COLLAPSE OF A WHARF.

New Zealand Herald, Volume LXI, Issue 18852, 29 October 1924, Page 8

COLLAPSE OF A WHARF.

PILES GIVE WAY. WESTERN WHARF SUBSIDES A LARGE AREA DAMAGED. SECTION 160 FEET LONG. REPAIRS MAY COST £20,000. Damage to the extent of many thousands of pounds was caused to the Western Wharf wh«in some of the concrete piles collapsed about 3 p.m. yesterday. Though there were a number of waterside workers and others on the wharf no one was on the part affected and there were no casualties. The first indication to those on the wharf that something was amiss was the loud cracking of concrete. They were amazed to see a large area_ of the surface of the wharf near the sea end gradually subside till a portion on the western side was almost at water level. Large fissures appeared on the surface, revealing the steel reinforcing girders. On the eastern side stout wooden fenders splinted and then snapped in two. Lorry Driver's Experience. At the time the driver of a motor-lorry was about to tip a load of soil over the side of the wharf. tChere was a sudden tremor beneath him and although be did not realise the situation immediately, be had a foreboding of danger. Without delay he tipped the soil on the wharf, cranked the lorry, and sped away to safer ground, being greeted with an outburst of cheers from waterside workers, who realised his peril. At the point where the wharf sagged most the concrete piles broke off almost in the oozing mud and the side wall of large boulders, cemented together, crumpled and fell to pieces. Several piles on the other side snapped as if made of chalk. On this, the eastern side, the steamer Trelissick was berthed, but she was not affected. An electrio crane was unloading cargo from a forward hold but fortunately it was some distance from the danger zone. A large wooden shed occupied a. corner of the sunken surface, and in it were stored some 60 coils of wire. These slid into the mud, but as. the tide was out, they were easily retrieved. Drop l"rom live to Twenty-fiva Feet. The depth of the drop at the corner of the shed was sft. and the greatest point was from 20ft. to 25ft. A gang of workmen was soon on the spot cutting through the concrete surface, about 9in. in thickness, and the steel reinforcing, so that the depressed part could be dropped, thus relieving the strain on the rest. The surface has been thrown out of alignment for about 160 ft., but quite 300 ft. will require rebuilding as, for some distance on both sides of the subsided portion, cracks on^ the pavement show evidence of the strain to which it was subjected. The Western Wharf is 1000 ft. long, and is one of the latest additions to the port facilities. Construction was begun abont 1918, and it vtfas completed in 1921, having cost about £85,000. The western tide deflector runs into the sea alongside it, and between the deflector and the western side of the wharf is a gap in course of reclamation. It was toward this gap that the wharf leaned. Theories as to the Cause. Mr. W. H. Hamer, engineer to the Auckland Harbour Board, attributed the mishap to the collap&e of a stone wall built along the western edge of the wharf to support it. This, he considered, had thrown extra weight on the piles, causing them to list and finally give way. Another theory was that- the sea bottom at this point was of papa, rock and that the piles had slipped. The damage has been estimated at from £10,000 to £20,000. Collapse of North Wall Becalled. A somewhat similar occurrence happened in the vicinity of the Western Wharf on February 10, 1910, when some 437 ft. of the north wall of the Freeman's Bay reclamation works gave way and toppled into .the water. The eastern wall, of solid concrete, ran out for a. distance of some 1400 ft., and the north wall had an approximate length of 1700 ft., with a wharf of cresceat-shaped concrete slabs on the outside. The work of pumping silt into the area to be reclaimed was proceeding, all going well until February 3, when it was noticed that the silt was banking up against part of the eastern wall. There was some delay before the pipes from the suction dredges were moved away from the danger spot, and when this was effected it proved to be too late, for with an ebb tide, the pressure became too great, with the result that the wall fell over into the water, not a single pile or slab being left standing in the whole distance of 437 ft. The replacement of the wall did not prove so difficult as the clearing awav of the debris from the foundations. The estimated cost of the damage at the time was £4300.