Stormwater treatment is an important part of many subdivision, land development and infrastructure projects. As sites are developed, buildings, roads, car parks and other hard surfaces can increase the volume and speed of runoff while also changing the types of contaminants entering the stormwater system.
The right treatment approach depends on the site itself. Available space, ground conditions, drainage connections, development density and council requirements can all influence which solution is most practical.
Considering stormwater treatment early gives the wider design more room to accommodate the system properly rather than trying to fit it into whatever space is left later.
Stormwater treatment can serve several purposes depending on the development.
In some cases, the main focus is improving water quality by reducing sediment, metals or other contaminants before runoff reaches the downstream network. Other projects may need to store stormwater temporarily and release it more slowly to reduce pressure on existing infrastructure.
Some sites require both.
The amount of hard surface being created, the type of activity occurring on the site and the sensitivity of the receiving environment can all influence the level of treatment needed.
This is why the treatment system should respond to the overall development rather than being selected in isolation.
Bioretention uses planted areas and engineered filter media to capture and treat runoff.
Water is directed into the system where it passes through vegetation, soil and filter layers before being discharged or infiltrated. This process can help remove sediment and other contaminants while also slowing the rate at which water leaves the site.
A well-planned bioretention design can work particularly well where treatment can be incorporated into landscaping, road reserves or car park areas.
Space is an important consideration. If bioretention is introduced too late in the design process, there may not be enough room to create a system that works effectively without affecting parking, access or the wider site layout.
Constructed wetlands can provide both stormwater treatment and storage, making them particularly useful for larger catchments and development areas where sufficient land is available.
They work by slowing runoff and allowing sediment and contaminants to be reduced through settling, vegetation and biological processes.
A wetland design may be appropriate for larger subdivisions or infrastructure projects where treatment needs to be provided across a wider area rather than at a single lot.
Because wetlands require space, water level control and ongoing maintenance access, they need to be considered early alongside roads, lots, open space and other infrastructure.
Traditional concrete prevents water from soaking into the ground and instead directs runoff towards drains and pipes.
Porous concrete allows rainfall to pass through the surface into a storage or drainage layer below. Depending on the ground conditions, this water may then infiltrate into the soil or discharge gradually into the wider stormwater system.
Porous concrete design can be useful for areas such as car parks, driveways and accessways where reducing direct surface runoff is beneficial.
Its suitability depends on factors such as soil permeability, groundwater levels, traffic loads and how the surface will be maintained over time.
Not every development has enough room for large surface-based treatment systems.
More constrained sites may require stormwater to be stored or treated below ground, particularly where the available surface area is already needed for buildings, parking or access.
Underground detention and treatment can provide storage and treatment while allowing the surface above to remain usable.
These systems can be particularly useful on commercial or higher-density developments, but they need to be carefully coordinated with underground services, foundations and drainage connections.
Maintenance access is also important. A system that cannot be easily inspected or cleaned may become less effective over time.
There is no single treatment method that works for every site.
The most appropriate solution will usually depend on a combination of:
A large greenfield development may have room for a wetland or larger bioretention system, while a compact commercial site may need to make greater use of underground detention.
Some projects may also combine several treatment methods to achieve the required outcome.
Different parts of a development can produce different levels and types of contaminants.
Runoff from roofs, roads, parking areas and commercial surfaces may therefore require different levels of treatment.
Contaminant load modelling can be used to estimate the amount of contaminants likely to be generated and assess how effectively the proposed treatment system is expected to reduce them.
This can be particularly useful when comparing treatment options or demonstrating how a proposed design responds to water-quality requirements.
Stormwater systems need suitable space, levels and drainage routes.
A treatment area positioned too late in the design process may conflict with buildings, accessways, landscaping or underground infrastructure.
Site levels are equally important. Many treatment systems rely on gravity, so small changes in elevation can affect whether runoff reaches the treatment area and where it can discharge afterwards.
Considering stormwater treatment alongside the wider civil design can help avoid these conflicts and create a more practical overall layout.
Permanent stormwater systems need to continue working after the development is complete.
Vegetation may need to be maintained, sediment removed and underground systems inspected or cleaned. The design should therefore consider how easily each system can be accessed and maintained over time.
Long-term performance is an important part of choosing the right treatment method. A system that is difficult to maintain may become less effective even if it performs well when first installed.
Civix provides stormwater treatment design for subdivision, land development and infrastructure projects.
The appropriate solution depends on the site, the level of treatment required and the wider development layout. By considering stormwater alongside civil, environmental and infrastructure requirements, the treatment strategy can be designed to work as part of the overall project rather than as a separate addition.
Earthworks are often one of the first major stages of a subdivision or land development project. They involve reshaping the existing ground so the site can support buildings, accessways and other future construction.
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Engineering approval is the stage where detailed civil plans are reviewed before construction begins. It is commonly required for subdivisions and developments involving earthworks, roads, accessways, drainage or connections to public infrastructure.
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READ MORE Earthworks can significantly change the way water moves across a development site. Once vegetation is cleared or soil is exposed, rainfall can loosen and carry sediment into stormwater networks, neighbouring properties, streams and other receiving environments.
Flood risk is not always obvious when looking at a property. A site may remain dry in normal conditions but still sit within a flood-prone area or carry significant surface water during heavy rainfall.
READ MORE Stormwater treatment is an important part of many subdivision, land development and infrastructure projects. As sites are developed, buildings, roads, car parks and other hard surfaces can increase the volume and speed of runoff while also changing the types of contaminants entering the stormwater system.
Development usually increases the amount of hard surface on a property. Roofs, driveways, roads and paved areas prevent rainfall from soaking naturally into the ground, which can increase the volume and speed of stormwater runoff.
Earthworks can produce sediment-laden runoff when exposed soil is disturbed by rainfall. Standard erosion and sediment controls are often used to slow this water and allow suspended soil particles to settle before discharge.
For private land developments, Civix Town Planners, Chartered Engineers and Licensed Cadastral Surveyors have got you covered from the initial site visit through to council sign off.
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