A FINAL REPORT BY PARTRAC LIMITED: MAY 2006

Transcription

1 A FINAL REPORT BY PARTRAC LIMITED: MAY 26 Measurement of Suspended Sediment Concentration & Tidal Current During Dredging Operations and Post-Dredge at the Offshore Disposal Area, Poole, Dorset

2 QUALITY CONTROL SHEET Publication title Client Ref: Version Measurement of Suspended Sediment Concentration & Tidal Current During Dredging Operations and Post- Dredge at the Offshore Disposal Area, Poole, Dorset RNA/MD/ Final Report Date May 26 File Reference PHC\SSM\1 Prepared under the management of: Kevin Black Project Manager Reviewed and approved by: Peter Wilson Director Client Address: Engineering Department Harbour Office Poole Harbour Commissioners 2 New Quay Road Hamworthy Poole Dorset BH15 4AF Dick Appleton (Harbour Engineer) Tel heng@phc.co.uk Contact Details: Ltd 141 ST James Road Glasgow G4 LT UK Kevin Black (Project Manager) Tel +44 () Fax +44 () kblack@partrac.com Web

3 EXECUTIVE SUMMARY Poole Harbour Commissioners (PHC) commissioned Ltd to collect data on suspended sediment concentration (turbidity) and current speed and direction at the offshore dredge disposal area outside Poole Harbour, Dorset. deployed a monitoring rig with back-up sensors at a single location ( N, W) for a total period of 51 days to include periods of normal dredge disposal operations and periods of non-dredge disposal operations. The location of the monitoring site was provided to by PHC. In parallel the dredge contractor (Van Oord) deployed a surface buoy to monitor surface suspended sediment concentrations. Two Nortek Aquadopp current meters with integral Seapoint turbidity sensors were deployed in a seabed frame at the monitoring location. The measurements were recorded at.6m above the seabed. The initial deployment was undertaken at 11:5hrs on the 21/1/6 and was recovered on the 15/3/6 at 12:35. The data was downloaded, checked and assessed for quality. The entire data record was judged to be of high quality. All times are quoted in GMT (24hrs). Suspended sediment concentration is given in milligrams of sediment per litre of seawater (mgl -1 ). All current directions are quoted in degrees relative to true north ( o T). The units of current flow speed are metres per second (ms -1 ). The following conclusions from the metocean and dredging data have been derived: Coastal oceanographic conditions at the Poole Harbour offshore dredge spoil disposal ground are typical of tidally driven coastal environments. A strong Neap-Spring tidal regime is evident with typical peak Neap tidal current velocities of.3 to.5 ms -1 and typical peak Spring tidal velocities of the order.8 to 1.1 ms -1. Both Neap and Spring tidal currents are sufficiently strong to induce sediment resuspension at the bed and there is a distinctive correlation of tidal current velocity and suspended sediment concentration. This correlation is evident from both the bed and surface monitoring. Nearbed suspended sediment concentration values range from 8 to 1 mgl -1 (slack tide background) increasing to 3 to 4 mgl -1 during strong Spring tides. Occasional large, short-lived peaks in nearbed suspended sediment concentration up to ca. 85 mgl -1 ) were recorded. Surface values of suspended sediment concentration range from 1.5 to 17.5 mgl -1 although occasional increases to a maximum of 3.16 mgl -1 were observed. Higher values of surface suspended sediment concentration may be related to dredge spoil dumping activity, but it is not possible to state this unequivocally. PHC\SSM\1 1

4 CONTENTS EXECUTIVE SUMMARY 1 INTRODUCTION Background Project Aim Field Site 3 2. BEDFRAME EQUIPMENT Nortek Aquadopp Acoustic Current Meter Seapoint Optical Backscatter Sensor Deployment Frame 4 3. BED FRAME METHODOLOGY Field Deployment Summary Calibrations QA 5 4. THIRD PARTY DATA Surface Turbidity Monitoring Buoy Tidal Data Dredge Vessel Activity 6 5. RESULTS Summary Statistics Time-Series Data for the Total Monitoring Period Weekly Time-Series data Dredge Disposal Logs 7 6. GENERAL SYNTHESIS Data Interpretation Considerations Data Synthesis 9 7. CONCLUSIONS 1 APPENDICES Turbidity Sensor Calibration Graphs Tabulated Weekly Summary Statistics Time-Series Data for Total Monitoring Period Weekly Time-Series Data 2 5. Dredge Disposal logs 29 PHC\SSM\1 2

5 INTRODUCTION 1.1 Background PHC were requested by MCEU as a condition of their disposal license to undertake a minimum of 48 hours near-bed (<1m) monitoring of suspended sediment concentration (turbidity) near the offshore dredge disposal site. The monitoring was to be undertaken both during non-dredge disposal and during normal dredge disposal operations at the site. In parallel, the dredge contractor (van Oord) was required to monitor surface suspended sediment concentrations at the disposal site. 1.2 Project Aim The monitoring programme aimed to acquire turbidity and current data at a single site for a 48-hour (min) period of normal dredge disposal operations and a 48- hour (min) period of non-dredge disposal operations. 1.3 Field Site The field site was located at N, W (Fig. 1). Figure 1 Field Site Location, Poole Bay. PHC\SSM\1 3

6 2. BEDFRAME EQUIPMENT 2.1 Nortek Aquadopp Acoustic Current Meter Two Nortek Aquadopp acoustic current meter was used to record current speed and direction. The current meter was secured in the centre of the mooring frame to take measurements at.6m above the bed. The Aquadopp instrument was also used to log the suspended sediment concentration (turbidity). One data set only has been reported here. 2.2 Seapoint Optical Backscatter Sensor Seapoint optical backscatter sensors (OBS) interfaced with the Aquadopp instruments were used to record suspended sediment concentration. 2.3 Deployment Frame The equipment was mounted on a bespoke stainless steel seabed mooring frame, equipped with 8Kg of ballast, lifting shackles and standard J-configuration mooring arrangement (Fig. 2). A vertical sediment trap was also attached to the frame to collect suspended sediment. Figure 2 The various instruments mounted in the bed frame. Sediment Trap Aquadopp Current Meters OBS (Turbidity sensors) PHC\SSM\1 4

7 3. BED FRAME METHODOLOGY 3.1 Field Deployment Summary The Aquadopp instruments were programmed to log current speed, current direction and suspended sediment concentration every fifteen minutes for the duration of the deployment. The instruments were tested and in good order prior to deployment. The initial deployment of the monitoring rig was undertaken successfully at 11:5hrs on the 21/1/6 to cover the pre-dredge monitoring phase. The rig was deployed using PHC s Herbert Ballam tug boat at location ( N, W); the water depth at the time of deployment was 29.m. mobilised for recovery on the 22/2/6, however, the two marker buoys attached to the frame were not present. instructed a diver team and some local fishermen to search for the frame. On the 15/3/6 at 12:35hrs the frame was found and recovered by the local fishermen at a location about 1m south-west of the original deployment location. All instruments were intact and had continued acquiring data through-out this extended period. The data was downloaded and checked and was all of high quality. 3.2 Calibrations The current meter was pre-calibrated by the manufacturer. The bed frame OBS was post-calibrated in the field by using five varying concentrations of native suspended sediment. The water samples were then filtered across.45 µm Nucleopore filter membranes to determine the dry mass concentration (units mgl -1 ) of suspended sediment. The turbidity sensor calibration graph can be seen in Appendix QA operate a Quality Management System which outlines methods of good practice, procedures for bottom and suspended sediment sampling, use of sediment traps, bedframe deployments, and sensor calibrations. staff closely adhered to the guidance in this internal documentation through all field and laboratory monitoring, sampling, analysis and related work Data Loss There was no data loss associated with this deployment. PHC\SSM\1 5

8 4. THIRD PARTY DATA 4.1 Surface Turbidity Monitoring Buoy The dreding contractor (Van Oord) supplied, deployed and calibrated a surface buoy that measured surface (approx..5m below the surface) suspended sediment concentrations. It was deployed on 26/1/6 at 16:3hrs and recovered 18/2/6 at 14:4hrs ( total 24 days). The turbidity sensor was calibrated using water samples from the site, the calibration graphs can be seen in Appendix Tidal Data Tide height (m CD) data measured at the RoRo ferry terminal were provided to by PHC in electronic format. 4.3 Dredge Vessel Activity The spoil dump volume (m 3 of sediment disposed of at the spoil ground) of the Van Oord dredge vessels Volvox Scaldia (length 85.81m and draft 3.94m), Ham 311 (length 94.54m and draft 5.68m) and Waterway (length 97.7m and draft 6.58m) were recorded by PHC and were provided to in electronic format. PHC\SSM\1 6

9 5. RESULTS 5.1 Summary Statistics Weekly summary statistics for the bed frame and surface buoy suspended sediment concentrations, current speed and direction and dredge disposal volumes are given in Appendix Time-Series Data for the Total Monitoring Period Time-series data for the total monitoring period is presented in Appendix 3. These comprise time-series of current velocity (ms -1 ) and suspended sediment concentration (mgl -1 m above the bed (a.b.), water depth at the spoil ground (m), RoRo berth tide height (m CD), surface suspended sediment concentration (mgl -1 ) and dredge disposal logs. Good quality current data was obtained from the bottom mounted frame for the full deployment period (23/1/6 11:5hrs to 15/3/6 12:35hrs). Surface suspended sediment concentration data was obtained by the dredging contractor (Van Oord) between 26/1/6 at 16:3hrs and 18/2/6 at 14:4hrs, although there was poor data between 12/2/6 at 18:hrs to 13/2/6 at 4:5hrs and 13/2/6 at 21:3hrs and 14/2/6 at 18:2hrs. The poor quality data has been removed. 5.3 Weekly Time-Series data The weekly results are presented in Appendix 4 as 8 multi-parameter weekly synthesis panels. These comprise time-series of current velocity (ms -1 ) and suspended sediment concentration (mgl -1 m above the bed (a.b.), water depth at the spoil ground (m), RoRo berth tide height (mcd), surface suspended sediment concentration (mgl -1 ) and dredge disposal logs. N.B. There are two (differing) y-axis scales on both the tidal height and suspended sediment concentration graphs. 5.4 Dredge Disposal Logs The dredge disposal logs for the monitoring period 23/1/6 to 28/2/6 are shown in Appendix 5. The table shows vessel, disposal location, disposal time, area[s] dredged, material type, wind speed and direction and tidal height. PHC\SSM\1 7

10 6. GENERAL SYNTHESIS 6.1 Data Interpretation Considerations In this study, a monitoring programme was commissioned to measure the oceanographic environmental conditions at the dredge spoil dump ground offshore Poole Harbour, Dorset. A bottom-mounted monitoring rig was specifically constructed for this purpose (see Section 2) and measurements of tidal current speed and direction, water depth, and suspended sediment concentrations were collected at.6m above the bed for a period of 51 days. A data return of 1% was achieved. The data collected are considered to be of high quality. The Aquadopp instrument provideed consistently good measures of tidal current speed and direction. The optical turbidity sensors also performed reliably and calibrations using sediments retained within the frame-mounted suspended sediment trap provided strong linear correlations (Appendix 1) for the range of suspended sediment loadings observed at the monitoring site. The single major consideration when interpreting turbidity data is that low turbidity values can, in fact, be attributable to 2 differing causes. Firstly, it may be the case that current speeds are only just capable of resuspending the bottom sediments and therefore turbidity values can be rather low; alternatively, there may be a paucity of sediment available for resuspension and this also may be a reason behind low turbidity values. The time-series of tidal height at the RoRo berth and of water depth at the monitoring location are out of phase by approximately 1 hour; this is to be expected and is typical of the behaviour of tides in coastal marine environments. Both data sets are given in GMT Van Oord Surface Suspended Sediment Concentration Data A 3 rd party (Van Oord) collected sea surface suspended sediment concentration data using a telemetric buoy system. A single calibration was applied to the raw data values using samples of suspended sediment collected using a hand-held water sampler, this calibration graph can be seen in Appendix 1. The data from these buoy deployments are presented and discussed here. Whilst we are in a position to comment upon any trends in sediment concentration, we cannot substantiate the absolute (numerical) values of suspended sediment concentration. These are much less than corresponding data measured.6m above the bed on the monitoring frame, due to natural vertical variability in sediment concentration. PHC\SSM\1 8

11 6.2 Data Synthesis The oceanographic conditions at the spoil ground are typical of tidally swept coastal zones. A strong Neap-Spring tidal regime is evident with typical peak Neap tidal current velocities of.3 to.5 ms -1 and typical Spring tidal velocities of the order.8 to 1.1 ms -1 (e.g. Week 6). Both Neap and Spring tidal currents are sufficiently strong to induce sediment resuspension and there is generally a good correlation of peaks in suspended sediment concentration (at both the seabed and the surface) with tidal current peak velocities. The data from Week 2 provides a good example of this. Maximum nearbed suspended sediment concentrations are of the order 3 to 4 mgl -1 during Spring tides, decreasing slightly to between 1 and 15 mgl -1 during Neap tides. During slack tidal periods, suspended sediment concentrations drop to ca. 8 to 1 mgl -1 and this can be regarded as the general background turbidity situation. Occasional large, short-lived peaks in nearbed suspended sediment concentration (>6 mgl -1 ) were recorded. For example, on 2/2/6 at 4:3 (651.9 mgl -1 ) and 2/2/6 at 16:45 (853.8 mgl -1 ). These events may relate to wave action, which can augment the resuspension potential of tidal currents, however this cannot be substantiated this without relevant wave data from the site. A limited quantitative interpretation only can be provided with respect to surface turbidity on account of the 3 rd party nature of the data. Notwithstanding this, the observation of phase similarity between the bed frame and surface concentration values derived from the Van Oord monitoring buoy provide some confidence in the surface concentration datasets. There is a considerable vertical gradient in suspended sediment concentration and surface values are an order of magnitude and a factor of 2 lower than near-bed values. As noted there is a tidal signal, albeit a weak one, in surface turbidity with slack tide values around 1.5 to 7 mgl -1 and peak values of 12 to 3 mgl -1. During Week 4 (a period of Spring tides) there are two instances when surface suspended sediment concentration values exceeded 24 mgl -1 (e.g mgl -1 on 13/2/6 at 18:14hrs and 3.2 mgl -1 on 16/2/6 at 16:42hrs). Inspection of the dredge dump volumes, especially during the second of these periods, shows activity and dumping of 1164m 3 of silt/sand on 16/2/6 at 12:5hrs. It is possible that the increase in surface suspended sediment concentration may be related to a low residual mass of sediments in the water column post-dumping, but it is not possible to link these two observations unequivocally. Certainly, dredge spoil dumping is not observed to modify patterns and magnitudes of nearbed suspended sediment concentration (e.g. see Week 5). PHC\SSM\1 9

12 7. CONCLUSIONS The following conclusions from the metocean and dredging data have been derived: Coastal oceanographic conditions at the Poole Harbour offshore dredge spoil disposal ground are typical of tidally driven coastal environments. A strong Neap-Spring tidal regime is evident with typical peak Neap tidal current velocities of.3 to.5 ms -1 and typical peak Spring tidal velocities of the order.8 to 1.1 ms -1. Both Neap and Spring tidal currents are sufficiently strong to induce sediment resuspension and there is a distinctive correlation of tidal current velocity and suspended sediment concentration. This correlation is evident from both the bed and surface monitoring. Nearbed suspended sediment concentration values range from 8 to 1 mgl -1 (slack tide background) increasing to 3 to 4 mgl -1 during strong Spring tides. Occasional large, short-lived peaks in nearbed suspended sediment concentration (up to ca. 85 mgl -1 ) were recorded. Surface values of suspended sediment concentration range from 1.5 mgl -1 to 17.5 mgl -1 although occasional increases to a maximum of 3.16 mgl -1 were observed. Higher values of surface suspended sediment concentration may be related to dredge spoil dumping activity, but it is not possible to state this unequivocally. PHC\SSM\1 1

13 APPENDICES 1. Turbidity Sensor Calibration Graphs 2. Tabulated weekly Summary Statistics 3. Time series data for total monitoring period 4. Weekly Time-series data 5. Dredge Dump logs PHC\SSM\1 11

14 1. TURBIDITY SENSOR CALIBRATION GRAPHS The bed frame OBS was calibrated in the field by using five varying concentrations of native suspended sediment (Figure 3) The water samples were then filtered across.45 µm Nucleopore filter membranes to determine the dry mass concentration (units mgl -1 ) of suspended sediment. Figure 3 Bed frame OBS Calibration graph including correlation coefficient (R 2 ) for the offshore disposal site OBS Calibration Graph for the Offshore Disposal Site OBS Output Reading y = x R 2 = Suspended Sediment Concentration (mgl -1 ) The surface buoy turbidity sensor was calibrated by Van Oord using surface water samples, the two calibration graphs are shown in figures 4 and 5. PHC\SSM\1 12

15 Figure 4 Surface monitoring buoy turbidity sensor Calibration graph including correlation coefficient (R 2 ) for the offshore disposal site (FTU v NTU) Figure 5 Surface monitoring buoy turbidity sensor Calibration graph including correlation coefficient (R 2 ) for the offshore disposal site. (NTU v TSS) PHC\SSM\1 13

16 2. TABULATED WEEKLY SUMMARY STATISTICS Table 1 Week 1 Disposal Site Data Summary Week 1 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average Min o to 215 o 1815 Max Table 2 Week 2 Disposal Site Data Summary Week 2 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average Min Max o to 215 o 2444 (one disposal event) Table 3 Week 3 Disposal Site Data Summary Week 3 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average Min o to 225 o 7657 Max PHC\SSM\1 14

17 Table 4 Week 4 Disposal Site Data Summary Week 4 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average Min o to 225 o Max Table 5 Week 5 Disposal Site Data Summary Week 5 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average N/A.3 Min N/A. 5 o to 24 o 118 Max N/A 1.4 Table 6 Week 6 Disposal Site Data Summary Week 6 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average N/A.53 Min N/A.1 Max N/A o to 24 o 219 (one disposal event) PHC\SSM\1 15

18 Table 7 Week 7 Disposal Site Data Summary Week 7 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average N/A.28 Min N/A.1 Max N/A.8 N/A (Disposal 3 o to 215 o operations complete) Table 8 Week 8 Disposal Site Data Summary Week 8 Disposal Site Data Summaries Bed frame SSC (mgl -1 ) Surface Buoy SSC (mgl -1 ) Current Speed (ms -1 ) Dominant Current Direction (Deg True) Total Dredge Disposal Volumes (m 3 ) Average N/A.44 Min N/A.1 Max N/A.86 3 o to 215 o N/A (Disposal operations complete) PHC\SSM\1 16

19 3. TIME-SERIES DATA FOR TOTAL MONITORING PERIOD PHC\SSM\1 17

20 2/3/6 13/3/ Surface buoy (mgl -1 ) /3/6 13/3/6 2/3/6 13/3/6 PHC\SSC\ Weeks 1-8 Dredge Dump Volumes at Dump Site 13/2/6 2/2/6 27/2/6 6/3/6 Weeks 1-8 Suspended Sediment Concentrations at Offshore Disposal Site 13/2/6 2/2/6 27/2/6 6/3/6 6/2/6 6/2/6 3/1/6 3/1/6 23/1/ Bedframe SSC Surface Buoy SSC Weeks 1-8 Current Speed at Offshore Disposal Site 13/2/6 2/2/6 27/2/6 6/3/6 6/2/6 3/1/6 23/1/ /1/6 Current Speed (ms -1 ) Bed Frame (mgl -1 ) Dump Volume (m 3 )

21 2/3/6 13/3/ Water Depth at Disposal Site (m) /3/6 19 6/3/6 6/3/6 PHC\SSC\ Weeks 1-8 Current Direction ( T) at Offshore Disposal Site 13/2/6 2/2/6 27/2/6 RoRo Tide Height & Water Depth at Dredge Disposal Site 13/2/6 2/2/6 27/2/6 6/2/6 6/2/6 3/1/6 3/1/6 23/1/ RoRo Tide Water Depth at Disposal Site Date /1/6 Tide Height (m CD) Current Direction ( T)

22 4. WEEKLY TIME-SERIES DATA PHC\SSM\1 2

23 35 Week 1 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /1/6 : 23/1/6 12: 24/1/6 : 24/1/6 12: 25/1/6 : 25/1/6 12: 26/1/6 : 26/1/6 12: 27/1/6 : 27/1/6 12: 28/1/6 : 28/1/6 12: 29/1/6 : 29/1/6 12: 3/1/6 : Week 1 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 23/1/6 : 23/1/6 12: 24/1/6 : 24/1/6 12: 25/1/6 : 25/1/6 12: 26/1/6 : 26/1/6 12: 27/1/6 : 27/1/6 12: 28/1/6 : 28/1/6 12: 29/1/6 : 29/1/6 12: 3/1/6 : 1.2 Week 1 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /1/6 : 23/1/6 12: 24/1/6 : 24/1/6 12: 25/1/6 : 25/1/6 12: 26/1/6 : 26/1/6 12: 27/1/6 : 27/1/6 12: 28/1/6 : 28/1/6 12: 29/1/6 : 29/1/6 12: 3/1/6 : 36 Week 1 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /1/6 : 23/1/6 12: 24/1/6 : 24/1/6 12: 25/1/6 : 25/1/6 12: 26/1/6 : 26/1/6 12: 27/1/6 : 27/1/6 12: 28/1/6 : 28/1/6 12: 29/1/6 : 29/1/6 12: 3/1/6 : Week 1 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) /1/6 : 23/1/6 12: 24/1/6 : 24/1/6 12: 25/1/6 : 25/1/6 12: 26/1/6 : 26/1/6 12: 27/1/6 : 27/1/6 12: 28/1/6 : 28/1/6 12: 29/1/6 : 29/1/6 12: 3/1/6 : PCH/SSM/1 21

24 35 Week 2 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /1/6 : 3/1/6 12: 31/1/6 : 31/1/6 12: 1/2/6 : 1/2/6 12: 2/2/6 : 2/2/6 12: 3/2/6 : 3/2/6 12: 4/2/6 : 4/2/6 12: 5/2/6 : 5/2/6 12: 6/2/6 : Week 2 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 3/1/6 : 3/1/6 12: 31/1/6 : 31/1/6 12: 1/2/6 : 1/2/6 12: 2/2/6 : 2/2/6 12: 3/2/6 : 3/2/6 12: 4/2/6 : 4/2/6 12: 5/2/6 : 5/2/6 12: 6/2/6 : 1.2 Week 2 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /1/6 : 3/1/6 12: 31/1/6 : 31/1/6 12: 1/2/6 : 1/2/6 12: 2/2/6 : 2/2/6 12: 3/2/6 : 3/2/6 12: 4/2/6 : 4/2/6 12: 5/2/6 : 5/2/6 12: 6/2/6 : 36 Week 2 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /1/6 : 3/1/6 12: 31/1/6 : 31/1/6 12: 1/2/6 : 1/2/6 12: 2/2/6 : 2/2/6 12: 3/2/6 : 3/2/6 12: 4/2/6 : 4/2/6 12: 5/2/6 : 5/2/6 12: 6/2/6 : Week 2 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) /1/6 : 3/1/6 12: 31/1/6 : 31/1/6 12: 1/2/6 : 1/2/6 12: 2/2/6 : 2/2/6 12: 3/2/6 : 3/2/6 12: 4/2/6 : 4/2/6 12: 5/2/6 : 5/2/6 12: 6/2/6 : PCH/SSM/1 22

25 35 Week 3 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /2/6 : 6/2/6 12: 7/2/6 : 7/2/6 12: 8/2/6 : 8/2/6 12: 9/2/6 : 9/2/6 12: 1/2/6 : 1/2/6 12: 11/2/6 : 11/2/6 12: 12/2/6 : 12/2/6 12: 13/2/6 : Week 3 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 6/2/6 : 6/2/6 12: 7/2/6 : 7/2/6 12: 8/2/6 : 8/2/6 12: 9/2/6 : 9/2/6 12: 1/2/6 : 1/2/6 12: 11/2/6 : 11/2/6 12: 12/2/6 : 12/2/6 12: 13/2/6 : 1.2 Week 3 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /2/6 : 6/2/6 12: 7/2/6 : 7/2/6 12: 8/2/6 : 8/2/6 12: 9/2/6 : 9/2/6 12: 1/2/6 : 1/2/6 12: 11/2/6 : 11/2/6 12: 12/2/6 : 12/2/6 12: 13/2/6 : 36 Week 3 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /2/6 : 6/2/6 12: 7/2/6 : 7/2/6 12: 8/2/6 : 8/2/6 12: 9/2/6 : 9/2/6 12: 1/2/6 : 1/2/6 12: 11/2/6 : 11/2/6 12: 12/2/6 : 12/2/6 12: 13/2/6 : Week 3 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) 6/2/6 : 6/2/6 12: 7/2/6 : 7/2/6 12: 8/2/6 : 8/2/6 12: 9/2/6 : 9/2/6 12: 1/2/6 : 1/2/6 12: 11/2/6 : 11/2/6 12: 12/2/6 : 12/2/6 12: 13/2/6 : PCH/SSM/1 23

26 35 Week 4 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /2/6 : 13/2/6 12: 14/2/6 : 14/2/6 12: 15/2/6 : 15/2/6 12: 16/2/6 : 16/2/6 12: 17/2/6 : 17/2/6 12: 18/2/6 : 18/2/6 12: 19/2/6 : 19/2/6 12: 2/2/6 : Week 4 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 13/2/6 : 13/2/6 12: 14/2/6 : 14/2/6 12: 15/2/6 : 15/2/6 12: 16/2/6 : 16/2/6 12: 17/2/6 : 17/2/6 12: 18/2/6 : 18/2/6 12: 19/2/6 : 19/2/6 12: 2/2/6 : 1.2 Week 4 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /2/6 : 13/2/6 12: 14/2/6 : 14/2/6 12: 15/2/6 : 15/2/6 12: 16/2/6 : 16/2/6 12: 17/2/6 : 17/2/6 12: 18/2/6 : 18/2/6 12: 19/2/6 : 19/2/6 12: 2/2/6 : 36 Week 4 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /2/6 : 13/2/6 12: 14/2/6 : 14/2/6 12: 15/2/6 : 15/2/6 12: 16/2/6 : 16/2/6 12: 17/2/6 : 17/2/6 12: 18/2/6 : 18/2/6 12: 19/2/6 : 19/2/6 12: 2/2/6 : Week 4 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) /2/6 : 13/2/6 12: 14/2/6 : 14/2/6 12: 15/2/6 : 15/2/6 12: 16/2/6 : 16/2/6 12: 17/2/6 : 17/2/6 12: 18/2/6 : 18/2/6 12: 19/2/6 : 19/2/6 12: 2/2/6 : PCH/SSM/1 24

27 35 Week 5 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /2/6 : 2/2/6 12: 21/2/6 : 21/2/6 12: 22/2/6 : 22/2/6 12: 23/2/6 : 23/2/6 12: 24/2/6 : 24/2/6 12: 25/2/6 : 25/2/6 12: 26/2/6 : 26/2/6 12: 27/2/6 : Week 5 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 2/2/6 : 2/2/6 12: 21/2/6 : 21/2/6 12: 22/2/6 : 22/2/6 12: 23/2/6 : 23/2/6 12: 24/2/6 : 24/2/6 12: 25/2/6 : 25/2/6 12: 26/2/6 : 26/2/6 12: 27/2/6 : 1.2 Week 5 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /2/6 : 2/2/6 12: 21/2/6 : 21/2/6 12: 22/2/6 : 22/2/6 12: 23/2/6 : 23/2/6 12: 24/2/6 : 24/2/6 12: 25/2/6 : 25/2/6 12: 26/2/6 : 26/2/6 12: 27/2/6 : 36 Week 5 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /2/6 : 2/2/6 12: 21/2/6 : 21/2/6 12: 22/2/6 : 22/2/6 12: 23/2/6 : 23/2/6 12: 24/2/6 : 24/2/6 12: 25/2/6 : 25/2/6 12: 26/2/6 : 26/2/6 12: 27/2/6 : Week 5 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) /2/6 : 2/2/6 12: 21/2/6 : 21/2/6 12: 22/2/6 : 22/2/6 12: 23/2/6 : 23/2/6 12: 24/2/6 : 24/2/6 12: 25/2/6 : 25/2/6 12: 26/2/6 : 26/2/6 12: 27/2/6 : PCH/SSM/1 25

28 35 Week 6 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /2/6 : 27/2/6 12: 28/2/6 : 28/2/6 12: 1/3/6 : 1/3/6 12: 2/3/6 : 2/3/6 12: 3/3/6 : 3/3/6 12: 4/3/6 : 4/3/6 12: 5/3/6 : 5/3/6 12: 6/3/6 : Week 6 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 27/2/6 : 27/2/6 12: 28/2/6 : 28/2/6 12: 1/3/6 : 1/3/6 12: 2/3/6 : 2/3/6 12: 3/3/6 : 3/3/6 12: 4/3/6 : 4/3/6 12: 5/3/6 : 5/3/6 12: 6/3/6 : 1.2 Week 6 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /2/6 : 27/2/6 12: 28/2/6 : 28/2/6 12: 1/3/6 : 1/3/6 12: 2/3/6 : 2/3/6 12: 3/3/6 : 3/3/6 12: 4/3/6 : 4/3/6 12: 5/3/6 : 5/3/6 12: 6/3/6 : 36 Week 6 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /2/6 : 27/2/6 12: 28/2/6 : 28/2/6 12: 1/3/6 : 1/3/6 12: 2/3/6 : 2/3/6 12: 3/3/6 : 3/3/6 12: 4/3/6 : 4/3/6 12: 5/3/6 : 5/3/6 12: 6/3/6 : Week 6 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) /2/6 : 27/2/6 12: 28/2/6 : 28/2/6 12: 1/3/6 : 1/3/6 12: 2/3/6 : 2/3/6 12: 3/3/6 : 3/3/6 12: 4/3/6 : 4/3/6 12: 5/3/6 : 5/3/6 12: 6/3/6 : PCH/SSM/1 26

29 35 Week 7 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /3/6 : 6/3/6 12: 7/3/6 : 7/3/6 12: 8/3/6 : 8/3/6 12: 9/3/6 : 9/3/6 12: 1/3/6 : 1/3/6 12: 11/3/6 : 11/3/6 12: 12/3/6 : 12/3/6 12: 13/3/6 : Week 7 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 6/3/6 : 6/3/6 12: 7/3/6 : 7/3/6 12: 8/3/6 : 8/3/6 12: 9/3/6 : 9/3/6 12: 1/3/6 : 1/3/6 12: 11/3/6 : 11/3/6 12: 12/3/6 : 12/3/6 12: 13/3/6 : 1.2 Week 7 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /3/6 : 6/3/6 12: 7/3/6 : 7/3/6 12: 8/3/6 : 8/3/6 12: 9/3/6 : 9/3/6 12: 1/3/6 : 1/3/6 12: 11/3/6 : 11/3/6 12: 12/3/6 : 12/3/6 12: 13/3/6 : 36 Week 7 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /3/6 : 6/3/6 12: 7/3/6 : 7/3/6 12: 8/3/6 : 8/3/6 12: 9/3/6 : 9/3/6 12: 1/3/6 : 1/3/6 12: 11/3/6 : 11/3/6 12: 12/3/6 : 12/3/6 12: 13/3/6 : Week 7 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) /3/6 : 6/3/6 12: 7/3/6 : 7/3/6 12: 8/3/6 : 8/3/6 12: 9/3/6 : 9/3/6 12: 1/3/6 : 1/3/6 12: 11/3/6 : 11/3/6 12: 12/3/6 : 12/3/6 12: 13/3/6 : PCH/SSM/1 27

30 35 Week 8 Dredge Dump Volumes at Dump Site Dump Volume (m 3 ) /3/6 : 13/3/6 12: 14/3/6 : 14/3/6 12: 15/3/6 : 15/3/6 12: 16/3/6 : 16/3/6 12: 17/3/6 : 17/3/6 12: 18/3/6 : 18/3/6 12: 19/3/6 : 19/3/6 12: 2/3/6 : Week 8 Suspended Sediment Concentrations at Offshore Disposal Site 9 Bedframe SSC Surface Buoy SSC Bed Frame (mgl -1 ) Surface buoy (mgl -1 ) 13/3/6 : 13/3/6 12: 14/3/6 : 14/3/6 12: 15/3/6 : 15/3/6 12: 16/3/6 : 16/3/6 12: 17/3/6 : 17/3/6 12: 18/3/6 : 18/3/6 12: 19/3/6 : 19/3/6 12: 2/3/6 : 1.2 Week 8 Current Speed at Offshore Disposal Site Current Speed (ms -1 ) /3/6 : 13/3/6 12: 14/3/6 : 14/3/6 12: 15/3/6 : 15/3/6 12: 16/3/6 : 16/3/6 12: 17/3/6 : 17/3/6 12: 18/3/6 : 18/3/6 12: 19/3/6 : 19/3/6 12: 2/3/6 : 36 Week 8 Current Direction ( T) at Offshore Disposal Site Current Direction ( T) /3/6 : 13/3/6 12: 14/3/6 : 14/3/6 12: 15/3/6 : 15/3/6 12: 16/3/6 : 16/3/6 12: 17/3/6 : 17/3/6 12: 18/3/6 : 18/3/6 12: 19/3/6 : 19/3/6 12: 2/3/6 : Week 8 RoRo Tide Height & Water Depth at Dredge Disposal Site RoRo Tide Water Depth at Disposal Site Tide Height (m CD) Water Depth (m) /3/6 : 13/3/6 12: 14/3/6 : 14/3/6 12: 15/3/6 : 15/3/6 12: 16/3/6 : 16/3/6 12: 17/3/6 : 17/3/6 12: 18/3/6 : 18/3/6 12: 19/3/6 : 19/3/6 12: 2/3/6 : PCH/SSM/1 28

31 5. DREDGE DISPOSAL LOGS The dredge disposal logs, recorded by the dredge contractor (van Oord) are shown on the following page. Table 9 provides the code for the dredge areas. Table 9 Dredge area code and name/location Code A B1 B2 C D1 D2 D3 E F Dredge Area Name Turning Basin Middle Channel Middle Channel Swash Channel Swash Channel Swash Channel Swash Channel Swash Channel Little Channel PHC\SSM\1 29

32 Disposal Date & Time Trip No. Vessel Dredge Area Quantity (Mt) Volume Disposal Area (m 3 ) Easting Northing Direction Type of Material Wind Speed (ms -1 ) Wind Direction (Deg True) RoRo Tide Height (m) 25/1/6 1:4 27 WATERWAY B Silt & Clay /1/6 8:5 216 WATERWAY A Silt & Clay /1/6 9:5 279 HAM311 D Sand /1/6 12:2 278 HAM311 A Silt & Clay /1/6 12:3 215 WATERWAY B Silt & Clay /1/6 23:2 225 WATERWAY D Sand /2/6 12:5 237 WATERWAY A Silt.Clay /2/6 1: 317 HAM311 E Sand/shells /2/6 17: WATERWAY B1 + B Silt/sand /2/6 16: 327 HAM311 B Silt.Clay /2/6 14: HAM311 F + B Silt / Clay /2/6 : HAM311 F 1, Silt/Clay/Stones /2/6 2:5 35 HAM311 B Silt / Clay /2/6 4: HAM311 C 2, /2/6 8: HAM311 C 2, Clay / Sand / Rubbish Silt / Clay / Sand / Rubbish /2/6 12:5 353 HAM311 F 1, Silt/sand /2/6 21: HAM311 B1 2, Clay /2/6 :1 359 HAM311 A 2, Sand /2/6 9: HAM311 A/B1/B2 2, Sandy Clay /2/6 16:3 357 HAM311 F 2, Silt/Clay/Stones /2/6 2:3 358 HAM311 A 2, Clay /2/6 2:3 376 HAM312 A 2, Clay N/A /2/6 5:3 373 HAM311 A 2, Clay N/A /2/6 9:4 374 HAM311 B1 1, Clay N/A /2/6 17:4 375 HAM311 F Clay N/A /2/6 2:3 377 HAM311 A 2, Clay N/A /2/6 7:2 378 HAM311 F 1, Clay N/A /2/6 23:58 44 Ham 311 B N/A N/A N/A N/A N/A N/A N/A Total PHC\SSC\1 3