Underwater Archaeological Impact Assessment Arklow Bank Wind Park Lease Area and Cable Routes LF100034-MIP-EV-RPT-0001 Underwater Archaeological Impact Assessment Arklow Bank Wind Park Lease Area and Cable Routes LF100034-MIP-EV-RPT-0001 Issued 31/07/2020 Client SSE for Sure Partners Ltd Project Director Niall Brady Report Author Niall Brady Figures Rex Bangerter Beverley Studios, Church Terrace, Bray, Co. Wicklow www.adco-ie.com Contents Abbreviations List of Figures 1 List of Plates 1 Executive Summary 2 1.0 Introduction 5 2.0 Receiving environment 6 3.0 2019 Marine geophysical survey 13 4.0 Impact assessment 22 5.0 Recommendations 22 6.0 Appendix 1: Recorded shipwreck events on Arklow Bank and adjacent waters 26 7.0 Appendix 2: Known shipwreck events on Arklow Bank and adjacent waters 31 8.0 Appendix 3: Catalogue of shipwreck sites and sites of potential wreckage on Arklow Bank and in adjacent waters 35 9.0 Appendix 4: Archaeology Management Plan in the event of the discovery of archaeological material during offshore GI works 94 10.0 References 99 Abbreviations ABWP - Arklow Bank Wind Park ADCO - Archaeological Diving Company Ltd AIA - Archaeological Impact Assessment CR - Cable Route DCHG - Department of Culture, Heritage and the Gaeltacht DPC - Dublin Port Company E - Easting EIS - Environmental Impact Statement GI - Geotechnical Investigations ITM - Irish Transverse Mercator LA - Lease Area LAT - Lowest Astronomical Tide MHW - Mean High Water N - Northing NGR - National Grid Reference NIAH - National Inventory of Architectural Heritage OD - Ordnance Datum SI - Site Investigations SMR - Sites and Monuments Record UAIA - Underwater Archaeological Impact Assessment UTM - Universal Transverse Mercator .......................................................................................................................................... Underwater Archaeological Impact Assessment Arklow Bank Wind Park Lease Area and Cable Routes List of Figures Figure 1: Map showing coastline and inshore seabed area stretching between the harbours at Wicklow and Wexford. Figure 2: Extract from Admiralty Chart map showing location of Arklow Bank with associated ABWP Foreshore Application Boundary superimposed. Figure 3: Distribution of known wreck sites and possible wreck sites from the DCHG Shipwreck Inventory. Figure 4: Distribution of known wreck sites across the northern half of the Arklow Banks, as per the DCHG Shipwreck Inventory, the 2019 Marine Geophysical Survey, and ADCO’s observation of that data. Figure 5: Distribution of known wreck sites across the southern half of the Arklow Banks, as per the DCHG Shipwreck Inventory, the 2019 Marine Geophysical Survey, and ADCO’s observation of that data. List of Plates Plate 1: The wrecking of the Royal Mail steam barque, Armenian, on 25th January 1865, as recorded in the Illustrated London News (Wreck W02658). Plate 2: Typical target recorded as a boulder, Target LA_1937. Survey line LA_W_011d.001. Plate 3: Debris Target LA_0331 showing on the right side of the sonar trace as an erratic assortment of linear elements. Plate 4: Linear target identified as fishing gear. Plate 5: Sonar trace showing the existing export cable from the windfarm that can be recorded in several instances. Plate 6: Example of one of three possible unexploded ordnance features recorded on the sonar traces. Plate 7: Example of one of two mound features recorded on the sonar traces. ADCO 1 Underwater Archaeological Impact Assessment Arklow Bank Wind Park Lease Area and Cable Routes Executive Summary Subject: Arklow Bank Wind Park Location: Arklow Bank UTM 30N: 301648E 5855291N Status: Archaeological seascape Introduction An Underwater Archaeological Impact Assessment (UAIA) was carried out of the Foreshore Licence application area of the consented offshore wind farm development, Arklow Bank Wind Park, located on the Arklow Bank, some 6 to 13km off the Co. Wicklow coast, centred at UTM30N 301648E 5855291N (ITM 738663E 675303N, WGS84 52.810864 Latitude -5.943113 Longitude). The UAIA is based on a desktop review of existing archaeological sources, and a review of marine geophysical survey data sets and report acquired in 2019 to inform a proposed programme of Offshore Geotechnical Investigation (GI) work. Receiving environment The Arklow Bank has been hazardous to shipping, and one hundred and sixty-five (165) historic wrecking events are associated with Arklow Bank and in the waters close to it. This includes one hundred and sixteen (116) recorded wreckings whose specific locations are not known, as well as forty-nine (49) known wreck-site and potential wreck-site locations, which have been identified through previous marine geophysical and related site surveys. Desktop review indicates the presence of no known features on the foreshore at the landfall locations. 2019 Marine geophysical survey A new and comprehensive marine geophysical survey was completed in 2019 by Ultrabeam for Alpha Marine on behalf of SSE that focussed on the Arklow Bank and three cable route options to shore. The 2019 survey comprised multi-beam bathymetry; side-scan sonar; magnetometry and sub-bottom profile surveys, to inform a detailed understanding of the topography and underlying geological formations of the seabed. The data of the 2019 survey was made available and has been reviewed archaeologically. Archaeological review focused on the side-scan sonar and magnetometry data sets and has included the three cable route landfall locations on shore. Twenty-four (24) wreck sites and potential wreck sites were recorded in the 2019 data set, some of which have been identified previously and some of which are newly ADCO 2 Underwater Archaeological Impact Assessment Arklow Bank Wind Park Lease Area and Cable Routes identified. In addition, three (3) possible unexploded ordnance targets were identified, 4 possible fishing gear targets, over twelve hundred (1200) debris targets and more than five thousand (5000) boulder targets. The 2019 marine geophysical survey set is very robust and establishes a new standard for survey on Arklow Bank. Archaeological review of the dataset concurs with the principal observations and identifies seven (7) additional potential wreck sites. There is close correlation between eight (8) historic wreck site locations and eight (8) of the sites recorded in the 2019 data set. The total number of wreck sites and potential wreck sites associated with the Arklow Bank currently stands at seventy-four (74). Wreck sites and potential wreck sites identified in previous surveys were not all observed in the 2019 survey, while the 2019 survey identified new sites in areas surveyed previously. This speaks to the dynamic environment of the Arklow Bank, where shifting sands will routinely expose and alternatively bury sites of archaeological interest. This report accepts the record as reported in the 2019 survey and believes the record to be very robust and comprehensive. It establishes a new standard for survey on Arklow Bank. Impact assessment A programme of Geotechnical Investigations (GI) is proposed for 2020 to 2023 that will obtain baseline data to inform detailed design of turbines, foundations, inter-array and export cables. The techniques proposed include: Boreholes; Cone Penetration Tests; Vibrocores; Grab/gravity Sampling and Trial Pitting. The exact locations of the Site Investigations will be selected to confirm the geophysical interpretation and to sample each change in geological unit, while being mindful of environmental constraints including the presence of archaeological features. The excavation of Trial Pits is restricted to the landfall sites. Recommendations The UAIA recommends the location of the landfall sites are inspected archaeologically by means of intertidal walkover survey. The inspection should take place in advance of GI works at the landfalls, if any open excavation works are intended, so that the GI works can avoid impacts on locations of archaeological interest. The UAIA recommends the locations of the seventy-four (74) wreck sites and potential wreck sites are avoided in the GI works. An exclusion zone is identified for each location where necessary, within which no GIs should take place. The size of the exclusion zones vary according to the recorded extent of the wreck site or potential wreck site and in some instances extends to include areas that may be related to debris fields associated with the wrecking event. The GI works locations will be agreed with SSE and the project archaeologist in advance and will not take place within the exclusion zones. The GI works may therefore take place without a requirement for an archaeological presence aboard the GI platform/s. A protocol, or Archaeological Management Plan (AMP), is nevertheless required to inform the GI works, to facilitate the discovery and reporting of ADCO 3 Underwater Archaeological Impact Assessment Arklow Bank Wind Park Lease Area and Cable Routes archaeological material during GI works should this occur. The AMP is included in this report in Appendix 4. The appropriate records of the GIs will be reviewed archaeologically following completion of the GI works and will be the subject of an annual archaeological report on that year’s GI campaign/s. The works will contribute additional information, which will inform the archaeological understanding of what is a known seascape that retains high archaeological potential. In the event that GIs are unable to avoid impacts within an exclusion zone, the works can only proceed with the consent