PARTICULARS OF WORKS PROPOSED TO BE CARRIED OUT TO MEET PRESENT REQUIREMENTS,
Storage Reservoir.-As good building stone does not appear to be abundant on the site of Reser voir No. 1, it is proposed to construct an earthen dam with central puddle wall on the lines of that at Pokfulam, a work which has proved very satisfactory and required little or no repairs. An earthen dam would probably be completed more quickly than one of masonry, and, the natural drainage ares being small, there need be no fear of injury from rainstorms during construction.
The dam will be 65 feet in height from top water level to the present stream bed. Its will be 10 feet above overflow level and 10 feet wide, the inside slope will be 3 to 1, protected by stone pitching, and outside slope 2 to 1, turfed. The puddle wall will be carried down in a trench to a solid foundation, and up to 3 feet above overflow level.
The overflow will be constructed of masonry and situated at the northern end of the dam. In will be so designed that, with a depth of three feet overflow it will discharge a rainfall of four inches an hour on the natural drainage area (152 acres) and 11⁄2 inch an hour on the area (400 acres) A masonry channel will which it is proposed should eventually be intercepted by catchwaters.
On the overflow conduct the overflow water clear of the toe of the dam and of the gauge basin. provision will be made for inserting planks, by means of which an additional two feet of water may The hill road, which be impounded in favourable seasons, as is now done at Tytam and Pokfulam. crosses the valley in the neighbourhood, will be diverted and carried across the overflow by means of a bridge.
The outlet works will consist of a culvert built in a trench excavated in the solid ground at the northern end of the dam, this will be connected to a valve tower containing the usual stand pipe and three outlet valves at different levels. A small bridge above top water level will give access to the
valve tower.
The lowest draw off will be 395 feet above Ordnance datum, top water level at the existing Yau-Ma-Ti service reservoir is 215 feet. Advantage will be taken of the ample head thus available to construct the gauge basin at such a distance below the dam as to intercept all probable leakage.
Catchwater.---The catchwater will be constructed to carry a rainfall of 14 inch an hour o the drainage area intercepted by it. This amount is seldom exceeded in dry years, and in wet years when the rainfall is excessive, the surplus will be carried away by suitable overflows. The bottom will be pitched with stone and a small cemented channel left at one side to carry the dry weather flow and prevent its loss by evaporation and leakage. The bank alongside the catchwater will be raised foot above the level of the overflows on straight lengths, and two feet where sand pits overflows o sharp bends occur. A connection will be provided from the catchwater to the gauge basin below the dam by means of a cast iron pipe, so that it may serve as a clearwater channel after times of heavy
rain.
Main to Filter Beds.-From the gauge basin below the dam the water will be conveyed to th Filter Beds by means of a 12-inch cast iron pipe laid along the hill side. This pipe when per will be capable of carrying 1,600,000 gallons a day, and will therefore serve for delivering the entir supply estimated to be obtainable when the whole of the sources described in the first portion of the report are made available. Near the Filter Beds a branch will be left for a future connection to Reservoi No. 2. All available streams will be intercepted en route.
Filter Beds.-The only suitable site for Filter Beds appears to be on a comparatively level spe north of the point where the new Taipó Road passes behind the hills above Cheung Sha Wan.
To filter 590,000 gallons a day-making the usual allowance for cleaning beds--an area of abou 1,300 square yards will be necessary, and in order to take advantage of the site in au economie manner the beds will be arranged at different levels, which can be done without undue loss of hend
A caretaker's bungalow will owing to the comparatively high level of the storage reservoir. required alongside the beds. If, on detailed surveys being made, the site is found to be large enoug it will be laid out with a view to the addition of further filter beds to deal with the water from th proposed reservoir on site No. 2. Should this, however, be found impracticable, a suitable site for the purpose must be found elsewhere.
Main to Service Reservoir-From the Filter Beds either a short tunnel will be driven through th ridge, or a pipe carried round it, as may be found the more economical when detailed surveys are mad and a 12′′ main will then be laid partly below and partly along the new Taipó Road and up the hi to the large service reservoir about to be described.
a
Service Reservoirs.-The existing service reservoirs are capable of containing only 250,000 gallons, quantity which has on several occasious been found inadequate to tide over a breakdown, and provision on a much more extensive scale for the storage of water after filtration is urgently required. There is no suitable site for a large service reservoir near the centre of the district to be served, and it has therefore been found necessary to select one on a hill to the north of the village of Kowloon Tong. The reservoir will be circular, 150 feet in diameter and 20 feet deep having a capacity of about
000 gallons.
190 At Kowloon City a small reservoir only, say 150,000 gallons capacity, will be required; it will be similar to the existing ones and situated on the hill above the walled city.
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Connection to existing Distribwion System.--From the Kowloon Tong service reservoir a 12′′ moin will be laid through Mong-Kok-Tsui to connect with the existing 7" main at Yau-Ma-Ti, and a main with 3" and 4" branches will supply Tai-Kok-Tsui and Sham-Shui-Po. On the eastern side of the Peninsula a 6" main will he carried along the now road to Kowloon City with 3" and 4" branch mains to the large villages of Too-Kwa-Wan and Ma-Tau-Wai All new mains will have hydrant- branches at distances of 300 feet apart where building is at all probable, and hydrants will be fixed in all built districts.
Fire Hydrants on existing system.In the original waterworks scheme fire hydrants were omitted, partly on account of the limited supply and partly because most of the houses were situated near the harbour.
When the proposed new supply is obtained fire hydrants should be fixed at intervals of about 300 feet on all mains in the built districts. Owing to reclamation works at Yau-Ma- Ti and Mong-Kok-Tsui the houses will soon be at such a distance from the harbour that little help could be obtained from it in case of fire.
ESTIMATE.
The following is an approximate estimate of the cost of the works described :---
Storage Reservoir,
Catchwater,
Main to Filter Beds,.........
Filter Beds and Bungalow,
Main from Filter Beds to Service Reservoir,
Service Reservoir at Kowloon Tong,
.$150,000
6,000
16,000
20,000
72,000
60,000
Connection to and extension of existing distributing system,
55,000
Service Reservoir at Kowloon City,
6,000
3,000
5,000
393,000
13,000
..$380,000
Fire hydrants on existing system, Purchase of cultivated ground,
Allow for value of machinery and pipes to be dispensed with,....................
Total,
To make a fair comparison between the cost of this and the cost of a pumping scheme such as that If this be hitherto existing, the annual expenditure on maintenance must be taken into account. capitalized at 5 per cent, we arrive at the following results :----
Supply, Orginal cost,
Existing Works.
232,000 gallons a day.
$ 128,000
Capitalized cost of maintenance, Cost of supply per million gallon per day,
Supply,
Proposed Gravitation Scheme.
Cost of existing works to be utilized, Estimated cost of new works, Estimated cost of maintenance (capitalized), Cost of supply per million gallon, per day,
$ 120,000 $1,070,000
590,000 gallons a day.
.$ 90,000
.$380,000
.$ 40,000
.$860,000