Mick Heffernan from SEQUD met with Mike Gurney and Delfin Project Engineer James Devoy onsite to discuss the options on how to reinstate the storm water pipe.
Open trenching to install a new line was not an option. The pipe was 60 m long, manhole to manhole, with depths ranging from 2.7 m to 1.3 m under retaining walls and across the back boundaries of Delfin’s display homes which included established fencing, gardens and an elaborate water wall feature.
At first it was decided that the best option was to try to drill through the collapse but this proved difficult with approximately 30 m of collapsed pipe, old PVC and a combination of sandstone pieces and pea gravel materials in the backfill. SEQUD considered pipe bursting by drilling through with a horizontal directional drilling machine to ensure line and grade was maintained and then pulling back the Quick Lock burst rods of an 800G Grundoburst machine.
SEQUD approached Peter Decker from TT Asia Pacific to see if it was possible to pull back through the collapsed portion of the pipe. Mr Decker advised that it would be possible and recommended contacting Ipswich Water, who already own and successfully operate Grundoburst equipment, one of their units being a Grundoburst 800G (80 Tonne) machine with the correct accessories.
Article continues below…The challenge was discussed between Ipswich Water and SEQUD and it was agreed that while SEQUD would carry out the directional drill shot and pull back the burst rods, Ipswich Water would prepare the excavations, set up and pull back the expander and install the new 250 mm polyethylene pipe.
The directional drill shot was successful, collapsing approximately 30 to 40 m of the pipe with little resistance encountered during pilot boring. It took four hours to drill through and pull back the burst rods. When Ipswich Water set it up, it took approximately two hours to pull the 250 mm line back and remove all accessories with very little resistance from the collapse. As a result, there was no surface ground movement that might affect the retaining walls or water feature. Once the new pipe was installed, Gurney Earthmoving completed the house connections and reinstatement works without causing much disturbance to the display homes.
The combination of directional drilling and hydraulic pipe bursting may be an unusual mix of Trenchless Technology but in this case it achieved the best results for all concerned and was a success for all involved. Most importantly, no disruption was caused to the properties, public and services during the replacement.
For further information on the companies, equipment and techniques used please contact Daryl Taylor of SEQUD on 07 3814 4218 or Peter Decker of TT Asia Pacific on 07 3420 5455.
