WIDENING THE DOOR

Hokitika Guardian, 27 January 1931, Page 2

WIDENING THE DOOR

WORK IN OTAGO HARBOUR.

SUBMARINE BLASTING

DUNEDIN, January 21

Sternly progress is being made with the work of unloving the toe of rock which jots into the Victoria Channel Irom Quarantine island on the Dunedin side. i ids obstruction inis been a cause of aux.ety to the Otago Harbour Board for some time and its removal will prove a source of .satisfaction both to captains of vessels and members or the hoard. .Mr F. Goodman, of Gisborne, is the contractor.

On the Dunedin side of Quarantine Island facing the channel there is a rocky formation showing above sea lev il and a toe c? rock then juts into the channel below the water. As vessels come through this channel or cut between Quarantine and Goat Islands on their way to Dunedin they have to he swung a bit. to starboard to come in between the beacons of the upper chan nel. With a strong north-east wind a vessel so swinging has a pressure oh its counter, causing the stem to eoiiie across to Quarantine Island its idie how is turned into the upper clialinel. It is in these circumstances that the obstruction Ims proved a menace.

INCIIEASE IN DEPTH. The rock formation runs more or less parallel with Quarantine Island for a distance of 150 feet. The depth of water, over the. toe at low water varies from 1.(5 feet t.o DO feet, and the contractor has to remove the rock as as to obtain a uniform depth at iow water of DO cot Whim this has been done the width of sale navigable water from Quarantine Island to Goat Island will be approximalelv 020 feet. It is about 200 loot

at present. It is estimated that there are 1500 cubic yards of rock to be removed. The rock is of a very hard nature. The rotary drill used is operated, from a mow. It is of the type used in drilling for oil in America, and it is a very •effective tool. It is driven by a 7 horse-power oi.l engine, and it, can drill to Draeticafly any, depth. An air compressor with a 601 b pressure is worked in conjunction with the drill for Uie purpose of keeping the hit of the drill clear; of broken rock. A number of dudes have already been, driven ; into the rocks. These are marked, by iron ■rods which stand above water level., .

BLASTING TO FOLLOW. When the work of bbriiig is completed u diver will go down and fiil Uie holes with gelignite which will be exploded by electricity, Ali.v )oo»o rock then left lying above a 80ft, low waver level will have to be removed by' the contractor. The best performance, jn drilling so far has been 4ft 6in. an hour. The drill bores a four-inch hole to a depth of several feet. Tlie current is very strong in the gut and more than once when a heavy wind lias been blowing work lias had to be suspended. From the top of tire drill to the bit there is a distance of about 60 feet, but tlie length of driil could lie added to very considerably if there were need. Tt will be some months before the work, which was commenced in Uie middle of December, will be completed. The depth of water in the gut between the two islands and in tlie immediately vicinity is from 70 feet to over 100 feet. Mr Goodman lias carried out a great deal Of work both on the land and sea in the Dominion. He had tlie contract for building a jetty and wharf at Toiaga Bay, the work taking four years and a half, and costing £72,000.