"Whole of Life" Cost Benefit

General

The Water Services Association of Australia (WSAA) has issued its draft National Sewer Code and included in this publication is the recommendation that Authorities apply WHOLE OF LIFE COST ANALYSIS when comparing tenders of differing materials.

The factors involved in such an analysis are:-

1. Initial cost of supply
2. Construction costs
3. Maintenance costs
4. Material life cycle
5. Replacement costs

With the introduction of vitrified clay pipes into the Australian market, Authorities and Consultants now have access to a high quality, consistent performing pipe and joint which offers a projected life of 150-200 years. This is well in excess of the 30-50 years life that can be expected from the various types of plastic pipes.

WHOLE OF LIFE COST ANALYSES should be a mandatory exercise for Authorities and Consultants to ensure best asset management practices. Whilst such practices are generally employed in major sewerage schemes, pressure by Developers to achieve low cost subdivisions has resulted in material selection being limited to initial costs only.

Auckland City (New Zealand), after consideration of all the above factors, legislated by way of a bylaw to ensure that vitrified clay pipe was the only approved pipe for its public sanitary sewer system. In 1997, Wellington City (New Zealand) also made the decision not to allow the use of uPVC in its public sewer systems and circularized Consultants accordingly.

The decision by the Auckland City Council was mainly based on:

• A longer projected life provided an expectation of reduced spending from $12.5M to $5.0M annually to keep its sewerage system operative.
• Because clay pipe does not distort its shape (does not become oval) it should provide a framework to line or grout in future rehabilitation.