The water supply of Hong Kong being a report submitted to H. E. Sir Arthur E 1873

CSON. 3728 of 1873 13 CET 2/08 2

EASTERN 10936.2.

RECEIVE 21024

1874

74

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Despatch Ney of 8th January 187/4

THE

WATER SUPPLY

OF

HONG KONG

BEING

A REPORT SUBMITTED TO H.E. SIR ARTHUR E. KENNEDY, K.C.M.G., C.B.,

GOVERNOR OF HONGKONG.

 

DIE

SOIT

QUI MALTY

DROIT.

ET

MON

VICTORIA, HONGKONG:

PRINTED BY

NORONHA & SONS, GOVERNMENT PRINTERS.

1873.

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:

1

2

P

"

H

*

INDEX.

Page.

The Requirements of Hongkong, compared with past Works,

The Pokfoolum Triple Reservoir Project,

1

5

The Aberdeen Project,

8

The Tytam Project,

11

Comparative Merits of the three Projects,

The Tytam Reservoir and Outlet Works,

13

18

The Conduit,

Tunnels,

20

21

The Service Reservoir,

23

The Distributing Apparatus,..

24

Pokfoolum Subsidiary Works,

25

Method of increasing the Supply pending the completion of the Main Works,

26

On the Prevention of Waste,

27

Letters from Mr. RAWLINSON, C.E., C.B.,

29

Cost of the Waterworks of 1861 and 1871,....

32

Proposed Regulations to be embodied in a Local "Water Act,”

33

Estimates,

35

Comparison of the Projects in Tabulated Form,

73

PUBLIC WORKS DEPARTMENT, SURVEYOR GENERAL'S OFFICE, HONGKONG, 1st November, 1873.

The Honourable CECIL C. SMITH,

SIR,

Acting Colonial Secretary.

In accordance with the instructions of His Excellency the Governor that I should report upon the most practicable method of improving the water supply to the City with a view to increasing the allowance per head of inhabitant to a rate more in accordance with the wants of the people, I have the honour to state that I have closely examined the existing supply, thoroughly familiarizing myself with its defects, and that I have carefully surveyed the Island of Hongkong so as to determine the source whence an additional provision could best be obtained.

Hongkong being a small island devoid of rivers or large streams, the required supply is only to be derived from the drainage area of a sufficiently large valley in which a proportion of the yearly rainfall can be collected together into an impounding reservoir for use during the winter season when all natural sources are dried up.

The recent surveys were directed to the search of such a valley at as high an elevation above the level of the sea as possible, and I may add that my labours have been immensely simplified by the abrupt and uncompromising configuration of the island which confined them to the three only high level valleys in it, where it could be at all hoped to find a sufficient drainage area and a site for a reservoir.

These valleys are at POKFOOLUM, ABERDEEN, and Tytam.

Other valleys quite as large and nearer Victoria were first examined, but owing to the inadequacy of their height above the sea it was found impossible to draw off their drainage at an elevation sufficiently high to be of use to the upper or middle portions of the town; they have therefore been left out of the present question.

There are also many small nullahs or rivulets flowing down the mountain sides in the neighbourhood of the City, which for a few hours after heavy showers become torrents, but as many of them cease to exist in time of drought they are not, as a whole, reliable as sources of supply, and even if they were, there is no site on the northern slope of the island for an impounding reservoir wherein to store their contents. The works now proposed however, provide for their absorption into the new channel of supply and they will help at least to swell the volume of water which it is sought to bring into Victoria.

According to the Census of December, 1872, the population of the City is 93,000, but as out of this number the Garrison consisting of 1,200 is already sup- plied from the military nullah, the number of consumers to provide for becomes reduced to 91,800 or say 92,000.

Droughts lasting 240 days have been known in Hongkong, and therefore all calculations connected with a new water supply should be based on the assumption that they may recur. In such an event, the present supply would dwindle down to the following daily quantity per head of inhabitant:

From Pokfoolum main,

Glenealy nullah,

""

Wongneichung damn,

""

Mint dam,

99

99

Wells, springs, and other sources,

Total,

4.43* gallons. 0.50

0.25

""

0.10

""

0.50

""

5.78

"

* These 4.43 gallons are made up of 3.35 impounded rainwater, and 1.08 from the Pokfoolum and other nullahıs,

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This allowance of five and three-quarters gallons for every inhabitant is a quantity far below the necessities of a tropical City, in which a liberal supply of water is so essential to health and comfort, and so conducive to the improvement of the habits of the lower orders.

The modern water supplies of English and Continental Cities, where they have been designed to combine sufficiency with economy, due allowance being made for a moderate amount of waste, have been generally constructed to ensure an average of about twenty-two gallons, classified under the following uses:

GALLONS PER DAY. least. average. greatest.

Used for domestic purposes, Watering streets, extinguishing fires, &c., Special, trade, and sanitary purposes,

Total usefully consumed,.

Waste under careful regulation,.

7

10

15

3

3

3

7.

7

7

17

20

25

2

2

21/10

19

22

271/

Total demand,

Taken in combination with the present sources, there will be no difficulty in finding an unlimited daily provision for the people of Victoria during the six rainy months of the year, but during the remaining six, the utmost which the most extensive of the projects now proposed has been able to achieve is eighteen and a half gallons per head, and in order to accomplish this, it will be necessary to build a large reservoir in addition to the present small one, and to take in all the streams in the western half of the island and convert them into feeders.

Before proceeding to explain the nature of the works now proposed, it will not be uninteresting to recapitulate in a few words the efforts which have been from time to time made by the Colonial Government to supply the City with water, and the causes of the very partial success which has so far attended them, with a view to comparing past works with those now in contemplation, and from the comparison estimating the results which are likely to be attained if the present scheme be carried out in its integrity.

In 1860 Sir HERCULES ROBINSON writing to the DUKE OF NEWCASTLE, then Secretary of State for the Colonies, states that the poor had suffered greatly during the previous summer from the deficient supply of water in the town, and that he had accordingly offered a premium of $1,000 for the best and most prac- ticable scheme for providing Victoria with a constant and efficient supply of pure water.

In consequence, several schemes were sent in, and a Committee, consisting of the Surveyor General, the Officer Commanding the Royal Engineers, and a member of the mercantile community, having been appointed to consider and report upon the competing plans, the premium was awarded to Mr. RAWLING, a clerk in the Royal Engineer Department, who for a lump sum of $25,000 undertook to execute and complete, within two years, all necessary works.

These were to consist of a masonry dam 15 feet high across the Pokfoolum valley in order to head up the waters of a small stream so as to make a pond, and a ten inch cast iron pipe leading from the dam to Victoria along the line of the carriage road.

There were likewise to be two service tanks in the City with the necessary distribution pipes along the principal streets, and thirty stone water stands or hydrants at convenient places throughout the town.

All these works were satisfactorily completed in 1863 for the stipulated sum, their cost being defrayed and their maintenance provided for, by the levying of a tax on houses of 2 per cent per annum on the value of their rentals.

In the following two years, the works were somewhat extended, extra hydrants and mains being laid in new districts and paid for in the same manner.

In 1866, the population having increased to over 90,000, the discomfort of an inefficient water supply began once more to make itself felt, and for the first time the want of provision for the future in Mr. RAWLING'S design was ac- knowledged and regretted. The requirements of Hongkong had increased year

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by year with its population and commercial prosperity, but the waterworks as constructed had been final, and were therefore incapable of any further extension or addition.

The little pond at Pokfoolum was found to impound nothing; the utmost it could do in time of drought was to decant into the ten inch main the entire contents of the stream which fed it at the rate of one hundred thousand gallons per diem, or a little over one gallon for each inhabitant.

This state of things attracting the serious attention of the Legislature and the community, the general feeling prevailed that no half measures should be repeated and that in projecting any new scheme to improve the supply it should be such as to meet in the amplest manner the largest requirements of the Colony.

Bearing this in view, the Government concluded that a large impounding lake with a sufficiency of water to last throughout the dry season was a necessity and its efforts were directed to the attainment of this object.

Accordingly, in May, 1866, the Surveyor General proposed to raise Mr. RAWLING'S stone dam by 15 feet in order to increase the contents of the pond during the rainy season, a scheme the utility of which is not apparent, as it would have remedied the evil but very imperfectly. On closer inspection however the stone dam was fortunately found to show signs of weakness under a pressure of only ten feet of water and the proposal was therefore withdrawn.

Later on in the same year, the Surveyor General recommended the formation of an embankment 50 feet high across the Pokfoolum valley (on its present site) which according to his calculations would create a reservoir storing 100 million gallons for use during the dry season. SIR RICHARD MACDONNELL, who had per- sonally gone into the question very closely, at first viewed this scheme very coldly replying that the city required a reservoir containing 450 million gallons. Hav- ing however been professionally advised that a work of such magnitude was impracticable, the Governor was fain to ask Mr. WILSON to devise some means of impounding at least 200 million gallons.

Again the Surveyor General reported upon the impossibility of so large a storage in the Pokfoolum valley, and he added that even were it obtained, the ten inch main would be too small to convey the water to the City in sufficient volume.

Eventually, after much discussion and delay, the capacity of the proposed re- servoir was made subsidiary to the capacity of the ten inch pipe and a storage of 100 million gallons was acquiesced in by the Government. Elaborate detail plans and specifications of the proposed embankment, outlet culverts, and bye-wash were prepared in Hongkong, and sent to the EARL OF CARNARVON, then Secretary of State, and by his Lordship referred to Mr. RAWLINSON, one of the greatest living autho- rities on Hydraulic Engineering.

It is to be specially noted that Mr. RAWLINSON was never consulted on the question of a water supply to Victoria, or as to whether such a reservoir as the one proposed at Pokfoolum, would fulfil the requirements of the City. He was merely invited to inspect Mr. WILSON'S drawings of the proposed dam and its ad- juncts, and to express an opinion on their efficiency as to design and the disposition of the material. Had Mr. RAWLINSON'S attention been drawn to the general ques- tion, he would immediately have replied "100 million gallons will not suffice a City of ninety or a hundred thousand people for 240 days." But it does not appear to have been considered necessary by the Colonial Government to obtain Mr. RAWLINSON's views upon a question more of polity than of engineering science, nor indeed was there any occasion to do so, since it appears very plain that it had already made up its mind before the works were undertaken that they were to be expressly designed to contain 100 million gallons and no more, and since it further was quite as well aware that this volume of water divided among the inhabitants and husbanded so as to eke out until the close of the dry season would give each person a ration immensely short of the allowance usually provided for in the modern water supplies of European cities.

Nevertheless, the Government decided upon the expediency of carrying out the Pokfoolum works in the belief that they would afford a most important and material relief from the intolerable scarcity of water which then oppressed rich and poor alike. That the relief was very great indeed, there can be no doubt, and the Colony on the completion of the works gratefully acknowledged the boon, how- ever intense may be the dissatisfaction to-day which prevails at the paucity of the supply.

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In the beginning of 1867, LORD CARNARVON had returned to SIR RICHARD MACDONNELL Mr. WILSON's plans amended by Mr. RAWLINSON. The latter, in a very lucid Report on the subject, declared that the Pokfoolum works had been well planned, and if carefully executed would safely answer their intended purpose, that is to say, they would ensure a water-tight reservoir.

The necessary plant and machinery having been obtained from England, the new works were inaugurated, and the storage of the 100 million gallons bid fair to become a fact in two years' time.

In 1869, Mr. MOORSOM arrived in the Colony and took charge of the works. His first act was to submit a plan to reduce the capacity of the reservoir from 100 million to 67 million gallons.

At this stage, it becomes interesting to watch the process of depletion which the proposed water supply underwent at the hands of the various authorities con- nected with it between the years 1866 and 1869. Originally SIR RICHARD MAC- DONNELL had laid it down that the reservoir, to be of real utility, should contain at least 450 million gallons, but owing to Mr. WILSON's unfavourable Report he was reluctantly compelled to relinquish the idea and to reduce the figure to 200 millions.

In Mr. WILSON's hands this quantity got reduced to 100 millions, and the 100 millions were finally brought down to 67 millions by Mr. MOORSOM's rejection of his predecessor's scheme to excavate the bottom of the reservoir, a plan which would of course have increased its cubic capacity, but one which has always been considered questionable by hydraulic engineers as it incurs the danger of opening up springs and fissures in the substratum into which the water can filtrate and either escape harmlessly or else creep up under the seat of the dam, in which case uney/ the dam itself gets combed and is soon destroyed.

The proposed storage having dwindled down to 67 millions, it would have been thought incapable of further reduction, but in 1870, when the works were far advanced, SIR RICHARD MACDONNELL had occasion to call upon Colonel De BUTTS, Commanding Royal Engineer at this station, to give the Colony the benefit of his opinion "on the suitability of the works for the object intended, .e., that of provid- ing an abundant and constant supply of water to the City." Colonel DE BUTTS, after carefully inspecting the works, arrived at the conclusion that it was unnecessary to build up the dam as proposed to 50 feet and he expressed himself confident that the reservoir was too large for the wants of Victoria and strongly recommended the Government to discontinue the works at Pokfoolumn until his conclusions had been verified by practical experience.

How completely subsequent results have failed to justify this opinion may be inferred from the significant fact that only three years later the attention of the Government is being called to the advisability of securing a supplementary supply three times as large again as the one condemned by Colonel. DE BUTTS as too vast for Victoria.

In 1871 the new works were completed and were shortly afterwards severely tested by an excessively heavy flood. During this flood the greatest depth of water escaping over the bye-wash was discovered to be only two feet, and a dam three feet high was therefore built across the wash whereby an additional quantity of 7 million gallons was impounded, raising the total final storage of water in the new reservoir to 74 millions, or in other words, to nearly four and a half gallons per day for each inhabitant during a long dry season of 240 days.

So small an allowance has made it necessary ever since to practise the system of intermittent service, that is to say, to dole out the water to certain districts in succession during stated hours of the day and night, so that each may get its share.

The adoption of this system has compelled the greater portion of the inha- bitants to have cisterns or butts in their houses for the purpose of holding the daily store of water, and has in consequence given rise to very great waste, an evil which in spite of the best management seems inseparable from the "intermittent" method of supply. Pending the arrival of the water and in order to avoid delay in filling cisterns or butts, the taps are left open, and as often as not the cisterns are allowed to overflow and the water run to waste into gutters and neighbouring sewers. This is specially the case in districts where the supply is nocturnal, the inmates of houses being naturally indisposed to sit up, or to leave their beds to shut off the supply when their cisterns are filled.

A very considerable quantity of water is also allowed to run to waste through leaky and ill constructed fittings and also from carelessness and other causes.

In

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some English towns, it has been proved that a quantity of water equal to that used is wasted. In Hongkong, the abuse in this respect was until recently likewise very great, it has been partially checked, but it can only be reduced to a minimum by special legislation, and to this end I have framed the draft of an Ordinance which is appended to this Report; it is explained further on, and will, I think, meet the requirements of the case.

It will be seen from the foregoing remarks that the reason why the City still remains ill supplied is because the efforts of the Government have been limited rather to affording partial relief than to effecting a radical cure of the evil.

When it should have provided the population with a minimum of 15 gallons per day, it first made a pond to give them two gallons, and then did away with it in favour of a reservoir which during a long dry season cannot yield more than four and a half gallons per day, and the consummation of the two projects has cost the colonial exchequer nearly $400,000.*

These are truths which are not brought to light now for the sake of idle cri- ticism, but because a valuable lesson is to be learnt from them. After a lapse of seven years, a recurrence of the urgent public demand for more water has placed the Government and Legislature in exactly the same dilemma. in which the preced- ing administrations of 1860 and 1866 found themselves. It becomes worth while then to consider whether the experience of the past, has not sufficiently proved the futility of all palliative measures, and whether it should not decide the present Government, now that the opportunity occurs for the third time in the history of the Colony to grapple with the question in such a manner as to set it at rest per- manently. This it can only do by carrying out works that will yield, in combina- tion with the present ones, a supply as nearly equal to that of European cities as possible.

Undoubtedly such works will cost a very large sum of money, one much larger than any colonist is perhaps aware of. In England, the cost of water supplies is generally estimated at £4 per head of the population; although in a distant colony like Hongkong it would have been wise to assume that the same class of work would cost more, it has now been discovered that an effective water supply inay be accomplished for a price considerably below this, and as the colony, is solvent, its credit good, and water considered an urgent necessity by all classes of the community; I have no hesitation in recommending in spite of its magnitude, the outlay necessary to secure a constant supply of eighteen and a half gallons per head, during the longest droughts.

In all large colonial cities, when a question arises of such vital importance to the community as a water supply, it generally developes numberless conflicting schemes which cause great difficulty and retard the question at issue by long dis- cussions and investigations. In the case of Hongkong, the small area of the island and its very marked surface configuration limit exclusively to the number of three any reasonable projects by which the present supply might be increased.

In analysing these three projects consecutively, I shall endeavour to place be- fore the Governinent such a body of facts in connection with them as will enable it, from the evidence, to decide upon their correlative merits and to adopt the one which, in its opinion, will best meet the requirements of the Colony.

THE POKFOOLUM PROJECT.

Enough has been said about the Pokfoolum works to convince any body that no relief is to be got from them as they at present stand. The present reservoir impounds only 74 million gallons and is fed by a stream contributing only 100,000 gallons per day. If this volume of water were drawn off daily at the rate of 15 gallons per head, which is not an immoderate allowance, the reservoir would become completely dry in fifty-four days. It is exclusively owing to the smallness of the ten inch main that it is able to hold out during the season in the way it does.

Although the reservoir is perfectly water-tight and the dam very ably and solidly constructed, it would be dangerous to attempt to raise the latter as its top

* The Waterworks of 1861 cost $169,800, and those of 1871, completed by Mr. Moorsom, cost $223,270.

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width is insufficient. Under any circumstances, it could not be raised sufficiently to impound a supply for 240 days. If therefore the present reservoir is treated of at all in this enquiry, it must be in conjunction with supplementary works.

There is a site a little higher up in the same valley for a smaller basin, which according to the recent survey is capable of containing 50 million gallons. This would necessitate a dam 350 feet long and 90 feet high in the deepest part, and if the substratum turns out to be rock as appears from outward indications, such a dam might be built of masonry. The enormous expense of building a 90 foot damn to impound so small a quantity as 50 million gallons is altogether out of proportion; it is a measure therefore that could by no means be recommended until every possible mears of obtaining a supply by other methods had been attempted.

The site a little below the present reservoir has also been surveyed and found capable of holding a considerable sheet of water by the formation of a dam 55 feet high and 250 feet long, containing thirty-four thousand cubic yards of material.

This reservoir would unfortunately be very shallow, and it would be spread out over a great area, and therefore the loss of water by evaporation would be

excessive.

All water contained in ponds and reservoirs loses its purity relatively with its subsidence towards the bottom. The bottom layers are generally laden with vegetation and the lower forms of organic life either living or decomposed. In a shallow reservoir this is particularly the case, because the temperature of the water is increased by the rays of the sun which are able to penetrate to its bottom. I have calculated that one-sixth of the bulk of water of a low level reservoir at Pokfoolum would therefore scarcely be wholesome.

This capital defect, together with the equally serious one of loss by evaporation, must therefore be considered in forming an opinion as to the advisability of so shallow a basin. A reservoir on this site would further have to be surrounded on its south and west sides by long low embankments to protect the Aberdeen Road which would otherwise be under water for nearly a quarter of a mile. The outlet culvert through which the supply for the town would be drawn would be at an elevation of not more than 457 feet above the level of the sea.

The Pokfoolum scheme therefore provides for an upper and lower reservoir in addition to the middle or existing one. The total storage of water in the three basins would be as follows:

Upper,

Middle (actual reservoir), Lower,

Total gallons,......

50 millions.

74 60

""

184 "7

The next question to consider is whether the drainage of the valley above is sufficient to fill the three compartments during seasons of small rainfall. The Pokfoolum water shed comprises 400 statute acres, the rainfall of the dryest year in Hongkong is 50 inches; by the ordinary computation it results that the least drainage will be 450 million gallons.

In estimating the proportion of rainfall which may be depended upon for storage, a considerable reduction must be made for losses by evaporation and absorption by the soil. These losses vary in all countries according to the climate and geological nature of the substratum. In Hongkong, they may be safely averaged at 60 per cent, for although evaporation is excessive, absorption is com- mensurately small, owing to the granite formation of the island. Upon this basis, the Pokfoolum drainage available for storage will be 180 million gallons, a volume barely sufficient to fill the triple reservoir during seasons of small rainfall. It would therefore be necesary to increase the drainage of the valley so as to place it beyond the possibility of failure. This could easily be done by making catchwater channels along the hill sides to the north and south of the valley and diverting the drainage of the neighbouring hills into any one of the three reservoirs.

The water connections between the three basins would be simple. The upper dam if it can be constructed of masonry would contain its own bye-wash. The upper basin would empty its contents into the middle one along the channel of the present stream by the ordinary method of a valve well, and the middle

*

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7

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basin would discharge itself into the lower one by means of the outlet from which the present supply to the town is drawn. Thus a regular and uniform subsidence of level could be at all times maintained in the waters of the three compartments.

In the lower dam, all the appendages of a store reservoir such as bye-wash, valve well, and outlet culvert would have to be for a third time repeated, and a conduit of brick or stone laid in cement covered with granite slabs would have to be built along the hill sides to convey the water by gravitation from the outlet mouth into Victoria. This conduit would be three and a half miles long and it should have an inclination or fall of four feet per mile, or a total fall of fourteen feet. It should terminate in a tank or service reservoir at a convenient site in town with sufficient elevation to maintain due pressure in the mains and distributing apparatus.

It must be borne in mind that the Pokfoolum project necessarily transfers the supply from the middle or actual reservoir to the lower one and that this transfer entails a loss of 43 feet in elevation in the delivery.

This is unfortunate, as there are houses in Victoria which from their position would be too high to avail themselves of the new supply. The only way to remedy the evil would be to leave the ten inch main pipe in its present position and utilize it to supply directly from the middle reservoir all that portion of the town which would be above the reach of the new conduit and service tank. It would not compensate to repeat a second masonry conduit at a higher level for so small a service.

The leading features of the Pokfoolum project having been cursorily described, its merits and defects may be summed up in a very few words.

While the necessities of the city during long droughts exact a minimum of 330 million gallons, the triple reservoir could only yield 184 millions.

This quantity, divided among the population, would afford an allowance only of eight gallons per day. This allowance could however be increased to nine gallons by the absorption of the nullahs between Pokfoolum and Victoria which the conduit would intercept.

The project is incapable of further enlargement or extension, owing to the steep slope of the valley, which does not admit of a repetition of reservoirs in steps higher up and to the inability of its drainage area to fill more basins. The upper basin could only be formed by a height of damn entailing an outlay totally disproportionate to the small number of gallons to be impounded by it.

The lower basin, containing 60 million gallons, would be very shoal, ac- cordingly the loss by evaporation would be excessive. The constant temperature of the water would be high, and its purity towards the end of the dry season questionable. The lowest layer of ten feet containing 10 million gallons would therefore scarcely be available.

The cost of iron pipes having become exorbitant, it had been contemplated whenever new works superseded its use to take up the three miles of 10 inch main between Pokfoolum and Victoria and to utilize it in the distribution of the new supply through the streets. The insufficient elevation of the outlet at the lower basin however demands, if the Pokfoolum project be adopted, that the main should remain untouched. It would therefore be unavailable for dis- tributing purposes and the loss is no trifling one because it would entail the purchase of new pipes for the streets.

In favour of the project, taken as a whole, it may be said that it can be realized at a cost considerably below that of any other feasible scheme.

It likewise is able to afford a water delivery at a level of 446 feet above the sea, which is a higher elevation than can be derived from any other valley in the island and the short distance of its source from town reduces the length of conduit to three and a half miles. Consequently, the yearly cost of maintenance would be reduced in proportion, but the multiplication of dams which a triple storage would entail, and the increased cost of keeping up three sets of works would perhaps outweigh this advantage.

Reservoir making," Mr. RAWLINSON states in his letter of the 29th of May, addressed to the Crown Agents for the Colonies, "is a difficult operation on any site "and under any estimate, but the operation will be specially difficult at Hongkong."

The operation is difficult because the construction of high embankments has to be carried out with the utmost care and caution. The penalty of failure is most appalling, the chances being in favour of the total annihilation of a dam the moment that the smallest leakage has established itself through its heart or

1

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between it and its foundations. Earthen dams have before now been destroyed in this manner with so little warning and with such fatal rapidity as to cause serious loss of life and property.

A dam properly and soundly constructed may in the course of years, if ne- glected, deteriorate and become defective, in which case of course the risk of its bursting will be the same as that which attends structures improperly built.

Bearing these eventualities in mind it is most desirable to select, if possible, a project with a single dam so as to reduce to a minimum the possibilities of failure. The Pokfoolum project entails two new dams besides the present one, and both these may perhaps have to be earth embankments. The stability of the third or actual dam might or might not be affected by the radical change which the springs and subterranean drainage of the Pokfoolum valley would undergo if so large a portion of it as the project necessitates were placed under

water.

All these are considerations to be carefully weighed in dealing with the Pokfoolum project.

5/

THE ABERDEEN PROJECT.

A little above the village of Aberdeen to the right of the bridle path which leads over the mountains to Victoria, there is a large valley possessing an area of nearly 600 statute acres. This valley is flanked by precipitous hills narrowing towards a gorge 500 feet wide, in which is an admirable site for a dam.

Nearly every condition for the formation of a store reservoir which had been so fruitlessly sought for in the narrow and contracted valley of Pokfoolum, would appear at first sight to be here fulfilled. Its great natural basin seemed as it were expressly shaped to afford every facility for the easy realization of an abundant water provision, and the configuration of the upper valley ap- peared equally favourable for a small subsidiary reservoir had such been required; at the back of this again, were hills stretching out to a height of nearly 1,500 feet, promising a rain drainage in excess of the requirements of Victoria.

Issuing fresh from the difficulties which had beset the preceding surveys at Pokfoolum, and the questionable expedient of a triple reservoir, which had to be resorted to in order to devise a water supply however scant, the marked contrast presented by the generous dimensions of the Aberdeen valley could not but be a gratifying sight.

On closer examination however, the bed of the valley scarcely appeared to have a sufficiently high elevation to provide water to the higher portions of the

town.

The subsequent surveys were productive of the most disappointing results, for although it was proved that the formation of an inland lake of twenty-two acres was perfectly feasible, it was also discovered that the exit of the water could not be effected at a greater elevation than 240 feet above mean sea level. Aberdeen water, if brought by gravitation into town, could therefore only serve those districts below that level.

At the conferences on the subject of the Hongkong Water Supply, held in London at Mr. RAWLINSON'S office, in April last, the question of a store reservoir in the Aberdeen valley was mooted and discussed. It was at the time inferred from the contour lines in the Ordnance map that the outlet could have been made on the 200 foot datum; and my predecessor, Mr. MOORSOM, in a memo- randum on the capabilities of this valley dealing with the conveyance of the water to the city, suggested two ways of effecting it, viz.: either by force pumping it through cast iron pipes into the reservoir at Pokfoolum so as to insure a high level delivery, or else by tunnelling a channel under the Aberdeen hills direct into the city.

With regard to the first of these suggestions, I must at the outset deprecate on the score of economy any scheme entailing the establishment of steam pumping machinery for Hongkong.

The first cost of engines and pumps capable of lifting the volume required to a height of 300 feet, of boiler houses and engine buildings, and of cast iron 24 inch mains leading from Aberdeen up to the Pokfoolum reservoir, a distance of two and a quarter miles, would be very great. But it is by no means to the first cost in founding works of this kind that there is so great an objection as to the continued yearly expenditure which they would involve. This expenditure

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in the item of coal alone would from present appearances bid fair to increase yearly until it had in the future attained proportions so considerable as to make it a sure matter of regret that such a scheme had ever been embarked in. Again the repeated cost of renewing the 24 inch cast iron mains would be equally serious.

Considering the present revolutionized state of the coal and iron markets, and the certainty that there can be no permanent reduction in their quotations owing to the great changes which the past few years have worked in the condition and aspirations of the labouring classes in England, those who can, should endeavour to do with as little coal or iron as possible. This rule should specially apply to Hongkong which is so far removed from the great marts where these two articles are dispensed that in order to acquire and utilize them, a second expense that of transport, equally great, has to be met.

Based on the prices of to-day, but which may be totally inadequate for to- morrow, the approximate cost of pumping water from a proposed reservoir at Aberdeen into the present one at Pokfoolum would be twenty-five dollars per diem. During July and August the rainfall in Hongkong is so great that it would be quite possible for Pokfoolum to keep up the supply unaided by Aberdeen; therefore, I do not suppose that it would be necessary to pump more than about three hundred days in the year, but even so the expense of the operation would not be less than $7,500 per annum, and this does not include the cost of wear and tear and incidental repairs to machinery but merely refers to labour and fuel.

In Victoria, where the best skilled labour is not always available, and where the appliances for keeping up a steam pumping establishment in thorough working order are not to be counted upon, it would be rash to rely upon intricate me- chanical contrivances and perishable iron pipes for a regular daily water supply so long as there existed as an alternative any feasible scheme upon which to fall back for obtaining the same by the natural law of gravitation in imperishable masonry conduits. In the one case, a first investment and a never ending yearly expenditure to follow are entailed upon the colony; in the second, a first cost only, for if the works are solidly built from the beginning the yearly expense of maintenance need not be more than nominal.

Conduits built by the Romans in ancient Italy and Spain are not only extant but in use. Their long life is due to the excellence of the material with which they were originally constructed, and there is every reason to believe that the excellent building material so abundant in Hongkong laid in any of the modern English hydraulic cements would form equally durable structures.

With regard to the second proposal, i. e., that of a straight tunnel conduit under the Aberdeen hills direct to the city, I should repeat by way of explanation that it was likewise based on the assumption that the outlet could be made as high

5/ as 300 feet, and therefore the tunnel was meant to be at that datum, but as it has

since been proved that the exit could not be effected so high by sixty feet, a tunnel would necessarily have to be lowered in the same ratio; this change of site would increase its length from 2,200 to 2,400 yards.

There would be no difficulty whatsoever connected with a work of this kind that could not be easily overcome at a comparatively moderate expense, although perhaps some might urge as a drawback against it the necessarily long time that it would take to complete.

The main objection to it however lies in the fact that we have every need to work on the surface of the ground and not under it in order to increase the volume of supply, for we must not limit ourselves merely to conveying into the city the impounded drainage of valleys, or in other words the contents of store reservoirs, but we should likewise try to intercept and utilize every available. drop of the drainage of intermediate hill ranges in which no sites for reservoirs exist. This is only to be done by means of masonry conduits built along the hill slopes.

For five or six months in the year the reservoir water travelling towards Victoria through these masonry surface channels could not progress any distance. forward without being reinforced along the whole line of road by the contents of nullahs, rills, or springs; thus before the end of the journey an aggregate supplementary supply would be picked up on the way of no mean proportions. During the height of the rainy season no conduit could have sufficiently con- venient dimensions to contain the torrent that would endeavour to pour into it in this way, and it would be necessary to guard against this embarras de richesse by contrivances providing the most ample overflow.

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The advantage of so valuable a subsidiary supply for five months of the year from hill side drainage as the one just described would be lost by the adoption of a subterranean conduit from the water source to the city, since no tributaries or feeders could have access to it. A continuous tunnel throughout would not therefore be advisable, however much it might shorten the route and cheapen the cost of the work.

A dam at Aberdeen 90 feet high in its deepest part and 520 feet long would form an impounding reservoir containing 213 million gallons. This quantity gives 94 gallons per day and together with the present Pokfoolum supply, would make a total storage of 287 million gallons, or a total daily allowance of 14 gallons per head for a long drought of 240 days.*

The area of the gathering ground above the reservoir site is 600 acres yielding in years of the smallest rainfall, say 50 inches, a drainage of 680 million. gallons, which after a deduction of sixty per cent for percolation into the ground and evaporation would leave a balance of 270 million gallons, or more than enough by 57 millions to fill the reservoir. A stream giving approximately 100,000 gallons per day flows down the valley all the year round, and there are likewise two sinall perennial nullahs which would be of some help in replenishing the volume of store water after all rain drainage had ceased.

Owing to the very low site of its outlet culvert and its consequent inability to accommodate the upper town, the Aberdeen project, if adopted, would ne- cessitate two distinct sets of waterworks, one as totally independent of the other as would be two rival water companies in England. Those parts of Victoria lying above the outlet level would have to be fed from Pokfoolum by a high level conduit leading from that place into a high level service reservoir in town holding a three days' supply, while the lower town would have to be provided for by a low level conduit from Aberdeen leading into a low level service re- servoir also to contain a three days' supply and to be built at some convenient site on the 200 feet level in the centre of the city. The line of demarcation between the two water services would be a little below the level of the Bonham and Caine Roads and Government House grounds.

During five months in the year the store water flowing through the pa- rallel conduits would receive on its way, the addition of the surface drainage of the mountains lying between their sources and their termini; during the re- maining seven months these accidental supplies would only be sufficient to benefit one conduit and that meagrely.

It must be acknowledged that the disadvantages and inconvenience entailed by double works of this nature would be very great. They would complicate the distribution through the town, and would entail the outlay of two service reservoirs. In order to acquire a site for the lower one, it would be necessary to purchase ground in one of the most populous parts of the city where property is very dear.

The conveyance of the last mile and a quarter of the Aberdeen supply would have to be made in cast iron 24 inch mains as it would be highly injudicious to expose it to the chances of pollution by the percolation of town drainage, and indeed, at intervals along its whole length precautions would have to be taken to make the cover of the conduit impervious to the filtration of sewage irrigation and other impurities, for its low level would compel it to pass through many frequented places and occasionally below the level of cultivated patches of land. Between Aberdeen and Mount Davis the declivity of the hill sides is so un- usually steep that it would not be possible to obtain a permanent foothold for a masonry conduit throughout, and it would therefore be necessary to revert to cast iron mains deeply buried in the ground for the conveyance of the water along a disjointed length of 2,670 yards, or a little over a mile and a half. In four places the turns of the contour line are so sharp as to render it necessary in cach case to have a short tunnel to cut off corners. In none of the surveys

hitherto made have the slopes of the mountains been found so steep as in this part of the island. In some places they almost resemble the side of a wall and it is this unfavourable configuration of the ground which would make it a matter of increased expense to lodge a safe foundation even for iron piping.

* These 14 gallons would be increased to 15 gallons by the extra gallon collected from the three large nullahs which the conduit would intercept between Aberdeen and Pokfoolum.

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But it is mainly the inadequate height of delivery which so seriously detracts from any advantage that a water supply from Aberdeen might possess. It makes the project like the Pokfoolum one rank as an alternative plan, to be reverted to only when every possible hope of something better has been found impracticable.

THE TYTAM PROJECT.

The next valley eastward of Aberdeen is that of Wong-nei-chung, on the northern slope of the island; it is perhaps more familiarly known as the Happy- Valley. Its drainage area is only 360 acres, or 40 less than Pokfoolum, and it does not possess, like the latter, any favourable site for a reservoir however small at a sufficiently high elevation to be of service.

The inspection of Wong-nei-chung brought the surveys of the valleys of the western half of Hongkong to a close with the most discouraging results. It now became apparent that if water must be had * it would be necessary to seek it somewhere in the eastern end of the colony far away from the city. The topo- graphy of the eastern districts is if anything wilder and more abrupt than that of the western ones. East of a meridian drawn from Aberdeen to Wong-nei- chung there is but one valley worthy of the name, this is at Tytam and it contains by far the largest watershed in the colony. The Tytam stream which flows down this valley discharges itself into the sea at the little village of Tytam Took and contains a very large volume of water even during the dryest season of the year.

I had no hesitation in recommending the Tytam valley to Mr. RAWLINSON as the probable site for a future reservoir, the more so as Mr. MOORSOM was of opinion that its outlet culvert was feasible at as high an elevation as 500 feet.

The recent investigations have however shown that it is not possible to effect the exit of the water higher than 400 feet; this is no doubt a great re- duction, but one which does not so seriously detract from the merits of the scheme as to entail (as in the case of the Aberdeen project) the necessity of two sets of works, for it so happens that there are only twenty houses in the whole City of Victoria situated above the 400 foot level, and arrangements could easily be made to supply these from the present Pokfoolum reservoir, the outlet of which is on the 500 foot datum.

In the treatment of the two preceding projects I have endeavoured to shadow out their leading features as clearly as lay in my power, omitting no fact con- nected with them favourable or unfavourable, from which the Government could draw a deduction on their comparative merits or demerits. I have therefore had to criticize adversely, and it may with truth be said that so far I have suc- ceeded in developing and elaborating schemes only to destroy them in the end by the exposure of the gravest defects.

Against the Tytam project however I have no word of disparagement. It may have defects, but these are not cardinal. Having said this much it may be asked why I did not come direct to it without going through the process of reviewing the Pokfoolum and Aberdeen ones? I would reply that the recent surveys having revealed but three valleys in the whole island where complete engineering designs for works to provide a city with water were at all feasible, it was not deemed inconsistent with the wide and general purport of this Report to touch upon the two first, explaining upon what basis any such works however inadequate or defective might be established before proceeding to deal with the third and last, because by a disclosure of the difficulties which beset the ga- thering, storing, and conveyance of water at Pokfoolum and Aberdeen, it was thought that the Government would be all the better able to appreciate the greater facilities of the Tytam valley to meet the requirements of the city.

Had the surveys of 1860 and 1866 been as comprehensive, and the capabilities of the different valleys of the island been as thoroughly brought to light as they have been in this instance, it is possible that different conclusions might have been arrived at by Sir HERCULES ROBINSON, and Sir R. MACDONNELL and that the community would not be in its present extremity for a common necessary of life. Indeed with regard to the surveys of 1866, when Sir R. MACDONNELL Was aspiring to a reservoir of 450 million gallous, it is almost certain that had the

*The search when I first undertook the survey was for 22 gallons per head of population.

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search been extended beyond the walls of the narrow valley of Pokfoolum, the people would have been spared the seven years of dearth and discomfort that have ensued, the more so as the subject of a generous water supply was in those days a very popular one, and the colony having attained a degree of commercial prosperity unprecedented in its history, had never been more ready and better able to bear the burthen of so great an outlay as that necessarily entailed by hydraulic works.

Before leaving this topic, I may venture to state that the question so far as concerns the Public Works Department has this time been properly ventilated and thoroughly exhausted. It was approached with the full resolve to embrace the whole length and breadth of the colony in the surveys begun at Wong-nei-chung and had there been need for it, to push these on as far as Cape D'Aguilar, its eastern extremity. No untrodden ground has now been left behind, and there is therefore nothing left to discover. Consequently a recurrence is impossible in the future, of the thankless task which has fallen to my lot: that of condemning the work and efforts of the past, and pointing out new and unexplored sources whence the city if it had only known and chosen to avail itself of them could have long ago derived a supply more in accordance with its wants.

The Tytam valley has a gathering ground of 700 acres, yielding in years of the smallest rainfall (50 inches) a drainage of 790 million gallons, which after a deduction of sixty per cent for losses by percolation, absorption, and evaporation leaves an available balance of 316 million gallons for storage during the dry season.

On the 400 foot datum the great three pronged basin of the valley suddenly contracts and forms a defile about 400 feet narrow with very precipitous sides. In the defile is an excellent site for a dam, which if built 90 feet high will form a lake twenty-three acres in extent containing 250 million gallons. After the termination of the periodical rains when drainage supplies cease, this lake would continue to be fed throughout the longest dry season by three perennial streams which would flow into it and which have been calculated to yield 130,000, 30,000 and 5,000 gallons respectively, or an aggregate of 165,000 gallons per diem:

The impounded water in the reservoir alone would afford an allowance of 11.32 gallons per day per head of population for 240 days, and taken in conjunc- tion with the 4.43 gallons derived from Pokfoolum, the total daily allowance of stored water during the dry season would be 15.75 gallons per head.

To this must be added the supplies from nullahs flowing into the conduit which estimated at a very low figure will average a minimum of 200,000 gallons per day or a total of nearly 50 million gallons during a drought of 240 days, or in other words a daily dividend of two and a quarter gallons for 92,000 souls. The future supply would therefore stand thus:-

Daily allowance.

Sources.

From Tytam reservoir,

11.32 gallons.

Pokfoolum reservoir,

4.43

"7

""

Nullahs flowing into the conduits,

2.25

""

Mint dam and other actual subsidiary supplies,*

0.50

17

""

A

1

Total,

18.50 "7

The bye-wash which is one of the most important and expensive adjuncts of a store reservoir need not in Tytam be tunnelled through the hills, or as in the case of Pokfoolumn be carved out of the solid rock. Nature has already done the work for us. A few feet below the level of the top of the proposed dam a small glen 180 feet wide, at present occupied by paddy fields juts out of the valley to a distance of 300 yards, making an admirable overflow channel capable of discharg- ing the greatest flood that a tropical rain storm could hurl down the valley. The only works necessary to utilize it will be a dwarf wall thrown across its mouth to prevent scour and a rough stone stepping outside, to break the fall of the water as it is escaping.

The outlet, as before stated, is feasible at an elevation of 400 feet and it is proposed to tunnel it on one side, through the solid hill, so as not to interfere with the earthen dam which should be one great compact and solid mass of concrete, puddle, and selected earth, unbroached or weakened by pipe or culvert per- forations of any kind or description whatsoever. The embankment would contain

* These supplies are: from the Mint dam, 0.25 gallons, and one half of the present Wong-nei-chung supply which drains off the north-eastern hills, 0.25 gallons; Total 0.50 gallons.

K

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300,000 cubic yards, it would be eighty-six feet high from the lowest point or bed of the stream up to the top water level, and four feet above that again up to "forma- tion level" which would finish with a width of twenty feet. The gorge is so deep and so narrow across that the 90 foot height of the dam would not be for more than twenty feet of its length. The banks on each side of the stream rise most abruptly, almost at an inclination of one foot vertical to one and a half foot horizontal. It is only owing to the enormous bye-wash space, 180 feet, with which nature has accomodated the site, and which it is in no way desirable to curtail or contract that so small a height of dam as 4 feet above top water level has been suggested.

The water should be drawn out of the reservoir through a masonry tower lined inside with cast iron containing two compartments one charged and the other empty divided by a partition, valved at every ten feet vertically as in the present Pokfoolum works. Once liberated through the top valve the water would pass out through the heading into a small masonry cistern forming the head or fountain. of the conduit, from thence it would overflow through a meter into the latter and wend its way to Victoria a distance of nearly six and a quarter miles.

The water starting from its source at Tytam on the 400 foot datum and dropping 4 feet per mile would be able to empty itself into a service reservoir in town at a height of 375 feet. It. would skirt along the hill sides cutting off sharp curves by short headings or tunnels and crossing ravines not by aqueducts which would be very expensive, but by means of inverted syphons or cast iron mains securely bedded under ground. Under no consideration would it be advisable to build the conduit on artificial embankments, such a step would incur the risk of the whole structure being swept away by the deluging falls of rain which, as described by Mr. RAWLINSON, "shoot off the mountain sides as off a slated house roof." It is a fortunate circumstance that the hill slopes along the route are not nearly so steep as those along the Aberdeen heights, if they were, the conveyance of the water would have to be effected for a great part of the way in cast iron mains to the great increase of the estimate. As it is, there are short sections where some piping will be indispensable in the Tytam project, but their aggregate length will not be more than one mile.

It should be borne in mind that the drainage system of Tytam, like that of Aberdeen, flows down the southern slope and empties itself into the sea on the southern coast, there is therefore a dividing ridge of mountains lying between it and the city forming the backbone of the island which it will be necessary to pierce in order to give the water access to the northern slope on which Victoria is situated. As there is no way of going round this obstacle there is no help but to go through it.

The shortest site for a tunnel for this purpose has been carefully surveyed and selected, it is under the lowest depression of the dividing ridge and its length is 650 yards.

The conduit would therefore on reaching the head of Deep Water valley dive into the mountain and only issue out again into light at the head of the Wong- nei-chung valley, whence it would continue along the northern slopes in the manner already described till it reached its terminus above the city.

The foregoing is a cursory summary of the proposed Tytam works and what they can do for the colony, and it may not be uninteresting to compare them in somewhat closer detail with the advantages promised by the two preceding al- ternative schemes, which are the only ones, if the Tytam be not adopted, upon which to fall back.

THE PROJECTS COMPARED.

From the foregoing it will be seen that while the Tytam reservoir will yield 11.32 gallons per head daily during droughts of 240 days, the Aberdeen one can only be depended upon for 9.64, and the Pokfoolumn triple reservoir for 8 gallons.

These quantities refer only to stored rain water and are, as pre- viously explained, capable of increase by additional supplies from nullahs and the drainage of hill ranges in the following approximate proportions: Tytam two and a quarter gallons, Aberdeen one gallon, and Pokfoolum one gallon daily. The Tytam conduit would intercept and absorb twenty-five nullahs, the Pokfoolum conduit twelve, and the Aberdeen one only three. The small number of feeders

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to the latter is accounted for by the fact of its having for the greater part of the way a conduit * running parallel to it somewhat higher up the hill cutting off all supplies; also the conveyance of Aberdeen water having to be effected for a long distance in pipes greatly debars it from the advantage of taking in way-

side contributions.

The length of the Tytam conduit from its reservoir to a proposed service tank in the city would be six miles and a quarter, that of the Aberdeen one six miles, and that of the Pokfoolum one three and a half miles. There is therefore a difference of only one quarter of a mile in the lengths of the first and second, whereas the third is shorter by nearly half.

This excess of one quarter mile in the Tytam line over the Aberdeen one is compensated for by its proportionately increased ability to collect more lateral hill side drainage. It is true that during the dry season this drainage will be very little, but during the five rainy months of the year, the surface waters caught by even one quarter of a mile of channel will be considerable.

The Tytam line involves only one mile of cast iron pipes to be used as syphons for crossing ravines, the Aberdeen line owing to the very unfavourable country it would have to traverse requires two and three quarter miles for the same purpose, and also to secure a foothold in the ground, and the Pokfoolum line can do with only two thirds of a mile of piping for occasional steep places. In this respect therefore Tytam has the better of Aberdeen though not the better of Pokfoolum.

In the matter of tunnels certainly the Aberdeen line has the advantage of the Tytam one for it has not got to pierce the dividing ridge of the island to force a way into Victoria, but it is not itself by any means free of subterranean works. The Tytam line entails seven tunnels with an aggregate length of 1,883 yards, the Aberdeen line four tunnels with 1,366 yards, and the Pokfoolum line two tunnels with 633 yards. Comparing the first with the second the Aberdeen tunnels are shorter by 517 lineal yards, an advantage which may be placed to the credit of the Aberdeen project as a slight set off against its excess of the one and three quarter miles of iron pipes. In this comparison the Pokfoolum project again asserts its superiority with a length of underground work less than half that of its two competitors.

Victoria is built in terraces upon the sides of very steep hills. It may be compared to a huge staircase, its bottom step being on the sea shore and its top landing somewhere in the region of the 500 foot contour. The most perfect water supply would be that which could effect a delivery on the top step, so as to let the water run down and disseminate all over the City by its own gravity; but none of the projects now under consideration can achieve this. The scanty one of Pokfoolum whose outlet at the triple reservoir would be 460 feet high, and its delivery 446 feet comes nearest the mark, the next highest is the Tytam one with its generous volume of water available at 375 feet, and far away below these two follows the Aberdeen one as low as 216 feet, leaving one third of the city above it unprovided for.

This is the prime defect of the Aberdeen project, and the one of all others inclining one to look for the bulk of water required, to Tytam aided by a high level conduit along the 500 foot contour leading in from the present small reservoir at Pokfoolum to accomodate the top step of the city. The overflow from such a conduit would of course amalgamate in the proposed service tank in town with the Tytam supply which it would help materially to increase.

Having no further comparisons of any great importance to make, I will simply proceed to the most interesting point connected with the question and state that the Pokfoolum, Aberdeen, and Tytam projects will cost respectively £201,540, £250,056, and £259,479.

I need scarcely state that these are only approximate estimates, since the studies upon which they are framed were only preliminary ones. In order to arrive at the correct cube and precise cost of earthworks and masonry it would be necessary for a regularly organized engineering party to take the field and make not only detailed surveys and cross sections of the ground but also borings or trial pits to ascertain the geological nature of the substrata in the foundations of the proposed dams, conduits, service reservoir, etc.

To defray the expenses of a complete and detailed survey the Government

* This conduit independently of any new works in contemplation either at Aberdeen or Tytam should be carried out

in substitution of the present inadequate 10 inch main which supplies the City.

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should devote a sum of not less than two thousand dollars, and it should direct the studies to be made leisurely and minutely.

I confess that it becomes a matter of some difficulty to point out how, under existing circumstances, such a survey could be effected, for there is no Royal Engineer or other professional person in the colony at present whose services are available.

It is unfortunate that the Department over which I have the honour to preside should be so constitutionally weak as to be incapable of undertaking the work. Since the withdrawal from the Surveyor General's staff of Lieutenant GOSSET, R.E., and Mr. ALFORD, I have been left without a single officer conversant with egineering field work, and however desirous I might be of conducting per- sonally so important an investigation as the one now proposed, I could not well do so without closing my office for a considerable time, to the interruption of official business, and to the detriment of the public service.

I avail myself of this opportunity to state in explanation of the long time, (nearly three months) which has intervened between the beginning and the com- pletion of the preliminary surveys recently closed, that owing to the press of ordinary departmental work, I was only able to prosecute them at long and ir- regular intervals, and that I have only been able to work out and condense the calculations and data acquired into the form they now present, in occasional moments of leisure snatched from the most active professional pursuits.

It would not however be desirable to undertake a detailed survey in this unsatisfactory manner, as it would be certain to become protracted over an in- terminably long space of time, and as it might also lose much of its value and accuracy from the constant and disheartening interruptions and calls diverting the attention of the engineer engaged upon it to other duties.

In estimating for water supplies to cities, it is usual to assume an ordinary allowance, generally of 20 gallons per head, and to calculate the costs of the works necessary to provide this allowance at a certain fixed sum or rate per inhabitant.

Mr. RAWLINSON gives it as his experience that in England the price varies from £3 to £5. I do not suppose that there is an engineer living able to form a more accurate opinion upon this subject than Mr. RAWLINSON, and we might therefore confidently guage the present estimates by his standard of prices in order to test their economy and to ascertain how they compare with the cost of works at home. The maximum estimate, on a European scale at £5 per head for works in Hongkong, would be £460,000, the minimum one at £3 per head £276,000. The fairest sum to adopt as a standard of comparison would be the mean between these two, viz., £368,000.

Not one of the Projects described, entails an expenditure per se approaching such a figure, although it must be borne in mind that if either the Tytam or Aberdeen one are adopted, their ultimate cost would be increased by the ad- ditional one of a subsidiary conduit from the present Pokfoolum reservoir to replace the old inadequate pipe. An estimate of this separate work amounting to £42,668 is given in appendix D, it swells the final cost of complete and efficient water- works in connection with Tytam to £302,147, and in connection with Aberdeen to £292,724.

The Pokfoolum project would not entail the construction of a conduit from the present reservoir, since it would be provided with one already on a somewhat lower site, supplying the city from its lower or third basin.

Notwithstanding the very meagre allowance, viz., nine gallons per day which the Pokfoolum project yields, and in spite of its many other disqualifications, it is possible that a desire to lean to it may arise, on account of its reduced estimate and high level delivery.

It was the fear of this contingency that led me in the beginning of this Report to recapitulate the efforts and failures of former Administrations to relieve Victoria in its distress for water, though perhaps, such comments on my part were not only in questionable taste, but might be deemed foreign to the business enstrusted to me by His Excellency the Governor which was perhaps not meant to be retrospective.

I trust however that anything I may have said will be justified by the very earnest object I have in view, that of proving in the plainest and most unmis- takeable language the fallacy of again repeating the policy of partial relief.

The revival of such a temporizing policy in 1873 could only be founded on mistaken economy. It would for the third time postpone the decision of the question to a future day; a day which if the Pokfoolum Project were adopted,

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would be sure to arrive immediately after its completion, when the people had become able to realize the paucity of its supply.

Water is a great civilizer, and a liberal supply of it one of the greatest sanitary blessings that can be vouchsafed to a people; it is beyond doubt a great reducer of the rates of mortality in all large communities and if it is plentiful, its very abundance tend to increase its use to the marked improvement of the social con- dition, habits, and appearance of the population.

The daily allowance provided by modern water supplies to English towns has already been stated to be about 20 gallons per head of inhabitant, surely then the requirements of a tropical city like Victoria can not be less!

Our defective system of drainage and sewerage, our bye-ways and alleys in the Chinese quarters and "back slums" of the city, our markets, slaughter houses, and public latrines, all require pure water in its greatest plenitude to remove as expeditiously as possible all noxious and decomposing matters which at present vitiate the surrounding atmosphere.

An inspection of the Chinese districts discloses the phenomenon of a dense mass of people herding together in dark and ill ventilated dwellings totally devoid of drainage, and where the house sewage, kitchen refuse, and sullage are generally kept standing inside each house in a tub from which is evolved an effluvium that would turn the stomach of a carrion crow. It is true that the vital energy of the occupants of such places is so lowered, and their olfactory nerves either so blunted, or so supernaturally fortified against the offence as to render them callous about it, but notwithstanding, the germs of disease lurk there, and are being generated by a pernicious and revolting system which urgently demands. reform. This reform is to be found in the substitution of proper and effective house and street sewage capable of being flushed when required by an ample supply of water.

Apart from public sanitary considerations it should be borne in mind that in a tropical city the intense heat of the climate makes the use of water for do- mestic purposes more grateful and frequent, and therefore more general than in temperate climates.

It is likewise of importance that every facility should be given to the shipping frequenting the port, to fill their water casks and tanks as expeditiously and cheaply as possible. For this purpose water should be laid on to public wharves and other places to be hereafter decided upon, along the sea frontage of the city, and these advantages should be extended to the junk and sampan population who should be able to obtain their daily store by coming alongside any of the sources along the Praya, which the authorities might assign for their use.

In a city of the wealth and importance of Victoria, it will not be too much to aspire to a few ornamental public drinking fountains interspersed through its most frequented thoroughfares. These would not fail, during the parching heat of the summer months, to be a boon to the humbler classes of the com- munity who have to labour through the streets during the day, and also to the foreign seafaring people who at present have to repair to taverns even if only in want of a drink of water.

The cultivation of trees and plants, so essential to the public health, is now rapidly increasing in Hongkong, which but a few years ago was comparatively a treeless and barren rock. The creation of gardens and plantations in every direction should be fostered and encouraged as jealously as any other great sa- nitary measure, and to this end an allowance of water should be made to provide for a moderate amount of irrigation during the long droughts to which the colony is so unfortunately subject.

In spite of the regulations which Government has prescribed in regard to the class of materials to be used in the construction of houses, and the improvement which has taken place in late years in the organization and appliances of the Fire Brigade, the city still continues to be subject to frequent conflagrations. On these occasions an amount of water is used in a few minutes equal to the quantity which would be consumed by many thousands of people in a day, and it is therefore of the last importance that the project selected should be able, while it was liberally answering all other demands upon it, to cope with any sudden emergency in this respect by maintaining every main in the City charged to its full power day and night.

The Pokfoolum Project with its nine gallons per head is unable to satisfy all these requirements, for they exact a supply of from 15 to 20 gallons; under the

————“་

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circumstances therefore, I can have no hesitation in recommending that it should not be adopted.

I have now only to revert to the Aberdeen and Tytam Projects, between which there is infinitely more analogy in the matter of volume of storage and supply. There will however be no difficulty in deciding between these two, for the advantages of the Tytam valley over that of Aberdeen are so manifest as to make the verdict in its favour a foregone conclusion.

The former can deliver a daily allowance of 134 gallons at a height of 375 feet above the sea, and the latter only 10 gallons at a height of 216 feet. The difference of cost between the two is £9,423 in favour of Aberdeen, but this difference barely compensates for the increased expenditure which this project would throw upon the subsidiary Pokfoolum works, in the shape of a high level service reservoir in town to provide the higher districts.

A glance over the estimates attached will satisfy the most economical mind, that financially there is very little advantage to be gained in adopting the Aberdeen Project in preference to the Tytam one, while on professional and sanitary grounds the latter is immeasurably to be preferred because it conveys a larger volume of water at an elevation not only high enough to avoid the intricacies of a double set of distribution works, but also sufficiently so to be above cultivated grounds, or inhabited and frequented places along the route, the drainage of which would filter into the conduits and affect the purity of the supply.

Coming to the only conclusion possible in this matter, I shall assume that the Government will adopt the Tytam project in its integrity, that it will also carry out a subsidiary conduit from the present small reservoir at Pokfoolum to a site in town so as to accomodate the houses situated above the level of the Tytam supply, and that it will reorganize the distribution of the water through the streets, a reform very urgently needed and which cannot be undertaken too soon.

These works will take from four to four and a half years to complete after the date of their commencement, and their combined total cost including labour, material, transport, plant, machinery and superintendence having been approx- imately estimated at £302,147 by the schedule of prices in use for many years in this department, * verified by past experience in the Pokfoolum works of 1867 show that they can be accomplished for £3.5.8 per head of population, a rate which does not contrast unfavourably with Mr. RAWLINSON's experience of the same class of works in England.

The difference of cost in favour of the Hongkong proposed works may in this instance be accounted for by the fact that a very considerable portion of the work, viz., the Pokfoolum reservoir providing 4.43 gallons out of the total 18.50 gallons has already been built, and by that of the new works being, although quite as sub- stantial, yet of a much ruder form and design than engineers are in the habit of car- rying out in England, where architectural effect is very properly studied equally with efficiency and solidity.

It would however be injudicious in the case of a colony like Hongkong to squander in display, means which if available, should be husbanded for other useful sanitary works in connection with the drainage and sewerage of the city, a matter quite as important as the projected water supply.

The method of providing by an adequate financial plan the means of carrying out the new waterworks, and of distributing the burden of their cost over more than one generation of colonists, and the revenues which might be eventually derived from said works, are matters which do not legitimately enter into my province, and I therefore abstain from touching upon them.

But as the Government cannot but desire to be in possession of the fullest particulars of an enterprise for which such a necessarily heavy call is made upon its means, I deem it desirable to include in this Report as accurate a description as the preliminary data in my possession will allow, of the works now proposed and recommended.

* Except the tunnel work which has been specially calculated and estimated.

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DETAILS OF CONSTRUCTION OF THE PROPOSED

NEW WORKS.

These will consist of the following:-

1. A dam with outlet works and bye-wash, &c. in the Tytam valley to

form the main storage reservoir.

2. A conduit from the Tytam reservoir to the City.

3. A service reservoir in the City to hold a three days' supply.

4. Re-arrangement of the water distributing apparatus throughout the

streets.

5. Subsidiary Pokfoolum Works.

The Dam.-This work as already stated would be an embankment 400 feet long and 90 feet in its deepest part. Its inner slope, or that next the water would be 3 feet horizontal to 1 foot vertical, and its outer one 2 to 1; halfway down the latter is a verm or bench 20 feet wide, which will not only tend to in- crease the stability of the dam, but also be most useful as a road to get across from one side of the valley to the other. The bottom of the valley about the neighbourhood of the proposed dam is by no means steep, and therefore the toe of the bank will not extend very far down the gorge, nevertheless to secure a perfect footing it has been deemed expedient to cut the ground into steps, so that the pressure of the enormous superincumbent weight may make the cohesion of the base more compact.

Although it is to be regretted that outward appearances do not indicate a substratum of solid sheet rock, allowing the construction of a rubble masonry dam in lieu of an earthen embankment, it is highly satisfactory that the ground is in every way favourable to the formation of a strong and reliable structure of the latter description.

The central portion of the site of the damn will be excavated down to in- permeable strata, in the form of a V trench, the bottom of which will not be stepped up the hill sides, but be dug at an angle equivalent to their inclination, so as to preclude the opening up of joints between the natural surface and the artifi- cial one when the subsidence of the centre of the bank draws its two extremities towards one another and away from the face of the hill.

It is proposed to fill the trench, and the whole of the floor of the inner half of the embankment with the best Portland cement concrete laid upon a 2 inch layer of hydraulic mortar, and to intersect the floor of the outer half by a com- plete system of small drains to carry off any possible leakage. The top surface of the concrete in the trench will also assume a V form and after receiving a 1 inch layer of hydraulic mortar it will form the seat of foundation upon which will be built the wall of puddled clay which is the real barrier to the escape of the water, and the main feature of the whole work to which we must look for safety.

It is proposed to carry up this wall to a height of 90 feet with a bottom width of 35 feet, and ending with a top width of 15 feet. It will be supported on either side for fifty feet, by selected and water-tight material which will be carried up in nine inch concave layers together with it, each layer to be thoroughly well punned and rammed down before another is spread out. The outer parts of the embankment will be built up in the same manner and will consist of earth ex- cavated in the immediate neighbourhood, but by no means on the site of the re- servoir, the bottom of which should not be tampered with. The quality of the clay procurable in China is generally very fair and if properly selected, well watered and cut three times, will form a good puddled wall reliable even to the vast height of 90 feet. The slope towards the water should be covered with 18 inches of macadam metalling in order to prevent the waves from washing away the earth behind it. The outer slope should be well turfed but no other ve- getation allowed to grow upon it. The embankment will finish four feet above top water level with a width of 20 feet, and after complete subsidence has taken place it would be well to cover the top with a shell of concrete, slightly convexed to keep out surface waters.

The Outlet Works.-The dam of any reservoir being an artificial structure is naturally its weakest side. If any way of avoiding it can be devised this weakness should not be enhanced by works liable in the course of time to derangement

( 19 )

and decay. Their submerged and inaccessible position renders them the master of the engineer who becomes helpless to deal with them if anything goes wrong. Pipes, masonry culverts, or other outlet works should therefore not be built under the made portion of the bank if they can be located in the solid natural ground or driven under it. The contact of the hard smooth surfaces of different materials however ingeniously welded and cemented together and interlocked, will always in- crease the chances of leakage. If there be any vent under pressure, the water would ooze out between the junction of masonry and puddle, or the latter and concrete, or between the surfaces of iron piping and puddle or concrete. The beginning of the leak would perhaps only be an appearance of dampness due to capillary at- traction, eventually a few tears would appear and these, in course of weeks or months, would resolve themselves into a little rill, at first of scarcely perceptible proportions but gradually gathering strength as it melted the clay in the heart of the dam and wore for itself a way through it. Arrived at this stage the destruction of the latter is merely a process of time and this process has in some cases been known to be very summary.

In 1864 near Sheffield a dam burst during the night and the contents of a reservoir being suddenly freed, drowned a village in a few minutes.

A structure of the great height as that proposed at Tytam should under no consideration be exposed to such risks, and I have therefore made provision to tap the reservoir by means of a tunnel under the hill, on the western side of the embankment.

As nearly as possible with the centre line of the bank, on a solid foundation, 10 feet above the bottom of the reservoir, it is suggested to build a masonry tower of a thickness sufficient to ensure perfect stability and to resist the creeping effect of water; it is possible on examination of the foundations that it might turn out preferable to erect it in the reservoir, just clear of the embankment, if so a light bridge would be required to connect it with the top of the embankment. The tower would be lined inside with cast iron plates, and be divided into two com- partments by a cast iron diaphragm, perforated every ten feet vertically with valves to be worked by spindles from the top. The inner length of tunnel would lead into the inner compartment of the tower and consequently both would always be charged. The water would be shot down on to the floor of the empty or outer compartment, by turning the spindle and opening the nearest valve below its level, from here it will escape through the outer tunnel into a masonry guage-basin out- side, and finally into the conduit. The tunnel should be lined with masonry set in cement backed and rammed hard with concrete, and along its floor, an iron pipe may be laid leading out from the bottom of the reservoir to act as a syphon, in the event of its ever being required to empty the reservoir of the lowest layer of water lying below the level of the outlet mouth.

The tunnel will be made to serve as a temporary bye-wash during the con- struction of the seat and lower portion of the embankment, and it is proposed to divert the beds of the three streams flowing down the valley, and to bring them to the mouth of the tunnel in rough wooden channels or open boxes caulked and made water-tight. This expedient is resorted to, because the sides of the hills contain so much granite that the cutting of a trench to serve as a temporary bed would entail an undue amount of labour. I foresee no difficulty in these tempo- rary works, if they are carried out during the dry season.

The Bye-wash.-Allusion has already been made to the extraordinary outline of the proposed reservoir, which spreads out into three arms converging towards one another near the dam. One of these arms is admirably adapted to the formation of a bye-wash affording accommodation by far in excess of what is actually required; indeed the site is so extraordinarily favourable in this respect, as to limit the necessary works simply to the formation of an ashlar masonry weir with a top level four feet below that of the dam. This weir should be built in an arched shape on a concrete foundation across the small valley which is 180 feet wide, and it should have a projecting coping so as to throw the water beyond its outer foot, on to a series of rough stone steps also firmly laid on concrete; each step should have a three foot tread, and an inward slope so as to break the fall of the overflow. The latter would be conducted back below the embankment, into its natural watercourse through the smaller stream at its side. The bed of this stream will have to be paved. To save masonry the 180 feet width of bye-wash space will gradually con- verge, funnel shaped, into somewhat narrower dimensions, accordingly as it gets lower down the steps, and these would be flanked by two solidly built low walls to keep the water within bounds.

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The Conduit.-I have already touched so often upon this important portion of of the new works that it will not now be necessary to do more than describe the shape and construction proposed, and the method which I think it will be best to adopt for catching the surface drainage of the hill sides without endangering the stability of the channel itself. During the rainiest months of the year, we will have to contend against a rush of water so great as to justify my assertion that the supply to the City during this season might, if required, be made almost unlimited.

There is no need however to fall into this extravagance, and it will suffice if we can ensure an average of 30 gallons per head daily, between May and October, and 18 gallons between October and May. Such a provision would lay aside all just grounds for complaint. It will be evident that the carrying capacity of the conduit must increase from its source as it progresses towards its terminus, laying every hill and dale under contribution and every moment requiring more room to contain the increment. It is therefore proposed to build it in different sections, one consecutively larger than the other, somewhat in the resemblance, if I may use the simile, of a telescope when it is pulled out. There would be a different cross section at every mile in the following ratio:---

Length.

1st mile

Internal Width of Conduit.

2 feet 6 inches.

22∞ að að að

2nd

""

3rd

3

4th

""

5th 61

""

3

3

""

9

0

3

A F

11

3

""

6

3

9

""

""

Internal Depth of Conduit.

1 foot 6 inches.

1

9

2 feet 0

2 2 2

11

3

6

339

150

11

19

9

"}

19

My first recommendation with regard to the conveyance of the supply was a canal dug along the hills lined with a shell of concrete, but the cost delivered in Hongkong of Portland cement, the principal ingredient in concrete, was calculated and found so great that a brickwork or masonry channel becomes preferable. In my opinion the best combination of economy and solidity in a conduit is to be at- tained by a granite floor 1 foot thick laid when necessary on a foundation of con- crete, and bricksides 9 inches thick laid and lined in cement; over this a cover of roughly hewn granite slabs 4 inches thick should be laid with half lap joints. The efficiency of the work entirely depending on the solidity of the foundations, the latter must be cut out of the solid ground, and it is this contingency that will entail the increased cube of excavation provided for in the estimate. A glance at the diagrams appended will show much better than I can explain, the class of con- struction proposed for a conduit along the steepest and most unfavourable sidelong ground, for one on a flatter slope, and for one in tunnel through three different

strata.

It will be necessary to leave an inner margin or space of 3 feet between the conduit and the hill side, to allow of a surface drain running parallel and between them, and a path of 4 feet on the outer side to be sodded and turfed to enable it to withstand the furrowing effect of the heaviest rains. In unusually steep places these widths must be increased, and greater drainage accommodation provided so as not to hazard any risk of damage to the work by flood waters.

It is designed to give the conduit an inclination of four feet per mile, not in the form of an inclined plane, but in four steps or drops of one foot each. This expedient will greatly facilitate work because Chinese masons and rule of thumb workmen although they may be trusted to build on the level will assuredly not be able to calculate to the nicety required, the decimal of fall per yard forward entailed by so imperceptible a vertical angle as 4 feet in a mile. The speed of current attained will be the same, because although the bottom of the water will assume the shape of four horizontal planes, its surface will, by natural laws, adopt the inclination due to the loss of head specified.

If the conduit were set out strictly along the contour of the hills, it would be composed of one continued series of curves throughout its entire length. As this would give rise to the intricacies of construction on circular and S shaped lines, it has been deemed advisable to adopt the ruder but simpler method of setting out the work in short straight broken lines, adhering as much as possible to the serpentine shape of the contour without going actually into curves. Beyond

Catchwater.

HONG KONG WATER SUPPLY

Cross Section of Open Conduit.

on hillside.

CONCRETE

Conduit.

Catchwater

*

T

CONCRETE

Conduit

HONG KONG WATER SUPPLY

Cross Section of Open Conduit

on

steep hillside.

1

HONG KONG WATER SUPPLY

Tunnelled Conduits.

In Solid Rock.

6ft oin.

In Fissured Rock.

CONCRETE.

oft oin.

Foin./

In Earth.

CONCRETE

1

H

1

:

"

!

( 21 )

doubt this plan will be most disparaging to the general appearance of the work when completed, but as it would materially expedite and simplify it, we may afford to sacrifice looks to expediency.

So far the class of structure described refers only to those portions of it tra- versing the softer strata. Sheets of granite may be discovered along the length of the route, in which case the water may be carried through them in a rough trench requiring no masonry, brickwork or concrete. Occasional fissures can be sealed. with concrete and cement, but if there are many of them, it would be prudent at once to give the trench a lining of concrete to ensure a water-tight channel.

The surface drainage of the hills above must not be allowed to pour down into the conduit wherever it likes. A ditch or catchwater must run along the hill side, parallel with the conduit and fifty feet above it, to act not only as a safeguard against the scouring and destructive action of storm waters which if allowed would soon furrow and deface the excavations, but also to intercept these waters and to convey them to places where the conduit may most conveniently absorb them. When feasible the catchwaters should be made to empty their contents into the nullahs which intersect the line at frequent intervals; from these nullahs the con- duit would take in by the following simple process, as much as it can carry and no more. A small dam would be built across each stream at a level above the conduit and below the catch water; into the dam would be fitted earthenware piping laid in concrete, leading down into a small but very substantial masonry tank or box built against the inner side of the conduit. It is the overflow from this small tank that would form the wayside supply which has been time and again alluded to in the course of this paper. The tank has been designed as an intermediate re- ceptacle to break the force and violence of the water flowing from what in the rainy season would be mountain torrents, and to act as a settling pool in which their thick and discoloured contents which carry with them an immense amount of sand and sediment, may become comparatively still, and cast their deposits before entering the conduit. A precaution of this kind is necessary in order to keep the conduit as free of silt as possible, for the work of cleaning it would entail no incon- siderable trouble. The excess of overflow from the tanks would be conducted back into the streams by earthenware piping laid in concrete. A scouring cock will be necessary to each tank to make it self cleansing, when necessary otherwise it would be found to be full of sand and gravel towards the end of the rainy season. It is also intended to provide the conduit with sandpits, at every mile in order to intercept and eject any sediment which is being swept forward by the current.

There are but few places along the line where it would be desirable to build aquæducts. As a general rule ravines should be crossed by cast iron syphons firmly bedded under ground; they should be laid in concrete on stream crossings and at any other points exposed to the action of water, and they should be pro- vided with close gratings across their up streauns mouths to strain the water, and with scouring cocks at their lowest points of depression, in order to expel pe- riodically the mass of silt which is sure to accumulate within them.

The joint between the conduit and the syphon would be made by means of a small masonry tank from which the latter will descend down the ravine, and re- mount to a second tank on the opposite side, built at a level lower by one foot, the conduit again commencing from the second tank. The object of this is to give the water in the syphon a head of pressure of one foot to expedite its delivery. There will be four syphons in every mile of conduit and consequently, as before stated a total fall per mile of four feet.

With regard to the question of the purity of the supply if conveyed in con- duits, I need but point out that the only risk of pollution would be from sewage irrigation percolating through the joints of the cover stones, and that this would be preventible by a Government prohibition to cultivate ground in the neigh- bourhood above. As the conduit would be covered from end to end, it would not be possible to throw dirt or rubbish into it, and with a proper system of sur- veillance it will not be difficult to prevent the washing of clothes or to keep the ravines above the city free of refuse matter.

Tunnels. The use of tunnelled conduits in preference to cast iron pipes for the conveyance of water along mountain sides has been advocated by far abler pens than mine.

While on the subject I cannot do better than quote a short extract from Major H. TULLOCH's interesting work on "The Water Supply of Bombay," which bears upon this particular point with such clearness, and in words so opposite to our own case, that one would imagine they were applied to Hong- kong instead of to Bombay.

+

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if

In describing the supply to that great city from the Concan, a hilly district in its neighbourhood, Major TULLOCH says: "if there were any advantage in pipes, this advantage would be ever so much greater in a country where pipes could be manufactured cheaply, and vice versa, the advantage would be less in a country where they were difficult and costly to obtain. Let us then enquire whether pipes have been used in preference to conduits in the land of iron. I suppose any one were asked where pipes could be obtained cheapest, he would at once say Glasgow, where both iron and the coal to manufacture it with are found in such abundance. But what do we find to be the case? In the Loch Katrine Works, among the first waterworks in the world, out of a total length of 34 miles of pipes and conduit, from Loch Katrine to Glasgow, there are only 12 miles of pipes and 22 of conduits, and in a total length from Loch Katrine to the service re- servoir of 25 miles there are only 33 miles of pipes and 22 of conduits. Mr. BATEMAN, adinittedly one of the first hydraulic engineers of the day, rather than lay down pipes, preferred to tunnel through the hills, and some of the shafts were 500 feet deep! Can any one after this doubt the necessity of our dispensing with the use of iron as much as possible? If Mr. BATEMAN found it cheaper to bring water through conduits to Glasgow, where iron could at the time be obtained at £4 and £5 the ton, and where every mechanical appliance, cheap fuel, and the best workmen could be obtained, how much more imperative must it be for us to adopt conduits in Bombay, where pipes will cost £16 per ton, where the use of mechanical appliances entails a heavy cost, where the price of coal is 60 s. per ton, and where skilled workmen are not only expensive, but difficult to obtain."

"Let me give another example in which conduits have been used in place of pipes, and one out of England, and where the features of the country are very similar in their character to those of the Concan. The water from the great Furens Dam* is drawn for the supply of St. Etienne through a masonry couduit which has been built in open cuttings on the sides of the hills. In this instance it has been found cheaper to build a long masonry channel than to lay down a direct iron pipe."

Strong as this argument is, it becomes still stronger when we remember that the art of tunnelling has wonderfully improved since the Glasgow waterworks were carried out. There is hardly any branch of engineering in which such great strides have been made. This is shown by the last tunnel built under the Thames which was successfully completed in a few months without the least difficulty, while Brunel's tunnel took years to construct.

The tunnels required on the Tytam line would have a very reduced sectional area, viz., 6 feet in width by 6 in. height; they would be mere rat holes compared to the dimensions of those adopted in European works; they could not be made smaller without hindering the progress of the work and inconveniencing the machines and the men working them. There would be no great difficulties to overcome as the soil to be perforated is not sandy or treacherous, the strata being everywhere known to be syenitic granite, either solid or in various stages of decay, but never so friable as not to be compact, and therefore dispensing as often as not with the need of timbering to support the sides and top of the excavation. In the softer strata as also in fissured rock it is proposed to line the tunnels with native brick, all hollows between the brickwork and the sides of the excavation being filled with concrete. The sectional form of tunnel recommended is shown in the diagrams appended, and consists simply of vertical sides and a semicircular arched roof. It is impossible to say until a closer and more detailed experimental search has been effected, what proportion of the aggregate length of these tunnels will have to be built or lined in brickwork, but one half has been assumed as a fair allowance, and I do not think that this provision will be very far wide of the mark.

The conduit form of conveying water unavoidably necessitates tunnelling for it is obvious that in mountain districts a masonry channel cannot follow the sinuosities of every hill and valley like a pipe. The latter being buried in the ground is safe. A conduit running along the surface is liable to be swept away if it is made to skirt round sharp projections and corners. Totally apart from the question of safety it would be expedient to adopt tunnels if only because they save long detours, and because in thus shortening the route they reduce the final cost of the works, as clearly shown in the estimates attached which represent the

* This is the highest reservoir dam in the world supplying St. Etienne in the Departement Loire with water from the Furens Lake.

J. M. P.

*

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expense of 5 miles of conduit including tunnels at £66,762 whereas the same dis- tance in pipes calculated at £20 per ton, would entail £73,185 or an excess of £6,423.

The life of iron pipes in Hongkong is uncertain, but it cannot assuredly be more than 20 years, judging from the appearance of those laid down by Mr. RAWLING in 1861, which are already badly eaten through with corrosion.

If therefore, conduits with tunnels are not adopted, the Colony would be saddled at the recurrence of every 20 years with the expense of a renewal of 64 miles of pipes, which based upon present prices, would entail a cost of £87,125. But, who can tell in 1873 to what height the price of iron pipes may not have soared in tewnty years?

Having I trust satisfactorily asserted the superiority of conduits and tunnels over iron pipes, I may proceed to point out the most practicable method of effecting all the tunnelling required in the proposed waterworks. Where the ground to be mined is soft the work should be done by the pickaxe, but on coming to granite, boring machinery should be resorted to. There are various des- criptions of tunnel driving machinery in use in Europe, but that now most ex- tensively adopted is the "Diamond Rock Drill," the success of which has caused it to be justly ranked among the most ingenious engineering inventions of our day. The machine is very simple in construction and not liable to get out of order; it moves on wheels and travels forward according to the progress of the excavation. To it are attached any number of drills required, pressed against the face of the rock and made to rotate, so that by the act of abrasion perforation is effected at a rate varying with the hardness of the stone acted upon. In granite the average working progress of the holes would be about 2 inches per minute.

When, at the expiration of 20 minutes, the whole face of the rock had been riddled with holes about 34 feet deep, the drills would be run back, and the holes loaded with gunpowder, tamped, and exploded in the ordinary way, the debris being cleared and swept away, the drills would be again brought forward, and 20 minutes after their first revolution, another 3 feet of tunnel would be ready for blasting out, and so the process would be repeated till the tunnel was completed. The rate of progress in England of much larger tunnels than those contemplated here, and driven by the machinery just described, through strata quite as hard as syenite has varied from forty to fifty feet per week.

The Diamond Rock Boring patent is the property of an English company who contract at a fixed price for the execution of work at home and abroad. An agreement might be entered into with them to execute for the Government of Hongkong, at a preagreed rate, all the tunnelling necessary, or else it might be arranged to let the Government have on payment of a premium to the Company the use of a certain number of the machines to be worked under the superin- tendence of its own Engineers.

The Service Reservoir.-This is the name applied to the reservoir or tank con- taining a three days' supply with which nearly every English town is provided, and which is generally situated in its immediate neighbourhood, on a site sufficiently lofty to give high pressure over the tops of all the houses.

The consumption of

The object of service reservoirs is told in a few words. water fluctuates very much in cities, it is not uniformly spread out over all the hours of the day, the bulk of the requirement being all drawn from the pipes simultaneously by every consumer during a limited time. The "draw" of water, for domestic purposes, is so excessive during the early hours of the morning, that according to the highest authorities, if it were kept up continuously at the same rate, the whole supply would be exhausted in eight hours. From this it may be gathered that pipes or conduits conveying water into cities must be sufficiently capacious to deliver not only a volume adequate for the day, but one which shall be sufficiently large to withstand the onset made upon it between 5 o'clock in the morning and 12 at noon. The run upon the water begins at 5 A.M. and reaches its maximum at 8 A.M., the crisis continuing till the middle of the day when it subsides gradually till it reaches a minimum after midnight. But pipes or conduits able to deliver a supply that will bear the brunt of the ma- ximum hourly demand, must be very expensive things on account of their great size. It is therefore usual to resort to the expedient of a service reservoir into which the supply steadily flowing in during the hours of the night, can have time to accumulate into a volume sufficiently large to meet the greatest exactions made upon it during the following morning, and this without showing any very great decrease or variation of the pressure which it is sought to maintain as uniformly as possible in the mains throughout the city.

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Another object, no less important, in having a service reservoir or tank, is to place the water service as much as possible beyond the risk of irregularities, by continuing the supply to the mains from the service reservoir, when accidents and failures occurring in the conduits, aqueducts, syphons, outlet works, &c. and requiring time to rectify, shall have entailed a stoppage of it from its true source, the storage reservoir.

To cut off the water supply of a city of over 90,000 inhabitants for a day or two, or even for a few hours wonld be an inconvenience so intolerable that it is necessary to include a service reservoir among the proposed works for Hongkong, the more so when we consider that the nature of the ground which the main channel of supply has to traverse renders the possibility of leaks, from storm damages or treacherous foundations not an unlikely one.

It

The aggregate cubic capacity of the present distributing tanks is somewhat less than one million gallons, so that they do not contain more than half a day's supply. This provision being totally inadequate it is proposed to erect a high level service reservoir to contain five million gallons or a three days' supply. would be 300 feet long, 100 feet wide, and 25 feet deep. The conduit from Tytain would enter it on the 375 foot contour level, and the outlet artery would be placed about 2 feet above its floor.

The reservoir should be of rubble masonry constructed over a solid concreted foundation with floor and sides set and lined in cement; it should be roofed or arched over so that the water may be protected against the heat of the sun which would provoke rapid evaporation, and also against the atmospheric impurities which float in the air of populous districts. It should contain two compartments divided lengthways by a water tight partition wall, so as to allow of its being cleaned when fouled with silt, without interruption to the service. This can be done by keeping one compartment filled and doing duty, while the other is emptied and swept out. Instead of running the overflow to waste in the neigh- bouring nullah it might be carried down to a fountain in the Public Gardens, and to the Dent fountain opposite the City Hall.

The best site, indeed the only one near the centre of the town, for a service re- servoir of the dimensions specified, is on the hill side immediately behind the present military tank. As this land is a War Department reservation it would be ne- cessary for the Colonial Government to effect an arrangement with the Imperial one for the occupation of the ground, and possibly, in exchange for the advantage of an ample reservoir supply during all seasons, the military authorities might be disposed to sanction the absorption of the military nullah into the new waterworks.

New Distribution Works.-As the present defective distribution of water would nullify the advantages to be derived from an increased supply, it will be necessary to take up a large proportion of the network of piping under the streets and to relay it according to established principles. It is unfortunate that no prearranged plan or system appears to have been observed in this respect. Accord- ing to Mr. MOORSOM's information it appears that as new streets were laid out, the mains have followed them, frequently without due regard to levels, so that instead of falling evenly towards their respective termini, they meander in various directions, sometimes rising and sometimes falling, and occasionally pipes of smaller dimensions have been pieced on to larger ones. An excellent opportunity offered for remodelling the whole system of retailing water though Victoria in 1871, when the Pokfoolum reservoir was completed; in that year the quotations in the price of iron pipes had not assumed the proportions to which they have since reached, and the work could therefore have been done for considerably less money than now.

It has already been explained how necessary it is that the conduit with the help of the service reservoir should be adapted to the maximum hourly demand as well as to the average daily one. The same rule holds good in distribution pipes, the fall of which from the service reservoir to the districts they are meant to serve, should be as uniform as the irregularities of the streets will permit, their diameters at the same time diminishing in the ratio of the distance which they recede from the fountain head, and according to the population of the neighbourhood through which they pass. In neither of these conditions can the present mains be made to conform to the proposed new state of things.

In a town of such irregular levels as Victoria, the virtual declivity to be given to mains will be a work requiring great attention and care, so as to avoid excessive pressure in the lower districts and to ensure a sufficiency of it in the higher ones. I would propose to rearrange the distribution with a pressure on each of the street mains equivalent to a height of 20 feet above the roofs of the houses on each side,

·

( 25 )

in order that the water may have access to their upper stories, and that it may be possible in the event of a fire to throw a jet of water over their tops without the aid of a fire engine.

The present water service in all its scantiness and poverty is even still further marred and curtailed by the condition of the mains and service pipes, which are corroded and choked to an extent so serious as to make it doubtful whether many of them could continue to be used in the new works unless at very low pressures. I have had sections of some of the largest mains in the city taken up and inspected and on every occasion the incrustation discovered adhering to the inside of the pipes has been so great as to reduce their sectional area by one third. This is by no means to be wondered at considering the number of years which they have been subjected to the proverbially destructive action of rain water, and that the water supply to the City having always been an intermittent one the greater portion of them have necessarily been exposed to the most trying ordeal which pipes could well undergo, namely, that of being alternatively charged and emptied, or wet and dried, a process extremely favourable to rapid corrosion.

As a practical proof of the destructive effect of an intermittent service in comparison with a constant one, which keeps the mains charged continuously, I may remark that the 10 inch main from Pokfoolum which since the day it was laid has only been emptied for a few hours, has been found on examination consi- derably less deteriorated than the street mains. It is likewise to be feared that decay has reduced the efficiency of the smaller pipes to a still greater extent, and that it has rendered many of them so varicose that water can scarcely dribble through them.

It seems likely therefore that even if the project for an increased supply now recommended be not adopted it will still be necessary to incur the expense of a renewal of a large portion of the piping in actual use. In reference to this parti- cular head of expenditure I need scarcely point out that it is the one of all others which the Government, when it founded the original waterworks of 1861, must have known to be a recurring one, since the life of cast iron pipes, as already stated, is limited to a certain term of years after which it becomes necessary to renew them.

It is very difficult matter to assign with any degree of accuracy what expen- diture a proper and efficient redistribution would involve. In my calculations I have assumed that when the proposed masonry conduit from the present Pokfoolum Reservoir into town is completed and water communication established, 3 miles of the ten inch main now in use, could be taken up, cleaned, and converted into main arteries for the principal streets.

I have further assumed that one-fourth of the existing pipes through the town will be useless, under the pressure which they will be called upon to bear, and I have therefore deemed it prudent to provide for new ones to this extent. Provision has also been made for the cost of cleaning and relaying as many of the pipes which it is thought will not be found on examination to be too deteriorated to continue in use.

A contingency has likewise been added for the probable cost of extra hydrants, fountains, stand-pipes, air locks, meters, loaded valves, scouring cocks, and the many accessories of a complete and efficient water supply in good and reliable working order.

In all cases where it can be done I would recommend the adoption of native earthenware pipes which can be procured in Canton at a reasonable cost. China stands preeminent among nations in this class of industry, her clay is almost unsur- passed, and the specimens of native earthenware that have come under my notice are as regards quality and material equal to any that I have seen in England. It would of course be out of the question to use earthenware pipes for the water distribution through the streets, but they may be advantageously employed in isolated sub-supplies of which there are a great many issuing from the main supply, and in all works connected with the feeding of the conduits and in carrying off their overflows and that of tanks.

THE SUBSIDIARY POKFOOLUM WORKS.

Having touched upon the works entailed by the Tytam Project as cir- cumstantially as the preliminary nature of this Report has allowed, I will proceed to describe how it is recommended to utilize the present Pokfoolum Reservoir in

the new scheme.

( 26 )

The Tytam reservoir in spite of the many advantages which recommend it, could deliver water no higher than 375 feet above the sea, the houses above this level must therefore be provided from the Pokfoolum reservoir the outlet of which is as high as 500 feet. A conduit is therefore recommended from the outlet at Pokfoolum leading to a small service tank in town to be situated in the immediate vicinity of the proposed main service reservoir as shown in the photograph attached.

The tank would be to the people dwelling above the level of the service reser- voir, what the latter would be to the City. One small main issuing from the tank would suffice to meet all the requirements of the neighbourhood and it could be voided of any surplus water by uniting its extremity to one of the service reservoir

mains.

Instead of building a masonry service tank it is proposed to remove the iron one at present in the Public Gardens and to utilize it on the site required. The most ample overflow channel must connect the iron service tank with the service reservoir, for it has been calculated that owing to the small number of consumers living above the 375 foot level, more than seven eighths of the whole Pokfoolum supply will overflow from the tank into the reservoir.

The conduit from Pokfoolum will be of the same dimensions as the first three miles of the Tytam one, it will have the same gradient per mile, and will have the same adaptability to catch hill side drainage. It will entail two tunnels and 167 yards of iron piping, and I may add that if not regulated by a proper valve at its source it would empty the Pokfoolum reservoir in less than two months of dry weather; it is however intended that the supply should be cut off whenever the water has subsided to its last eight or ten feet of depth, at which stage it would become thick and perhaps impure.

The present Pokfoolum works will bear an important part in the future supply, and although their inefficiency is under present circumstances to be re- gretted it must be remembered that without their future help even the Tytam valley could not be made to yield the quantity of water required by the people. The capital sunk upon the Pokfoolum works cannot by any manner of means be said to have been misapplied if His Excellency the Governor contemplates achiev- ing the great work now under consideration, and of which they may be called the first instaliment, and not the least important one.

TEMPORARY SUPPLY PENDING THE COMPLETION

OF THE WORKS.

+

Although the City of Victoria can not be said to be in extremis for the want of water, it is none the less to be denied that the individual discomfort of nearly every household from this need is very considerable. Under such a grievance, four years and a half would seem a long and disheartening time to wait for relief, yet in spite of the utmost expedition it would scarcely be possible to complete works yielding an efficient supply under this time.

The difficulties which the engineer has to contend against in carrying out an enterprise of any magnitude abroad are perhaps only known to himself; the distance which divides him from his supplies of stores, materials, and all the labour saving mechanical appliances which so immensely facilitate such under- takings in European countries are denied him in distant colonies, and this tends to hinder progress no less than the absence of efficient workmen upon whose technical experience he might rely for the satisfactory prosecution of the works when his attention is called away to other duties; neither is the climate of Hong- kong favourable to rapid progress, the intensity of the periodical rains making outdoor work almost impracticable during four months of the year. It therefore becomes a matter of necessity to devise some means of partially relieving the wants of the city pending the completion of the works which are to render water abundant, but which are to take such a long time in doing so.

I therefore think that the Government could not do better than follow the suggestion contained in Mr. RAWLINSON'S letter of the 4th of June to the Crown Agents wherein he recommends that the proposed conduit should be made the medium of a temporary supply, while the formation of the storage reservoir is in

(27)

progress. Although it may seem an anomaly, it nevertheless happens that the dearth of the water is most sore upon the people just at the time when it is falling in deluging torrents from the skies. The intense heat of the summer months increases the demand for water among the natives, for bathing, washing and domestic purposes very materially, and it is precisely during the summer months that without the aid of a storage reservoir the conduits could, from hill side drainage alone, convey to the service reservoir a volume sufficient to keep it brimfull. The truth of this must be patent to anybody who has noticed the nullahs in the neighbourhood of the city, gorged to repletion, pouring their contents into the sea by millions upon millions of gallons while the people, pinched for water, are lamenting the slender allowance upon which they are kept.

In order to reap the benefit of the new works at the earliest stage of their progress it would be necessary to begin by building the service reservoir and service tanks, and by extending from them, East and West, in the directions of Tytam and Pokfoolum, the masonry conduits which are to absorb the nullahs flowing down the northern slope of the island. A pipe of adequate dimensions could be laid down provisionally from the service reservoir to the nearest street main to unite the new supply to the actual one. If these suggestions are adopted, the present allowance of water may be very materially increased during the rainy months, within one year after the commencement of the works.

Steps are already being taken to increase the small subsidiary supplies which the City derives from Wong-nei-chung and other nullahs, by raising the dams across them so as to have no overflow except that of storm waters; this will not increase the present provision very materially but perhaps even the smallest con- tribution may be acceptable to a tropical city which is doing only upon 4 or 5 gallons a day per head of inhabitant.

1

PREVENTION OF WASTE, UNDUE CONSUMPTION, AND

CONTAMINATION OF THE WATER SUPPLY.

So far I have only alluded to the best method of gathering, storing, conveying and distributing water, I now enter on entirely new ground and will conclude with a few words in reference to the preservation of it after it is procured, and the precautions necessary to ensure its purity. These will perhaps be best understood by a perusal of the regulations appended which are intended eventually to be embodied in a local Ordinance, if approved by His Excellency the Governor in Council.

Under my directions, one thousand nine hundred and thirteen taps and water- cocks have been examined in the dwellings of Europeans and Natives alike, between the 4th of September and the present date, of these one thousand three hundred and fifty have been found to be sound and water-tight, and five hundred and sixty- three leaky, in other words nearly 30 per cent of the water fittings in use are defective. These observations refer only to waste from defective workmanship on the part of plumbers, or from the general use of a cheap and inferior class of fittings, but it is to be feared that prodigality likewise, to some extent contributes to curtail the supply.*

Among natives the money value of water would appear to be but imperfectly conceived, they cannot be made to understand that its misuse tends to the preju- dice of all; if with the present very starved supply such waste exists, it is only fair to presume that it will develope in proportion with a more liberal provision.

I have not hesitated therefore to recommend, in the interests of the Commu- nity at large, special legislation in terms sufficiently effective to check so inexcusable a state of things.

It is proposed to make the use of water-tight fittings and pipes compulsory by requiring them to be of a certain standard of efficiency, weight, and solidity, and to abolish the use of waste pipes which are only the promoters of extravagance. It is proposed likewise to deal with cisterns and all other apparatus connected with

*In my visits to some of the Chinese houses, I was somewhat disconcerted to discover that a very general way of washing linen was by piling it under the supply tap, and keeping it in soak with the full force of water turned on upon it for a day or night.

( 28 )

a house supply, from which by careless or defective workmanship leakage might arise, and to aim specially at the misuse of water by restricting the size of all house pipes to a waterway or diameter capable of delivering a fair and generous allowance, but not admitting of any serious amount of waste, and also by effecting all connections with the mains by means of stopcocks, which will enable the officers in charge of the distribution, to cut off the water from any particular dwelling where undue waste or consumption has been detected.

Some of the clauses in the proposed Act provide for the protection of the water flowing through pipes laid across drains or sewers, or near cesspits and other places likely to generate deleterious gases. The necessity of these protective measures is obvious and as the clauses explain themselves, there is no need to dilate upon them here.

If the new supply is carried out, the present intermittent service will become a constant one. Every main and pipe in the City will be charged to its utmost extent, day and night, and the knowledge that there is abundance in the house at all hours, may perhaps tend, at all events on the part of Europeans, to lessen the amount of waste caused by the objectionable expedients which are now resorted to. They will not go to bed leaving every tap in the house open, because they fear that the water will only pay a short and flying visit to the main between two and four in the morning.

Having carefully gone through every point to which my notice was directed by His Excellency the Governor on the first day of my arrival in the colony, I have now nothing left to add unless it be to reiterate my regret that the close and cautious investigation, notwithstanding that it could only be a preliminary one, which the importance of the subject demanded of me, and the many cares which have of late divided my attention, should have so long debarred me from placing this Report in your hands.

I have the honour to be,

Sir,

Your most obedient Servant,

JOHN M. PRICE,

Surveyor General.

(29)

Mr. Rawlinson, C.E., C.B., to the Crown Agents for the Colonies.

LONDON, 29th May, 1873,

+

The Crown Agents for the Colonies.

GENTLEMEN,

I have had several interviews with Mr. MOORSOM relative to Hongkong, the Waterworks at Pokfoolum, the Town of Victoria, and as to sites for additional

Reservoirs on the Island.

At my request tracings showing the contouring of the District near Victoria have been prepared as also a Report. These documents are sent with the tracings, as also the Returns and Reports sent from Hongkong.

Hongkong is a small Island situate off the South-eastern Coast of China, at the mouth of the Canton River, the length East and West is about eleven miles, the breadth is from two to five miles, the area is nearly twenty square miles. The Island is separated from the mainland by about half a mile. Granite rises in cones from five hundred feet to eighteen hundred feet above the sea, having steep slopes. There is no large area of land at such a level about Victoria as to permit of a large impounding Reservoir being formed in which to store water; there are however several small sites where works as at Pokfoolum may be repeated.

The average fall of rain may be taken as 75 inches. A dry year fall will be down to 50 inches; a wet year fall will be up to 100 inches. The dry year fall, that is 50 inches, must be the test for water works.

The wet months appear to be May to October. Rain however falls unequally; deluging torrents in a few hours, and many weeks without rain. The Island from its surface configuration and elevation acts however as a condenser, so that small streams flow down the sides of the granite peaks almost at all times.

It is considered that provision should be made to supply with water a popu- lation of one hundred thousand, which at 15 gallons per head will require 1,500,000 gallons per day, or 552 millions of gallons per annum.

Waterworks were commenced in 1850, that is, a sinall Dam was constructed at Pokfoolum to head up the small stream 15 feet, and a cast iron pipe of ten inches internal diameter was laid from this Dam along the carriage road to Victoria. It is this pipe which is used to convey the water from Pokfoolum Storage Reservoir, and which is said to be defective and inefficient.

The Pokfoolum Reservoir has an embankment seventy feet deep and stores, when full, about 74 millions of gallons of water, having on an average in a dry season, about one hundred thousand gallons flowing in.

The area of the gathering ground above the Pokfoolum new Reservoir is about 396 statute acres, the outlet is on the 500 feet contour.

It will not be advisable to raise the Reservoir embankment as such a course would endanger the works.

The Pokfoolum Reservoir must not be considered as available in dry weather for much more than fifty days at one and a half million of gallons per day. As there should be storage for two hundred and fifty days at the least, it will require four times the Pokfoolum Reservoir capacity, or say three hundred millions of gallons of additional storage; this supposes that there will not be more than 250 days of continuous dry weather; there may however be droughts of longer continuance.

Additional Storage Reservoirs may be made at sites marked and colored on the Map as at Aberdeen and Tytam. Taking the 500 feet contour line as the point of outlet, Aberdeen site would give an area of 567 acres, and Tytam an area of about 667 acres; these areas are both larger than that at Pokfoolum and may afford sites for Reservoirs better in proportion to area, this however can only be settled by a personal examination and survey of the ground.

The Conduits from Pokfoolum, Aberdeen, and Tytam, will require careful consideration on the ground. The contours may be made available so as to obtain a graduated fall of about five feet in each mile. In all cases the Conduit should

(30)

be covered. Tunnels or Headings may be cheaper than longer contours, and inverted Syphons of cast iron pipe to cross intervening valleys may save length and cost; these are however questions also to be settled by the Engineer on the ground.

Reservoir making is a difficult operation on any site and under any estimate, but the operation will be specially difficult at Hongkong on account of the subsoil granite,) and on account of the configuration: steep slopes with hard smooth surfaces, the occasional deluging falls of rain shooting off the mountain sides as off a slated house-roof.

Over-

These contingencies must be anticipated and must be provided for. flows or by-wash space for each Reservoir must be in and down the solid rock, not less in length than 5 feet for each one hundred acres of gathering ground.

The outlet Culvert must be in the solid and may be ten feet above the bottom of the Reservoir on the inside. If the outlet Culvert is taken well into the solid hillside the Valve Well may be in the solid also and not in the made part of the Bank as at Pokfoolum; the water can be taken in from the Reservoir by a Heading.

The Puddle Wall must rest on concrete and must be supported on both sides with selected and water-tight material.

The finished embankment should be 3 to 1 inside, 24 to 1 outside, six feet above top water level, and finish 12 feet wide. As subsidence will take place, this must be provided for or must be made good as it takes place. The Valves should be so arranged as to draw the water down at 10 feet intervals, that is, the Valves should be 10 feet apart vertically.

Estimates must be made on the site.

(Signed,)

ROBERT RAWLINSON.

Mr. Rawlinson, C.E., C.B., to the Crown Agents for the Colonies.

To the Crown Agents for the Colonies.

GENTLEMEN,

LONDON, 29th May, 1873.

In accordance with instructions contained in your letters of 9th January and 5th February, 1873, I have several times seen Mr. MOORSOM relative to the water supply of Hongkong. A Report from him is returned with the other papers. I have embodied the information as briefly as possible in my Report.

I have also seen Mr. PRICE several times, and have looked over the Plans, Details and Reports with him. Mr. PRICE took the papers to look over and drew up a short Report which is sent with the other documents.

Details and Estimates can only be worked out satisfactorily on the ground. With respect to the works constructed at Pokfoolum, I beg to state that in no respect are these works a failure. The embankment is sound, and it im- pounds as much water as the site permits of being impounded with an em- bankment 70 feet deep.

The Conduit pipe from the Reservoir to Victoria is the old pipe laid out 1850. Efficient waterworks are very costly in England and will be more costly in Hongkong, as materials and labor will be dearer.

To supply 15 gallons per head per day may cost from 3 to 5 pounds per head of the population, that is, for a population of 100,000 the estimate for works on the English scale will be from £300,000 up to £500,000. A ruder mode of supply may, of course, be provided at less cost; very cheap works cannot however be constructed in Hongkong, the country, climate and rainfall will not permit of cheap works. Water must be impounded and such works are necessarily costly.

I have the honor to be,

Gentlemen,

Your most obedient Servant,

(Signed,) ROBERT RAWLINSON.

+

4

>

( 31 )

Mr. Rawlinson, C.E., C.B., to the Crown Agents

for the Colonies.

The Crown Agents for the Colonies.

GENTLEMEN,

LONDON, 4th June, 1873.

The cost of waterworks in Hongkong on anything like an English plan of impounding Reservoirs will be so large as to retard the execution of such works to some indefinite period; there may however be works executed so as to give immediate relief which shall form parts of a general plan and not be very costly.

A new Conduit is required from Pokfoolum to Victoria.

New sites are pointed out for additional Reservoirs, as at Aberdeen and Tytam; there are streams at each of these sites as at Pokfoolum, and if in the first instance Conduits are formed at such levels and in such manner as to serve for future Reservoirs, these Conduits will intercept and bring in the water from these streams; as also any water intercepted on the lines of such Conduits.

In my opinion, Conduits may be made, as suggested, by local labor, and may be executed gradually, the granite cer forming the surface of the island acting as condensers, will at all times have small rills of water flowing down, and in the whole may produce a volume of several hundred thousand gallons per day; which, taken into Victoria, will be useful. Orders may be given for a local examination Report and Estimate.

Economy in the use of water will be of the utmost importance; the dis- tributing apparatus in Victoria should therefore be such as to prevent waste, but no fittings will avail if not kept in perfect order; and to insure this, there must be strict and unceasing supervision. It will be better to secure by economy 3 or 4 gallons per head per day than to have nothing. If the water in the Pokfoolum Reservoir at the commencement of the dry season, is economised at some 3 or 4 gallons per head, the volume will of course last four or five times as long as if run off at a rate of 1.5 gallons per head per day. It must be manifest to the local Authorities that care in this direction will alone prolong the existing supplies of water through the dry periods of the year.

I have the honor to be,

Gentlemen,

Your most obedient Servant,

(Signed,) ROBERT RAWLINSON.

Mr. Rawlinson, C.E., C.B., to the Crown Agents for the Colonies.

The Crown Agents for the Colonies.

GENTLEMEN,

5th July, 1873.

With respect to the cost of recent Waterworks in proportion to population for a tropical City, I wish to direct your attention to a Report on the water supply of Monte Video in the "Engineer" of 4th July, 1873. This City, in site, climate, and population may be compared with Singapore and Hongkong. The population of Monte Video is 75,000 to 90,000.

Cost of Works about ...

£500,000.0.0

Annual cost of pumping and management, say,

£2,000, which at 25 years' purchase makes...£ 50,000.0.0

Total Cost,

.£550,000.0.0

The volume of water to be supplied, about 20 gallons per head or 1,800,000 gallons per day for 90,000 persons, including water for sanitary and trade purposes. You will see on looking at the Singapore Estimate that it is very much lower, and even the Hongkong Estimate is lower.

I have thought these facts might interest you.

I have, &c.,

(Signed,) ROBERT RAWLINSON.

( 32 )

Cost of Original Water Works of 1861, begun and completed by Mr. Rawling.

1. Plant and Machinery,

2. Surveys and Superintendence,

3. Labour and Material,

...

4. Incidental Expenses,

Total,..........

....

54,636.92 11,671.00 103,032.49

343.68

$169,684.09

Cost of Pokfoolum Reservoir begun by Mr. Wilson in 1867, finihsed by Mr. Moorsom in 1871,

1. Plant and Machinery,

.....

2. Surveys and Superintendence,

3. Material,

4. Labour,

5. Incidental Expenses,

..$20,312.17

13,278.11

92,533.31

94,304.20

2,842.76

Total,..

$223,270.55

Total Cost of the Works of 1861 and 1871, combined.

Water Works of 1861, Water Works of 1871,

Grand Total,................................

$169,684.09

223,270.55

$392,954.64

}

( 33 )

Proposed Regulations to form the basis of a Hongkong Water Act, for the healthier preservation of the projected new water supply and for the prevention of waste.

1. No Communication Pipe for the conveyance of water from the Government Mains into any premises shall hereafter be laid until after the point or place at which such Communication Pipe is proposed to be brought into such premises shall have had the approval of the Surveyor General.

2. No lead pipe shall hereafter be laid or fixed in or about any premises for the conveyance of or in connexion with the water supplied by the Government except when and as otherwise authorized by these regulations, or by the Surveyor General), unless the same shall be of equal thickness throughout, and of at least the weight following, that is to say:-

Internal Diameter of Pipe in inches.

59/00 -|0n|00 m‡

inch diameter.

""

Weight of Pipe in lbs. per lineal yard.

5 lbs. per lineal yard.

6

""

19

2 A

""

""

9

""

""

""

1

12

""

""

99

1.

16

4

""

"}

3. No house shall, unless with the permission of the Surveyor General in writing, be hereafter fitted with more than one Communication Pipe.

4. Every house supplied with water by the Government (except in cases of Stand pipes) shall have its own separate Coinmunication Pipe. Provided that, as far as is consistent with future legislation in the case of a group or block of houses belonging to one owner, the said owner, may, at his option, have one suffici- ent Communication Pipe for such group or block.

5. No house supplied with water shall have any connection with the pipes or other fittings of any other premises, except in the case of groups or blocks of houses, referred to in the preceding Regulation.

6. The connection of every Communication Pipe with the Government pipes shall hereafter be made by means of a sound and suitable brass screwed Ferrule or Stop-cock with Union, and such Ferrule or Stop-cock shall be so made as to have a clear area of water way equal to that of a half-inch pipe. The connection of every Communication Pipe with the Main and pipes shall be made by the Government and the Government shall be paid in advance the reasonable costs and charges of and incident to the making of such connection.

7. Every Communication Pipe and every pipe external to the house and through the external walls thereof, hereafter respectively laid or fixed in connec- tion with the water Mains shall be of lead, and every joint thereof shall be of the kind called a "Plumbing" or "Wiped " joint.

8. No pipe shall be used for the conveyance of, or in connection with, water supplied by the Government, which is laid or fixed through, in, or into any drain, ashpit, sink, or manure hole, or through, in, or into any place where the water con- veyed, through such pipe may be liable to become fouled, except where such drain, ashpit, sink, or manure hole, or other such place, shall be in the unavoidable course of such pipe, and then in every such case such pipe shall be passed through an exterior cast-iron pipe or jacket of sufficient length and strength, and of such construction as to afford due protection to the water pipe.

9. Every pipe hereafte" laid for the conveyance of water supplied by the Government shall, when laiu in open ground, be laid at least eighteen inches below the surface.

10. No pipe for the conveyance of, or in connection with, water supplied by the Government, shall communicate with any cistern, butt, or other receptacle used or intended to be used for rain water.

( 34 )

11. Every Communication Pipe for the conveyance of water to be supplied by the Government into any premises shall have at or near its point of entrance into such premises, and if desired by the consumer within such premises, a sound and suitable Stop-valve of the screw-down kind, with an area of waterway not less than that of a half-inch pipe, and not greater than that of the Communication Pipe, the size of the Valve within these limits being at the option of the consumer. If placed in the ground such Stop-valve shall be protected by a proper cover and Guard-box.

12. Every cistern used in connection with the water supplied by the Govern- ment shall be made and at all times maintained water-tight, and be properly covered and placed in such à position that it may be inspected and cleansed. Every such existing cistern, if not already provided with an efficient Ball-tap, and every such future cistern shall be provided with a sound and suitable Ball- tap of the Valve kind for the inlet of water.

13. No overflow or Waste-pipe other than a Warning-pipe shall be at- tached to any cistern supplied with water by the Government, and every such overflow or Waste-pipe existing at the time when these regulations come into operation shall be removed, or at the option of the consumer shall be converted into an efficient Warning-pipe within one calendar month next after the Surveyor General shall have given to the occupier of, or left at the premises in which such cistern is situate, a notice in writing requiring such alteration to be made.

14. Every Warning-pipe shall be placed in such a situation as will admit of the discharge of water from such Warning-pipe being readily ascertained by the Surveyor General or Officers duly authorized by him. And the position of such Warning-pipe shall not be changed without previous notice to and ap- proval by the Surveyor General.

15. No cistern buried or excavated in the ground shall be used for the storage or reception of water supplied by the Government, unless the use of such cistern. shall be allowed in writing by the Surveyor General.

16. No wooden receptacle without a proper metallic lining shall be hereafter brought into use for the storage of any water supplied by the Government.

17. No Draw-tap shall in future be fixed, unless the same shall be sound and suitable and of the screw-down kind.

18. Every Draw-tap in connexion with any Stand-pipe or other apparatus outside any dwelling-house in a court or other public place, to supply any group or number of such dwelling-houses, shall be sound and suitable and of the waste- preventer kind, and be protected as far possible from injury.

19. Every boiler, urinal, and watercloset, in which water supplied by the Government is used (other than waterclosets in which hand flushing is employed) shall be served only through a cistern or Service-box and without a Stool-cock, and there shall be no direct communication from the Main pipes to any boiler, urinal, or watercloset.

20. Every watercloset cistern, or watercloset service-box hereafter fitted or fixed in which water supplied by the Government is to be used, shall have an efficient waste-preventing apparatus, so constructed as not to be capable of dis- charging more than two gallons of water at each flush.

21. Every urinal-cistern in which water supplied by the Government is used other than public urinal-cisterns, or cisterns having attached to them a self-closing apparatus, shall have an efficient waste-preventing apparatus, so constructed as not to be capable of discharging more than one gallon of water at each flush.

22. Every Down-pipe hereafter fixed for the discharge of water into the pan or basin of any watercloset shall have an internal diameter of not less than one inch and a quarter, and if of lead shall weigh not less than nine pounds to every lineal yard.

23. No pipe by which water is supplied from the Mains to any watercloset shall communicate with any part of such watercloset, or with any apparatus con- nected therewith, except the service-cistern thereof.

24. No bath supplied with water from the Mains shall have any overflow waste pipe, except it be so arranged as to act as a Warning-pipe.

25. In every bath hereafter fitted or fixed, the outlet shall be distinct from, and unconnected with, the inlet or inlets; and the inlet or inlets must be placed so that the orifice or orifices shall be above the highest water-level of the bath. The outlet of every such bath shall be provided with a perfectly water-tight Plug, Valve, or Cock.

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( 35 )

26. No alteration shall be made in any fittings in connection with the supply of water by the Government without two days' previous notice in writing to the Surveyor General.

27. All lead Warning-pipes and other lead pipes of which the ends are open, so that such pipes cannot remain charged with water, may be of the following minimum weights, that is to say:-

inch (internal diameter,

""

""

do., do.,

3 tbs per yard.

5

""

7

""

وو

""

28. In these Regulations, the term "Communication Pipe" shall mean the pipe which extends from the district pipe or other supply pipe of the Government up to the Stop-valve prescribed in the Regulation No. 11.

29. Every person who shall wilfully violate, refuse, or neglect to comply with, or shall wilfully do or cause to be done any act, matter, or thing in contravention of these Regulations, or any part thereof, shall for every such offence be liable to a penalty in a sum not exceeding twenty-five dollars.

30. Where under the foregoing Regulations any act is required or authorized to be done by the Government, the same may be done on behalf of the Government by the Surveyor General or some Officer of his Department duly authorized by the Surveyor General, and where under such Regulation any notice is required to be given by the Surveyor General, the same shall be sufficiently authenticated if it be signed by an authorized Officer of the Surveyor General's Department duly authorized by him.

31. All existing fittings, which shall be sound and efficient, and are not required to be removed or altered under these Regulations, shall be deemed to be prescribed fittings under this Act.

APPENDIX A.

ESTIMATE FOR THE PROPOSED TYTAM PROJECT.

Reservoir Dam,

Outlet Works,

Conduit in Pipes,

Do. Open,

Do. Tunnels,

Utilizing 25 Tributary Streams,

Service Reservoir,.

Renewal and cleansing of Street Mains,

Reservoir Dam,

Outlet Works,

Conduit in Pipes,

·

Do. Open,

Do.

Tunnels,

£

s. d.

.122,250. 0. 0

13,674. 0. 0

14,035. 0. 0

50,754. 0.0

16,008. 0. 0

6,341. 0. 0

28,673. 0. 0

7,744. 0. 0

Total,.

£259,479. 0. 0

APPENDIX B.

ESTIMATE OF THE ABERDEEN PROJECT,

Utilizing 3 Tributaty Streams,

Service Reservoir,

Renewal and cleansing of Street Mains,

4', s. d. .120,141. 0. 0

13,674. 0. 0

38,571. 0. 0

28,868. 0. 0

11,624. 0. 0

761. 0. 0

28,673. 0. 0

7,744. 0. 0

Total,.

£250,056. 0. 0

( 36 )

APPENDIX C.

ESTIMATE FOR THE (TRIPLE RESERVOIR), POKFOOLUM PROJECT.

Reservoir Dam,.

Outlet Works,

Conduit in Pipes,

Do. Open,

Do. Tunnels,

Utilizing 12 Streams,

Service Reservoir,

Renewal and cleansing of Street Mains,

• •

£

s. d.

93,166. 0. 0

27,348. 0. 0

9,305. 0. 0

26,880. 0. 0

5,380. 0. 0

3,014. 0. 0

28,673. 0. 0

7,744. 0. 0

Total,..

£201,540. 0. 0

APPENDIX D.

ESTIMATE OF THE PROPOSED POKFOOLUM SUBSIDIARY WORKS.

Conduit in Pipes,

Do. Open,

Do. Tunnel,

Utilizing 12 Streams,

Service Tank and Overflow Works,

£ s. d. 1,319. 7. 6 36,299.12. 3 1,005.16. 8

3,044. 0. 0 1,000. 0. 0

Total,..

.£ 42,668.16. 5

(37)

Comparative Statement of Particulars of the Tytam, Aberdeen, and

Pokfoolum Projects.

POKFOOLUM. ABERDEEN. TYTAM.

Area of gathering ground, in acres,

400

600

700

Drainage of gathering ground, in millions

of gallons,

180

270

316

Area of storage reservoir, in acres,

...

30

22

23

Contents of storage reservoir, in millions of

gallons,

184

213

250

Length of conduit, in miles,.

3/1/2

6

61

Length of conduit in tunnel, in yards,

633

1,366

1,883

Length of iron pipes, in yards,.....

1,166

4,837

1,760

Length of

open conduit, in yards,

4,267

4,297

7,550

Number of streams utilized on the way,

12

3

25

Height of outlet culvert above sea, in feet,

460

240

400

Height of conduit terminus in the city, in feet,

446

216

375

Height of water delivery in the city, in feet,.

424

194

353

Allowance afforded by each Project, in gallons,

9.00 ·

10.64

13.57

Allowance gallons in conjunction with sub-

sidiary works,

9.00

15.57

18.50

Cost of each Project singly,

£201.540

£250,056 £259,479

Cost including Pokfoolum Subsidiary Work,.

...

£292,724 £302,147

Rate of cost per head of inhabitant,......

£2.3.9

£3.3.4

£3.5.4

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so

Sulphur Chinnel

Belchers

Bay

Tunnel.

MOUNT

DAVIS

sandy Bay

Rock

Tunnel

Tunner

Tarhowan

Bay

Waterfall

Bay

West Point

Pessession Point

VICTORIA PEAK

CITY

VICTORIA

POK FOOĻUM

400

ACRES

Actual Reservoir

(LEY

Upper Reservoir

Timservice

Réservoir Lokfoolum Bervice Reservoir.

MOUNT GOUGH

Lower Reservoir-

Pokefu tum

MOUNT KELLET

1500

Tunnel

4

Tree 1stand

E

N

E

Tunnel

E

ABERO EEN

Aberdeen Bay

Careening Ish

West

Rock

ABERDEEN

HONG KONG WATER SUPPLY:

POK FOOLUM PROJECT

COLOURED. BLUE

ABERDEEN PROJECT COLOURED CREEN

TYTAM PROJECT COLOURED

Masonry Conduit thus

Iron Piping-

Tunnels

RED

Im Frce.

Surveyor General.

Kellet's Island

ARBOUR

О

ABERDEEN

VALLEY

ACRES

ISLAND

MOUNT JOHNSTON,

Aberdeen

Channel

Tunnel

Staun Lons

Valley

The Happy

Valle

unne?

East Point

Heong Kong

Deep Water

Bay

Middle

hd

last Point

Causeway

Bay

Jo

Kong

Water

y

North Point

Tunnel

Tuknel

Repulse

Bay

Island

THE GAP

M

Com

Quarry

Bay

Quarry Point

A M

WALL

VALLEY

ACRES

Tunnel

Bye

Wash

Aldrich's

Bay

MOUNT

PARK ER

yłam

TYTAM

BAY.

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