Minimising on-site pollution
Sediment, runoff, paint and other contaminants can harm people and the environment.
Under the Resource Management Act, you’re responsible for discharges of any contaminants - which can include solid or liquid waste, airborne pollutants, and even noise and energy - from your property.
With good management of your building or renovation site, sediment and other contaminants can be contained or disposed of safely.
Airborne pollutants
During construction airborne pollutants can come from:
- dust from construction materials and bare ground - this can cause irritation and long-term harm
- volatile organic compounds (VOCs) from paint, sealants, glues, particle board and some other construction materials - VOCs such as formaldehyde can cause asthma and other health problems
- smoke from incinerators.
Exposure to airborne pollutants can be reduced by ensuring work is carried out in well-ventilated areas, and by wearing dust masks and, where necessary, respirators.
For information about minimising exposure airborne pollutants in your home, see Unhealthy Air. For information about choosing building materials to avoid exposure to airborne pollutants, see materials.
Asbestos
A single exposure to asbestos dust has been known to cause asbestosis and death several decades later. If you’re renovating and uncover material that you think may be asbestos, contact your local Occupational Safety and Health (OSH) office (see the OSH website for contact details).
Asbestos materials should only be removed and handled by contractors experienced in this type of work - look under ‘Asbestos’ in the Yellow Pages (www.yellowpages.co.nz). The Occupational Safety and Health website has guidelines on management and removal of asbestos.
Sediment
Bare soil on a building site will get muddy when it rains. If there is any slope, the water will flow downhill carrying loose soil. This erodes the building site and also moves the soil to where it isn’t wanted - a neighbouring section, stormwater drain, or a stream.
Sediment can clog up waterways, harming plant and fish life. It can also contribute to flooding by reducing the ability of the stormwater system to handle runoff. In addition, the sediment can carry harmful waste such as paints or chemicals from the building site.
There are two ways to keep sediment out of waterways: design and build your home in ways that prevent soil erosion, and contain any sediment that is created during the construction process on-site.
You may require a resource consent for earthworks on your property, and may be responsible for any harm caused by sediment runoff that harms neighbouring properties or waterways. Check with your local council before starting work.
Preventing soil erosion
The risk of erosion is increased by:
- earthworks, which expose bare topsoil and alter natural drainage channels
- removal of vegetation.
The most effective way to reduce the risk of erosion is to design your home or renovation to minimise the need for earthworks - for example, by keeping its ‘footprint’ as small as possible or by using foundations that don’t require large excavation.
During construction, erosion can also be prevented by:
- carrying out earthworks in summer to reduce the likelihood of rainfall causing heavy runoff
- diverting water away from the excavated area using diversion channels, contour drains or small embankments
- protecting bare soil with tarpaulins
- removing the minimum amount of earth and vegetation
- having a single vehicle access point
- stabilising bare soil as soon as possible with semi-permeable paving, mulches, plants and turf (hydroseeding techniques are often used on bare cut slopes).
Trapping sediment on the site
There are various ways to trap sediment:
- Existing vegetation can slow the flow of water, allowing sediment to settle.
- Silt fences use screen filter fabric to trap the sediment. These must be strongly constructed - otherwise a strong water flow can knock them over.
- A row of hay bales allows water to run through while trapping sediment. These may have to be weighted down.
- Sediment ponds allow sediment to settle. They have a drain near the surface which carries water away.
Cement, concrete and asphalt runoff
Concrete contains lime, which is highly caustic. Concrete pollution can occur when new concrete is laid, when concreting equipment is washed, when concrete is waterblasted to expose the aggregate, and when concrete is cut or ground. This can harm fish, plant and insect life in streams and waterways. it needs to be contained on site.
Bitumen and asphalt contain hydrocarbons which are also toxic in waterways.
To minimise the potential harm, runoff from unset concrete and from bitumen and asphalt needs to be kept out of waterways - for example, by diverting it to nearby grass or soil or by collecting it for safe disposal elsewhere.
If you’re hiring a contractor to do concreting work, check what they’ll be doing to ensure the runoff doesn’t get into waterways. You may be legally responsible for any harm they cause.
Solvents and paint
Solvents and paint can harm plant and animal life if they get into waterways. They should never be tipped down stormwater drains, and paintbrushes shouldn’t be washed in areas where the runoff will enter stormwater drains. Paints should be kept for touch-ups or future jobs, or disposed of responsibly.
Light Organic Solvent Preservative (LOSP) fungicides are now used to treat timber. Any LOSP fungicide that gets into streams is deadly to fish. The alternative boric treatment is much more benign.
Demolition/renovation hazards
Some older buildings contain hazardous materials such as:
- lead-based paints
- lead-head nails
- asbestos insulation and sheeting (see Asbestos above)
- fluorescent lights containing mercury.
If you’re renovating or demolishing/deconstructing a building, special care will need to be taken with these materials. None of them can be dumped in an ordinary landfill.
The ConsumerBuild website has a page about safe removal and disposal of lead-based paint, and OSH’s website has guidelines on management of lead-based paints.
Contact your local council for advice about safe disposal of fluorescent light tubes (they contain mercury and cadmium).
Legal
Under the Resource Management Act, you’re responsible for any discharge of contaminants - which can include solid or liquid waste, airborne pollutants, and even noise and energy - from your property.
The Resource Management Act is administered by regional and local councils, which can permit certain activities affecting the environment and issue resource consents for others.
Contact your local and regional councils before you carry out any earthworks or do anything else that could involve a discharge of waste into the environment.
Building consents can also require you to control stormwater and sediment runoff.
Pollution on site may also be covered under the Health and Safety in Employment Act 1992.
More information
From Smarter Homes
From ConsumerBuild
From other sites
The REBRI (resource efficiency in building and related industries) website has practical advice about minimising waste on construction sites.
The North Shore City Council’s website has a page on pollution prevention.
The National Institute of Water and Atmospheric Research’s website has a page on pollution including the impacts of sediment on waterways.
The Auckland Regional Council’s website has information about works involving concrete, cement, lime and asphalt.
The Waitakere City Council’s website has a factsheet Site Earthworks (154k PDF) and a page about a regional project to reduce concrete-related pollution.
The Ministry for the Environment’s website has pages about environmental issues including water and air pollution.
Information about the Resource management Act can be found at www.rma.govt.nz.
