Re-building the Scrubbing Dock

The job needed doing, there is no doubt about that. It just needed someone brave enough to take it on. Luckily for us Barry Gardiner was up for it. Taking the old dock apart was an adventure in itself and revealed some of the realities that would come to haunt us as the months went on. The work is hard and physical with potential for injury and infection. Most operations were subject to tidal availability and the vagaries of the weather. We have had more than our fair share of bad weather during this project.

We have tried to reduce the risks of slipping and becoming contaminated whilst working on the dock. This involves constantly cleaning the dinghy slipway and the concrete slabs of the foul sludge that settles there remorselessly. The best method is to start shortly after High Water and follow the ebb down. The tricky bit is judging when you can just get onto the slab without the water going over your wellies. Then it is a case of quickly agitating the sludge with the squeegee and possibly the broom over the whole slab before the water retreats and then finishing it off with the hose. That way there is a reasonable environment to work in. Bear in mind that the tidal cycle leads to some very early starting times and this operation is required nearly every working day. When the work is finished there is a need for frequent washing and disinfecting of work clothes. It’s virtually impossible to keep clean.

All that was left of the old dock after demolition were the six steel piles at the western end. Another eight new steel tubes were purchased and driven in by a JCB machine using the hydraulics to force them into the ground. Setting loads varied from 1.6 to 3.5 tonnes and gave an average of just under 2.5 tonnes each.

The next stage was to carefully measure between adjacent pairs of piles and then progressively order prefabricated steel beams from Nash’s, the local supplier, to form the top platform. They were collected on a trailer and then manhandled into position using tubular scaffolding for access. Once in position the beams were tack-welded. When all of the 25 top beams were in position the connections were fully welded by a specialist welding contractor. The main structure was completed with another seven connecting beams at low-level.

The decking material selected was Dura Tread, the same type of GRP material already installed on the walkway but using a deeper section. These sheets are incredibly heavy and all had to be handled and shaped to suit each location. Many tools were blunted in the process.

The intermediate framework to support the timber cladding consists of three rows of horizontal steel channels, welded between the piles. Every one of the 18 horizontal pieces was bespoke for its particular position. Making them fit the curved surfaces of the steel tube piles was an arduous process of cutting and grinding on site.

The vertical elements of the lattice framework are similar channels, pre-drilled by Nash’s to take the timber fixings. These are provided with fixing brackets, cut, drilled and welded on site,  to suit the connections to the horizontals. With the aid of cramps and temporary bolts, all the connections are drilled to receive the fixing bolts. The landward side of the dock has nine of these vertical supports, each carefully located to suit the timber cladding. The final steelwork operation was making and fixing mooring cleats to the piles. All this was then ready for steelwork preparation and painting.

The paint is a two-part epoxy and, as most of you will realise, preparation is everything.  We have worked hard to condition the new steel members by leaving them in the water and allowing the initial rust to get at the mill scale. This is then removed by wire-brushing and needle-gunning, followed by specialist liquid cleaning, pressure-washing and, finally, painting. Getting paint into all the corners and crevices proved to be another challenge. All of the landward side of the dock is now painted.

The last major operation was fixing the timber cladding which consists of planks of a West African hardwood called Ekki. This is cut and drilled as necessary and fixed to the vertical channels. The timber is apparently so dense that it doesn’t float. The planks are fixed with stainless steel bolts, countersunk into the face of the planks. The last of these on the landward side is now fixed and Dock 3 is open for business.

To those who have stuck with the project, I say “Thank You” To those who are dissatisfied with progress and the long time it has taken I say “Sorry, but that’s the way it has been”. Finishing the rest of the project will have to wait a little longer as Barry and his team take a well-earned break.

Martin Richards

Date Published 22nd Jul 2013