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Stone Drains

earth, drain and box

STONE DRAINS.

In localities where stone suitable for such purposes exists along a roadway it is common and often econ omical toĽ use stone drains for purposes of under drainage.

Blind Drains: For short lengths, where it is only necessary to provide a permeable path for a small quantity of water to escape, blind drains may be used. They consist of ditches cut into the soil and filled at bottom with fragments of stone, the trench then filled with earth. Care should be taken that the top of the stone is protected, so that the earth may not be washed into the stone and stop the drain; a little small-sized stone or gravel on top, or a light layer of brush or sod, to hold the earth until it has compacted, is useful. Such drains have frequently proven quite efficient when used where the requirements are not too great.

Box Drains. Where suitable stone is plenty and cheap, a box drain may be built. This consists of a rectangular box formed of fiat stones at the bottom of the trench, which is then filled with earth. This box may be very roughly built, and it is desirable when stone or gravel is plentiful to fill immediately over the drain with such material, to protect it against the entrance of earth and assist in leading the water into it. Figure 6 shows a section of such a drain as con

structed to intercept a seepage of wafer in stiff reten tive material. In ordinary soil there would be no advantage in filling the trench so full of stone. The construction shown in Fig. 7 is also sometimes used, and is cheap and reasonably efficient.

The size of opening in a stone drain must be consid erably larger than that in a tile to carry the same quantity of water, the construction usually being very rough, and the resistance to flow greater. Drains of this type are used in many localities where materials are available for building them, although their use is growing less, due to the fact that porous tile costs so little and tile drains are so easily and cheaply con structed.