Unitywater (QLD) has inspected more than 56,000 properties across the Sunshine Coast, Moreton Bay and Noosa regions as part of its Source Detection Survey.
It has found a number of residents with illegal plumbing connections, placing undue stress on the sewerage network – especially during times of significant rainfall.
Between 1 July 2010 and 31 March 2015 the survey work, done through smoke-testing of underground pipes, identified 2,744 customer-related defects.
These were most commonly Overflow Relief Gullies positioned too low (1,509), damage to inspection openings (421) and cracks to house drainage pipes (278).
“We also found 221 roof-water pipes connected to the sewer, 36 rainwater tank overflows connected to the sewer and 13 wash-down bays draining to the sewer,” Executive Manager Infrastructure Services, Glen Babington, said.
“The majority of these defects (2,228) have so far been repaired and we thank our customers for their co-operation in taking the necessary corrective action.
“But there are still some customers who have not rectified the incorrect connections we have discovered.
“This places extra strain on the sewage network, particularly in instances of heavy wet weather. It also contributes to a greater risk of a sewage overflow into other streets, parks or residents’ properties in the neighbourhood.
“Many people do not realise the sewerage network and the stormwater network are two different systems. The aim is to keep stormwater out of sewage and vice versa.
“During unusual and significant wet weather, like the 400-plus millimetres of rainfall that fell over several days during Tropical Cyclone Marcia, large volumes of stormwater get into the sewerage network and are likely to overload it, as recognised by our regulated environmental requirements.
“The amount and severity of overflows can be reduced if these incorrect plumbing connections are fixed. We are working closely with our customers to do so.”
Mr Babington said smoke-testing was a much more cost-effective way to address stormwater infiltration than simply building bigger pipes, pumps and treatment plants.
“If we did that, we would be spending millions of dollars and increasing customer bills significantly,” Mr Babington said.
“Instead, we are focussed on reducing the infiltration of stormwater to avoid unnecessary, wasteful expenditure and impacts on customer bills.”
Unitywater has a Sewage Overflow Abatement Program which has been developed to reduce the amount of rainwater entering the sewerage network in order to:
- Reduce the inconvenience to customers caused by sewage overflows;
- Prevent sewage overflows into waterways, rivers, parks and private property;
- Defer the need for expensive upgrades to sewage infrastructure;
- Keep sewage pumping and treatment costs to a minimum; and
- Enhance the quality of our waterways.