Strategies of maintenance in storm sewers in Bogotá Colombia by using estimates of operational and flooding reliabilities

The purpose of this research was to suggest strategies for maintenance activities on a specific portion of Bogota’s sewer network (with a surface of 4515 ha and approximately 12800 combined and separate sewer pipes) based on operational and flood reliability calculations. The information used for achieving the expected results of this study was provided by the Bogota Water and Sewage Company (EAAB): (i) a detailed data base containing damage reports and complaints from users from 2003 to 2009; (ii) a data base with information of sewer pipe features. With the calculations made for defining a specific measurement of flood and operational reliability for each sewer pipe, the zones with greatest deficits of maintenance activities were identified. It was proved by using statistical tests based on the Kruskal-Wallis approach, that the features of sewer pipes that mainly cause variability on the reliability in the study area were the diameter, the sewer type (combined or separated) and the urban area to which they belong. Based on flood and operational reliabilities, a feasible (Benefit Cost Ratio BCR=1.18) preventive maintenance strategy is proposed, for which EAAB would obtain approximate annual savings of USD 832000.