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Largely Unchanged 1990s Sediment Treatment 

New Zealand arguably leads the world in the design, building and operation of the high efficiency sediment retention ponds. While the rest of the globe works to catch up with this highly effective technology the New Zealand leaders in the deployment of this approach have their eyes on the future, a future where changes in climate and compliance standards represent challenges to the success of these 30-year-old design specifications. Intended to provoke, this opinion piece takes a reflective look at the implications for contractors in 2022 and beyond who have grown up with Auckland Council’s Technical Publication 90 (TP90) and more recently Guidance Document 5 (GD05). As design specification bibles these may now be starting to show inconsistent outcomes in certain circumstances. Environmental performance standards imposed by permit conditions are increasing. However, regulators are still mandating the 1990s technology as the basis to achieve that standard. Climate change, more particularly increases in rainfall intensity, now lead us to ask whether the mandated technology designed 30 years ago allows us to achieve these imposed standards. Using the Wellington City Omaroro Reservoir Project as an example of the challenges this presentation will examine closely how the 1990s technology is having to adapt and how the design and implementation of sediment controls was deliberately exceeded and is world leading. The Omaroro Reservoir is a 35,000,000 L earthquake resilient tank in the middle of suburban Wellington, involving 40,000 m3 of earthworks within the inner city and the presence of two streams running through it.


Simon Cathcart
National Environmental Manager, HEB Construction Ltd


Simon has worked on both sides of the compliance equation. Having worked for Auckland Council in soil and water resource roles and Waikato Regional Council in an investigation and enforcement role. Over the last 15 years he has worked in construction as an environmental practitioner. In the last 6 years he has assembled New Zealand’s largest construction based environmental team. Simon has a reputation for constructive disruption and getting quickly to the point where not just good business outcomes are achieved but quality environmental outcomes.



Wednesday 7th December

In the Context of a Changing Climate and an Ever-changing Landscape of Construction related Compliance Conditions 

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