Landscape Contractor / Design Build Maintain

AUG 2012

LC/DBM provides landscape contractors with Educational, Imaginative and Practical information about their business, their employees, their machines and their projects.

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Going Permeable Staff Report Permeable Grade C ompared to non-porous hardscapes, the porous surfacing niche is expanding. Permeable surfacing, which can come in a number of sub- groups (ranging from porous to permeable and pervious), is becoming more popular, as both an effective storm-water mitigation method, a rainwater collection gateway, as well as a way for companies to earn LEED points. City governments and municipalities are embracing it, as are homeowners looking to address run-off or flooding issues, as well as those who are investing in rainwater capture systems. Essentially, this type of surfacing allows water to penetrate the ground and recharge the water table, rather than sending runoff through a city drainage system. Some permeable surfacing applica- tions are laid over a gravel sub-base that allows the movement of wa- ter through it. In other applications, such as grid systems, water is allowed to seep through organic material, typically grass. In addition to reducing runoff, this gravel base effectively traps suspended solids and filters water pollutants. Water can be allowed to seep into the ground, or with a water collection system added, it can be used to capture rainwater for use in future irrigation or gray- water applications. Water captured in this fashion is usually not subject to city irriga- tion restrictions. Porous solutions can be based on: porous asphalt 20 LC DBM Top: The pathway features a 190-foot elevation change. To address this and to ensure an adequate base in the steepest areas, DeBest installed a grid system that they pinned onto the hill; this allowed the pavement to lock onto it, preventing any future movement. and concrete surfaces, concrete pavers (permeable interlocking con- crete paving systems - PICP), or polymer-based grass pavers, grids and geo-cells. Porous pavements and concrete pavers (actually the voids between them) enable storm water to drain through a stone base layer for on-site infiltration and filtering. Polymer-based grass grid or cellular paver systems provide load bearing reinforcement for surfaces that are subjected to heavy loads, such as parking lots or even patio areas. Grass pavers, plastic turf reinforcing grids (PTRG), and geo-cells (cellular confinement systems) are honeycombed 3D grid-cellular systems, made of thin-walled HDPE plastic or other polymer ma- terials. These provide grass reinforcement, ground stabilization and gravel retention. The 3D structure reinforces infill and transfers sur-

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