Light at the end of the tunnel as two ends meet in middle

JOHN BISSET/Timaru Herald

MEETING POINT: The first of Timaru's three multi-million-dollar sewer tunnels has met in the middle. The council contractors Harker Underground Construction, working on the sewer main renewal between Washdyke Lagoon and Smithfield, broke through from each end of the tunnel on Friday morning. Pictured ripping up the tracks used by the tunnel boring machine are, from left, Jason Turner and Rodger Meaclean, and at rear, from left, Leonard Morgan and Tim Clemens.

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COUNCIL contractors Harker Underground Construction, working on the sewer main renewal between Washdyke Lagoon and Smithfield, broke through from each end of the tunnel on Friday morning.

One crew was digging from the southern end with a tunnel boring machine, while the second crew was using traditional manual labour with explosives to break down the rock face from the northern end.

The two tunnel halves were well-aligned when they met, enabling the tunnel boring machine to be propelled forward to the end of the northern shaft, dismantled and removed.

The boring machine works like a small excavator in a horizontal can which is propelled through the ground with hydraulic rams, while a mechanical arm scoops soil on to a conveyor belt which runs back to the entrance shaft.

Timaru District Council district services manager Ashley Harper said good progress had been achieved.

"Due to the mix of basalt, clay and rock, it has been slow work at times when the contractor hits a particularly hard section, but the crews have been working 24 hours a day to keep to schedule. We're stoked."

Two new sewer main pipes will be run through the tunnel.

Contractors are already working on the second tunnel, directly under Westcott and Richmond streets, and the tunnel boring machine will be used again on the third tunnel, from Ashbury Park through to Virtue Avenue.

The three tunnels are two metres in diameter, bored at depths of between four metres and 19 metres and are each about 400 metres long.

The pipe-linking contract, held by Works Infrastructure Ltd, sees pipes run through the tunnels, linked and joined to pipes already installed across Caroline Bay.

- © Fairfax NZ News