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The Shing Mun Valley scheme was started in 1923 and initially a 2km-long 3m-diameter tunnel was driven to Shek Lai Pui. Subsequently, the largest pre-Pacific war reservoir was constructed, which was to double the Territory's total water storage capacity to 27,000 million litres; it was formed by the main Gorge Dam, which was the highest in the old British Empire at that time (1936), and the subsidiary 25m-high earth/rockfill/concrete core Pineapple Pass Dam. The remarkable Gorge Dam, 85m high with a bold and probably unique design, consists of a downstream shoulder of rockfill faced with pitching and an upstream face comprising a slender near-vertical reinforced concrete diaphragm wall supported by a massive concrete thrust block. Between the upper part of the thrust block and the downstream rockfill, there is a narrow wedge filled with sand for the purpose of taking up any settlement of the rockfill and to cater for possible earthquake movement. Any leakage through the upper part of the diaphragm can be observed from an inspection gallery behind it. Elaborate experiments were made to determine the correct design of the reservoir overflow bellmouth in order to reduce vortexing and to neutralise the destructive vacuum forces which could occur at the base of the bellmouth overflow shaft. For this investigative work, the young Geoffrey Binnie was awarded a Telford premium by the Institution of Civil Engineers. Subsequently, preliminary investigations for the Tai Lam Chung scheme were started shortly before the outbreak of the Pacific war, by which time the Territory's population had risen to about 1.6 million.
As a result of an acute water emergency on the Island, work started on a 300mm steel pipe cross-harbour main in 1929, the sixty-two 30m-long bolted sections taking less than 2 months to lay, and a further 450mm main was laid in 1935. Due to corrosion problems, it was necessary to replace these pipes in 1939 with two 530mm steel pipes, protected with a 12mm-thick cement lining on the inside and a 60mm coating of vibrated concrete on the outside, which were laid on reinforced concrete blocks bedded on rockfill with a protective rubble mound on the east side of the pipelines to prevent damage from dragging anchors.
These pre-Pacific war water schemes not only involved building dams but also needed construction, often in difficult site conditions, of a multiplicity of extensive catchwaters, tunnels, trunk mains, treatment plants, service reservoirs, pumping stations, and distribution mains in
96
The Shing Mun Valley scheme was started in 1923 and initially a 2km-long 3m-diameter tunnel was driven to Shek Lai Pui. Subsequently the largest pre-Pacific war reservoir was constructed which was to double the Territory's total water storage capacity to 27,000 million litres; it was formed by the main Gorge Dam, which was the highest in the old British Empire at that time (1936), and the subsidiary 25m- high earth/rockfill/concrete core Pineapple Pass Dam. The remarkable Gorge Dam, 85m high with a bold and probably unique design, consists of a downstream shoulder of rockfill faced with pitching and an upstream face comprising a slender near-vertical reinforced concrete diaphragm wall supported by a massive concrete thrust block. Between the upper part of the thrust block and the downstream rockfill there is a narrow wedge filled with sand for the purpose of taking up any settlement of the rockfill and to cater for possible earthquake movement. Any leakage through the upper part of the diaphragm can be observed from an inspection gallery behind it. Elaborate experiments were made to determine the correct design of the reservoir overflow bellmouth in order to reduce vortexing and to neutralise the destructive vacuum forces which could occur at the base of the bellmouth overflow shaft. For this investigative work the young Geoffrey Binnie was awarded a Telford premium by the Institution of Civil Engineers. Subsequently preliminary investigations for the Tai Lam Chung scheme were started shortly before the outbreak of the Pacific war by which time the Territory's population had risen to about 1.6 million.
As a result of an acute water emergency on the Island, work started on a 300mm steel pipe cross-harbour main in 1929, the sixty-two 30m-long bolted sections taking less than 2 months to lay, and a further 450mm main was laid in 1935. Due to corrosion problems it was necessary to replace these pipes in 1939 with two 530mm steel pipes, protected with a 12mm-thick cement lining on the inside and a 60mm coating of vibrated concrete on the outside, which were laid on reinforcedconcrete blocks bedded on rockfill with a protective rubble mound on the east side of the pipelines to prevent damage from dragging
anchors.
These pre-Pacific war water schemes not only involved building dams but also needed construction, often in difficult site conditions, of a multiplicity of extensive catchwaters, tunnels, trunk mains, treatment plants, service reservoirs, pumping stations and distribution mains in
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