Dredging and Dredged Material Beneficial Use in 3

COLM SHEEHAN, JOSEPH HARRINGTON and JERRY D. MURPHY

DREDGING AND DREDGED MATERIAL BENEFICIAL USE IN IRELAND

ABSTRACT Phil McGoldrick of GeoSolutions Ireland, 99% of Ireland’s imports and exports by Jonathon Wynn, Geosynthetics Consultant, volume and 90% of Ireland’s GDP This article provides an overview of the Michael O’ Carroll, Secretary & Harbour representing a value in excess of dredging industry in Ireland which may be Master of & Harbour € 120 billion. The shipping and maritime small by international standards but is of Commissioners and Ken Fitzgerald of transport sector has grown rapidly over the critical importance to the nation’s Ports and Malachy Walsh & Partners Consulting past decade, in line with general economic Harbours. Open sea disposal of dredged Engineers. They also wish to gratefully growth (Shields et al., 2005). However, material is most common, but a range of acknowledge the input of personnel in the owing to the current recession, the volume beneficial uses for the coarser fraction of port and dredging industries, regulatory of ship traffic through Irish ports declined dredged material has been practiced. agencies and other organisations who have by approximately 20% in the second half Details on different aspects of dredging in provided information for the project, as well of 2008 (Irish Maritime Development Ireland are presented including a review of as Dr. Tony Lewis and Dr. Jimmy Murphy, Office, 2009), with further reduction current beneficial uses. A specific site at Hydraulics and Maritime Research Centre, predicted as the global recession continues. Fenit Harbour in is examined to University College for their support. assess the potential for a specific beneficial The twelve main commercial ports in the use of dredged material using geotubes in are primarily semi-state breakwater and revetment structures. By INTRODUCTION ports (two are privately owned) operating using the dredged material that is normally independently in a competitive environ­ dredged and disposed at sea to fill the The Port and Harbour industry, and by ment. Fishery Harbours Centres, of which geotubes and construct a coastal structure extension the dredging industry, are vital to there are six in the Republic, are the primary a sustainable and feasible beneficial use of Ireland’s economic performance. As an fishing harbours in Ireland. A number of dredged material may be achievable. This island nation located in the northwest of smaller commercial harbours operate under case study may be applicable to other Europe, maritime transport accounts for the auspices of local harbour commissioners harbour sites in Ireland. or under the authority of local government. Above: A site at Fenit Harbour in Tralee Bay was Some € 200 million was identified for The authors wish to acknowledge the examined to assess the potential for the beneficial use investment under the National Development funding received from the Environmental of dredged material using geotubes in breakwater and Plan 2007-2013 to provide for the future Protection Agency under the Science, revetment structures. Seen here, the R558 road to Fenit viability of the fishing industry (Burke, 2009) Technology, Research and Innovation for Harbour looking west with revetment structure on but as a result of the current recession this the Environment (STRIVE) Programme eroding shoreline in foreground and Fenit Harbour in investment is no longer available and a 2007-2013. They would like to thank background. national infrastructure bond is to be 4 Terra et Aqua | Number 115 | June 2009

Table I. Legislative framework for dredging projects in Ireland (adapted from Harrington et al., 2004).

Legislation Responsible Agency Comments

Fisheries Act 1959 to 2006 Regional Fisheries Board Responsible for maintaining and improving environmental quality and the fishery resource. Water Services Act 2007 Local Authority (under the Ensures water is maintained to a standard consistent with its various (Water Framework Directive auspices of the Department of uses. This potentially can introduce additional controls on dredging (2000/60/EC)) Environment, Heritage and and dredge disposal activities with potentially significant cost Local Government) implications. Dumping at Sea Act Department of Agriculture, Application assessed by the Marine Licence Vetting Committee (MLVC) (1996 & 2004) Fisheries & Food and may involve consultation with Local Authorities and Regional Fisheries Board. Typical permitting timeframe of 4 to 6 months. Waste Management Act Environmental Protection Applied to any waste material segregated, stored or disposed onshore. (1996 to 2005) - Licenses Agency (EPA) Licenses are required from the EPA and take an average of 6 months to acquire. More complex cases can take up to 18 months. Applies to quantities greater than 100,000 tonnes. Waste Management Act Local Authority Applied to any waste material segregated, stored or disposed onshore. (1996 to 2005) - Permits Permitting timeframe of 21 days. Applies to quantities less than 100,000 tonnes. Waste Management Local Authority - Dublin City Applies to the Transfrontier Shipment of Waste. Regulations 2007 – Shipments Council of Waste Planning and Development Local Authority, Environmental Commonly required for large scale dredging projects in the Republic Regulations 2001 to 2002 Protection Agency, An Bord of Ireland. (85/337/EEC, 97/11/EC) Pleanála (project dependent) Foreshore Act (1933-1998) Department of Agriculture, Disposal between Mean High Water Mark and 12 nautical mile limit. Fisheries & Food Application assessed by the MLVC and may involve consultation with Local Authorities and Regional Fisheries Board. Typical permitting timeframe of 4 to 6 months. Planning Permission (Planning Local Authority Generally required for all developments. Public Consultation process & Development Act, 2000) required. Typical 3 month permitting timeframe (in parallel with other required permits) EC Quality of Shellfish Waters Department of Agriculture, These prescribe shellfish water quality and designate the waters to Regulations 2006 Fisheries & Food which they apply. Designation of shellfish areas (as advised by the EU) may impact on dredging. Conservation of Wild Birds National Parks and Wildlife 121 designated Special Protection Areas (SPA) in the Republic of Regulations 1985 to 2005 Service (DEHLG) Ireland for rare and vulnerable species with some impacting on (79/409/EEC) dredging projects. Natural Habitats Regulations, National Parks and Wildlife 413 designated Special Areas of Conservation (SAC) with some 1997 (92/43/EEC) Service (DEHLG) impacting on dredging projects. Wildlife Acts 1976-2000 National Parks and Wildlife This is an area considered important for the habitats present. Over Service (DEHLG) 1100 proposed National Heritage Areas (NHA). Many overlap with SAC/SPA. Some may impact on dredging National Monuments Act National Monuments Service 120,000 protected archaeological sites, some potentially impacting (1930 –2004) (DEHLG) upon dredging. Dredging and Dredged Material Beneficial Use in Ireland 5

COLM SHEEHAN Table II. Dredging Questionnaire Details. graduated in 2006 with a BEng in Structural Engineering from Cork Type of Organisation No. of Questionnaires No. of Responses Institute of Technology. He worked in a distributed civil engineering consultancy before Ports 13 10 (77%) returning to Cork Institute in a research position. He is Harbours 26 17 (65%) currently completing a PhD doctorate Marinas 43 8 (19%) titled “A Technical, Environmental and Other * 16 5 (31%) Economic Analysis of Dredge Material Total 98 40 (41%) Recovery and Reuse Techniques for Ireland”. This research is sponsored by * includes Irish Naval Base, Group, Bord Gáis Éireann, Electricity Supply Board, Government Office the Irish Environmental Protection of Public Works and Local Authorities Agency under the STRIVE Research Programme. introduced by the Department of Finance to to individual ports, harbours, marinas and raise money for capital projects (Department other relevant regulatory agencies and JOSEPH HARRINGTON of Finance, 2009). Figure 1 shows the organisations in Ireland in 2007. The aim (BE, MS, PhD, CEng FIEI, EurIng, PE) is investment in Ireland’s Ports and Harbours was to gain a general understanding of the Head of the School of Building & Civil from 2000 to 2007. current status of the dredging industry and Engineering at the Cork Institute of to update a previous national dredging Technology, previously working as a survey undertaken in 2003 (Harrington et Coastal Engineer with Moffatt & Nichol THE IRISH DREDGING INDUSTRY al., 2004). A postal survey was undertaken Engineers, California and as a Lecturer with a follow up by phone. This survey in Civil Engineering at the Cork Institute The dredging industry in Ireland is small by information was supplemented by of Technology. He graduated from international standards but is essential to the information gathered from the Department University College Cork with Bachelor operation of Irish Ports and Harbours. The of Agriculture, Fisheries and Food (formerly and Doctoral Degrees and University of historic average annual maintenance dredge some of its responsibilities were under the California, Berkeley with a Masters requirement for disposal at sea is Department of Communication, Marine Degree. His research interests include approximately 1.2 million wet tonnes for the and Natural Resources) website on recent sediment behaviour, transport and Republic of Ireland (OSPAR Commission, dredging projects. The locations for which management in river, estuarine 1997-2006), accounting for approximately data is available are shown in Figure 2. and coastal environments. 73% of the total offshore disposal volume. Practically all maintenance dredged material Questionnaires were sent to 98 groups/ is currently disposed off-shore with organisations with an overall response rate JERRY D. MURPHY approximately 40% of capital dredge of 41%. Details are presented in Table II. (BE, MEngSc, PhD, CEng MIEI) is a material (the coarser fraction) used in some Additional information was gathered from Lecturer in Transportation Engineering in form. An overview of the Irish Dredging regulatory agency data yielding information University College Cork and principal Industry is presented in here based on an for a total of 47 locations. The data investigator in the Environmental analysis of a dredging questionnaire survey gathered included a wider range of Research Institute at the University. supplemented by other available information. dredging projects and locations then the A civil engineering graduate of University previous 2003 survey (where 63 College Cork (1989), he completed a The Legislative Framework questionnaires were distributed with a 53% Masters Degree on Anaerobic Digestion The legislative framework governing response rate). (1992) and a PhD on energy production Ireland’s dredging industry is rigorous and from wastes (2004). His research stringent. Depending on the type of project The two-page questionnaire required interests include bio-energy and bio-fuel planned the various licenses and permits information on the last major dredging systems. required can take between 3 months for project undertaken by the relevant a relatively simple project and over organisation and specifically requested 18 months for a complex project. details on: A summary of the current legislative - Type of dredging project framework is presented in Table I. - Volume dredged - Equipment utilised The Dredging Questionnaire Survey - Dredged volume used A dredging questionnaire survey was sent - Type of beneficial use practiced 6 Terra et Aqua | Number 115 | June 2009

quay from 5.4 m to 7.5 m and reinstated €100 an old turning circle which had suffered €80 extensive siltation. - Rossaveel Harbour (66,100 m³), in €60 , where dredging was required to create a new ferry basin, a €40 small craft harbour basin and to widen existing berths. €20 - The Electricity Supply Board (ESB)

Annual Investment (Millions € ) upgraded one of their generating stations €0 at Aghada in County Cork which 2000 2001 2002 2003 2004 2005 2006 2007 involved the laying of a new pipeline

Harbour Investment Port Investment 400 m from the shoreline. The total quantity dredged was 16,500 m³ of Figure 1. Investment in Irish Ports and Harbours from 2000 to 2007 (McNally, 2008; O’Brien, 2008). which 2,500 m³ of granular material was used as backfill. - Dublin Port dredged 80,000 m³ to The survey returned a significant amount of likely to continue as funding for such improve its bulk handling facilities. information that is stored in a database and developments is now more limited. - Castletownbere Harbour dredged has been analysed. This database is a 140,000 tonnes of mixed sediment and MySQL database management system and Recent capital dredging projects of note 29,000 tonnes of rock as part of a will shortly be made available online to include 120 metre pier development. A portion allow relevant organisations and regulatory - Warrenpoint Harbour (25,000 m³) in of the uncontaminated dredged material authorities access to the data. The online Northern Ireland that deepened 300 m of was used in land reclamation. system will allow additional information to be uploaded as necessary and will provide a key resource for the industry in Ireland. Buncranna

Capital Dredging Greencastle Analysis of the survey data shows that 46% Maintenance Dredging of the total dredged volume is from capital Both Londonderry projects with the remainder from maintenance dredging projects. The Larne Killybegs Northern dredged materials particle size distribution Ireland Bangor is 6% gravel, 38% sand and 55% silt and Belfast clay. Sediment contamination was found at a limited number of sites including the fishery harbours of Killybegs and Castletownbere (presence of TBT) where Dundalk Warrenpoint Greenore large scale dredging has been undertaken Republic of Port Oriel Drogehda Ireland Bord Gais as part of pier developments. Approaches Roundstone Interconnector Rossaveel Malahide to dealing with the contamination varied – Galway Dublin Poolbeg Dun Laoighaire at Castletownbere the contaminated layer Wicklow Bray was dredged using an environmental grab ESB Moneypoint dredger, brought ashore, stabilised with a Killimer cement product and then exported to Kilrush Foynes River Nore Arklow Germany for treatment. However, at Fenit ESB Tarbert Killybegs the contaminated material was left undisturbed New Ross Waterford Rosslare The proportion of capital dredged material Cork (46%) is significantly down from 71% in Hanbowline the previous survey of 2003, indicating that Castletownbere ESB Aghade Kinsale the amount or size of capital dredging Keelbeg projects around the country has decreased relative to the 2003 survey. This trend is Figure 2. Locations of dredging projects with available data. Dredging and Dredged Material Beneficial Use in Ireland 7

Table III. Annual Maintenance Dredge Requirement for the Main Ports. A number of dredging projects are currently underway or recently completed: - The Limerick Tunnel is one of the largest Port Average Annual Frequency of Dredging dredging operations in Ireland in recent Maintenance Dredge years with 900,000 m³ of material being Requirements dredged; it is currently under construc­ (Wet Tonnes) tion. 500,000 m³ of this dredged material Port of Waterford1 520,000 Annually is to be used in backfilling the tunnel. 2 - The dredging of approximately 18,000 m³ Dublin Port Company 394,240 Annually of material for a 2 km gas pipeline in Drogheda Port Company2 317,120 Annually County Mayo has just been completed. Port of Cork1 176,400 Annually - Caladh Mór in the Aran Islands in County Shannon Foynes Port Company2 126,000 Annually Galway has recently completed dredging 3 works of 35,000 m³, the majority of Dundalk Port Company 58,800 As Required which is rock and has been used on site. Rosslare Europort1 42,500 Approx. every 7 years - The pier of Cill Ronain in the Aran Islands Port of New Ross2 27,276 Annually has also been dredged generating Dun Laoghaire Harbour Company1 11,875 Approx. every 8 years approximately 100,000 m³. 3 - A new € 300 million deepwater port for Galway Harbour Company 9,000 Approx. every 10 years Bremore, County Louth is currently at Wicklow Port1 400 Approx. every 5 years design stage. Port of Greenore1 None Not Required - A reclamation of 300,000 m² of land for a new port area for Waterford Port is 1 Survey results, 2 Dumping at Sea Licence Applications & Permits Issued (Department of Agriculture, Fisheries and planned. Food), 3 Harrington et al. (2004) - Other planned developments of note are the proposed Port of Cork relocation, development of Greystones Harbour, 20% with Dublin Port and Belfast Harbour also planning reclamation works for 2% expansion purposes.

The annual maintenance dredge requirement for the commercial ports is presented in 57% Table III based on the survey analysis and 21% other available information. The five ports with the largest dredge requirement contribute approximately 90% of the Ports Harbours Marinas Other Republic of Ireland’s total annual national maintenance dredge requirement. The larger Figure 3. Proportion of dredging classified by type of organisation. ports currently operate under 5 year Dumping at Sea Licenses with a number of small harbours such as Bunbeg Harbour, pipeline laying and tunnel construction. in recent times the TSHD and bed leveller Drogheda Harbour, Fenit Harbour, Portmore In capital dredging only 16% of material have been used to achieve the optimum Harbour, Buncrana Harbour and Greencastle was generated by the commercial ports output for the dredging project. For the Harbour operating under or have applied for while harbours account for 35%, marinas volume dredged the THSD is the most similar licensing arrangements. 2% and other projects, as outlined above, productive, dredging over 62% of the total; account for 47%. 88% of maintenance dredgings and 32% The questionnaire survey indicates that 57% of capital dredgings. of the volume dredged is undertaken by the The method of dredging/type of dredging main commercial ports (see Figure 3). The plant used was also investigated in the External contractors are now used for all harbours account for 21% of all dredged survey. The most popular type of plant for large-scale dredging works. These include, material generated with only 2% of the maintenance dredging was the trailing for example, Tideway, Royal Boskalis, volume dredged attributed to marinas with suction hopper dredger (TSHD) while for UK Dredging, Dutch Dredging B.V., and the remaining 20% classified as ‘Other’ capital dredging the backhoe dredger was Van Oord. There are a number of Irish ports which consist of projects such as gas the most popular. In maintenance projects and harbours who have purchased dredgers 8 Terra et Aqua | Number 115 | June 2009

Capital Dredging Maintenance Dredging economic viability, transport logistics, environmental constraints and the length of 44% 99% time involved in instigating such a process owing to the licenses and permits required.

Figure 5 shows the beneficial uses practiced for the coarser grained fraction of dredged

56% material. Some examples of use include, 16,000 m³ in the Castletownbere Harbour 1% Development, 238,000 m3 in the Killybegs Harbour Development and 1000 m³ in the Vol. Disposed Vol. Reused Vol. Disposed Vol. Reused Port of Larne for land improvements on Figure 4. Volumes of dredged material disposed or used. site. Londonderry utilised its port owned dredger to bring ashore approximately 34,000 tonnes of sandy material annually for use by the general public. However, 23% 22% with the purchase of the new larger dredger, the Lough Foyle, this activity will Land Reclamation no longer take place (McCann, 2008). Fill Material Land Improvement 6% CURRENT ISSUES/TRENDS IN THE Construction Related IRISH DREDGING MARKET

26% Beach Nourishment The larger ports (Cork, Dublin, Drogheda, 23% Shannon Foynes and Waterford) now operate under 5 year Dumping at Sea Figure 5. Beneficial uses of dredged material as a percentage of volume used. Licenses. A number of smaller ports and harbours are currently investigating the possibility of acquiring a long term in recent years. In some cases this has been replace an older TSHD and to supplement dredging contract or are operating under a multi functional vessel that can be used the use of the Harbour’s other dredger, this licensing regime. for other activities on site. The most used is the Otterbank, which is a plough dredger. the grab hopper dredger (GHD), the Hebble The Department of Agriculture, Fisheries Sand, which is based in Dundalk Harbour. The Otterbank is leased out to several local and Food is encouraging the ports to apply The harbour purchased this dredger in sites annually. The Ports of Cork and Dublin for these licenses allowing timely and full 2004 as there was a gap in the market recently purchased multi-purpose vessels. consideration of alternatives to disposal at place for a dredger that would undertake The Rosbeg and the M.V. Denis Murphy are sea. These types of contracts benefit both dredging work in smaller harbours. This used for buoy handling, plough dredging, parties as it ensures the dredging required dredger has been used in various sites towing and anchor handling. is carried out for the port authorities while around Ireland, in conjunction with ensuring that the dredging contractor is Dundalk’s regular maintenance dredging. guaranteed work over a longer time period. Shannon Foynes Port Company also has a BENEFICIAL USES: AN OVERVIEW GHD, the M.V. Curraghgour II, which is Some ports and harbours have or are based in Limerick Harbour all year round. Based on analysis of the questionnaire looking into the option of purchasing a Recently in 2007, Shannon Foynes Port survey approximately 20% of dredged small to medium sized dredger. This can Company invested € 2.4 million in a new material is being beneficially used with provide additional income to the harbour multi-purpose vessel, the Shannon I. practically all coming from capital dredging through leasing if the market exists projects. The use of maintenance dredged (O’Carroll, 2008). For example, The The boat is involved in dredging, bed material is approximately 1% (see Figure 4), Shannon 1 can be leased from its base in levelling and the maintenance of jetties. which may be unfavourably compared with Limerick for a basic charge of € 2,750 per The Port of Londonderry also purchased some European countries. When questioned day (8 hours) including fuel and crew. It two dredgers in recent years. The Trailing as to why beneficial uses were not also provides the harbour authority with Suction Hopper Dredger (TSHD), the Lough practised, the main reasons given were the greater control and flexibility over its Foyle, was purchased for € 2.2 million to engineering aspects of the material, dredging operation. Dredging and Dredged Material Beneficial Use in Ireland 9

Figure 6. Location and aerial photograph of Fenit Harbour in Tralee Bay.

The presence of contaminated sediments has to date been a localised problem in Irish ports and harbours but has involved export for treatment, at Castletownbere Harbour Harbour, for example. This will continue to Offices be an issue and will need to be addressed, for example, in the proposed Bantry Bay Harbour Development.

The beneficial use of the fine fraction of New Berthing Area dredged material in Ireland is limited and Original long term planning is essential for the Berths Original development of any such beneficial uses. Breakwater Location It would be fair to state that in all but the Relocated Breakwater larger capital dredging project that involve an Environmental Impact Statement (EIS) the potential for the use of the dredged material Extended in the past may not have been fully explored. Pier

The Department of Agriculture, Fisheries and Food has recognised this and now states on its Dumping at Sea License application form that “The dumping of Figure 7. Layout of proposed Harbour Development (Malachy Walsh & Partners, 2008). dredge spoil at sea is only acceptable when other means of disposal are ruled out for ecological or sound social or economic Licenses indicates the efforts being made to SELECTION OF BENEFICIAL USE SITES reasons. Even so, for ecological/ environ­ achieve a greater amount of sustainable mental/fisheries reasons the dumping of use of dredged material. Harrington et al. (2004) identified the the waste may not be permissible in all limited number of beneficial uses of cases” (Department of Agriculture, One might also suggest that in the future dredged material practiced in Ireland. Fisheries and Food, 2009). changing the wording from “dredge spoil” Cork Institute of Technology has since to dredged material might encourage undertaken research in this area with some This combined with the encouragement to viewing dredged material as a useful results having been presented in operate under 5 year Dumping at Sea product and not a waste. Murphy et al. (2008) and Sheehan et al. 10 Terra et Aqua | Number 115 | June 2009

Figure 8. Local Irish coastline suffering coastal erosion.

(2008). The current ongoing work has project. The aim is to identify a potential waiting list (O’Carroll, 2008). The main focused on analysis of proposed beneficial beneficial use methods that can be utilised deep-sea pier is 175 m long with extensive uses at specific dredging sites (where both for the proposed capital dredging storage facilities available. Liebherr Cranes beneficial use of dredged material has not project as well as subsequently for the is the primary commercial user of the been practiced to date) to show the irregular maintenance dredging on site. harbour. potential for such development at the site Fenit Harbour is typical of a number of with possible application to other dredging small harbours around Ireland, allowing the The land surrounding Tralee Bay includes a sites. Analyses of beneficial uses for research undertaken to be potentially number of protected areas. Fenit Island to dredged material at the Port of Waterford applicable elsewhere and also to potentially the north of the harbour is a designated and at Bantry Harbour, County Cork are influence more sustainable dredged Special Protection Areas (SPA) for the near completion as part of this research material management. protection of the local wildlife habitats. effort. Another study is briefly presented Most of Tralee Bay is a Special Area of below for Fenit Harbour in . Fenit Harbour is a small harbour in the Conservation (SAC). south west of Ireland as shown in Figure 6. It is under the jurisdiction of Tralee and Shoreline stretches along the bay suffer FENIT HARBOUR Fenit Harbour Commissioners. The harbour coastal erosion but available funding to itself is on the north side of Tralee Bay and address the problem is limited. Road Fenit Harbour undertakes periodic connected to the mainland by an 800 m collapses caused by the severe coastal maintenance dredging as required and is in causeway. The harbour includes a 130 erosion in the area have occurred; the most the planning stages for a capital dredging berth marina which is full with a long recent were in 2007 when two sections of road were damaged. The repair work for one section of road cost approximately New Eastern Breakwater € 4 million and Kerry County Council is still in debt as a result of that project, limiting the scope for further investment in coastal 3000 250mm Thk protection works. County Kerry, for Concrete Wall +7.00 CD -6.50 example, has a coastline of 684 km and it 1500mm Thk Rock Armour In is estimated that approximately 41 km of 2 Layers (1.0 Tonnes) this coastline is considered to require 700mm Thk Rock Underlay In protection at a cost of over € 30 million 2 Layers (0.1 Tonnes) (O’Sullivan, 2006).

Quarry Run 1.5 Current Proposal Core Geotextile 1 The Harbour Commissioners currently envisage two proposed developments; one to extend the existing breakwater (Figure 7), the other to provide coastal protection for a stretch of road connecting Figure 9. Cross-section of proposed traditional breakwater construction (Malachy Walsh & Partners, 2008). Fenit Harbour to the nearby town of Tralee Dredging and Dredged Material Beneficial Use in Ireland 11

(Figure 8). These schemes are outlined The second development involves the water to escape through the fine pores of below and propose the use of traditional protection of a stretch of coastal road the geotube. As the water drains from the rubble round structures. An alternative between Fenit Harbour and the town of geotubes, the contained slurry’s density approach is presented in here involving the Tralee, which is currently suffering severe increases to the required density. The two use of geotubes with potential cost savings coastal erosion, using a rubble mound proposed developments are close to the and use of dredged material. This illustrates revetment. The proposed construction is dredging project and, therefore, pumping the potential for such an approach at Fenit similar to a 200 m long local revetment distance is not an issue. Consultations with and also possibly elsewhere in Ireland. project completed in 2005 as shown in Geosolutions Ireland, Malachy Walsh & Figure 10. This stretch of road has had Partners, Kerry County Council, The proposed harbour expansion involves coastal protection in place, however, this quarry, the Department of Communication, an increase in the size of the marina and system is in disrepair and the remnants are Marine and Natural Resources and Tralee & improvements to the commercial harbour visible in Figure 8. A survey of the road by Fenit Harbour Commissioners have been facilities through extension and relocation Kerry County Council has been completed ongoing. Geosolutions Ireland have of the breakwater. to identify the areas most at risk. indicated that they would sponsor the cost of the geotubes for the revetment project Preliminary investigations and design have Alternative Proposed should it be funded, however this is not been undertaken by Malachy Walsh & This article proposes an alternative taken into account for this analysis to Partners and have been funded by integrating the dredging activities into the reflect the normal costs involved for other the sale of land owned by the Harbour construction of the breakwater and potentially similar projects. Commissioners. Further funding is currently revetment using geotubes which have being sought, with initial estimates for the extensive applications in dewatering and Geotube Design and Construction development of between € 10 million and marine structures. This would provide the The type of dredger is generally the most € 15 million. benefits of reduced dredged material important aspect of such a project as to fill disposal at sea and an identifiable beneficial the geotubes requires pumping at as high a A schematic cross-section of the proposed use. A further aim is to show that geotubes volume of solids as possible, preferably to rubble mound breakwater design is may be a practical, feasible and economic at least 40% solids. A specialised dredger presented in Figure 9 consisting of a quarry solution to local coastal erosion problems that can pump this high density slurry is run core, geotextile filter, a rock underlay when combined with maintenance required as most inland/port dredgers and 1 tonne rock armour layer. dredging, thus allowing future projects in provide only a fraction of the density The original breakwater shown in Figure 6 the locality to consider this innovative necessary to fill the geotubes. These pumps was constructed of material from Ardfert solution, or alternatively at another similar are submerged in the dredging area by Quarry (11 kms from Fenit), as well as from location in Ireland. hydraulic arms from onshore or from a (45 kms from Fenit). For this pontoon allowing most dredging locations analysis it is assumed that the Ardfert The geotubes are designed to receive and to be accessible. Also, smaller versions of quarry will supply the project. retain pumped sediment while allowing the cutter suction dredgers with 6-8” pipes can

Figure 10. Before (left) and after (right) revetment construction in 2005 (O’Murchu, 2008). 12 Terra et Aqua | Number 115 | June 2009

Table IV. Particle Size Distribution of sediment in Fenit Harbour (Aquatic Services Unit, 2005). The designs of the geotube breakwater and Sampling % Gravel % Sand % Silt/Clay geotube revetment are based on two Location >2mm 63µm-2mm <63µm different approaches. The first, a geotube and riprap structure, is similar to the Berths 0.0 45.6 54.4 traditional construction as only the quarry Pier 0.0 40.7 59.3 run core material is replaced by the filled Entrance to harbour 0.0 72.6 27.4 geotubes. The geotubes are stacked into position to form the desired shape and covered with a geotextile, rock underlay Table V. Amounts of quarry material required for the breakwaters. and a 1 tonne rock armour layer (this rock Quarry Material Traditional Geotube and ‘Pseudo’ Geotextile armour size is also assumed for the Breakwater Riprap Breakwater Breakwater revetment). Some quarry run core material may be required to shape the surface of (tonnes) (tonnes) (tonnes) the stacked geotubes. The only difference Core 388,930 56,873 56,873 between this method and the traditional Filter 41,194 41,194 21,659 method is in the volume of quarry run core. Armour 41,997 41,997 41,997 The second method, a ‘Pseudo’ Geotextile Total 472,121 140,065 120,529 Breakwater, is different as it utilises Quarry Material Saving 0 332,056 351,592 generally only geotextile materials on the inner wave protected harbour side of the breakwater to replace the quarried material Table VI. Amounts of quarry material required for the revetments. protecting the geotube. The exposed side Quarry Material Traditional Revetment Geotube and Riprap of the breakwater remains as outlined in (tonnes) Revetment (tonnes) Figure 9 above with rock armour. A small amount of quarry run core material may Core 4,855 1,456 still be required to develop the desired Filter 3,140 3,140 shape. This method utilises the geotubes Armour 8,757 8,757 but covers them on the sheltered side of the breakwater with a geotextile fabric Total 16,752 13,353 such as NAG 550 (an erosion control Quarry Material Saving 0 3,399 blanket) or a Triton Mattress (plastic gabion mattress). Table VII. Cost of construction for the different coastal structures. After consultation with Geosolutions Type Cost per Metre (€) Total Cost (€) Ireland and Jonathan Wynn (a geosynthetic consulting engineer), the design of the Traditional Breakwater € 17,754 € 7,921,000 geotubes for the breakwater was 5 metres Geotube and RipRap Breakwater € 11,545 € 5,124,000 wide by 2 metres high. The revetment ‘Pseudo’ Geotextile Breakwater € 10,669 € 4,737,000 geotubes are slightly smaller at 3 metres Traditional Revetment € 1,325 € 265,000 wide by 0.75 metres high owing to the slope they are lying at and the size of the Geotube and RipRap Revetment € 1,382 € 276,500 revetment required in comparison to the breakwater (for analysis purposes it is assumed to be similar in dimension to the be utilised. The filling of the geotubes from The sediment in the area was found to be revetment constructed in 2005 which the dredger must be continuous until the more than 40% sand which is sufficient to included quarry run material under geotube reaches its design height as allow the geotubes to be used as a geotextile). interruptions allow consolidation of the structural core. The particle size distribution material within the geotube, which may for three locations within the harbour are Utilising smaller tubes gives several benefits. deform the final shape. shown in Table IV. Chemical testing was With stacked tubes, as designed for the also undertaken on the material and suggested breakwater, a better shape can The material in Fenit Harbour has been showed that the material complied with all be achieved. There is drainage between the tested for its suitability for filling geotubes. relevant quality standards. geotubes and they can be tailored to the Dredging and Dredged Material Beneficial Use in Ireland 13

right size for slope and height purposes. 60% Also, smaller tubes are less susceptible to breakage (Wynn, 2008). It should be noted 50% during design that the final filled height will be 0.66 to 0.75 times the design diameter, 40% as the geotube is elliptical in shape. 30% Table V shows the quantities required, based on the design of a 444 m 20% breakwater length, for the three types of 10% breakwater structures proposed and the Increase in Project Cost amount of quarried material that can be 0% replaced with used dredged material. This shows that significant savings can be made 0.00% 50% 100% 150% 200% 250% 300% 350% on the cost of quarried material while using Increase in Delivery Distance local dredged material that would otherwise be disposed of at sea. Table VI Traditional BreakWater ‘Pseudo’ Geotextile Breakwater Geotube and Riprap BreakWater shows the details for the revetment. Figure 11. Influence of delivery distance on Overall Cost of Breakwater. Economic Analysis The costing of both the traditional method and the proposed alternative methods were €3,200 developed after consultation with market sources. The quarried material was sourced €2,800 and priced at the local quarry situated at Ardfert, approximately 11 km from the site. €2,400 The geotextile material was priced from Geosolutions Ireland. Consultation with a €2,000 Jonathan Wynn, geosynthetic engineer in the UK led to the design of the geotubes as well €1,600 as the pricing and sourcing of the dredger

required. Relevant costings and site drawings Cost of Revetment per metre €1,200 for the 2005 revetment were also acquired 11 17 22 28 34 39 45 50 56 62 67 through the Department of Communication, Marine and Natural Resources. The volumes Delivery Distance (km) of quarried materials required were Traditional Revetment Geotube and Riprap Revetment determined based on drawings acquired from Malachy Walsh & Partners. Figure 12. Cost comparison for revetments with increased delivery distance.

Table VII presents estimated current costings for the breakwater and revetment delivery and placement of this material. does not cover the capital costs of designs. The breakwater analysis shows From this it may be concluded that the purchasing the geotubes and hiring the that the traditional method is the most delivery distance from the quarry is a key necessary dredging and pumping equip­ expensive with the geotube with riprap and factor in the decision making process. This ment for this transport distance. The impact the ‘Pseudo’ geotextile breakwater both is highlighted in Figure 11 which shows the of transport is outlined in Figure 12. being less expensive. The primary factor is influence of an increase in the delivery For transport distances greater than the cost of transport from the local quarry. distance. approximately 25 km the geotube with riprap revetment is estimated to be more For the traditional breakwater the transport The revetment is a smaller structure (at an cost effective. costs account for approximately 33% of assumed 200 m in length) with the the overall cost of the project. The cost estimated costs presented in Table VII. The Integration into Dredging Programme reduction in the two alternative geotube geotube with riprap revetment is estimated Fenit Harbour Commissioners plan a capital breakwaters results not only from the to be more expensive for an 11 km quarry dredging programme for the proposed reduction in the volume of the quarried distance. The savings made in transporting harbour re-development. In addition a material required but also from costs in the and placing the reduced quarry material regular maintenance dredging programme 14 Terra et Aqua | Number 115 | June 2009

is in operation with a current 5 year protection structure being considered is Commissioners, Personal Communication. Dumping at Sea License in place allowing within pumping distance of a port or harbour December, 2008. 44,800 tonnes of material to be dredged with a dredging requirement. From a coastal annually. There is potential for the protection point of view, for example, a McNally, C. (2008). Conor McNally, Maritime proposed geotube coastal protection report on Coastal Zone Management in Transport Division, Department of Transport, scheme to be constructed in tandem with Ireland identified 1500 km of coastline that is Personal Communication. August 2008. the capital or maintenance projects. at risk from erosion, with some 490 km in immediate danger (Department of the Murphy, J.P., Riordan, J.D., Harrington, J.R. However, good communication, Environment, Heritage and Local (2008). “Construction and Demolition Waste and co-operation and consistent objectives Government, 2001). Geotubes, with the use Dredge Material as Landfill Liner in Ireland”, amongst all the relevant parties are of dredged material, may provide a 1st Middle European Conference on Landfill essential for successful implementation. sustainable beneficial use for dredge material Technology, The Hungarian Academy of based on local site conditions. Sciences, Budapest. The geotubes require a dredger that is not normally used in Ireland in standard O’Brien, O. (2008). Orla O’ Brien, Fishery Harbour dredging projects as it needs a higher REFERENCES and Coastal Infrastructure Development density of slurry to sustain the required fill Programme, Department of Agriculture, Fisheries rate. Coordination would be needed Aquatic Services Unit (2005). Fenit Harbour and Food, Personal Communication. April, 2008. amongst all parties including the Harbour Dredge Spoil Testing, Environmental Research Commissioners, the consulting engineers, Institute, University College Cork, Cork, Ireland. O’Carroll, M. (2008). Michael O’ Carroll, the Local Authorities and the dredging Secretary & Harbour Master, Tralee & Fenit contractor. This would allow one dredger Burke, R. (2009). The Development of Business Harbour Commissioners, Personal to carry out the capital and/or maintenance Plans for the Fishery Harbour Centres, Raymond Communication. January. dredging for the harbour but also produce Burke Consulting and Mclver Consulting, Dublin, a raw material for the geotubes. Ireland. O’Murchu, N. (2008). Noel O’Murchu, Department of Communications, Marine and The amount of dredged material that Department of Agriculture, Fisheries and Food Natural Resources, Tralee Office, Personal would be required for the proposed (2009). Application Form for a Dumping at Sea Communication. March. geotube breakwater is approximately Permit, Dublin, Ireland. 162,000 m³ and approximately 3,500 m³ OSPAR Commission (1997-2006), Dumping of per 200 m constructed of geotube Department of the Environment, Heritage and Wastes at Sea 1987 to 2006, London, UK. revetment constructed. By using the Local Government (2001). Coastal Zone dredged material that is normally dredged Management – Executive Summary, The National O’Sullivan, C. (2006). Minutes of the Ordinary and disposed at sea to fill the geotubes and Spatial Strategy - Indications for the Way Ahead, Meeting of Kerry County Council, C. O’Sullivan, construct a coastal structure a sustainable Dublin, Ireland. SEO Corporate Services, Kerry County Council, and feasible beneficial use of dredged June. material may be achievable. Department of Finance. (2009). Summary of Supplementary Budget Measures - Policy Sheehan C., Harrington J.R., Murphy J.P., Changes, Dublin, Ireland. Riordan J.D. (2008). “An Investigation into CONCLUSIONS Potential Beneficial Uses of Dredge Material in Harrington, J.R., Sutton, S., Lewis, A.W. (2004). Ireland”, WEDA XXVIII and Texas TAMU 39th The analysis presented above suggests the “Dredging and dredge disposal and reuse in Dredging Seminar, St. Louis, USA. cost savings associated with the use of Ireland – a small island perspective”, Proceedings geotubes for a breakwater development of World Dredging Congress XVII, B4-5, Shields, Y., O’ Connor, J., O’ Leary, J. (2005). such as at Fenit Harbour and the potential pp. 1-14, Hamburg, Germany. Ireland’s Ocean Economy & Resources, Marine for coastal revetment development. These Institute, Marine Foresight Series No. 4. economic benefits are also supported by Irish Maritime Development Office (2009). the environmental benefits which would The Irish Maritime Transport Economist, Dublin, Wynn, J. (2008). Jonathon Wynn, Consulting occur from a reduced volume of quarried Ireland. Geotechnical and Geotextile Engineer, Personal material, with a consequent reduction in Communication. November. the transport demand and a reduced Malachy Walsh & Partners (2008). Ken Fitzgerald, disposal at sea volume. Personal Communication. October, 2008.

This research may be applicable to a variety McCann, B. (2008). Bill McCann, Harbour of sites around Ireland once the coastal Master, Londonderry Port & Harbour