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Dirt Cheap? Are rapid house builds trashing the environment?

The pace and scale of public and private sector new home building is unprecedented. Here I reveal a major potential downside of this rapid development – the runoff of sediment from building sites into stormwater pipes, streams, lakes, beaches and harbours – and show how a business opportunity can help us build houses that don’t cost the earth.

NIWA estimates 98% of the lucrative West Coast snapper fishery is hatched in the Kaipara Harbour. The Waitemata Harbour is a significant commercial, cultural and recreational fishery.

Why is this relevant to housing needs? Because we need to build thousands of homes to catch up – and hopefully keep up – with population growth.

But there’s a catch: the best places are near water – think Auckland’s urban beaches and the internationally acclaimed Hauraki Gulf, soon to host the America’s cup once more. Think also of our biggest rivers, most popular beaches and our incomparable Southern lakes. If we don’t keep the soil on the land when we open up a site for building, it gets into our stormwater systems and streams and ends up all over our beaches, filling in our estuaries, smothering seafloor life and creating a tidal wave of mangrove expansion into our harbours.

Throw that into the mix with these stats:

  • sediment is a very serious and widespread contaminant in global and New Zealand waters
  • sediment yield from bare earth exposed by earthworks is up to 1000 times greater than from soil protected by forest[1]
  • as little as 1mm depth of mud across 1% of estuarine habitat can cause over 10% reduction in the biological diversity that’s the basis of our fisheries
  • fisheries are a big export earner for us, boosted by our “clean, green” image
  • tourism now ranks as a top national income earner for the same reason –

– and we have a serious threat to our economy and our community wellbeing.

And the speed of the post-GFC housing catch-up has ramped up so fast that there hasn’t been time for the building industry or the councils to catch up.

The problem with small construction sites

In my 25 years of environmental training, I’ve seen the civil construction sector work with councils to get well on top of erosion and sediment control on large construction sites – big subdivisions, highways, water infrastructure and the like. Together, they’ve created a large body of skilled environmental staff to meet the ever-higher environmental expectations of communities and clients.

Strangely, in all that time we’ve never really got on top of what happens when the residential subdivisions are grassed down, signed off by the council and sold off to homeowners, then opened up by builders, exposing the earth once more to the intensely erosive impact of raindrops and runoff.

It’s not surprising then that many builders are putting up houses as fast as they can to meet the country’s housing shortage, only to find they’ve got irate neighbours breathing down their neck about mud all over the street, or council staff turning up in response to a water pollution complaint.

But wait – we’ve been building houses like this forever. So why is it such a big deal all of a sudden?

For local communities and environmental professionals, it’s been a big deal all along, but it’s been surprisingly tricky to fix, so while housebuilds were at a relatively low level, councils focused on other pressing work.

Today, however, councils and communities all over New Zealand are fast waking up to give the issue of sediment runoff from small construction sites the attention it needs.

And this comes at a tough time. Already under pressure with the construction boom, most builders will be thinking, “This is totally unrealistic – we haven’t even got the time to build all the houses that need building, let alone do a whole bunch of extra environmental stuff!”

And yes, it is yet another compliance requirement. But it needn’t be a big deal – and for any builder who likes fishing, there’s a personal incentive to find the smartest way to do it well.

And there are some business opportunities there, too. Let’s take a look.

The problem with sediment runoff from small construction sites

Sediment runoff gets into green infrastructure that’s designed to hold back stormwater runoff to prevent flooding and treat it to prevent pollution, clogging the system up so it can’t do the important job it’s designed to do. The mud running off even a few building sites can cause local flooding that harms nearby houses, costing the owners time, money and grief.

And at the point where this happens, the piped stormwater system, rain gardens and treatment ponds have been handed over from the developer to the council, which has to pay to clean it all out. That significant cost falls on the long-suffering ratepayer.

The cause of the problem

Big civil construction sites need resource consents that ensure a high standard of erosion controls and sediment controls to protect the environment. But not all house-builds require resource consents, and building consents are too often issued without requiring environmental controls – not just on sediment runoff but on pollutants like concrete and paint as well as construction and demolition waste.

So housebuilds slip through the compliance net, and by the time the first building inspection is due, the earthworks for the driveway and foundations are already opened up, often with no controls, so mud gets everywhere. Worse still, most councils don’t have enough inspectors with the right skills to get round all the growing numbers of building sites to advise on best practice.

Common results[2] are:

  • muddy roads as a result of vehicle movements on and off sites
  • more mud from uncontrolled runoff from clearing vegetation, trenching, retaining walls, foundations and driveways
  • sediment entering stormwater systems and receiving environments
  • sedimentation and expensive maintenance of stormwater treatment devices such as raingardens, wetlands, ponds and pipes
  • discharges of other contaminants to stormwater systems and receiving environments, such as paint and concrete.

What councils are doing about the problem

Councils around the country are putting out great information to help people do the right thing. Inspectors target areas of intense building activity and if they find a site with no controls or inadequate controls, they’ll explain what needs to be done and give the builder a week to do it. If their return visit finds ongoing non-compliance, they can send an infringement notice in minutes. It’s not an ideal or even comprehensive process but it’s better than nothing and this engagement with the industry yields good results.

That said, in an ideal world, all builders would undergo environmental training as part of their qualifications – but that’s a generation away and our streams, lakes and harbours can’t wait that long.

The scale of the problem and the training gap

The sheer number[3] of builders out there, even in Auckland alone, makes it totally unrealistic to deliver environmental training to them all. While we put the training in place through the industry training organisations, we have to think of something else to protect the environment in the meantime.

Towards an interim solution to the problem

25 years ago, coastal areas of Australia experienced the same building boom we did – but while we started controlling sediment runoff from the big horizontal (civil) construction sites, they started with the small vertical (house) construction sites.

In the New South Wales-Queensland boom areas, sediment runoff was clogging up council stormwater drains, smothering the local streams with sediment, staining the surf beaches and flowing on out to settle all over the Great Barrier Reef.

John Dunlop, a staffer at the Sunshine Coast Council, set up a program where every house site had to have an erosion and sediment control plan before the building was allowed to start. He realised this offered a commercial opportunity, and as soon as the program was up and running, he left the Council and set up a company called Digger Dunlop. 22 years later, Digger Dunlop is still going strong and is proud of its certification from the Australasian chapter of the US-based International Erosion and Sediment Control Association (IECA).

For the princely sum of $AUD 7-800 (more for very big or tricky sites) the firm will:

  • draw up a simple erosion and sediment control plan to meet council requirements
  • install the controls
  • maintain them after rain or damage like a truck backing over the silt fence
  • take them away at the end of the job for use on the next site.

Our thinking has been based on the premise that the builder must be trained in erosion and sediment control. But consider that builders don’t all do the plumbing, glazing, painting, wallpapering and other specialist jobs: these are line items in the quote to the customer. All the builder has to know is that environmental controls are compulsory, how much they’ll cost and when to call a service provider to install, repair and remove them.

Training for Green Jobs

Here’s where this commercial opportunity becomes a strategic training opportunity: if we only have to train a much smaller number of erosion and sediment control experts for the vertical construction sector, the job instantly becomes more manageable.

For this to work, we need:

  • clear specifications of what controls are effective
  • councils making sure that every building consent and if relevant, every house-build resource consent, requires the appropriate environmental controls
  • councils having enough trained inspectors to ensure compliance
  • big vertical construction companies having trained staff on board to ensure controls are used on all their sites
  • small environmental control firms trained to service smaller building firms
  • third-party certification of council and company staff doing this work
  • industry partnerships to reach out across the large and diverse vertical construction sector.

Here’s what we already have:

  • local authorities and other relevant bodies in New Zealand – the IECA, BRANZ, Green Building Council – already have the information on tap
  • a group of erosion and sediment control professionals who can deliver training to the councils and companies working on small sites
  • an internationally recognised third-party certification system for large horizontal construction sites that could readily be adapted to meet the environmental needs of small vertical construction sites – the IECA’s Certified Professional in Erosion and Sediment Control (CPESC) program
  • an industry training organisation, the Building and Construction ITO (BCITO) that can work with experts to develop and deliver environmental training as part of its apprenticeships
  • a major industry association, the Construction Industry Council (CIC), that can reach out to all its member organisations across the building and construction, design and property sectors.

The erosion and sediment control and wider environmental management sector in New Zealand is characterised by strong cross-sector partnerships. We can work together to make sure that erosion and sediment control service providers and council staff alike attend the same training and get the same certifications for erosion and sediment control, pollution control and construction and demolition waste minimisation. This protects the environment while we set up the wider building industry training and its environmental management programs that we need for the long haul.

It’s doable. Let’s make a start right now on helping builders protect the environment while we build the partnerships needed to put in place the more comprehensive longer term solutions.

Two things every builder can do:

Put erosion and sediment control as a line item in every proposal and budget for it – just as you would for the sparky, plumber, roofer and other specialists. There are simple tools to use and suppliers out there who know how to use them: just search for “erosion and sediment control companies, New Zealand”.

Then go fishing – and feel good that you’re protecting the waters fish flourish in!


This blog triggered the two excellent comments below .

Resource Management Consultant Richard Tong highlighted something that dimly went through my mind with respect to the wonderful quote from Will Rogers that I’d included in my newsletter linking to this blog. Here’s the quote:

There are three kinds of men. The ones that learn by reading. The few who learn by observation. And the rest of them who have to pee on the electric fence and find out for themselves. Will Rogers, Cherokee-American cowboy, comedian, humorist, social commentator, vaudeville performer and actor, 1879-1935

Here’s Rick’s comment, which made me laugh as much as the quote does!

Hi Clare, Loved your enewsletter – just an odd point from your friendly pedant.  You had better credit Will Rogers with some other quite extraordinary skills – special American ones like those ones than Donald Thump has. The invention of electric fences is generally credited to Kiwi, Bill Gallagher, around 1936-37.  The Americans had earlier lethal versions, as did the Germans in WWI when one section was credited with killing 3,000 Allied troops.  We can be confident that they were not all relieving themselves. This leaves the mystery of how Will Rogers managed to make his observations and pass them on to others in the two years after his death.   Have a great festive season.

Soil conservator extraordinaire Lee Whiley manages a number of properties in Auckland. With respect to the blog above, he very cleverlee  made some points in his own inimitable style, from his own experience:

There is no housing crisis in NZ in terms of numbers available: there is an affordability crisis. It is difficult to find tenants right no. It is difficult to sell houses right now. There are plenty of houses but with compliance and construction costs possibly the highest in the world and wages comparitivelee low, people can’t afford to buy or rent them.


[1]         Department of Natural Resources and Environmental Control, Delaware, USA (1989) Delaware Erosion and Sediment Control Handbook.

[2]         Erosion and sediment control on small construction sites: Co-creating a process for changing our practice in the Mahurangi (2016) A report prepared for the Auckland Council in June 2016 by Beca Ltd (Beca) and Clare Feeney of Environmental Communications Ltd.

[3]         The numbers in the diagram come from the following sources: