Guide to stormwater management in construction
Stormwater management in construction is critical, with the primary goal in both commercial and DIY projects being to prevent building site by-products from entering stormwater drains.
It is illegal to discharge any pollutants into a stormwater system, that is, anything other than rainwater, so careful site planning is imperative.
Failure to plan can cause costly delays to your project. You are also at risk of fines and prosecution if wastewater or sediment from your site contaminates the environment.
Types of stormwater pollution:
The main stormwater pollutant from a construction site is sediment, caused by soil erosion, wind or water. If not prevented by using control measures, sediment in stormwater can cause major environmental issues.
Site activities and by-product pollutants involving brick, bitumen or concrete cutting washings, soil, clay, concrete waste, sawdust, timber preservative, roof cleaning waste and other activities can also have a negative environmental impact.
Managing stormwater and sediment with drainage controls:
All building and construction sites must observe strict drainage practices, and a plan must be prepared to prevent run-off into the stormwater system.
Divert uncontaminated stormwater away from the work area and into the stormwater system using flow diversion strategies and devices.
Protect sand and soil stockpiles and other materials that may erode with waterproof coverings and ensure waste is contained in covered bins or traps made from geotextile. Ensure building materials are stored away from drainage paths and up-slope of sediment barriers
Wastewater collected onsite – whether from excavations, seepage of groundwater or surface water runoff – must only ever be removed by dewatering, which should be considered in the design stage. It is illegal to divert wastewater to neighbouring sites.
Ultimately, for best management, your planning must include consideration of erosion, sediment and other pollutant controls, as well as drainage management, fit-for-purpose products, and ongoing inspection and maintenance of systems during the entire construction period.
Drainage controls will differ between sites and need to be assessed on a site-by-site basis during the planning stage.
For instance, depending on your state or territory and type of construction, you will need to prepare a detailed soil drain management plan (for erosion and sediment control) and/or a construction and environment management plan (for site contamination and other general waste management).
A variety of products exist on the market which help to prevent erosion of exposed soil, prevent and filter entry of sediment into stormwater channels, and contain and absorb spills and other pollutants.
These include stormwater management products, including drain, curb and gutter guards, pipe socks, concrete filters, fuel mops, sand- and/or gravel-bags, dewatering products, sediment traps and bunds/spill containment systems (ramps, humps or channels made from impervious materials).
Fulfilling your legal obligations:
Eliminating contaminants from entering the stormwater network is vital. Where stormwater is not properly managed, it takes pollutants with it which can be toxic and damaging to the ocean, creeks, rivers and even major drinking supply dams.
While the same basic principles of stormwater management apply nationally, legislation differs slightly in each state and territory. Start by looking for the Environmental Protection Agency (EPA) legislation for your state/territory.