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Braving the elements

Building a new lifeboat station at Tenby has required ingenuity and luck, discovers Jackie Whitelaw.

The crew of the Tenby lifeboat still run through the town to the lifeboat station when the maroons go off, warning that they need to put to sea. 'We have to do the run because the streets are so narrow it takes too long to drive to the harbour, ' explains Steve Lowe, full time mechanic to Tenby's current lifeboat, the Sir Galahad.

They will continue to run when their new lifeboat arrives next year, but to a new station 80m east round the headland, being built for the Royal National Lifeboat Institution (RNLI) by main contractor Dean & Dyball.

Tenby's narrow Georgian streets have played a large part in the construction strategy for the new station, designed to house and launch the RNLI's latest 25 knot Tamar class lifeboat.

Access for plant and equipment is all but impossible: 'It's as difficult to get materials to the job as to build it, ' says D&D civils site agent Geraint Evans. So much of the work is being carried out from jack up barges at sea.

Tenby's new station replaces an old wooden boathouse built in 1905, the slipway of which was no longer deep enough due to siltation. The Sir Galahad has had to be moored offshore, slowing reaction times considerably. The new site has no siltation problems.

The station's height has been determined by the requirement for a minimum 2.7m depth of water at the end of the slipway for launching at a speed of 16 knots. 'You work back from there on a 1:5 gradient to where the boat sits, ' D&D project manager Graham Williams explains.

Its slipway is 72m long and the boathouse slab, sitting 19m above the sand, measures 22m by 16m. The boathouse itself is 9m tall. Its key feature is 6.2m deep boat well which will house a tipping cradle to precipitate the lifeboat into launch position.

In all, 41 piles, 19 for the boathouse and 22 in pairs for the slipway, have been drilled into limestone bedrock by subcontractor Seacore from its Deep Diver jack up to provide foundations. Now seven 19.5t concrete transoms and four lighter steel versions to support the steel slipway are being lifted in. These will be slotted onto the slipway piles from the smaller Skate IV jack up, on charter to D&D.

The first piles arrived on Deep Diver but the rest had to be brought out to site from Pembroke dock by catamaran, as were the transoms. 'It's a four hour trip, ' says Evans, 'today is the only time in the last two weeks we could get the cat here.'

To do the whole job like this would have been difficult, expensive and time consuming.

'The planners were extremely co-operative and allowed us to bring the 600m 3of insitu concrete for the deck in through the town. The only restriction is that we can't do the work in the summer when the town is full of tourists, ' says RNLI contract project manager Cei Herbert.

Next the Ministry of Defence, which owns land behind Penally Bay, just round the coast from Tenby, allowed D&D to site its marshalling yard there.

Then came a stroke of luck:

local Andy Aldred asked Evans if the contractor wanted to use his MB2 amphibious landing vehicle. He was greeted very enthusiastically. The ex-Nato Beaver drives materials over the beach and into the sea at Penally, then chugs it round to the boathouse where they are lifted off by crane.

Constructing the 800mm deep insitu deck slab required a brave decision from Evans. 'I could either support it from below or hang it from above. Looking at the tidal range convinced me that rather than propping the falsework we had to go with hanging.'

An RMD H33 girder system has been suspended from the tops of the piles. 'Just after the first pour we had some hefty weather and the underside of the falsework was damaged. That convinced me this was the right way to go, ' he says. 'If we'd propped from below it would have been a disaster. All the sea-borne debris would have knocked away falsework built up from the sand.'

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