All Your Questions About Bioretention Systems Answered
Bioretention systems – also called bioswales – are shallow, depressed areas that filter and slow stormwater and runoff. So are they an important element in your property’s commercial landscape? And what role do they play in reducing environmental pollution and managing local water levels? Keep reading for answers to these questions and more.
Q: How does a bioswale remove pollutants from water runoff?
A: Through a physical filtration system, water passes through multiple layers of a bioretention basin. No bio-swale is created equal; the levels of filtration will vary but often consist of flow entry/drainage points, grass buffers, sand beds, ponding zones, vegetation and mulch, engineered soil, storage areas, underdrains, and sand or native soil. As water sieves through each layer, it is collected and treated – including the removal of pollutants and debris – until it reaches the underdrain, and then penetrates native soil or is directed to a discharge point.
Q: What kind of properties most benefit from a bioretention basin?
A: Smaller drainage areas adjacent to runoff sources – such as parking lots or streets – are best suited for bioswales. Placement is also key as the bio basin must be maintained regularly in order to function at the highest level; away from structures and roads but in open, visible areas is ideal. The use of bioretention basins is becoming increasingly more common in new commercial development, as required by changes in city mandates and permitting.
Q: What kind of maintenance does a bioretention system require?
A: Bioretention maintenance is a multifaceted process requiring a group effort from several parties, depending on placement and requirements of the bio basin, but can often include a cooperative effort between city officials, property owners & managers, landscape maintenance providers, and hazardous waste removal companies. Accumulated sediment must be removed regularly, inspections are required semi-annually or annually (sometimes more or less frequently depending on the property), mulch levels must be maintained and replenished, debris cleared frequently, and often de-clogging as drains are susceptible to obstructions. Overflow devices can also be used to prevent an excessive amount of water from collecting in the basin and must be inspected and maintained as needed.
Q: Where does the water go that passes through the system?
A: Depending on where the bioretention basin is located and its system of filtration, runoff that doesn’t evaporate is either discharged to a stable outlet – such as sewers or swales – or absorbed into native soil.
Q: How does a bioretention basin impact environmental preservation?
A: The process of bioretention in itself is eco-friendly as it naturally lends to less water pollution and contamination, and slows and reduces runoff, improving the quality of local water sources, including nearby beaches, lakes, rivers, etc. Bio basins also create habitats for wildlife – including birds and butterflies.