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A damaged pipe at the Rotorua Wastewater Treatment Plant will be replaced after last week’s overflow.
Rotorua Lakes Council said it was alerted to a treated wastewater overflow on the morning of November 19. It was stopped between 10pm and midnight that night.
Treated wastewater is usuallypumped to Whakarewarewa Forest, where it is sprayed onto land, but Wednesday’s overflow drained into Lake Rotorua via Sulphur Bay.
The council said initial water quality tests found slightly elevated E. coli levels in Puarenga Bay.
“This approach provides a more reliable and quicker solution than repairing the damaged section alone.”
Wednesday’s overflow drained into Lake Rotorua via Sulphur Bay. Photo / File
“The decision to replace the pipe follows an earlier concrete repair that proved ineffective, possibly because the damage extends further than initially thought.
The council said fluid around the pipe made it difficult to confirm the exact cause of the damage, so replacing the full length of pipe, estimated to be about 100m, was the best option to ensure long-term reliability.
“While the pipe is not sealed, any ongoing leakage is contained within a hole dug to access the damaged section.
“At current plant flows, any overflow from the damaged pipe will remain contained on site.”
The council said its wastewater contractor, Trility, had reduced levels in parts of the plant to create storage capacity if inflows increased.
“… Prolonged heavy rain could challenge this temporary measure."
General advice from Toi Te Ora – Public Health after any heavy rainfall was to avoid swimming for 48 hours, because of the risk of elevated E. coli levels.
The council’s general manager of infrastructure and assets, Stavros Michael, said last week the break was not caused by ongoing work on the wastewater treatment plant upgrades. An exact cause ywas et to be established.
Rotorua Wastewater Treatment Plant. Photo / Rotorua Lakes Council
The damaged pipe is “35 to 40 years old” but had an expected lifespan of about 90 years, with Michael saying it was “not due for replacement” for many years.
“This is a very rare occurrence, and our community can rest assured that ensuring our critical infrastructure is well maintained is a priority for our council.”
About $427 million of investment in Rotorua’s water services was outlined in the council’s 2024-34 Long-Term Plan, with $167.4m allocated to wastewater services including the maintenance, renewal and upgrade of infrastructure.
Councillors voted to establish a Recovered Water Working Group in July to assess alternatives to the forest irrigation system and recommend a new permanent discharge method by early 2027.
The council said it was too soon to assess the impact of the break on ongoing upgrades or the potential cost of repairs.
Investigations into the cause of the pipe break continued.
- Additional reporting by Mathew Nash at Local Democracy Reporting
