OAMARU HARBOR WORKS.

New Zealand Mail, Issue 116, 5 July 1873, Page 17

OAMARU HARBOR WORKS.

The following letter by Mr M'Gregor, C.E., to a gentlemau in Napier, appears in a local paper :

“The Hon. Matthew Holmes has requested me to send you a few particulars regarding the breakwater now under construction at the port of Oamaru, and in compliance with his wishes, I beg to inform you that the breakwater, as I have designed it, and now being carried out successfully so far, is intended to enclose a space of about seventy acres, and form a commercial harbor sufficiently large to accommodate vessels at low tide drawing not more than sixteen to eighteen feet of water. The wall is to be 1200 feet long, and is constructed of Portland cement, concrete blocks, with rubble pockets (at intervals) under low water line. The blocks that form the outer casing are moulded on a piece of reclaimed ground, and are allowed to stand for two or three months before removing; these weigh from twenty-five to thirty tons, and when they are hardened are lifted by a fortyton steam travelling crane, and deposited in their places in the wall. The concrete blocks over the top of the mbble pockets, in the centre of the wall, are built in situ, and weigh 110 tons. At present the wall only stands three feet above high water line, hut when it is run out its full length I intend to build a concrete capping in caissons six or seven feet higher, the full width and whole length of the breakwater, in one solid monolithic mass. The work is now advanced seaward about 150 feet, and appears to stand the force of the waves without showing the slightest sign of damage, and my confidence in the stability and permanent success of the work is increasing as the work pro gresses. The cost of the work, including the cement, which is imported and specially manufactured to the order of the Harbor Trust, is about £6O per lineal foot forward, but any similar work undertaken in the colony could be executed for less than this amount. We have had to expend large sums in plant and machinery—the steam crane alone costing <£l6oo, because all the patterns had to be got up for this unusual class of machinery. With regard to concrete breakwaters generally for the improvement of New Zealand ports, I am of opinion that they can be built anywhere where shingle can be procured readily, and can be made strong enough to defy any sea.