Low Impact Stormwater Design
Although man made devices such as filter socks in sumps or proprietory treatment tanks can provide a level of stormwater treatment, nature is equally effective in dealing with contaminants through appropriate plantings in waterways being used to trap and absorb contaminants. Choice of plant species in relation to summer/winter conditions, water velocity and the like are critical to success. Space constraints may preclude a natural or vegetated solution in which case a range of proprietory devices are available off the shelf for particular applications. Staig & Smith are aware of the range of potential treatment processes available and can advise on the most appropriate method or design to achieve improved quality of discharged water.
The nature of in-situ soils, water table and potential offsite effects will dictate whether infiltration can be considered. Infiltration reduces the demand on downstream reticulation and can therefore reduce costs both onsite and offsite.
The smoothing of peak stormwater flows through treatment/infiltration beds, swales and the like may delay the time of concentration and also allow a more gradual release of high flows into downstream reticulation. Again there can be benefits through reduced sizing of downstream reticulation.
By their nature, many of the more natural 'low engineering' treatment solutions allow for landscape planting as an integral component of their operation. Unlike purely aesthetic landscaping there can be a mixture of form and function employed in the design of rain gardens to good effect.