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lakeside estates - wastewater treatment system

Lake Wakatipu and Queenstown Lakes is one of New Zealand's fastest-growing areas.

ACH Consulting is committed to preserving New Zealand’s pristine environments for our future generations. When the Lakesides Estates Homeowners Association approached us for help with their complex decentralised wastewater treatment system, on the shores of Lake Wakatipu, we were keen to put our experts on the case to ensure a great outcome for both our client and our iconic lake!

Lake Wakatipu and Queenstown Lakes is one of New Zealand's fastest-growing areas. With intensive development, proper management of wastewater is critical and Councils are imposing requirements that each residential subdivision will be required to provide high quality treatment of wastewater for land discharge. Lakeside Estates, a gated community near Queenstown, was one such subdivision.

When working on complex decentralised wastewater treatment we endeavour to provide designs with great treatment levels that deliver economical and future-proofed results without compromise to our environment. 

Located on the southern shores of Lake Wakatipu this development is outside the area covered by the reticulated wastewater network which services Queenstown. The existing wastewater treatment system servicing 36 residential dwellings was not only outdated but would not be able to meet the conditions of the new discharge consent from Otago Regional Council.  Time was running out to get compliance. 

There were a number of special conditions, and challenges to overcome on this particular site.

  • Close proximity to Lake Wakatipu, meant risks of adverse effects on the environment were particularly high.

  • Nutrient loading in lakes, particularly nitrate and phosphorous, can cause algal blooms and anoxic conditions to receiving waters. An abundance of nitrogen can kill fish, cause uncontrolled algal blooms and be detrimental to human health.

  • Human borne pathogens such as E.coli if not removed from the wastewater stream can result in public health threats.

  • Whatever system was installed needed to be able to operate within the Queenstown temperatures which range from -10°C during winter to +30°C during summer. 

  • The complexity of the underlying alluvial soil presented challenges in terms of land disposal. Ineffective land disposal can lead to adverse impacts on the water quality such as eutrophication of water bodies, and odour.

  • CAPEX and OPEX for the installation and the life of the system.

  • Upgrade works needed to take place over the warmer season, which meant also during a peak occupancy period for the subdivision. We had to ensure minimal disruption to the existing community during these works.

  • Two regulatory bodies held control over the consent being both the Otago Regional Council & the Queenstown Lakes District Council.

ACH researched the performance and track records of different technologies and systems, and how well those systems could operate in the climatic conditions of the central Otago Area. Track records of the various systems and service providers were also considered.  Capital costs and long term operating costs over the 20 year period of the consent were tallied and adjustments made for inflation.  

Tertiary treatment using UV and Nitrogen reduction were recommended as part of the upgrade to keep the lake and community free from pathogens and algal blooms. The best practical solution to future proof the design was provided, which in the case of Lakeside Estates was the Recirculating Textile Packed Bed Reactor (rtPBR) treatment system provided by Innoflow New Zealand. 

ACH Consulting were engaged again following investigation works to manage the installation of the new treatment plant and effluent disposal area. The land disposal area was steep and needed to be re-contoured to reduce steep areas and remove minor flow paths which would cause the effluent to pool.  Moreover, the land needed to be replanted prior to the end of May so as to achieve some establishment of vegetative cover prior to the wetter winter months.  Delayed replanting had the potential to cause a significant amount of sediment to enter the lake.  

Due to the volume of wastewater generated on site the effluent disposal field needed to be large, over 5000 m2.  The planting needed to provide further reduction of nutrients and optimal evapotranspiration even in the colder months.  In addition the disposal field was highly visible to the community and needed to provide high amenity value in terms of a beautiful view.

When completed the following outcomes were achieved:

  • Lakeside Estates had a treatment plant that could handle the climate and be expanded if population increased.

  • The treatment quality is such that the resulting effluent is suitable for irrigation purposes in the future if drought conditions became severe and has no adverse effects on the health of Lake Wakatipu.

  • The installation of the plant and upgrading of the wastewater lines was used as an opportunity to also lay conduit to allow for fibre optic cable installation when it is available to the area.

  • The re-contouring and replanting of the area which provides effluent disposal saw the property rid of pest species and replaced it with good native vegetation. 

  • The project was completed prior to the consent clock running out and Code of Compliance received, so that Lakeside Estates and the Homeowners Association remained within compliance of their Wastewater Discharge Consent thus avoiding fines from the district and regional councils.

During this process, ACH Consulting has developed good working relationships with the Otago Regional Council, Queenstown Lakes District Council, as well as suppliers and service providers in the region.  Our Auckland based location is no impediment to working nation-wide. If you have any questions about this project or your wastewater project throughout New Zealand please do not hesitate to contact us.  We are happy to provide the best options for your development wherever you may be.