Design of Marine Protection Works for New Container Terminal in Karachi, Pakistan Steve Hinton Project Director, Royal HaskoningDHV, London, UK Farooque Chaudhry Local Project Director, Techno Consult, Karachi, Pakistan Mark Hill Project Manager, Royal HaskoningDHV, London, UK Alec Sleigh Technical Director, Royal HaskoningDHV, Peterborough, UK Siong Hong Ting Design Engineer, Royal HaskoningDHV, Peterborough, UK Summary This paper is a case study covering the planning and design of the marine protection works (breakwaters) for a new container terminal in Karachi, Pakistan for the Karachi Port Trust. The paper concentrates on the development of the plan layout for the breakwaters and the cross-sectional design of these structures. Introduction In 2006, Karachi Port Trust (KPT) commissioned a team led by Royal Haskoning (now Royal HaskoningDHV (RHDHV)) to carry out the planning, design and contractor procurement for the construction of a new state-of-the-art deep water container port at Keamari Groyne, which is situated to the south and at the approaches to Karachi Harbour, Pakistan (see Figure 1). The port is to accommodate container vessels up to 400m LOA (length overall) with a draft of 16m and a capacity of approximately 13,500 TEU (twenty-foot equivalent unit). RHDHV was responsible for management of the overall project including contractor procurement and supervision of the site investigation, masterplanning the port, preliminary and detailed design of the dredging, reclamation and marine protection works (breakwaters) and contractor procurement for the dredging and reclamation and marine protection works construction contracts. RHDHV also assisted KPT with the award of a concession contract for the provision of buildings, services, container handling equipment and operation for the first phase of the terminal. The concession was awarded to Hutchinson Port Holdings (HPH) in 2008 and the new facility is to be known as South Asia Pakistan Terminals (SAPT). Sub-consultants to RHDHV included Scott Wilson (now URS), HR Wallingford (HRW) and Techno- Consult International (TCI). URS contributed to the terminal masterplan and were responsible for preliminary and detailed design of the quay wall and contractor procurement for the quay wall construction contract. HRW was responsible for carrying out hydraulic modelling studies used for design of the marine protection works and real-time navigation studies which were carried out in consultation with the KPT Port pilots. TCI, who are based in Karachi, were initially responsible for co- ordinating and supervising the site investigations and surveys which were carried out by specialist sub-contractors and throughout the duration of the project contributed to the design and contractor procurement processes. The masterplan required the capacity for this port extension to be able to accommodate up to 10 berths in the future; however, Phase 1 is for the delivery of the first 4 berths, comprising 1.5km of quay wall, together with 75ha of container stacking yard to cater for a throughput of 3 million containers per year. Phase 1 also included over 30,000,000m3 of dredging, 4,500,000m3 of reclamation, over 5,000,000m3 of material stockpiled for use in the future development of the port, with the remainder of the dredged arisings dumped at sea, and 4.6km of marine protection works (breakwaters and armoured revetments). The breakwaters provide shelter and calm conditions for safe navigation of the container vessels in and out of the port and the armoured revetments contain the reclamation material which forms the container stacking yard. Following on from the design phase, RHDHV, along with TCI, are now carrying out the construction supervision for the dredging, reclamation and marine protection works construction contracts which are currently on-going and due to be complete in late 2013. The paper discusses the planning and design of the marine protection works. The design of these works was independently reviewed by Baird and Associates. N Figure 1: Location plan Wave Conditions at Site Weather conditions at the site are dominated by the two monsoon seasons. The south west (SW) monsoon which occurs in the summer months between May and September and is associated with hot and humid weather, heavy rainfall and strong and persistent winds which generate swell waves with long periods (12 seconds and above). These swell waves approach Karachi from the SW. The north east monsoon occurs in the winter months between December and February and brings some relief from the weather conditions that persist during the summer monsoon. The wave conditions at Karachi during the winter monsoon are also modified. Cyclones occur in the Arabian Sea during the SW monsoon season; however, a review of historical tracks has shown that there is no record of a cyclone hitting the city. Karachi does, however, suffer from the effects of passing cyclones and experiences strong winds, rough seas and swell and torrential rain. Layout of Breakwaters Initial Layout Following the decision to develop a new port to the east of Keamari Groyne, studies were completed to develop a layout of breakwaters that would provide acceptable wave conditions at the new berths and in the approach to the entrance. The final layout is provided in Figure 4; however, this section describes how this layout was developed. Initial layouts looked at the retention of the existing Manora Breakwater as the primary defence against the monsoon swell with a secondary structure (Keamari Breakwater) extending the existing Keamari Groyne to the south east by approximately 600m. The latter structure was to protect the new basin from swell passing the end of the existing Manora Breakwater. The layout also included the construction of a 2,800m long lee breakwater (Oyster Rocks Breakwater) to protect the basin from locally generated waves from the south east and to also prevent the migration of sediment from the Clifton foreshore into the new berths. This layout was tested by HRW in their wave penetration model, ARTEMIS and the results for a 1 year wave from 210° and 240°N are shown in Figure 2. Figure 2: Initial layout - 1 year waves The modelling indicated good conditions at the berths with wave heights less than 0.5m under a 1 year return period storm. However, conditions were a concern in the final length of the approach channel, at the confluence of the existing Lower Harbour and in the channel into the new port, where the modelling indicated wave heights up to 2.5m. This raised concerns over whether or not wave conditions were calm enough to allow tugs to be made fast to vessels entering the port (to help control navigation) and whether or not the vessel could reduce speed sufficiently and still maintain steerage into the new port. It was also important to ensure that the incoming vessel had sufficient distance to reduce speed and stop at the manoeuvring basin, located at the northern end of the port basin. Alternative Layout From these initial tests it was apparent that whilst the layout of the breakwaters provided acceptable conditions at the berths, changes were required to provide acceptable conditions in the navigation channel. An alternative layout was developed which extended the existing Manora Breakwater so that the roundhead was positioned close to the navigation channel. The Keamari Breakwater was removed from the layout because of the additional protection provided by the extended Manora Breakwater. Two variations to this layout were tested by HRW in their ARTEMIS model; one with the roundhead next to the channel and a second with the roundhead located 150m back from the channel. The results are illustrated in Figure 3 for 240°N. The figure indicates that extending the Manora Breakwater significantly improved wave conditions in the final length of the approach channel and further fast time simulations demonstrated that vessels would be able to safely enter and exit the harbour. With the wave height reduced to 1 to 1.5m, it would be possible to attach tugs to the vessels in the area behind the new breakwater. The modelling also demonstrated that the conditions were sensitive to the location of the roundhead and it was concluded that it should be located as close as possible to the channel. The extension of the Manora Breakwater also significantly improved wave conditions in the Lower Harbour (see Figures 2 and 3) which will be a benefit for the whole of Karachi Harbour. The wave penetration modelling has shown that the side slopes of the deep dredged channel into the port are, in part, responsible for the good wave conditions at the berths. The side slopes refract energy away from the channel (see Figure 3) and reduce the height of waves that enter the basin. This process, however, resulted in a concentration of energy along the west side of the channel and a focussing of waves towards the southern corner of the quay wall. There were concerns that this focussing of waves could result in poor conditions on the most southerly berth and a decision was taken to introduce a short stub breakwater to stop this energy entering the basin. This focussing of energy is shown in Figure 3 together with the short length of breakwater (Keamari Breakwater). Longer Breakwater Shorter Breakwater Figure 3: Alternative layouts – 1 year waves Final Layout The final layout for the new container terminal is shown in Figure 4. The marine works comprise the 1,100m long New Manora Breakwater, the 2,500m long Oyster Rocks Breakwater and the 300m long Keamari Breakwater. In addition, the works comprise the 700m long Keamari Revetment which is an extension of the Keamari Groyne and protects the reclamation fill for the new container yard. Figure 4: Final layout The final layout was verified using real-time navigation modelling which was also undertaken at HRW with the Karachi Port Pilots in attendance.