Council discusses options to improve stormwater system
Upgrading Gore’s stormwater system to cater for a one-in-five-year storm could cost $175million, the Gore District Council revealed last week.
The Gore stormwater master plan and level of service was discussed at the council’s operations committee meeting on Tuesday.
3 Waters asset manager Matt Bayliss said in a report the existing stormwater reticulation network had capacity issues which caused flooding of private properties and the road reserve during large rainfall events.
In addition, about 40% of Gore’s and 25% of Mataura’s wastewater network was combined with the stormwater system which meant it was conveyed in a single pipe, he said.
“Therefore during any flooding, the wet weather overflows are often contaminated with wastewater.”
The combined system also resulted in high flows through the council’s wastewater treatment plant affecting performance and/or resulting in raw wastewater overflows to the environment.
The plan revealed the majority of wastewater and stormwater separation could be achieved by upgrading the council’s 12 existing discharge points, but two new stormwater outfalls would be needed.
Several scenarios were presented to councillors.
If the council stayed with the existing piping, 252 properties could expect to be affected by flooding.
The councillors were in favour of the upgrade that would cater for a one-in-five-year storm event, which would mean 29 properties would be affected, which would cost $175million.
“It is anticipated this will take in the vicinity of 50 years to implement,” Mr Bayliss said.
Another option would address a one-in-two-year storm, which would affect 163 homes, and would cost $110million.
Upgrading for a one-in-10-year storm event scenario, which would affect only four properties, would cost $260million.
Mr Bayliss said irrespective of the preferred option, the financial cost was significant.
Council general manager of infrastructure Ramesh Sharma said spreading the work over 50 years was logical.
“This report is about setting us on a journey,” Mr Sharma said.
Gore Mayor Tracy Hicks said the focus was on dealing with stormwater in Gore and Mataura.
“It’s good to see we’re getting into this space now,” Mr Hicks said.
Councillors believed it was a lot of money but it would be spent over a long period of time.
Cr Doug Grant questioned why the council did not take out a loan and proceed with the project in the short-term as interest rates were extremely low.