Farm drainage / The Principles, Processes, and Effects of Draining Land with Stones, Wood, Plows, and Open Ditches, and Especially with Tiles

by Henry F. French

Albert Model Farm, Glasnevin, Dublin,
January 31, 1859.

To the Hon. Henry F. French, Exeter, N. H.:

Sir:—Your queries on land-drainage have been too long unanswered. I have now great pleasure in sending you, herewith, my views on the points noted. * * *

Pray excuse me for the delay in writing. I am, sir,
Your obliged and obedient servant, William Boyle.

LAND DRAINAGE—REPLIES TO QUERIES, ETC.

Introductory observations. Ireland contains close on to twenty-one millions of acres, thirteen and a half millions of which were returned as "arable land," in 1841. By "Arterial" and thorough-drainage, &c., effected through loans granted by government, the extent of arable land has been increased to fifteen and a half millions of acres. The "Board of Works" has the management of the funds granted for drainage and land improvements generally, and competent inspectors are appointed to see that the works are properly executed. The proprietor, or farmer, who obtains a loan may, if competent, claim and obtain the appointment of overseer on his own property, and thus have an opportunity of economically expending the sum which he will have to repay (principal and interest) by twenty-two installments. The average cost of thorough-drainage, under the Board of Works, has been about £5 per statute acre. In 1847, when government granted the first loan for land-drainage, tiles were not so easily obtained as at present, nor was tile-drainage well understood in this country; and the greater part of the drains then made—and for some years after—were either sewered with stones, formed into a conduit of various dimensions, and covered over with finely-broken stones, or the latter were filled into the bottom of the drain, to about one foot in depth, as recommended by Smith, of Deanston. The dimensions for minor drains, sewered with stones, were, usually, three and a half feet deep, fifteen inches wide at top, and three to four inches wide at bottom (distance apart being twenty-one feet); and the overseer carried about with him a wooden gauge, of a size to correspond, so that the workmen could see at a glance what they had to do. These drains are reported to have given general satisfaction; and they were cheaply made, as the stones were to be had in great abundance in almost every field. On new land, trenching was sometimes carried on simultaneously with the drainage; and it very often happened that the removal of the stones thus brought to the surface, was very expensive; but they were turned to profitable account in sewering drains and building substantial fences. In almost every case the drains were made in the direction of the greatest inclination, or fall of the land; and this is the practice followed throughout the country. Some exceptions occur on hill-sides, where I have seen the drains laid off at an acute angle with the line of inclination. It is not necessary that I should explain the scientific reasons for draining in the direction of the fall of the land, as that point has been fully treated of, and well illustrated, in your article already referred to. I shall now pass on to the Queries.

Depth of drains, and distance apart. There is still a great diversity of opinion on these points, and particularly in reference to the drainage of stiff clay soils; some of the most intelligent and practical farmers in this country hold to the opinion that, on such soils, the maximum depth should not exceed three feet, and the distance apart sixteen to twenty feet. On clay loams, having a subsoil more or less free, the general practice is, to make the drains three and a half to four feet deep, and at twenty-one to thirty feet apart. On lighter soils, having a free subsoil, four feet deep and forty feet apart are the usual limitations. This farm may be taken as a fair average of the land in Ireland, as a test for drainage; the soil is a deep clay loam; the subsoil a compact mixture of strong clay and calcareous gravel, almost free from stones. Thirty miles of drains have been made on the farm, the least distance apart being twenty-one feet, and the greatest distance thirty feet; the depth in every case, three and a half to four feet for minor drains. This drainage has given the greatest satisfaction; for although the greatest part of the work was performed by the Agricultural pupils, in training here, we have not had occasion to re-make a single drain, except in one instance, where the tiles got choked, and which I shall explain hereafter.

Tiles: Size, Shape, Draining, Capacity, &c. We use circular pipe tiles, of inch and a half bore, for all parallel drains whose length does not exceed one hundred yards, and two-inch pipes for any additional length up to one hundred and fifty yards, the greatest length, in my opinion, a parallel drain should reach before discharging into a main or sub-main drain. We do not find it necessary to use collars on this farm, as we have firm ground to place the tiles on, and we can cut the drain to fit the tiles exactly. As regards the size of tiles for main and sub-main drains, that can only be regulated by the person in charge of the drainage at any particular place, after seeing the land opened up and the minor drains discharging. As a general rule, a circular pipe of three inches internal diameter will discharge the ordinary drainage of five or six statute acres, and give sufficient space for the circulation of air. It should be observed, however, that this applies to a district where the annual rain-fall is from twenty-six to thirty inches, that of all Ireland being about thirty-five inches; besides, we have not the immense falls of rain in a few hours that occur in other countries. All these points should be carefully considered in estimating the water-way for drainage. I have said that collars are not used with the tiles on this farm, as the bottom of the drains is quite firm and even; but, where the bed for the tile is soft, and the subsoil is of a shifting nature, then collars should be used in every case. Collars cost about half the price of tiles, which they are made to connect, so that the use of them adds one-third to the expense of the sewering material; and, as I have already pointed out, I think it quite unnecessary to use them where the subsoil is firm, and where the drain can be bottomed to fit the tile. Where large pipes are not to be had conveniently for sewering main or sub-drains, I find a proportional number of pipes of lesser diameter to answer perfectly. It is very desirable to provide branch pipes for connecting the minor with the main drains. The branch should be socketed to receive the end of the last tile in the minor drain, and the point of attachment to the main pipe may be on the top or on the side of the latter. If the branch be made to lead the water into the side of the main pipe, then it should join the latter at an acute angle, that both streams may meet with the least possible opposition of forces.