Tests expose sewer faults

Whangarei District Council efforts to stop sewage flowing into Whangarei Harbour have exposed some unusual potential leaks.
The multiple woes of Whangarei's ageing sewerage system are being uncovered with a survey hunting for possible leaks seeing smoke pumped into pipes emerge in residential gardens, Whangarei Harbour and even the Whangarei Aquatic Centre.
Sewage flowing into Whangarei Harbour has been an major issue in the past few years with wastewater infiltrating the sewerage system from private properties a big part of the problem.
Whangarei District Council is smoke testing gully traps and sewers around the city to find out the full extent of the problem so it can deal with it.
Council wastes and drainage manager Gary Oldcorn said the testing had exposed a number of problems, including smoke emerging from a sewerline into mangroves in Riverside.
"The aim of the programme is to prevent stormwater getting into the sewer during wet weather and causing storm-related sewage spills which have been a major public health concern for the community," he said. "We knew there must be a substantial storm water infiltration in this catchment because the sewage pumping station at Riverside always has large increases in volumes during heavy rain compared to the normal day-to-day flow."
Mr Oldcorn is pleased the programme is highlighting the issues so it can know the full extent of the problem and emphasised there are no health-and-safety issues at the aquatic centre. The sewers have been developing for up to 80 years in older areas, so some pipes have had much more time for things to go wrong.
"The inspection and testing programme is showing very clearly how widespread and complex the problem is with stormwater getting into the sewer system and how simple the fixes can sometimes be," he said.
"It illustrates how much of the problem can be solved by individual property owners ensuring their downpipes are correctly plumbed to the stormwater system, not the sewer system."
In the case of the smoke in the mangroves, the testing showed there was no back-flow prevention valve on the emergency overflow pipe from the council's Riverside pumping station.
"That meant sea water could potentially flush into the sewer on very high tides, and we will now fix that," Mr Oldcorn said.
During the testing, smoke also started filling the basement of the Whangarei Aquatic Centre, in Ewing Rd. "That could indicate the potential for water in the basement to get into the sewer system. We aren't sure why the smoke has shown, but we can now investigate and remedy if there are any problems." 
He said at no point had storm water or sewage entered the basement at the complex and the problem might be caused by something as simple as an S-bend drying up.
"We have investigated only 10 per cent of the (730) properties in the catchment so far and have already found three houses where either part or all of the roof water was discharging into the sewer," Mr Oldcorn said.
"Seemingly small spot problems like these can cause major issues. We will be working with the owners of these properties and giving them all the advice we can to fix their faulty connections."
The smoke testing will continue until the end of November before moving on to Hikurangi.