Environmental Statement Chapter 12 Appendix A - GEMS Geophysical Survey Report

Transcription

1 DOGGER BANK CREYKE BECK April 2013 Environmental Statement Chapter 12 Appendix A - GEMS Geophysical Survey Report F-OFC-CH-012 Appendix A Issue 1 Chapter 12 Page i 2013 Forewind

2 DOGGER BANK CREYKE BECK Title: Dogger Bank Creyke Beck Environmental Statement Chapter 12 Appendix A - GEMS Geophysical Survey Report Contract No. (if applicable) Forewind Document Number: F-ONC-CH-012 Appendix A Issue No: 1 Issue Date: 19-Oct-12 Status: Issued for 1st. Technical Review Issued for PEI3 Issued for 2nd. Technical Review Issued for Application Submission Prepared by: GEMS Survey Ltd. Approved by: GEMS Survey Ltd. Checked by: (Forewind) Sophie Barrel Signature / Approval (Forewind) Approval Date: 1-Dec-12 Gareth Lewis Revision History Date Issue No. Remarks / Reason for Issue Author Checked Approved 19-Oct-12 1 Issued for Approval GEMS F-OFC-CH-012 Appendix A Issue 1 Chapter 12 Page ii 2013 Forewind

3 GEMS International Group of Companies Geotechnical, Geophysical and Metocean Expertise around the World GEOPHYSICS RESULTS REPORT VOLUME 4 OF 9 DOGGER BANK TRANCHE A ACOUSTIC AND GEOPHYSICAL SURVEY PREPARED FOR FOREWIND LIMITED DOCUMENT REF.: REVISION: OCTOBER GEMS Survey Limited St. James House, St. James Place, Gains Lane Devizes, Wiltshire, SN10 1FB United Kingdom Registration Number: T: F: devizes@gems-group.com

4 DOCUMENT CONTROL AND REVISION STATUS Document Title Geophysics Results Report Volume 4 of 9 Project Client Project No. Document Ref. Dogger Bank Tranche A Acoustic and Geophysical Survey Forewind Limited GSL10109 Revision No. 03 Document Distribution Copy Number Distributed to Date Master GEMS Server 19 October GEMS 19 October This report is copy number: Signed: Revision History Date Orig. Chk. Appr. Client 00 Draft 20 September 2011 JMO/LJE/JTI JST 01 Issue to Client for Review 23 September 2011 JMO/LJE/JTI JST PHA 02 Issue to Client After Review 17 February 2012 JMO/LJE/JTI JST PHA 03 Issue to Client After Review 19 October 2012 JMO/LJE/JTI BBR PHA Signatory Legend: JMO Joseph Morris LJE Louise Jemmett JTI Jenny Tippin JST Jon Steer JMO Joseph Morris BBR Ben Barton PHA Phil Hayles The following personnel are the designated contacts for any queries regarding this document: Name Job Title Telephone Heath Turck Project Manager Heath.Turck@gems-group.com Ed Weare Project Manager Ed.Weare@gems-group.com GEMS International Group of Companies i

5 TABLE OF CONTENTS 1. INTRODUCTION Project Overview Objectives Document Overview Forewind Client Feedback GEMS Response SCOPE OF WORK Site Definition Line Plans Equipment Simultaneous Operations PROJECT CONTROL Horizontal Datum Vertical Datum Time Datum Units Datum BATHYMETRY Depths SEABED FEATURES Sediment Overview Sediment Transportation Existing Infrastructure Contacts SUB-BOTTOM GEOLOGY Unit a Unit b Unit c Unit d Unit e Unit f Unit g GEOPHYSICAL AND HYDROGRAPHIC INTERPRETATION Overview Slopes Near Surface Geological Discussion Sediment Sampling and In-Situ Testing POTENTIAL HAZARDS Shallow Gas Potential Peats Faults Small Bodies of Sand GEMS International Group of Companies ii

6 8.5 Channels / Soft Channel Infill Cobbles / Boulders Surface Obstructions LIST OF FIGURES Figure 1 Dogger Bank Zone...1 Figure 2 Lines Run by Kommandor Jack Figure 3 Lines Run by Aquarius Figure 4 Grid of fictional tidal stations Figure 5 Tidal Level Contours Figure 6 Colour banded bathymetry overview of Tranche A Figure 7 Shallow sandwaves observed in the bathymetric dataset Figure 8 Bathymetric profile across symmetrical sandwaves Figure 9 Low relief flat area, with WD 20-25m observed in the East of the Tranche A site Figure 10 Depths of 30m-40m in southeast of site, highlighting the base of the valley forms Figure 11 Depths of 30-40m along northwest boundary, delineating the base of valley forms Figure 12 Adapted Folk Sediment Classification Figure 13 SSS record of stiff clay with frequent cobbles and occasional boulders Figure 14 Predominance of sand across the Tranche A site Figure 15 SSS record of sand Figure 16 SSS record of stiff clay (occasional) and gravel Figure 17 Megaripples observed in the SSS mosaic Figure 18 SSS record of mixed sediment classification Figure 19 SSS record of mixed sediment classification Figure 20 SSS record of isolated gravel patches Figure 21 SSS mosaic of gravel patches Figure 22 Megaripple variations Figure 23 SSS record of sediment migration, 03 December Figure 24 SSS record of sediment migration, 21 December 2010; Figure 25 Areas of sandwaves identified in bathymetry (encircled in black) Figure 26 Sandwave direction, wavelength and amplitude Figure 27 Sandwave direction, wavelength and amplitude Figure 28 Magnetometer detected gas pipeline Figure 29 SSS mosaic of the detected SEAL gas pipeline Figure 30 Isolated Boulder (3.1x1.5x0.7m) Figure 31 Boulder Cluster (image extent 50 x 90m) Figure 32 Trawling activity in evident in gravel sediment Figure 33 Trawl scar termination at sediment boundary Figure 34 Wreck (ID 1000) identified in the bathymetric data (top) and SSS record (bottom) Figure 35 Wreck (ID 1001) identified in the bathymetric data (top) and SSS record (bottom) Figure 36 Wreck (ID 1002) identified in the bathymetric data (top) and SSS record (bottom) GEMS International Group of Companies iii

7 Figure 37 Geological schematic of Interpreted Sub-seabed Geology in Tranche A Figure 38 Shallow sub-bottom profile showing Unit a overlying Unit b Figure 39 Shallow sub-bottom profile showing the sand waves with exposed Horizon B Figure 40 Base of Unit b (depth in metres bsb) Figure 41 Thinning of Unit c in localised area of faulting; Figure 42 Acoustically transparent and chaotic internal structure of Unit c Figure 43 Base of Unit c (depth in metres bsb) Figure 44 Spatial illustration of depth BSB (m) to Horizon E, the base of Unit e Figure 45 Spatial illustration of depth BSB (m) to Horizon F, the base of Unit f. The red polygon depicts the area disturbed by faulting Figure 46 Representative sparker interpreted profile Figure 47 Overall Spatial Representation of Sediment Types in Tranche A Figure 48 Site slope values (degrees from horizontal) which highlights the valley locations Figure 49 Valley profile B-B (as indicated in Figure 48) Figure 50 Shaded colour depth BSB to Horizon B, interpreted to mark the surface of Unit c Figure 51 Colour banded illustration of bathymetry across Tranche A Figure 52 Zone A as defined from Seabed Features Interpretation Figure 53 Pinger SBP profile of Unit b overlying Unit c with evident seabed valleys Figure 54 Pinger SBP profile of sub-cropping/outcropping Unit c with incised Unit ci Figure 55 Bathymetric image of observed bedforms Figure 56 Zone B as defined from the Seabed Features Interpretation Figure 57 Shaded colour bathymetry with delineated gravel boundary located within a valley Figure 58 Sub-bottom profile showing sandwaves overlaying Unit c and seabed valleys coincident with outcrops of Unit c Figure 59 Zone C as defined from Seabed Features Interpretation Figure 60 Shaded colour bathymetry with delineated gravel boundary located within valley Figure 61 Shallow SBP profile showing surface geology within Zone C as found to the north Figure 62 Shallow SBP profile showing surface geology within Zone C as found in the west Figure 63 Shallow SBP profile showing surface geology within Zone C as found in the southwest Figure 64 Zone D as defined from Seabed Features Interpretation (South) Figure 65 Zone D as defined from Seabed Features Interpretation (West) Figure 66 Zone D as defined from Seabed Features Interpretation (North) Figure 67 Shaded colour bathymetry with the delineated Unit c exposure boundary coincident with a topographic valley Figure 68 Shallow sub-bottom profile showing the sub- outcrop of Unit c Figure 69 Shallow SBP profile showing sub-outcrop of Unit c and correlation with valley topography Figure 70 Profile showing apparent reverberation and acoustic blanking associated with gas presence. 75 Figure 71 Spatial illustration of the high amplitude anomalies observed across the site Figure 72 High amplitude anomalies present GEMS International Group of Companies iv

8 LIST OF TABLES Table 1 Report Volumes...2 Table 2 Dogger Bank Zone Coordinates...9 Table 3 Tranche A Boundary Coordinates (created from rev 1 line plan)...9 Table 4 Met Mast Locations...9 Table 5 Simultaneous Operations Table 6 Geodetic Parameters Table 7 Tidal Heights Table 8 Sediment Transport Definitions Table 9 Wrecks As found Table 10 Observed Depths of Geological Units Table 11 Slope Categories Appendix A Seabed Features Target Database Appendix B Figure Base Map LIST OF APPENDICES GEMS International Group of Companies v

9 GLOSSARY OF TERMS AND ABBREVIATIONS A list of abbreviations that may have been used within the main body of the report λ Wavelength ATT Admiralty Tide Table BSB Below Sea Bed C-O Computed - Observed CAD Computer Aided Design CM Central Meridian CPT Cone Penetrometer Testing DF Dual Frequency DGPS Differential Global Positioning System GSL GEMS Survey Ltd GPS Global Positioning System HAT Highest Astronomical Tide HF High Frequency HSE Health Safety and Environment KHz Kilohertz km Kilometre LAT Lowest Astronomical Tide LF Low Frequency m Metre MBES Multibeam Echo Sounder MRU Motion Reference Unit MSL Mean Sea Level MV Motor Vessel OPM Offshore Project Manager OTS Over the Side QA/QC Quality Assurance / Quality Control QINSy Quality Integrated Navigation System SBP Sub Bottom Profiler SSS Side Scan Sonar SVP Sound Velocity Profile UK United Kingdom UTC Universal Time Co-ordinated UTM Universal Transverse Mercator WD Water Depth (corrected to LAT) WGS84 World Geodetic System 1984 GEMS International Group of Companies vi

10 1. INTRODUCTION 1.1 Project Overview GEMS Survey Ltd. (GEMS) were contracted by Forewind Limited (the Client) to undertake a bathymetric and geophysical survey of the Tranche A development area and two met mast locations (which were later revised) within the Dogger Bank Zone, in addition to a cable reconnaissance from Tranche A to the Yorkshire coastline. The Dogger Bank Zone is located 122km off the coast of Yorkshire and extends to the median line between UK and European waters, as illustrated in Figure 1. Figure 1 Dogger Bank Zone Tranche A is an area of approximately 2000km 2 and lies in the southwest section of the Dogger Bank Zone. The Tranche A and met mast surveys comprised acquisition of side scan sonar, sub-bottom profilers, bathymetric, acoustic ground discrimination (AGDS) and magnetic anomaly data. The cable reconnaissance survey consisted of bathymetric and sub-bottom profilers. GEMS International Group of Companies 1

11 1.2 Objectives The primary objectives of the survey were to produce sufficiently high resolution bathymetric and geophysical data and interpretations to allow regional interpretation for planning and modelling purposes; for met mast design to commence and to provide high quality data to inform further benthic and environmental surveys. These objectives were met by acquisition of the following datasets: Bathymetric data to establish the site depths and bathymetric profiles. This data is also used for acoustic ground discrimination (ADGS), in order to identify different environmental habitats and sedimentation patterns at the seabed to inform the design of the environmental survey. Side scan sonar to identify any seabed features and verify the position of existing infrastructure (e.g. pipelines), with a particular emphasis on identifying hazards to future engineering works, and to inform the design of the environmental survey and of appropriate ground truthing locations. Sub-bottom profiler data in order to characterise in high resolution the stratigraphy of the site to a minimum depth of 50m below seabed. This was achieved by utilising both pinger and sparker profilers, and the characterisation placed particular emphasis on identifying hazards, such as gas charged bodies and faults, to future engineering works, and to identify suitable locations for subsurface sampling. Magnetic data to verify the position of existing infrastructure and identify any unknown ferrous bodies that may pose an obstruction or hazard to future engineering works. Drop down camera transects to allow seabed habitat classification (at met mast locations). 1.3 Document Overview The reporting of this survey campaign has been broken down in to aid accessibility. The full listing of all final reports is available in Table 1. Table 1 Report Volumes Volume Description Document Reference 1 Operations Report: MV Aquarius GSL10109-OPS Operations Report: MV Kommandor Jack GSL10109-OPS Processing and Interpretation Report GSL10109-OPS Geophysical Results Report 5 Original Met Mast W Report GSL10109-GPH-OF002 6 Original Met Mast X Report GSL10109-GPH-OF004 7 Alternate Met Mast W Report GSL10109-GPH-OF006 8 Alternate Met Mast X Report GSL10109-GPH-OF007 9 Cable Route Reconnaissance KP Descriptions GSL10109-GPH-OF003 GEMS International Group of Companies 2

12 1.4 Forewind Client Feedback GEMS Response The following Client Feedback / Response was issued 22nd February 2012: The following client comments have been addressed along with the report and charts. Missing volumes Delivered to client on 27 th January. Volume 1 Operations report M/V Aquarius Volume 2 Operations report MV Kommandor Jack Volume 3 Processing and interpretation report Multibeam Bathymetry Data The multibeam bathymetry data displayed evidence of minor tidal correction discrepancies, the result being stripy looking data grids with differences of over 0.5m identified between some lines (Figure 1). This does not significantly affect the appearance of large scale features, but could make identification of smaller objects such as small wrecks problematic, especially if such features cross between survey lines. Even if such features can be identified, any absolute depth readings taken would be inaccurate. The tidal correction problem also makes the provided gradient analysis spurious, as the only real areas identified by this analysis are the data steps observed between survey lines. Additionally, one file (DBA_425_6070) appears to have data missing, both from the.sd files and the original.xyz file. All depth readings below -32.8m are not present, meaning data from a significantly large area of this section of Tranche A is missing from the data supplied to WA. Please add any abbreviations to the glossary - and refer to LAT Please take section Zone A to Zone D and place it in here with each section split into Bathymetry, Seabed Features including sediment transport and near subsurface soils these should incorporate all the relevant sections of bathymetry and seabed features & sediment transport that are currently in separate sections because there is a huge amount of duplication. For example Figure 7 and 47 are the same! Please move part of section 6 to here call it 'Geophysical and Hydrographic Interpretation' - then section 6.1 Overview with Figure 41 and Figure 44 the zones of similarity are the best way to describe the bathymetry and seabed features of the region. This does not match the 'as supplied' slope information' there are a huge number of artefacts in the data which suggest slopes of in excess of 30 degrees. Please define how the slope information was derived and the filters used to remove the artefacts in order to get this information out Acknowledged and agreed but data reduced by predicted tides resulting in these errors. GEMS now operate using real time tidal corrections. Corrected and to be delivered to client in the final data drop. WD added to glossary. Vertical datum section states that all depths are corrected to LAT. Duplicate Figure removed. Each system / dataset has been introduced prior to the detailed zonal section. For clarity the whole document cannot be discussed in zones as the same features would need to be introduced for each zone, an overview prior to the zones is preferred. This has been discussed with Leo James. Some reconfigurations of the sections have been made to help clarify and avoid duplication. Bathymetry is introduced for the whole area described in water depths of 10-20, 20-30, etc then in detail in the zones of similarity (as above comment). The slope image in Figure 12 is a result of data that has been gridded at a larger (10m bin) interval than in the data issued digitally (1m bin). This explains why there appears to be slopes in excess of 30 degrees in the supplied 5km x 5km block digital data. A comment to this affect has been added to the report to explain the process. Sidescan Sonar Data The sidescan sonar data were provided as.xtf files. Although no survey or operations report were provided, the survey logs indicate that the data were positioned using a mixture of a cable counter and USBL data and the positioning appears to have been included with the data files. A number of problems were encountered with the sidescan sonar data, though judging by the quality of the mosaics created by GEMS (provided as images), it is unclear whether this is a reflection of the data quality itself or is an artefact of how Coda has visualised these particular files. There appears to be a problem with the navigation in All data acquired using USBL positioning but cable counter recorded as standard practice and for verification purposes. The GEMS in house software InfoX was utilised for SSS processing. Online acquisition is set up with the strings necessary for InfoX processing. The processed xtfs were exported from InfoX and have a slightly reduced resolution to that in InfoX. The final navigation used to generate the mosaics is GEMS International Group of Companies 3

13 most of the files which prevents the data being displayed correctly in mosaic. However, this again can be corrected for by a number of processing steps. Although this processing flow does not take a particularly long time to work through for an individual file, the sheer number of files for this project would mean a significant amount of extra processing time would be required to correct all of the files should further interpretation work be deemed necessary. The sidescan sonar data itself is often very spiky, causing problems when attempting to equalise the gains and display the data. Additionally, the speed of sound in water for the survey seems to have been recorded incorrectly, as the data files show a range that is twice that recorded in the survey logs. Additional to the data display problems, the data itself appears of an average quality, with a degree of sea surface noise, interferences from other equipment and snatching visible on many of the records viewed. Further differences in interpretation processes were highlighted during the gap analysis. The first were two anomalies, one a large contact 5m high and the other a depression 7m deep (GEMS ID DBA_S3130 and DBA_S1314 respectively), that could not be identified at their given positions on the sidescan sonar data, nor could they be identified on the multibeam bathymetry data. This suggests either a positioning or measurement error, but either way highlights inconsistencies between two different interpretation processes. identical to that included in the processed xtfs. It is unfortunate that you have to take additional steps to read in the data correctly. If the format of the xtfs is incorrect then please give further feedback so our software developer can address this. Similar corrections have been made during processing. Variable gains believed to be a function of the influence of the towed magnetometer and associated cabling, which causes the fish to list, and also the variable currents experienced. This problem has been identified. The XTF header has been populated with the correct speed of sound 1507m/s however it appears that some packages do not take TWTT into account. The velocity will be halved in the headers for the next issue of the data to ensure that it reads into Coda correctly providing the correct range. Surface noise and cable snatch is apparent in some cases and is unfortunately unavoidable in shallow water (with undamped small cable outs), particularly when operating in marginal weather. Interference is also an issue as the cable out in shallow water is insufficient to provide separation from the Sparker source. These contacts are visible in the high resolution dataset of InfoX however the heights are inaccurate and have been revised to 2.7 and 3.4 for S3130 and S1314, shown as follows (both close to the water column) Furthermore, it is unclear why a large pipeline clearly identifiable on both the sidescan sonar and multibeam bathymetry data was not highlighted by GEMS, though it is present in their gazetteer of magnetic anomalies. Any other anomalous target sizes have been verified. The pipeline and 2 cables have been digitised as part of the geophysical interpretation and has been included in the charts. It appears that this digitisation may have been omitted from the latest shape file delivery. This has now been included. Sub-Bottom Profiler Data The pinger data is of good quality and shows shallow features in high resolution. Despite this, however, one problem was encountered. The Kingdom projects were provided in a number of blocks. Of these, Block 3 appears to be of significantly lower quality than the others, with very little penetration, poorer resolution and a higher degree of background noise. Given the good quality of the other data, it is possible that this is the result of the use of a different processing sequence and is not a reflection of the data itself; though without raw data this cannot be verified. During the review of these data sets, a number of features/layers of potential archaeological interest (e.g. small channels, possible peat layers) appear to have been omitted from the provided interpretation (Figure 3). This would obviously prove problematic For the duration of Block 3 the Aquarius was utilised. The initial set up onboard was a 2x2 pinger array as the moonpool was adapted to carry both the pinger elements and the MBES system. The pinger data was identified to be of poor quality in relation to the Kommandor Jack and the onboard systems were later reconfigured to allow the installation of a 4x4 array, to match the Kommandor Jack. The high data quality, data volume and geological complexity limited the interpretation of the dataset to the critical lithostratigraphy. Attempts were made to identify shallow GEMS International Group of Companies 4

14 were this interpretation solely used for an archaeological review. It is understood that the provided interpretation was not the final version, though the frequency with which such features were omitted suggest they would also be missing from the final interpretation, as whilst they are of archaeological importance they may not be critical to defining the lithostratigraphy and associated geotechnical attributes. Following investigation of the GEMS geophysical survey report, the major concerns regarding the interpretation presented are a series of channels that do not appear to have been identified. Sub-Surface Geology Interpretation Unit b A number of instances of missing data are marked on the unit b isopach provided. However, there is no mention of how much data is missing. This information should be contained within the report. Other areas in unit b are marked Uninterpretable in record. GEMS define unit b as Holocene sediments. In this area, Holocene sediments are generally sandy in nature (see BGS Swallow Hole and California Quaternary Geology charts). Figure 64, in the GEMS geophysical survey report, presents the interpreted base of unit b. An area of approximately 170 km2 in the central east of the Tranche is labelled Horizon B main lines not interpretable. The relevant isopach shapefile provided, shows large areas where unit b has not yet been interpreted by GEMS. On page 65 of the GEMS geophysical survey report it states that: The depth of the horizon in the centre of Zone A is beyond the penetration of the pinger and can be seen as a very shallow horizon in the Sparker data. If this is the case then unit b should be interpreted from the sparker and not the pinger data. As it stands there is no information concerning the thickness of the top sedimentary unit for a large proportion of the Tranche. It seems likely from reading the zonal survey and geotechnical reports that these areas marked uninterpretable in record correspond to the shallow channel system observed by Gardline and the sandy unit recorded in geotechnical samples recovered by Fugro. Horizon B recognised as likely Bligh Bank Sands only top section of the Holocene sequence included within GEMS interpretation - additional work has been completed on Holocene sands section report and latest image included for reference. Unit c Figure 67, in the GEMS geophysical survey report, displays the interpretation of Horizon C (the interpreted base of unit c ). The stated scale is Depth in metres. It is assumed that this refers to depth below seabed (mbsb). However, this requires clarification. It is also noted that the displayed depth range is 15 to 60 m and that at times the horizon is interpreted to be within <1 m of the seabed. These two ranges are contradictory. If the base of unit c shallows to within 1 m of the seabed then it follows that it must be present between 15 and 1 m. However, this horizon does not appear to have been interpreted at these depths. It is also noted that Horizon C (base of unit c ) is interpreted as not present over an area of approximately 180 km2 in the west of Tranche A. From investigation of the isopach C shapefile, provided, it is apparent that Horizon C is interpreted at between 25 and 35 mbsb on the boundary between presence/absence of unit c. This implies that, in this location, unit c is truncated at depth and replaced in the sedimentary column by another unit. GEMS explain this by suggested glacial faulting (see p. 67). However, the OMM geologist is sceptical of this interpretation for a number of reasons: not least because in the zonal survey, Gardline identify a major channel at this location. In any case, the interpretation presented by GEMS is not consistent with truncation via faulting. features but we appreciate we may have omitted the interpretation of features critical to archaeological review. Further insight into archaeological surveys has been beneficial to GEMS development. In future projects more time will be set aside to achieve this. The missing lines are to be identified clearly in the charts so that remaining interpretation gaps correspond to uninterpretable alone. Data has been interpreted in a conservative way to try to avoid misinterpretation, in areas where horizons are unclear. This has a significant effect on the areas acquired with the 2x2 array. It is acknowledged that Forewinds have continued the interpretation in these areas. Attempts were made to use the sparker data to complete the pinger interpretation however the wide seabed pulse, which overwrites the data, and the increased wavelength of the data made accurate delineation too difficult to continue. See previous comment regarding shallow features. GEMS acknowledge this discrepancy in light of the new interpretation and geotechnics, where horizon B now represents the likely base of the Bligh Bank Sands and Unit A the base of the Holocene sediments. A comment in the report has been added to explain. The scales on all of the depth below seabed images have been checked and tally with the table. Depth below seabed has been stated in the vertical datum section of the report. Faulting of the glacial deposits is observed as most clearly shown in Figure 41. This has now been identified by the BGS study. It is possible that Horizon C occurs at shallower depths but the record is difficult to interpret without geotechnical input. GEMS International Group of Companies 5

15 From the data presented in the GEMS geophysical survey report, it is noted that the other units interpreted as being present in this location are b, e and f. Unit b is interpreted as being relatively shallow (generally 2 4 m, though with a maximum thickness of 14 m in the far west). It is difficult to assess the thicknesses of units e and f as OMM have not been provided with isopachs for these. However, using values based on figures 68 and 69 in the GEMS geophysical survey report, unit e has a minimum depth value of 100 mbsb and unit f seems to have a depth of somewhere between 15 and 50 mbsb (from the symbology used in Figure 69 it is very hard to tell). GEMS interpret unit c as the Dogger Bank Formation, unit e as the Yarmouth Roads Formation and unit f as the Swarte Bank Formation. Of these, the Dogger Bank Formation is the most recent, followed by Swarte Bank Formation, with the Yarmouth Roads Formation the oldest. Again the scales on all of the depth below seabed images have been checked and tally with the table. Unit e is in fact the Swarte Bank formation and Unit f the Yarmouth Roads. BGS checking/re-mapping GEMS horizon C within Tranche A First activity was to identify large buried mound that sits atop horizon C (Fig 1) and to separate it from actual horizon C. Feature is clearly distinct. Unfortunately there is no core atop the mound to test its composition. o We ve made a separate, coarse interpretation of this feature and removed it from the GEMS Horizon. (Fig 2) Picking discrepancies: The next task was to check the GEMS horizon and try and fill in blank areas where the interpretations had not made. This analysis revealed a fair amount of inconsistency in the GEMS pick but also the complexity of mapping the base Dogger Bank. Rather than correct their horizon, we decided to create a new coarse (every 5-10 lines) in the interest of time. o This horizon is intrinsically difficult to map due to regular interference of seabed multiple. o Summary: We believe that what they have mapped as C is largely the Top of Egmond Ground (EG), rather than base Dogger Bank (DB). Where they have mapped base Dogger Bank, they have not mapped the top Egmond Ground. We have gone back and mapped this horizon in this area (Fig 3). We suggest that the base DB is often a weaker reflector than top EG. According to several boreholes (eg 1014), there is an irregular sand body sitting between what is presumably EG and DB. Laterally, it is of varying thickness 0-20m). (Fig 4). So where this unit is absent (or can t be distinguished on seismic), the GEMS C horizon is the base DB. We have begun to coarsely map the base DB, where GEMs have only mapped the top EG (Fig 5). I ve done a quick difference map (Fig 6) Colour scheme on seismic interpretation: Pink (GEMS horizon C); Purple (BGS interpreted top Egmond Ground); Red (BGS reinterpreted base Dogger Bank); Yellow (Seabed and seabed multiple); light blue (GEMS D); dark blue (GEMS E - Swarte Bank). Channels: Sometimes GEMS pick channels dropping off top EG, and sometimes they draw straight line across. In our re-mapping exercise, we will not incorporate channels into our re-interpretation of the base DB. Blank Areas: We broadly find that areas they have not mapped are either due to presence of channels, or deformation in the DB which has deformed underlying units as well. As a note, this deformation of underlying units is quite common. GEMS value the feedback received from Forewinds. The potential Esker mound is of particular interest and was not reported during the interpretation of the main stratigraphic units. GEMS appreciate that the interpretation is evolving and that mistakes have been made due to the complexity of picking the base of the Dogger Bank. An additional explanation has been added to the report to reflect this. We find often that it is possible to coarsely trace across these areas joining reflectors either side. But it should be noted that the geotechnical properties within these zones will almost certainly be different from undisturbed strata. GEMS International Group of Companies 6

16 The following Client Feedback (to Rev.2 of this report, February 2012) was subsequently received 8 th October 2012, with comments incorporated into the current document. Document Geophysical Survey Report - Document Review GEMS International Dogger Bank Tranche A:- Acoustic and Geophysical Survey Geophysics Results Report Volume 4 of 9 Document No. Revision 2:- Issue to Client after review Date of issue 17 th Feb By:- RAB Date:- 5 th October 2012 Approved:-LJ Date:-8 th October 2012 Overall Comments There has been considerable development of the geological model, however what is presented is fair reflection of what is present and has contributed significantly to the development of the model. There needs to be a consistent approach to the report as regards naming conventions, text and Figure presentation. Page Section Location Comment Action General When discussing directions e.g. section Correct throughout South East write as southeast (all one word). Other points of the compass should be written as south and SSE etc. General All figs that include sonar data need an along Add throughout. track and cross track scale. Mosaic data examples will need a scale. General All figs that include examples of the seismic data Add where applicable. need a vertical scale in metres. At the very least it needs to be annotated what the vertical scale is(two way time but preferably meters). 2 (new) 1.4 New section Can you insert the document dated 22 nd Feb 2012 as section 1.4 and give it the same title ie.. Add. Response is acknowledged. Forewind Client Feedback GEMS response vii glossary WD Water Depth (corrected to LAT) add rd para. 1 st Sub-bottom profiles should read Sub-bottom correct sentence profilers st para Survey data for Alternate Mast West (previously correct W) nd para Survey data for Alternate Mast East (previously correct X) rd para, last.but stiff clay. correct sentence New section Insert section title Stiff clay outcops add New section Insert section title Stiff clay and gravel add rd para, 1 st Change boulder clay to stiff clay correct sentence New section Insert section title Mixed sediments add New section Insert section title Gravel patches add Table 8 Add λ to the Glossary as Wavelength add 29 Fig 25 Add an X to mark location of figs 26 and 27 and add annotate relevant X st para, 2 nd Sub bottom profiler dataset but should be correct sentence changed to and nd para,2 nd Anomaly amplitudes should be changed to correct sentence magnetic anomalies 32 Fig 29 SEAL should be in capitals Correct also in List of Figs page iv nd para, 2 nd Anomaly amplitudes should be changed to correct sentence magnetic anomalies rd para, 2 nd Anomaly amplitudes should be changed to correct sentence magnetic anomalies th para Place these details into a table. Along with as amend given and as found positions st para, 1 st 3 identified wrecks discussed in section 0 correct GEMS International Group of Companies 7

17 Page Section Location Comment Action sentence should be section st para Move to next page so it goes with the trawl scar amend figs Table 9 In the coloumn header Height. (Depth) should be correct changed to (m) 41 6 Fig 37 Change cartoon to schematic needs to be amend done in the Figure list as well on page v nd para, 1 st Delete the s on the end of Forewinds correct sentence rd para, Shouldn t it be Dave Long not Brian Long? Check. last sentence rd para. Formation should have a capital F Correct all nd para. 2 nd 2 examples were boulder clay should read stiff correct sentence clay nd para. 3rd Change higher water depths to greater water correct sentence depths rd para. Beginning the relative benign. Move so it amend comes after Fig50 56 Fig 50 Add note as in fig40 regards uninterpretable add section nd para Mention Botney Cut channels at the surface in add Zone A st Para 2 nd Beginning The average amplitude. Remove amend sentence this but ensure it is covered in the SBF section nd para. 2 nd Beginning the bathymetry indicates amend sentence Remove this but ensure it is covered in the bathy section nd para. 5 th Remove the word thin from in front of veneer, amend sentence a veneer is by definition, thin th para Beginning few sonar contacts Remove this amend but ensure it is covered in the SBF section nd para 1 st Rewire to focus less on bathy.suggest amend and 2 nd sentences Sandwaves are present only in 20% of the zone, mainly in the shallow areas st Para Beginning few sporadic sonar contacts amend Remove this but ensure it is covered in the SBF section rd para, 2 nd Beginning the average amplitude Remove amend sentence this but ensure it is covered in the bathy section rd para, 1 st, again oriented with the flow regime should be correct sentence orientated st Para Beginning There are few. Remove this but amend ensure it is covered in the SBF section. 71 Check page numbering as there are two page Amend 71 s nd para, 2 nd sentence the interpreted Dogger Bank Formation capital F correct GEMS International Group of Companies 8

18 2. SCOPE OF WORK 2.1 Site Definition Tranche A The Dogger Bank Zone, and Tranche A are defined by the coordinates (WGS 84, UTM 31N) in Table 2 and Table 3. Easting Table 2 Dogger Bank Zone Coordinates Northing Table 3 Tranche A Boundary Coordinates (created from rev 1 line plan) Easting Northing Met Mast Locations The Met Mast locations are 1km by 1km surveys based around the locations in Table 4, provided in WGS84, UTM Zone 31N. Table 4 Met Mast Locations Met Mast Easting Northing Original Met Mast W Original Met Mast X Alternate Met Mast West (previously W) Alternate Met Mast East (previously X) GEMS International Group of Companies 9

19 2.1.3 Cable Route Reconnaissance Cable route reconnaissance lines were run during periods of marginal weather when work on Tranche A was not possible. Lines were run at arbitrary 5km intervals within the Project One corridor. No lines were run within the 12 nautical mile limit from the UK coast. 2.2 Line Plans Line plans were provided by RPS, a consultant to Forewind, and were designed to run perpendicular to the expected strike of the geology across the region. The line orientations matched the Zone Wide Survey (ZWS) performed in spring Tranche A Survey Main lines were orientated at 43 /223 and spaced at 100m intervals. Cross lines were orientated at 133 /313 and spaced at 500m intervals. All systems were logged concurrently during the single pass survey Met Mast Surveys (Original) Surveys were based on a 1km square orientated in-line with the Tranche A mainlines. Main lines were orientated as 43 and spaced at 100m intervals. Cross lines were orientated at 313 and spaced at 150m intervals. All systems were logged concurrently during the single pass survey. A more detailed magnetometer survey was conducted over the 100m immediately surrounding both proposed locations, with line spacing at 10m intervals for both main and cross lines. Environmental surveys were performed via drop down camera work at locations selected from the side scan sonar Met Mast Surveys (Alternate) Survey data for Alternate Met Mast West (previously W) was extracted from the main Tranche A survey data, with line spacing as per Tranche A (100m main lines, 500m cross lines). Survey data for Alternate Met Mast East (previously X) was acquired as a separate survey as it is outside of the Tranche A limits. The 1km square was orientated in-line with Tranche A mainlines, and line spacing as per Tranche A. All systems were logged concurrently during a single pass survey. No separate magnetometer survey was performed. No environmental investigations were performed. GEMS International Group of Companies 10

20 2.3 Equipment A full list of equipment is available in the operations reports; equipment types varied slightly by vessel but the following types of systems were run Seabed Topography Information on seabed topography was acquired using the following systems: Singlebeam Echosounder R2Sonic 2024 Multibeam Echosounder SEA SWATHplus interferometry system Seabed Features Information on seabed features was acquired using the following systems: Edgetech 4200 FS multi-pulse side scan sonar G882 or SeaSpy Magnetometer Geophysics Information on geophysics was acquired using the following systems: GeoAcoustics Hull Mounted Pinger Geo-Spark 800 Geo-Resources sparker (Geo-Spark 200 as redundant spare), with a TL3 multichannel recording system. 2.4 Simultaneous Operations Both the MV Kommandor Jack and the MV Aquarius undertook acoustic and geophysical operations as part of the Tranche A surveys. Tasks were completed as per Table 5. The terminology used to describe the areas completed by the vessels was Blocks 1 through 4. The Aquarius completing the northern most Block 1 and central Block 3 and the Kommandor Jack an adjacent central Block 2 and southern most Block 4. This is illustrated in Figure 2 and Figure 3. GEMS International Group of Companies 11

21 Table 5 Simultaneous Operations Single Pass Survey Separate Survey Singlebeam Echosounder Multibeam Echosounder SEA Swath Side Scan Sonar Magnetometer Pinger Sparker Environmental Magnetometer Tranche A Mainlines Tranche A Crosslines Original Met Mast W Original Met Mast X Alternate Met Mast W Alternate Met Mast X Cable Route Reconnaissance KJ/AQ KJ/AQ KJ/AQ KJ/AQ KJ/AQ KJ/AQ KJ/AQ - - KJ (infill only) KJ KJ KJ KJ KJ - - KJ - KJ KJ KJ KJ KJ AQ KJ KJ - KJ KJ KJ KJ KJ AQ KJ KJ/AQ KJ/AQ KJ/AQ KJ/AQ KJ/AQ KJ/AQ KJ/AQ - - AQ AQ AQ AQ AQ AQ AQ - - KJ KJ KJ KJ = MV Kommandor Jack AQ = MV Aquarius GEMS International Group of Companies 12

22 Figure 2 Lines Run by Kommandor Jack Figure 3 Lines Run by Aquarius GEMS International Group of Companies 13

23 3. PROJECT CONTROL 3.1 Horizontal Datum Geodetic parameters were specified by Forewind and entered into the online (and other relevant systems) as displayed in Table 6. All Easting and Northings are provided in the working projection (UTM 31). Table 6 Geodetic Parameters Working Spheroid Datum: WGS84 Projection: Spheroid: WGS84 (GRS1980) Conversion Factor to metres: Working Projection Universal Transverse Mercator Zone Semi-major, a: Longitude Origin: E Semi-minor, b: Latitude Origin: N Flattening, 1/f: False Easting: Eccentricity, e 2 : False Northing: 0 Comments/notes Scale Factor on CM: Units: m 3.2 Vertical Datum The vertical datum for this project is LAT using predicted tides. Twenty seven fictional stations were spaced across the site using co-tidal charts on predicted tide from the River Tyne station. The following was supplied to the vessel to enable this to take place: UKHO Admiralty Tide Table NP UKHO Admiralty Chart 5058 (Co-Tidal / Co-Range North Sea) QINSy Software Figure 4 Grid of fictional tidal stations Predicted tide was calculated for the survey period using harmonics for River Tyne which was the closest primary port to the survey area and also proved to be the most suitable station, as it provided the largest GEMS International Group of Companies 14

24 tidal range for the co-tidal model calculations. Chart 5058 was then used to calculate the Mean High Water Interval (MHWI) and Mean Spring Range (MSR) for each fictional station. Adjustments for the twenty seven fictional stations using the predicted tide at River Tyne were then made and a linear co-tidal model was built in QINSy which was then applied to the data. LAT and HAT tidal values at each fictional station can be found in Table 7 below. All figures quoted below are in relation to MSL. Table 7 Tidal Heights Station Number Easting Northing LAT (m) HAT River Tyne GEMS International Group of Companies 15

25 Figure 5 shows the relationship between LAT and HAT throughout the site depicted in contour form. Again all heights are quoted in relation to MSL. Figure 5 Tidal Level Contours Sub-bottom profiler depths are provided with respect to the seabed. Values for all horizons are stated in metres below seabed (mbsb). 3.3 Time Datum All systems have been interfaced to the DGPS system, with critical systems being linked to the 1 Pulse Per Second (PPS). All systems are set to log in UTC. Daily Progress Reports (DPRs) are in Local Time (BST). 3.4 Units Datum All systems are set to log using the SI (metric) system. All units in this report are in SI units unless quoted otherwise. GEMS International Group of Companies 16

26 4. BATHYMETRY The bathymetric data set was collected with an R2 Sonic 2024 Multibeam Echosounder interfaced through QINSy and processed using Fledermaus. The following sections provide a brief introduction to the Bathymetry observed across the entire Tranche A site. The bathymetry is then discussed in more detail in the Geophysical and Hydrographic Interpretation, Section 7, where the Tranche A site has been split into similarity zones A through D. 4.1 Depths Figure 6 shows the Tranche A site, colour banded by depth (LAT), as follows: < 20m (red) 20 to 30m (green) 30 to 40m (blue) > 40m (white) Figure 6 Colour banded bathymetry overview of Tranche A The following sections outline the major bathymetric features and characteristics associated with the aforementioned depths bands defined across the site. GEMS International Group of Companies 17

27 4.1.1 Less Than 20m WD The areas of less than 20m WD predominantly reside in the south and west of the Tranche A site at the summit of the valley forms which can be observed in the locality. Sandwaves are occasionally observed in depths less than 20m. Such occurrences are illustrated in Figure 7 and are centred on E, N (19.87m WD) and E, N (19.94m WD). Figure 7 Shallow sandwaves observed in the bathymetric dataset. GEMS International Group of Companies 18

28 These sandwaves are predominantly symmetrical in cross section as illustrated in Figure 8. Figure 8 Bathymetric profile across symmetrical sandwaves. Centred on E, N. GEMS International Group of Companies 19

29 m-30m WD Depths of 20-30m dominate the site, as illustrated by the green areas of Figure 6. There is a large low relief area of seabed in the Southeast of Tranche A, which shows depths ranging from 20-25m as outlined in Figure 9. 1 km Figure 9 Low relief flat area, with WD 20-25m observed in the East of the Tranche A site. The sandwaves observed across the site are most dominant in this water depth range. The nature of the seabed in WD 20-30m is of relatively low relief in comparison to the features observed at deeper depths. GEMS International Group of Companies 20

30 m-40m WD Depths of 30m-40m can be observed towards the base of the valley features to the southeast and northwest, as displayed in Figure 10 and Figure 11 respectively. Figure 10 Depths of 30m-40m in southeast of site, highlighting the base of the valley forms. Figure 11 Depths of 30-40m along northwest boundary, delineating the base of valley forms GEMS International Group of Companies 21

31 5. SEABED FEATURES Side scan sonar and magnetometer data were reviewed in conjunction with the bathymetric datasets in order to analyse the seabed characteristics. These characteristics include the following: Interpreted sediment type Sedimentary bedforms Sonar contacts Magnetometer contacts Potential hazards at the seabed Side scan sonar data was acquired using an Edgetech 4200MP towfish. Magnetometer data were acquired with a Marine Magnetics SeaSpy or GeoMetrics G882 magnetometer. The magnetometer was towed directly behind the side scan sonar towfish with a layback of 10m. Correlations were then made between identified magnetic anomalies and the side scan sonar record. The figures provided in this and subsequent sections have been provided with a centre position for reference. An accompanying base map to show these locations is provided in Appendix B for spatial reference to the Tranche A site. GEMS International Group of Companies 22