KITIMAT LNG IMPORT TERMINAL

Transcription

1 METOCEAN (METEROLOGICAL AND OCEANOGRAPHIC) STUDY Revision 2 ANALYSES OF WIND, WAVE, VESSEL WAKES, CURRENT AND TSUNAMI CONDITIONS FOR BISH COVE Prepared for: Prepared by: 777 W. Broadway, Suite 400 Vancouver, BC Canada V5Z 4J7 Tel: Fax: August 31, 2006 M&N Project No.: M&N Document No.: REP-METO-REV2 Revision Issue Purpose Date Author Reviewed Approved 2 Update for Bish Cove 100% Preliminary Design Submittal August 31, 2006 SL RDB 1 Original Issue - Emsley Cove October 26, 2005 SL RDB

2 TABLE OF CONTENTS KITIMAT LNG INC. EXECUTIVE SUMMARY... ii GLOSSARY... v 1.0 INTRODUCTION SCOPE OF WORK REFERENCE INFORMATION AND DATA MARINE CHARTS TIDES WIND AND WAVE DATA WIND DATA ANALYSIS WIND STATISTICAL ANALYSIS WIND AT PROJECT SITE WAVE DATA ANALYSIS WAVE HINDCAST STUDY WIND-GENERATED WAVE HINDCASTS WAVE AT DOUGLAS CHANNEL: MIKE 21 - NSW MODEL WAVES AT BISH COVE: ACES WINDSPEED ADJUSTMENT AND WAVE GROWTH CODE WAVES AT THE PROJECT SITE VESSEL WAKES PRIMARY WAVE EFFECTS SECONDARY WAVES CURRENTS TSUNAMIS OFFSHORE TSUNAMIS TSUNAMIS GENERATED BY LANDSLIDES CONCLUSIONS AND DISCUSSIONS APPENDICES APPENDIX A - MARINE CHART APPENDIX B - RESULTS OF WIND DATA ANALYSIS APPENDIX C - RESULTS OF WAVE DATA ANALYSIS APPENDIX D - RESULTS OF WAVE MODEL BY MIKE 21 NSW APPENDIX E - RESULTS OF WAVE HINDCAST BY ACES APPENDIX F - RESULTS OF VESSEL-GENERATED WAVES ANALYSIS METOCEAN STUDY REVISION 2 August 31, 2006 Page i

3 EXECUTIVE SUMMARY Kitimat LNG Inc. is proposing to construct a LNG import terminal at Bish Cove, situated approximately 15 km southwest of Kitimat, British Columbia, on a parcel of land adjacent to the tidewater Douglas Channel. This report summarizes the analysis methods and results from the metocean (meterological and oceanographic) studies related to the project including wind, wave, current, vessel wake, and tsunami conditions at the site. The results of these analyses will be used to form the Basis of Design (Design Criteria) for the project. Statistical analyses were performed with measured wind and wave data from the Nanakwa Shoal Marine Buoy, located approximately 3 km down channel from Bish Cove. Numerical models were applied to simulate extreme wind and wind-generated wave conditions at the site for events with 2, 5, 10, 25, 50, and 100 year return periods. The dominant winds in Douglas Channel adjacent to Bish Cove are from the north-east during the winter and from the south-west during the summer. The dominant wind directions follow the orientation of the channel. The cove provides good sheltering from northerly winds but is exposed to the south/south-west. The results of the wind analyses are summarized in Table E1. Table E1: DESIGN WIND SPEEDS Return Period (years) Maximum Sustained Wind at Nanakwa Shoal (m/s) from All Directions from NE from SW from the window 185 o to 195 o METOCEAN STUDY REVISION 2 August 31, 2006 Page ii

4 The wind-generated wave conditions were developed using the coastal engineering and design software programs ACES and MIKE 21. The results of the wind-generated wave analyses are summarized in the Table E2 below. Table E2: DESIGN WAVE (at Bish Cove berth location) Return Period (Years) Wave Height, H (m) H s H 10 H Wave Period, T (s) 4.3 Vessel wakes were predicted by analytical methods using empirical formulae. Based on the results from the analyses and models, the following design parameters are recommended: CURRENTS Table E3: DESIGN VESSEL WAKE (at Bish Cove berth location) Vessel-Generated Wave Case 1 Case 2 Wave Height (m) Wave Period (m/s) Design values for tidal currents and wind-generated surface currents were also estimated based on a literature review and commonly accepted engineering practice. The recommended design value for currents are as follows: Design current: 1.5 knots, parallel to bathymetric contours. It is recommended that a site specific current measurement program be implemented at Bish Cove to verify the magnitude and direction of currents. TSUNAMI Further research is required to better quantify the potential risk of tsunami waves. As an interim measure, the following tsunami heights are suggested for discussion purposes: Design tsunami wave run up height: Generated by offshore seismic event: 2m above mean high water level with negligible current; and, Generated by local subsea landslide: (To be confirmed pending ongoing studies by Jacques Whitford). METOCEAN STUDY REVISION 2 August 31, 2006 Page iii

5 These design parameters will be used to formulate appropriate design criteria for the Kitimat LNG Import Terminal project, including but not limited to the following: Berthing loads; Mooring loads; Slope protection; Navigational guidelines; and, Construction constraints. Detailed descriptions of the methods and assumptions used in the analyses are included in this report. The results of the analyses are summarized in their respective sections, while detailed results are included for reference in the appendices. METOCEAN STUDY REVISION 2 August 31, 2006 Page iv

6 GLOSSARY ACES: The Automated Coastal Engineering System, an integrated collection of coastal engineering design and analysis software. Hindcast: A method of estimating extreme wind, wave, and current conditions at a location based on numerical analysis of historical meteorological data and time histories of the sea state for a given event and return period. MIKE21: An engineering software package developed by the Danish Hydraulic Institute (DHI) consisting of a comprehensive modeling system for the simulation of waves in offshore and coastal areas. Return period, T p : The statistical average interval (in years) between events equal to or greater than the associated extremes. Significant wave height, H s : The average height of the highest one-third of waves in a sample being measured. Other waves of interest are H 1/10 and H 1/100 which represent the average of the highest 10% and 1% of waves respectively. Wavelength, L 0 : The horizontal distance between successive wave crests. Wave height, H 0 : The vertical distance between the crest (highest part) and trough (lowest part) of a wave. Wave period, T: The time interval (in seconds) between successive wave crests. Weibull distribution: A simple analytical distribution function applicable to certain civil engineering problems, including those involving the distribution of wave heights and wave periods. Wake: Waves generated by the motion of a vessel through water. Tsunami: A series of waves, or a wave train, of extremely long wavelength and period. It is generated by a disturbance that vertically displaces the water column from its equilibrium position. Earthquakes, landslides, volcanic eruptions, explosions, and meteorites, can generate a tsunamis. METOCEAN STUDY REVISION 2 August 31, 2006 Page v

7 1.0 INTRODUCTION The proposed Kitimat LNG Import Terminal is to be situated at Bish Cove, approximately 15 km southwest of Kitimat, on a parcel of land adjacent to Douglas Channel. The project includes marine infrastructure for the berthing and unloading of LNG vessels and upland LNG storage, processing and distribution facilities. Wind and wave parameters form part of the basis for coastal and marine structural design. Consequently, wind and wave conditions at the proposed project site need to be characterized before detailed design works are carried out. This report summarizes the results from analyses and numerical models using available wind and wave data in proximity of the project site. Extreme wind speeds for events of 2, 5, 10, 25, 50, and 100 year return periods were calculated with Weibull distributions. Also, a wave hindcast model was developed to determine the wind-generated wave climate for extreme storm events. The height of vessel-generated waves from passing vessels calling at facilities in Kitimat was also considered. These were predicted using empirical equations. Tidal currents, wind-generated surface currents and tsunami waves were also estimated. METOCEAN STUDY REVISION 2 Page 1 August 31, 2006

8 2.0 SCOPE OF WORK The objectives and scope of the study are as follows: Determine the extreme wind speed at various return periods; Determine the extreme wind-generated wave height at various return periods; Estimate the passing vessel wake height and associated effects including return currents and drawdown; and, Estimate the wave height for tsunamis originating from both locally-generated submarine landslides and seismic events. The statistical analysis and coastal engineering modeling undertaken to achieve the above objectives include and report on the following: Extreme wind speed using statistical methods based on recorded wind data; Offshore wave climate using wave hindcasting techniques; Vessel wakes, based on empirical prediction methods; Currents, based on published values for Douglas Channel; and, Tsunami wave heights based on a review of available scientific background studies. METOCEAN STUDY REVISION 2 Page 2 August 31, 2006

9 3.0 REFERENCE INFORMATION AND DATA 3.1 Marine Charts KITIMAT LNG INC. Bathymetric information for the study area is based on information presented on the Canadian Hydrographic Services (CHS) published Marine Chart No for Douglas Channel. A reduced copy of the marine chart is included in Appendix A. Detailed bathymetric information within Bish Cove is based on the results of a bathymetric survey completed by Golder & Associates Ltd. in May A copy of the bathymetry survey results is also included in Appendix A. 3.2 Tides Characteristic tide levels above chart datum at Bish Cove are assumed to be consistent with those at Kitimat. Design tidal elevations, based on information published in the CHS Tide Tables, Volume 7, are as follows (all elevations are referenced to Tide and Chart Datum (CD) which is 3.23 m lower than Geotetic Datum): 3.3 Wind and Wave Data Table 3.1: Tide Levels at Kitimat Large Tides: H.H.W. 6.5 m L.L.W m Mean Tides: H.H.W. 5.3 m L.L.W. 1.0 m Mean Water Level: M.W.L. 3.3 m The Marine Environmental Data Service (MEDS) of the Department of Fisheries and Oceans (DFO) maintains a wave rider buoy at Nanakwa Shoal, located within Douglas Channel approximately 11 km south-west of Bish Cove (see station identification data in table 3.2 on the following page). The buoy provides approximately 17 years of wind and wave measurements. A number of other wind stations in the region (eg. Kitimat, Prince Rupert) were also obtained and reviewed. Due to the proximity to the site, the Nanakwa Shoal data are considered most representative of conditions with Bish Cove, and form the basis for most of the wind and wave hindcasting carried out for the site. An additional station operated at Bish Cove for a one-year period in 1997 as part of a previous site investigation program. Although the one-year period record is too short to be used for statistical hindcasting purposes, the data were nonetheless compared to the corresponding period at Nanakwa Shoal to validate the localized conditions. In general, the Bish Cove data show similar trends in wind speed and direction, but the magnitude of the wind speed is somewhat reduced. The use of Nanakwa Shoal data is therefore considered to be conservative for this project. Details of the analysis procedure are described in section 4.0. METOCEAN STUDY REVISION 2 Page 3 August 31, 2006

10 Table 3.2: Summary of Wind and Wave Data Information Station Name: Nanakwa Shoal Station ID: Location: 49 o 50'N, 128 o 49'W Observed Elevation for Wind Speed Measurements (m): 5 Observed Depth for Wave Height Measurements (m): 21 Distance to Kitimat LNG Carrier Berth (km): 11 Data Period: Total Hours: 103,222 METOCEAN STUDY REVISION 2 Page 4 August 31, 2006

11 4.0 WIND DATA ANALYSIS 4.1 Wind Statistical Analysis BISH COVE A total of 8,760 hours of valid wind data from the one-year ( ) Bish Cove record were analyzed. Table 4.1 and Fig.4.1 summarize the wind climate in wind rose and bi-variate histogram formats, respectively. Table 4.1: Wind Frequency Distribution (Count) Bish Cove Wind Speed N NE E SE S SW W NW Total (m/s) > Total Frequency of Calm Winds: 122; Average Wind Speed: 3.15 m/s NORTH 25% 20% 15% 10% WEST 5% EAST SOUTH WIND SPEED (m/s) >= Calms: 1.39% Fig. 4.1: Bish Cove Wind Rose METOCEAN STUDY REVISION 2 Page 5 August 31, 2006

12 NANAKWA SHOAL A total of 85,266 hours of valid wind data from 1988 to 2005 were used in the statistical analysis. Yearly maximum wind speeds were sorted and converted to 10 m elevation wind speeds using the following equation: U 10 = U z 10 z 1 7 Where z is the wind observation height (5m in the case of the Nanakwa Shoal Marine Buoy). Table 4.2 and Fig. 4.2 Summarize the wind climate in wind rose and bi-variate histogram formats, respectively. Table 4.2: Wind Frequency Distribution (Count) Nanakwa Shoal Wind Speed (m/s) N NE E SE S SW W NW Total > Total Frequency of Calm Winds: 4508; Average Wind Speed: 4.68 m/s METOCEAN STUDY REVISION 2 Page 6 August 31, 2006

13 NORTH 20% 16% 12% 8% 4% WEST EAST WIND SPEED (m/s) SOUTH >= Calms: 4.83% Figure 4.2: Nanakwa Shoal Wind Rose Detailed wind data for Nanakwa Shoal are presented in Appendix B. Comparing Figures 4.1 and 4.2, it is clear that the prevailing wind directions at Bish Cove and Nanakwa Shoal are quite similar. The wind frequency distributions for the both stations with same period are listed in Table 4.3. The dominant wind directions in the area vary with seasons, from the north-east during winter (October to March) and from the south-west during the summer (April to September). The maximum hourly wind speed recorded during the period of record was 20.3 m/s, observed in January 2000 at Nanakwa Shoal. Table 4.3: Comparison of Wind Frequency versus Wind Direction Station Frequency Distribution (%) N NE E SE S SW W NW Calm Total Bish Cove Nanakwa Shoal METOCEAN STUDY REVISION 2 Page 7 August 31, 2006

14 The averaged monthly maximum wind speed at Bish Cove is about 33% smaller than at Nanakwa Shoal. A comparison of maximum monthly wind speeds of the two stations for the same period is summarized in Table 4.4. Table 4.4: Comparison of Monthly Maximum Hourly Wind Speeds (m/s) Year Month SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Bish Cove Nanakwa Shoal Due to the limited duration of the Bish Cove data, is not considered suitable for design purposes. It is recommended that the wind data at Nanakwa Shoal be used for the design of the project. 4.2 Wind at Project Site To determine the wind climate at the project site, the ACES Extremal Analysis Code was applied to the Nanakwa Shoal data to determine the extreme wind speeds (assuming Weibull distributions) for return periods of 2, 5, 10, 25, 50, and 100 years. Table 4.5 presents a summary of the results of the analysis. Detailed results of the analysis are included in Appendix B. Return Period (years) Table 4.5: Design Wind Speeds for Kitimat LNG Import Terminal from All Directions* Maximum Sustained Wind (m/s) from NE from SW from the window 185 o to 195 o * Adjustments are made for some return periods to ensure the wind speed from all directions be never less than from a specific direction. METOCEAN STUDY REVISION 2 Page 8 August 31, 2006

15 5.0 WAVE DATA ANALYSIS The data record for the Nanakwa Shoal Marine Buoy includes wave data in addition to the wind data discussed in Section 4. However, a review of the raw data indicates that the integrity of some of the wave data from the Nanakwa Shoal is questionable. Near the end of October 1997, the measured wave periods were often unusually long with periods of 32 seconds being very common. This long wave period is not consistent with local windgenerated waves. After this date, wave periods were almost exclusively less than 10 seconds. It seems that either the wave sensor or the processing changed around the end of October 1997, and again around July 1999 (after which date the wave periods were reported with a precision of 0.1 seconds rather than 1 second as previously reported). On occasion, measured wave heights are extremely high. For example, on January 11, 1998, the measured wave height was 6.7 meters. No wave period was measured for these waves, suggesting problems with either the wave gauge or the processing. Wind-generated wave periods in excess of 5 seconds are thought to be erroneous since such low frequency waves cannot be generated within a relatively small fetch such as the Douglas Channel, nor can they effectively propagate into the channel from the deep ocean. Removing apparent outliers in the wave height sequence suggests that the maximum wave height, for locally-generated waves, is approximately 1.5 meters. For waves from the south to southwest, the maximum wave height appears to be approximately 1.1 meters. The wind-generated waves in Douglas Channel are short waves, with a period less than 5 seconds, and would approach the site from within a very narrow window to the south. Higher waves are possible in the channel, particularly from the northeast. However, Bish Cove is well protected from the northeast. An ACES analysis was performed on the wave data, filtered with the removal of waves with a period of 5 seconds and greater. Table 5.1 summarizes the results of the ACES analysis and presents the significant wave heights (assuming Weibull distributions) at Nanakwa Shoal for return periods of 2, 5, 10, 25, 50, and 100 years. The detailed results of the wave height analysis are included in Appendix C. Return Period (Years) Table 5.1: Significant Wave Height at Nanakwa Shoal Significant Wave Height, Hs (m) From All Directions From NE-Direction From SW-Direction METOCEAN STUDY REVISION 2 Page 9 August 31, 2006

16 6.0 WAVE HINDCAST STUDY 6.1 Wind-Generated Wave Hindcasts As there is no long-term wave record available for Bish Cove, wave conditions were hindcasted from wind data. The offshore wave climates at Douglas Channel were modeled utilizing MIKE21. MIKE 21 is an engineering software package developed by the Danish Hydraulic Institute (DHI) and is a comprehensive modeling system for the simulation of waves in offshore and coastal areas. The Nearshore Spectral Wind-Wave module (MIKE21-NSW) is a time-dependent, fully discrete spectral wave model which describes the formation, growth, and decay of waves in time and space as a function of a varying wind field. The model comprises the effects of refraction and shoaling due to varying depth and wave generation due to wind. Wave conditions at Bish Cove, a function of wind climate and wind fetch, were hindcasted using ACES. The Automatic Coastal Engineering System (ACES) computer program is an integrated collection of coastal engineering and design software, developed by U.S. Army Cops of Engineers, covering: wave prediction, wave theory, wave transformation, structural design, wave runup, transmission, and overtopping, littoral processes, inlet processes, and harbour design. The ACES Code of Windspeed Adjustment and Wave Growth was applied for wave hindcast. 6.2 Wave at Douglas Channel: MIKE 21 - NSW Model The objective of this task was to predict the wind-generated waves at Douglas Channel, and validate the results of the wave data analysis discussed in Section 5.0. An offshore spectral wind-wave numerical model was developed using the MIKE 21-NSW model. The model grid with spacing of 50 meters was developed based on the marine charts listed in Section 3.1. The MIKE 21-NSW model grid is shown in Fig METOCEAN STUDY REVISION 2 Page 10 August 31, 2006

17 Bathymetry N 25 BISH COVE (Units in kilometer) NANAKWA SHOAL (Units in kilometer) Bathymetry Above Below -300 Undefined Value Figure 6.1: MIKE 21 NSW Model Grid and Bathymetry METOCEAN STUDY REVISION 2 Page 11 August 31, 2006

18 The governing wind-generated waves will occur outside of Bish Cove during the predominantly north-east and south-west wind events described in Section 4.0. These conditions, summarized in Table 6.1 below, were used as input for the MIKE21-NSW model. The duration of the winds were assumed longer enough to achieve fetch-limit conditions. Return Period (Years) Table 6.1: MIKE 21 - NSW Model Input Conditions Direction ( o N) SW-Winds Speed (m/s) Direction ( o N) NE-Winds Speed (m/s) Table 6.2 and shown in Fig. 6.2 below present a comparison between the results of the ACES Code of Extremal Analysis of the Nanakwa Shoal Marine Buoy data and the MIKE21- NSW model. The comparison indicates that there is generally good agreement between the two methods, with a difference of within 10% for a 100 year return period event. Table 6.2: Significant Wave Heights by ACES Code of Extremal Analysis and MIKE 21 - NSW Model (Nanakwa Shoal) Return Period (Years) Significant Wave Height, Hs (m) ACES Extremal Analysis MIKE 21-NSW Model METOCEAN STUDY REVISION 2 Page 12 August 31, 2006

19 2 1.5 Hs (m) ACES Extremal Analysis MIKE 21 - NSW Model Return Period (Year) Figure 6.2: Significant Wave Heights by ACES Extremal Analysis and MIKE 21-NSW Detailed modeling results, including graphical results of all MIKE 21-NSW model simulations, are included in Appendix D. An example of the significant wave height distribution results for a 100 year wind event from the south-west is illustrated in Fig. 6.3 below. Hm0 [m] N (Units in kilometer) (Units in kilometer) Figure 6.3: MIKE 21-NSW Wave Height Results (100 year south-west Wind) Hm0 (m) Above Below 0 Undefined Valu 6.3 Waves at Bish Cove: ACES Windspeed Adjustment and Wave Growth Code A two-dimensional Boussinesq wave model (MIKE 21-BW), which covers the Bish Cove and approach entrance, was initially developed for the wave propagation study. These model results proved to be unreliable and were not used in this report. Instead, the ACES Code of Windspeed Adjustment and Wave Growth was used to hindcast the wave conditions at Bish Cove. METOCEAN STUDY REVISION 2 Page 13 August 31, 2006

20 The wind-generated wave conditions are determined by the wind direction, wind speed, duration of the wind and the dimension of the fetch. The predominant winds occur outside of Bish Cove are in north-east and south-west directions. Only south-west wind events were applied for wave hindcasting as the Bish Cove is well protected from north-east direction. Different wind directions and durations with associated return period were applied to establish the critical wave conditions. The maximum air-sea temperature difference of -7 o C in the area was used for stability correction of wind speeds. Combinations of case for applying ACES Code of Windspeed Adjustment and Wave Growth are listed in Table 6.3 below. Table 6.3: Case of Combination for ACES Wave Hindcasting Wind Direction ( o N) Fetch (km) Wind Duration (Hrs) Return Period (Years) Wind Speed (m/s) , 1.5, 2.0, 2.5, 3.0 2, 5, 10, 25, 50, , 13.4, 14.6, 15.8, 16.6, , 16.4, 17.9, 19.5, 20.6, 21.6 It is found that winds blowing from 190 o N to 225 o N with wind duration of 2 to 2.5 hours result the maximum waves for all the return periods. The predicted maximum waves with associated return period are summarized in Table 6.4 below. Detailed results of the ACES wave hindcasting are included in Appendix E. Table 6.4: Results of ACES Wave Hindcast Return Period (Years) Wind Direction ( o N) Wind Speed (m/s) Wind Duration (Hrs) Fetch (km) Wave Heights (m) Wave Period (s) METOCEAN STUDY REVISION 2 Page 14 August 31, 2006

21 Recorded data of south-west wave at Nanakwa Shoal were analyzed using ACES Code of Extremal Analysis, and the extremal winds were applied to ACES Code of Windspeed Adjustment and Wave Growth. Table 6.5 and shown in Fig. 6.4 below present a comparison between the results obtained from the two different methods. The comparison indicates that there is generally good agreement between the two methods, with the hincasted values slightly high. Table 6.5: Results of Significant Wave Height (Nanakwa Shoal) Return Period (Years) ACES Extremal Analysis Significant Wave Height, Hs (m) ACES Wave Hindcast Hs (m) ACES Extremal Analysis ACES Wave Hindcast Return Period (Year) Figure 6.4: Significant Wave Heights by ACES Extremal Analysis and Wave Hindcast METOCEAN STUDY REVISION 2 Page 15 August 31, 2006

22 6.4 Waves at the Project Site Based on the analysis described above, the recommended design waves for the Bish Cove project site are summarized in Table 6.6 below. Table 6.6: Design Waves for Kitimat LNG Import Terminal Return Period (Years) Wave Height, H (m) H s H 1/10 H 1/100 Wave Period, T (s) Notes: H 1/10 = 1.27H S (Upper 10 th percentile wave height); and H 1/100 = 1.67H S (Upper 1 st percentile wave height) METOCEAN STUDY REVISION 2 Page 16 August 31, 2006

23 7.0 VESSEL WAKES The following description of vessel wakes is adapted from a number of sources, including Sorensen (1997), Schiereck (2001) and PIANC (1987). A vessel moving through the water creates a characteristic pattern of waves, some of which travel with the ship and some of which radiate outward from the vessel s sailing track. Vessel wake effects can be broadly categorized into two groups primary and secondary waves. Primary waves move with the vessel and are caused by the hydrodynamic pressure field created by the moving hull. As a vessel moves through the water, there is flow back past the vessel hull relative to the hull, known as the return current. The velocity head of this current will cause the water level around the vessel to be lowered. This water level depression or drawdown is most pronounced close to the moving hull, and diminishes as the distance from the hull increases (See Figure 7.1). Figure 7.1: Illustration of Primary wave (adapted from PIANC 1987) METOCEAN STUDY REVISION 2 Page 17 August 31, 2006

24 Drawdown behaves like a long solitary wave with a wavelength similar to the overall length of the ship. Drawdown does not break at the shoreline as normal waves do. It is more like a tidal pulse, slowly rising and falling as the vessel passes. As a result, drawdown is generally not easily observed in the field. It also tends not to be of significant concern from a shoreline erosion point of view. Nonetheless, in narrow or shallow channels, where a moving vessel passes close to another ship at berth, the drawdown wave field can cause suction forces which adversely affect a moored ship. These passing ship effects have been known to shift the moored ship along the berth, hampering cargo transfer operations or even breaking mooring lines. A pattern of diverging secondary waves are created as a direct result of the primary wave drawdown. The sharp rise and fall in the water surface at the bow and the stern produces a pattern of free surface waves that propagate from the vessel (Figure 7.2). The pattern consists of symmetrical sets of diverging waves that move obliquely out from the sailing line and a single set of transverse waves that move in the direction of the sailing line. The transverse and diverging waves meet to form cusps, also called interference peaks, located along a pair of lines that form an angle of about 19.5 degrees with the sailing line. The highest waves in the pattern are found along this cusp locus line. The wave pattern spreads out from the vessel, and the wave heights gradually decay as they propagate away from the ship. These secondary waves are the ones that are generally visible in the field. Secondary waves are always short and behave like normal waves, which means that the general linear wave theory relations for wavelength, celerity etc. are valid. They also break as they approach the bank shoreline and breaking type (i.e., spilling, plunging, or surging) is dictated by the same slope and wavelength relationship as other normal waves. Figure 7.2: Secondary Wave Pattern (adapted from Schiereck, 2001) The magnitude of the generated waves depends on a complex combination of variables including the vessel size, operating draft, hull form, speed, water depth, channel geometry, and other factors. METOCEAN STUDY REVISION 2 Page 18 August 31, 2006

25 7.1 Primary Wave Effects Within Bish Cove, LNG vessels would be moving very slowly, such that wake generation would be negligible. Tug boats operating within Bish Cove, and vessels of all sizes passing by the site en route to and from Kitimat, may create wakes. Due to the sheltering provided by headland at Bish Cove and the distance from the sailing track of vessels in Kitimat Arm, it is expected that the primary wave effects from passing vessels will be negligible within Bish Cove. Although the primary wave effects are not expected to impact directly on the berth location in Bish Cove, the effects may be of relevance outside the cove, for example in the approaches along Douglas Channel. While the focus of this wind and wave study is to determine the design conditions for the berth area only, the vessel wake effects were evaluated for completeness since this information may be required as part of other studies covering the entire area. A 200,000 m 3 capacity LNG carrier with beam of 48.5 m and loaded draft of 12.5 m, in accordance with the project Design Criteria, was used as the basis for the drawdown and return current analysis. The maximum vessel speed is 12 knots (6.17 m/s) and the minimum channel depth is 15 m. The drawdown and the return current are estimated by using the ACES Code of Vessel Generated Waves. A number of runs were analyzed to determine a range of values, and to establish the governing design case. Table 7.1 presents a summary of the input variables and the output results for the ACES analysis. Table 7.1: Results of Drawdown and Return Current by ACES Parameter Value Vessel Speed, Vs (knots) 12.0 Vessel Wetted Cross-Sectional Area, A m (m 2 ) 606 Channel Depth, d (m) 19.3* Channel Width, b (m) 350 Drawdown, Δd (m) 0.56 Return flow, V r (m/s) 0.83 * An iterative process is required to determine a value that ensures the ACES program formulae converge. The depth indicated is much less that the actual channel depth, but this is a conservative result. The drawdown and return flow values, indicated above, are considered to conservatively representative conditions outside of Bish Cove. Within Bish Cove, the drawdown and return current values are expected to be negligible. METOCEAN STUDY REVISION 2 Page 19 August 31, 2006

26 7.2 Secondary Waves Secondary wave effects within Bish Cove may be generated from passing vessels en route to Kitimat, as well as tug operations near the berth. The characteristics of vessel wakes is dependent a several variables, including vessel type and speed. Numerous authors have developed analytical relationships to predict wake heights, results of which vary widely. Sorensen (1997) provides a technical discussion related to the development and use of these prediction methods. Based on Sorensen s discussion, the following models were considered to be most appropriate for the Kitimat LNG project: PIANC s method (1987); Weggel and Sorensen method (1986), and; Gates and Herbich method (1977). These three methods were each used to estimate the wake conditions for Bish Cove, with the most conservative result adopted for design purposes. The predicted vessel wake heights are summarized in Table 7.2, below. Table 7.2: Results of Vessel-generated Waves Patrol Boats, Tugboats Vessel Type Oil Tankers Ore Carriers and Motorboats Vessel Speed (knots) H s (m) T (s) Based on this analysis, vessel wakes from tug and patrol boats govern. For design purposes within the Bish Cove, two conditions will be considered as follows: Case 1: H s = 0.96m, T = 3.2 s Case 2: H s = 0.74m, T = 5.9 s References: Gates, E. T., and Herbich, J. B. (1977). A mathematical model to predict the behavior of deep-draft vessels in restricted waterways,@ Report TAMU-SG , Texas A&M University, College Station, TX. Permanent International Association of Navigation Congress (PIANC), Supplement to Bulletin No Guidelines for the Design and Construction of Flexible Revetments Incorporating Geotextiles for Inland Waterways, Report of Working Group 4 of the Permanent Technical Committee I. Sorensen, R.M. (1997). Prediction of Vessel-Generated Waves with Reference to Vessels Common to the Upper Mississippi River System. Prepared for US Army Corps of Engineers. METOCEAN STUDY REVISION 2 Page 20 August 31, 2006

27 Sorensen, R.M., and J.R. Weggel, Development of Ship Wave Design Information, Chapter 216, Proceedings, 27th International Conference on Coastal Engineering Schiereck, G.J. (2001). Introduction to Bed, Bank and Shore Protection. Delft University Press Weggel, J. R., and Sorensen, R. M. (1986). A ship wave prediction for port and channel design. Proceedings of the Ports '86 Conference, Oakland, CA, May 1986, American Society of Civil Engineers, New York, METOCEAN STUDY REVISION 2 Page 21 August 31, 2006

28 8.0 CURRENTS Douglas Channel is a tidal watercourse and is therefore affected by tidal currents due to rising (flood) and falling (ebb) tides. There are no measured tidal current data available near the project site. The published tidal current velocities indicated on the CHS Marine Chart No for Douglas Channel are 0.5 knots for flood conditions and 1 knot for ebb conditions. This range of values was confirmed in discussions with The BC Coast Pilots Ltd. related to the Kitimat LNG project. In addition to tidal currents, energy is transferred when wind blows over the ocean from the wind to the surface layer. In the open ocean, the current speed will be about 2% to 3% of the wind speed. For the 100 year return wind with speed of 25.6 m/s, a wind-generated surface current of 0.8 m/s, or 1.5 knots, is estimated. Within Bish Cove, the tidal and wind-generated currents would expect to be significantly less than in the open channel. It is recommended that a current measurement program be initiated with Bish Cove to provide site-specific current data for both design and operational purposes. In lieu of site specific data, a conservative current velocity of 1.5 knots is recommended. METOCEAN STUDY REVISION 2 Page 22 August 31, 2006

29 9.0 TSUNAMIS Tsunamis can be generated by earthquakes, landslides, volcanic eruptions, explosions, and meteorites. Tsunamis generated by earthquakes can travel great distances and can affect coastlines distant from the source. Other types of tsunamis, e.g. those generated by landslides, are more localized in nature. The project site is potentially susceptible to tsunamis generated from both offshore Pacific Basin seismic events and locally-generated submarine landslide events. The risks of tsunamis generated from other effects are considered to be negligible. 9.1 Offshore Tsunamis According to a 2004 report published by the District of Kitimat, estimates of 3.1 m for the 100 year return period and 6.0 m for the 200-year period have been made in terms of trough-to-crest height of a tsunami at Kitimat (Wigen 1979). However, the Kitimat report also states that following a tsunami warning on the BC coast in 1994, subsequent studies revealed that the wave heights approximately 1 foot (very negligible) over normal tide/current tables was the maximum impact on the port at Kitimat. This apparent contradiction is not explained in the report. The District of Kitimat report does not explicitly identify the Wigen 1979 citation, of which several were published by that author in Moffatt & Nichol obtained a number of Wigen publications from that year. The most relevant appears to Wigen s Tsunami frequency at Tofino and Port Alberni, which involved a statistical analysis of 33 measured tsunami events between 1906 and The Wigen papers relate strictly to events at Port Alberni and Tofino, both of which are located more than 500 km from Kitimat on the west coast of Vancouver Island. No direct references to the Kitimat area are made in this study or any of the other Wigen references from The geographical and hydrodynamic characteristics between the channels leading to Port Alberni and Kitimat are quite different. Within the estuary leading to Port Alberni, it is more likely that a tidal bore could be generated because of the funnel shape of the watercourse and generally shallower depths. Douglas Channel, on the other hand, contains a number of turns and curves, maintains very deep water, and is generally quite wide. The project site is located about 95 nautical miles (176 km) from the open ocean entrance at Hecate Strait through the Caamano Sound, Squally Channel, Lewis Passage, Wright Sound and Douglas Channel. The channel width varies from 2 to 5 kilometers and water depth from 100 to 500 meters. Furthermore, the severe wave height and run up experienced at Port Alberni following the 1964 Alaska earthquake is attributed in part to the chance correlation between the natural resonant frequency of the inlet and the frequency of the approaching wave. This allowed the wave to be amplified, much as the water in a bathtub can be made to slosh higher and higher with properly timed rhythmic movements of one s hand. (Thomson, 1981). Since the natural frequency of Douglas Channel would be expected to very different from Alberni Inlet, there is little theoretical basis on which to correlate tsunami heights at Kitimat and Port Alberni. In our opinion, the 3.1 and 6.0 m wave heights quoted in the District of Kitimat report do not represent a reliable statistical assessment of tsunami risk for Kitimat. METOCEAN STUDY REVISION 2 Page 23 August 31, 2006

30 A more relevant study of tsunami risk along the British Columbia coast was published in 1988 by Seaconsult Marine Research Ltd. The Seaconsult study was based on detailed computer modeling of tsunamis approaching the west coast and propagating up the various inlets, including Douglas Channel and Kitimat. The study estimated the effects from tsunamis generated from hypothetical earthquakes originating in several known tsunamigenerating areas in the Pacific basin, including the Prince William Sound area in Alaska (source of the devastating 1964 Alaska earthquake and tsunami), the Aleutian Islands (Shumagin Gap), Kamchatka Peninsula, and Chile. The model results were validated against tide data and actual tsunami records from the 1964 Alaska event and were generally found to be in good agreement. In each case, the model results show that the water level variations and current velocities at Kitimat were substantially less than those predicted for Port Alberni, mainly due to differences in the inlet bathymetry and exposure to the outer coast. A comparison of the predicted wave and current heights at Port Alberni and Kitimat is shown below. Table 9.1: Comparison of Predicted Tsunami Results: Kitimat vs. Port Alberni Event Description Wave Height (m) Current (m/s) Kitimat Port Alberni Kitimat Port Alberni Alaska Chile Shumagin Gap Kamchatka In general, the predicted tsunami heights at Kitimat are on the order of 11% to 22% of the heights at Port Alberni, with a mean of approximately 18%. The largest predicted tsunami height at Kitimat is 1.9m, compared to corresponding wave of 8.3 m at Port Alberni. The current velocities at Kitimat are also very low, suggesting that these tsunamis would appear much like a rapidly rising and falling tide rather than a destructive bore or breaking wave. Given that the deck elevations of the anticipated marine structures for Bish Cove are more than two metres above the highest tide level, it does not appear that offshore tsunamis represent a serious threat to the facility. For design purposes, it is recommended that a tsunami height of 2.0 m be used which could occur at any stage of the tide. The current associated with this event would be negligible. The estimated return period of such an event occurring at or below mean tide would be greater than 200 years, based on the statistical results quoted earlier for Port Alberni. 9.2 Tsunamis Generated by Landslides An undersea landslide triggered a tsunami in the Kitimat Inlet of northern British Columbia s Douglas Channel in The event originated at Moon Bay on April 27, 1975, just south of the Alcan facility, on the north shore of Douglas Channel. Based on personal accounts from residents, documented in Golder s 1975 report to the BC Water Resources Service reviewing the incident, a wave height of about 6 meters was observed directly across Douglas Channel at Kitimat Village, about 10 kilometers upstream the project site. METOCEAN STUDY REVISION 2 Page 24 August 31, 2006

31 According to the findings presented in the Golder report, the cause of the landslide was shearing failure of the soft marine clay triggered by excess pore water pressures due to an extreme low tide and saturated conditions due to spring run-off. Since the 1975 Kitimat landslide was relatively well documented, it has been the focus of a number of research papers intended to develop predictive modeling tools for similar events. Skvortsov prepared a numerical animation of the landslide mass and the resultant wave. The images in Figure 9.1 below illustrate the initial generation and propagation of the wave beginning at 10 seconds after the start of the event, followed by images at 40s, 60s, and 70s respectively. The animation shows how the wave energy radiates outward from the source in an arc, decreasing in height as the length of arc increases. In the last image (at t=70 seconds) the crest height increases significantly due to run up on the opposite shore. This simulation shows how the wave run-up height on shore can exceed the height of the wave in deeper water. It also illustrates how the areas at greatest risk are in the immediate vicinity of the slide, as well as any areas on shore immediately opposite the slide location. T = 10 sec T = 40 sec T = 60 sec T = 70 sec Run-up Figure 9.1: Numerical Animation of Tsunami from 1975 Kitimat Landslide (adapted from Skvortsov) METOCEAN STUDY REVISION 2 Page 25 August 31, 2006

32 According to the Port of Kitimat Capability Report, four potential sites located within Kitimat harbour were identified to have metastable subsurface sediments which could be susceptible to sliding. These sites are at least 10 kilometers north of the project site. Hence the landslide generated waves at Bish Cove from these potential sites are expected smaller than at Kitimat since the cove is protected from the north. An alluvial delta within the western half of Bish Cove is a potential location for a landslide and subsequent tsunami. A geotechnical investigation of the site will be carried out during the current project to assess its stability under static and seismic conditions. Based on the results of the geotechnical investigation, further work will be carried out to develop an estimate of potential landslide generated tsunami waves at the project site (To Follow). References: District of Kitimat. (2004). Port of Kitimat Capability Report: A Guide for Industrial Investors and Senior Governments Regarding Kitimat s Capacity for Additional Industrial and Port Development. Golder & Associates Ltd. (1975, June). Report to BC Water Resources Service on Investigation of Seawave at Kitimat, BC Thomson, R.E. (1981). Oceanography of the British Columbia Coast, Can. Spec. Publ. Fish. Aquat. Sci. 56: 291 p. Seaconsult Marine Research, Ltd. (1988). (Dunbar, D.S., LeBlond, P.H., and Hodgins, D.O., authors) Evaluation of tsunami levels along the British Columbia Coast. Report prepared for the Department of Fisheries and Oceans, Institute of Ocean Sciences, Sidney, BC, March Skvortsov, Andrey. Numerical modeling of landslide - generated tsunamis. MSc Research, University of Victoria Research abstract published online at Wigen, Sydney O., Tsunami frequency at Tofino and Port Alberni, Institute of Ocean Sciences METOCEAN STUDY REVISION 2 Page 26 August 31, 2006

33 10.0 CONCLUSIONS AND DISCUSSIONS Wind and wave data at Nanakwa Shoal were collected for the study. The wind and wave characteristics at Nanakwa Shoal are suitable to represent the metocean conditions for the project as the shoal is located near the site in open water. Wind data were analyzed statistically. The dominant winds are aligned with the channel north-east and south-west directions. The annual maximum wind speeds are usually from the north-east direction and are associated with winter out flow events. The project site is largely sheltered from these north-east winds, with the greatest exposure coming from south-west winds. The averaged annual maximum wind speed from the window of 185 o to 195 o is about 70 % of that from all directions (or from north-east direction). The maximum wave height at Nanakwa Shoal during 18 years of records, after removing apparent erroneous data, is 1.47 meters. Extreme wind events were applied to wave hindcast by using ACES code. The winds from north-east direction generate the highest waves in Douglas Channel. However, south-west wind climate governs since the area is well protected from north-east direction. The vessel wakes were analyzed by applying ACES code and other empirical methods. The drawdown and return currents were predicted by ACES code, and the secondary waves were estimated by three different methods. The recommend design criteria for the project are as follows: Design winds: Table 4.5 Design waves: Table 6.6 Design vessel-generated wakes: Case 1: H s = 0.96m, T = 3.2 s Case 2: H s = 0.74m, T = 5.9 s Maximum currents: 1 knot, parallel to bottom contours, 1 year return period. 2 knots, parallel to bottom contours (100 year return period). The tsunami waves from distant earthquakes and locally generated landslides were also reviewed. Tsunamis from locally-generated landslides are considered to represent a higher risk than those generated from distant seismic events. Further geotechnical field investigation within Bish Cove and the immediate vicinity in Douglas Channel is needed to help quantify the risk of a locally-generated landslide. METOCEAN STUDY REVISION 2 Page 27 August 31, 2006

34 APPENDIX A MARINE CHART

35 Bish Cove METOCEAN STUDY Page 1 APPENDIX A August 31, 2006

36 METOCEAN STUDY Page 2 APPENDIX A August 31, 2006 KITIMAT LNG INC.

37 APPENDIX B RESULTS OF WIND DATA ANALYSIS (NANAKWA SHOAL)

38 WIND ROSE PLOT: MEDS ID: C46181 Station Name: Nanakwa Shoal DISPLAY: Wind Speed Direction (blowing from) NORTH 20% 16% 12% 8% WEST 4% EAST SOUTH WIND SPEED (m/s) >= Calms: 5.29% COMMENTS: ALL DATA DATA PERIOD: Jan 1 - Dec 31 00:00-23:00 CALM WINDS: 5.29% MOFFATT & NICHOL MODELER: Shawn Lu TOTAL COUNT: hrs. AVG. WIND SPEED: 4.68 m/s DATE: 8/5/2005 PROJECT NO.: 5499 WRPLOT View - Lakes Environmental Software METOCEAN STUDY Page 1 APPENDIX B August 31, 2006

39 WIND ROSE PLOT: MEDS ID: C46181 Station Name: Nanakwa Shoal DISPLAY: Wind Speed Direction (blowing from) NORTH 25% 20% 15% 10% WEST 5% EAST SOUTH WIND SPEED (m/s) >= Calms: 5.08% COMMENTS: Data for: Apr to Sep. DATA PERIOD: Apr 1 - Sep 30 00:00-23:00 CALM WINDS: 5.08% MOFFATT & NICHOL MODELER: Shawn Lu TOTAL COUNT: hrs. AVG. WIND SPEED: 4.13 m/s DATE: 8/5/2005 PROJECT NO.: 5499 WRPLOT View - Lakes Environmental Software METOCEAN STUDY Page 2 APPENDIX B August 31, 2006