Island water supply - 1947
Water treatment plant
I must start with something in the nature of an apology. When Mr Guiton approached me with regard to it, I felt that the subject might become too technical in my hands and be consequently uninteresting to laymen. Nevertheless, I realised that I should be speaking to a selected body of interested Jerseymen about Jersey and that I myself would be compelled to look up certain dates in which I had long been interested.
While this paper will be devoted almost entirely to the story of the organized water supply, there is ample material for the preparation of another paper upon the wells of Jersey, particularly those in St Helier. Such a paper would be interesting from both historical and technical points of view. Certainly the details of strata and subsoil which must lie hidden away somewhere would be worthy of collection. I hope some day to be able to devote myself to this task.
The configuration of the Island is well known to most of you. The well defined valleys and streams therein being sufficient justification for the description of Jersey in Falle's History of Jersey as being abundantly watered.
The rainfall in the island from which all sources of supply must be obtained are as follows: Average rainfall - 33½ inches Driest year, 1921 - 16¾ inches Wettest year, 1872 - 45¾ inches Average of three driest consecutive years, 1920-22 - 26¼ inches Average of three wettest years 42 inches.
These figures based upon the last 75 years' rainfall show that the rainfall here closely follows observed departures from average in Great Britain, with its driest year one half of average, the wettest year 1½ times average and three driest years furnishing 4/5 of average rains. They indicate, too, that the rainfall can be likened to the British lowlands generally, but one important deviation can be noted. The winter rains (upon which the engineer relies to replenish storage) occur later than in Great Britain. Whereas in Great Britain reservoirs are filling in late September, it is November and frequently later, when this refilling takes place in Jersey.
While it is true that numerous springs can be found in the volcanic rocks which form the strata of the Island, the bulk of the rainfall is run off by surface drainage by the streams. Certain areas have a run-off which is longer delayed than others. The streams in St Peter's and Le Mourier Valley are examples of these. In these, the dry weather or summer flow is much higher, area for area, than that, say, in St Ouen's valley, where summer flow falls to a very small amount.
It follows from the foregoing that for community supply, surface water must be used, a lesson which the first company learnt to its great cost.
I have heard it said that underground water from the Continent finds its way to Jersey, but this is a theory that I am unable to endorse. It is not impossible, but it is unlikely. For this to happen there would require to be a considerable area of the older rocks such as are found in Jersey, outcropping on the Continent at a higher elevation than here. There would also require to be an overlay of impervious strata which would seal off any water falling onto and percolating into these older rocks. The impervious strata would, in addition, require to continue unbroken under the sea. All the conditions of the London chalk basin would need to be repeated. Consequently I would say that this fascinating theory must be dismissed for want of positive evidence.
As previously mentioned, records of wells are not numerous. I do not refer to records of the shallow surface wells, found at the numerous farms in the Island. I am referring to the deeper wells, which have been sunk from time to time to furnish larger supplies. One such record has, however, come into my possession, (by the courtesy of Wilfrid du Pre), and refers to the well sunk in 1806 at Fort Regent.
Apparently at that time there existed a well in Hill Street, which is described as the 'Pigeon Pump'. The presence of this well convinced the then engineer officer that water could be obtained for the fort by sinking a well on that site, to approximately the same level as that of the Pigeon Well. This work was embarked upon and a shaft some 235 feet deep was sunk. It is recorded that although some water was encountered during sinking, this casual water was never enough to embarrass the miners employed. The firing of a blasting charge was eventually resorted to, upon which, according to the report, water poured in like a torrent, flooding the shaft to a depth of 70 feet. This to the great astonishment of the miners who had remained suspended in their bucket awaiting the result of the explosion.
The level of the water in the Pigeon Well was observed to drop several feet and at the time of the paper it had not regained its former level. The year 1835 tried the wells of the Island very severely and the Pigeon Well failed altogether. The level of the water in the barrack well also fell to an apparent rest level of 70 feet. The Fort Regent work commenced in December 1806 was completed in October 1808.
The writer goes on to give an account of an interesting experiment which was performed in the presence of the then Lieut-Governor, Maj Gen Sir Edward Gibbs. A respectable old farmer named Ingouville demonstrated the divining twig to the satisfaction of his Excellency. It may be that this is the first record of any such experiment in the Island.
After this short diversion, which I trust has not been uninteresting, I propose to return to my major theme, a description of the provision and growth of the organised community supply of the Island.
The need and desire for a piped supply had been felt as far back as 1847. In this year a meeting was held, attended by the Bailiff and Lieut-Governor. Although resolutions were passed at this meeting, setting forth the desirability of public supply, some 20 years were to elapse before active steps were taken.
The forerunner of the present company was called the Jersey Waterworks Company, and came into being in 1863. It was blessed with the approval of the States and Parish Assembly of St Helier, and everything seemed set fair for the launch of a sound enterprise. On 20 September 1869 there assembled in St Lawrence Valley a distinguished gathering, to witness and assist in the inauguration of the Jersey Waterworks. Among those present were the Lieut-Governor, the Bailiff, the Dean and the Attorney-General. All these gentlemen made speeches at the repast which followed the turning of the first sod by the Lieut-Governor.
A curious circumstance arose after the departure of the more important guests, for the crowd which had assembled invaded the marquee, seeking refreshment. It is recorded that Centenier Pinel failed to clear the tent and appealed to Capt Dallain, who was in charge of a detachment of St Lawrence Militia, for assistance. This gentleman, acting with military promptitude and spirit ordered the fixing of bayonets. The report says that as many of his men had imbibed freely, a scene of indescribable confusion took place. When at last peace was restored and the invaders repelled, it was found that one unfortunate civilian, whose name is not recorded, had been wounded in the leg.
The works upon whose inauguration we have been privileged to peep were situated near Vicart Mill in Waterworks Valley. They consisted of a pumphouse, a well and a concrete reservoir nearby. The pump house existed until recently, being demolished in 1935. The remains of the reservoir are still to be seen to the West of the road leading to Mont Misere, just before the tum leading to Dannemarche Reservoir. How long these initial works sufficed is not known but the original company later constructed the first works at Millbrook, on the site now occupied.
Again the directors of the company pinned their faith to a well and on the Millbrook site arose a pumping station with a large cast iron service tank near by. Photographs are in existence which show the old tank. This later fell into the hands of Messrs Hunt and was duly demolished and carted away by that firm.
The storage reservoir and all the major works now existing at Millbrook were still in the future. The company looked forward no doubt to a period of progress which, alas, did not materialize. The well supplies proved unsatisfactory in yield and were no doubt augmented from time to time by intake from the St Lawrence stream. To quote from a paper by my predecessor A J Jenkins: "The first attempt to provide a supply was badly conceived. The insufficiency and inferiority of the supply created a prejudice which existed for some time and which it has been difficult to overcome".
Handicapped thus by a bad start the Jersey Waterworks Company went en desastre and the present concern, the Jersey New Waterworks Company, took over in 1882. It acquired all the works just described but immediately realised the grave shortcomings thereof. The policy of seeking to obtain large supplies from wells was abandoned, attention turning instead to the St Lawrence stream, near which the Millbrook site conveniently lay.
No attempt was made to deal with the situation halfheartedly, although matters of capital must have given the then directors some concern. The new works started at Millbrook in 1884 consisted of two slow sand filters, new pumping machinery and a brand new service reservoir at Mont Felard. The filters were of the type proved in hundreds of British and Continental waterworks. The works themselves were well designed, a new system of distribution from the new Felard Reservoir comfortably commanding the bulk of St Helier. These works may well be regarded as the nucleus from which the present system has developed.
It was not long before the need for storage facilities was felt. In 1895 the Millbrook reservoir, the first in Waterworks Valley, was commenced. The dam is partly of earth and partly of masonry. When completed 12 million gallons of water could be stored for use. No alterations to roads were necessary to complete the reservoir, but the valley had acquired the first of its beautifying stretches of water.
1897 found the young company again active when additional filters became necessary. Three new and larger slow sand filters were started and completed in the following year. The filters then constructed are still in use after a thorough overhaul in 1934.
Sixteen years of strenuous building, particularly for a young company by no means prosperous, is not a bad record. But in waterworks practice there is no finality with a growing community. The need for more storage capacity gradually made itself felt, the relentless pressure of increasing demand culminating in the building of Dannemarche Reservoir in the years 1908-1909.
Most of you will be familiar with this reservoir, which lies about 1¾ miles up the valley and about ¾ of a mile from Millbrook. The major work consisted of a mass concrete dam across the valley, a labour containing some 5,000 cubic yards of concrete. The building of the dam necessitated a considerable road diversion, the whole of the road from Vicart to the northern end of the reservoir being built by the company. The completion of Dannemarche placed the company in an excellent position, the new dam holding 28 million gallons and bringing total storage to 40 million gallons of water.
The war of 1914-1918 no doubt interfered with development and the water resources of the company were not seriously taxed until the year 1921, the record year for low rainfall. This year was rightly looked upon as an expected occurrence, but it emphasized that major works could not long be delayed. I use the term long here, in the sense that a waterworks engineer would use it. A short period is anything up to 15 years.
From 1922-1929 development was fairly rapid and the latter year saw the Handois Reservoir embarked upon, to be completed in 1931. The same methods of construction were followed as at Dannemarche, the dam being again built of mass concrete. The capacity of Handois Reservoir is 50 millions gallons, a figure which brought total storage resources to the useful figure of 90 million gallons of water.
In the intervening period Westmount Service Reservoir had been built, the service reservoir at Felard no longer commanding the higher districts of St Helier to which the supply was spreading. Up to the time of building Handois, the slow sand filters at Millbrook had proved sufficient, being increased by the addition of closed type pressure filters in 1926. An experimental plant had also operated from St Peter's Valley, when water was pumped on odd occasions for final treatment at Millbrook. Chlorination was in use at Millbrook as far back as 1921.
With the completion of Handois, the company embarked upon inquiries as to newer modes of treatment, this leading to the construction at Handois of the present rapid gravity filters in 1934. The new plant embraced chemical treatment, precipitation before filtration and sterilization by chloramine. Chloramine treatment was also introduced at Millbrook instead of straight chlorination. The laboratory which started about this time afterwards developed into the highly organized check methods now in use.
After Handois it might have appeared that the search for water resources might rest for some time. But this was not to be, and in 1934 the works at La Hague in the St Peter's Valley were constructed. They consisted of a pumphouse, small reservoir and the necessary line of pipes leading to Handois. Closed pressure filters were installed at Handois to deal with the water from St Peter's valley. These were transferred from Millbrook where they had become redundant.
The last acquisition in the way of water resources was the site in Le Mourier Valley. The works here will follow the lines of the St Peter installation. The engine house and brookcourse and the pipeline are nearly complete. When the dam and completion of machinery installation takes place this station will pump water to Handois and take its place in the supply of the Island's water.
Before leaving the works side to describe how all the various pieces fit together in the whole scheme I should devote some time to the question of distribution. Without being too technical I will try to suggest to you how the distribution system has developed. Leaving out the original works, the new company supplied town from Mont Felard service reservoir with a height of 170 feet above OD. Then the Westmount Reservoir was built (height 220 feet above OD), enabling still more of the town to be covered. All water to these reservoirs required to be pumped from Millbrook.
The Handois site made possible a service reservoir at 250 feet elevation enabling water to gravitate, (without pumping), to Westmount Reservoir. This newer reservoir enabled a better supply to be given to still higher parts of St. Helier.
In addition there have sprung into being five electric automatic booster or repumping stations situated at Westmount, Wellington Road, St Brelade, etc. which furnish supplies to still higher fringe zones. These areas are still developing but even now have duplicate pumping plant ingeniously controlled, to care for any reasonable demand.
In recent years the pipes of the distribution system have practically all been relaid, for which purpose a special concrete lined cast iron pipe has been used. The Town is excellently provided with trunk mains and is superior to many towns on the mainland in this respect.
There are many unique points in the development of Jersey's water supply which are perhaps more apparent to the engineer accustomed to mainland practice, than to the layman in Jersey. There are few places where the water undertaking has to carry out
- Large scale storage
- Filtration and chemical treatment
- Pumping to replenish storage
- Pumping to service
to enable a supply to be afforded. The smallness of the valleys makes the cost of storage reach a figure that would be considered astronomical on the other side. The cost of land alone is interesting. Whereas it is frequently purchased for £5 an acre in Great Britain, for impounding schemes there are many of you who will realise that this figure is rarely possible in Jersey.
And now having sketched out the development of the works so that we all have some idea of them, let me briefly describe how the whole combine to function harmoniously. First of all consider the Handois reservoir and station. The reservoir receives all its water from the St Lawrence streams which lie above and to the north of it. Not all the water is taken in. Sudden rains scour the land and many a heavy shower upon which my friends have congratulated me have in actual fact meant the turning of the stream to waste with consequent actual loss of water. Further supplies reaching Handois from St Peter's Valley and Le Mourier will contribute additional water when completed. It should be noted that water from the two additional stations referred to is filtered before reaching the Handois reservoir.
First treatment at Handois consists of the addition of two chemicals, soda ash and sulphate of alumina. Soda ash is added at two points. These chemicals cause the larger part of the impurities and colour to be deposited into a large tank called the sedimentation tank. Remaining impurities group or flock together to be removed by the rapid gravity filters which follow. After filtration a small dose of ammonia is added followed by the addition of a dose of chlorine. The combination of these is called "chloramine" which is a sterilant, contact with which destroys all germs causing water borne disease. A small amount of chloramine is left in the water to safeguard it in the mains and storage tanks until required for use.
At Millbrook the filtration is by the slow sand method, after which ammonia and chlorine gas are added as at Handois to complete the purification process. The sometimes long period during which untreated water remains in the storage reservoirs before being drawn for use contributes largely to the purification processes which follow. When the water finally leaves the works on route for the consumer, it is absolutely sterile and safe for use for any purpose.
Checking the purification processes at all points is a rigid system of chemical observations and bacteriological examination. Daily examinations of water from each originating source are made in the company's laboratory, and each week check samples are submitted to eminent London bacteriologists. There is no concern of similar size in Great Britain with its own system of bacteriological examinations. Jersey supplies are drawn from intensely cultivated areas. Protection by laying the land barren, as is done in some parts of Great Britain, is impossible, so that an elaborate defence system has required to be built. Jersey water is pumped to the impounding reservoirs, stored, filtered, sterilized and often repumped twice before reaching the consumer, the compactness of the Island and the smallness of its valleys contributing to the problem. The need for future extensions has always been borne in mind, and the existing system is planned to form part of an harmonious whole, when the time arrives to write finis to the story of further developments.