Decentralised Sewerage – Low Pressure Sewer Systems

Fraser Thomas have designed and supervised the construction of many decentralised pressure wastewater systems that have incorporated low pressure sewer systems.

Such systems can have considerable advantages over traditional sewer systems in rural, hilly and remote locations, or where connection to the existing Council sewer system is constrained due to overloading, leaks, or similar.

Recent projects completed in this area include:

Mt Taylor Subdivision, Fielding:

Detailed design of an innovative wastewater reticulation system to service a 120-lot residential development.  The wastewater system comprised on-lot Septic Tank Effluent Pump (STEP) system units, rising main and pressure sustaining valve arrangement with discharge to the local Council sewer.  The Council had a significant issue with its existing sewerage system due to infiltration and inflow.  This STEP system excluded infiltration and inflow that typically is the achilles heel of conventional sewer systems, and gave Council the confidence required to approve this development.  The wastewater system is maintained by Council.

Wainui Farm Park Subdivision, Gisborne:

Preparation of and lodgement of resource consents and preparation of expert evidence for the design of an innovative wastewater reticulation system to service a 40 lot residential farm park development in an environmentally sensitive location.  The wastewater system comprised on-lot STEP system units reticulated to an effluent detention tank whereby the flow rate and time of discharge to the Council sewer is controlled via telemetry due to severe overloading of the Council sewer in wet weather.

Hampton Downs Motorsport Park – Water and Wastewater Management Design:

Preparation of and lodgement of resource consents and design of a wastewater management system comprising an innovative conveyance system (STEP with three 110 m3 live storage tanks), wastewater treatment and an 8 hectare effluent land irrigation disposal system for a Motorsport park complex with a capacity of up to 5,000 participants and spectators.

Expertise provided:  

  • Surveying
  • Resource management planning
  • Civil
  • Environmental
  • Geotechnical

Project cycle:

  • Investigations
  • Preliminary design
  • Consenting
  • Detailed design
  • Construction observation
  • Completion certification