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East Catchwater,
The East Catchwater would have a total length of 11,200 feet and would drain 314 acres. It would commence in the stream below Wongneichong Reservoir and follow the 400 feet contour to the gap North of Bennet's Hill where it would discharge through a tunnel 600 feet long into the reservoir.
The catchwater where in "soft" will be lined with cement concrete but will be unlined on the inner side where in rock. Necessary overflows, wash- outs and sand pits will be provided.
West Catchwater.
The West Catchwater would have a total length of 15,000 lin. ft. and would drain 496 acres. It would commence in the stream above Kellett Bay and contour the hill side at about the 380 feet level passing round and above the West side of the existing reservoir and discharge into the new reservoir at the North end of the Dam. It would be similar in construction to the East Catchwater.
Bennet's Hill Catchwater would have a total length of 4,200 ft. and drain 52 acres of the East and South sides of Bennet's Hill and would dis- charge into the Lower Reservoir.
Supply Mains.
East Catch-
water.
West Catch-
water.
Bennet's Hill Catchwater.
The supply main, which would be approximately 21,000 ft. in length and Supply Mains. 18" in diameter, would be either Cast Iron, or Steel, lined with concrete or bitumen. It would contour above the existing reservoir and join the Wanchai Gap-Aberdeen Road at the Gap west of the existing dam and follow the road as far as Aberdeen where the main Island Road is reached, and where a junction with a pipe from the existing reservoir would be made.
The pipe would follow the Island Road as far as Pokfulam Hill then join Victoria Road and follow it as far as Telegraph Bay.
Telegraph Bay would be crossed by means of an inverted syphon thus avoiding the Villa Miramere Gap which is too high and Victoria Road would again be reached 400 yards east of Sassoon Road and be followed as far as the Pumping Station at the re-entrant on the road above Sandy Bay,
This pipe would be capable of delivering 3 millon gallons per day with a total loss of head of approximately 60 ft.
Pumping Station.
Station.
Sandy Bay Gap over which the water has to be pumped has an elevation Pumping of approximately +355 ft. O.D. or pipe line level of, say + 340 O.D. while the cope level of Elliott Filter Beds is approximately +300 O.D.
Top Water Level of the Upper Reservoir is approximately +365 O.D. and the existing or Lower Reservoir+261.85 O.D., so for calculation purposes the pumping level of the water in the reservoirs can be taken as +340 and
+240 O.D. for the Upper and Lower Reservoirs respectively.
Necessary head to be pumped will therefore be (340-(340-60))—60 ft. and (340-(240-60)) = 160 ft. for the Upper and Lower Reservoirs respectively.
As the Pumping Station would be approximately 200 ft. above sea level and comparatively inaccessible, the cost of steam power would be high, owing to transport charges for coal, and I would therefore propose that electric energy be used. An electrical supply main is conveniently situated on Mt. Davis Road a few hundred feet distant.