CONFIDENTIAL - All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorisation from Mallin Consultants Ltd. Site Visit Draft 2 Prepared for Foras na Mara Galway, Ireland Site Visit for the Galway Bay SmartBay Cable Project 14 August 2012 Prepared by: Peter Phibbs, P.Eng, MICE Phone: 604-987-6625 E-mail: [email protected]330 Tempe Crescent, North Vancouver, B.C. V7N 1E6
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Site Visit Draft 2 Prepared for Foras na Mara
Galway, Ireland
Site Visit for the Galway Bay SmartBay Cable Project
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Revision Issue Date Issued to Revisions Draft 1 10 August 2012 MI First draft for comment Draft 2 14 August 2012 MI Additional detail added for system ground and shore
station
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Executive Summary
Following the issuance of its Status Review for the Galway Bay SmartBay project on 9 August 2012, Mallin Consultants was contracted to undertake a site visit to the proposed landing site in Spiddal to review landing options and advise the Marine Institute on their suitability.
The two options identified in the Status Review were the West Beach, north of the West Breakwater, and the West Breakwater (Figure 1-1). The West Beach was considered suitable, but there was insufficient data on the foundations of the West Breakwater to make any recommendations.
Figure 1-1 West Beach and West Breakwater
Figure 1-2 Small beach to south of West Breakwater
Prior to the site visit, a small beach directly south of the West Breakwater was added to the landings to be considered (Figure 1-2).
During the site visit a landing on the end of the West Breakwater was identified, and is considered the most appropriate landing. The West Beach remains possible, but a risk of sand depetion which would expose the cable has been identified. This depletion would not put the cable at risk, but would expose it and possibly cause concern amongst the public. The small beach to the south of the breakwater is not considered suitable due to the rocky approach and the rocky foreshore. It is likely that this beach will also suffer from sand depletion in some years.
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Table of Contents 1 Introduction ........................................................................................................................................... 5
2 Approach to the Landings ..................................................................................................................... 5
4 Landings on the breakwater .................................................................................................................. 8
5 System Ground .................................................................................................................................... 11
6 Route to shore terminal ....................................................................................................................... 13
Figure 1-1 West Beach and West Breakwater ........................................................................................ 3 Figure 1-2 Small beach to south of West Breakwater ............................................................................. 3 Figure 2-1 Route to Landing ................................................................................................................... 5 Figure 2-2 Route showing areas of identified seabed obstructions and survey lines .............................. 6 Figure 2-3 Route showing existing survey and energy test site .............................................................. 6 Figure 3-1 West Beach from the breakwater .......................................................................................... 7 Figure 3-2 Small beach south of breakwater from breakwater ............................................................... 7 Figure 3-3 Small beach from head of beach ........................................................................................... 8 Figure 3-4 Rock and tide pools at the head of small beach..................................................................... 8 Figure 4-1 Breakwater from West Beach ............................................................................................... 9 Figure 4-2 South face of breakwater from top of wall ............................................................................ 9 Figure 4-3 Offshore end of the breakwater from a boat ........................................................................ 10 Figure 4-4 North east corner of end of breakwater ............................................................................... 11 Figure 4-5 Ladder on North face of breakwater .................................................................................... 11 Figure 5-1 Rough ground near the proposed shore terminal ................................................................. 13 Figure 6-1 Potential shore station location............................................................................................ 14 Figure 6-2 Land cable route from breakwater on left to single storey proposed terminal building on right. ...................................................................................................................................................... 14 Figure 6-3 Footpath showing bridge in background ............................................................................. 15 Figure 6-4 Bridge over Spiddal River ................................................................................................... 16
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1 Introduction Three landing sites were considered. In addition to marine considerations, each side was reviewed for suitability for positioning a beach manhole for the cable splice, and for duct routes to a suitable building for terminal equipment.
2 Approach to the Landings The approach to each of the landings is a narrow winding strip of sand that extends from the river mouth to the bottom of the slope into Galway Bay. While the narrowness and winding nature of this route is not optimum, it is considered acceptable given the water depth, based on the use of divers to place the cable.
The landing on the breakwater is a nominal location, and should be adjusted once divers have surveyed the seabed and precise GPS coordinates have been established.
The cable route follows the sedimented channel, avoiding any obstacles or rocks that are apparent on the sidescan data. A discrepancy in location between the ONFOMAR and Dive Survey data was noted, and the GPS coordinates of the proposed route should be verified.
The proposed route runs slightly to the west into deeper water, avoiding an area of exposed rock, wrecks and other seabed obstructions. It then makes a slow sweep to the east towards the energy test site.
The route will be reviewed by the installer based on the equipment selected. It is likely that the installer will straighten the route from AC11 to AC16, allowing approximately 800m straight cable to provide resistance to the cable tension required to start the turn at AC16. It may also be necessary to install a cable anchor near AC11 to prevent the straightening of AC4 to AC10 due to tension from the installation vessel.
At the end of the turn at AC18, the route runs straight to the south-west corner of the energy test site. It is proposed to place the CEE in a corner of the test site so as to minimise impact on the users of the test site.
An alternate route which would return to the existing survey corridor and terminate in the north west cornet of the test site has been proposed. This route would minimise the amount of
additional survey, at the expense of some increase in cable route.
Either the current route or the alternate route should provide sediment throughout for cable burial. The amount of burial possible will depend on the tools used and the type of sediment. Burial is preferred by the Marine Institute since it will minimise any impact on the local shrimp trawl fishery. While this
Figure 2-1 Route to Landing
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fishery is very occasional in this area, it is preferable to have the cable buried to remove any concerns that the fishers might raise.
Figure 2-2 Route showing areas of identified seabed obstructions and survey lines
Figure 2-3 Route showing existing survey and energy test site
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3 Beach Landings
3.1 West Beach The West beach landing is suitable for a diver assisted cable landing (Figure 3-1). However, small boats are beached above the low water mark at various points on the beach, and the cable would have to be protected from beaching loads.
There is access to a public road at the head of the beach. A suitable location for the beach manhole would be either at the head of the beach or on the public road.
Figure 3-1 West Beach from the breakwater
The drawback to landing on West Beach is that there is a history of the beach occasionally losing its sand cover. While exposure of the cable will not be a risk to the cable, since this beach is used by the public exposure of the cable may cause public concern. This public concern could lead to negative press for the Marine Institute.
3.2 Small beach south of the breakwater There is a small beach just south of the breakwater that has been suggested as a possible landing point.
Figure 3-2 Small beach south of breakwater from breakwater
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Figure 3-3 Small beach from head of beach
Figure 3-4 Rock and tide pools at the head of small beach
The beach is detailed in Figure 3-2 to Figure 3-4. This is a small beach with a winding approach parallel to the breakwater. The approach has rock that is visible at low tide. There are likely to be boulders dislodged from the breakwater in the approach. To the south of the approach is a bedrock ridge.
The beach is part sand, part cobbles and boulders, suggesting a sand veneer, limiting cable burial. The head of the beach is an area of exposed bedrock, cobbles and boulders, with some tide pools. There is public access to the beach, and a well used public foot path crossing above the beach.
The small beach is not a preferred cable landing because the approach is too narrow and rocky; the sand cover on the beach is sparse and thin; and there is rock at the top of the beach that would have to be trenched to provide cover for the cable.
4 Landings on the breakwater The breakwater is a massive masonry structure with a sloping south face and a near vertical north face (Figure 4-1). There is an approximately 4m high wall above the breakwater itself that provides shelter for a roadway that extends to the end of the breakwater.
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Figure 4-1 Breakwater from West Beach
4.1 South face of the breakwater The south face of the breakwater is a high masonry wall built on an apron of loosely placed rocks. In some areas the masonry is covered with a skim of concrete (Figure 4-2). It is probable that some energy is dissipated by movement of the rock at the foot of the breakwater on the south side.
Figure 4-2 South face of breakwater from top of wall
Because of the exposure to the sea, the probable movement of the rock at the base of the wall and the difficulties of access, a landing on the south of the breakwater is not considered feasible.
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4.2 Offshore (east) end of breakwater
Figure 4-3 Offshore end of the breakwater from a boat
The offshore (east) end of the breakwater is characterised by a rock feature or pinnacle that provides protection to the end of the breakwater (Figure 4-3). This feature effectively blocks any cable route to the eastern end of the breakwater.
4.3 North side of the breakwater A landing on the north face of the breakwater appears to be feasible. Based on visual assessment of the seabed, there appears to be sand up to the wall of the breakwater on the north side. The approach would be from the east, with the cable route in line with the foot of the north face of the breakwater (Figure 4-4). Approximately 10m in from the end of the breakwater there is a vertical channel cut into the wall for a ladder (Figure 4-5). It appears to be feasible to route the cable up from the seabed into this channel, and to fix it to the wall in the corner behind the ladder.
Care would have to be taken to protect the cable from over bending, both at the foot of the ladder and at the top of the ladder. A trench would have to be opened up in the roadway at the head of the ladder to allow for the minimum bend radius (typically 1500mm). A representative of the council offered that placing a manhole in the roadway at the head of the pier and a trench to the top of the ladder would be feasible.
At the foot of the ladder the cable would be covered using cast iron protectors placed by divers. These cast iron protectors would extend out approximately 100m to around the -5m contour. The exact extent of cast iron protectors will be determined during the cable installation.
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Figure 4-4 North east corner of end of breakwater
Figure 4-5 Ladder on North face of breakwater
5 System Ground A system ground that is separate from any building grounds is required for the seawater return. This ground must provide low impedance and low current density, and have a design life which matches the life of the system. The resistance of the system ground must be confirmed throughout the system life.
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The system ground is often placed in the sea at the landing site, and cabled back to the shore station (Figure 5-2). If the landing is at the end of the breakwater, it would be appropriate to place the system ground electrodes in a flat, sedimented area clear of any vessel anchorage or grounding. A location approximately 20 – 30 m from the end of the breakwater appears possible, subject to diver inspection (Figure 5-1).
Figure 5-1 Possible location for sea ground electrodes
An alternative would be to measure the resistance of the soil in the ground adjacent to the proposed shore terminal building. It may be that the sand in this area is sufficiently conductive to offer a good
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ground. In that case a ground bed could be placed under the parking lot in front of the building, under the rough grasses near the building or under the beach in front of the building (Figure 5-2 and Figure 5-3).
Figure 5-3 Surroundings of potential shore terminal
Figure 5-4 Rough ground near the proposed shore terminal
6 Route to shore terminal A cable route will be required from the landing to the shore terminal. Depending on configuration, between one and three ducts will be required along this route. Three ducts are required if the power
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cable and fibre cable are separate, and if the system ground is to be installed in the sea at the landing site. Only one duct is required if the land cable has both conductors for power and fibres in a single jacket, and if the ground is to be placed near the shore station.
The closest suitable building to the landing sites is a small building near the seawall northeast of West Beach. The building is owned by a foundation and leased to a variety of local community groups and social services (Figure 6-1, Figure 6-2 and Figure 6-3).
Figure 6-1 Potential shore station location
Figure 6-2 Land cable route from breakwater on left to single storey proposed terminal building on right.
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Figure 6-3 Aerial view of shore route
Access from the landing to the building is along a public footpath (Figure 6-3). Ownership of the footpath was not confirmed during the site visit. The footpath is paved in places. There is a service duct under the footpath for future light installation, but it is anticipated that new ductwork will be required for the cable.
Figure 6-4 Footpath showing bridge in background
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There is a bridge over Spiddal River where the cable could be fastened to the web of the i-beam or to the underside of the bridge (Figure 6-4). Care will be required to avoid dropping debris into the salmon river below.
Figure 6-5 Bridge over Spiddal River
7 Shore terminal requirements The proposed building itself appears suitable. However, the amount of space and support required at the terminal station will depend on the connectivity that can be negotiated between Spiddal and the Marine Institute.
7.1 Communications requirements As discussed in the Status Report, it would be very advantageous to have a fibre optic link from the shore terminal to the Marine Institute that was at least as large as the link from shore to the Cable End Equipment (CEE), so that data could be seamlessly transmitted from the underwater equipment to the Marine Institute. Optimally, space would be provided on fibre such that the CDWM wavelengths from the CEE could be transmitted directly to terminal equipment in the Marine Institute without any other equipment being required. However it is likely that the backhaul provider will place equipment on the line to meet its normal operating procedures.
It may be that an economically feasible arrangement for backhaul of all of the data cannot be provided. In that case, some of the data processing and storage will take place in Spiddal.
An alternate to fibre would be a direct radio link to the marine institute, using Wi-Fi routers and some high gain antennae or microwave. Capacity will depend on conditions, from 50 to 300Mb/s. Unlicensed Wi-Fi would be inexpensive, and microwave would cost about €40,000. This capacity would handle the system control requirements and the low rate data, but would quickly be overcome
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with any video or acoustic data streams.
Figure 7-1 Typical 19” equipment racks (in very large space with underfloor wiring and cooling)
The space requirements for communications equipment depend almost entirely on the selected backhaul system. However it is estimated that any terminal equipment in Spiddal (as opposed to data processing and storage equipment) will fit into a single 19” rack.
7.2 Power requirements The power requirements for the system are modest. Including shore equipment they are not likely to exceed 10kW. They should therefore be within the capabilities of the electrical feed to the proposed shore terminal building. Some upgrade to the panel, or addition of a second metre for separate billing, may be required.
It is recommended that a UPS system be installed to, as a minimum, allow orderly shutdown in the event of a power interruption. The minimum capacity of the UPS should be 2 hrs at full current.
It is also suggested that an autostart generator and transfer switching be provided to eliminate power interruptions. The generator would have to be located in a well ventilated service room in the building or under a roof outside the building.
Space requirements for power in the terminal building will depend on vendors but are estimated to be three 19” rack units plus space for technicians to access. In addition the generator will require an external space.
7.3 Support space If the data is backhauled to the Marine Institute, once the system is established there will be very little requirement for support staff in spiddal. One work station should be ample.
If data processing and analysis is to take place in Spiddal, additional space will be required. Three work stations seems a reasonable estimate at this stage.
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8 Conclusion The preferred landing is at the eastern end of the north face of the breakwater. The beach landing on West Beach is also viable, but may lead to public concern in the event the sand migrates away and exposes the cable. The small beach to the south of the breakwater is not considered a suitable cable landing.
The sea ground could be placed off the end of the breakwater near the cable landing, or adjacent to the proposed terminal building.
The extent of the shore equipment in Spiddal, and the requirements for the terminal building, depend greatly on the services that can be obtained from Eircom or any other backhaul provider.
