Rosedale Outfall

Client: McConnell Dowell

Location: New Zealand

LDD reacted quickly to client requests; successfully deploying a full RCD drilling spread at short notice to install a 17m shaft in New Zealand. LDD Engineering reconfigured standard drilling equipment to save cost, reduce shipping space and enable rapid mobilisation.

LDD were contacted by McConnell Dowell, the main contractor for North Shore District Council on the new Rosedale Waste Water Treatment works in Auckland, New Zealand. The initial contact was made mid-August, and after rapid negotiations, a Letter of Intent was presented to LDD in early September. The majority of the equipment was prepared at LDD HQ in Cornwall and was presented for shipping in early October; not only demonstrating LDD’s ability to react quickly to our client’s demands, but do so in an effective and pro-active manner to meet our client’s critical schedule.

Our LDD engineering and project teams closely managed the bespoke fabrication ops in New Zealand and China, ensuring all equipment arrived in a timely fashion, quayside in New Zealand, to suit the Client’s concise programme.

Client quotation

“We cannot fault LDD on their performance on the Rosedale Outfall Riser Shaft drilling works. The planning and execution of their works was exemplary and produced an excellent result”. Statement from Roger McRae, General Manager, McConnell Dowell Constructors Ltd, regarding LDD’s performance at Rosedale.

Project statistics

  • No of shafts: 1
  • Pile diameter: 1950mm
  • Average length: 17m
  • Geology: 10 – 12 MPa
  • Duration of Drilling Works: 18 Hours

Equipment

  • LD408 Drilling rig
  • Drill bit 1950mm Mill tooth
  • Specialist grouting equipment

Challenges

Drilling tolerance was very tight between the GRP liner and socket edge, therefore careful precision drilling was essential.

LDD employed our LD408 pile top drill rig, which typically would only be used for sockets up to 1300mm diameter, however in this case it proved to be more than capable with dealing with the larger diameter of 1950mm. The in-house design team developed a novel solution which incorporated a false deck (cellar deck), flange bolted between the drilling conductor and drill rig. The large diameter items including the drill bit and bottom hole stabilisers, were run inside the conductor and suspended from the false deck, before the drill rig was connected and the drill string run in conventional fashion.

The main advantage for using the LD408 unit was the combination of a reduced day rate and shipping space, fast mobilisation/demobilisation times and a reduced handling weight particularly above the shaft centre.

Upon equipment arrival, the LD408 and down-hole equipment were loaded onto MacDow’s floating installation vessel SEATOW – 80. This was then towed to site and held onto position using a 4 point anchor spread. The LDD team assisted MacDow in the installation of the sub-sea frame, placement of concrete and the installation of the drilling conductor casing. During this phase, the LDD crew took this opportunity to attain real-time information regarding vessel movements and onsite weather conditions to ensure the safe and smooth installation of the drilling equipment.

The 1950mm drill-bit proved itself in the hard-rock conditions encountered throughout the drilled shaft and out-performed the client’s expectations by completing the shaft 1.5 days ahead of the project programme.

The environmentally sensitive surrounding area and close proximity to residential buildings caused concern both for our Client and local Council. LDD were proactive in dealing with all environmental assessments and working methods were modified to suit the impact of noise and light. The LD408 rig also demonstrated another of its on-site advantages; its minimal noise impact. When an on-site noise impact assessment was conducted, the rig achieved levels well within the pre-specified limits; causing no environmental concern.