Info for building & construction activities
Stormwater pollution prevention for building and construction activities
Activities undertaken in the building and construction industry have the potential for significant stormwater pollution and impacts to receiving waters. The stormwater drainage network is separate from the sewage system. It drains from the gutters and pipe network into our natural water bodies (creeks, rivers, groundwater, wetlands and the sea). If not managed appropriately, stormwater generally flows with pollutants, including those from building and construction activities, untreated into natural water bodies.
As with all stormwater pollution, it is this cumulative impact that causes significant environmental degradation.
Construction activities disturb soil. Once disturbed it is easily eroded and moved off the site into the stormwater drains, becoming a major source of sediment pollution in waterways, and ultimately the sea.
Studies have shown that sediment from an area under building and construction development, may be 5-20 times greater than sediment pollution in an already developed area. (Landcom NSW Blue book p. 6-2).
While the principle pollutant is sediment, there are many other pollutants that may also be generated on building sites and activities such as concreting, plastering and painting which must be managed to prevent impacts to our waterways and oceans.
The Environment Protection (Water Quality) Policy specifies that a number of pollutants cannot be discharged to the stormwater system or onto land where they may enter stormwater. By law you are obliged to ensure these pollutants do not reach the stormwater system from your site. Those pollutants most relevant to the building and construction industry include:
- brick, bitumen or concrete cutting wastewater
- building washwater
- washdown water from cleaning vehicles or equipment
- high pressure water blasting waste
- building construction or demolition waste
- concrete waste
- roof cleaning waste
- paint and paint scrapings, painting washwater, paint stripping waste, stain or varnish
- plaster, plaster waste and plaster wastewater
- solvents, stain or varnish
- soil, clay, gravel or sand
- rubbish, hard waste.
To fulfil the obligations of the Water Quality Policy and ensure these pollutants do not move off site, it is strongly recommended that all building or construction sites undertake erosion, sediment and drainage control management practices.
The Code of practice for the building and construction industry requires that a soil erosion drainage management plan (SEDMP) must be prepared:
- where there is a high risk of sediment pollution to adjoining lands or receiving waters; or
- if the total area to be disturbed, or left disturbed, at any one time exceeds 0.5 ha.
This code is linked to the Water Quality Policy and designed to assist in the compliance with the general environmental duty. The requirements outlined in the code are enforceable by the issuing of an EPO under section 93 of the Environment Protection Act 1993. Failure to comply with an order is a breach of the Act and constitutes a criminal offence.
Erosion is the detachment of soil particles through the action of water or wind at a rate greater than the soil forming process. The soil is transported by water (or wind) and deposited in a process known as sedimentation. During the building and construction process there is a very high risk of sediment moving off site through these processes and sediment pollution in stormwater is a major cause of environmental degradation in receiving waters.
Erosion and sediment control are considered essential on any building or construction site. There are two distinct practices:
- erosion controls aimed at preventing soil erosion in the first instance
- sediment controls aimed at capturing the soil particles once disturbed through soil erosion.
By minimising soil erosion in the first instance it can reduce the need for sediment controls. It is usually far more cost effective to reduce erosion than use sediment controls.
Principles of erosion and sediment control
Adapted from Best Practice Erosion and Sediment Control, International Erosion Control Association (Australasia) 2008.
1. Ensure erosion, sediment and other pollutant control is considered in the planning phase of the development
By incorporating erosion and sediment in the planning phase it will identify high-risk construction activities and areas of the site. This allows for appropriate management and timing when these high-risk activities are undertaken to minimise the risk. Consider the physical constraints of the site and plan erosion and sediment control before construction activities begin.
2. Develop a soil erosion drainage management plan (SEDMP) based on the soil conditions, likely weather and construction conditions
An SEDMP must be considered a dynamic plan that adapts to varying site conditions and the construction activities being undertaken at a given point in time. It must include responsibilities, inspection, review and assessment, and modified should controls prove to be ineffective.
Review the SEDMP according to the changing site conditions and update it accordingly. Remember it is a dynamic plan that needs to adapt.
3. Minimise soil erosion
- Avoiding soil disturbance. All activities should be timed and staged to minimise the time and extent where soil is exposed to water and wind.
- Controlling water movement into and around the site. Reasonable and practical measures must be taken to ensure that all runoff upstream of the site is diverted around the site. This ensures only the water falling on the site requires management. Within the site water should be diverted around areas where soil has been disturbed and flow velocities minimised.
- Stabilising all disturbed areas as quickly as possible.
4. Use sediment capture controls and retain soil and other pollutants on the site
These controls must be appropriate to the soil and weather conditions. However sediment controls should never be the sole means of minimise pollution and secondary to minimising erosion.
5. Inspect and maintain all controls regularly
This is essential to ensuring they maintain the functional design and refers to both erosion and sediment controls.
There are a number of resources available to building and construction managers outlining erosion control and sediment control techniques. It should be emphasised that no two sites are the same and the techniques used on any site may vary to those used at another location.
- EPA 2010 Handbook for pollution avoidance on building sites 2nd Edition
- KESAB Clean sites How to do it right
- International Erosion Control Association (Australasia) 2008 Best Practice Erosion and Sediment Control
- Catchments & Creeks 2012 Erosion and Sediment Control A Field Guide for Construction Managers Version 5
- Catchments & Creeks 2013 Erosion and Sediment Control A Field Guide for Builders Version 3
- Catchments & Creeks 2012 Principles of Construction Site Erosion and Sediment Control Version 1
- Landcom 2004 Managing Urban Stormwater: Soils and Construction Volume 1, 4th Edition (the Blue Book)