DrainWise is hailed a success by mayor: Work to reduce sewage overflows making progress

A scheme to stop sewage from bubbling up on to Gisborne properties during severe weather events has been hailed a success by the city’s mayor. 

Gisborne Mayor Rehette Stoltz said as a result of DrainWise, the network capacity had increased from four to six times dry-weather wastewater flows during wet weather events. 

The DrainWise programme aims to prevent sewage from backing up on to Gisborne properties by renewing wastewater pipes and collaborating with private property owners to minimise the inflow of rainwater into the wastewater system. 

When a rainy spell still brings a risk of contaminated water reaching properties, the council opens valves and discharges wastewater into the city rivers. 

In a recent letter to the editor of the Gisborne Herald, one resident said the approach of trying to prevent stormwater getting into the wastewater system may be the wrong tactic. 

“The necessary investment in a system update will only happen if Gisborne District Council makes it happen,” said the resident. 

“After many fruitless years of trying to prevent rainwater from getting into the system, it may be time to grasp the nettle and ensure the system is capable of taking it away — rather than backing up and necessitating the opening of sluice valves,” they added. 

But Stoltz is adamant the programme is working, especially where it addresses the impact of localised flooding topping wastewater gully traps. 

The private property inspections help to identify and address gully trap and downpipe issues, she said. 

“To date, the private property inspections have resulted in 2600-plus gully trap repairs, and the removal of 98 roof downpipes from wastewater gully traps. 

“In simple terms, during a rain event, 98 downpipes are equivalent to 4900 properties worth of dry-weather wastewater flows, so removing these has a substantial impact on network performance,” said Stoltz. 

The council property inspections team will be working through Kaitī for their 2024/25 programme, an area which is historically known for overflows. 

“DrainWise is a critical focus for our three-year recovery plan, with $13.2m allocated to continue to improve the performance and capacity of our wastewater network and reduce stormwater inflow and infiltration,” said Stoltz. 

The resident’s letter also made the case that Gisborne District Council should prepare for major works on the city’s wastewater system, funded via the Local Government Funding Agency which was expected to be established by mid-2025. 

Stoltz said the Government had announced funding options as part of its Local Water Done Well initiative, which currently had its second bill working through Parliament. 

Council staff were working on the requirements to provide information to the council and community to make an informed decision on the future of Three Waters (stormwater, water supply, wastewater) in Tairāwhiti by June 2025, said Stoltz.