route option. More detailed information on the hazard identification is found in Appendix (38) SSPA Report No.: RE C

18 4 Risk analysis Simulation techniques are used to model the motions and translation of a drifting vessel and the vessels movements when an anchor is dropped. In this way, distances and duration of drifting and dragging can be estimated. These estimates are valuable when the navigational risks are analysed. 4.1 Anchoring simulations In the present study, simulations were performed using the SSPA software SEAMAN. Simulations have been conducted for two selected types of vessels with different characteristics. Particulars for these are presented below. Oil tanker of Aframax size. Length over all: m Beam: 46.0 m Displacement: m 3 Draught loaded: 15.0 m Container vessel Length over all: m Beam: 32.2 m Displacement: m 3 Draught loaded: 9.0 m The oil tanker is assumed to potentially cause the worst consequences in case of grounding. The container vessel is assumed to have different drifting behaviour and a higher drifting speed due to higher superstructure and container load Start positions Based on the findings in the hazard identification process, four different start positions for drifting and emergency anchoring simulations were identified and selected. All positions are located on the western boundary of the DW route as this implies the shortest distance to the pipeline. The starting positions shall be regarded as the vessels positions when a blackout or rudder failure occur and when it starts drifting. The area around Norra Midsjöbanken is considered more critical than Hoburgs bank due to the shallower water at the bank and shorter distance to shallow peaks from the DW route. Hence, points 1, 2 and 3 refer to the risk of grounding at Norra Midsjöbanken. In the emergency anchoring zone east of Hoburgs Bank, the water depth is deemed to be too large to be favourable for anchoring (>50 m). The presence of the pipeline will therefore not influence a potential emergency anchoring, as it is more beneficial to wait until having reached more shallow water west of the considered routes. Thus, no simulations of blackouts in this area are needed. South of Hoburgs bank, the 17 (38) SSPA Report No.: RE C

19 water depth where the pipelines are to be routed allows for safe anchoring. Point 4 addresses the risk of grounding at Hoburgs bank due to a blackout in this area. Figure 4.1 shows the selected starting positions Figure 4.1 Starting positions for simulations Anchoring strategy In the simulations, several logic conditions are used to decide when to drop anchor. Water depth is smaller than 50m SOG (Speed over ground) is less than 2 knots or vessel has been adrift for more than 1 hour if SOG does not drop below 2 knots. Vessel is not within any of the defined no-anchoring zones, as described in section below. Vessel is not within the DW route. If all conditions are fulfilled, one anchor is dropped according to the following settings: Anchor is walked out with a speed of 1.5 m/s 200 m of cable length is walked out Cable length is fixed to 200 m until end of simulation 18 (38) SSPA Report No.: RE C

20 If one anchor does not manage to stop the vessel, a second anchor is dropped. The no-anchoring zones are related to the existing pipelines, the telecom cable and the potential NSP2 pipelines. It is assumed that the master will apply a safety margin before dropping anchor. The pipelines are assumed to be considered more important and hence introduce a larger safety margin for anchoring than the cable. Based on discussions with experienced mariners, a safety margin of 300 m to the cable and 500 m to the pipelines have been applied in the simulations. In addition, no anchoring is assumed to take place between the installations since the master is expected to rather wait to drop anchor until having pass all installations due to the risk of dragging Drifting and emergency anchoring simulations Drifting and anchoring simulations for several different scenarios have been conducted, see Table 4.1. Table 4.1 Emergency anchoring scenarios and no-anchoring distances applied in simulations. Scenario West side (of NSP1) East side (of NSP1) Anchoring performed on: 1 Only existing assets 800m 500 West side 2 Additional gas pipeline on the east side 3 Additional gas pipeline on the west side 800m 2 100m West side 2600m 500m West side 4 Only existing assets 800m 500 East side 5 Additional gas pipeline on the east side 6 Additional gas pipeline on the west side 800m 2 100m East side 2 600m 500m East side Wind is applied in the model from two different directions, from South (180 ) and from Southeast (135 ). The wind speed is set to the maximum recorded wind speed (23 m/s) at the measurement station at Hoburg, located on the southern cape of Gotland (SMHI, 2016). For position 1 and 4 winds from south have been identified to be of particular interest as this implies drifting towards ground. For position 3 winds from southeast are identified to be of particular interest. For position 2 both winds from south and southeast are identified to be of particular interest. Hence, the emergency anchoring simulations have been limited to these cases Results All simulations are documented with track plots and time-series showing, vessel speed, heading, cable length, anchor mode, distance to existing NSP1 gas pipeline and bottom clearance. All results are found in Appendix (38) SSPA Report No.: RE C

21 In addition to the emergency anchoring scenarios, drifting simulations without anchoring were conducted as reference. Track plots of the drifting scenarios are shown in Figure 4.2 and Figure 4.3. The plots show the vessels movement when drifting during 10 hours. Area to be avoided Figure 4.2 Simulation of tanker (blue) and container vessel (red) drifting in south and south-easterly winds from start position 1, 2 and (38) SSPA Report No.: RE C

22 Area to be avoided Figure 4.3 Simulation of tanker (blue) and container vessel (red) drifting in south and southeasterly winds from start position 4. Table 4.2 summarizes some of the overall results collected from all the time series. Table 4.2 Summarizing results of the simulations. Approximate drifting speed at 23 m/s winds Shortest drifting time to bottom clearance<10 m Dragging distance after 1 h since walk-out of anchor Container 260 m Tanker 266 m 2.1 knots 1.7 knots 6 h 7.5 h <100 m <100 m In general, a ship suffering a total blackout will turn against the wind as the speed is reduced. As it comes to an almost stop it will start to drift sideways with the wind and waves. As the anchor is walked out and starts to dig in on the bottom, the ship experiences a forced heading change so that it points towards the wind and comes to quite an abrupt stop. This is also the time where the anchor is dragging, but as seen in the table above, in no simulation has a ship been found to move more than 100 m from the initial anchoring location during the first hour. In no case has it been necessary to drop the second anchor to stop the vessel from continuing to drift. Figure 4.4 shows the plots of scenario 3 from 21 (38) SSPA Report No.: RE C

23 position 3. Scenario 3 implies that the additional gas pipelines are located in the western corridor. This scenario and position minimizes the area available for anchoring leeward of the pipeline before reaching the area to be avoided. The anchor is dropped 500 m leeward of NSP2 located in the western corridor and with a distance of m to NSP1. Area to be avoided Figure 4.4 Scenario 3, tanker (blue) and container vessel (red) drifting from position 3, emergency anchoring leeward of Nord Stream 2 located in western corridor. More detailed information on conducted simulations of emergency anchoring is found in Appendix Quantitative analysis of grounding probability A drifting grounding accident would be a result of a chain of events where all separate components turn out in an undesirable way, Figure 4.5. An event tree of a drifting grounding accident including probabilities of each event is outlined in Appendix (38) SSPA Report No.: RE C

24 Figure 4.5 Chain of events leading to a drifting grounding Probability of machinery failure It is well known among seafarers that most ships sometimes encounter temporary engine failure or electrical blackout leading to the loss of propulsion and steering control. In most cases, the duration of such failures is short and the propulsion can be recovered without creating serious risks. Engine failures and blackout events usually occur in situations when the engine power output is changed, that is during port approaches, departures and manoeuvring. Typical situations are also when vessels are leaving ship yards where reconstruction or overhaul of engine and fuel systems has been undertaken. Various estimations of engine failure rates can be derived from different historic accident statistics and databases. It is, however, not until recent years with the introduction and long term registration of AIS, that reliable figures on the total number of ship hours performed in specific sea areas, with specific ship types etc. have been possible to compile. Still another important contribution to the difficulty of computing reliable probability figures is the fact that many failures are not registered. Many marine risk analysis methods include numerical figures on the expected frequency of engine failure or blackout and normally the figures are expressed in terms of events per ship and hour or per year. Based on experiences from other investigations on drifting grounding assessments performed, a probability of per ship hour for engine failure can be used. Assuming the ship is operating 80% of the time, the figure corresponds to 1.75 breakdowns per ship and year. This figure is also applied in other models for example in the IALA IWRAP model (IALA, 2014). For the present scenarios, the fact that the drifting occurs at sea where large speed alternations are rare, and that many ship types generally show lower probability figures, contribute to make it reasonable to consider this probability figure conservative. 23 (38) SSPA Report No.: RE C

25 Based on the forecasted passages (average of passages over line 4 and 5, see Table 2.1) in the DW route and estimated time for passing the banks at an average speed of 13.5 knots, the number of black-outs in each of the six sections is calculated, see Figure 4.6 and Table 4.5. The total number of blackouts in the six sections are summarized to 13.8/year Figure 4.6 The DW route divided into six sections (1-6). The distance along the western boundary of the DW route is measured to to estimate the number ship-hours in each section Drift direction predominant wind direction The drift direction of a disabled ship is generally governed by the current direction, the wind direction and secondary wave drift forces. In the Baltic Sea. the average currents are very weak implying that drifting is primarily governed by the wind. Wind statistics based on hourly values between 2009 and 2015 at station Hoburg A located at the southern cape of Gotland have been retrieved from SMHI (SMHI, 2016). The statistics show that the prevailing wind direction is southwest which prevails 23% of the time, Figure 4.7. The average wind speed is 5.9 m/s and the maximum wind speed is 23.1 m/s. Wind speeds of 10 m/s or more are registered at 8.6% of the time. 24 (38) SSPA Report No.: RE C

26 Figure 4.7 Wind rose based on wind observations between 2009 and 2015 at Hoburg A (SMHI, 2016). The occurrence of an engine failure or blackout event is assumed to be independent of wind speed and wind direction. The critical wind directions for drifting towards shallow waters are differentiated dependent on location in the DW route. Hence, critical wind directions and frequency have been estimated for each section, see Table 4.3. A blackout in section 4 may potentially imply grounding on either Norra Midsjöbanken or Hoburgs bank. In winds from southwest, which are prevailing 23% of the time, a vessel suffering from blackout will drift towards Hoburgs bank. In winds from southeast, which are prevailing 11% of the time, the same vessel will instead drift towards Norra Midsjöbanken. Based on the frequency of the critical wind direction in each section, the number of vessels with blackout drifting towards the banks is calculated for each section and summed up to a total of 2.47 vessels per year drifting towards shallow waters. Table 4.3 Critical wind directions and their frequencies. Section Number of black out/years Critical wind direction East South east South South west south east South east South Frequency of critical wind direction Vessels drifting towards the banks/year 9% 11% 10% 23% 11% 11% 10% (38) SSPA Report No.: RE C

27 4.2.3 Potential grounders The smallest depth is 10.3 m at Hoburgs bank and 9.3 m at Norra Midsjöbanken (MSL 1945) (Swedish Maritime Administration, 2010). The areas of these depths are limited to minor parts of the banks. Thus, drifting towards the banks does not imply that the vessel will encounter these depths. A major part of the traffic in the DW route is large vessels. However, not all have draught large enough to imply a grounding risk anywhere on the banks. Of the vessels in the DW route, have a draught larger than 8 m, which is defined as the limit for being a potential grounder at a depth of 9.3 m. Five intervals are defined to estimate the number of vessels that may suffer a drifting grounding dependent on depth, see Table 4.2. The critical depth is defined with 15% margin to the upper limit of draught in each interval. This provides a very conservative (high) estimation of the number of potential grounders. Table 4.4 Number of vessels for intervals of draught and corresponding critical depth for each interval. Draught T (m) Number of vessels Critical depths (m) T< (not potential grounders) < T<9 937 potential grounders at depth < T< potential grounders at depth < T< potential grounders at depth < T< potential grounders at depth < In order to estimate the fraction of vessels that are expected to encounter critical depth when drifting in critical wind direction, a sectoral fan is applied. A distribution of possible drift directions is defined for ±22.5 degrees from the main critical drift direction, see Figure 4.8. For each of the indicated sectors A-E the minimum water depth is registered and utilised to derive a probability function for grounding of vessels with respect to their specific draught. 26 (38) SSPA Report No.: RE C

28 Figure 4.8 The "sectoral fan" applied in section 1 to identify the smallest depth in part A. B. C. D and E. In total, 0.6 vessels/year are estimated to be exposed to critical depths when drifting. Hence, one vessel every 1.7 year may be expected to drift aground if no self-repair is successful and no anchoring takes place. In addition to the critical wind direction it can also be assumed that the wind speed has to be high enough to generate a critical drifting speed. Based on a critical wind speed of 10 m/s, the potential grounders can be reduced to 1/11 since the wind speed exceeds 10 m/s only 8.6% of the time Self-repair Many engine failures are repaired by the crew on-board and the power recovered in relatively short time. In most cases the repair is conducted fast and manoeuvring control is recovered in due time to prevent accidental events like collision or groundings. According to Rasmussen (2012) the probability of having repaired the error is given by a cumulative distribution as a function of time. This distribution could be estimated with a Weibull function with k=0.5 and λ=0.605, as illustrated in Figure 4.9, showing that in half of the blackout events, control is recovered within about 15 minutes and only 5% of the failures are not repaired within the first 5 hours from the blackout event. This function of self-repair is applied for rudder failure as well as for blackout events. 27 (38) SSPA Report No.: RE C

29 1-P Rapair 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% t [hour] Figure 4.9 Graph illustrating the probability that a vessel is not repaired as a function of time. The simulations of drifting from the DW route show that the minimum time until grounding is about 6 h, and refers to a container vessel in winds of 23 m/s. Based on the function in Figure 4.9, 96% of all engine failures will be repaired within this time and hence, grounding is avoided. The shortest time until grounding from each section is estimated and the number of potential grounders which will not be repaired in time to avoid grounding is calculated. This leads to a significant reduction of potential grounding events, approximately 1 event in 700 years if no anchoring attempt is made (1.39 x 10-3 grounding/year). Table 4.5 summaries the estimations of potential grounders in the DW route. Table 4.5 Compilation of calculation of potential grounders. Section Total Length of section (km) Number of blackouts/year Vessels drifting towards the banks SW 0.65 SE Potential grounders critical wind speeds 7.83E E E E E E E E-02 - not repaired 2.50E E E E E E E E (38) SSPA Report No.: RE C

30 4.2.5 Failure of emergency anchoring Even though the results of the simulation studies clearly indicates that successful emergency anchoring without significant dragging distances is possible also in worst case wind conditions, it is possible that various technical failures or human error may result in failing of anchoring. High drifting speed is a factor considered to increase the failure risk and at drifting speeds of knots it is assumed that successful emergency anchoring is expected only in 50 % of the events. Taking into account that the fraction of wind speeds generating such drifting speed is very low, an anchoring failure rate is estimated to 5 % at wind speeds above 10 m/s Existing pipeline presence as hindrance for anchoring During the preparation process and routing discussion for the first Nord Stream pipelines, it was claimed that the presence of the pipelines within the outlined buffer zone may constitute a hindrance for emergency anchoring of drifting vessels that had lost its propulsion due to technical failure and potentially drifting towards the protected bank areas. The cognizance of being above or near windward to the pipeline will most likely make the master of the ship unwilling to drop anchor. With today s modern navigation equipment, the position of the ship in relation to the pipeline position as shown in the sea chart or ECDIS, is generally quite precise and clearly legible. Even if the ship has a total blackout, essential navigation equipment as GPS and ECDIS should be operational by electricity supply from emergency generators. This means that as soon as the vessel adrift has passed the pipeline, the master can safely drop anchor without any risk for pipeline interaction. If no power supply is available at the anchor windlass, the anchor cable cannot be walked out mechanically but at adequate anchoring depths the manual windlass brake shall ensure control of the pay out speed of chain. The situation with the vessel drifting without control, the presence of large gas pipelines, shallow banks with stringent protection status in the drifting direction, ongoing urgent repair activities, discussions with rescue resources and perhaps also adverse weather are all together very stressing factors. Factors making it very difficult for the master to make rational considerations and decisions on emergency anchoring, and thus delayed decisions, quick forced anchor handling activities and other human factor related issues are likely to influence the actions taken not to be optimal. Based on these considerations it was found that deployment and the presence of the first Nord Stream pipeline may delay emergency anchoring somewhat in some narrow buffer zone areas, but that such delay of anchoring also would result in anchoring in more favourable water depth. Anchoring simulations in various conditions further demonstrated that there were enough space leeward of the proposed pipeline route for safe anchoring. It was hence concluded that the presence of the first Nord Stream pipeline in the proposed route and its potential delay impact on emergency anchoring of drifting vessels 29 (38) SSPA Report No.: RE C

31 would not increase the overall risk of groundings with oil spills on the shallow bank areas Potential impact of additional NSP2 pipelines along the existing Nord Stream The planned laying of a second Nord Stream pipeline system in parallel with the existing will widen the corridor where emergency anchoring is not feasible, but the presented simulation studies demonstrate that it still will be enough distances of favourable anchoring areas leeward of the pipelines. The routing option for the NSP2 east of the existing pipeline, will not restrict the available areas of the emergency anchoring zones leeward of the existing pipeline. This routing option is therefore considered not to influence the risk of drifting grounding on the banks. The routing option for the NSP2 west of the existing pipeline, will have a small restricting effect on the available areas of the emergency anchoring zones leeward of the existing pipeline. This routing option therefore has a very limited influence on the risk of drifting grounding on the banks. More detailed information on quantitative risk calculations and the event tree model applied are presented in Appendix (38) SSPA Report No.: RE C

32 5 Risk Control Options, RCO Various, existing or possible future, Risk Control Options (RCO) were identified and discussed in the Hazid process and some are subject to further analysis by use of the event tree model. The risk reduction may either address the probability of failure of emergency anchoring by preventive measures, or reduction of the consequences of such events by adequate mitigating measures. 5.1 Comparative aspects of NSP2 route location options Delayed emergency anchoring in case of blackout is identified as the principal hazard that potentially may be influenced by the presence of a second pipeline system and its location relative to the existing pipeline route. The existing Nord Stream pipelines, NSP1, introduced an anchoring hindrance effect and the recently laid Sea Lion cable, in most cases routed m west of the NSP1, possibly widened the anchoring hindrance corridor somewhat even though the hindrance effect imposed by the cable is much weaker than that by the gas pipeline. Both the NSP2 route options, west and east of NSP1, will contribute to a widening of the anchoring hindrance corridor. The western option, however, would affect areas with more favourable anchoring depth leeward of the existing pipeline, whilst the eastern option essentially influences areas with larger depth and less attractive anchoring areas windward of the pipeline and cable corridor where potential dragging of anchors may cause damage to the seabed installations. The area between the existing NSP1 and the planned NSP2 will, because of limited width and adjacent pipelines, not be considered feasible for emergency anchoring. In order to make the widening of anchoring hindrance corridor as limited as possible, the distance between the existing NSP1 and the planned NSP2 pipeline is recommended to be as small as possible. The presented emergency anchoring simulation examples show that the available area, drifting time and distance in the emergency anchoring zones still are large enough, even if the anchoring hindrance corridor would be somewhat widened. Thus such a widening and associated possible delay effect of emergency anchoring would not significantly influence the probability of drifting grounding and it is difficult to quantify any difference in final probability of drifting grounding by use of the event tree model presented in Appendix 4. The recommended routing of NSP2 east of and close to the existing NSP1 can be considered as a preventing risk control option minimising potential delay of emergency anchoring. 31 (38) SSPA Report No.: RE C