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Divers attach giant metal rulers to Lower Huia and Upper Mangatawhiri

Installing giant 30-metre custom-made iron rulers underwater is anything but routine – even before the days of electronic equipment – but that is exactly the project ENVCO Global is on the verge of completing in the Lower Huia Dam (Waitakere Ranges) and The Upper Mangatawhiri Dam (Hunua Ranges).

Technical Specialist for ENVCO Environmental Equipment Suppliers, Graham Andrew, says the giant 30 metre staff gauges – commissioned by Watercare Services Limited – were installed at both dams because it is important to keep a manual check on electronic readings when it comes to dam levels.

“Watercare does have electronic equipment to measure water levels, but you need a way to keep the electronics honest, so to speak. The other reason it is being done is because the original gauges at these sites are imperial measurement – they have been there since the dams were built, well over 50 years ago.

“Each of the gauges was custom made and installed by scuba divers, so they had to be designed to interlock with ease underwatero within three millimetres – no easy feat when we’re talking the physics of manoeuvring and drilling the lengths to old, hard concrete and much of it beneath the surface.

“This required that we custom design each component. Our third project, also in the Hunua Ranges, will be even more challenging because we have negotiate over a step in the dam wall,” he said.

Installing staff gauges isn’t normally as challenging because most of the work is done in ponds or rivers where all that’s required is two or three metre rulers attached to a pipe on the bank.