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Island records

The largest capital project ever commissioned by the Jersey government is an architecturally driven energy from waste facility. Report by Martin Cooper.

Energy from waste facilities, where rubbish is incinerated to produce electricity, are becoming increasingly popular as a source of sustainable energy.

At La Collette near St Helier on Jersey one of these plants is to provide a reliable means of waste disposal.
Deriving energy from waste is regarded as the best option for a community with few waste management facilities and the plant will also be able to produce 10MW of power, equivalent to 7% of the island’s electricity usage.

The plant is on a headland next to an existing power station, with which it will share a chimney and cooling water. The prominent location meant that the plant’s appearance was a major design factor, says SpieBatignolles Camerons project director Andy Simm.

“The plant can be seen for miles around and so the design was very important to the States of Jersey. A building with some style and character was required.”

Exposed skeleton

The main steel exo-skeleton is left exposed outside the cladding perimeter and its large steel circular columns and roof trusses will also remain in full view.

“A steel frame was chosen for the structure to fit the overall architectural concept,” says Campbell Reith project engineer Will Shaw. “Additionally, to allow us to achieve the required open internal spans, it was the obvious option.”

Much of the project’s concreting works, including 9,000m3 for the main superstructure, were completed last year. This included walls, structures housing offices at one end of the building, and a 30m-deep refuse tipping bunker.

“A steel frame was chosen for the structure to fit the overall architectural concept and achieve the internal spans”

Will Shaw, Campbell Reith

 

More than 500m3 of concrete was used for the refuse bunker slab. This may not seem like a huge amount for mainland UK operations, but it is believed to have been the largest single concrete pour ever undertaken in one day on the island. Concrete supplier Granite Products used its entire fleet of nine trucks for 12 hours to complete the pour.

The steel frame is formed by six large 36m long roof trusses supported on 37m high circular columns. At roof level the trusses are tied together by a series of 16m long secondary trusses, while the two gable ends are formed with large box sections in a goalpost formation.

Delivering steelwork to Jersey from mainland UK provided another logistical challenge. The steel is transported by road to Portsmouth from subcontractor Bourne Steel’s facility in Poole, Dorset, and then shipped overnight by ferry.

But once on Jersey the loads were too big to be moved from the harbour to the site as parking restrictions were needed to allow the trailers to be manouevred around tight bends.

Stockpiling steel

So the steelwork was stockpiled in the port and all deliveries to the site were made on Sundays when there is less traffic on St Helier’s roads.

The long tubular columns had to be transported to site in three sections - two 15m lengths and a third 7m piece. The 5m deep roof trusses arrived in two equal sections, while most of the remaining steelwork was delivered complete.

“We have an assembly yard on site where the columns and trusses are welded, shotblasted and painted, before being lifted into place as complete sections,” explains Bourne Steel contracts manager Neil Senior.

As part of a separate contract, a further 400t of structural steel have been erected to support the internal equipment and to provide maintenance walkways.

Steelwork for the main facility was due for completion last month. The facility is due for completion in May next year.

 

Who’s who

Client States of Jersey
Architect EPR
Main contractor
Spie Batignolles Camerons
Structural engineer
Campbell Reith
Steelwork contractor
Bourne Steel
Steel tonnage 900t

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