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CONFERENCE: NZWWA 50th Anniversary Conference, Christchurch, New Zealand, September 2008

ABSTRACT:
Low pressure sewer systems have significant advantages over conventional gravity collection systems under certain physical conditions.  These advantages relate to both installation and operation.  The advantages include reduced capital cost, the elimination of peak wet weather flows, and the associated overflows and treatment plant failures.  A major obstacle to the use of these systems is determining the best implementation and ownership model for the Territorial Authority (council). 
There are a number of different ownership models which could be used to implement low pressure sewer systems.

• A Traditional Model, the council own, operates, and maintains the entire network and on site components.
• Model 1, the council owns the entire network and on site components and property owners maintain the on-site components.
• Model 2, the council owns the low pressure network and property owners own the on site components.  The council is responsible for maintaining the on-site components.
• Model 3, the council owns the low pressure network and the property owners own and maintains the on site components.

Each of these models have advantages and disadvantages in terms of cost, consistency of standards, and equity. 
In order to implement a low pressure sewer system council s need to change wastewater bylaws, engineering standards and develop a public education strategy before implementing a system.  This is required to ensure the following.

• Responsibilities for the network will not be confused.
• Engineering standards are consistent and deliver a high quality, reliable system. 

The public accept and understand low pressure sewer systems.

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