File photo. Wastewater overflows at a Cockburn St property in 2018. The issue has been ongoing for many years. Photo: LDR / Supplied
Plumbing and drainage mistakes are "key contributors" to sewage flowing into backyards in Masterton during bad weather, the council says.
Properties in the Cockburn St area have been flooded with wastewater during storms, leaving toilet paper and human waste floating in some people's yards and forcing residents to use portaloos because their toilets don't work.
A temporary medium-term solution for residents is now in place while a longer-term project is underway.
This involves Masterton District Council [MDC] confirming the sources of wastewater overflows and identifying the long-term solution and investment needed in the stormwater and wastewater network.
MDC infrastructure and assets manager Maseina Koneferenisi told councillors at a recent Infrastructure and Services meeting that "solid evidence" confirmed there are several cross-connections into the wastewater network.
"These are key contributors to overflow issues."
A report to elected members said the council has been able to "get visibility of some but there is likely a number that are beneath the ground - this will require physical work to confirm and remedy".
Cross-connections are a common mistake with residential plumbing and drainage works.
In this case, stormwater pipes have been connected to the wastewater system.
A common source of cross-connections is downpipes diverted into the gully trap - a small drainage vent usually covered with a small grating and located against the outside go a house neat the kitchen, laundry, or bathroom.
Wastewater and stormwater networks are separate and it is the property owners' responsibility to ensure they stay that way.
Local Democracy Reporting asked MDC if property owners would need to pay to fix these connections or if council would use ratepayer money to solve the problem.
An MDC spokesperson said the council would be taking "a collaborative approach" with the property owners, with each case considered on its merits.
Smoke testing has been underway to understand where inflow and infiltration may be happening and a "pilot trial" will soon begin in the area of Cockburn St, Taranaki St, Okato and Patea Place, and Kuripuni St.
The trial would involve more detailed data collection using instruments and potentially a hydraulic model.
"This will help us identify the potential areas of concerns, zones of inefficiencies, and how the network behaves under a variety of scenarios and weather events," the report to council stated.
Koneferenisi said council would then look at the numbers and solutions, then consider it as part of the annual planning process.
"It will have to be a long-term project, I imagine, considering the potential costs related to that."
An information evening would be held on June 12 for impacted residents where a report from engineering company GHD would be shared.
This report is an independent review and was commissioned in October by MDC chief executive Kym Fell.
Councillor Tim Nelson said he was pleased with the strategy and said communication with impacted residents was "incredibly important".
"If they feel they are being listened to, they are going to feel like we're actually taking their concerns into account as opposed to fobbing them off which I believe has happened in the past," he said.
"This report here isn't fobbing someone off, it's actually addressing the issue that has been happening for many years."
Masterton Mayor Gary Caffell disagreed with Nelson's use of the words "fobbing off".
"I think certainly there could be an improvement in the communication for sure," Caffell said.
"I'm not sure we would deliberately fob them off at any stage but I think that we need to do better."
LDR is local body journalism co-funded by RNZ and NZ On Air.