Knights Brown has successfully completed the construction of a 250m deep water berth at Portland Port, meeting the requirements of a demanding six month contract period and critical programme deadline.

Knights Brown was appointed as managing contractor for the port’s £25m investment, which went ahead under an innovative, alternative procurement route after competitive tenders exceeded the funds available.

The new deep water berth allows the port to simultaneously accommodate two 350m long cruise ships, the first pair of which have already arrived in port.

The works, which only got underway last October, also included a 75m extension to the Outer Coaling Pier and the creation of an additional 15,000m² of quay space to extend the total available area to 21,000m².

The principal operations included:

• Demolishing the original deep water berth and dolphin.
• Constructing a 410m combi pile wall comprising 136, 1.4m diameter, 24m long tubular steel piles separated by sheet piles.
• Anchoring each tubular pile with 32m long tie rods to a sheet pile anchor wall.
• Installing 25t precast concrete units on top of the piles to act as permanent formwork for the in-situ capping beam, itself comprising over more than 2,000m³ of structural concrete.
• Crushing and transporting (off road) 400,000t of locally sourced quarry waste to create a granular fill material to bring the extended quay area to level.

The project’s bespoke procurement arrangement saw Portland Port adopt a unique form of contract that relied on collaboration between all parties. Having chosen to work with Knights Brown to develop the approach, Portland Port agreed to carry the major project risks and directly procure high value materials and subcontract packages.

Knights Brown’s role as managing contractor was to adopt appropriate mitigation methods that would minimise the port’s exposure. Collectively, these measures allowed the project to be brought in line with the budgetary restraints without compromising the scope of works.

Kevin Valentine, Managing Director, Knights Brown, said: “Our intention was to find a way to deliver the full scope of what was wanted within the timescale and budget available. This has been achieved through true collaboration and cooperation, at quite astonishing speed.”

Prior to starting on site, Knights Brown worked closely with designers, Ramboll, to ensure buildability and maximise value engineering opportunities. A key driver of the design process was to allow rapid construction. Consequently, off site fabrication was prioritised as a means of meeting programme while also limiting works that had to be carried out over water and avoiding tidal activities.

The precast capping beam was an important contributing factor as it eliminated the need for shuttering and was designed to allow prefabrication of the steel reinforcement. Another important productivity gain was achieved with Red7 Marine, who together with specialist engineers designed a pair of bespoke piling gates to speed installation of the combi pile wall through improved accuracy and tolerance.