The planned life expectancy of asbestos cement pipes in Marlborough has been adopted from the New Zealand Asbestos Cement Watermain Manual 2001 . The manual was compiled based4 on statistical analysis of pipe test results collected from a national survey of twenty water suppliers throughout the country. Some pipe sampling and testing of AC mains has been undertaken in the Marlborough area as the water is known to be aggressive to the cement bond. Pipesapes are removed wherever possible during routine maintenance and are visually inspected and photographic records taken. The water abstracted from the shallow aquifers of the main river valleys (Blenheim, Speeds Road, Picton, Renwick and Havelock) has a naturally low pH (around pH 6) and is aggressive to the cement binder in asbestos cement pipe. The water leaches the cement from the AC matrix. Deterioration of the cement pipe wall is reasonably constant and therefore small diameter, low pressure rated pipes with relatively thin walls will degrade to the point of failure more readily than the thicker walls used for larger diameter or high pressure rated pipes. Figure 18. Remaining Life of Watermains The table shows the aggregated length of main that has exceeded its nominal useful life. More than 90 kms of mains have a life expectancy of less than 10 years ie; it has deteriorated to the point where it has become uneconomic to repair the pipe and it will need to be replaced. There is around 15 km of small diameter (50 mm- 75 mm) galvanised steel, 0.5 km of 50 mm ABS and the remainder is asbestos cement (51.5 kms in the Awatere scheme.) The theoretical life expectancies that have been adopted suggest there is a significant issue with water mains that have reached the end of their useful life. If this were the case the quantity of failed mains and subsequent increase in repair activity would be marked. This is not the case in practice. The quantity of bursts and mains repairs has seen a decrease in recent years. However, Figure 18 does emphasise the need to undertake further work to reappraise the condition of pipelines and adjust the assumed useful life of material types (or other groupings) in order to deliver better predictions for future planning. Pipe sampling, on-site condition assessment and non-destructive pipeline surveying are being investigated to improve the data 4 New Zealand Asbestos Cement Watermain Manual 2001 (NZWWA, August 2001) Page 58