Stormwater runoff from the built environment, often mixed with contaminants, has a damaging effect on local and downstream ecosystems. Porous paving products and vegetated roofing systems result in less rainwater runoff and thereby reduce surface water pollution. Stormwater treatment systems reduce pollutant levels in any water that is released. Again, quantifiable benefit and a strong track record are important determinants here of “green.”
Unilock makes a number of permeable pavers for use in a variety of applications. According to the company, Unilock has installed 12 million square feet of its concrete pavers since 1991. Products include the interlocking Dura-Mat units for erosion control; interlocking L-shaped Eco-Optic that can handle heavy loads; non-interlocking Eco-Stone and interlocking Ecolocfor maximum drainage; Turfstone that supports turf growth in erosion control and parking areas; and the Eco-Priora, which is available in multiple shapes and has improved durability and color retention. Custom colors are available for some models. Unilock also makes traditional and industrial pavers as well as block wall systems.
Porous paving seeks to combine the load-carrying capacity we expect of paved areas with the rainwater-infiltration qualities of natural landscaping.
Porous unit pavers made from concrete are of two main types: a grid of openings that can be planted with grass or filled with gravel, and solid unit pavers. The solid pavers are made of concrete with the “fines” left out so that rainwater can be absorbed more readily.
All porous paving systems must be installed over a carefully engineered subsurface that acts as a reservoir for stormwater. This allows pollutants to break down slowly beneath the paved area instead of contaminating surface water. In addition, solid concrete unit pavers also need to have drainage voids along the installed edges.
In addition to managing stormwater, porous paving systems planted with grass also minimize contributions to the urban heat-island effect while providing visually appealing outdoor space.
When possible, look for recycled content and less portland cement.
Precast concrete unit paver can incorporate fly ash or alternative aggregrates as recycled content, and most products listed by GreenSpec here have at least 20% recycled content.
Consider the use of porous pavers that help manage stormwater runoff, reduce the urban heat island effect, and offer other benefits. GreenSpec includes some porous pavers with lower recycled content due to those environmental benefits.
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