South Western Interceptor HDD portion
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Service: Trenchless Pipe Construction
Cost: $1.8M
Started: Jan 2011
Completed: Aug 2011
Client: WaterCare
Engineer: SKM
The Project was part of the larger South Western Interceptor Extension project; run as a JV between Fletcher Construction, Brian Perry Civil and PipeWorks.  PipeWorks were contracted to complete two Horizontal Directionally Drilled installations of a 1,000mm HDPE rising main.
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Rewriting the book

  • Largest Diameter HDPE Pipe installed by HDD in New Zealand
  • 1.35m bore drilled through sandstone
  • Drilling at grades as low as 1% and around multiple compound curves.

Project Scope

  • Install 630 meters of product pipe (in two separate shots) through a pre-reamed 1350mm bore.
  • Variable geological conditions encountered; ranging from sandstone to silts & clays.
  • Grades ranging between 1.0% and 2.0%.
  • Setup in busy level two main road.
  • Weld and Test two 1.00 meter diameter HDPE pipe strings totally 630 meters in length and prep for insertion.

Project Outcomes

  • Successful installation of two of the largest diameter drill shots in New Zealand.
  • Due to effective cleaning and reaming of the bore and high standard of drill fluid monitoring and recycling combined with detailed pipe insertion methodologies pipe pull pressures as low as 10% of the total pipe weight achieved.
  • Stringing out and welding of 300 meter and 330 meter strings of 1 meter diameter HDPE pipe in restricted traffic conditions while having only minimal impact on traffic flow and residential access was an achievement in itself; access to only one property for a single day was restricted during the 6 month project duration.