To the Board of Commissioners of the Central Park:
Gentlemen,

By a resolution of the Board, communicated to me on the 24th of September, I am called upon to report to you “a comprehensive plan of draining for the Central Park, and at what time such work may be advantageously commenced.”

Owing to the exceedingly diversified character of the ground, the great amount of rock, both above and below the surface, with which it is encumbered, and its numerous springs, hidden and superficial, a detailed plan of drainage for the Central Park could only be formed after such a careful study as a proper attention to the ordinary duties of my office forbids me at present to give to the subject. The depth and direction of the drains must be, in many cases, also, adjusted to the elevation of the brooks, cascades, and standing water, which will be established solely on artistic grounds, as well as to the roads which may be laid out. Until, therefore, a complete plan of the Park shall have been definitely determined on, I think it would be unwise to carry a consideration of the drainage-plan beyond the adoption of certain fundamental rules, to which even the landscape design should be subordinate.

Among the questions which may with advantage be immediately considered, the following occur to me:

First.—To what extent should the Park be drained?

Second.—By what form of drains?

Third.—At what depth?

Fourth.—Can the drainage be most economically executed by contract or by days work?

Construing the requisition of the Board as asking my judgment upon these preliminary points, I reply to the first: That I consider it of the utmost importance that the drainage of the Park should be “thorough” in all its parts; that not a rood of the soil on which either grass, trees or shrubs are expected to flourish, should be exempt from the direct draught of a subterranean tube, rapidly conducting the superabundant water it collects to some lower point, and eventually beyond the limits of the Park.

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The cost of such drainage will be great. $30,000, in addition to the expense already incurred in indirect superficial drainage, would be a moderate estimate for it. I have been repeatedly asked, in a manner which indicated that the proposition would be generally considered preposterous, if I thought that the high table-land and the slopes beyond it, lying adjoining and south east of the reservoir, would be benefitted by artificial drainage, and I presume there will be a difference of opinion in the Commission, if not as to a certain degree of benefit to be derived from thorough-draining soil so situated, at least as to the economy of so great an expenditure as will be necessarily incurred to obtain it. Near the highest part of this elevated land are some large rocks, the earth around which had been excavated preparatory to their removal, about three weeks since. Some of the cavities thus formed remained open until last week, when I made an examination of the soil with reference to this Question. Nearly two weeks had passed since rain had fallen, at which time the earth at the bottom of the holes was in the loose condition in which it had been left after the action of the pick and spade. Nevertheless, it was in every case moist and plastic. In some of the holes pools of water still stood, and it was evident that in no case had the rain-water to any considerable extent passed off by filtration. The earth taken from the bottom was in a condition resembling a stiff paste; that a little above it, from which the water had recently evaporated, was like half-dried putty; but still higher-above where the water had collected—in the perpendicular walls of the excavation, the earth, though composed, probably, of exactly similar particles, had a crumbling and porous appearance. It broke in flakes, and was pulverised under pressure; that below could only be removed in clots and lumps, and was tenacious under pressure.

This is simply an extreme exposition of the different character of the subsoil of the high land of the Park in a thoroughly drained, and in its ordinary undrained, condition. In the one case it is easily penetrable by the roots of plants, and constantly ready to yield them the materials of their growth; in the other it is cold, inert, and not merely useless, but at all times and under every condition of the atmosphere, positively baneful to the health of the plants growing on the surface. When surcharged with moisture, it is tenacious, and holding water like putty, the soil above becomes a mere mire, suitable only to the growth of swamp-plants. During a season of hot drought, it hardens so that it can hardly be broken up by a pickaxe, and in this state it interposes a hydraulic floor between the thirsty roots in the surface soil, and the moisture which would otherwise be afforded them by capillary attraction from the cool earth below.

The action of under-drainage is primarily to remove superabundant water, but in the process of doing so it produces a mechanical change in the structure of the subsoil, the value of which as affecting fertility is secondary only to its sanitary influence. This mechanical improvement is effected somewhat slowly in clay soils; it may be two years before it becomes of consequence, but when secured, it is more valuable than every thing that can possibly be effected[96] without it by surface tillage or even by the subsoil plow or spade trenching. I have no doubt that the thorough draining of the soil will eventually be considered essential to the beauty, as well as to the salubrity, required in the Park, and if neglected at this period it will be secured hereafter, when, from the improvements which shall have been made on the surface, and the difficulty of connecting a complete system with such an arrangement as will otherwise be adopted, its cost will be greatly increased. So essential to the Central Park, so fundamental to its construction, do I consider a perfect under drainage to be, that if an expenditure of all the funds under the control of the Board should be required to secure it, I should think it the duty of the Board to make this use of them, leaving, if necessary, those operations which can only be executed satisfactorily after such a preliminary operation, to a future generation. Nearly all the subsequent work contemplated can not only be executed with much better results but also much more cheaply after the ground is completely, and at all points, freed from superabundant moisture.

A necessity of all modern gardening, there is abundant reason for asserting that thorough-drainage is a peculiar and special necessity for the site of the Central Park. It is believed that nearly one-seventh of the laborers employed upon it have been attacked with intermittent fever during the last fortnight. The cause of this is unquestionably to be found in the tenacious and unfiltrating condition of the soil, a condition which will be completely changed by thorough-drainage.

II. The form of drains:

Experience proves that earthenware tubes of from one inch calibre upwards, according to their proximity to the surface, and of the parallels when [97] laid, to one another, and in sections of from ten to fifteen inches in length, form the cheapest and most secure channels of drainage, and these, upon examination of evidence readily obtained, will undoubtedly be recommended by your Committee on the subject.

III. The most desirable depth at which to lay these tubes:

When the modern system of thorough-drainage first came extensively in use, the depth generally adopted was three feet, and to this custom the Drainage Act of Great Britain—by which large sums were loaned by government to encourage an improvement which has since doubled the average product from agricultural labor in that kingdom—required all who took advantage of it to conform. Subsequently, however, there arose a school of agriculturalists, at the head of which was Mr. Josiah Parkes, Consulting Engineer of the Royal Agricultural Society, who, on certain theoretical grounds, propounded the rule that drainage-tubes should never be laid at less a distance than four feet from the surface. Making this gentleman’s acquaintance when I was in London, in 1851, he gave me letters to several superintendents of public parks and bailiffs of noblemens’ estates, the drainage of which he had planned. In visiting them, I endeavored to ascertain more especially the effect of the system of deep drainage in a time of drought. For this purpose, I was fortunate in the opportunity of seeing several of them in an unprecedentedly dry season. I cannot say that the result equalled the expectations which in theorizing on the subject I had been led to form. Phoenix Park, a public pleasure ground of 400 acres, near Dublin, every part of which had been recently underlaid with tile, at a depth generally of five feet, was far from exhibiting the proverbially vivid verdure of the Emerald Isle, nor could I anywhere obtain conclusive statistics establishing any superiority for the system, in this respect, as I had hoped. Its advocates observed justly that this might be attributed to the recency with which the deep drains had everywhere been made, and the limited time they had had in which to produce the thorough mechanical change in the soil which was to be hoped from them. But the result of all my observations and enquiry at this time, and subsequently, obliges me to state that all theorizing aside, the weight of evidence from experience seems to me yet to be in favor of more frequent and less deep drains for heavy clay lands, than have recently been advocated by many eminent agricultural authorities, both in England and our own country.

The possibility, however, of the roots of trees crowding a drain-tube out of place, or of their fibres entering the crevices between the sections and occupying the interior, is a conclusive reason, in my judgment, for adopting the rule with regard to all parts of the park in which, according to the plan that shall be [98]finally accepted, masses of trees are to stand, that no drain-pipes shall be laid nearer than four feet from the surface, except in certain exigencies of rock and surface-water, and then only after special consideration and approval by the Chief Engineer.

In all open glades, on the parade and play-grounds, and wherever there are no trees, roads, or other occasions for conducting the water at a greater depth, I should recommend tile-drains at a depth, so far as convenient, uniformly, of three feet, never less, and [a] distance apart of fifteen. These propositions will be objected to by the partisans of different theories on widely different and inconsistent grounds, but where it cannot be afforded, or would not be right, to expend money looking to uncertain results, I believe the most general experience of practical men justifies them.

IV.—Preliminary to any work, a plan of drainage should be sketched without regard to hidden rock or the minor undulations of the surface. A careful subterranean survey by means of sounding-rods, and occasionally by digging test-holes, should then be employed to ascertain, as far as possible, the practicability of following the provisional lines of this sketch. A modified plan should then be drawn according to the data obtained by this subterranean survey. I have no question, however, that, as the trench-digging proceeded, it would still be found economical to depart very frequently from the lines of the last, or revised, plan. Rocks would be encountered which had not been discovered in the survey, and divisions between and depressions across rocks would be found which had not been suspected by the surveyor. To take proper advantage of these circumstances, the constant attendance of an intelligent and experienced person, who should be allowed discretion to vary from the plan as it should seem to him economy required, would be necessary. Very delicate questions as to how far a certain deviation from the plan, and consequent hazard of loss of the expected advantages from the work, would be justified by obstacles encountered, would momentarily arise. It is doubtful, for this reason, if it would be best to previously adopt explicit specifications for the drainage operations, and I think it can hardly ever be advisable to have any work extensively done by contract unless the specifications for it are very explicit and capable of being stringently enforced.

It is hardly possible to estimate the cost of the labor required for the drainage of the park with much justifiable confidence. Hence the chances are either that the contractor would find himself losing money more rapidly, and therefore, taking advantage of the necessarily loose specifications of the instrument of contract, would insist on doing his work very inefficiently, forcing the Commission to some compromise to his advantage, or, that he would be paid a sum much larger than it would cost the Commission to drain the park by days-work. Some parts of the work would require constant and vigilant inspection, by trustworthy officers of the Commission, to secure their safe execution under a contract; especially so, the laying of the tile and the filling immediately upon it. In one case under my observation where this had been left to a contractor, [99]

[100] the drains not working satisfactorily, an exploration was made and it was found that, during a temporary absence from the field of the proprietor, tile had been thrown into the trench helter-skelter and hastily covered out of sight, thus wasting a large proportion of the expenditure for the whole work. A decision upon this question however, can be made much better after such preliminary action as I have suggested. The survey for the purpose, if I may be allowed to advise the Board, should be commenced immediately, before the ground is hardened by severe frost. Its result, to a certain extent, will be needed in order to form a well-digested plan for the next season’s work on the park—not merely for the drainage but for any other work. It is possible that modifications of the landscape and road-designs for the park may be suggested by it.

It is not improbable also, that in the course of such a subterranean examination of the site for the park, a valuable deposit of clay, adapted for the tile making, may be discovered. In this case it might be best for the Commission to manufacture the tile required for the park upon the ground. It will otherwise probably be brought from Albany, and as it is a bulky article, the freight, and cartage expenses, will be a large item in the whole cost of drainage. I should roughly estimate it at $5000. A drain-tile machine, to be worked by hand and capable of turning out 1000 feet of the smallest pipe per day, would not cost over $75, and the necessary temporary sheds and kilns for the purpose would be inexpensive.

The first thing to be done in forming the principal drives of the park will be to construct deep road under-drains, one on each side, on their exterior lines. To obtain the effect of seclusion and to avoid as far as practicable an outlook from them upon the high-graded streets which will surround the park, these drives will probably be laid out as low as shall be found convenient. Their concurrent drains will therefore be below the general depth of the park drainage and will readily become in many cases the leading or main drains for it. Until, therefore, the design by which the course of these drives will be designated is finally adopted, I trust the Board will agree with me that it is impracticable to extend a plan of drainage for the park beyond the few important preliminary points, my views upon which I have now submitted.