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Date: 13 May 1996
Author: Mr. Warren Fisher, Ancor-Loc New Zealand Ltd.
Subject: Sewer Pipe Outfall
Project Site: Orewa Beach, New Zealand
Description of Problem: The Red Beach polyethylene sewer outfall
pipe was beginning to fail at the stainless steel joiner junction because of surf and tide action. With the onset
of inclement winter weather, gales, etc., there was no time to secure the pipeline using the older method of burying
200-liter drums of concrete (requiring barge, crane, boat and digger, etc.).
Site / Design Conditions: Depth of water at low tide approximately
1.5m, visibility 1m, silty sand and shell conditions. Works civil engineers required urgent securing of the pipeline
because the pipe was bouncing during the low tide surf and was in danger of breaking apart.
Proposed Solution / Selected Solution: 3 sets of 3 each 88-DB1 anchors
were driven into the seabed to approximate depth of 1.2m then shackled to an 8mm galvanized chain and locked. Although
the pipeline is to be re-routed to another area within 2 to 3 years, the securing operation needed to be semi-permanent
because of the high environmental risk if the pipeline was to separate.
Anchors: 9 x 88-DB1, 10m x 8mm Hot Dipped Galvanized Chain
Installation Equipment: 12 lb. sledgehammer, DS-88 Drive Steel, 2 men with wet suits and snorkels only.
Installation Notes: DUCKBILL® anchors have proved so successful,
the council engineers are now considering the installation of further anchors to pin a concrete sea wall beside
the pipeline. This would reduce the sand movement and scouring action underneath the pipe.
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