The $50 million capital dredging programme set to begin deepening the Port of Tauranga Harbour channels in October is also going to replenish the sand at local beaches, says Port of Tauranga chief executive Mark Cairns.
The Pilot Bay beach which is regularly replenished by the port's maintenance dredging will also benefit from the capital dredging, as will the ocean beaches.
The dredged sand will be dropped where it will wash back onto the beaches. Photo: Supplied.
'There are two dump sites of clean sand at the Mount and further along towards Omanu,” says Mark. 'That's been proven scientifically to have a replenishing effect on the beaches.”
One dump site is between Moturiki and the Mount Main Beach, which is a near shore replenishment site, and there are two sites further along Marine Parade.
The original Port of Tauranga dredging consents were based upon ground breaking sediment transport studies work by among others, the late Professor Terry Healy, Willem de Lange, and team from the University of Waikato.
'Go back and look at the old photos of the Mount. Pre-dredging the Mount Main Beach was a very rocky beach. It's actually improved since the dredging there's been sand accretion,” says Mark.
'The beaches have actually improved. There's some science behind this consent we have got.”
As well as consent conditions requiring the sand to be used for replenishment as directed by the Bay of Plenty Regional Council, the consent conditions also require ongoing monitoring.
Bathymetric surveys are to be carried out at all dredge sites immediately before and after dredging.
The depth sounding survey has to be accurate enough to enable an accurate calculation of the volume of sand removed during each operation.
They also have to keep an eye on water quality. Water samples have to be taken upstream of the dredging to determine natural background turbidity values, and to determine the clouding in the water column during dredging. The water samples have to be taken every second day.
Danish dredging company Rohde Nielsen will be deepening port channels from 12.9 metres to 14.5 metres depth inside the harbour and 15.8 metres outside the harbour – using a combination of trailer hopper suction dredge and a large backhoe.
'The dredging is the final building block in a $350 million capital expenditure programme over the last five years to facilitate New Zealand's exporters and importers being able to access the blue water savings of larger ships,” says Mark.
The port company is expecting to have the dredging completed by the third quarter of 2016.
3 comments
Goodbye Surfing
Posted on 09-07-2015 09:13 | By Dave Manville
It doesn't take an avid surfer to realise just how much of an effect this dredging has had on the behaviour of waves over the past 6 months or so. The sand dumped within a 1km range of the shore along the coast over the past few months has created banks and troughs in the sea bed close to shore and this has resulted in nearly all waves uncharacteristically either dumping on the banks or lulling out. This occurs even on days when tide times and general conditions would normally present beautiful waves that one can ride all the way into shore. If you don't think this dredging has effected the quality of waves then you're head is in the sand. With the planned dredging ahead in 2015, things will only get worse. The tourist drawcard that is Mount surf is quickly becoming a thing of the past.
Surf Action is Concerning
Posted on 09-07-2015 11:43 | By Bill Gibson-Patmore
Dave Manville has presented a very good explanation. I am most definitely in favour of scientific proving of theories. However, please let's not over look these basic facts: "Science will prove something, but if the science is directed to one area, there may be other areas or objectives which are overlooked." If the science is constantly attempting to prove the same thing, there must by invitation for more parameters to be introduced, as need arise or change." "It seems fairly clear that the criteria of the consent is to 'Return Sand to The Beaches and Replenish.' Dave's point about the quality of the sea bed.... prior to the beach... is extremely valid, and I've not seen any part of the consent process which charged a responsibility for attention to that facet." We all know that putting a one+? metre wall in the ocean near Tay Street was scientific? Bill
NO
Posted on 09-07-2015 20:23 | By Capt_Kaveman
NO NO NO what a bunch of idiots, all the sand should be left inside the harbour
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