Construction of replacement sewer mains in congested urban environments has led councils and contractors in New Zealand to explore faster installation techniques, avoiding disruption to the local population.
Nestled away in the idyllic Wairarapa region lies Masterton, a small city that is leading the way in adopting innovative Trenchless Technology techniques.
The Masterton District Council’s (MDC) ongoing sewer renewal project, which costs between $AU1.5-2.5 million annually over a 15 year period, is a recent example of the static hydraulic pipe bursting – cartridge method pit-to-pit (STPB-CMPP) technique being applied to a live sewer replacement.
STPB-CMPP is being successfully applied during the ongoing Masterton works by project contractor Higgins, allowing them to install new pipes and renew existing pipes efficiently and cost-effectively.
Approximately 4 km of DN100 pipe in sizes 100-225 mm have been successfully installed so far using the STPB-CMPP method during the Masterton sewer renewal project.
The pipe-lengths installed varied from 1-6 m, depending upon the on-site conditions available on each street upgrade.
When installing pipes with the STPB-CMPP method, an installation rate of 1 m per minute is often achieved, and in some cases, twelve household sewer laterals have been renewed per day.
The works were performed using a HammerHead static hydraulic pipe burster model PB30 with 30 tonne pull force and a Trackto-Technik static hydraulic pipe burster TT with 800g-80 kn pull force.
Higgins Asset Owner Glenn Malcolm said Masterton’s ongoing sewer renewal project had been progressing well, despite some economic and environmental constraints.
“The amount of effluent being treated at the MDC Waste Water Treatment Plant and being disposed of has been a constraint, however, the well-structured replacement program currently in place ensures that not only the sewer mains but the lower laterals are being replaced, lowering infiltration and therefore meeting the council requirements due to lessening the amount of effluent being treated and disposed of.”
In addition to the environmental constraints, the Masterton sewer renewal project has additionally encountered problems surrounding some of the lateral service connections.
Iplex Pipelines representative Todd Randell said traditional methods such as the application of wye junctions to the lateral service connections were expensive.
“Quick-fit snap-on fittings (also known as “÷quick-fit saddles’) were sourced in Masterton, resulting in a much quicker installation time during the project.
These saddles provide a clean invert resulting in less maintenance for the asset owner,” Mr Randell said.
“÷Quick-fit saddles’ are commonly used alongside the STPB-CMPP method.
Mr Malcolm said that this method of pipe bursting was the most suited to a project such as the sewer renewal project in Masterton “This method of pipe bursting offers a cost-effective alternative to the public cost, a primary driving force for the MDC when approving the bursting method.
“The secondary being public disturbance levels, with most sewers being relatively shallow in the Masterton District, open-cut can be achieved with an experienced crew at similar rates, however, deep lines, reinstatement, complex road crossings and navigating via existing utility services is where the bursting methods saves on costs.”
Mr Malcolm said.