Waipoua Forest Wastewater Treatment Wetland

Works Overview

Wetland Solutions completed this project on-time and within budget. Existing facilities remained operational at all times during the construction.

This project required a “turn key” approach, input from design engineers and a variety of suppliers and contractors were successfully coordinated.

Works included:

• Service of existing sewage system
• Restoration of existing sub-surface flow treatment wetlands (2)
  
• Design, construction and installation of 80m² contact filter (sand filter)
  
• Installation of 650m rising main
• Installation 8,400m UNIRAM
• Ground works reinstatement
• Operating and maintenance manual
  
• Training of Waipoua Forest staff

Backgound

The Waipoua complex consists of 7 houses, a visitor centre, workshop, office building, 160 person campground, 2 kitchens, 10 tourist cabins, caretaker’s cottage and 2 ablution blocks with showers.

The existing on-site effluent disposal system consisted of a collection system utilising septic tanks and sewers to two sub-surface flow wetland cells with shallow trench disposal.

Clear felling of an upper catchment above the disposal area in November 2000 combined with winter rainfall conditions led to an elevated groundwater table saturating 30% of the existing disposal area, resulting in failure.

Purpose

• The project objectives were to provide a high level of wastewater treatment by designing, constructing and installing a contact sand filter and relocating the failed disposal area.
  

• It was paramount that new and existing treatment facilities and the final disposal systems were located so as to not adversely affect the spiritual and physical qualities of the Waipoua River.

Scope

• Clean and inspect all septic tanks, fit risers and eliminate ground/surface water intrusion

• Install grease traps for campground and hall kitchens

• Design, construct and install new sand filter to further treat effluent

• Install new pump chamber and rising main to new disposal irrigation system

• Replace sub-surface flow wetland aggregate with Meltzer slag

Disposal Area	Subsurface Flow Wetland (before)	Grease Trap Installation

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