Stormwater Compliance Issues in Sanson and Rongotea

The stormwater and wastewater systems operate with distinct networks of pipes and pumps, each requiring different treatment processes. Wastewater necessitates a more intensive treatment than clean stormwater. However, when stormwater infiltrates the wastewater network, it leads to operational challenges and incurs unnecessary treatment costs. In severe cases, the increased water volume can result in wastewater discharges from manholes and pump stations, and, at worst, backflow into residential properties.

Stormwater can enter the wastewater system through damaged or inadequate plumbing.  This is known as inflow. Infiltration occurs when surface water seeps into broken wastewater pipes, often found on private properties.

Through operational monitoring, Sanson and Rongotea have been identified as key areas for intervention. The Council conducted a smoke testing program, where smoke was introduced into the network via manholes. Observers monitored for any escaping smoke from drains, helping to pinpoint problem areas.

During this assessment, 115 properties were identified, with the primary concern being downpipes that discharge directly into wastewater gully traps and low-lying gully traps that allow surface stormwater to enter the system.

Affected property owners will receive a direct letter detailing the issues that need to be addressed, accompanied by photographs for clarity. According to Council bylaws, it is the property owner's responsibility to rectify these issues. However, Council is available to assist with any questions or concerns regarding the necessary fixes.

A reinspection is scheduled for early 2025 to ensure compliance with the required improvements.

For more information, please visit; Stormwater Compliance | Manawatū District Council (mdc.govt.nz).

For questions please contact Council through infrastructure@mdc.govt.nz with the subject line of ‘Stormwater Compliance Issues in Sanson & Rongotea’.