SEQUD were approached to tender for works at Sumner & Monier Rds, Sumner Park. We were hoping to be awarded this tender as our drilling crews were keen to sink their teeth into a project with such interesting and challenging requirements.

Ground conditions in the area had previously proven to be soft rock, which led us to use our Vermeer D50 x 100 machine coupled with the Mud Motor. Works entailed a combination of day and night drilling over a period of four months. Two of the drill “shots” required the crossing of the Centenary Highway and on and off ramps. This was mainly done during the night due to the traffic volume. Some of the other locations along with the Centenary Highway were done at Night due overhead high tension power lines causing interference with location equipment.

The most challenging aspect of the project was the drilling under the Highway where we had to achieve over a ten metre change in elevation from the top to the bottom of the bore over a limited distance. This was done by utilising bore planning software, allowing us to see how the elevation and inclines would affect the drilling equipment and outcome of the bore.

In all, the project was completed with minimal problems. Thirteen kilometres of product pipe (seven 140mm conduits) was installed in eleven drill “shots” ranging from 30 metres through to 180 metres. The end result was a satisfied customer and no roadway or highway damage.

The best machine for the job was the Ditch Witch JT2020 with a 750 Tracker Locator. The ground and soil conditions were determined to be Brisbane Schist through a combination of local knowledge and the rock face present below the structure. Due to these conditions a Ditch Witch rock head was decided upon to aid in steering the bore and swabbing the hole.

On the interior of the Cathedral a 250mm hole was drilled vertically through concrete giving the drilling operators a target exit point/zone for the bore. There were several footings to negotiate on the way to the target exit point. After two solid days of hard work from both operators and machinery the drill emerged within the target zone.

The drill was a total length of 30 metres with three 40mm Conduits being installed. Also installed was a Type 4 Pit.

SEQUD were approached regarding the possibility of a directional drill though a hillside for a new power station. After numerous discussions and several options the final bore plan of five 140mm Electrical conduits and an adjacent 160mm Fuel Line through the hill was agreed upon. The machine that best suited the expected conditions was the Vermeer D50 x 100 Directional Drill, which has rock drilling capabilities, used alongside our 3.5 Mud Motor and Eclipse locating system.

Throughout the course of the job there were numerous obstacles to overcome. Pilot lines were successful on first attempt, however opening the hole up to both 400mm and 600mm proved to be far more challenging. Rock up to 200mpa was encountered in areas which places some strain on the equipment. Within this very hard and solid rock was found to be a much softer variety, which in turn put additional strain on equipment resulting in one challenging situation after another. In addition to this the layers of rock formation and the angles on which these layers were made drilling difficult. During the drilling wet weather was encountered as a side effect of a cyclone in the region, which caused worksite flooding. After much frustration at the constantly varying ground conditions and strain on the equipment, the reward of a successful 140 metre bore for both Electricity and fuel lines, through the hillside was given. We were also asked to frill a third line for an additional 140mm Electrical from the top of the hill down to the exit points. This was approximately 60 metres on a grade on -32%.

The soil conditions were known to be sandstone to mudstone with a mixture of clays from the geotechnical report supplied by the customer. To avoid any difficulties with hard ground in such a delicate environment the Vermeer D50 x 100 machine was used as it has greater capabilities in hard ground, reducing the need for start stop and slow drilling.

Due to the sensitive environmental situation with our bore path running directly under the creek we used environmentally friendly drill fluids to assist with the sandstone conditions. This meant that if an instance arrived where drill fluids could enter and mix with the water, no harm would be done to the quality of the water or the environment. To avoid any instance of the drill fluids entering the water flow the drill was done at a depth of six metres below the bed of Oxley Creek. In total the completed bore was 120 metres and was completed on target and on time, to the satisfaction of both SEQUD and the customer.

We have done drilling shots from 30 metres through to 50 metres in length so far. Directional Sewer drilling has been successfully done in ground conditions from that of Clay right up to harder ground conditions like Sandstone, Shale and Porphyry Sandstone. We currently use the Ditch Witch JT 2020 with both the Subsite and Eclipse locating systems.