The project called for a new power supply to run to the airport from a substation on Abernathy Road and required four holes to be bored under a 20 m wide main drain near the substation, and nine holes bored one metre apart under Horrie Miller Drive, which is the main public road in and out of the airport.
Fortunately, N.K. Contractors chose an experienced directional drilling contractor, Lateral Drilling, to safely achieve the clearances necessary for a main drain crossing and bores under Horrie Miller Drive.
Difficult environment
The four 45 m long bores near the substation main drain along Abernathy Road ranged from 110 mm to 150 mm in diameter. The bore was also required to dip steeply to pass under a five metre deep sewer main running past the substation into the neighbouring treatment plant, then level out to pass at least two metres below the bottom of the main drain to a maximum depth of around six metres before rising steeply to pass above the
600 mm diameter high-pressure steel natural gas pipeline operated by Alinta.
The gas main was 1,600 mm below the surface on the opposite side of the main drain to the substation and the hole for the power conduit could not be within a metre of the gas main. An Alinta representative was on site for the duration of this bore to monitor the proximity conditions.
This bore was further complicated by the presence of a high-voltage power cable and three fibre optic lines running close to the bore area and these lines had to be located before the boring could start.
The right tools
While the city of Perth is located predominantly on sand, the area of the bore contained interspersed layers of white beach sand and very sticky clay. Choosing the correct tools and drilling fluids called on the experience of the drilling contractors.
Lateral Drilling, owned by Wayne and Chris Martins, is in its 13th year of operations, and has an intimate knowledge of drilling conditions in and around Perth. From this knowledge, Lateral Drilling chose bentonite to hold the hole open when drilling through the sand. This universal drilling fluid suits a wide range of conditions. When clay was encountered, a polymer lubricant was added to the mix, and the rotational pressure on the drill was monitored so that it did not increase.
By monitoring the carryout of clay cuttings into the entry pit, as well as the rotational pressure and the thrust, Lateral Drilling was able to find the right mix of mud and tooling used.
The first two bores under the main drain were undertaken with a Vermeerå¨ D24 NAVIGATORå¨ horizontal directional drill – the first directional drill that the business bought – while the remaining bores were completed with a Vermeer D18x22 NAVIGATOR drill rig.
The Vermeer drills have an elevated operator’s station with gauges for thrust/pullback, rotation and water pressure placed between the operator and the drill, so that the operator can monitor the gauges while viewing the drill operation. Both drill rigs employ a rack-and-pinion drive system and have available torque to turn large cutting tools in difficult conditions.
A standard dirt drill head was used to open the hole in both the sand and clay. Initially it was thought that Lateral Drilling could complete the job by reaming and pulling the conduit back into the hole, but it became obvious that it would not be possible to keep the hole on grade without pre-reaming.
It was only necessary to use this through the mud sections, where a
150 mm diameter open-wing cutter was used, as the bentonite held the hole open in the sand. A 150 mm fluted reamer was then used when pulling the conduit back through the clay and sand.
A DigiTrak receiver was used to locate the position of the drill head every 1.5 m to ensure that the bore remained on grade.
Nine bores under Horrie Miller Drive ranged from 110 mm to 150 mm in diameter and each was 42 m long. Excavation was required at the base of an embankment to provide a level platform for the Vermeer D18x22 NAVIGATOR drill rig to bore under the dual carriageway. Since these bores had to be parallel to each other, at one metre spacing, the contractor used DigiTrak readings after each 1.5 m of boring. These bores also went beneath phone and optic fibre cables and water and gas mains.
All work was completed within five days, and a vacuum excavation truck was hired to keep the site clean.
Customer satisfaction
N.K. Contractors General Manager Nicholas Kalichis had not used Lateral Drilling prior to this project, but said, “I rate the work that they (Lateral Drilling) did as 11 out of 10. They showed up when they said they would, they knew what they were doing, their rates were good, and they asked for help when they needed it, but best of all, they finished three days ahead of schedule. This was a critical part of a job that ran on a tight schedule. I plan to use them for our directional drilling work in the future.”
Customer satisfaction is something that Lateral Drilling seems to achieve throughout its business. The bulk of its work involves drilling water connections for Water Corporation contractor Drilline (the Trenchless Technology arm of the Georgiou Group), with around 80 such connections made per month.
Drilline General Manager Kim Boyd said “We have had no problems with their work over a long period of time. They are competent and careful, and use good modern equipment on their jobs. They are an important part of the work we do, and have attended many of our in-house training courses.”
Apart from the D24 NAVIGATOR and D18x22 NAVIGATOR horizontal directional drills used on this project, Lateral Drilling also operates a Vermeer D7x11A NAVIGATOR drill rig – the third such unit that it has used since its inception.
The Martins’ went to Vermeer for their first drill because their combination of specification, backup and price was the best on the market and the service and reliability that they have received since then has given them no reason to look elsewhere.
Apart from the three drills, they have three mini excavators and three trucks in their fleet and hire other equipment as required. All machines are busy, and Mr Martin sees this continuing for some time along with the volume of work in the state. He will not rule out expanding the size of the company in this climate.
ID Equipment (formerly Lely West), the local Vermeer dealer, has worked with Lateral Drilling since its inception, and Mr Martin states “We bought one of the first Vermeer directional drills in Western Australia, and have always been very happy with the product, support and continuing comment from the guys at Vermeer.
“We have a great relationship with them, and they are always dropping in to our workshop or turning up on our jobsites, and are always willing to talk about new equipment that’s coming up or look at different ways of doing different jobs.”
Martins believes that good choice of tools and mud is the key to success in directional drilling and in this case it helped them complete this project three days ahead of schedule.