Figure 17. Havelock Reservoirs before and after upgrade All the ferro-cement reservoirs (except one) at Havelock were replaced with a sectional steel tank in 2011. The single reservoir was retained for emergencies. A more rigid schedule of inspection and maintenance of storage units will be incorporated into the new asset management information system and referenced to the Water Safety Plan (formerly Public Health Risk Management Plan) developed for each supply area. Reticulation - Asset Condition - The useful life of buried pipes is dependent upon a many inter-related factors - manufacturer, operating pressures, soil conditions, groundwater levels, water chemistry, operational methods, installation workmanship, surface loading, depth and quality of bedding and surround materials, jointing techniques, etc. The rate of deterioration of the pipe wall, joints, fittings and service connections is a product of a combination of the various factors. Ultimately the combined effects will result in one of the components of the pipeline to fail. However because of the complexity of the inter-related factors it is not easy to determine a predominant factor and subsequently identify a trend that allows reliable forecasts into the future. Some of the steel pipes laid in the ground are protected from corrosion by a coating of zinc galvanisation. High ground water levels and aggressive soil chemistry can cause premature failure of the zinc coating and accelerated steel pipe walls. This has been identified as a problem in the Awatere scheme and other areas. Galvanised steel pipes laid in an inert environment have a life expectancy of 80 to 100 years. In the aggressive local environments this has been reduced to 50 years. Further evaluation is required however as corrosive soils can occur in relatively isolated, localised patches. Accurate assessment of the remaining life expectancy of the reticulation will require further effort to assess the remaining asset stock. A project for the condition assessment of buried pipes is included in the asset management improvement plan. There is some evidence of reduced life expectancy for small diameter PVC and ABS pipe that has been jointed with solvent welded socket and spigot joints. A technique that requires a rigorous standard of workmanship. Early jointing practices by some installers did not always follow manufacturer’s instructions and premature failure at joints has become evident. The planned life expectancy of the ABS pipes and PVC pipes up to and including 50 mm nominal diameter has reduced to 40 years within the Awatere reticulation. Asbestos cement was a popular material for the manufacture of pipes from the 1940s through to 1980. Experience has revealed a number of common failure modes. Acidic waters are capable of leaching the cement out of the asbestos/cement matrix causing softening of the pipe wall and premature failure. Historical evidence has shown that steel bands within some types of joint socket are prone to corrosion and bolted gland joints can also corrode. Hillsides that are subject to erosion and the formation of under-runners can have the bedding and support of pipelines undermined. AC pipe is a relatively brittle material it needs to be adequately supported and point loading needs to be avoided. Page 57