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Sewage from a “cross-connection” polluting Owhiro Bay, contamination continues at Taranaki Wharf

News from Wellington Water
The water quality in Owhiro Bay is being affected by a cross-connection. A cross-connection is where a wastewater pipe is connected into a stormwater pipe. Most cross-connections are from private pipes into public (council) pipes, and this is the case here.

Wastewater from private properties is entering the stormwater system, which leads to Owhiro Stream, which leads to the Bay. We are working with the property owners concerned, who were not aware of the issue, to resolve it as quickly as possible.

Contamination from cross-connections can be difficult to locate. Wastewater flows are not constant – they depend on usage. To find the source we have to take samples, send them to the laboratory for testing, and then get the results. This takes a couple of days. We have to work our way methodically upstream to narrow down the area where the contamination is coming from.

We’re working with property owners to resolve cross-connections we’ve identified. We expect to have these sorted by the end of the week. We’re also continuing our investigation and testing; it can be a mistake to think the first fault you come across will fix the problem.

If you have concerns about what you think might be a cross-connection at your place, please let us know and we’ll come and take a look. Our main concern is to eliminate as many of these as we can.

Warning signs that recommend against swimming and fishing in Owhiro Bay remain in place, and will stay there until we receive three consecutive days of clear results. We will update via social media and the website when this changes. If you have been swimming in the area and feel sick, please visit your doctor.

Wellington.Scoop – January 20
The council-owned Wellington Water company is this week faced with its fourth sewage spill in less than a month.

The spill, reported yesterday by the DomPost, is at Owhiro Bay on Wellington’s south coast. Measurements taken daily since January 8 have shown unsafe pollution levels every day.

Tom Hunt of the DomPost reports:

Wellington Water became aware of the contamination spike at Owhiro Bay just before New Year’s Eve and put up signs but, with swimmers still using the water, it admits it could have communicated better. On one hand it has told residents it is fixing the problem – likely caused by wastewater including sewage getting into stormwater – on the other it says it is still trying to find out what the problem actually is.

There is no information about Owhiro Bay on the website of Wellington Water.

But pollution at the Bay has been unresolved for ten years – in 2010 the beach was closed for weeks when the city council failed to find the source of the contamination. In March of that year the council said it believed it had fixed the problem. But two years later contamination was again found in the bay.

Five days ago, Wellington Water reported a discharge of partially treated sewage from the Martinborough wastewater treatment plant. It has provided information on this contamination:

We estimate that about 90,000 litres – three rainwater tanks-worth – of partially treated wastewater entered the Ruamahanga River over a 12 hour period between 9.45pm last night and 10am this morning. This is about two litres a second, or a dilution factor in the river of about 10,000 to one. Public health and recreational water user risk from the discharge is understood to be negligible. Discharging treated wastewater to the river is a consented activity under the right conditions, but in this case, the discharge was not in accordance with the consent. Another 45,000 litres of partially treated wastewater was discharged to land adjacent to the treatment plant, where treated wastewater is normally spread by irrigation.

Authorities at Regional Public Health and Greater Wellington Regional Council as well as iwi and community liaison group representatives have been notified. We have initiated a full incident response and investigation and the outcomes of this work will be released when completed.

Meanwhile, sewage contamination in part of Wellington harbour has still not been fixed. On 10 January, Wellington Water reported:

We have been working this week on Cuba Street to resolve a cross-connection to reduce the contamination in the inner Wellington Harbour. Recent tests show that the water quality has still not improved sufficiently, so we continue to advise people to avoid swimming or collecting seafood at the Taranaki Diving Platform and the shaded area on the map below until further notice.

And work continues to provide new sewage pipes under the CBD, after the December collapse which resulted in millions of litres of sewage flowing into the harbour.

Last year Wellington Water was convicted and fined $67,500 for an illegal discharge of sewage sludge from the Porirua City Wastewater Treatment Plant.

1 comment:

  1. jamie, 20. January 2020, 11:37

    Starting to be a bit of a habit and the excuse of old pipes or getting to know how the system works is wearing thin.