Rockabill Cable Route Corridor Marine Archaeological Assessment
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Rockabill Cable Route Corridor Marine Archaeological Assessment Client: McMahon Design and Management Author: Mark Kelly Checked By: Finn Delaney Job No. G18006 Date: 14/02/2018 Geo-Mara Ltd. Cois Cuain, Ballynamanagh, Clarinbridge, Co. Galway, Ireland Tel: + 353 91 485790, Email:[email protected], Web: www.Geo-Mara.com Marine Archaeological Assessment Non-Technical Summary: McMahon Design and Management Ltd. Have commissioned Geomara Ltd. to undertake a maritime archaeological assessment in connection with the DeepSea Fibre Networks proposed sub-sea fibre optic cable extending from Portrane in North County Dublin and making landfall at Cleveleys in Lancashire in the UK. This report addresses the section within the Irish jurisdiction. The assessment comprises an introduction to the study area; and the identification of cultural heritage sites, features and deposits located along the proposed cable route corridor. In order to provide a comprehensive assessment, an extensive desk based study of the route corridor was undertaken. Potential impacts of the proposed scheme on the receiving environment are addressed and mitigation measures to ameliorate these impacts are presented. The assessment concluded that there are no known potential cultural heritage assets directly affected by the landfall in Portrane but a number of wrecks sites are located in close proximity to the cable corridor. Two sites in particular (the Sharlega W10033 and the Nelie Esplin W00786) are highlighted as having possible direct impacts. The route corridor as assessed was changed as a result of these findings and the cable corridor has been diverted around the location of the Sharlega (W 10033). Three archaeological monuments located in close proximity to where the cable route makes landfall in Portrane are St Catherine’s Church (DU-008-031001), located c. 200m directly west of the where the cable makes landfall, adjacent to the church and graveyard c. 430m northwest of landfall a Tower house (DU-008-030) known as Stella’s Castle can be found and in the townland of Quay almost 400m east of the cable making landfall the human burnt remains (DU-008-032) in a beach deposit were exposed in the 1940’s suggesting a possible funeral pyre. Given the close proximity to these known sites and wrecks, the likelihood of additional unknown archaeological features or wrecks associated with the surrounding historical landscape needs to be taken into consideration before and during the proposed project. Consequently, given the results of the impact assessment the mitigation strategies outlined here detail the measures to be adopted in order to ameliorate any unforeseen direct, indirect and secondary impacts that the proposed cable may have on features of maritime cultural heritage interest. If these measures are employed it is envisaged that the proposed cable installation will have no impact on features of maritime cultural heritage interest. The following mitigation recommendations are presented in connection with the proposed cable: 1. It is recommended that all sites of cultural heritage interested included in this report are avoided. 2. The cable installation from the end of the HDD out to the low water line should be subject to archaeological monitoring. 3. A detailed marine survey using remote sensing geophysical techniques, involving Multibeam Echosounder, Sidescan Sonar, Sub Bottom Profiler and Marine Magnetometer should be carried out prior to commencement of main-lay operations. 4. Archaeological analysis of the geophysical and bathymetric pre- installation surveys should be undertaken to both confirm the locations of the wreck sites within the survey corridor and also to identify any potential unrecorded seabed and sub seabed maritime archaeological features. Where the location of any wreck sites on the cable route is established the cable will be re-routed to avoid them. Geo-Mara Ltd. Cois Cuain, Ballynamanagh, Clarinbridge, Co. Galway, Ireland Tel: + 353 91 485790, Email:[email protected], Web: www.Geo-Mara.com Marine Archaeological Assessment 5. Archaeological monitoring of the pre-lay grapnel run should be undertaken in order to identify any previously unrecorded archaeological features finds or deposits. 6. It is recommended that procedures should be put in place to ensure that any previously unrecorded cultural heritage assets encountered during the project should be assessed by a suitably qualified archaeologist and avoided by the cable laying operations. 7. Should the proposed cable route be subject to further revision, details of these revisions should be forwarded to the project archaeologist for assessment 8. On completion of the cable installation a report will be produced summarising all archaeological aspects of the project and submitted to DAHG and the National Museum of Ireland Geo-Mara Ltd. Cois Cuain, Ballynamanagh, Clarinbridge, Co. Galway, Ireland Tel: + 353 91 485790, Email:[email protected], Web: www.Geo-Mara.com Marine Archaeological Assessment Table of Contents 1. INTRODUCTION ...................................................................................................... 5 1.1 Introduction .......................................................................................................................................... 5 1.2 Site Location: ......................................................................................................................................... 5 1.3 Legislative Framework and Guidance ................................................................................................... 7 2. ASSESSMENT METHODOLOGY ................................................................................ 8 2.1 Desk based assessment ......................................................................................................................... 8 2.2 Impact Assessment ............................................................................................................................... 9 2.3 Mitigation measures ............................................................................................................................. 9 3. EXISTING ENVIRONMENT ..................................................................................... 10 3.1 Introduction ........................................................................................................................................ 10 3.2 Planning Context in Relation to Archaeology and Cultural Heritage .................................................. 10 3.3 Historical Landscape Character Areas ................................................................................................. 19 3.4 Geological Baseline ............................................................................................................................. 21 3.5 Bathymetry and seabed typology ....................................................................................................... 21 3.6 Portrane and Donabate ....................................................................................................................... 22 4. CABLE ROUTE CORRIDOR ...................................................................................... 25 4.1 Sites of cultural heritage interest along the cable corridor. ............................................................... 25 4.4 Unrecorded sites ................................................................................................................................. 34 5. PROPOSED CABLE DEVELOPMENT DETAILS ........................................................... 35 5.1 Pre Installation Survey ........................................................................................................................ 35 5.2 The landfall at Portrane (HDD) ............................................................................................................ 35 5.3 Cable Installation on Beach ................................................................................................................. 36 5.4 Offshore Cable Installation .................................................................................................................. 36 6. IMPACT ASSESSMENT ........................................................................................... 37 6.1 Impacts on maritime cultural heritage................................................................................................ 37 6.2 Direct Impacts ..................................................................................................................................... 38 6.3 Indirect Impacts .................................................................................................................................. 39 6.4 Secondary Impact ................................................................................................................................ 39 6.5 Cumulative impacts ............................................................................................................................. 39 7. MITIGATION MEASURES ....................................................................................... 40 7.2 Proposed Route Position List .............................................................................................................. 41 APPENDIX 1 SHIPWRECK INVENTORY ......................................................................... 43 APPENDIX 2. TOPOGRAPHICAL FILES ..........................................................................