Discovery Bay shipyard slipway repair

The shipyard's lifting platform runs on steel rails that continue below the waterline, down to about −4.8 m, and sections of the rails had worn.

Our repair: cut out the worn sections, fully weld in 20 mm steel plate, and add 10 mm stiffener plates every 800–1,000 mm, all done underwater.

We also surveyed seabed levels across the slipway on a grid to define how much silt needed to be removed.

From the drawings

Discovery Bay Enterprises came back to us many times. In 2005, 2007 and 2010 we desilted in front of the slipway to −4.5 m over about 42 × 30 m with a 6-inch submersible pump and airlift, with depth grids before and after. In 2007 about 3.5 m of heavily worn rail was repaired by welding on 20 mm plate with 10 mm stiffeners every 800–1,000 mm, and in 2008 the rails were strengthened with thicker galvanised plates. In 2019 we airlifted the pier again and cleaned residual grout out of a Ø1,050 mm pile casing.