Tuesday, 27 January 2009

ODT 26th May 1908

The sewage of the city was discharged direct into the Pacific Ocean through the Lawyer's Head tunnels for the first time yesterday.

For some time past, pending the completion of the main tunnel and the branches leading there, the sewage from the Musselburgh pumping station has been discharged on to the beach in the vicinity of Lawyer's Head, making this favourite resort a less desirable locality to visit than it was formerly.

The sands of the beach, however, provided excellent filtration, and the pollution of the waters was not by any means so serious as might be supposed.

With the completion of the tunnelling beneath Lawyer's Head, however, the necessity for the undesirable practice of discharging sewage on to a public place of health resort has been entirely done away with, and the sewage is now discharged direct into the ocean at two points in the rocky facing of Lawyer's Head.

The main tunnel at Lawyer's Head is 860ft 6in in length, and terminates at an air shaft from which two bifurcating 4ft tunnels diverge to the right and left in south-east and south-west directions until the ocean is reached.

The amount of sewage to be discharged daily by means of four hours' pumping is 348,000 cubic feet, equal to 37,000 cubic feet per hours.

Undersea concrete pour achieved

By Allison Rudd on Sat, 18 Oct 2008
It sounds impossible: Take enough concrete to pour the bases of eight family homes, pump it 250m and fill a large hole 9m below the surface of the Pacific Ocean.

But contractors working on the Dunedin City Council Tahuna sewage outfall pipe did just that successfully yesterday.

Specialist staff from AAA Concrete Pumping were brought in from Marlborough and Queenstown to pump 190 cubic metres of concrete along the length of the construction pier and into an underwater steel structure.

The resulting concrete block will securely hold in place two outfall pipes - an underground pipe laid from the Tahuna sewage treatment works and a 1km long marine pipe - to enable a short joiner pipe to be placed between them.

It was important to "hold things together", council project manager Brian Turner said yesterday.

"The pipes will join approximately 9m below the surface and 5m below the seabed, so this is the most critical area to get right."

Pumping began at 7am and was finished by 2pm.

The job was the most challenging AAA Concrete Pumping had attempted, administration manager Paula O'Donnell said yesterday.

"The distance was the farthest we have ever done . . . What the guys did takes a lot of skill, but it all went very smoothly."

The $37 million pipe project has been delayed by rough weather, but Mr Turner said pressure testing was expected to take place next month, with the pipe expected to be commissioned in December.



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