No sewage overflow into rivers

A109 Light Utility Helicopter flight with mayor Gisborne City from the air in November 2023.

Substantial rain over the last couple of days did not cause sewage to overflow into Gisborne's rivers.

Gisborne District Council senior wastewater operations engineer Phil Dodds said the 55 to 70 millimetres of rain across the city would have caused sewer overflows into Gisborne river's in previous years.

“This improvement is directly attributable to the work the DrainWise team has done over the last two years fixing 404 low and broken gully traps and removing 50 household roof downpipes that were going directly into the sewer,” he said.

“Stormwater improvements undertaken on private properties minimise or eliminate surface flooding, which ends up going down low and broken gully traps.

“The Wainui Road high flow emergency sewer pump station did not run but it did get very close at 7pm last night.

“The sewer system's total network flow was at least 30 percent lower relative to previous years.

“This is a good sign as it means less stormwater infiltration into the sewer network. We do also acknowledge that dry conditions in soils could also contribute to this.

“We have upgraded 17 of the most critical sewer pump stations with modern adaptive cutter pumps.

“This includes the Wainui and Childers road sewer pump stations where we have noted a twenty-fold improvement in the stations' ability not to block and fail at critical high-flow times.

“We have started the sewer lining process. The work up Lytton Road alone has had an immediate improvement to the wet weather flows from that western area of the town.

“We have installed additional level and flow electronic monitoring devices which greatly assist in identifying problematic issues. This helped to resolve the Turenne Street sewer problems.

Towels, fat and wet wipes are still a problem, Mr Dodds said.

“We have seen up to 450mm-diameter sewer mains being partially or fully blocked.

“The 3 P's (pee, poo, paper) is still a very important message but it's only part of the problem.”