DRAINAGE BY EXPLOSIVES.

Dunstan Times, Issue 2961, 31 March 1919, Page 3

DRAINAGE BY EXPLOSIVES.

Ono who has learned his subject at the front has written to a Home paper with reference to the reclamation of entirely unproductive swampy and hogg.V lands by drainage by the aid of explosives. Thus, be says, may they be made “as fertile and rich as those alluvial soils of the Nile, where Egypt’s plenteous crops are raised.” He adds: Ditching the land by means of dynamite is a speedy and labor-saving method of draining the swamps, and because of this it is also essentially a very cheap one. There are many thousands of acres of land that cannot be tilled owing to a river or stream following a circuitous route, which by means of explosives could be readily straightened. and these areas reclaimed for cultivation. There are two methods employed in blasting a ditch, the one for dry soil, and the other for wet earth. In the former case, holes are put in between two and three feet apart, and are connected up to the exploder, or battery, and all fired simultaneously, while in the latter case the holes are placed nearer together and contain larger charges, being fired by a fuse ignited in the centre charge, this being sufficient to ignite the charges on either side, and so continue all the length prepared.

Holes in dry land require well tamping, but those in swamps and under water fill with mud and water and do not require further tamping to make the explosive do its work. Of course, ditches may be made any width by adding one or more extra rows of holes, and the grading of a ditch thus made can quite readily be accomplished by altering the depth of the holes very slightly, in the direction in which the dip is required. An inch in a hundred feet is sufficient fall. The depth of the hole should be about six inches less than the required depth of the ditch, and it may be said that deep ditches will give infinitely better results than shallow ones.

Swamps are usually to be found on the lowest ground, and exist because the water is held by a hard, impervious stratum below the top soil, and it is necessary that this hard layer or stratum should be penetrated and fractured by the explosives, so that drainage may be effected. If this “hardpan” or impervious stratum lies directly upon the rock the hole should be bored through it so that the explosive will lie upon the rock and tend to fracture and cause fissures in it. but usually beneath

it will be found a pervious soil, which will quickly drain the swamp. As regards cost, ditching with explosives only conges to about half the cost of ditching with pick and shovel. The amount of explosive to be used per hole naturally depends upon the nature of the ground and the depth of the hole, and the amount of work each shot has to do, while the number of holes bepends upon the size of the stfamp, the depth of the impervious soil, and the amount of water to be lowered. A four-ounce cartridge of dynamite per 15 inches of depth is an approximate rule, which will be found to give good results.