In an earlier piece, I posed some questions about what might be in our local waterways. I wondered what might be getting sucked up the new Alexandra drinking water intake pipes beside Lake Dunstan near the Clyde Dam.
Water arriving at the Clyde Dam will start as pure snow melt from the Southern Alps, but on its way it has picked up all manner of hitchhikers.
Water leaving Lake Wakatipu looks good, although, as we know, it is not necessarily E. coli-free. Near the Shotover River mouth the Queenstown Lake District Council’s new Project Shotover wastewater plant has resource consent to discharge up to 45,000cu m of treated liquid waste per day “on to land” within a designated area of the Shotover River delta.
This staggering amount is equivalent to a rugby field filled daily almost 6.5m high with treated waste.
I suggest it then finds its way through the gravel and joins the Kawarau River on its way to Cromwell.
To be fair, the plant is modern; E coli levels discharged are supposed to be within “swimmable” limits, but how many toxic chemicals remain in that waste?
Why isn’t that liquid being disposed of away from the river system? Examination of old documents show that that was considered, but the full QLDC council meeting of December 2007 approved a cheaper option.
At Cromwell, the Central Otago District Council has consent to discharge 4400cu m of treated liquid septage per day in dry weather or 7500cu m on a wet day into the Kawarau arm of Lake Dunstan.
Until January 1, 2019, this septage could contain up to 200,000 colony forming units of E. coli per 100ml, a figure that could be doubled without breaching the consent conditions.
From January 1, 2019 until 2044, there is no specified upper limit on E. coli discharged, although a Ministry for the Environment formula does give guidelines based on sampling numbers. Present unsafe “swimmable water” levels are declared when there are more than 260 E. coli per 100ml in 50% of the samples taken.
At Clyde there is at present no communal sewage disposal and all liquid effluent filters down from septic tanks through the gravel to the water table.
At the confluence of the Manuherikia River with the Clutha/Mata-Au, the Manuherikia River may legally contribute between 80 and 350cu m per day of treated liquid effluent from Omakau, together with up to 10,000 E. Coli per 100ml.
Around the corner, another 2800cu m of treated waste from the Alexandra wastewater plant can legally join the flow every day.
There is also stormwater run-off carrying animal faeces, and toxic chemicals from our roads that add to this burden in our lakes and rivers.
So you get the picture! On January 20, 2019 the New Zealand Herald reported 48 Auckland beaches as unsuitable for swimming due to high E. coli levels.