With Councils starting to become more serious about Water Sensitive Urban Design (WSUD) in their areas, selecting the right WSUD measures to treat your project has become paramount. Infiltration swales are cost effective and have excellent WSUD rating results, however they are often inappropriate when the site does not feature sandy soil or when basements occupy a high percentage of the site. This leaves raingardens and tanks.
Rainwater tanks can be very effective for apartment developments but are more limited in their ability to achieve compliant stormwater quality outcomes for townhouses and other medium density developments with a higher percentage of external paving such as driveways and unroofed courtyards. Raingardens are a biofiltration system which can effectively be used to achieve the needed WSUD outcomes, but challenges can arise due to conflicts with the desired landscape design and the levels of the Legal Point of Discharge (LPD) relative to runoff areas.
EcoResults has worked with ESD officers in a variety of Councils to achieve the approval of filtration systems which do not require soil or plants and which require less maintenance than raingardens over time. These pits allow hard surfaces to be treated effectively through 3 specially designed filtration layers. Utilising a modular design and only requiring an average of 15% of the size of a typical raingarden, they save space on site.
Although non-biofiltration systems are not the first preference of the Councils, we often recommend them on sites where raingardens are not appropriate or desirable.