Hidden beneath our feet is a more complex geological profile than we think. A geotechnical assessment could be the difference between the success or failure of your effluent project.

Engaging a geotechnical engineer not only ensures you meet regional council resource consent and district council building consent requirements, but can also lower the uncertainty and risk involved in your effluent storage design – so you can avoid costly construction and remediation activities.

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It’s not just a tick box exercise

With increasing media attention around the environmental impacts of the dairy industry in New Zealand, it’s no surprise that enforcing stringent legislation conditions has become the new norm.

Legislation overseeing the industry primarily relates to the Resource Management Act 1991 and the Building Act. Regional and district councils regulate aspects of construction to ensure farm effluent storage structures are built to minimise environmental impacts should something go wrong. As part of this process, professional advice from a certified engineer and related specialists is now a requirement to gain resource consent. This could come from two sources:

  • a civil engineer or supplier for structural design
  • a geotechnical engineer for ground foundation design

Why use a geotechnical engineer if you can get consent sign off using a civil engineer or other supplier?

A geotechnical engineer will understand local ground conditions better than most. This is critical in designing a stable and effective foundation option for your dairy effluent storage structure.

Once an effluent structure is built and loaded, it starts exerting force upon the underlying soils. In poor conditions, this force can potentially lead to ground failure, and what follows is a whole raft of remediation works that are costly, and time consuming.

This can occur in two ways - bearing capacity failure and settlement.

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Bearing capacity - when the ground (or part thereof) beneath the structure can’t support the loads imposed and ‘gives way’, destabilising the structure.

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Settlement - when the loads imposed by the structure cause the underlying ground to compress and the structure to ‘sink’ into the ground. Farming land consisting of peat and organic clay type soils is most susceptible to this, with destabilization happening over an extended period of time.

It starts at the foundation

A civil engineer will have a good understanding about ground strength conditions in order to oversee earthworks and construction of an effluent structure. Choosing to only work with them may have short term cost benefits - but what about the long term?
Geotechnical investigation of the soil properties and ground water levels on the construction site will determine the optimal foundation design to avoid ground failure beneath the structure. The foundation is the make or break element in terms of the integrity of the structure – and can be the most costly and difficult to fix when problems arise.
An engineered foundation may mean higher upfront costs, but will provide peace of mind that this investment will be money well spent.

How Coffey can help?

It might seem like an additional and even unnecessary step – but the threat of noncompliance, costly remediation and the associated down time should make it worth it.

We have a proven track record working in the Waikato region on effluent based projects. We’ve provided detailed ground investigations to support effluent sump foundation design and solutions to overcome challenging ground conditions, to mitigate risks of future settlement.

Dairy effluent tank foundation - geotechnical investigation and design

Effluent storage tank foundations

We work closely with you and other parties involved, delivering effective and stable foundation design options.
This shouldn’t be about going through the motions to get consent. There are some real savings in carrying out thorough investigations – not only in monetary terms, but in lowering your uncertainty and risk for long term benefit.

Are you armed with the right information about your ground conditions? If not, we’d like to help.

Contact Kori Lentfer, Associate Engineering Geologist on +64 21 880 831 or via email at kori.lentfer@coffey.com or, Luke McCann, Engineering Geologist on +64 21 636 951 or via email at luke.mccann@coffey.com