Heathcote River - a disaster area
Pollutants in the Heathcote River include human faeces, heavy metals and industrial waste.
It was bad before the Canterbury earthquakes and worse now.
University of Canterbury Strategic Water Management Professor Bryan Jenkins this week told The Press water quality tests in the Heathcote were damning.
It was far from safe for recreational use and would need a major clean up if it is to be used for boating like businessman Alistair Cassell wants.
The river has many problems, with raw sewage top of the list.
The Christchurch wastewater system was rigged to overflow into rivers when the system was under pressure. This often happened during heavy rain. Pumping sewage and wastewater into rivers relieved system stress but meant regular dumps of raw sewage.
Pre-quake, Jenkins said 22 Christchurch sites did not meet national sewage guidelines, overflowing more than once every two years.
Sewage went into the Heathcote on 36 separate occasions last year.
"Pre-quake it was totally unacceptable. Post-quake, it is worse."
There were 114 constructed overflow points in the Christchurch wastewater network.
Some sites were particularly problematic for the Heathcote, including one on Fisher Ave in Beckenham that overflowed an average of five times a year between 2003 and 2008.
After the February 2011 earthquake, E.coli levels at an Opawa Rd river testing site were 35 times higher than the pre-quake average and 20 times higher than Ministry for the Environment guidelines.
Water tests this year showed the quality was "very poor", Jenkins said. "Basically it's the worst ranking you get. They're [ECan] saying, ‘Do not swim here.'
"You can see why they're saying not to eat the whitebait in our rivers."
On top of E.coli, the Heathcote suffered from industrial pollution.
Directly downstream from industry in Middleton and Wigram, pollution indicators were high before the earthquake. Jenkins said industrial pollution fed into Hayton's Drain, which ran into the upper Heathcote.
Since 2005, ECan had caught and prosecuted or fined 19 businesses for industrial pollution offences. Damages, fines and remedial payments totalled almost $100,000. Pollutions included diesel, detergents, concrete waste, cleaning chemicals, blood and paintwash.
ECan resource management director Kim Drummond said there was "a huge amount of work going on" to improve the river and no business had consent to discharge pollution into the waterway.
Along with man-made pollutants like sewage and industry, Jenkins said the Heathcote was battling environmental factors.
Rivers running through Christchurch, including the Avon, the Styx and the Heathcote, were supplied by groundwater and streams.
While groundwater quality was high near the Waimakariri River, by the time it reached the Heathcote, it was heavily contaminated.
Jenkins said Nitrate-Nitrogen, a pollution indicator, was extremely high in groundwater feeding into the Heathcote, and was partly the result of Canterbury's natural soil conditions and water quality from feeder streams.
Post-quake academic studies showed high sediment and liquefaction levels having an "extreme" effect on the species living in the river. The Heathcote was home to eels, inanga, trout, mullet and bully.
So what can be done?
Despite the condition of the Heathcote River, Jenkins says it is not too late to save it. "One thing that's important for people to know is that the rivers can bounce back. If we do make restorative efforts, they'll recover."
Time is of the essence. As conditions stay stable but poor, work could be done to improve the river and solve some of the worst issues. "This is not rocket science."
Jenkins said the Avon River Precinct in the central city was a great example of what could be done - riparian planting and sediment and liquefaction removal.
However, fixing rivers one stage at a time would be pointless if other stages were not fixed. Work on one area would be undone when sediment and pollution washed in from others.
The sewage problem would be solved with a modern system - one that diverted sewage into holding tanks in times of flooding pressure, rather than sending it into rivers. The tanks could be emptied back into the system for proper treatment when pressure on the system died down.
Residential stormwater technology had been updated in the last 10 years. Jenkins said subdivisions built in the last decade often used a swale system instead of the conventional curb-and-channel gutter system.
Drummond said sediment problems from the Port Hills was being looked at.
"An action plan is expected within six months or so.
"The solutions are a work in progress and involve a wide range of people, organisations, businesses and councils, including the community water management zone committee."
Any cleanup would be funded by the city council and ECan.
Jenkins would like to see better enforcement and regulation for industry.
"There is no doubt that improving industry - direct discharges and stormwater management - would help," he said. "Spills and industrial accidents are preventable with better systems in place."
The problems E.coli levels 20 times higher than Ministry for the Environment guidelines. 36 sewage overflows into the river in 2013 alone. Industrial pollution. High phosphorus, nitrogen and sediment levels. The solutions Sewage overflow tanks. Enforced protection of groundwater quality. Better stormwater systems. Managed wetlands to improve water quality.