Opotiki Harbour dredging trial explained

The equipment at the river channel. Supplied photos.

The contractor behind the build of the new Opotiki Harbour entrance is reaching out to the public to explain what they are doing.

HEB Construction recently trialled equipment for use in dredging the river channel for the new harbour.

The equipment is a low-cost option for cutter-suction dredging, where the material in the river is loosened and then pumped along discharge pipes to be deposited on land or onto a barge for transport.

HEB’s senior project manager David Wyeth explains the process.

“The equipment uses a cutter-suction head attached to a regular excavator. So at the head, you have a propeller which loosens the sand and the sand and water is pumped up and moves along a discharge pipe to final deposit area."

“In this trial we just moved the sand and water slurry about 120m to an excavated sump deposit site on land, where it quickly settled and dewatered. The pump is self-contained and is driven from the hydraulics of the excavator.

“While the cutter-suction dredge process isn’t new, the trial was a good opportunity to test the process on site and in our own particular conditions.”

Consent conditions have requirements on the use of dredging materials from the river channel and from outside the walls to be used for river closure or deposited on land.

The trial was also an opportunity to check the suitability of equipment for ongoing harbour maintenance dredging requirements at the same time.

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