When it rains it pours, straight into the Waikato River. But it's not just rainwater that makes its way into the waterway. Daniel Adams reports.
Sewage spilled into the Waikato River system 138 times last year through overflowing pump stations connected to the stormwater network, often as a result of heavy rainfall.
The overflows, which dwarfed the twice-a-year average of similar cities, are revealed in a report presented today outlining the city's significant sewerage challenges.
While it is improving, Hamilton's wastewater network remains a sieve compared with other urban areas, prompting one river advocate to slam the record as "shameful".
The report also discusses compliance risks at the city's sewage treatment plant, where external technical expertise has been called in to assess how best to address issues.
The council faces sentencing next month for a spill there that leaked 112 cubic metres of effluent into the river, and may yet cost hundreds of thousands of dollars in fines.
The report warns continuing consent noncompliance for discharge quality from the plant into the river may lead to more enforcement action by the regional council.
Meanwhile, a proposal to pump sewage from another 18,000 people into the city's straining sewerage system via a major new pipeline from Cambridge continues to be floated.
City waters manager Tim Harty said the city's sewerage network, which includes about 140 pumping stations, was starting to improve in benchmarking against other cities.
"Essentially every one of those pump stations has an overflow and in times of heavy rainfall or pump failure the level can reach that point and overflow," Mr Harty said.
They will end up defaulting to the stormwater system, and we're not hiding the fact, that's a concern and we're trying to get out there and do as much as we possibly can."
"Some cities do have pump stations with significant storage, we don't," he said.
Almost $20 million is built into new 10-year wastewater budgets to address the issues, with $4.3m for pump station investment to reduce overflows and $15.2m tagged for the treatment plant, funded by loans serviced with rates and developer contributions.
"We haven't had any issues in securing the funds to address it," Mr Harty said.
Former city council candidate and Green Party activist Mark Servian found the comparison startling and said piping Cambridge sewage to the city was "bizarre".
"I would give them some credit, we're finding out about this because they're reporting it, and their processes have turned it up. From that point of view it's good, but while this report describes the status quo, it doesn't explain how we came to be there.
"The figures for the overflows compared to Dunedin are shameful. Our house is not in order and Hamilton is not in a position to criticise anyone about the way they use the river, and that's a bad place for us to be as a city.
"You may be able to prove the scale of the overflows were a relatively small volume, but it demonstrates that it happens, and it's completely possible for it not to happen."
Mr Harty said the potential Cambridge sewage pipeline was still being investigated.
"That's certainly one of the options on the table, and the other is to upgrade the plant at Cambridge," Mr Harty said.
"It's prudent for both organisations to look at the best solutions for the communities involved.
"There's no point getting into the detail of 'what happens if it turns up', until we know for certain that it's going to turn up."
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