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Porous pavements offer many benefits which are practical and aesthetic. Some of them include reduction of storm-water runoff, controlling the peak rate, increasing groundwater infiltration and recharge, treating water runoff and providing a high out-flowing water quality (Pennsylvania Stormwater Best Management Practices Manual, 2005). To ensure such benefits are realized and maintained, landscape architects need to adopt strategies that guarantee sustainability of the porous pavements. The design of porous pavements depends greatly on the location and funds available, it is therefore imperative for landscape architects to take into consideration these rudiments prior to designing a porous pavement.
To ensure longevity three factors must be taken into consideration irrespective of the design to be used. First and foremost are the location and unique features in the site as they influence the design to be adopted. The second factor entails designing a rigorous and correct structure for the pavement while the last one involves building the structure properly using the most appropriate management practices. These factors provide the steppingstone to ensuring sustainability of the pavement as they influence the design and the cost of the pavement (Pennsylvania Stormwater Best Management Practices Manual, 2005).
Porous pavements are vulnerable to failure during construction hence it is imperative for construction to be undertaken in such a way that the risk is eliminated. The soil beneath the pavement structure should allow water which has accumulated to drain and in addition to that, special attention should be availed to avoid compaction. Moreover, caution should be taken to ensure clogging does not become a problem and this can be achieved by ensuring that debris drain in all directions away for the structure. Drainage of ‘sediment laden waters’ into the constructed bed or onto the porous surface should also be avoided (Pennsylvania Stormwater Best Management Practices Manual, 2005).
What are the key elements in designing porous pavement?
There are several key design elements that should be considered in designing porous pavements. These elements include: a surface with substantial permeability of greater than 8” per hour; a surface and stone bed which is suitable for designing traffic loads; an open-graded sub-base which has a minimum 40% void space; an underlain made from nonwoven geo-textile; level bed bottoms; traffic surfaces should have a slope of less than 5%; protection from sedimentation during the construction process; a line bed with nonwoven geo-textile; avoiding installation on recently placed fill of less than five years; provision of storm-water overflow through outlet structures which are well engineered; allowing three feet buffer between the seasonal high groundwater table and the bed bottom and a two feet buffer for rock; and a non-compacted sub-grade (Pennsylvania Stormwater Best Management Practices Manual, 2005).
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In conclusion, porous pavements are susceptible to failure thereby making it essential to adhere to the key design elements. These elements ensure that the porous pavement are constructed well and work properly. The location and the cost of constructing and maintaining the porous pavement are also important in ensuring sustainability at the site. It is therefore imperative for landscape architects to take into consideration the amount of funds available and the design most appropriate and in addition to that, ensure that the key design elements exist at the site.