As custodians of our most precious resource, water authorities are charged with safeguarding both our communities and our ecosystems – and that means stopping sewer spills before they happen
Water is the driving force of all nature; every individual, community, industry and ecosystem depends on it to thrive – and as the world’s driest inhabited continent, Australia needs every precious drop.
Our wastewater networks play a vital role in water security, and environmental and public health, but if these systems overflow, they can introduce harmful contaminants that can impact communities, kill aquatic life, disrupt food chains and cause harmful algal blooms.
As more than 80 per cent of Australia’s native flora and fauna are endemic, many of which are already endangered, sewer spills can have devastating consequences for our unique ecosystem.
Protecting our waterways is a huge priority for utilities, but preventing overflows is easier said than done, especially as heavy rainfall events become more frequent.
ISC Services Director, Dennis Bentink, explained that when sewerage networks are overloaded or blocked due to soil ingress, root intrusion or other restrictions – then sewage can overflow from structures and pipes into the environment.
“Inflow and Infiltration (I/I) is unwanted groundwater or stormwater entering sewerage collection networks, which if unchecked leads to overflows,” he said
“The end result of I/I is increased operational costs as well as excessive and early damage to expensive sewerage infrastructure and even surface structures and roads.
“Not only are there environmental impacts, interruption to public amenity and negative public perceptions, but the costs of managing these overflows can also be quite significant.”
Cascade effect
I/I from groundwater and even small rain events can result in increased pump operations with increased power consumption and treatment required that have negative environmental impacts even if the I/I doesn’t result in an overflow.
While it is not practical to totally eliminate all I/I, Mr Bentink said that it is possible to adopt processes and smart construction techniques to prevent early onset of I/I in new assets and by utilising systems that address I/I sources, asset owners can reach a manageable and sustainable level of I/I control.
This results in environmental and financial benefits for water authorities and communities who ultimately pay the price for inflow and infiltration.
When it comes to the main causes of I/I, according to Mr Bentink, sewer manholes generate a disproportionate amount of I/I.
“The most common entry point for I/I is failed joints, particularly the chimney or neck of maintenance holes where there are often multiple joints close together and near the surface,” he said.
“Despite the best of work on new maintenance holes and pump stations, ISC Services is often contacted by contractors needing to fix a leak in a new joint, particularly in manholes and pump stations, which can be caused by a range of issues and the repair of premature failure of precast joints can be costly.”
Preventing the development of I/I is the simplest and best approach for new structures being constructed and includes the use of quality, well proven components, appropriate design and good installation techniques.
“Simple innovative approaches such as implementing Gator Wrap, a flexible high-quality external wrap, designed for new precast joints in pits, manholes and pump stations, will help cost effectively prevent early development of leaks as well as soil and root ingress,” Mr Bentink said.
Infi-Shield® Gator Wrap is a stretchable, self-shrinking, intra-curing halogenated based rubber with 500 per cent elongation and a full face of butyl mastic adhesive, which wraps around the outside of the joints on new structures to prevent development of premature leaks.
Gator Wrap prevents infiltration by providing a water-tight seal around any precast concrete manhole, catch basin or concrete pipe joint. Gator Wrap resists harsh soil conditions and also provides a root barrier and stops soil ingress at any crack or joint. Mr Bentink said that one of the key benefits of Gator Wrap is that it installs easily with no primer and no special tools, and can be immediately backfilled.
“Its EPDM rubber with butyl mastic adhesive achieves 500 per cent elongation and so will prevent the formation of leaks at joints, even if there is settling or movement of the structure after construction. Gator Wrap will reduce the long-term costs associated with infiltration when used on all new precast concrete constructions, and can even be used on PVC and FRP pipes,” he said.
“With a design life of at least 50 years, Gator Wrap represents a great return on investment and insurance against costly repairs.”
Ultimately, Mr Bentink said that the first step towards minimising I/I is to understand its possible causes and identify potential sources in your wastewater system.
“The simplest way to do this is to look at how sewage flow changes during and immediately after rain events. If sewage flow increases then rainwater and/or ground water is entering the network,” he said.
“Once you’ve identified the sources, you also need to know what your options are for addressing these.”
To help utilities with both of these steps, Mr Bentink has published a series of helpful resources on ISC’s website.
Solutions like Gator Wrap are a simple and easy way to tackle I/I, but especially for larger scale or more complicated challenges, Mr Bentink said that there are options for councils and water authorities to get specialist contractors to do detailed investigations.
“Working with specialists and contractors experienced in I/I will allow you to determine what your I/I assessment and management goals are and tailor a staged plan and program to suit your specific circumstances and budget,” he said.
“We’re here to help, so if you need it, get in touch.”
