"However, these last few metres will be the most challenging part because we need to line up the pipe with the very middle of the steel sleeve on the Matapihi side."
Contractors Brian Perry Civil have been working continuously since Friday to install the steel pipe under the harbour.
"They've had to work 24/7 to ensure the pipe didn't get stuck," Severinsen said.
"This is a very dynamic part of the project with lots of moving parts. We've had six cranes and 14 diggers on site."
It's hoped the outer pipe would emerge at Matapihi tomorrow.
From there, work will begin to winch the plastic pipe that will eventually hold the wastewater through the steel pipe, before the pipe is connected at both ends to the rest of the Southern Pipeline wastewater trunk main.
As of yesterday contractors returned to a single daily 12-hour shift.
It will take another three to four months to complete the Southern Pipeline project and reinstate construction sites to their original states.
The $99 million Southern Pipeline project has been beset by delays and problems since construction started in Greerton in 2010.
The outer pipe was the riskiest part of the $21m harbour crossing.
Project manager Chris Thomas said on Tuesday there was "an air of excitement" at the site and there would be a celebration when the steel pipe was finally through.
It's a huge milestone for the contractors involved.
"There is an Australian drill which has an Australian team of people, and a local team as well. They have done an amazing job. It's been a surreal weekend."
Thomas said he had never seen so many people working so efficiently together on a project with so many parts to it.
Completion of the pipeline will mark the end of waste bubbling out of manholes at the lowest point of central Tauranga's sewerage system when the Chapel St treatment works were unable to handle huge volumes of stormwater-swollen sewage.
Harbour crossing: how it happened
• 1500 tonne outer steel pipes welded together at Memorial Park • Welded into five strings of pipes between 156m and 468m • Pipe string hoisted in the air by cranes and threaded into end of drill hole • Strings thrust one after another through the hole from Memorial Park, pulled from Matapihi • Five hours welding between each pipe string • Drilled hole full of bentonite mud to keep it open • Pipe filled with water as it passed through the mud to reduce buoyancy
