ADVENTURE, Depth and Technology (ADT), a remote imaging and underwater survey company based in Santa Cruz, California, US, recently joined forces with Advance Diving Systems (ADS) from Mesquite, Nevada, US to investigate and document a 10,000 gallon per minute water leak from a high altitude reservoir in Utah. If not located and sealed, the leak would cause the shut down of a power plant, at an estimated cost of US$80M a month.

During the summer of 2002 divers were brought in to locate the source of the leak. With extremely poor visibility from algae growth and summer runoff, they were unable to do so. The power company, which services the greater Salt Lake City area, made a decision to wait until winter when the lake was frozen, knowing water clarity would be at its peak and the ice would provide a stable work platform. Their plan was to bring in an ROV, deploy it through the ice and do a complete underwater survey.

In February 2003 the ADT and ADS teams were contracted to perform the survey operation. ADT brought in their Fisher SeaLion ROV and Diver Mag 1 hand-held magnetometer. The remoteness of the site required all equipment be transported in by snowmobiles and sleds. An on-site dive station and electronics room was set up close to the suspected fault lines. Over nine days the crews worked at an altitude of 2590.8m in near zero temperatures with snow falling every day.

Capt. Wings Stocks, owner and president of ADT reports: ‘After cutting triangular access holes through 18 inches of ice, a survey grid was established and the SeaLion went to work. After many hours of running grid lines with the ROV the first fault was finally located. The operator brought the ROV up to the surface until it was resting under the ice. The Diver Mag 1 was used to pinpoint the exact location of the ROV and a GPS position was taken. Over the course of the week several more faults were located and tracked. Each one was videotaped and it’s position documented.’

‘The SeaLion worked flawlessly, 7 hours a day, for nine straight days,’ he adds. ‘The power company’s chief geologist repeatedly commented on the performance of the ROV – not only on it’s ability to fly and hover, but on it’s reliability despite the extreme weather.’

Equipment

The SeaLion ROV, available from JW Fishers, is a completely mobile underwater camera system capable of moving in any direction. Designed for pipeline work, river and ocean services and the inspection of hazardous sites, the SeaLion is a more powerful version of Fishers SeaOtter ROV.

The ROV has a sophisticated six motor propulsion system, says the company, four motors for forward and reverse, and two motors for vertical and lateral thrust. All motors are reversible and operate at variable speed. Meters on the control panel monitor thrust and direction of the motors.

The SeaLion sends its video picture to a topside 13inch high resolution colour monitor. A VCR can be connected to the monitor to make a permanent record. The colour camera has a 6mm wide angle lens. The camera’s 70° tilt allows a full 120° viewing angle. Illumination is provided by four 100W remotely controlled tungsten halogen lamps.

The Diver Mag 1 is a microprocessor driven marine magnetometer detection system with a one gamma sensitivity. The hand held mag, according to the company, is a super sensitive detector of ferrous metal, designed to locate pipelines, cables, cannons and dredge parts.

Operator selectable cycle times of two, five and 10 seconds allows for a strong return signal, and an adjustable sensitivity switch allows for pinpointing targets.