The Kowloon Byewash Reservoir was completed in 1931. Its completion was reported in the Public Works Department's Annual Report for that year:
141. Water from the new Byewash Dam became available on 16th January, 1931. This dam which forms the connecting link between the Kowloon Reservoir and the Shing Mun Supply has a capacity of 185.50 million gallons and provides a much needed addition to the mainland storage.
290. Item P, Byewash Reservoir.—This work was referred to in paragraph 248 (P) of last year’s Report. Fair progress was made with the works during the earlier part of the year, and by the end of May the dam was brought up to road level. Final cleaning down was completed early in August. Water was impounded from the beginning of the year and brought into supply on January 14th by connecting the 18" dia. draw-off to the existing supply main to the Kowloon Filter Beds. In June the Reservoir was emptied and the original 18" dia supply main from the Kowloon Reservoir 2,100 feet long, was recovered from inside the Reservoir basin during which time the supply to Kowloon Filter Beds was maintained from the Reception Reservoir. The Byewash Reservoir was then allowed to fill and overflowed on 11th August. The existing overflow channel from the Reception Reservoir has been diverted so that it now discharges into the basin of the Byewash Reservoir. The Access Road to the Shing Mun Filtration Plant which was continued beyond the dam as far as the Shing Mun Filters was completed in June. The dam is situated in the Lai Chi Kok Valley about 700 yards downstream of the existing Kowloon Dam and impounds the water which overflows from the latter as well as the overflow from the Reception Reservoir of the Shing Mun Valley Scheme. The Reservoir has a direct catchment area of ninety acres and a nett capacity of 185.5 million gallons. The top water level is 380.00 A.O.D. and at that level the area of the impounded water is approximately fifteen acres. The dam is of gravity section constructed of mass concrete with pre-cast concrete block faces. The up-stream face is vertical except between the levels of 320.00 and 350.00 A.O.D. where it has a batter of one in sixteen while the down-stream face has a general slope of one in 1.492. The height of the roadway over the dam above the lowest foundation level is 143'-6" and 118 feet above the original stream bed. The various mixes of concrete used in the construction of the dam are as follows:—
- To seal and upstream face 1 cement, 2 sand, 3 broken stone.
- To backing below 290.00 A.O.D. 1 cement 2 sand 4 broken stone with displacers.
- To backing between 290.00 & 330.00 A.O.D. 1 cement 2 1/2 sand 4 1/2 broken stone with displacers.
- To backing between 330.00 & 380.00 A.O.D. 1 cement 3 sand 5 broken stone with displacers.
- To Reinforced Cement Concrete Arches. 1 cement 2 sand 4 broken stone.
- To pre-cast Blocks. 1 cement 2 sand 4 broken stone.
- To dam above 380.00 A.O.D, Lime and cement concrete, with displacers.
The pre-cast blocks forming the up-stream face of the dam are smooth faced with level joints while those on the down stream face have an imitation rock facing with margin drafts.
291. The overflow section of the dam consists of sixteen twelve feet bays, and the ten feet wide roadway, which traverses the dam, is carried over the overflow section by sixteen reinforced concrete arches twelve feet span and two feet rise. The overflow is collected in two flood water channels which discharge into a water cushion fifty feet wide at the toe of the dam and thence over a sill into the original stream bed. A valve well is constructed centrally in the dam and is surmounted by a rectangular Valve House containing the operating gear for the various control valves. There are four 18" dia. draw-off pipes each controlled by an 18" dia. penstock and a 15" dia. Sluice Valve at levels of 300, 320, 340, and 360 A.O.D. and each is connected to an 18" dia. stand pipe. The 18" dia. supply main from the stand pipe crosses the South-east flood water channel on a reinforced concrete skewed arch bridge of 42'-0" span. A total of 29,300 cubic yards of concrete were placed in the works, the total number of blocks made being approximately 14,100 of which 7,200 were rock faced and 6,900 smooth faced.
292. The contractors for the works were the Hong Kong Excavation Pile Driving and Construction Co. who introduced modern equipment for the construction of the dam. Materials, except stone which was found near the site of the dam, were transported by road to a loading station at the East end of the dam and carried over the valley by overhead cableway to the mixing station. The sand and cement were deposited from the cableway direct into storage bins constructed immediately above a concrete mixer of one cubic yard capacity. The mixed concrete was hoisted inside a steel tower and discharged into a chuting equipment suspended from a cable slung across the valley. The pre-cast facing blocks were cast in gang moulds on a specially prepared concrete floor adjacent to the mixing station, the faces of the rock faced blocks being formed by cast iron moulds.
1931 Expenditure $217,883.07
Expenditure to 31st Dec., 1931 $518,623.89
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