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Tackling inflow and infiltration

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Sewerage networks are typically designed with a contingency to allow for inflow and infiltration, and it is not unusual for storage systems to be added to existing sewerage networks to increase capacity to cope with inflow and infiltration, particularly during rain events.

While these contingencies result in large and costly infrastructure and pumping systems, many water authorities still report increases during normal rain events of between 5 and 10 times average dry weather flow (ADWF), which overloads these systems.

With many water authorities wanting to work towards reducing environmental impacts and achieving zero carbon emissions, addressing I/I both in new constructions as well as repair and rehabilitation of existing assets is increasingly important.

The benefits of addressing I/I are vast and include:

  • Reduced operation and capital costs
  • Lower power consumption and CO2 emissions
  • Reclaiming network capacity (supporting increased urban infill with existing infrastructure)
  • Less wear and tear on pumps, pipes and assets
  • Reduced potential for overflow
  • Less potential for formation of voids and associated damage to assets and surface structures
  • Lower insurance and litigation risks
  • Reduce pressure on already stretched personnel

While it may not be practical to completely eliminate I/I, it is possible to easily identify catchments and assets that are significant contributors, even with limited budgets or personnel.

It is also necessary to realise that I/I management is a long term strategy involving a combination of assessment and repairs.

Delaying starting the process (which can occur as the problem seems insurmountable) will only translate into a more costly program down the track, because leaks don’t get better on their own.

Sewer manholes generate a disproportionate amount of I/I and there are a range of trenchless repair and rehabilitation solutions for manholes that can be used to help quickly and cost effectively reduce the inflow and infiltration from these assets.

ISC Services has put together free informative downloads to help water authorities better understand the sources and causes of inflow and infiltration to help with urgent repairs and ongoing management.

Click here to find the below free guides:

For more information visit the ISC Services website. 

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