Marine Archaeo-Geophysical Survey of of Amets

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MARINE ARCHAEO‐GEOPHYSICAL SURVEY

OF OF AMETS OFFSHORE BERTHS AND CABLE ROUTE

ANNAGH HEAD,

BELMULLET,

CO. MAYO.

Moore Marine

Job Number: M12MY02

Author: Eoghan Kieran

Licence No. 10R012

Date: August 2012

TABLE OF CONTENTS 1 SCOPE OF WORKS...... 1 1.1 Introduction...... 1 2 CHARACTERISTICS OF THE PROJECT...... 1 2.1 Project Description ...... 1 2.2 Wave Energy Test Site Location...... 2 2.3 Project Components ...... 3 2.4 Site Layout/Location details ...... 5 3 DESCRIPTION OF THE EXISTING ENVIRONMENT...... 5 3.1 Solid Geology ...... 5 3.2 Soil Type...... 5 3.3 Landscape ...... 5 4 ARCHAEO-GEOPHYSICAL SURVEY ...... 5 4.1 Side Scan Sonar Survey ...... 7 4.1.1 System...... 7 4.1.2 Frequency ...... 8 4.1.3 Range ...... 8 4.1.4 Slant Range Correction ...... 8 4.1.5 Survey Pattern...... 8 4.1.6 Navigation...... 8 4.1.7 Data Acquisition...... 9 4.1.8 File Format...... 9 4.1.9 Datum...... 9 4.1.10 Geo-referencing ...... 9 4.2 Marine Magnetometer Survey ...... 9 4.2.1 System...... 9 4.2.2 Cycling Rate ...... 10 4.2.3 Survey Pattern...... 10 4.2.4 Navigation...... 10 4.2.5 Data Acquisition...... 10 4.2.6 File Format...... 11 4.2.7 Datum...... 11 4.2.8 Geo-referencing ...... 11 4.3 Multibeam data...... 11 5 CHARACTERISTICS OF THE PROPOSED DEVELOPMENT ...... 11 5.1 Offshore Berth Locations;...... 12 5.2 Submarine electricity cables ...... 12 5.3 Cable lay vessel...... 13 5.4 Cable burial ...... 14 5.5 Cable route...... 14 5.6 Submarine cable landfall ...... 15 5.7 Cable transition joint bay ...... 15 5.8 Substation ...... 15 6 ARCHAEOLOGICAL ASSESSMENT OF GEOPHYSICAL DATA ...... 16 6.1 Side Scan Sonar ...... 16 6.1.1 100m water depth offshore test area ...... 16 6.1.2 Cable route from 100m water depth offshore test area to 50m water depth offshore test area...... 19 6.1.3 50m water depth offshore test area...... 20 6.1.4 Cable route from 50m water depth offshore test area to extent of offshore survey 22 6.2 Magnetometer...... 22 6.3 Multibeam bathymetry ...... 23 7 DISCUSSION & RECOMMENDATIONS ...... 25 7.1 Discussion ...... 25 7.1.1 The Development Area ...... 25 7.2 Assessment of Potential Impacts...... 26 7.3 Recommendations ...... 26 8 APPENDIX 1. SIDE SCAN SONAR CONTACTS ...... 27 9 APPENDIX 2. BIBLIOGRAPHY ...... 32

TABLE OF TABLES Table 1. Location details...... 5

TABLE OF FIGURES Figure 1. Extract from Admiralty Chart 2420 showing berth locations in red and cable route in black (Berth C has been removed)...... 2 Figure 2. Proposed landing site with cable route in blue ...... 3 Figure 3. 2010 Survey Lines ...... 6 Figure 4. 2012 Survey lines...... 7 Figure 5. 2010 & 2012 Side Scan Sonar Mosaic of Survey Area ...... 16 Figure 6. Results of 2010 Magnetometer Survey ...... 23 Figure 7. Results of 2012 Magnetometer Survey ...... 23 Figure 8. Multibeam data being reviewed in IVS Fledermaus...... 24 Figure 9. Multibeam data of the AMETS site...... 25

TABLE OF PLATES Plate 1. Klein 3900 Side Scan Sonar...... 8 Plate 2. Marine Magnetics Sea Spy Magnetometer ...... 10 Plate 3. Small anchor associated with ADCP ...... 17 Plate 4. Met Buoy anchor and cable on sandy seafloor and in the water column...... 18 Plate 5. Small rock outcrop on eastern side of Test Area A...... 18 Plate 6. Gravel patch in western side of Test Area A...... 19 Plate 7. Rocky and sandy seafloor along Test Area A cable route...... 20 Plate 8. Image of mooring chain at 50m box...... 21 Plate 9. Rocky and sandy seafloor in Test Area B ...... 21

M12MY02 AMETS Geophysical Survey August 2012

1 SCOPE OF WORKS

1.1 Introduction

Moore Marine Services Ltd. was commissioned by the Sustainable Energy Authority of Ireland (SEAI), to carry out a archaeo‐geophysical cultural heritage assessment of locations for a proposed wave energy test site and associated facilities at Annagh Head, Belmullet, Co. Mayo. Resulting from the preliminary survey a full archaeo‐geophysical cultural heritage assessment of the proposed offshore test areas and cable route corridor was undertaken. As part of the EIS study assessments were undertaken at the proposed test area locations shown in Figure 1 below. The shape of the areas proposed for the test site was altered following discussions with the local Fishing community (particularly the Erris Inshore Fishermens Association, EIFA) to accommodate their activities. The reshaped areas incorporated the original areas surveyed but extended beyond the boundaries necessitating a re‐evaluation of available Multibeam survey data obtained during the original surveys by the Celtic Voyager and supplementing this with additional side scan sonar and marine magnetometer surveys. The surveys were undertaken from 28th September to 3rd October 2010 and 20th to 27th July 2012. This data was then interrogated to indentify the presence of any potential cultural heritage. The survey work was undertaken from the survey vessel M.V. Dulra Na Mara, under detection device licence 10R12 and the interrogation was carried out by Moore Marine.

2 CHARACTERISTICS OF THE PROJECT

2.1 Project Description

The Atlantic Marine Energy Test Site (AMETS) is a facility to provide prospective developers with a grid connection and licensed berth location to test their full scale prototype wave energy devices. There will be a number of components to the facility which include offshore berth facilities in pre‐designated box areas of varying water depth and power cables from the box areas to a land based substation where connection to the national grid will occur as detailed below:

• Offshore berths at two depths:

o 100m Water Depth Mooring Location

o 50m Water Depth Mooring Location

• Four submarine electricity cables to the mooring locations (two to 50m and two to 100m)

• Onshore substation to interface with the electricity network

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• Dedicated feeder overhead power line (wooden pole) from test site substation to Belmullet 38/20/10kV substation (construction responsibility of ESB Networks and outside the scope of this document).

Note that a third site surveyed initially termed the nearshore test area, close to Annagh Head was excluded on technical grounds from the project and was not included in the Foreshore Lease application.

Fig ure 1. Extract from Admiralty Chart 2420 showing berth locations in red and cable route in black (Berth C has been removed)

2.2 Wave Energy Test Site Location

The Annagh Head test site is located off west County Mayo, approximately 7 km from Belmullet. The proposed landing area is at Belderra Strand south of Annagh Head. This areas were chosen as assessment of the seabed geology concluded that the seabed offshore appeared to provide a more acceptable route for cabling.

The site is located in a small westerly facing bay between Annagh Head in the north and Cross Point in the south. The landside of the bay is characterised by variable sandy beach area and bedrock coastal fringes, which extend landward to sand dune formations and predominantly sand based vegetated land which is primarily used for grazing or is only scrub.

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Site access to the proposed landfall sites is good. The main access is off the R313 which passes through Belmullet. From there secondary roads lead the Annagh Beach and Emlybeg Beach. Secondary roads off the R313 provide additional access to Emlybeg Beach and Belderra Strand.

Figure 2. Proposed landing site with cable route in blue

2.3 Project Components

The proposed development will involve subsea cables and associated works at the landfall, allowing for connection into the distribution grid onshore. The project will comprise a number of components:

 Offshore cables in the sub tidal environment

 Cable landfalls in the intertidal environment to cable joint interphase bay

 Land cable connection to the substation

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 Offshore berths for wave devices

Offshore Test Area Locations;

The offshore test areas, Test Area A and Test Area B, were designed following consultation with Wave Energy Converter (WEC) developers and marine users, and were based on Marine Institute data and other survey data for the area.

Test Area A consists of an irregular boot shape designed to allow anchoring of the WEC on sediments ranging up to 7m in depth, while avoiding fishing ground in the area as much as possible. At the 50m water depth contour the test area consists of a box rectangular area, again located on sediments up to 7m in depth.

Submarine electricity cables

Wave Energy Converters (WEC’s) will be deployed within Test Area A and B and connected to the onshore electricity grid via electricity cables. The cable layout for the test site provides for two cable terminations at each end of the two offshore test area locations. Two cables will run from the cable transition bay at Belderra Strand to Test Area A (Approximately 16Km in length). The cables will be installed to an optimum depth of 1m below the seabed where sandy substrate exists. Surveys have indicated that a stony substrate is likely to be encountered along 4km of the cable route length and here the cables will be laid on the surface of the seabed and protected using suitable methods such as rock armour or concrete mattresses.

The cables will terminate within the test area. Within the test area, approximately 300m of each cable will consist of a dynamic riser cable, a flexible section of the cable which will allow connection to the WEC’s. This dynamic riser will be capped and left on the seafloor and protected as above. As the cable installation is likely to take place well in advance of the WEC’s deployment, the dynamic riser cable will need to be stabilised on the seabed until the WEC deployment takes place. The location of the dynamic riser cable will be marked by a surface marker buoy.

Two further cables will run for the land‐side cable transition joint to test area B. Each cable will be approximately 6.5km long. These cables will again be installed to a minimum depth of 1m below the seabed where substrate allows and suitably protected on the seabed where necessary ‐ although surveys indicate that the route for these cables has sandy substrate all the way. These cables will have 150m sections of dynamic riser cable which will be laid on the seabed and temporarily protected until WEC’s are deployed. They will also be capped and marked with a surface marker buoy. The cables will be deployed in a corridor with a maximum width of 200m and will converge as they near the shore to the landing location at Belderra Strand.

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2.4 Site Layout/Location details

County Mayo Townland Annagh, Emlybeg, Binghamstown, Cross, Ballymacsherron. OS Sheet number MO: 09 & 016 RMP number N/A NGR Varied Height +/‐ 10m O.D

Table 1. Location details

3 DESCRIPTION OF THE EXISTING ENVIRONMENT

3.1 Solid Geology

The geology of the region surrounding Annagh Head consists of Precambrian Schist and Gneiss.

3.2 Soil Type

The Geological Survey of Ireland records the broad physiographic division of this area as rolling lowland. It records that the principal soil is acid brown earths (90%) which has associated soils of gleys (5%), rogosols (3%) and podsols (2%). The parent material for this material is morainic sand and gravel and blown sands.

3.3 Landscape

The landscape surrounding Annagh is classified as rolling lowlands.

4 ARCHAEO‐GEOPHYSICAL SURVEY

Two geophysical surveys were undertaken of the proposed test site. The first survey was carried out from 28th September to 3rd October 2010. It covered the initial test site location; the offshore 100 m test area, the 50m test area and the cable route. Following a series of public consultation, the shaope of the test areas were altered. Consequently, a second marine magnetometer and side scan sonar survey was required to validate the original findings. This survey was carried out from 20th to 27th July 2012. It was undertaken under an extension to the previous licence to use a detection device 10R12.

The 2010 survey comprised 121.28 linear km of combined side scan sonar survey and marine magnetometer survey. The 2012 survey recorded 178.48 Km of combined data. In both cases the side scan sonar survey was carried out at 445 kHz with 75m slant range, whilst the overhauser magnetometer cycled

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every 1 second. Survey lines were planned at spacing increments of 50m and this arrangement of survey pattern coupled with the side scan sonar slant range ensured 100% overlap between all survey lines.

As per general operational procedures, the height of the side scan sonar towfish off the seafloor was kept to between 10 and 20% of the slant range. In certain situations this had to be modified to prevent snagging of potting gear ropes, however the increase in height did not appear to diminish seabed recognition capabilities. A remote controlled electrical sonar winch placed at the rear of the survey vessel was used to adjust the towfish height and an acoustic USBL (Ultra Short Baseline Positioning) system was used to position the towfish in relation to the survey vessel and the on‐board geo‐referencing station. The average survey speed was 5 knots and lengths of up to 300m of side scan sonar cable were deployed.

The magnetometer survey was carried out in tandem with the side scan sonar. 100m of magnetometer cable was deployed and a fixed layback was applied. This arrangement ensured that the magnetometer was sufficiently submerged to record the location of any significant ferrous objects.

Figure 3. 2010 Survey Lines

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Figure 4. 2012 Survey lines

4.1 Side Scan Sonar Survey

The aim of the side scan sonar survey was to record imagery of the seafloor on and adjacent to the berth areas and the cable route. This data was then examined for the presence of potential cultural heritage material.

4.1.1 System

The side scan system used was the Klein 3900 side scan sonar system. This is a towed system which is normally deployed off the stern of the survey vessel ‘MV Dulra Na Mara’ with the help of a sonar winch. Survey speed was 3‐5 Knots.

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Plate 1. Klein 3900 Side Scan Sonar

4.1.2 Frequency

The operating frequency of the side scan sonar system was 445 kHz.

4.1.3 Range

The normal operating range was 75m, however if possible archaeological anomalies were noted, these may be later re‐surveyed using a decreased range.

4.1.4 Slant Range Correction

Slant range correction was not applied during the data acquisition process.

4.1.5 Survey Pattern

The proposed survey pattern involved survey of the two berth locations and interconnecting cable routes using line spacing of 50% of the swath width.

4.1.6 Navigation

Navigation and track line information were provided by Hypack 2012 software. A number of pre‐survey grid lines were produced for the fieldwork. These gridlines were displayed on a helmsman display in the survey vessel and they provided the vessel skipper with a pre‐determined course to steer in order to ensure full survey coverage was achieved.

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4.1.7 Data Acquisition

Data acquisition was carried out on board the survey vessel using Klein’s Sonar Pro proprietary software. Later analysis was carried out using SonarWiz software.

4.1.8 File Format

Raw side scan sonar data was recorded in both XTF (Extended Triton Format) and SDF (Sonar Data Format) formats. These included layback, lag calculations.

4.1.9 Datum

All data was recorded in raw format using WGS 84, Geographic projection UTM (zone 29). This can later be transferred to Irish National Grid (1975 adjusted).

4.1.10 Geo‐referencing

Geo‐referencing was provided by an on‐board Trimble 232 ag DGPS. Geo‐referencing of the side scan sonar was provided by an Applied Acoustics Ultra Short Baseline Positioning System. The positional data from this USBL system was inputted directly into Sonar Pro to ensure correct positioning of the towfish at all times.

4.2 Marine Magnetometer Survey

The aim of the magnetometer survey was to record changes in the magnetic field investigate the proposed development for the presence of archaeological material.

4.2.1 System

The magnetometer system used was the Marine Magnetics Sea Spy overhauser magnetometer. It was towed 100m from the stern of the vessel, in tandem with the side scan sonar at a survey speed of 3‐5 Knots.

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Plate 2. Marine Magnetics Sea Spy Magnetometer

4.2.2 Cycling Rate

The proposed cycling rate for the magnetometer was 1 reading per second at a 1 Hz, this allows for maximum sensitivity of 15pT RMS. Faster cycling speeds such as 0.25 seconds are believed to reduce sensitivity hence the 1 second cycle was used.

4.2.3 Survey Pattern

The proposed survey pattern was the same as the side scan sonar survey.

4.2.4 Navigation

As with the side scan sonar survey, navigation and track line information was provided by Hypack 2012 software. A number of pre‐survey grid lines were produced for the fieldwork. These gridlines were displayed on a helmsman display in the survey vessel and they provided the vessel skipper with a pre‐ determined course to steer in order to ensure full survey coverage was achieved.

4.2.5 Data Acquisition

Data acquisition was carried out on board the survey vessel using Marine Magnetics’ Sealink proprietary software. Later analysis was carried out using Hypack 2012 and Surfer 9 software.

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4.2.6 File Format

Raw magnetometry data was recorded in ASCII XYZ format. This included layback and lag calculations.

4.2.7 Datum

All data was recorded in raw format using WGS 84, Geographic projection UTM (zone 29). This can later be transferred to Irish National Grid (1975 adjusted).

4.2.8 Geo‐referencing

Geo‐referencing was provided by our on board Trimble 232 agDGPS.

4.3 Multibeam data

Multibeam data of the proposed test site had previously been acquired by the Marine Institute from the survey vessel Celtic Voyager. The raw data from this survey was reviewed to identify potential archaeological features. The review methodology involved gridding the raw data in 5m grids using Caris Hips and Sips software. The data was then imported as a PFM into IVS Fledermaus. The PFM was then displayed as a scene, from where the analysis took place. This methodology allows the user to review the multibeam data, investigating seafloor anomalies to determine their length, height and profile. This exact procedure has been used successfully in several countries for the identification of low relief shipwrecks.

5 CHARACTERISTICS OF THE PROPOSED DEVELOPMENT

Consideration of the Characteristics of the proposed development allows for the projection of the ‘level of impact’ on any particular aspect of the proposed environment that could arise. For this section, the potential impact on Cultural Heritage is discussed. A full description of the development can be found in Chapter 4.

The proposed development will involve subsea cables and associated works at the landfall, allowing for connection into the distribution grid onshore. The project will comprise a number of components:

• Offshore cables in the sub tidal environment

• Cable landfalls in the intertidal environment

• Offshore berths for wave devices

These will each be examined and their potential impact on the cultural heritage resource will be discussed.

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5.1 Offshore Berth Locations;

The areas will be delineated by both cardinal marker buoys and other marker buoys in accordance with international regulations and in consultation with the Marine Survey Office (MSO) and the Commissioners of Irish Lights (CIL).

Test Area A, the furthest offshore, will be located in a water depth of 100m and will accommodate WECs such as Wavebob and Pelamis (described in Section 4). Test Area A will cover a total area is 6.9 km2 or 2.02 nautical square miles.

Test Area B will be located in 50m water depth and will accommodate WECs such as attenuators or Oscillating Water Column WECs (also described in Section). Test Area B will cover an area of 1.5 km2 or 0.44 nautical square miles.

The deployment and later recovery of WEC anchors (gravity, drag embedment, vertical Load or suction bucket) and the accompanying marker buoy anchors has the potential to impact and or uncover previously unrecorded cultural heritage deposits or features. Consequently, it is recommended that all operations which involve seabed impact or disturbance, such as anchor recovery, should be monitored by a suitably qualified archaeologist.

5.2 Submarine electricity cables

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The laying and later recovery of the submarine cables will have the potential to uncover and/or impact previously unrecorded cultural heritage deposits or features. Consequently, it is recommended that all operations which involve seabed impact or disturbance, such as a Pre Lay Grapnel Run (PLGR) or cable trenching operations, should be monitored by a suitably qualified archaeologist.

5.3 Cable lay vessel

Cable deployment will be performed by a dedicated cable laying vessel, which will lay the cable onto the seabed. The same vessel may also have a device to bury the cable into the seabed as the cable is laid. Such an embedment technique would typically be associated with ploughing in cables. Alternatively, a separate vessel may follow the cable laying vessel to perform the task. This embedment method would be used when trenching the cables using water jetting. Cable burial can be performed by either water jetting or ploughing.

Cable laying may be performed on a 24 hour basis to ensure minimal impact on navigation and on other users and to maximise efficient use of suitable weather conditions and vessel and equipment time. In addition to the installation vessel(s), additional support, supply and guard vessels will be involved with the operation.

Depending on the vessel specification, the cable laying vessel could be positioned using Dynamic Positioning (DP) or anchors. If the cable laying vessel is positioned using anchors then there is the potential

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for the anchor deployment and recovery operation to uncover and/or impact previously unrecorded cultural heritage deposits or features. Consequently, it is recommended that all operations which involve seabed impact or disturbance, such as anchor recovery, should be monitored by a suitably qualified archaeologist.

5.4 Cable burial

Cable burial is required as a safety measure to avoid damage and entanglement with third parties (for example with trawling gear or anchors), and to minimise the risk of ‘free span’ cable over gaps leading to cable fatigue. The optimum burial depth is 1m, although this will be confirmed by detailed subsea survey and burial assessment work as part of an Engineer, Procure and Construct (EPC) contract. Cable burial depths are likely to vary where seabed movement is identified and depending on how compacted different areas of seabed are. For example, if the seabed is very hard, a burial depth of 0.5m may be acceptable. Where cables pass through a test area, as in the case of Test Area B, an increased burial depth of up to 2m may apply and this will be supplemented by rock berm protection to highlight the presence of the cables to prospective WEC deployments.

Cable burial will be by means of a ploughing or water jetting, either simultaneously with, or after, cable deployment.

The laying of the submarine cables, by whatever means chosen, will have the potential to uncover and/or impact previously unrecorded cultural heritage deposits or features. Consequently, it is recommended that all operations which involve seabed impact or disturbance, such as cable trenching operations, should be monitored by a suitably qualified archaeologist.

5.5 Cable route

The four cables will follow a sandy substrate corridor over most of their length to the landing location on Belderra Strand. In sandy substrate areas the cable will be buried to a minimum depth of 1m below the seabed.

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5.6 Submarine cable landfall

The four cables will converge as they reach the proposed Belderra Beach landing area. The cables will run underneath the beach up to a cable transition joint bay located behind Belderra Strand. The cable corridor at the Low Water Mark will be approximately 40m in width reducing to a 10m corridor as the route approaches the cable transition joint bay location. The cables will be installed at a minimum depth of approximately 1m in conduits under the beach surface between the Low Water Mark and the cable transition joint bay. Conduits will be pre‐installed and secured using lean mix at the bottom of the cable trench, which will be backfilled with beach material. The cables will cross the intertidal zone, and works associated with their installation will temporarily affect the zone between the high and low water marks, as well as above the high water mark near the existing car park area.

The laying and later recovery of the submarine cables along Belderra Strand will have the potential to uncover and/or impact previously unrecorded cultural heritage deposits or features. Consequently, it is recommended that all operations which involve seabed impact or disturbance, such as the landfall cable trenching and joint bay construction, should be monitored by a suitably qualified archaeologist.

5.7 Cable transition joint bay

A cable transition joint bay will be constructed underground at the car park location at Belderra Strand. The approximate dimensions of the cable transition joint bay will be 7m long by 6m wide and 2m deep. The area over the jointing bay will be reinstated post construction to its pre‐construction condition. A triangular area behind the car park will be used as a temporary lay‐down area and for a mobile cable pulling winch. The creation and later removal of the cable transition joint bay will have the potential to uncover and/or impact previously unrecorded cultural heritage deposits or features. Consequently, it is recommended that all invasive groundworks should be monitored by a suitably qualified archaeologist.

5.8 Substation

The proposed substation will be constructed in the townland of Ballymacsherron, south of the L5233, which runs alongside Belderra Strand. An existing access track running parallel to a minor road will be used during construction and will be reinstated to its pre‐existing condition or improved. A hardcore access road will constructed off the existing track to the substation site. The creation and later removal of the substation site will have the potential to uncover and/or impact previously unrecorded cultural heritage deposits or features. Consequently, it is recommended that all invasive groundworks should be monitored by a suitably qualified archaeologist.

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6 ARCHAEOLOGICAL ASSESSMENT OF GEOPHYSICAL DATA

6.1 Side Scan Sonar

Figure 5. 2010 & 2012 Side Scan Sonar Mosaic of Survey Area

6.1.1 100m water depth offshore test area

The side scan sonar survey of the 100m water depth offshore test area covered an area which measured a maximum of 3.5km in length and 3.2 km in width. The results of the survey indicated that the seabed in this area was uniformly flat, comprising mainly of medium to coarse sand. The side scan sonar was the most effective seabed imaging tool in this area, as it successfully recorded the flat fine grained planar surface of the seabed. It recorded four small pockets of differentiated seabed (possible gravel) located both to the north and the south of the test area, as well as one rock outcrop to the east. All were not of archaeological significance. The side scan sonar imaged nine anomalous features on the seafloor in this berth. Two mooring anchors were noted, these were associated with the wave rider buoy and the navigation marker, which were placed in the survey area. Another small anomalous feature which was noted on the seafloor was considered to possibly be a lost ADCP (Acoustic Doppler Current Profiler) or an acoustic recorder used to record mammal passages through the area. It was very discreet, less than 1m in size with a low magnetic signature. Consequently the features were not considered to be of archaeological significance. Five of the seafloor features were unidentifiable, however their small size and low magnetic signature meant that it was unlikely that they were of archaeological significance. A full description of the identified anomalies is contained in Appendix 1.

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The high resolution marine archaeo‐ geophysical survey of the 100m water depth offshore test area did not appear to indicate the presence of any potential cultural heritage in the area.

Plate 3. Small anchor associated with ADCP

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Plate 4. Met Buoy anchor and cable on sandy seafloor and in the water column

Plate 5. Small rock outcrop on eastern side of Test Area A

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Plate 6. Gravel patch in western side of Test Area A

6.1.2 Cable route from 100m water depth offshore test area to 50m water depth offshore test area

The side scan sonar survey of the cable route from 100m water depth offshore test area to 50m water depth offshore test area provided a very good image of the area. The survey area measured almost 9 km in length and 0.7 km at its widest. Close to the 100m test area, the seafloor rises very gradually and appears to be composed mainly of medium to coarse sand. A large almost 20m high rock outcrop is encountered almost 1km east of the 100m test area. After this the seafloor returns to a gradually sloping medium to coarse sandy seafloor. The seafloor continued in this manner, rising gradually for the next 3.2 km. Rocky outcrops reappear 4.2 km west of the 50m water depth test area and continue in a random manner up to the test area. Large areas of rippled sandy seafloor and channels are interspersed between these rock outcrops, throughout this area.

The survey recorded the presence of one seafloor anomaly (Contact 10) at the western end of the corridor. This was considered not likely of archaeological significance as it was a singular linear feature with a low magnetic signature.

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Plate 7. Rocky and sandy seafloor along Test Area A cable route

6.1.3 50m water depth offshore test area

The survey area of the 50m water depth offshore test area measured 1.5km in length and 1.5Km in width. Similar to the 100m test area, two buoys, one navigation marker and one meteorological buoy were located at the test area during the survey. The signatures of both these features were noted by the side scan sonar and the magnetometer. The side scan sonar recorded the location of the anchor chain and pattern, whilst the magnetometer recorded the localised magnetic variation.

The results of the archaeo‐geophysical survey for this area indicated that areas of rock outcrop are situated towards the northern end of the test area, whilst a flat sand and cobble substrate is recorded on the southern section. The survey did not record the presence of any cultural heritage in this area

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Plate 8. Image of mooring chain at 50m box

Plate 9. Rocky and sandy seafloor in Test Area B

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6.1.4 Cable route from 50m water depth offshore test area to extent of offshore survey

The survey of the cable route from the 50m water depth offshore test area to extent of offshore survey, measured almost 6.5 km in length and 0.6 km in width. The side scan sonar recorded that much of this route comprises rippled seafloor sandwiched between rock outcrops. A number of rock outcrops were noted on the northern boundary of the survey route. These ranged in height from 5 to 8m and are interspersed throughout the survey route. A large reef was noted 1.2 – 1.4 km from the eastern terminus of the survey. This rose to within 5m of the surface at the time of the survey. A low gradient flat rippled sand seafloor lay in the interior of this reef.

The geophysical survey of the cable route did not reveal the presence of any material which could be indicative of the presence of cultural heritage in this area.

6.2 Magnetometer

The marine magnetometer survey did not record the presence of any significant ferrous materials which may be representative of previously unrecorded cultural heritage. It recorded a magnetic variation of 255 nT throughout the entire site. The recorded magnetic ranged varied from a minimum of 49,098.01 nT at the lowest range and 49,353.08 nT at the highest range. The survey recorded a number of small variations in the general magnetic field, as well as a series of broader magnetic changes. The areas of broader magnetic changes when cross referenced with the side scan sonar results indicated that these were caused by geological magnetics. The areas of smaller magnetic change were generally located on the boundary of these broader changes. The areas immediately surrounding the metrological buoy and the navigation marker were avoided as they could have potentially damaged the equipment. The magnetometer survey did not record the presence of any potential cultural heritage material in the development area.

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Figure 6. Results of 2010 Magnetometer Survey

Figure 7. Results of 2012 Magnetometer Survey

6.3 Multibeam bathymetry

Third party multibeam data was acquired for the project by the Marine Institute. The raw data was provided to Moore Marine for archaeological analysis. This data was reviewed using the previously

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mentioned methodology and software. Typically this procedure is good for recording the presence of larger buried material >10m. It is not very good for identification of smaller features as multibeam sonar does not provide the material differentiation which one gets with side scan sonar. Notwithstanding this, the review of the multibeam data did not indicate the presence of any previously unrecorded anomalies which may be indicative of the presence of cultural heritage material. The data, in general, concurred with the findings of the side scan sonar survey data.

Figure 8. Multibeam data being reviewed in IVS Fledermaus

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Figure 9. Multibeam data of the AMETS site

7 DISCUSSION & RECOMMENDATIONS

7.1 Discussion

7.1.1 The Development Area

The Annagh Head test site is located off west County Mayo, approximately 7 km from Belmullet. The proposed landing area is at Belderra Strand. The area was chosen as assessment of the seabed geology concluded that the offshore seabed appeared to provide a more acceptable route for cabling.

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7.2 Assessment of Potential Impacts

Direct Impacts

The archaeo‐geophysical survey did not record the presence of any potential cultural heritage material on or adjacent to the subject site. A number of modern features were navigation markings and meteorological buoys. None were considered to be of archaeological significance.

Although the geophysical survey did not record the presence of any upstanding material there is potential for buried remains to exist either at the berth locations or along the cable route. Consequently there is potential that the project has a direct, negative and long term impact on any archaeological material which may be present.

‘Do nothing’ impact

If the proposed development were not to proceed there would be no negative impact on the archaeological or cultural heritage resource.

‘Worst case’ impact

Under a worst‐case scenario, by way of its form and function, the construction of a trenched cable route in this area will have a permanent and negative impact on any previously undiscovered archaeological material which may be contained within the area.

7.3 Recommendations

Based on the results of the assessment, it would appear that this area is low to medium archaeological potential. The geophysical survey did not record the presence of any archaeological material at the proposed development zone. Notwithstanding this, there is potential for buried and previously unrecorded archaeological material to be contained on the subject site. Consequently, it is recommended that all invasive subsea works be monitored by a suitably qualified archaeologist.

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8 APPENDIX 1. SIDE SCAN SONAR CONTACTS

Contact image Contact Details Contact Description Contact 1 Dimensions  Sonar Time at Target: 07/20/2012 18:39:55 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 9 Meters (X) 415743.47 (Y) 6015912.19 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 1 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data1207201 Avoidance Area: 83400.xtf Classification 1: Unknown  Ping Number: 8941 Classification 2: CONF 3  Range to Target: 39.74 Meters Area:  Fish Height: 57.77 Meters Block:  Heading: 190.200 degrees Description: Unknown narrow  Event Number: 0 linear target, low relief, with a  Water Depth: 0.00 possible buried central portion.  Line Name: sonar_data120720183400 Possibly a small length of rope most likely not of archaeological significance

Contact 2 Dimensions  Sonar Time at Target: 07/20/2012 19:18:10 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 2 Meters (X) 415497.82 (Y) 6016953.15 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120720191 Avoidance Area: 700.xtf Classification 1: Small anchor  Ping Number: 26024 Classification 2: CONF 4  Range to Target: 60.03 Meters Area:  Fish Height: 36.24 Meters Block:  Heading: 47.500 degrees Description: Small anchor or  Event Number: 0 mooring with a second smaller  Water Depth: 0.00 anchor to the southeast.  Line Name: sonar_data120720191700 Possibly the site of the lost ADCP

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Contact image Contact Details Contact Description Contact 3 Dimensions  Sonar Time at Target: 07/20/2012 19:42:42 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 0 Meters (X) 415313.20 (Y) 6013567.22 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120720194 Avoidance Area: 100.xtf Classification 1: Unknown  Ping Number: 36984 Classification 2: CONF 3  Range to Target: 45.42 Meters Area:  Fish Height: 47.90 Meters Block:  Heading: 271.100 degrees Description: Most likely not a  Event Number: 0 feature as this is located on a  Water Depth: 0.00 turn. Probably caused by  Line Name: sonar_data120720194100 acoustic bunching

Contact 4 Dimensions  Sonar Time at Target: 07/20/2012 19:54:47 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 2 Meters (X) 415359.67 (Y) 6015513.55 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120720195 Avoidance Area: 100.xtf Classification 1: Unknown  Ping Number: 42386 Classification 2: CONF 3  Range to Target: 57.20 Meters Area:  Fish Height: 52.34 Meters Block:  Heading: 17.500 degrees Description: Very small  Event Number: 0 anomalous bulbous feature  Water Depth: 0.00 sitting proud of the seafloor.  Line Name: sonar_data120720195100 possibly remnants of a lost lobster pot

Contact 5 Dimensions  Sonar Time at Target: 07/20/2012 20:32:29 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 4 Meters (X) 415496.98 (Y) 6014454.91 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120720202 Avoidance Area: 600.xtf Classification 1: Anchor  Ping Number: 59219 Classification 2: CONF 3  Range to Target: 35.03 Meters Area:

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Contact image Contact Details Contact Description  Fish Height: 48.18 Meters Block:  Heading: 6.600 degrees Description: Roughly oval  Event Number: 0 seafloor feature with hollow  Water Depth: 0.00 centre. A small length of cable can be seen on the south-  Line Name: sonar_data120720202600 western edge. Most Likely an

anchor relating to a seafloor

deployment

Contact 6 Dimensions  Sonar Time at Target: 07/21/2012 09:48:55 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 0 Meters (X) 415996.31 (Y) 6013881.20 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120721094 Avoidance Area: 600.xtf Classification 1: Mooring  Ping Number: 51292 Classification 2: CONF 4  Range to Target: 22.12 Meters Area:  Fish Height: 41.11 Meters Block:  Heading: 12.500 degrees Description: Mooring block with  Event Number: 0 associated seafloor scour  Water Depth: 0.00  Line Name: sonar_data120721094600

Contact 7 Dimensions  Sonar Time at Target: 07/21/2012 10:17:06 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 0 Meters (X) 416687.47 (Y) 6015642.08 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120721100 Avoidance Area: 800.xtf Classification 1: Mooring and  Ping Number: 63881 cable  Range to Target: 75.84 Meters Classification 2:  Fish Height: 37.87 Meters Area:  Heading: 191.200 degrees Block:  Event Number: 0 Description: Mooring block with  Water Depth: 0.00 cable visible travelling through  Line Name: sonar_data120721100800 the water column. Also noted on previous lines.

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Contact image Contact Details Contact Description Contact 8 Dimensions  Sonar Time at Target: 07/21/2012 11:31:52 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 3 Meters (X) 416283.97 (Y) 6014566.07 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120721112 Avoidance Area: 600.xtf Classification 1: Unknown  Ping Number: 97278 Classification 2:  Range to Target: 76.14 Meters Area:  Fish Height: 37.69 Meters Block:  Heading: 1.200 degrees Description: Small seafloor  Event Number: 0 anomaly.  Water Depth: 0.00  Line Name: sonar_data120721112600

Contact 9 Dimensions  Sonar Time at Target: 07/26/2012 14:27:06 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 0 Meters (X) 417200.48 (Y) 6014122.93 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 0 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120726142 Avoidance Area: 300.xtf Classification 1: Unknown  Ping Number: 50444 Classification 2: CONF 3  Range to Target: 46.82 Meters Area:  Fish Height: 50.88 Meters Block:  Heading: 5.100 degrees Description: Irregular seafloor  Event Number: 0 anomaly located near a rock  Water Depth: 0.00 outcrop. Possibly an extension  Line Name: sonar_data120726142300 of the outcrop

Contact 10 Dimensions  Sonar Time at Target: 07/26/2012 17:23:49 Target Height: = 0 Meters  Click Position (Projected Coordinates) Target Length: 7 Meters (X) 417967.88 (Y) 6013757.37 Target Shadow: 0 Meters  Map Proj: UTM84-29N Target Width: 1 Meters  Acoustic Source File: Mag Anomaly: C:\SonarSurveys\Survey003\sonar_data120726172 Avoidance Area: 300.xtf Classification 1: Unknown  Ping Number: 129373 Classification 2: CONF 3  Range to Target: 45.90 Meters Area:

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Contact image Contact Details Contact Description  Fish Height: 61.03 Meters Block:  Heading: 157.200 degrees Description: Possible outcrop on  Event Number: 0 seafloor  Water Depth: 0.00  Line Name: sonar_data120726172300

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9 APPENDIX 2. BIBLIOGRAPHY

American Society of Civil Engineers (ASCE) (1998). Hydrographic Surveying. ASCE Press.

Binns A. 1985. Towards a North Sea Kingdom: Viking Age incursions and later attempts to establish a Scandinavian rule "west over the sea". In The North Sea. A Highway of Economic and Cultural Exchange, ed. A Bang‐Andersen, pp. 49‐62. Norway: Norwegian University Press

Blackwell, M. (1992) Ships in Early Irish History, Ballinakella Press, Whitegate

Blondell, P. (2009). The Handbook of Side Scan Sonar, Praxis Publishing, Chichester, UK.

Byrnes, M.R., Crowell, M. and Fowler C. (2003). Shoreline Mapping and Change Analysis: Technical Considerations and Management Implications. Journal of Coastal Research. Special Issue 38.

Ellis, M.Y. (1978). Coastal Mapping Handbook. Department of the Interior, U.S. Geological Survey and U.S. Department of Commerce, National Ocean Service and Office of Coastal Zone Management, U.S. GPO, Washington, D.C.

Fish, J.P. & Carr, H.A. (1990). Sound Underwater Images, a guide to generation and interpretation of side scan sonar data. Orleans M.A.

Fish, J.P. & Carr, H.A. (2001). Sound Reflection; advanced applications of side scan sonar. Orleans M.A.

Friel I. 2003. Maritime History of Britain and Ireland. London: The British Museum Press

International Hydrographic Organisation (IHO) (2005). Manual on Hydrography, 1st Edition. International Hydrographic Bureau, Monaco.

Moore, L.J. (2000). Shoreline Mapping Techniques. Journal of Coastal Research. Volume 16. Pages 111 to 124.

The National Ocean Service's (NOS) (1976). Hydrographic Manual, Fourth Edition. National Oceanic and Atmospheric Administration, Maryland, U.S.

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