Assessment of drinking water reservoirs boosted by underwater ROV

Published 05/10/2020

Underwater remotely operated vehicle, Deep Trekker is assisting the ongoing inspection programme of 150 drinking water reservoirs around the region.

By Jim McNaughton

 

Wellington Water has purchased a Deep Trekker underwater remotely operated vehicle (ROV) for the ongoing inspection programme of its 150 drinking water reservoirs located in Lower Hutt, Porirua, Upper Hutt, South Wairarapa and Wellington. Weighing only 8kgs and operating for up to 8 hours on its battery, the ROV shoots high-res video and can operate to a maximum depth of 200m.  Hamish Black, advisor, smart services, for Wellington Water, said the ROV was easy to operate and provides great low light images for inspections.

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The underwater ROV about to dive on a reservoir inspection. A 100m signal cable is needed for the largest tank reservoirs.

 

Previously, the internal condition of a reservoir was often largely unknown prior to draining it for inspection, cleaning and maintenance. Hamish said that meant the costs and time needed to get the reservoir back in service were also largely unknown. “Not only does the ROV lessen the amount of time a reservoir is out of service for maintenance, it helps a lot with prioritising work and budgeting.”

Drinking-water reservoirs are currently on a 20-year maintenance programme. “The problem is that you don’t know what you’ll find,” Hamish said. “The ROV means we’re not going in blind when we let a reservoir drain down for maintenance. We know the size of the job beforehand and can prepare for it.” 

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Utilities Service Person, Scott Woodhouse and Field Service Person, Alistair McEwan using the ROV’s video camera to inspect the reservoir at Wright’s Hill, Karori.

 

Underwater ROV inspections have been completed by contractors in the past but the high cost has meant they were mainly used to diagnose a known issue. “Now, with the ever-decreasing cost of technology, the ROV has become cost-effective, and we can run a full programme of inspection in-house.” 

Divers have also been used for assessments in the past. “Diving in a reservoir tank is a risky activity and the logistics are complicated. ROVs are much safer and easier to manage.” 

Hamish said the ROV’s efficiency means Wellington Water will be able step up the reservoir assessment and maintenance programme. “The ROV reduces the amount of time reservoirs are out of service because it allows us to prepare in advance, helps us prioritise work, budget accurately, and keep people safe for assessments—and save money. It’s an awesome tool to have.”

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Screen shot: The Deep Trekker looks up to the reservoir’s entry hatch.