Mist used to test Portland sewers

22 June 2018

Wannon Water will begin a mist testing program in Portland next week to help protect the future reliability of the town’s sewerage system.

Wannon Water senior planning and development engineer Vin O’Neill said contractors would pump a mist into sewer manholes and then monitor where it escapes to identify where stormwater may be entering and putting strain on the system.

The two-week testing program will take place in areas where large volumes of stormwater have been recorded at sewage pumping stations. Testing will begin mid next week in streets and properties in the area north of the central business district.

“Currently, the sewage flows that enter the Portland Sewage Treatment Plant from these areas during heavy rain are three times higher than in dry weather, which suggests that stormwater is getting in through leaks, faults or illegal connections,” Mr O’Neill said.

“The sewerage network is not designed to accommodate stormwater flows. Excess water can overload the sewers and cause spills, so it is important that we find out where it is entering the system.

“The mist testing is an effective and cost-efficient method of finding sources of stormwater intrusion, cross connections between sewers and stormwater drains, and defective sewer connections.

“Once we have a clearer picture of where the stormwater is entering the sewers we can then take action to address any concerns.”

The mist is clean and odourless. Under pressure, it fills the sewer mains and any sewerage pipes connected to it, and may briefly be seen coming out from building roof vents, foundations, manhole covers or the ground.

The mist should not appear inside homes unless there is faulty plumbing. If it permeates up through the ground, it indicates breaks in the sewer line.

“If the tests identify any defects or unauthorised connections on customer properties, Wannon Water will notify those customers in writing and work with them to rectify the issue,” Mr O’Neill said.

The program will not cause any disruption to sewerage services.