Directional Drilling Projects for South East Water Limited
The LPR results for Mirang Avenue indicated that only the first 520m of the 1050m length had a high risk of failure and therefore needed to be replaced along a parallel alignment. All four failures that had occurred since March 1999 were along this section.
For Brasser Avenue it was decided to construct the new rising main on a completely new alignment. The existing main was situated in a high-risk location adjacent to the Mornington Peninsula Freeway reserve, a 200mm diameter transmission-pressure gas line and in an easement at the rear of private properties.
The new alignment for Brasser Avenue was to be in the nature strip in the front of businesses in the industrial estate. Allowing access to these businesses during construction was of paramount importance. Hydraulic studies of the Brasser Avenue pump station revealed that the rising main diameter could be reduced from 150mm to 100mm internal diameter (ID) hence allowing 100mm ID polyethylene (PE) pipe on 250m coils to be used for construction of the new rising main. This not only avoided laying out long pipe strings during pullback resulting in blocked driveways but it also had the added benefit of minimising the number of joints along the pressure main.
Envirosafe Construction Pty Ltd in conjunction with Blaxland Pacific Pty Ltd and Enetech Pty Ltd (now Tenix Alliance Pty Ltd) in conjunction with Rowlands Underground Technology (RUT) were chosen to construct the Brasser Avenue and Mirang Avenue rising mains respectively.
The principal contractors, Envirosafe Constructions and Tenix Alliance, would carry out the reconnections of the new and abandonment of the old rising mains and any other associated duties while Blaxland Pacific and RUT undertook the directional drilling works.
SETOUT & ASSET LOCATION
Asset Location, Survey Set-Out and Drill Head Tracking
RIG SETUP & PIPE DELIVERY
100mm ID PE pipe delivered on two 250m coils to Brasser Avenue, Dromana
As Mirang Avenue was to be replaced using 250mm ID (315mm OD) diameter PE the 12m pipe lengths were joined using butt and electrofusion welding.
Welding at Brasser Avenue and Mirang Avenue
Pipe end preparation for welding and resultant pipe strings at Mirang Avenue
commenced at Brasser Avenue using an Aroco BoreKing drilling rig, while a
Vermeer D33x44 was used at Mirang Avenue.
RUT’s drilling rig and mud-mixing unit arrive at Mirang Avenue, Mt Martha
RUT’s Vermeer D33x44 at Mirang Avenue, Mt Martha
Blaxland Pacific’s Aroco BoreKing drilling rig at Brasser Avenue, Dromana
CONDITIONS & DRILLING FLUIDS
A ‘frac-out’ of drilling fluids.
Frac-outs can also occur if there is a weakness in the ground close to where the bore shaft is being drilled. The picture above shows a frac-out occurring adjacent to where previous repairs had recently been completed.
RUT and Blaxland Pacific had eductor trucks on standby in the event of a frac-out. The eductor trucks were also used to remove drilling fluid from the exit shaft of the borehole during pipe pullback. An approved dumping site is critical at this point, as not all tips will receive drilling fluid as waste.
RUT’s eductor truck with separate storage tank at Mirang Avenue, Mt Martha
A 450mm backreamer attached to the 315mm OD PE ready to begin pullback at Mirang Av.
Pressure testing of the newly installed rising mains was undertaken to ensure that the pipe pullback had not weakened or damaged the pipe and the welds.
Water pressure tests confirmed the integrity of the pipeline after installation
Comments such as these are what any project manager likes to hear and are a good reflection on horizontal directional drilling construction methods and those companies selected to undertake them.
Article by Declan McCreesh