Knights Brown was awarded this complex design and construction scheme to deliver the cruise berth levelling and extension works at Portsmouth International Port. The original berth was at height for passenger embarkation, but this meant loading was cumbersome. Our project brief was to lower the berth by 2.4m so that loading could be carried out at dock level and passengers embark via a gantry walkway. The design and construction brief also included extending the cruise berth by 40m and adding a further freestanding mooring structure, known as a dolphin. This would enable the port to receive cruise ships of up to 255m in length, opening up more of the cruise market for the city.
Delivering Full Design and Construction to a Challenging Programme
This project was to be delivered within a challenging timeframe. Works began on site in November 2019 and were due to finish before the start of the cruise season in the spring.
To achieve programme, we worked simultaneously on two fronts. Marine-based operations were undertaken from a spud leg barge with 330t crawler crane, the largest hydraulic pile driving hammer in the UK, (with a drop weight of 20-tonnes, a 16-tonne shroud and a maximum impact weight of 300 tonnes) and a supply barge.
The crane assembled on the barge was towed to Portsmouth, where it was fitted with a BSP CG300 hydraulic pile driving hammer. When installing the dolphin, the crane and hammer drove the central pile before the 61-tonne carousel structure was lifted over it. The carousel was then used as the temporary works structure during the driving of the remaining six piles, and remained in place as the permanent structure.
For the berth extension, the tubular piles, which weighed between 30 and 60 tonnes, were driven into the ground before being topped off in-situ.
In summary, the key marine activities and sequencing were as follows:
- Scour protection to end of the finger jetty locally removed to allow pile installation.
- Installation of 21 tubular piles to the berth extension, up to 33m in length and 1.2m in diameter, into the seabed. (Up to 14m of each pile sits below water, with 3m above the waterline and 16m below bed level.)
- Installation of the new dolphin (a free standing mooring structure).
- Modifications to dolphin 1.
- Installation of the precast and in situ concrete to the deck extension.
- Installation of the fenders, walkway to the new dolphin, bollards and mooring hooks etc.
Land-based operations were completed in two distinct areas utilising 160t and 80t crawler cranes. A third, 80t crane barge was also deployed for lighter lifts, such as preparing the tops of the new piles, grouting units and holding concrete pump hoses. Works sequencing included:
- Demolition of Area A
- Demolition of Area B
- Reconstruction of Area A (all materials lifted into area over Area B)
- Reconstruction of Area B
- Reinstatement of quayside furniture, fenders, M&E etc.
Accommodating Stakeholder Needs and Maintaining Port Operations during Covid-19
During the pandemic, construction works at Berth 2 continued while accommodating additional ship movements required to keep essential freight services incoming. Our team worked tirelessly to overcome resource and supplier deficiencies attributable to the situation, while keeping everyone on site safe. During this phase, despite the challenges, all beams and planks were installed alongside the new extension and several particularly large concrete pours were completed, including one of 800m3.
Throughout, Knights Brown maintained a flexible approach to facilitate the port’s operations as they continued to serve their customers. This included facilitating temporary mooring and berthing arrangements to allow two cruise vessels to berth over the Christmas/New Year period and other vessels to berth during inclement weather. All other frequent ship movements were also maintained throughout.
Just prior to completion, Royal Caribbean Cruises requested to bring Majesty of the Seas into Portsmouth for repatriation of crew and to pick up stores. We were able to make the berth available at short notice, accommodating at 268m, the largest cruise ship to ever have berthed at Portsmouth.
Driving Innovation, Cost Savings & Added Value
With the works being delivered for a local authority, cost savings and value for money (VFM) were a critical consideration of our approach. To maximise VFM, we focused on the following activities:
Concrete Pre-cast On Site
The concrete units for the berth extension were all pre-cast on site by our directly employed workforce. Due to the short procurement timeframe, we elected for self-delivery to better control the operation. Reduced lead in times ensured units would be produced to meet critical programme dates and required quality in a controlled environment. In placing each unit directly onto the pile, we eliminated the need for shuttering. It also afforded a more flexible approach, allowing on site adjustments to accommodate construction tolerances and design changes. We were also able to cast larger units while reducing transport and associated costs. Delivering these by road would have been difficult and if coming by sea from Ireland, there was the additional potential for delays caused by bad weather.
Off-site prefabrication of the dolphin structure
The new dolphin structure – including a prefabricated steel carousel – was built offsite and transported to Portsmouth by barge. The carousel structure (weighing approx. 60t) was lifted and placed over a central pile. The carousel served as a piling gate to drive the six perimeter piles through. Once all piles were driven to depth, the carousel was welded in position. This approach represented a quicker and more cost-effective solution than traditional methods.
Existing dolphin piles were due to be removed, however we proposed incorporating these into the new berth arrangement, reducing both demolition and new piling works. Sacrificial anodes, (cathodic protection) were also incorporated into the design to allow the existing steel pile assets useful working life to be extended.
Rigorous site surveys and due diligence
Our focus on this element of the contract led to further cost savings, not least due to thorough analysis of ground investigations to determine optimum pile design, and ultrasonic thickness surveys to enable the re-use of existing piles.
- Client: Portsmouth City Council for Portsmouth International Port
- Designer: Marbas Ltd
- Form of Contract: Design and Construction NEC3 Option A
- Procurement Method: Competitive tender
- Contract Sum: £5M
- Timescales: November 2019 – July 2020
Watch our timelapse recording of the construction works on our YouTube channel.