Erosion and Sediment Management
What do you need to know about erosion and sediment?
Run-off from your site travels via the gutters and drains to local creeks or canals and eventually ends up in a river or harbour or on a beach. If it is contaminated it can kill fish and other water life and seriously pollute the environment where people swim, fish and play. Keeping it clean is important.
Builders carry out many activities that can pollute stormwater. Allowing stormwater to become polluted is an offence that can result in an on-the-spot fine or other legal proceedings.
Why are sediment and erosion a problem?
Soil contains plant nutrients, minerals, organic matter and seeds. It can also contain pesticides and toxic heavy metals. Building disturbs and loosens soil and can create much dust and debris. These materials are very easily washed into drains and creeks and quickly enter rivers and harbours, unless erosion and sediment controls are used on the building site. Although a single block of land may seem insignificant, the effect of many building blocks is significant. A single building block can lose four truckloads of soil in one storm.
Erosion takes away fertile topsoil that contains plant nutrients, seeds and bulbs. The plants and animals that depended on that soil can no longer survive, and the plants that once grew there cannot regrow because their seeds have gone. Erosion costs you and your clients money because you then have to bring in soil from elsewhere. This also increases the risk of importing weeds. When soil, sand, dust, cement, paint and building debris reach the waterways, they can:
- increase the risk of flooding
- block drains
- spread weeds to bushland
- result in algal blooms
- cause skin irritation for swimmers
- result in unpleasant smells
- smother water plants
- suffocate water animals, including fish
- spoil the look of waterways
- reduce fish breeding
- lower the quality of drinking water.
Anyone allowing material to enter a waterway or even leaving the material where it can be washed off-site can expect an on-the-spot fine or prosecution. Everyone on the site is responsible. So save money â€“ yours and your clients'â€“ and stop site erosion.
Prepare a soil and water management plan
- The first step in controlling erosion and sedimentation is to prepare a soil and water management plan (SWMP), sometimes called an erosion and sediment control plan. It's a good idea to submit an SWMP with every development or demolition application.
- An SWMP shows how you will minimise erosion and trap sediment. Many councils will have sample or standard plans that you can use to draw up your own. The plan will tell everyone on your site where to place erosion and sediment controls, how to maintain them, where materials can be placed, how to dispose of waste, and where to wash equipment, among other things. A diagram of the site and instructions on how to construct control measures that are capable of managing the expected stormwater flows and pollutant loads are essential parts of the plan.
Erosion and sediment controls
You should take into account the following points when developing your SWMP and when building. These control measures are considered the minimum protection necessary for a building site.
- Install erosion and sediment controls before work starts.
- Leave as much vegetation as possible.
- Install temporary fences to define 'no go' areas in those areas that are not to be disturbed. Include the area under the canopy of trees so that tree roots will not be damaged by soil compaction.
- Divert run-off from upslope away from the site, but ensure that you do not flood your neighbours. For example, dig drainage channels (catch drains sized to accommodate the upslope catchment).
- Install sediment controls downslope of the site to catch sediment.
- Check the erosion and sediment controls every day and keep them in good condition.
- Leave or lay a kerbside turf strip (for example, the nature strip) to slow the speed of water flows and to trap sediment.
- Limit vehicle entry and exit to one point, and lay geotextile and blue metal to stabilise it for all-weather access.
- Clearly mark the access point and give an access map to all suppliers.
- Protect all drains with a gravel sausage made from geotextile filled with blue metal.
- Save the topsoil and stockpile it for use later in revegetation. Never place it around trees as this will kill them.
- Store all stockpiles and building materials behind sediment fences. Cover them with plastic to prevent erosion by wind.
- Get council approval before placing stockpiles or other materials on the nature strip or footpath.
- Connect downpipes from the guttering to the stormwater drain as soon as the roof goes on.
- Build a dam below the area used for cutting tiles, concrete and bricks.
- Surround the wash-out area with a sediment fence that slows down the water flow. Site this area upslope of another sediment control.
- Fill in all trenches immediately after services have been laid.
- Spread the topsoil back when the work is finished and revegetate the site as soon as possible to control erosion.
- Remove the sediment and erosion controls only after this is done.
- Sweep the road and footpath every day. Washing down is unacceptable.
- Never place any materials in the gutter or on the road. You will be fined for this.
- Filter or settle-out all water pumped off the site. The water must be clear before it enters the stormwater system or creeks. Gypsum can be applied to
muddy (turbid) water to help clay particles settle.
- Your local council
- Department of Lands, Tel: (02) 9228 6666
- DECC Environment Line, Tel: 131 555
- Housing Industry Association, Tel: (02) 6245 1300. Ask for a copy of the
Guidelines for Soil and Sediment Control
- Yellow Pages â€“ look under 'Soil Stabilisation'
Page last updated: 27 February 2011