Hawthorn Sewer Relining Program

Abstract

As of May 2017, there was a total of 9,200km of gravity sewers located throughout the Yarra Valley Water (YVW) service area. Some of these gravity sewers are more than 100 years old and have been shown to be prone to sudden structural failure. To avoid the risks associated with structural failure, YVW operates a program to proactively inspect sewers deemed to be high risk and rehabilitate them as required. One of the areas with aging infrastructure is Hawthorn, which is an inner suburb of Melbourne, Victoria settled in the late 1830s, most of sewer infrastructure for this area was installed in the first decade of the 20th century (1900 – 1910). YVW uses a criticality approach based on risk and likelihood, to proactively identify the sewer pipelines that will be renewed. In the case of gravity reticulation sewers, pipe structural condition is used as the indicator of “likelihood” and consequence is replaced with “criticality”. Pipes with a condition grade of “4” or “5”, are estimated to have remaining service lives of <5 years and <1 year respectively, and they are prioritised accordingly. YVW determined that there might be benefits from rehabilitating ageing infrastructure in an entire area, rather than targeting individual sewer lines. Hawthorn was chosen for this new approach as the assets within it contain a highrisk profile (53km of sewer reticulation pipes); and more than 95% of sewers within the suburb have theoretical condition scores of 4 or 5 (>91% with a score of 5). The benefits expected from an entire area program included; - reduced customer inconvenience, - increased efficiency to complete work, - reduced areas of high risk for sewer blockages or collapse, and - reduce rehabilitation costs. In addition, YVW would have a performance benchmark for a fully sewer rehabilitated area. We used Trenchless technologies were used as much as possible to reduce customer interruption and increase productivity. This program was successful for YVW and its Contractor Partners, as it achieved its targets to reduce customer interruption, increased positive feedback from customer and reduced customer complaints. The program was completed within the 10 months and delivered within budget. It is too early to measure the full success of the program, but over the last year there has been one blockage on the renewed pipes, which indicates a great outcome for the program. Page 1 of 9 No-Dig Down Under 2019 HAWTHORN SEWER RELINING PROGRAM Alberto Vela and Jamie Lynch - Yarra Valley Water, Mitcham, Victoria, Australia

Techniques