Background

Bespoke Underwater Engineering: Western Australia

Background

This scope was part of a refurbishment and upgrade campaign on the water supply infrastructure for a large regional metropolis 600km from Perth, Western Australia. The water catchment is achieved via the 120 year old Mundaring Weir located in the hills of Perth. Part of the upgrade to the iconic structure was the removal of the original water intakes and replacing them with a larger, more efficient design. The water intakes are located in a well beneath a heritage-listed structure on top of the weir.

The requirement was to drill a one meter diameter hole through 1.9 meters of old concrete reinforced with granite boulders while underwater. The positional accuracy required was only +/-10mm, with similarly tight tolerances on the diameter and heading of the hole through the wall.

Background

Solution

Following an exhaustive failure mode, effects and criticality analysis (FMECA), the decision was made to deploy the tool down the well and drill outwards, rather than start outside and drill inwards. The analysis also identified the most appropriate cutting methodology and contingency requirements in the event of a failure. The tool had to be compact to not only fit down the well, but also through the door of the heritage-listed structure on the top of the wall. The width of the door was only slightly larger than the diameter of the hole to be drilled, resulting in the need for a clever and compact design. The careful selection of cutting methodology and the detailed consideration of contingencies was essential in the prevention of possible contamination and disruption to the supply of drinking water to a large metropolis.

The first step was the installation of a landing porch down the well to accurately establish the correct cut location and ensure the high tolerances were achieved. The porch served to receive the cutting tool and also provided rope technicians with a stable working platform within the well. The cutting tool was lowered down the well and sat on top of the porch, after which the well was flooded to match the water level of the reservoir. All equipment was controlled by a technician on top of the wall.

Conclusion

The hole was successfully completed within 8 hours and surpassed all targets in terms of speed and accuracy. The resulting coupon of concrete weighed nearly 3 tonnes. Although the scope differed in terms of location and client, it still comprised bespoke underwater engineering and shared a great number of the traditional challenges often encountered in our more routine scopes: confined spaces, poor visibility, limited intervention, high accuracy and novel technology.

Background

Benefits

  • The Diamond Drill Drum was the first and largest of its kind to ever be designed, built and applied underwater
  • Successful first scope with a new client in a new sector
  • Excluded competitor with existing track record
  • Successfully extended existing technology into new applications and new magnitudes

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