Central Park in Sydney’s CBD is a unique urban hub powered largely by a centralised tri-generation thermal plant. The plant provides the energy demands of each building on site via an underground thermal piping network. To expand this energy network to service surrounding infrastructure, a trio of trenchless crossings were dug beneath Broadway, beginning at an unusual depth of 20m below ground.
Brookfield Infrastructure acted as lead contractor, with Australian Wide Directional Drilling (AWDD) brought in to complete the trenchless installations. Works began on January 4, 2016 and were successfully completed by February 9, 2016.
Horizontal Directional Drilling (HDD) technology was chosen to complete each bore of 70m in length, using a Vermeer D100x120 HDD rig.
Four pipes and two communications conduits were installed in total, with 2x125D pipes sharing a single bore, and the remaining 2x500D pipes installed in separate bores. The pipework will provide a chilled water (flow and return) service as well as a recycled water and sewerage network.
To connect to the underground thermal plant at Central Park, each bore was drilled from the existing basement 20m below ground. The bore was then terminated at a depth of 4m on the other side of ‘Broadway’, one of Sydney’s main arterial roads, and adjacent to the grounds of University of Technology (UTS).
Once the new UTS buildings are developed, a pit will be excavated to allow access to the pipes which will then enable thermal service to the new UTS facility.
CHALLENGES AND TECHNIQUES
Because the bore had to be completed entirely below ground, special tooling and logistics had to be considered. According to Corey Passlow, General Manager at AWDD, their biggest challenge was getting the machinery down into the basement.
“As you can see in the pictures, we brought in a 300 tonne crane to lift all of our equipment. This included excavators, drill rigs, trucks, recycles and site sheds.
“Everything also had to be brought into the basement within daylight hours, so it was a pretty busy day for everyone on the team,” said Mr Passlow.