Material Pipe Useful Life Material Pipe Useful Life Type Diameter Type Diameter ALUFLO 100 ST-D 100 B-ARCH 80 ST-GL 60 C-ARCH 80 ST-SW 100 CC 80 UNKNOWN 100 CI 100 UPVC 100 CU 40 VC 80 DI 0 100 DRUM 50 Plant Useful Life Mechanical Plant 40 Electrical Plant 25 Civil Structures 100 Table 15 Asset Life Expectancies Used in Re-valuation 5.5.1 Data Confidence The data quality is regarded as good. Of the pipes recorded in the asset management database one or more of the attributes (age, diameter or material type) was missing for around 1% of records. Estimates were made for the missing data based on adjacent pipes or the known history of land drainage in the area. Other assumptions included in the financial planning are shown in Table 16 Assumption Confidence in Risks of Incorrect Mitigation Measures Assumption Assumption Population growth Medium Either decrease rate Review in-house continues within the base affects income growth forecasts medium to high Or increased demand following the growth projection on assets and Statistics NZ accelerated forecasts due to be investment published in early 2015. Use BERL forecasts and demographic & local intelligence Deterioration of High Accelerated renewal Develop a condition underground assets programme assessment continues in line with programme and guideline useful lives improve asset management information Page 80