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The equipment is part of Port Otago's ''next generation'' project to deepen and widen the 13km of channel from Port Chalmers to Taiaroa Head, and the port company has just begun to seek expressions of interest for the job from international contractors. On Wednesday, two piles were driven off the Otakou wharf to install the submerged turbidity meters, which will measure and provide a base-line during the next year on particles in the water and water clarity.
Port Otago general manager of infrastructure Lincoln Coe said six more piles would be driven in around the harbour soon, with those in navigable areas to carry lights. Meters and lights would be solar-powered.
There would be one pile at Pulling Point, others near Harwood, lower Portobello Bay, on Quarantine Island's shoreline, at the northern tip of Pudding Is near Portobello and near Roseneath.
Mr Coe said while the meters would not offer the public live web-cam images, which could be of interest to fishers, they would be able see a graphed interpretation from streamed data on Port Otago's website indicating clarity levels.
Port Otago has 25-year resource consents in place to undertake a wide range of dredging options.
Port Otago could dredge from the existing 13m depth to 14m and remove 2 million cu m of spoil for $10 million, and at the furthest extent dredge to 15m deep, at a cost of $35 million, to accommodate larger container vessels.
Mr Coe said no decision had yet been made, other than the dredging depth would probably be within a range of 13.5m-14m.
A decision was ''quite some time away'' on whether Port Otago or an international contractor would undertake the work.
Some environmentalists and coastal user groups have expressed anger over the plan to dump spoil about 6km out at sea.