167
18
Mr. Henderson in his minute dated 13.1.26 in C.S.0.3864/25 pointed out that the following savings in water from the mains could be made if salt water were made available:-
(a) Existing Public Latrine (metered)
(6) Existing Water Closets (excluding Peak)
estimated
(c) Street Watering (H.S.D's estimate)
(d) Side Channel Washing (H.S.D's estimate)
Total
59 million gallons per annum.
•
29
42 2
JJ
94.5 million gallons per annum or 260,000 gallons per day.
Savings can also be made if the fresh water flush scheme is adopted. I estimate that piping could be installed at an economic cost to give at least 130,000 gallons per day from the proposed fresh water scheme without recourse to pumping. The total fresh water supply required is therefore 245,000 gallons per day, the whole of which for an average of about 7 months in the year will be available from the streamcourses without pumping. The volume to be pumped daily during the 4 months dry weather period will vary from a few hundred gallons upwards.
The lowest D.W.F. gaugings are shown on plan of Health Districts and are as follows:-
J
9,331 gallons per day.
33,653
Stream at Point A
B
0
31
6,826
D
7,488
25
E
3,499
}}
F
>>
6,667
35
G
}}
3,300
J
H
>>
7,373
99
I
41,990
11
J
"
K
""
4,248 17,496
D
141,861 say 140,000 gallons per day.
No rain has fallen since the 19th January and gaugings which have again been taken at each of the above points show only a diminution of flow equal to 12% over an average of 20 days. From the above it will be seen that an additional supply of not more than 105,000 gallons per day will be required from some other source during the dry weather period to ensure an adequate supply for the whole of the residential areas on the north- ern slopes of the Island above the level of Pokfulam, Bonham, Caine and Kennedy Roads from the Chinese Christian Cemetery on Pokfulam Road to Mount Parish, excluding the Peak which is already supplied from the main.
Fortunately two other reliable sources are available which will continue to give an abundant supply. The first is in Shek Tong Tsui Nullah below Pokfulam Road and here it is proposed to utilise the water which drains into the nullah below the intake tank at the point marked A on plan and also the water which runs to waste from the condensers and pumping plant the result of slip on the high duty pumps of the Pokfulam Road Pump- ing Station.
The minimum available from these two sources, after allowing for a draw off of 50,000 gallons at the intake tank and 34.000 to be recovered by Waterworks is 43,000 and 33,000 gallons respectively giving a total of 76,000 gallons.
19
The second source is in the Albany Nullah just below the level of Bowen Road and here it is proposed to use the water which drains into the nullah below the intake tank at the point F on plan and also the water which is used for sand washings at the Bowen Road filter beds. The minimum available from the former source alone after allowing for a draw off of 38,000 gallons at the intake tank at F is 200,000 gallons. The former source has been checked and the returns show no diminution of flow.
At each of these 2 nullahs it is proposed that electrically driven pumps be installed to deliver, after filtration, such quantities to the high level tanks as the streams fail to supply during the dry weather period. The total available at all times in these two nul- lalis is not less than 282,000 gallons per day.
There remains the cost of the installation and the question of harbour pollution which I understand is now being reported on by the Government Analyst. As to the latter, it would appear that in the granting of water flush to a population of 19,200, the sewage discharging through the harbour frontage of about 3 miles would be considerably diluted and the increased pollution would be very small and practically negligible; about 20% of this population already possesses the flush system. As to the cost, no alterations or additions would be required to the existing sewer system and the total cost of carrying out the scheme including the necessary nullah intakes, tanks, balancing tanks, electric pumps, pump houses mains and fittings complete as shown in brown on plan would be approximately $178,500.00, details of which are given on page 19. To prevent waste I would suggest that all houses be put on water meters at a rate of say $1.00 per 1,000 gallons which no doubt all consumers would gladly pay for the privilege of the flush system. The adoption of the scheme based on a consumption of 115,000 gallons per day would give, after deducting working costs, a returri to Government of about 8% on capital outlay plus maintenance and depreciation charges. All houses above the level of 50 feet below the top water levels of tanks and reservoirs shown on plan are or can be supplied from streamcourses and have been taken into account with existing services in recording the dry weather flows.
Small intake Tanks generally of about 1 day's supply, break pressure and balancing tanks would be built in the positions indicated on plan together with any minor intakes to ensure full development of the whole of the polluted catchment area on the northern slope, not used for Waterworks purposes and bounded by the spur above I.L. 2378 Pok- fulam Road, High West, Victoria Peak, Victoria Gap, Mountain View, Mount Gough, Magazine Gap and Wanchai Gap.
The pumping mains shown green on plan would be of steel 5" in diameter and the chief distributing main shown on plan by heavy brown line would be 4 inches in diame- ter and the subsidiary mains shown brown 3" galvanized.
The houses on Stubbs Road in the Wongneichong catchment area East of Mount Parish are too widely scattered to be brought into the scheme; each must be treated on its merits in many cases water flush can only be granted subject to the owners providing 4 months capacity storage tanks, very few streams being available during the dry period.
The Ridge Broadwood Road and all houses in the vicinity up to the 400′ level can he provided for as shown on plan.
FRESH WATER SCHEME FOR MIDDLE LEVEL ZONE.
Approximate Estimates.
(A). Approximate cost of Pumps & Pump Houses,
1. at Pokfulam Road
2. at junction of Bowen Road and Garden Road
(B). 5" Steel Pumping Mains in duplicate,
2. at Albany 8,580,
.$12.000.00 12,000.00
1. at Shektongtsui 5.940 feet.
}
36,500.00
Carried forward
60,500.00
108
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