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Art. LIII. — On the Drainage Works at Remuera SwamjJ. By J. Baber, C.E. 



(With Illustrations.) 



[Read before the Auckland Institute, November 15, 1869.] 



The means for draining the swamp near the Remuera sale-yards, known as 

 Mr. Farmer's swamp, have been pi-ovided by laying earthen pipes in a tunnel 

 in a different manner from the ordinary mode. The area of the swamp is 

 twenty acres, in winter it had about three feet of water in the lowest parts. 

 The greatest depth of the drain now laid is twenty-eight feet below the surface 

 of the ridge. The diameter of the pipes used is thirteen inches. 



Iu designing the work, care had to be taken, that the pi]3es, after they 

 were laid, should be secure from accident or displacement, from any slipping of 

 the feet of the upright timbers, and that sufficient room should be left for 

 working, without taking out more earth than was necessary. The striata 

 through which the drive was cut consisted of a red volcanic soil, varying from 

 eight to ten feet in thickness, overlying a bed of white silica and alumina almost 

 destitute of cohesion, falling in from behind the timbers in thick flakes, without 

 warning. The transverse Section 1 (See Plate 1 3) shows the working : the 

 tunnel being first driven and timbered to a convenient length, a trench two 

 feet wide, and four feet deep, was sunk in the floor of the drive, in this the 

 pipes were laid, and the earth thrown on them as the trench was dug. The 

 floor of the drive was thus raised about nine inches, and the feet of the 

 uprights secured from slipping, while sufficient headway was left above, both 

 for levelling and trucking out the earth from the drive. This plan was 

 continued for about 220 feet, when the white sandy bed became so treacherous, 

 that it was no longer safe to trust to the footing of the uprights, which slipped 

 inwards as soon as the strainers were moved, and the digging the trench 

 commenced. For a short distance Section 2 was used ; it was safer, but did not 

 afford the same facilities for keeping the correct gradient, nor for removing 

 the earth. 



The longitudinal section shows the tunnel from A to B, driven according 

 to Section 1, and its continuance from B to C, according to Section 2, the 

 remainder was laid in an open cutting. The shaft D is permanent, in order to 

 inspect the work at any time without much cost, that at E is a working shaft, 

 filled in at completion. The timber uprights and headers are left in the diive, 

 allowing the earth to fall gradually in upon the earthen pipes. The work was 

 executed in a bad season of the year, in the months of May, June, and July. 

 It cost £222 lis. 6d., or rather more than £1 14s. a yard. The pipes were 

 socket pipes, glazed inside and out, manufactured by Carder, of Henderson's 

 Creek. 



Like other swamps in the volcanic parts of this district, this one had its 

 summer outlet through the lava, on the south-west side, which dried the swamp 

 in summer, but in winter was insufficient to carry off the water that came 

 from the surrounding land. In the summer of 1868-1869, this outlet was 

 enlarged, in the expectation that it might be rendered more effectual, this, 

 however, did not prove to be the case. The water is now carried under a 

 ridge, and thence to a volcanic cave, where it instantly disappears. 



