Rethinking soil – making the most of C&D waste

27 October 2025 marks the start of the first-ever Construction Waste Week in New Zealand. Organised by WasteMINZ, it shines a spotlight on the scale of construction waste across the country and the smart ways organisations are tackling it.

While much of the focus is typically on construction and demolition (C&D) waste like concrete and timber, one resource that is often overlooked is soil. In this article, we dig deeper into this invaluable natural resource.

One teaspoon of soil can contain more living organisms than there are people in the world^[1] and it plays a vital role in our ecosystem, supporting carbon sequestration, nutrient cycling and water filtration. Yet despite its ecological significance, soil is often treated as waste in C&D.

Soil and other C&D waste that are unsuitable or impacted by contaminants – including petroleum hydrocarbons, heavy metals and asbestos – are typically sent to landfills, at both financial and environmental cost. With soil making up approximately 78% of all levied C&D disposed material^[2], there’s a significant opportunity for the industry to rethink how contaminated and unsuitable soils are managed.

At Davis Ogilvie, our geotechnical engineers and contaminated land specialists are actively involved in the strategic management of surplus soils across residential, commercial and infrastructure developments. Through early-stage site investigations, in-situ remediation and source segregation, we aim to minimise the amount of soil sent to landfill, reduce project carbon footprints, and promote circular economy principles in the built environment.

Our commitment to sustainable soil reuse is reflected in proactive strategies where appropriate, such as:

• retaining surplus soil onsite as landscape and amenity features
• working with our structural engineers to use foundations that reduce soil disturbance, such as piles
• blending soil onsite to reduce overall contaminant concentrations
• collaborating across our multidisciplinary team to transform contaminated sites into functional assets.

We also work closely with our clients and explore the most effective way to manage contaminated soil, taking into consideration transport, the cost of disposal, site-specific constraints and long-term land use, to deliver solutions that are practical, cost-effective and environmentally responsible.

For example, we recently helped a client divert around 500 m³ of contaminated soil from landfill by working with them to design and construct a landscaped, onsite storage area. This solution saved thousands in transportation and landfill fees, and it will ultimately form an attractive planted entrance feature to the property.

This example shows how C&D waste – in this case, soil – doesn’t have to end up in landfill. Engaging experienced contaminated land specialists and environmental scientists who explore alternative approaches, can reveal ways that transform surplus or contaminated soil into a useful part of a project, rather than simply disposing of it.

As a multidisciplinary team, we combine in-house expertise across engineering, surveying and planning to deliver practical, sustainable outcomes. Talk to us about your project, and how we can help you make an informed decision on making the most of the soil on your site.

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[1] British Society of Soil Science (2023).

[2] Ministry for the Environment (2025) New Zealand Construction and Demolition Waste Baseline & Tracking Methodology Report.