Tsuen Wan stormwater culverts: guide rails and stop gates

To keep two stormwater culverts in Tsuen Wan dry for works inside them, each end needed a gate that could hold back water and be removed afterwards.

We measured each opening and designed an angle-steel frame anchored with M16 expansion bolts, a steel gate running in guide rails, a rubber gasket against the concrete, and a 4-inch valve to control the water level. The programme for each gate was short: 1.5 days to clear silt, half a day to deliver the frames and gates, 1.5 days to drill and fix the frames, and 1.5 days to fit the gate and seal the leaks.

From the drawings

The work was for Penta-Ocean under the Yeung Uk Road widening contract (TW/2008/01). Two sealing methods were drawn: a 15 mm rubber gasket, or a grooved seat with an 80 mm canvas fire hose inflated with water or air. Each gate is 10 mm plate in a 250 × 120 × 10 mm channel frame, running in 150 × 150 × 20 mm angle rails on M20 anchors, with a 4-inch relief valve. Programme: desilting 1.5 days, frame 1.5 days, gate and sealing 1.5 days. The gates were later removed the same way, and the design was reused at the Wan Chai East sewage pumping station in 2011.