Draining for Profit, and Draining for Health. George E. Waring
10
| TABLE No. 2 | |
|---|---|
| Deg. | Feet. |
| 5 | 8.716 |
| 10 | 17.365 |
| 15 | 25.882 |
| 20 | 34.202 |
| 25 | 42.262 |
| 30 | 50.— |
| 35 | 57.358 |
| 40 | 64.279 |
| 45 | 70.711 |
| 50 | 76.604 |
| 55 | 81.915 |
| 60 | 86.602 |
| 65 | 90.631 |
| 70 | 93.969 |
| 75 | 96.593 |
| 80 | 98.481 |
| 85 | 99.619 |
With the maps before him, showing the surface features of the field, and the position of the under-ground rock, the drainer will have to consider the following points:
1. Where, and at what depth, shall the outlet be placed?
2. What shall be the location, the length and the depth of the main drain?
3. What subsidiary mains—or collecting drains—shall connect the minor valleys with the main?
4. What may best be done to collect the water of large springs and carry it away?
5. What provision is necessary to collect the water that flows over the surface of out-cropping rock, or[pg 058] along springy lines on side hills or under banks?
6. What should be the depth, the distance apart, the direction, and the rate of fall, of the lateral drains?
7. What kind and sizes of tile should be used to form the conduits?
8. What provision should be made to prevent the obstruction of the drains, by an accumulation of silt or sand, which may enter the tiles immediately after they are laid, and before the earth becomes compacted about them; and from the entrance of vermin?
1. The outlet should be at the lowest point of the boundary, unless, (for some especial reason which does not exist in the case under consideration, nor in any usual case,) it is necessary to seek some other than the natural outfall; and it should be deep enough to take the water of the main drain, and laid on a sufficient inclination for a free flow of the water. It should, where sufficient fall can be obtained without too great cost, deliver this water over a step of at least a few inches in height, so that the action of the drain may be seen, and so that it may not be liable to be clogged by the accumulation of silt, (or mud,) in the open ditch into which it flows.
2. The main drain should, usually, be run as nearly in the lowest part of the principal valley as is consistent with tolerable straightness. It is better to cut across the point of a hill, to the extent of increasing the depth for a few rods, than to go a long distance out of the direct course to keep in the valley, both because of the cost of the large tile used in the main, and of the loss of fall occasioned by the lengthening of the line. The main should be continued from the outlet to the point at which it is most convenient to collect the more remote sub-mains, which bring together the water of several sets of laterals. As is the case in the tract under consideration, the depth of the main is often restricted, in nearly level land, toward the upper end of the flat which lies next to the outlet,[pg 059] by the necessity for a fall and the difficulty which often exists in securing a sufficiently low outlet. In such case, the only rule is to make it as deep as possible. When the fall is sufficient, it should be placed at such depth as will allow the laterals and sub-mains which discharge into it to enter at its top, and discharge above the level of the water which flows through it.
Fig. 10 - STONE PIT TO CONNECT SPRING WITH DRAIN.
3. Subsidiary mains, or sub-mains, connecting with the main drains, should be run up the minor valleys of the land, skirting the bases of the hills. Where the valley is a flat one, with rising ground at each side, there should be a sub-main, to receive the laterals from each hill side. As a general rule, it may be stated, that the collecting drain at the foot of a slope should be placed on the line which is first reached by the water flowing directly down over its surface, before it commences its lateral movement down the valley; and it should, if possible, be so arranged that it shall have a uniform descent for its whole distance. The proper arrangement of these collecting drains requires more skill and experience than any other branch of the work, for on their disposition depends, in a great measure, the economy and success of the undertaking.
4. Where springs exist, there should be some provision made for collecting their water in pits filled with loose[pg 060] stone, gravel, brush or other rubbish, or furnished with several lengths of tile set on end, one above the other, or with a barrel or other vessel; and a line of tile of proper size should be run directly to a main, or sub-main drain. The manner of doing this by means of a pit filled with stone is shown in Fig. 10. The collection of spring water in a vertical tile basin is shown in Fig. 11.
Fig. 11 - STONE AND TILE BASIN FOR SPRING WITH DRAIN.
5. Where a ledge of shelving rock, of considerable size, occurs on land to be drained, it