There are a wide range of stormwater treatments and configurations. Before beginning work, do your research so you choose the right stormwater treatments the first time.
Stormwater treatments vary greatly in size, form and treatment process. The best choice of treatment depends on a number of criteria, including stormwater management objectives and the treatment location.
Types of treatments include:
- Single function – require a sequence of treatments, or treatment train, to meet stormwater management objectives; examples include sediment ponds and gross pollutant traps
- Multi-function – can meet management objectives on their own when properly sized and maintained, such as bio-retention systems and wetlands
- Hybrid – use a combination of methods for greater effectiveness; examples include bio-infiltration systems that can also recharge groundwater reserves, and systems with an integrated stormwater harvesting function
More information is on the following pages:
- Stormwater quality objectives
- Outlet and distributed approaches
- Multiple treatments - treatment train
Select and implement treatment measures by following these six steps.
1. Determine treatment objectives
What do you wish to achieve by implementing stormwater treatment measures? Establish the pollutants of concern in the catchment (e.g. litter, sediments and nutrients) and the level of pollutant retention required.
Your aims might include:
- meeting a regulatory requirement
- achieving best practice environmental management (BPEM)
- aligning to Victoria’s State Environmental Protection Policy (SEPP)
- achieving water quality targets
- managing urban hydrology
2. Understand the nature of the catchment
Understand the catchment's characteristics so you can choose the best form of treatment.
Some questions to ask include:
- Is the catchment made up of residential roads and roofs, or are there commercial and industrial areas that will generate higher than normal pollutant loads?
- Will natural features, such as deciduous trees, generate seasonally high organic loads?
- What physical opportunities and constraints exist within the catchment?
- Are there social considerations such as access, amenity or a need for fit-for-purpose water?
- Do the land managers or final asset owners have requirements and guidelines on their preferred type of treatment system?
3. Shortlist suitable treatment measures
Based on your treatment objectives and catchment characteristics, identify the treatment measures you are likely to implement.
Consider the scale(s) at which the treatments can be implemented, and the characteristics of the landscape. For example, wetlands provide adequate treatment and can harvest stormwater, but may be constrained by steep slopes.
4. Determine the optimal treatment measures
Consider which treatment measures will serve you best, taking into account their:
- ease of maintenance
- pollutant retention
- capital and lifecycle costs
- secondary benefits, such as alternate water supply
5. Decide who will manage and maintain the system
Consider the following questions:
- Who will take on management of the systems once complete?
- Is there a maintenance period?
- What handover requirements are there?
6. Develop a detailed design
Develop a design of the stormwater treatment system you intend to implement.
As stormwater treatment measures often combine engineered and vegetated components, an ideal design team should include engineers, landscape architects and scientists. You should also seek input from operational staff.
Opportunities and constraints
Be aware of the opportunities and constraints that affect your site and environment.
Consider the following physical site characteristics when planning your treatments:
- topography – steep slopes
- soils and geology – erosivity, porosity, depth to bedrock or instability
- groundwater – geochemistry and water table depth
- space – limited open space and proximity to underground services such as gas and electricity)
- environmental – significant flora and fauna species, heritage values
Do your best to address social issues during the treatment design stage, especially where innovative or new designs are used. This may involve developing occupational health and safety procedures for operations and maintenance staff, or installing hazard signs and fencing around dangerous areas.
When planning treatments close to recreational facilities, consider:
- odour problems
- visual impacts
- noise if machinery is required to treat or maintain it
- physical injury from unauthorised access
- contamination – infection, poisoning or injury caused by trapped pollutants or algal blooms
- vermin such as mosquitoes and rats
Some of the social opportunities that can arise from stormwater treatments include:
- aesthetic improvements to existing environments due to plantings and wetlands
- water supply – captured stormwater being used within the community
- amenities – improved parkland facilities
- reduction of nuisance flooding
For a fuller appreciation of treatments we recommended investigating other resources, such as the WSUD Engineering Procedures available for purchase from CSIRO publishing.
You should also consider seeking professional advice to take advantage of the latest improvements in treatment design and maximise the benefits for a given location.