Ōwhiro Bay water quality

We won’t be updating this page while we work through how we present information about water quality monitoring for the Wellington region.

Update 29 October 2020

Alongside the Ōwhiro Bay Community we’ve developed the second edition of WorkStream, our regular report that captures the activity and sampling results in Ōwhiro Bay.

Take a look at WorkStream Issue 2.

All data below is from a Sanitary Survey and remedial work undertaken by Wellington Water from December 2019-September 2020. The survey was carried out following the discovery of E-coli on Ōwhiro Bay beach, December 2019.

Update 17 September 2020

Commentary on results  (recent trends, weather events, other influencing factors):

The results for August are varied with a number of spikes showing in the monthly figures. However, the spikes coincide with rainfall as recorded by Berhampore Nursery rain gauge (the closest GWRC rain gauge to Ōwhiro Bay).
The results are indicating the following issues:

• We are seeing significant wet weather spikes at the Above T&T Landfill sampling site. This site is above the Ōwhiro Bay residential areas, as well as above the industrial area. The fact that the spikes are appearing only due wet weather events implies that there is possibly an unidentified constructed overflow somewhere in the Brooklyn catchment.
• The U/S Ōwhiro Bay Parade Bridge dry weather site results are consistently higher than the results from sites above the Ōwhiro Bay School. This is indicating that the contamination source is coming from somewhere between the school and that Ōwhiro Bay Parade Bridge.

Update 12 August 2020

Alongside the Ōwhiro Bay Community we’ve developed WorkStream, a regular report that captures the activity and sampling results in Ōwhiro Bay.

Take a look at WorkStream Issue 1.

Update 20 July 2020

Latest sampling results:

Commentary on results (recent trends, weather events, other influencing factors):

Similar to the previous weeks, we had significant rainfall this week that has increased flow through the stormwater networks and influenced the water quality results. This effect can be seen in the spikes from 7-10 July

Unfortunately our sampler was unable to sample from the Owhiro Bay Beach site due to heavy swells that made entering the water to take the sample a Health and Safety risk.

The stream mouth and the beach site haven’t been included in the graph as coastal sites are measured using a different indicator organism that the freshwater sites

Remedial works in catchment

We have completed investigations into the Priority Three zone without finding any issues. Crews have returned to properties in the Priority Two zone that they could not access earlier and found a property with a broken wastewater lateral. Flow from this was entering the stormwater network, and this has been brought to the property owner’s attention with a request that it be addressed soonest.

The crews also dye tested the public wastewater pipeline to see if there were any leakages from the wastewater system into the stream. Nothing untoward was found here.

Our Operations teams are now implementing daily sampling for one week to determine what effect peak usage is having on the stream. Samples will be taken from seven locations (as seen below) at 8am each morning. These locations were chosen as the properties along this stretch of the stream are not connected to the stormwater network.

Dye testing the remaining residential properties on Happy Valley Road continues.

Public advice:

The mouth of Owhiro Stream is situated along Owhiro Bay beach, with the freshwater flowing across the beach and into the ocean. The stream has a history of contamination and it is advisable to avoid contact with this freshwater discharge. Warning signs have been fixed around the Owhiro Bay bridge reflecting this advice.

During winter it is also advised that heavy rain flushes contaminants from urban and rural land into waterways and that people not swim for 2 – 3 days after heavy or prolonged rain – even at sites that generally have good water quality

Next scheduled sampling dates:

Daily until further notice.

Monthly ecological sampling was carried out in the stream behind 17 Happy Valley Road as per the monitoring programme. We were also asked by community representatives to carry out sampling in the stream behind the Owhiro school. The results for both sites will be sent through to community representatives this week.

Sample site locations

Owhiro Bay Beach site and Owhiro Stream u/s Owhiro Bay Parade

Lower Careys Gully and the two Happy Valley Tip Bridge sites

Kingston and Owhiro Stream above T&T Landfill

Investigation Priority Areas

Update 27 June 2020

Latest sampling results

Commentary on results

On the 13^th, we recommenced daily sampling at eight sites along the Owhiro Stream, as well as on the beach. This coincides with the increased investigation activity from our Operations team and their contractors.

The results indicate that there is some contamination influence between the Owhiro Stream sample site above the T&T landfill (see attached images showing sampling sites) and the stream site upstream of the Owhiro Bay Parade Bridge.

The higher results for the 13^th and the period 17^th – 21st reflect rainfall over those days. Significantly, the results do indicate that the contamination is largely concentrated at the lower reach of the Owhiro Stream. However the contamination during dry weather flow doesn’t appear to be affecting the recreation water quality at the beach sample site.

A summary line graph of the daily testing results at the stream monitoring sites is below. The stream mouth and the beach site are not included in the graph as these sites are measured using a different indicator organism than the stream sites.

Remedial works in catchment

As indicated in last week’s update, our Operations team continued their investigations in the Ōwhiro Stream catchment. We’re prioritising areas where stream water quality results indicate issues, mainly around the lower reach of the stream. Below is an image showing the areas we have prioritised. Gaps in the prioritised areas reflect properties not serviced by the stormwater network, where individual properties discharge their drainage straight into the stream.

The investigation consists of dye testing the gully traps on all properties where we have been allowed access, to see if dye makes its way from a property’s wastewater system into the stormwater system. If we do see dye in our stormwater network, then this would indicate some form of plumbing issue that could be contributing to the stream contamination.

The inclement weather over the past week has unfortunately slowed the progress of this work, meaning crews are still dye testing in the Priority Two area.  However a positive result is that they have located a broken sewer lateral that is overflowing into the stormwater network. Crews will be investigating this breakage this week and we will report the outcome in next week’s update.

An issue that is slowing the crews down and impacting our investigation is there are some properties where we have not been able to gain permission to access.

Public advice

The mouth of Ōwhiro Stream is situated along Ōwhiro Bay beach, with the freshwater flowing across the beach and into the ocean. The stream has a history of contamination and it is advisable to avoid contact with this freshwater discharge. Warning signs have been fixed around the Ōwhiro Bay bridge reflecting this advice.

During winter it is also advised that heavy rain flushes contaminants from urban and rural land into waterways and that people not swim for 2 – 3 days after heavy or prolonged rain – even at sites that generally have good water quality.

Next scheduled sampling dates

Daily until further notice.

During the week, ecological sampling was carried at in the stream behind 17 Happy Valley Road as per the monitoring programme. Wellington Water was also requested by community representatives  to carry out this sampling in the stream behind the Ōwhiro school. The results for both sites will be made available to the community once their laboratory have completed the reports.

Update 21 June 2020

Latest sampling results:

Commentary on results

On 13 June we recommenced daily sampling at eight sites along the Ōwhiro Stream, as well as on the beach. This coincides with the increased investigation activity from our Operations team and contractors.

The results indicate that there is some contamination influence between the Ōwhiro Stream sample site above the T&T landfill (see images below showing sampling sites) and the stream site upstream of the Ōwhiro Bay Parade Bridge.

However, it appears the contamination is not affecting water quality at the recreational bathing sample sites in the bay.

The higher results for 13 and 17 June reflect the effect of rainfall over those days. A summary line graph of the latest daily testing results is below, illustrating that rainfall effect clearly.

Public advice

The mouth of Ōwhiro Stream is situated along Ōwhiro Bay beach, with the freshwater flowing across the beach and into the ocean. The stream has a history of contamination and it is advisable to avoid contact with this freshwater discharge. Warning signs are fixed around the Ōwhiro Bay bridge reflecting this advice.

Public health advice is that because rain flushes contaminants from urban and rural land into waterways, people should not swim for 2 – 3 days after heavy or prolonged rain – even at sites that generally have good water quality.

Remedial works in catchment

Our Operations team re-started investigations in the Ōwhiro Stream catchment last week. We’re prioritising areas where stream water quality results indicate issues, mainly around the lower reach of the stream. Below is an image showing the areas we have prioritised. Gaps in the prioritised areas reflect properties not serviced by the stormwater network, where individual properties discharge their drainage straight into the stream.

The investigation consists of dye testing the gully traps on all properties where we have been allowed access, to see if dye makes its way from a property’s wastewater system into the stormwater system. If we do see dye in our stormwater network, then this would indicate some form of plumbing issue that could be contributing to the stream contamination.

As of Friday, our teams had successfully dye tested the Priority 1 area and almost completed the Priority 2 area. Next week we will finish the Priority 2 area and start the Priority 3 area, weather permitting. To date we have found no plumbing faults at the properties we have tested, however there are some properties in the areas that we have not had access to.

Other activity

On Friday, staff from Wellington Water met with technical representatives from the Ōwhiro Bay community, to talk over the current sampling and investigation programmes, the resource consent that Wellington Water operates under, and the opportunity to co-develop an Ōwhiro Stream Catchment Management Plan. Also discussed was how best to make monitoring data and catchment activities more available to the community, with the view to possibly rolling this approach out across the region. The meeting was positive with Wellington Water taking away a couple of tasks to work on and report back.

Next scheduled sampling dates

Daily until further notice. Also next week there will be ecological sampling in the stream behind 17 Happy Valley Road and behind the Ōwhiro School.

Update 14 June 2020

Commentary on results

No new results were recorded this week as sampling frequency has been fortnightly under Covid levels 4, 3, and two. However, under level 1, daily sampling resumed on Thursday.

Remedial works in catchment

As agreed with OBRA, in a recent meeting, WWL drainage crews recommenced their investigations, targeting the bottom 1.8km reach of the stream on Thursday. The results of these investigations will be included in these weekly updates

Other workstreams

Discussions have been held with Greater Wellington Regional Council about the current sampling data being included, and made visible, on their Open Data website. This will allow the stream quality data to be compared with GWRC’s rainfall data and the stream flow data at the Ōwhiro Bay Bridge. The site will also display trends and allow for the downloading of the data itself.

Public advice

The mouth of Ōwhiro Stream is situated along Ōwhiro Bay beach, with the freshwater flowing across the beach and into the ocean. The stream has a history of contamination and it is advisable to avoid contact with this freshwater discharge. Warning signs have been fixed around the Ōwhiro Bay Parade Bridge reflecting this advice.

During winter we also advise that as heavy rain flushes contaminants from urban and rural land into waterways, it is recommended that people not swim for 2 – 3 days after heavy or prolonged rain – even at sites that generally have good water quality

Next scheduled sampling dates

Next week

Update 6 June 2020

Wellington Water monitors environmental water quality on behalf of client Councils, to detect acute contamination spikes which may indicate problems within the network. This update is to inform the community of the latest results and current activity in the area, and is a snapshot overview.

All samples are gathered and analysed by an independent specialist laboratory.

Latest sampling results:

Commentary on results

The results indicate that there is some contamination influence between the Ōwhiro Stream sample site above the T&T landfill (which is at the top of the catchment) and the stream site upstream of the Ōwhiro Bay Parade Bridge. However, it doesn’t appear that the contamination is affecting the recreational water quality at the beach sample site. 

Remedial works in catchment

As agreed with Ōwhiro Bay Residents Association in a recent online meeting, starting next week Wellington Water drainage crews will recommence their investigations, targeting the bottom 1.8km reach of the stream.

Public advice:

The mouth of Ōwhiro Stream is situated along Ōwhiro Bay beach, with the freshwater flowing across the beach and into the ocean. The stream has a history of contamination and it is therefore advisable to avoid contact with this freshwater discharge. Warning signs have been fixed around the Ōwhiro Bay bridge to reflect this advice.

Residents are also reminded that heavy rain (as common at this time of year) flushes contaminants from urban and rural land into waterways and that people are advised not to swim for 2 – 3 days after heavy or prolonged rain – even at sites that generally have good water quality.

Next scheduled sampling dates:

Next week

Sample site locations:

Ōwhiro Bay Beach site and Ōwhiro Stream u/s Ōwhiro Bay Parade

Ōwhiro Stream above T&T Landfill

Update 29 May 2020

Wellington Water monitors environmental water quality to detect contamination which may indicate problems within the network. This update is to inform the community of latest result and current activity in the area.

All samples are gathered and analysed by an independent specialist laboratory.

Latest sampling results

Update 8 May 2020

During the response to COVID-19 with many activities on hold/paused at alert level four, it was requested that we undertake sampling in Ōwhiro Stream to see what impact this paused activity had on the stream. We continued this through the transition to alert level three.

For reference, the sampling site ‘Owhiro Stream above T&T Landfill’ is located above most of the commercial activities, whereas the sampling site ‘Ōwhiro Stream at Happy Valley Tip Bridge’ is at the intersection of Rarangi Road and Happy Valley Road – which is below most of the commercial activities centred around Landfill Road. At these sites, the sampling results were below the consent pollution response triggers.

At the sampling site, ‘Ōwhiro Stream behind 17 Happy Valley Road’ is a freshwater monitoring site that is just upstream of the Ōwhiro Bay Parade bridge. It was chosen as it has less tidal influence than the Parade Bridge site. The results show that on most days, the pollution levels here were higher that the sites around the commercial activities. The results were higher than consent triggers in three occasions. This would indicate that the pollution is likely coming from a source(s) below the commercial/industrial activities. As with Alert Level 4, we are concentrating our resources on essential services and on keeping our frontline teams, who maintain them, safe and healthy. Our water quality monitoring and response activity continues to be scaled back during Alert Level 3.

The latest results show high levels on May 3 and 4, this is a result of heavy rainfall. As always, it is recommended that you don’t swim 48 hours following heavy rainfall.

Update 15 April 2020

The Baywatch site has been in green since January. The stream mouth quality has been improving since 27 March, which is likely due to the heavy rainfall we experienced a couple of weeks ago giving the whole stream and stormwater network a good flush. 

Update 6 April

Readings have trended down as the system flushes out after heavy rain in the last weekend of March.

Update 3 April 2020

Readings are typically higher following rain because it washes contaminants into the stormwater system and stirs up pollutants already stuck in pipes. The high results here are a result of the heavy rain we had last weekend.

You may have noticed a difference in some of the sampling results, with results higher than 10,000 showing as >10,000. This is because we moved to a test with a more rapid turnaround in order to provide results within a shorter timeframe for the Ōwhiro Bay community. This test provides precise results up to 10,000. Precision above that level requires the longer turnaround form of testing.

In the context of the national response to Covid-19, our top priority is providing clean drinking water and safe wastewater treatment to our community. This means our water quality monitoring and response activity is being temporarily scaled back. Read more about our response here.

What the lock down means for sampling in Ōwhiro Bay is that we are essentially reverting to our regular sampling programme from Monday 6 April. This means:

• Sample testing at the recreational bathing Baywatch site in Ōwhiro Bay will be fortnightly from April 1 with the end of the bathing season
• Because we are suspending work on private cross-connections during the lock down, we will suspend associated sanitary survey sampling in the stream
• Samples from the bottom of the stream will be taken fortnightly rather than daily
• The other sites in the stream will be sampled monthly rather than daily
• We’ll change our sample test from the quick-turnaround test accurate up to 10,000 cfu/100ml back to the longer format test that captures spikes into the millions, should they occur. These samples take an extra day or so to process but will allow us to better detect blockages causing wastewater overflows that require urgent attention.

Update 30 March 2020

Results have been affected by rain and therefore inconclusive with regards to helping narrow down the source of the pollution.

Update 27 March 2020

Rain on Tuesday will have contributed to the high values we’re seeing.  However, levels at the stream mouth and the Parade Bridge are still a concern. Rarangi Way culvert has not been out of spec since the cross-connections were fixed on 11 March, so we are investigating the lower section of the stream.

Update 24 March 2020

High results for the stream outlet were likely due to rain on the night of the 21^st. We have started sampling from the bottom of the stream moving up to find a possible source nearer the bridge.

Update 20 March 2020

Rarangi Way culvert results are trending down, indicating that the work that Wellington Water drainage teams have undertaken in that area is having a positive effect on water quality. However we are seeing some higher results at the stream mouth and Parade Bridge. This suggests a possible issue in the lower reaches of the stream closer to the bridge, which our teams are investigating. Notably, the sampling sites in the bay itself continue to show good results, indicating that the issue at the stream mouth is not extending beyond the bay into the Marine Reserve.

Update 19 March 2020

The latest sampling indicates the stream mouth is back at unsafe levels, as well as the Baywatch site at an amber level. These results may have been influenced by the stormy weather that came through the night ahead of this sampling. We are continuing with investigations in Ōwhiro Bay to locate further contamination points.

We will look at the next samples as they come through, which will give us a better indication of what’s happening in the catchment.

Update 18 March 2020

Readings are a valuable measure for establishing faults and trends, but because they are a small sample taken at one moment in time they do not indicate the state of the entire waterway all of the time.

Readings will vary for several reasons. Wastewater flows are intermittent in nature, depending on how the community is using water at the time – for bathing, cleaning, laundry, using the toilet and cooking. Peak use time is between 7am and 9am, so a reading taken during that period might result in a spike. Sea conditions affect readings, and readings will always be higher after rain because it washes contaminants into the stormwater system and stirs up pollutants already stuck in it. For this reason, swimming at urban beaches should always be avoided 48 hours after rain.

Sample readings are presented on a logarithmic scale because there are exponential changes in the magnitude of numbers.

A swimming beach reading of 280cfu/100m leads to the beach’s closure and an investigation to stop the pollution source. (Cfu stands for colony-forming units, in this case the microorganisms being measured are live bacteria found in bird, human and other mammal faeces.)

Most urban streams are not swimmable and processes around readings are different. Current monitoring is based on a rolling 12-month median value for E.coli (dry weather sample) > 1000 cfu/100ml, which triggers investigation on the ground, as well as a single reading above 10,000 cfu/100ml/
A stream reading above 1000 cfu/100ml requires that a second reading be taken the next day. We are migrating towards Greater Wellington Regional Council’s Global Stormwater Consent condition of two consecutive samples of >1000 cfu/100ml, triggering investigation on the ground. This will be closed out as part of 21/31 LTP discussions.

To put those sample numbers in context, a single reading of over 20,000 cfu/100ml is not unusual for urban waterways in Wellington or across New Zealand, particularly after rain. The top end of the scale is raw sewage, which reads in the millions. 

Update 11 March 2020 - recent sampling results

The sampling results published on 9 March indicated a spike in results on 1 March of 23,000cfu/100ml.

While this spike understandably caused concern in the community, we think some more context will help to address this. These figures are not uncommon across the Wellington region and across New Zealand after rain. Rain will wash pollutants into the stormwater system and will stir up pollutants that accumulate in the stormwater system over the very dry summer. This is why our advice is always to avoid swimming at our beaches following 48 hours of heavy rain.

We will be discussing these results and related matters at the Community Board meeting on Monday 16 March.

We are really grateful to the community for their interest in this work, and we’ll be providing more context for this and the test results in the future on our website: wellingtonwater.co.nz/owhiro-bay

Update 11 March 2020 - stormwater flushing

We’re flushing out stormwater pipes in the Ōwhiro Bay catchment today. This is to help clean out pipes that have been affected by the plumbing faults (cross-connections) that we’ve found and fixed.

We believe there is more work to do, so we will be continuing with our investigations in the catchment.

One of the ways we investigate is through dye testing. Dye is put down the gully trap (plumbing feature that receives wastewater from the property) of a property, and if the dye comes out in the stormwater network, we know there is a plumbing fault. Dye testing will be continuing over the next few weeks.

Update 9 March 2020

Update 2 March 2020

Update 27 February 2020

Update 21 February 2020

Update 19 February 2020

We are currently undertaking water quality sampling in Ōwhiro Bay; daily at the stream mouth, and weekly at the Baywatch site (on the other side of the bay).

Below are the latest results.

Update 4 February 2020

We have followed our protocols recommending the reopening of the beach. A source of the spike in contamination was identified and the sampling at the long term beach monitoring site had returned to normal. We acknowledge that our communication could have been better as removing the warning signs implies that the Ōwhiro Stream, that crosses the beach, is safe for swimming in. Ōwhiro Stream, like many urban waterways, has a long history of contamination and is regularly unsafe for swimming in. Improving the quality of Ōwhiro Stream will require a coordinated and long term programme of works.

Update 30 January 2020

The beach has returned to safe levels and our investigations of the likely sources in the catchment has just been completed with 3 cross-connections found. We will be removing the warning signs today.

Thanks to the wider community for your patience and understanding as we worked through resolving these cross-connections.

Update 29 January 2020

Our operations team have been hard at work resolving cross-connections in the network. As a result of this work, we are seeing an improvement in the water quality in Ōwhiro Bay.

We are continuing with our routine sampling, and are looking at when it is appropriate to take down the warning signs. For now, they are still in place. We will confirm when signage comes down.

What's happening?

The water quality in Ōwhiro 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 Ōwhiro 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 Ōwhiro 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.