Appendix D DHI Marine Survey Report 2010 For inspection purposes only. Consent of copyright owner required for any other use. EPA Export 10-12-2012:23:36:56 For inspection purposes only. Consent of copyright owner required for any other use. EPA Export 10-12-2012:23:36:56 Ringsend Waste Water Treatment Plant Long Sea Outfall Dublin Bay Marine Survey Report For inspection purposes only. Consent of copyright owner required for any other use. CDM Ireland Final Report July 2010 EPA Export 10-12-2012:23:36:56 Ringsend Waste Water Treatment Plant Agern Allé 5 DK-2970 Hørsholm, Denmark Long Sea Outfall Tel: +45 4516 9200 Dublin Bay Fax: +45 4516 9292 e-mail: [email protected] Marine Survey Report Web: www.dhigroup.com July 2010 Client Client’s representative CDM Ireland Mr. Alan Hooper Project Project No Ringsend Waste Water Treatment Plant 11807675 Long Sea Outfall - Dublin Bay Authors Date Kim Roerbaek 9 July 2010 Approved by For inspection purposes only. Consent of copyright owner required for any other use. H. Jacob Vested Head of Projects, CED 2 Final report (2) KIR HJV HJV 09/07/10 1 Final Report(1) KIR HJV HJV 18/06/10 0 Draft Final Report KIR HJV HJV 26/01/10 Revision Description By Checked Approved Date Key words Classification ADCP current mapping Open ADCP fixed stations Internal Proprietary Distribution No of copies CDM Ireland: Mr. Alan Hooper PDF DHI: HJV, HRJ, KIR, JAO PDF EPA Export 10-12-2012:23:36:56 CONTENTS 1 INTRODUCTION ........................................................................................................... 2 2 MARINE SURVEY WORK ............................................................................................ 3 2.1 Survey Area .................................................................................................................. 3 2.2 Survey Boat .................................................................................................................. 4 2.3 Survey Activities ............................................................................................................ 5 2.4 Mapping of Spatial Current Circulation .......................................................................... 6 2.5 Fixed Station Measurements ....................................................................................... 10 2.6 Float Trackings ........................................................................................................... 13 APPENDICES A Current Vector Plots B Data from Fixed Measuring Stations C Float Trackings D Examples of Model Verification For inspection purposes only. Consent of copyright owner required for any other use. 11806543.kir.be-ybr.09July2010 i DHI EPA Export 10-12-2012:23:36:56 1 INTRODUCTION With the purpose of providing data for calibration and verification of a numerical model, DHI has conducted two current measurement campaigns in Dublin Bay, Ireland. The first campaign was performed from 6 April to 11 April 2010 and the second between 11 May to 14 May 2010. The first campaign comprised vessel-based mapping of spatial current distribution in Dublin Bay, deployment of two bottom-mounted Acoustic Doppler Current Profilers (ADCPs), a temperature/conductivity string as well as float trackings. The second campaign also comprised mapping of spatial current distribution as well as float trackings. Additionally, the deployed instruments were all recovered. The hydrographical data will be used to develop and calibrate a three-dimensional hydrodynamic and transport numerical model which forms part of the subsequent thermal impact and re-circulation study. For inspection purposes only. Consent of copyright owner required for any other use. 11806543.kir.be.06.2010 2 DHI EPA Export 10-12-2012:23:36:56 2 MARINE SURVEY WORK 2.1 Survey Area A number of predefined transects were established in the outer part of Dublin Bay. The transects running E-W crossed the shallow Burford Bank, whereas two N-S running transects were inside Burford Bank and one was outside. For inspection purposes only. Consent of copyright owner required for any other use. Figure 2.1 Figure showing the predefined transect grid established for the 2010 current mapping campaign in Dublin Bay. The deployment locations for the two ADCPs and the TC string are also shown 11806543.kir.be.06.2010 3 DHI EPA Export 10-12-2012:23:36:56 2.2 Survey Boat A local fishing boat was contracted for the work. The boat was mobilised with hydro- graphic equipment and an ADCP was mounted in a fixation over the side. Figure 2.2 The survey boat and the fixation holding the ADCP For inspection purposes only. The boat was providedConsent for of copyright an electric owner required winch for any which other use. proved very useful during retrieval of the fixed measuring stations in the bay, see Figure 2.2. The boat was an excellent platform for the work and the boat’s captain was skilled and competent. 11806543.kir.be.06.2010 4 DHI EPA Export 10-12-2012:23:36:56 2.3 Survey Activities Table 2.1 below lists the activities performed in the course of the project. Only main activities are included. Table 2.1 Table of main activities Date Activity First measuring campaign Arrival in Dublin of Mr. Kim Roerbaek, DHI 6 April 2010 Prepare equipment for deployment Deploy ADCP and TC string in station 1 inside Burford Bank Mobilise boat for ADCP transect work 7 April 2010 Collect ADCP data in predefined lines 8 April 2010 Continue ADCP data collection in predefined lines in the bay 9 April 2010 Continue ADCP data collection in predefined lines in the bay 10 April 2010 Continue ADCP data collection in predefined lines in the bay Float tracking in areas of proposed outfall locations 11 April 2010 Deploy ADCP in station 2 outside Burford Bank End of first measuring campaign Second measuring campaign Arrival in Dublin of Mr Kim Roerbaek, DHI 10 May 2010 Weather does not allow recovery of fixed stations in the bay Mobilise boat for ADCP transect work Float trackings in areas of proposed outfall locations Recover For ADCP inspection and purposes TC only. string in station 1 11 May 2010 Consent of copyright owner required for any other use. Recover ADCP in station 2 Process data from all three stations 12 May 2010 Collect ADCP data in predefined lines in the bay Continue ADCP data collection in predefined lines in the bay 13 May 2010 Stop at 13:00 hrs due to bad weather Continue ADCP data collection in predefined lines in the bay 14 May 2010 End of second measuring campaign 11806543.kir.be.06.2010 5 DHI EPA Export 10-12-2012:23:36:56 2.4 Mapping of Spatial Current Circulation Mapping of spatial currents in the bay was made with a vessel-mounted RDI 600 kHz Workhorse ADCP. The ADCP uses the Doppler principle to measure the water velocity relative to the boat. In addition, the ADCP also measures its own speed and direction across the bottom using the same technique as it uses to measure the velocity of the water. By subtracting the boat velocity from the apparent (relative) water velocity, the true velocity of the water with respect to the bottom is determined. An ADCP divides the water column into a number of discrete segments stacked in the vertical. These segments are called depth cells. The ADCP determines the velocity and direction of each depth cell. If we plot the velocity as a function of depth, we get a velocity profile from near the surface to near the bottom, see Figure 2.3. For inspection purposes only. Consent of copyright owner required for any other use. Figure 2.3 Boat-mounted ADCP measuring principle Due to inherent limitations in the Doppler principle, the ADCP cannot measure the top 1.2-2m (distance depends on configuration) of the water column and an area close to the seabed equal to 6% of the total water depth. The ADCP was configured to collect a velocity profile approximately every 10 seconds while underway. The boat speed was kept around 5 knots thereby recording a current velocity profile every 25m. The ADCP was mounted on the survey boat’s port using a simple wood assembly, see Figure 2.2. Spatial current information was collected in predefined lines, see Figure 2.1. The lines were established in order to provide the best possible information on the current circula- tion pattern that is instrumental in the calibration of the hydrodynamic model. 11806543.kir.be.06.2010 6 DHI EPA Export 10-12-2012:23:36:56 A Hemisphere V110 GPS compass provided heading and positioning data and HYPACK MAX integrated survey software package were used for data collection and navigation. HYPACK MAX is a suite of programmes assisting in collecting and processing data pertinent to surveying works. The programme displays the survey area and creates planned survey lines. Navigation information for assisting the helmsman to keep the boat on the predefined lines is displayed on the PC screen. At the end of each survey day, all transect data were processed and depth-averaged currents were presented in pdf files superimposed on a Google image of Dublin Bay. An example is shown below: For inspection purposes only. Consent of copyright owner required for any other use. Figure 2.4 Example of vector plot of ADCP data collected 13 May 2010 in the period between 11:46 and 12:57 hrs UTC. The vectors represent depth-averaged current velocity and direction. Velocities are in cm/sec. The corresponding tidal stage is shown in the top left corner (the solid red curve represents the tide during the measurement period) 11806543.kir.be.06.2010 7 DHI EPA Export 10-12-2012:23:36:56 It was attempted to temporally distribute the data collection in such a way that various tidal stages were covered. The weather conditions were very favourable during the first measuring campaign, whereas the second campaign was characterised by windy conditions which to a certain degree affected the amount of data that we managed to collect. However, the data quality was not affected and in general, the quality of the transect data from both campaigns was very high. Velocity profiles in each transect were depth-averaged and are presented as vector plots on a total of 16 plots.