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Stormwater Management – Why is it so Important?

All of the water that flows across the outside surfaces of your premises is channelled into drains and gutters and subsequently finds its way into our creeks, rivers and ocean.

All of the water that flows across the outside surfaces of your premises is channelled into drains and gutters and subsequently finds its way into our creeks, rivers and ocean. This water is untreated and contains pollutants such as, general rubbish, industrial waste, heavy metals and hydrocarbons.

Stormwater should only contain, clean rainwater and there is specific legislation to prevent pollution of our stormwater system such as the Public and Environmental Health Act, the Environment Protection Act and the Local Government Act. The recently developed Environment Protection (Water Quality) Policy 2003 was introduced to help car yards comply and prevent pollution of our waterways.

It is common knowledge that car washing from car yards in high density areas, along main roads for instance, produces large volumes of wastewater. This wastewater can contain a range of pollutants including sediment, rubber, oil and grease, lead and zinc residues and nutrients such as phosphates. These all have a harmful effect on the health of our waterways.

Nutrients from detergents that are washed into the stormwater system contribute to problems such as rampant algal growth which can reduce oxygen availability for aquatic animals and plants and ultimately kill them. Some algal blooms (such as blue-green algae) can also be toxic and a risk to public health. The use of biodegradable phosphate detergents can be beneficial to the environment if the wastewater is directed to the sewage system and the treated effluent re-used to grow plants.

The following table shows the list of pollutants from car washing and their impact on our receiving waterways.

Pollutant type	Impact
Oil & grease (Suspended Solids)	Harm aquatic life mainly by smothering or preventing oxygen transfer to the water. Suspended solids decrease visibility to aquatic organisms and light availability for photosynthetic organisms. Increase sedimentation of the water. Heavy metals and other pollutants attach to the sediment particles, which transport them through waterways, and harm water quality.
Nutrients (nitrogen & phosphorous)	Can cause (along with other factors) algal blooms which harm aquatic life by depleting oxygen in the water and decreasing light penetration for photosynthetic organisms. Promote unwanted weed growth.
Heavy metals Toxic (Cadmium, Chromium Copper, Lead & Zinc)	Can bio-accumulate in aquatic species such as mussels, which can then have an impact all the way through the food chain.

Typical pollutants associated with car washing

Cars for sale need to look presentable and must be cleaned often. The options in these guidelines allow car yard operators to keep cars presentable while minimising pollution of local creeks, rivers and oceans.

Issues

Washing cars using detergents and the wastewater entering the stormwater system.
Car wash bays and degreasing operations not having the correct structures to prevent discharge into the stormwater system.
Engine leaks and spills (e.g. oil, coolant) washing into the stormwater system.

Benefits

By addressing the potential stormwater pollution problems at you car yard you:

Reduce your pollution contribution to our waterways.
Improve the public image of the car sales industry
Increase your compliance with the environmental legislation.
Receive fewer public complaints

What can car yard managers and staff do to prevent pollution of the stormwater system?

Listed below are some options for you to consider to minimise the impact of your business on local waterways.

Options for structural surroundings of the car yard

Some existing sites have difficulty managing wastewater because of their design and the structure of the surrounds. Despite this, all car yards should be able to use at least one of the options given here to maximise the water retention on site or develop an alternative.

Existing sites may not need structural changes if you change washing procedures to ensure that no wastewater leaves the site. New sites should consider the design and structure of the site as well as washing procedures, to ensure that wastewater is minimised and contained on site.

Surround the site with gardened areas that are capable of absorbing the wastewater runoff so that none escapes into the stormwater system.
Surface the site with gravel or another permeable or semi-permeable material that will allow increased infiltration of the wastewater, preventing it from entering the stormwater system. This can also help with oil spills and leaks as the contaminated gravel can be removed and replaced, thus preventing oil residue from entering the system.
Install permeable pavers or cement lattice, with rubble or grass in the open sections of the lattice to retain wastewater on site. Find out if the soil on your site is suitable for this option.
Create a bund around the entire site to help retain all water on site. Ramp style bunds or channels over driveways allow vehicles to enter and leave easily.

Options for washing procedures

Car Yards without a wash bay

Clean car bodies by using a bucket or hose and a chamois. Use a trigger nozzle on the hose to minimise the volume of water generated and the possibility of it leaving the site. Use minimal amounts of water to ensure that no excess water makes its way into the stormwater system. This method will decrease water consumption as well as solve the problem of using detergent. Have cars detailed by a bona fide car detailer (with an appropriate trade waste facility) before they arrive at the yard.
Wash cars on a spill safe mat or other containment device (where practicable). Detergent can be used with this method as long as no wastewater escapes the mat, and that the wastewater contained within the mat, or other device, is disposed of either to an approved trade waste facility or onto a garden bed.
Consider the use of a dust removal product that picks up dust from the car surface without water or chemicals. It may not be practicable for car yards located on exceptionally busy roads where a lot of road grime accumulates.
Clean cars with new products that require only a cloth and the product, and no water.

Car yards with a wash bay

The use of detergents is acceptable provided the wash bay drains to an approved trade waste treatment facility and has appropriate bunding to contain all of the waste so that none escapes into any nearby stormwater drains. Wash bays should also be roofed to prevent rainfall from entering the wash bay.
The treatment facility should be capable of treating all wastewater generated. Check the facility regularly and pump out sludge as required.

Wash bay requirements (SA Water Trade Wastes)

General

Only wastewater complying with SA Water’s standard of acceptance may be discharged to sewer.
Wastewater containing organic solvents may be discharged to sewer if permission from SA Water is granted.
Only quick break detergents/degreasers may be used in conjunction with vehicle washing activities.
Wastewater and chemical solutions, which are not permitted to be discharged to sewer, shall be contained within an approved blind tank and disposed of by a licensed waste disposal contractor. Washing area design All vehicles shall be washed in an area with the following features:
A minimum gradient of 1 in 80 to the drainage point
A bund designed and constructed to:

Pre-treatment

Wastewater from vehicle washing shall drain to a graded channel fitted with weir/s which retain rapidly settling solids and/or perforated screen/s for retaining gross solids.
The channel shall be designed to facilitate cleaning of trapped material.
Where grease/oil exceeds SA Water’s standard of acceptance (e.g. cleaning of chassis or engine bays) the channel shall drain to a pump sump. Wastewater shall then be pumped by a positive displacement pump to an approved above-ground coalescing plate separator, before discharge to sewer.
Where oil/grease is within SA Water’s acceptance limits, (e.g. cleaning of road grime from body exterior) the channel shall drain to an approved suspended solids settling chamber, before discharge to sewer.
Where the pH of the wastewater is likely to be outside SA Water’s limits (pH 6-10), an automatic pH correction system and shut off valve shall be installed.
All cars being washed with detergent must be washed in the wash bay or appropriate washing facility and not in the yard (unless the yard is designed so that no wastewater is discharged from the premises). Cars that require touch ups can be cleaned with a bucket/hose and chamois within the car yard (ensuring that no wastewater escapes from the yard).

Car yard maintenance

The car yard should be maintained and kept clean to minimise the impact of surface runoff into the stormwater system. Cleaning methods also have the potential to impact on the stormwater system. Hosing down the yard is an unacceptable method of cleaning; it will increase the amount of pollutants taken into the stormwater system. Vacuum sweeping or dry sweeping with brooms are the preferred method of cleaning. If blowers or brooms are used, sweepings should be directed into a pile to be collected and placed on a garden or into a bin.

Spills

Any spills such as oil or radiator leaks should be cleaned up by using absorbent materials or, if it is on a gravel or rubble type of surface, the affected area can be removed and replaced. The material can then be disposed of into a container and placed into a bin. This will minimise the amount of residual oil and other materials being washed into the stormwater system.

Stormwater as a valuable resource

As we know South Australia is the driest state on the driest continent, so it is imperative that we try to conserve whatever water we do have. It doesn’t matter what type of setup the car yard has, minimising the amount of water used in the washing process will save you money and conserve water. It may also ensure that you are not discharging anything from your site, thereby complying with the current legislation. Water usage can be minimised by the use of a low pressure water nozzle, dry cleaning, or a bucket and a chamois. Stormwater is a valuable resource that is generally wasted. The installation of rainwater tanks and/or the implementation of a re-use or re-cycling system can be used to not only conserve water but to save money spent on mains water.

For further information

Please contact the stormwater pollution prevention officer at your local council, SA Water Trade Wastes Section (phone 8207 1350), the Environment Protection Agency (phone 8204 2000), your Catchment Water Management Board, or John Nelson at the MTA (phone 8291 2016)

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