Construction of the abutments for the 150 metre Kaituna River Bridge is underway as Tauranga’s biggest roading project continues – the Tauranga Eastern Link.
The bridge abutments are being constructed using mechanically stabilised earth walls; basically huge layer sandwiches of sands and geo grid mesh and fabric.
Works on the Kaituna River Bridge abutments.
Concrete slabs will be used to create the abutment facings.
The river front is protected by sheet piling, which will protect the river bank when the 55m bridge piles are driven for the bridge piers.
The work above ground comes after months of subsurface preparation work necessitated by the fact the highway and the bridge are being built across centuries of bog and swamp.
The peat has dictated the methods of construction and the materials which are largely sand and pumice sourced from Paengaroa and Tauriko.
Rock is available from the quarry on Poplar Lane, but it would create an impermeable mass, say senior project manager Wayne Troughton. Sand and pumice is permeable.
“Part of the resource consent conditions are that it needs to allow water to flow through it,” says Wayne.
“If you put an impermeable layer there you are effectively making a dam, and that would be bad.”
The highway is being built west of the Kaituna, through the scientific process of piling up the sand and pumice and leaving it for a while to settle.
Wick drains are emplaced under the alignment.
Wick drains are vertical drains that allow sub surface water to escape when it is squeezed by the weight of the preload material.
They were installed 20-30 metres into the ground before the pre-load material was placed. There’s about 920km of wick drains installed.
Another threat to highways built on swamp is liquefaction during earthquakes.
At the Kaituna Bridge, abutments in-ground rock columns have been placed under the abutments.
Holes were drilled 15-20m into the ground and gravel dropped in as the drill shafts were withdrawn. The result is an invisible network of underground gravel columns.
“The sheet piling is temporary, all that sheet piling and the sand that’s behind it will be removed and it will be restored to a grassy river bank,” says Wayne.
The temporary platforms are from where the bridge piles will be driven at the river’s edge.
The TEL site will be holding its first public open day on Sunday, March 25 from 10am till 2pm.
It is largely based at the visitor information centre in Tara Road, Papamoa.
From the information centre the public will be able to walk out to the construction site behind the centre.
Apart from on State Highway 2 from Te Maunga to Domain Road, parts of the TEL site can also be seen Parton and Bell Roads.
The Bell Road boat ramp and car park is a 100 metres or so downstream from the bridge site.
On the eastern side of the river, parts of the site can be seen from Pah Road which crosses over the $380 million future highway alignment.
The new section of Kaituna Road is completed giving access to Te Tumu Road which crosses the alignment near Young Road.
Te Pumu Road is to be realigned and a bridge built to lift the new highway over Maketu Road.