An Auckland construction company has been fined $35,000 after pleading guilty to three Resource Management Act (RMA) charges arising from repeated failures to contain concrete slurry and sediment on its site. The penalties followed releases that contaminated Auckland’s stormwater network, with the company also having breached an abatement notice issued by Auckland Council after earlier incidents.
Auckland Council Team Leader Investigations Paul Cowling was direct about the purpose of the rules: “Resource consents, erosion, and sediment control rules exist to protect Auckland’s waterways and harbours.” The case is a reminder that non-compliance in this area carries real legal and financial consequences, and that enforcement is active.
Why Concrete Slurry Is a Particular Risk
Concrete washwater and slurry are highly alkaline and carry fine suspended solids that can cause significant harm to waterways when they enter the stormwater system. Unlike some forms of site runoff that simply carry sediment, concrete washwater also has a pH that is harmful to aquatic life. Auckland’s stormwater network drains directly to harbours and streams, which means that what leaves a site uncontrolled can end up in sensitive coastal and freshwater environments relatively quickly.
What the Rules Require
Before construction work commences, sites need an Erosion and Sediment Control Plan that identifies how runoff will be managed across the full range of conditions the site will experience. Clean water entering the site from outside the disturbed area should be diverted away from construction zones. Sediment controls such as silt fences and retention areas must be installed, inspected regularly, and maintained after rainfall events.
Concrete washwater requires specific management. All water from truck washout, pump cleaning, and tool cleaning must be contained on site, not discharged to any stormwater inlet, waterway, or neighbouring property. Clearly marked and properly bunded washout areas, along with reusable washout systems where available, are the expected standard.
Practical Site Management
Staff training on what the controls are and how to respond to spills is essential — the controls only work if the people on site understand what they are for and what to do when something goes wrong. Detailed inspection and maintenance records, kept throughout the project, demonstrate due diligence if a complaint or investigation follows.
Concrete recycling programmes offer an additional tool: material that does not go to the stormwater system cannot contaminate it. For sites generating significant quantities of washwater, investing in a more systematic management approach pays dividends in both compliance terms and reduced material waste.
Explore more compliance guidance for New Zealand construction sites, or connect with environmental and resource management specialists in your region.
