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Dunedin City Council – Kaunihera-a-rohe o Otepoti
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Preventing stormwater pollution

Day-to-day activities, both business and residential, can significantly affect stormwater quality as it is not treated before it is discharged.

Stormwater pollution creates ecological damage and can be a threat to public health by preventing us from taking part in and enjoying recreational activities around water.

We have set limits on what may be lawfully discharged to the public stormwater system - stormwater drains should only carry stormwater!

What is a pollutant?

Some pollutants are more obvious than others, such as oil, paint, and other chemicals can make our streams and beaches unpleasant and even dangerous for us and aquatic life. Litter is easily carried into and through the stormwater system.

Lawn fertiliser, car wash detergent, and even soil are pollutants too. Excess fertilisers can cause algae blooms that use up all the oxygen in the water killing other aquatic life. Detergents can kill aquatic life as well. Topsoil carried into the ocean by stormwater can limit sunlight penetration, coating aquatic plants with sediment killing aquatic life.

Examples of types of pollutant

Organic

  • Leaves
  • Grass clippings
  • Animal droppings
  • Compost
  • Bark chips
  • Fuels
  • Oils and grease
  • Food
  • Sewage

Inorganic

  • Sediments
  • Cement
  • Paints

Solid Waste

  • Litter
  • Glass/plastic bottles
  • Cans
  • Cigarette butts

Chemicals

  • Antifreeze
  • Industry chemicals
  • Fertilisers
  • Pesticides
  • Car washing
  • Cleaning products
  • Outdoor cleaners
  • Chlorine (spa and swimming pool water)

Metals

  • Zinc from unpainted roofs
  • Brake linings from vehicles
  • Copper
  • Lead

To prevent stormwater pollution

  • Identify where your stormwater and wastewater drains are.
  • Do not dispose of wastes down the stormwater drain.
  • Take action to prevent or minimise pollutants entering the stormwater system.

Stormwater protection

Accidental spills

If you have a minor accidental spill of a liquid pollutant, try and stop the substance getting into the stormwater system. You could use sand or sawdust to absorb it, hose the area onto a permeable surface (such as grass or gravel) or even try to soak it up with a towel or similar.

If a small spill enters (or is likely to enter) the stormwater system, or you have had a large spill of a hazardous substance, please call us on 477 4000, the Otago Regional Council on 0800 800 033, or the NZ Fire Service on 111 for help.

Car/vehicle washing

Water used for washing cars contains sediments, heavy metals (eg zinc and copper), soaps, surfactants, oils and grease.

  • Avoid using detergents. Using an environmentally-friendly cleaning product helps but is not by itself enough.
  • Use dry-wash methods to minimise water use.
  • Wash on an unpaved surface like grass or a gravel driveway as many of the pollutants will get broken down by microbes in the soil.
  • Prevent wash water from entering street gutters – you may need to redirect dirty water onto an unpaved surface.
  • Use a commercial car wash as they discharge to the wastewater system.

Community fundraising carwashes

  • Hold your carwash on an unpaved or grass area.
  • Wash on areas where the dirty water can be discharged to the wastewater system, such as a commercial wash-down pad - talk to your local petrol station or carwash facility.

Green Waste

Sediments like mud and stones and lawn and hedge clippings can block stormwater drains and cause odours.

  • Compost green waste.
  • Sweep rather than hose.
  • Cover piles of dirt and mulches to stop them washing into stormwater drains in heavy rain.

Moss and mould killers - roof, path and decking

  • Clean surfaces with a brush to reduce or eliminate chemical use.
  • Use environmentally-friendly products and follow manufacturer's instructions.
  • Let contaminated water flow onto soil or grass. For the roof, disconnect downpipes temporarily and drain the chemicals onto the ground.

Painting

  • Buy just enough paint to do the job at hand.
  • Contain paint flakes and dust. Do not wash down with water – sweep and dispose of in a rubbish bag.
  • Do not paint if it is likely to rain. If it does rain and fresh paint is washed off, direct it away from stormwater systems onto permeable surfaces. Disconnect downpipes if the paint is on the roof and direct onto soil or grass.
  • Do not dispose of unused paint into the stormwater system.
  • Brush out excess paint on to cardboard or newspaper, leave to dry and put in your general rubbish.
  • Do not wash paint brushes on the roadside or over outside drains.
  • Wash water-based paint from brushes so that the wash water drains to wastewater (inside drains) or onto soil or grass.
  • Wash oil-based paint brushes in solvent and wait for the paint to settle and drain off solvent for reuse.

Disposal of unwanted or unused paint

  • The Green Island Landfill no longer accepts old paint.
  • Resene Paintwise Recovery Programme - When buying Resene paints, you pay 15c per litre as a disposal levy, but it is free to bring back unused paint. If you bring non-Resene paint, and for trade customers returning paint, it costs $1 per tin up to four litres, or $2.50 for tins 10 litres or larger.
  • These fees are passed on to the Resene Foundation charitable trust and are used to pay for the cost of running the service. Resene Colourshop is located at 172 Crawford St.
  • Charity Barn - this store accepts good, clean paint for re-use through their paint exchange programme. Charity Barn is located at 329 Kaikorai Valley Rd (former Fisher Aluminium Building) Phone 03 453 3247.
  • Oil and water based paints - To dry your paint, take the lid off, add some sand or sawdust and leave for several weeks. When it is completely dry, put the lid back on tightly and dispose of it in your general rubbish.

Pesticides and fertilisers

These chemicals are highly toxic to waterways - do not pour unwanted or unused chemicals into stormwater drains, streams or rivers.

  • Use sparingly, or better still make your own natural pesticides or liquid fertiliser.
  • Avoid application if the weather forecast is for rain.
  • Read instructions before use and follow manufacturer's instructions. Do not over-use or over-dose chemicals. If you feel you must use a pesticide or herbicide, follow the label directions very carefully as applying more than the label allows is risky for you, your family and the environment.
  • Make up only what will you will use.
  • Rinse out equipment with clean water and dispose of that water onto soil or grass – but do not dispose of on grassed areas if a weed killer has been used.
  • Dispose of rinsed used containers appropriately, ie in the rubbish or the recycling system.
  • Avoid overwatering your lawn.

Disposal of unwanted chemicals

  • Do not dispose of unused chemicals in the general rubbish. Unwanted chemicals can be disposed of at the Green Island Landfill. Please let the booth attendant know you want to dispose of unwanted chemicals.
  • The chemical needs to be in a secure container and labelled. Landfill charges will apply. For large amounts, please contact the Green Island Landfill Engineer.

Pet waste and manure

Animal waste can degrade water quality as it contains pathogens such as bacteria, parasites, and viruses. When they wash into recreational waters, they can make people sick with sore throats, intestinal problems, rashes, nausea, and eye and ear infections.

Animal waste also contains nutrients such as phosphorus and nitrogen that fertilise aquatic algae blooms and promote bacterial growth in water.

Disposal of pet waste

  • Pick it up in a bag and dispose of it in general rubbish.
  • Flush it down the toilet (flush only the pet waste, not the plastic bag!).
  • Bury it away from the garden, drinking water sources, and walking areas.
  • Create a pet waste compost.

Subdivision/Earthworks

Sediment/erosion control measures should be in place for earthworks activities.

Many subdivisions require a Resource Consent, which will usually include a condition that all practicable measures are used to mitigate erosion and to control and contain sediment-laden stormwater run-off during site disturbance, in accordance with the Dunedin Code of Subdivision and Development 2010.

We have guidelines for sediment control on small sites (see Silt and Sediment Control Guide in the related information section) and the ORC has rules about discharges of sediment to water. In particular, you may not discharge sediment to water from land disturbance if there are no measures to mitigate sediment runoff (plan change 6A).

Pool water

Swimming and spa pool water can contain chemicals such as chlorine and copper, which are added to kill harmful bacteria and/or algae. Maintaining the proper chemical balance and filtration in your pool will help reduce the number of times it needs to be drained.

Filtered backwash water must be discharged to the sewer. Cartridge filters should be washed onto the lawn or into the sewer. Spent diatomaceous earth should be disposed of to the rubbish.

Wherever possible, drain pool water to your lawn or garden and make sure the water does not flow off your property.

Private landowners may discharge pool water to the sewer. Please make sure you do not discharge pool water when it's raining. If you need to drain a commercial pool (e.g. motels, schools etc.) please contact our Senior Education and Compliance Officer (477 4000).

Water blasting

Divert water away from stormwater drains. If this is not possible, cover the drains with a filter that will filter out the paint flakes, stones and sediments. Sweep up loosened material and dispose of in the general rubbish. Do not hose down stormwater or wastewater drains.

If you are using chemical cleaners to remove oil, grease or any other contaminant, allow the water to run off into a plugged stormwater sump where it can be removed by a liquid waste contractor.

Wastes from trade or industrial premises

Waste generated from businesses (trade and industrial premises) are addressed by the Trade Waste Bylaw 2008. This includes wastes generated by mobile businesses (e.g. various cleaning services).

The Trade Waste Bylaw controls all non-domestic discharges to the sewer, and sets limits on all discharges to the stormwater system. All wastes generated from trade and industrial premises must be appropriately disposed of. For more information, please contact our Senior Education and Compliance Officer (477 4000).

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