Wells and Subterranean Water Supply.
(Continued from last week.)
Another point in connection with subterranean water deserves a word as we pass by. It is frequently asserted and maintained that subterranean water obtained from either open or driven wells in the immediate vicinity of rivers or streams is the natural and lateral infiltration from the latter, cither through its banks or bed. It seems to us that a moment’s reflection on the nature of things will challenge this theory, from the fact that is universally known that every stream is inclined to deposit more or less mud or silt in its bed and pass along in a practically impervious channel. Now, should there be any holes or springs in the bottom of the river or stream, would it be natural for the river waters to flow out) If this were the case would not our rivers be likely to lose in volume rathei than to gain as they proceeded on their course? And as our streams are almost invariably found in the lowest points of our valleys or water sheds, does it not follow that the waters from the surrounding territory, which is presumably higher, should be fed by the natural head which the elevation of the surrounding country would give, and being held down in many cases by an impervious soil preserve the pressure upward? This is the theory, but practice is better. For example, the author could name “a stream where this assertion was made, and to disprove it a well was dug along the shore of the river, in which the water on pumping maintained a level about four feet lower than the water level in the river following a suitable operation of the pumps.” When this was the case the earth over the whole water level on the river side was entirely dry, and extending it laterally until within less than two feet of the bank of the river caused no inflow of water from the bed of the river into the well, and this last few inches of soil proved itself to be dense and impervious to water, Such examinations have and often will prove that there is no connection between the gravel beds of a valley and the stream which drains it, but that the former is fed entirely from an independent underground source, many times flowing parallel to the river through the gravel and following in a general way the slope of the lund.
The author could name in his own experience several like cases, notably one at Watertown, Mass., where we put in a well approximating twenty feel from the river on a low bank, the surface of which was scarcely 18 inches above low water, and subject to overflow at all periods of flood. The mate~™Yterafew feet below the surface was large, coarse gravel, extending to the river bank, and apparently should have offered the freest of passages for the water from the river to the wells, the water level in which, when we were pumping, was from six to nine lect below the level of the river level. Vet, under analysis, these waters had little in common ; the temperature of the river water was in the vicinity of seventy degrees in midsummer and of the wells but a trifle over lifty. These wells were pumping from half to three-quarters of a million gallons per day. A bacteriological examination of the waters showed the river water to have 2,700 bacteria to the cubic centimeter, and the water from the wells but three. This should be pretty conclusive proof of non-connection or contamination. And it is a common occurrence with us to put down wells in the vicinity of ponds and streams and have a difference of fifteen to twenty degress in temperature in midsummer and midwinter which could not possibly be accounted for by the passage of the water did it come direct through so short a passage as that between the river or stream to the well or wells, for if a large quantity of water of higher or lower temperature passed through it would undoubtedly in a very short time reduce the earth by its modifying influence to an equal temperature, so that the two waters should be alike in this respect. And it should not be forgotten that this question of temperature of subterranean water is one not to be overlooked when considering it as a source of supply, for in summer it will nearly always be found vastly cooler than water fromasurface source, which is an important and desirable consideration iu the average community. And the author believes, taken as a whole, where subterranean supplies are possible, they are, as a rule, cheaper than the average supply of an equal quality and quantity of water taken from surface sources, for it is nearly always the case that a city or town of any importance will usually have to go some distance away for the purpose of obtaining a satisfactory and unpolluted source.
Now, having considered some of the advantages and made an appeal for subterranean water, it is well to add a few of the popular objections thereto, several of which in regard to permanence, quality, quantity, etc., have already been treated, but the chief of which in the eyes of the average community or individual is the objection that such waters are often hard. Considering this it is well to remember that it is difficult to obtain a water that is highly desirable for drinking purposes and at the same time equally desirable for manufacturing. When we look over the field, however, it seems to us that the health of the community deserves primary consideration. There are comparatively few lines of manufacturing save dyeing and a few chemical processes or work involving cooking or something in which the steam comes in contact with that which it would damage, where the trouble with the average hard water could not in most cases be practically connected, by the addition of a little kerosene oil, fed through a common sight feed luoricator. I’he writer is inclined to believe this a very desirable and almost costless boiler compound to cure either medium or fairly hard waters.
Now, while the writer may have appeared slightly enthusiastic on the subject of subterranean water, yet he is fully mindful of the many difficulties to be encountered in obtaining such supply. T he old and grossly erroneous idea that if one goes down deep enough in any given locality he is sure to get water should have been exploded long ago, but, alas, is not. If persons seeking supplies in the lower stratas where artesian wells have to be resorted to would consult geologists and obtain an accurate knowledge of what is likely to be encountered beneath the surface, they would sometimes save themselves a large expenditure, for an artesian well has its necessary requirements as well as the driven well or surface stream. There must be a roof and floor between which such waters must be confined if they are to be found in any quantity, though there is also usually existing chance of striking a fissure which may furnish one good well, though the likelihood of striking another is exceedingly remote; and the author could cite a case where a single artesian well gave as much as seven more, and a ten foot shaft sunk in the same locality for the purpose of increasing the yield, as there was only so much water there and one robbed the other. The same is practically true of wells in the upper strata. And the writer knows of few things, (except in obvious cases of the existence of a supply,) that requires more judgment and experience than the location of a large subterranean source of supply for a city or town, and many of the failures to obtain water are due to lack of knowledge, forethought, or experience. And many, again, to the lack of the application, the proper appliances or devices to fit the conditions. Practical well men and others are too prone to the practice of trying to make their favorite well point strainer, open well, or other appliance, do duty under all conditions, which is like trying to drive a square plug in a round hole and make a tight joint.
I he writer has been called to several places in the last two years, where a number of attempts by various people had been made to obtain a water supply and failed, and has located from one to five million gallons within a hundred feet of abandoned test wells which had been put down and the ground declared useless or impracticable for water supply. It is an apparent fact that in well work one has to deal with conditions as they are found and with materials as nature placed them. Consequently we have to make our methods subservient to this great mistress, and if we do not we are almost sure to fail. In locating the subterranean water supply,.great care should be taken to ascertain the available water shed with direction of its flow and the character of the material through which it passes and in which the plant must be located.
The writer is an ardent advocate of the driven or tubed welt, believing it in nearly all cases to be superior to an open well for the reason that in the first place an artificial head can be created by suctions in addition to any natural head due to the lowering of the water plane. As the open wall is merely a reservoir into which the water runs by natural gravitation, when the lever is lowered you have only gravitation to supply the deficiency and what you have taken away. The bottom of the open well or filter gallery is likely tosilt up and the flow to diminish from the fact that such wells can rarely be sunk to any great depth where much water exists in the first few feet, thus reaching only comparatively the top of the water bearing strata instead of penetrating it, which is the natural desideratum. And likewise being on the .wrong principle insomuch as they present their contact with the water strata on a plane and, on top when the rational method is vertical and by pertration.
Much could be said in reference to the location and fit condition for successful well plants, but so much depends upon surrounding circumstances that no given set of rules or suggestions could be made to satisfactorily cover the ground and be a reliable guide to one not well or thoroughly versed by experience in such matters.
There are many more points which the writer would like to cover on this interesting subject, but he feels that he has al ready taxed the patience of his listeners, and, as barely time remains for the mechanical details of putting this article on paper, he will close with a brief description of a plant recently designed by him and built by the Hydraulic Construction Company for the New Utrecht Water Supply Company, New Utrecht, Long Island.
The writer was called in a little over a year ago by the president of the above company, which was at the time suffering seriously on account of inadequate supply. Their then plant consisted of some eight open wells about six feet in diameter and approximating 35 feet in depth, constructed about 1886. These wells were of the ordinary type with a brick curb sunk to the depth above named and with a few large stones thrown in the bottom, but through which the finer sands had run and largely silted them up, reducing the yield so that under heavy draught the suction would be bad and the level lowered to the limit of the pumps. The president of the company was a great advocate of open wells and after our first interview employed a party to sink one of about 25 feet in diameter in the vicinity of the others. The contractor began the work, but after some weeks was compelled to abandon his attempt on account of the fineness of the material and water, which prevented him from carrying down his curb more than about 10 feet, as the sand ran in so that he could not make any practical progress. The result was, he gave up and we were again consulted. This time, mindful ol the president’s predilection in favor of open wells, we designed an atmospheric well to use in combination with his open wells which would not reduce the water level abnormally in the vicinity of the tube well plant, and, therefore, perhaps take the water away from and render his open wells useless. As they were in serious straits by this time for water, we were asked how long it would take us to put in wells to yield a million gallons, which we agreed to supply in ten days and actually finished in nine, increasing this amount up to nearly two million in sixteen days, which the author believes is about the quickest work for the quantity of water obtained on record. Having relieved their immediate necessities, we proceeded to put in the permanent plant of twenty 6-inch wells. These wells were designed after the general style of the annexed blue print. The wells proper were of 6-inch iron tubing, equipped with a special spiral copper non-corrosive strainer of 7 1-2 inches in diameter, as shown in the drawing, and designed by the writer. These strainers averaged aDout 6 feet long and were sunk to a depth of about 58 feet below the surface of the ground and presented a suction area about 50 times greater than a cross section of the 6-inch pipe. A flange was screwed on the upper end of the 6-inch pipe and on this was placed a chair with four frets on the bottom and with an aperture through it large enough to drop a 4-inch suction pipe inside, which pipe was sunk down to about the top of the strainer. This 4-inch receiving pipe had only a relative proportion of the area of the strainer of xoo to 1, and the result of such liberal proportion was almost beyond the writer s expectation. ‘This suction pipe was connected with a 6-inch well head and that by a ninety degree elbow to a 5inch cross section running at forty-five degrees’ angle to the main and connected thereto by a flanged Y, intersected by a gate valve, so that each well could be shut off without interfering with the operation of the plant. The suction main is 12 inches in diameter and the wells are located on a square 20×25. An expanded joint entered the receiver which had four 16-inch flanged openings, only two of which, however, were used and the others blanked. The receiver was a single casting, weighing some 6,000 pounds and being 5 1-2 feet in diameter and 7 1-2 feet high, covered with a manhole 18 inches in diameter, furnishing access for the removal of sand or for any other purpose. The joints and connections throughout the plant were flanged and bolted together with the intervention of rubber caskets. The wells were thoroughly pumped with a centrifugal pump for from two days to a week before being connected into the line, as the sand was quite fine and it took some time to get them clear. A 16-inch main approximating from 500 to 600 feet in length connects the receiver with the engine house, through which the water is pumped.
This is a very brief and inadequate description of a well plant which the writer believes is as successful and modern in proportio’n and design throughout as anything recently done. The results are equally gratifying, as every well on the plant will pump nearly 400 gallons of water, or approximately so, per minute, and the writer is advised, though he has not visited the plant for nearly a year, that it is giving perfect satisfaction. The pumping capacity of the works is approximately 4.000,000 gallons, consisting of two 2,000,000 Worthington pumps, one of which is a high duty ; and we are told that running days they run on about a 7-inch vacuum, and that the water is never lowered more than 23 inches, and that on the average consumption during the day it is only reduced 9 inches. And although the plant is operated under the Holly or direct system, during the night the water recovers, so that in the morning it is found to be only 4j£ inches below the normal. The water is of an exceptional character, being the most palatable, the author thinks, he has ever tasted, and so seems to be the general consensus of opinion in regard to its quality. The wells are located in an excavation some twenty feet deep, the material having been taken out some time ago and used for filling in and street purposes in Brooklyn. The writer can only approximate the yield of this plant, but is inclined to believe it would readily give six or eight million gallons, and that for low friction, high efficiency and quality of water it is worthy of notice. The quality of the water may be all the more surprising to some of our inland friends when it is remembered that this plant is located within a mile substantially of the ocean at Coney Island and within a quarter to a half a mile of an inlet or arm of Jamaica Bay.
The writer begs leave to offer his apologies for so incomplete and incoherent a paper, which has been dictated at a single sitting, without revision, for all of which please accept the apologies of an earnest brother member.
(To be continued)