Castle Peak Power Station is situated on the Tap Shek Kok peninsula on the southwest coast of the New Territories of Hong Kong.

The power station has a total capacity of 4280 MW and is accommodated, together with a cement production plant, on a 90 ha site, much of which has been reclaimed from the South China Sea by depositing into the immediate offshore area some 7.2 million m3 of rock and soil excavated from the rugged hills forming the original coastline. The reclamation is retained and protected by a graded and armoured rockfill sea wall up to 35 m deep, topped by a wave wall 6.9 m above mean sea level.

The site is bounded on three sides by the sea and on the fourth by the backslopes formed by the hillside excavation. The photograph on the facing page shows a typical view of the backslopes which are some 1500 m in length and comprise a rockface up to 120 m high, capped by soil.

The geology of the site is predominantly the Cheung Chau Granite which varies in its degree of weathering from slightly weathered to completely decomposed granite. A 10 m wide feldspar porphyry dyke cuts the face sub-vertically at an acute angle and required special stabilization since its depth of weathering is considerably greater than the surrounding granite. Numerous other sub-vertical altered dolerite dykes, each less than 1.0 m thick occur, substantially normal to the excavated face.

Selection of a slope angle of 65° for the

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