What happens when a sewer line needs to be constructed beneath a railway? Visions of major closures, transport headaches, frustrated contractors and dollar signs start appearing from all directions. Not however, if you have the skill and accuracy to work within a tight deadline to get the job done.
The Gold Coast City Council recently required a gravity sewer line to be installed via trenchless technology along the Old Pacific Highway in Pimpama. Construction involved the installation of a concrete enveloper pipe and gravity sewer beneath a section of Queensland Railway within a tight time frame of just 48 hours.
Steve Mitchell, Project Engineer at Edge Underground, subcontractor chosen for the works, said that the railway had to re-open after 48 hours “no ifs no buts”. Because of this, planning and organisation of the construction had to be highly effective and closely monitored.
“Organising appropriate crews for the job was a top priority, as well as selecting the most appropriate tools, materials and drilling equipment.
“Contingency plans for changing ground conditions, disposal of drilling mud, mechanical failure and supply of materials also had to be prepared before the works could begin.
“Each aided in the speed and smooth execution of the project, and gave us a clear action plan and backup if something unexpected were to take place,” said Mr Mitchell.
A DN600 Class 4 butt jointed concrete pipe was chosen as the enveloper for the DN450 PE gravity sewer. This was installed via a laser guided microtunnel of 350mm in diameter, followed by the pilot being reamed out to 700mm diameter while the DN 600 concrete jacking pipe was installed. The gravity sewer was then centralised and grouted within the concrete enveloper.
Twelve hours of inclement weather meant that access tracks to the site had to be reinvented midway through the project.
“Thankfully, ground conditions were not a challenge during this installation being stiff, self-supporting clays, however the poor weather meant that we had to be up early to hurriedly fix the tracks before work could re-commence.
“This is where our pre-planning and coordination shone, and we were able to get back to work within a short amount of time.” said Mr Mitchell.
“Despite the challenges we were able to get the project completed both on-grade and within a tolerance of 10mm vertically and horizontally, which is a great success for the team,” said Mr Mitchell.
Edge Underground utilised two, four-person crews working 12 hour shifts to complete the installation.
Stuart Harrison, Managing Director at Edge Underground, says that the company’s personnel is what makes Edge Underground a reliable choice when it comes to choosing a microtunnelling contractor for a time-sensitive installation.
“We have experienced personnel ready to undertake work around the clock, across Victoria, New South Wales and Queensland. This gives us an added advantage when it comes to projects requiring a fast turnaround,” says Mr Harrison.
“We also have the knowledge and experience required to produce accurate results via our Vermeer AXIS Guided Boring System. We also consistently produce successful results on the first attempt.
“This is definitely a top priority when it comes to completing projects within a strict deadline. Railway closures are a major inconvenience to communities and businesses so the ability to get in and out quickly and safely is something that the Edge team can be proud of.”