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Pegasus Lake Update: PRGI Lake Sub-Committee & Lake Stakeholders Meeting

The Pegasus Residents’ Group (PRGI) has set up a Pegasus Lake Sub-Committee to engage with the lake stakeholders and provide transparency to Pegasus residents on the progress of the lake water quality issue. The first meeting took place this month and below is a copy of the meeting report.


This is the first report from the PRGI Lake Sub-committee. It focuses upon a recent meeting with stakeholders as noted below.

Summary of meeting held on Friday 11th Sept 2020 at Ruataniwha Service Centre, Kaiapoi

1. Attendees:

  • WDC – Gerald, Kelly

  • ECan – Paul, Adrian, Tina

  • PRGI – Matt, Roger

  • Golders - Stephanie

  • Templeton Group (via remote video link) – Chris, Andrew

2. Meeting Purpose:

To bring stakeholders up to a common level of understanding on the issues with Lake Pegasus such that next steps could be agreed.

3. The Parties:

Developer & Original Lake Owner – Infinity Group

Current Lake Owner – Templeton Group since early 2020 having taken over from Todd Property Group.

ECan – (i) Set original water quality compliance standards for development, and (ii) ongoing water quality compliance authority and issuer of non-conformance notices/penalties

Golders – Technical experts employed by lake owners to assist with ongoing water quality monitoring and design of necessary remedial actions.

WDC – (i) Local authority that set original resource consent standards and (ii) entity that will eventually inherit lake ownership upon exit of developers/owners BUT only with agreed compliance standard being met, ie no algal bloom for a consecutive 12 month period.

PRGI – Pegasus residents forum (i) lobbying for increased momentum in water quality resolution and (ii) representatives of ratepayers that will eventually pick up lake management costs upon exit of lake owner/transition to WDC control.

4. The Challenges Faced:

Lakes and waterways in NZ are generally seeing an increased occurrence of Algal Bloom. This is not a problem isolated to Lake Pegasus.

Algal Bloom creates the release of a highly toxic cyanobacterial Bloom requiring affected waterways to be shut for public (and animal) use.

Lake Pegasus, as a man-made lake, is now maturing. The original water quality experienced 10 years ago is not a realistic goal ongoing. The lake has only ever been formally consented for Secondary Standard use, ie non-immersive, non-swimming activities.

Lake Pegasus has now had 5 consecutive summer seasons of public leisure activity curtailed early due to Bloom. The period of lake closure has steadily grown longer each year.

The specific issues with Lake Pegasus related to Algal Bloom are:

i. Slow water flow – upon entering the lake, a drop of groundwater takes 200 days to exit to the wetlands.

ii. Water Stratification (layering) – associated with (i) above. Causes low water oxygen content and encourages conditions well suited to Algal Bloom.

iii. Proliferation of weeds – linked to both (i) and (ii) above. Weed control methods have their own set of challenges:

Chemical – toxic impacts to surrounding natural habitats

Trimming/Cutting – cuttings left to break down in the water can provide nutrients for Bloom to flourish

Removal – practical/economic considerations.

NB: The average lake water depth of 5m to 5.5m exacerbates the poor water quality situation. The deeper the water the stiller it will be. Theoretically, the lake depth could be reduced to promote better flow but this is highly impractical.

Through various changes in lake owner organisations, along with some poor information sharing to stakeholder groups, the full history and rationale for past decisions regarding the lake is lost or incomplete. For example, it is unknown if the existing SolarBees deployed in the lake to mix and aerate the water were ever adequately specified for the lake, especially as it matures.

Todd Properties were issued with non-compliance penalty notices over the past 5 years by ECan (although PRGI were only made aware in February 2020). These appear to have been largely ignored. Upon purchase, these are now owned by Templeton, to which a further non-compliance penalty notice has been added relating to recent water monitoring this year. Templeton are showing a genuine desire to resolve this largely inherited situation.

5. Potential Solutions to Water Quality:

Various and many solutions have been considered over time.

The current consensus for the focus of new solutions is now aeration (and possibly additional algal scrubbers) ie mechanical “agitation and mixing”, breaking down still water layering and improving the level of oxygen in the water.

The owner of the task to deliver an appropriate solution is the lake owner, ie. Templeton. However, they will need specialist technical advice from appropriate experts. In addition, any solution(s) will likely come with pros and cons that will need to be considered by the wider team of ongoing stakeholders, e.g run costs (impacts to WDC rates) and possible practical considerations such as noise and space impacting the residents’ environment and usage.

6. Next steps:

Templeton Group has now formally engaged Golders to specify and design potential solution(s) and come up with a realistic timeframe for review, selection and implementation. This proactive step is a massive step forward from the status quo.

Another meeting with stakeholders to assess progress will be arranged shortly by Templeton.

7. In summary:

Finally, we now have some meaningful traction and momentum in addressing the Algal Bloom issue for Lake Pegasus.

Sadly, without any new intervention likely being in place for this coming summer season, we should anticipate Bloom impacting lake usage once more. However, hopefully, we will have an improved situation for next year.

Matt James,

PRGI Vice-President and Lake Sub-Committee Team Leader.

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