Evolution, not revolution

Who wants to be the guinea pig? Not many in the ports industry would put their hand up to that question, and who can blame them? When a container terminal extension is needed, clearly it’s easier to come up with a ‘repeat design’ than start from scratch – especially in busy times.

“There was this period when the ports industry was very overloaded and everything was done in a rush, rush, rush, but now there is more time to consider things more carefully,” says Martin Mannion, global head of maritime and ports at consultancy firm Scott Wilson.

He says that while some clients are more receptive to innovative ideas, many only want to go with what is proven. “They want lower risk and are not willing to experiment. With anything a little bit unusual, clients ask, where has it been done successfully before – so sometimes it does take a while for innovation to get going.

“Often people working on a project may not be aware of all the options. And when it comes to building extensions, sometimes they do repeat because it is easy. It might be more critical to get it done quickly in order to deliver the project earlier and get revenue in earlier; so there are blockages to spending time coming up with something unusual.”

But taking a fresh look at the way port facilities are designed and built can save money, speed up construction, increase efficiency, reduce environmental impact and even open up the geographical options for such developments.

Scott Wilson was responsible for the design of an innovative caisson breakwater required to protect ships unloading at the Costa Azul LNG terminal off Baja California in Mexico.

The challenges included wave heights up to 9.2 metres, extreme Pacific Ocean swelling, a demanding schedule and the protection of sealife and seabed.

This was a daunting project – the sheer scale of which had never before been attempted for an offshore breakwater in such deep and challenging coastal waters, says Mr Mannion.

The breakwater was built of six-cell and nine-cell caissons, filled with sand after installation. Normally the friction between a flat concrete surface and the ground is quite low, but the design team made the choice to roughen the base of the caissons by casting serrations over the entire bottom surface. This allowed the caisson width and breakwater footprint to be significantly reduced.

To prevent scouring away of the seabed by the strong currents at the end of the caissons, the team used Core-Loc concrete armour units instead of large concrete blocks – these were easier to place accurately and, thanks to their interlocking, required much less concrete.

The caissons were cast in a purpose-built dry dock on reclaimed land on the beach, and towed to the site 24 kms up the coast. The largest was 25.5 metres high, 36 metres wide and 69 metres long, the equivalent of towing three connected nine-storey office blocks through the Pacific Ocean and sinking them to within 500 mm of the intended position.

The breakwater design won the British Excellence Design of the Year award in November 2009 and the Association of Consulting Engineers Infrastructure Innovative Design Award earlier this year.

“For us, the main feature was that the footprint of the breakwater was reduced and therefore environmental damage was limited and cost reduced,” says Mr Mannion.

Consultant AECOM has been involved in projects similarly involving major construction work offsite. This applies particularly to oil and gas jetties in Western Australia.

“We build large chunks of jetties offsite – in this case in Indonesia and fit cabling, piping and wiring to them; we take them to the site and lift them into place with a massive crane,” says AECOM’s global director ports and marine, Richard Clarke. “It is borrowing technology used in the North Sea, where they build and fit out production rig modules completely onshore.

“This method minimises the amount of over-water work you are doing – which makes it a lot safer during building and also means much lower environmental impact, because you are not dropping concrete or sending wash-down water into the sea.”

After pile-driving is complete, a pre-fabricated pile cap is put into place, ready for the pre-built spans, delivered by barge, to be dropped on top.

The method is being used for long, thin approach jetties, with modules up to 60 metres in length being lifted into place. Pipes are welded together onsite, but because this is already over the pile cap, there is a platform between workers and the water. “Generally this method can reduce onsite labour costs, time and risks,” says Mr Clarke.

Elsewhere, Halcrow picked up a pile of awards for its Dames Point Container Terminal design in Jacksonville, on the US east coast.

Innovative designs helped ease the schedule constraints and also identify sustainable solutions that were cost-effective and beneficial to the community, says Halcrow vice president Paul Starr, based in the US.

“The primary thing was our approach to dredging; we recognised that re-using the dredging spoil (for reclamation) was the most cost-effective and sustainable solution. So we started dredging out at the channel and moved our way in, in order to keep that material on the site, running all the activity in parallel.”

Halcrow also broke with tradition in using pulverised fly ash (PFA) to stabilise the hardstanding. Halcrow found that by mixing PFA with traditionally used lime rock, pavements were significantly strengthened, money was saved, and the project could make use of a lot of surplus PFA in the area.

“By using PFA, we saved $10m over an area of 160 acres,” says Dr Starr. “PFA is something the power companies want to get rid of; it cost us about $3 per cubic yard, compared to lime rock at $10.”

Making use of local materials makes obvious sense, says Scott Wilson’s Mr Mannion. “In the case of standard block paving solutions, maybe there is an asphalt plant next door. For breakwaters, you might take into account that there are quarries around that can actually provide the material. It might even be slightly below normal specs, but maybe you can be more flexible in design to take advantage of local materials, or accept that there will be slightly more maintenance going forward.”