CONCRETE HARBOR WORKS.

Grey River Argus, Volume XIII, Issue 1537, 8 July 1873, Page 4

CONCRETE HARBOR WORKS.

The following letter by Mr M'Gregor, C.E., to a gentleman in Napier, appears in a local paper :— "The Hon. Mathew Holmes has requested, me to.send you a few particulars regarding the breakwater now under construction at the port of Oamarn, and in compliance .with his wishes, 1 beg to inform you that the breakwater, as I have designed it, and now being carried out successfully so far, is intended to inclose 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 ft 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 ace moulded on a piece of reclaimed ground, and ; are allowed to stand for tyro or three months before removing; these weigh from twenty.five to thirty tons, and when they are hardened, are lifted by a forty- ton steam travelling crane, and deposited in their places in the wall. The concrete blocks over the top of the rubble pockets, in the centre of the wall,' are built in sifoc, and weigh 110 tons. At present the wall only stands three feet above high water line, but when it is run of its full length, I intend to build a concrete capping in caissons six or seven feet higher, the fall width and whole length of the breakwater, in one solid monolithic mass. The work is now advanced seaward about 150 ft, and. appears to stand the force of the waves without showing the slightest signs of damage, and my confidence in the stability and success of the work is increasing as the work progresses. The cost of the work (including the cement, which "is imported and specially manufactured to the order of the Harbor Trust) is about L6O 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 LI6OO, because all the patterns had to be got up for this unusual class of machinery. With regard to concrete breakwaters generally, I am of opinion that they can be built anyr where where shingles and sand can be procured readily, and can be made strong enough to defy any sea."