Today, most parking lots, roads, fire lanes, walkways, sidewalks and bike paths use asphalt or concrete when a hard, durable surface is necessary. Both materials work relatively well in such applications, but their impermeable nature leads to runoff problems, flooding, and erosion, plus they are difficult to install, costly and energy-intensive.
Porous pavers, also known as permeable pavers, provide an alternative that is environmentally conscious, easy to install and eliminates many of the drainage problems that are common with asphalt or concrete surfaces. Porous pavers are a system of interlocking plastic grids that are laid over a prepared sub-surface. They are then filled with materials such as washed rock, limestone, crushed glass, sod or a combination of soil and grass seed to create a strong and durable surface that allows water to drain through to the soil below naturally.
Compared to asphalt and concrete, porous pavers are much better for the environment, and here are a few of the features that have earned them that distinction:
#1 They Promote Natural Water Absorption
Much of the drinking water that is harvested throughout the country comes from natural underground aquifers, which are recharged by groundwater that soaks into the soil after a storm. The water is brought to the surface via wells and pumps, then is either used on site or distributed through a municipal water system. If too little groundwater soaks into the soil, over a period of time, the water levels in the aquifer may drop too low to provide a suitable supply for the wells.
Concrete and asphalt surfaces are impermeable, providing a barrier to the natural absorption of water and, often, any runoff collected in their integrated drainage systems is discharged far away from where it originally fell. In places that have a large portion of the land area paved, such as cities or tightly-packed suburban communities, this may disrupt the natural process that recharges the aquifers, requiring new sources of water to be found or deeper wells to be drilled at great expense.
Because porous pavers allow water to drain through to the sub-surface naturally, they prevent no obstacles to the natural recharge of local aquifers. This helps protect the local water supply and eliminates the costly and energy-intensive process of finding new water sources or drilling new wells.
#2 They Help Filter Pollutants
Paved surfaces tend to collect pollutants like oil, fuel, and other automotive chemicals, and when it rains, those pollutants and others from nearby areas are often absorbed into the runoff. With concrete and asphalt surfaces, these pollutants travel with the water through the stormwater drainage system, to either retention tanks or municipal wastewater systems. Before the water can be used for other purposes, it must be filtered and treated to remove pollutants, an expensive and difficult process that may have environmental consequences, depending on the pollutant disposal process.
Porous pavers have a permeable surface that allows the water and pollutants to drain through to the soil below, where gravel, sand, and natural bacteria help to trap and break down the pollutants naturally. The resulting water, now free of the majority of pollutants can then continue on to refill local aquifers. With no external energy expended and no harsh chemicals, this natural treatment process is far better for the environment.
#3 They Are Made From Recycled Materials
Asphalt is made from a combination of petroleum products and natural materials, and concrete is made from sand, aggregate and cement that is expensive and difficult to produce, process and transport. Though many of the materials are natural, they still require large amounts of energy to extract and process them, and large amounts of carbon are emitted during their production and use.
Porous pavers are made from high-density polyethylene, or HDPE, similar to the material used in plastic gasoline cans and many colored plastic food containers. HDPE is a versatile material that is easy to recycle, and it does not leech harmful chemicals, like BPA, into food or water that comes in contact with it. Except for those made in custom colors, porous pavers are made from 100 percent post-consumer recycled HDPE materials. Though energy is required to recycle HDPE and create new products from it, the process minimizes the energy required to extract new materials like petroleum, and it reduces the amount of plastic in the waste stream. And, at the end of their life cycle, porous pavers can be recycled again to create new products.
#4 They Minimize Transportation Costs and Consequences
The raw materials used to create concrete and asphalt are often transported long distances to the production facilities, then the materials are transported again to the job site and installed with heavy equipment. The entire process consumes vast amounts of energy and produces considerable amounts of carbon.
Porous pavers are extremely lightweight, which reduces the costs of shipping them, and the amount of energy used during the process. The sub-surface materials and the fill make up the bulk of the transportation costs, as well as the majority of the energy used during the installation process, and because these materials are obtained locally, energy usage and carbon production is minimized. Because of this, porous pavers require far less energy to install than either concrete or asphalt.
#5 They Can Help Control Erosion
Many of the nutrients needed for growing plants, including food crops, is contained within the top layer of soil. Without proper soil management and cover vegetation, this nutrient-rich layer can be washed away during heavy rains, leaving behind soil that has few nutrients and will require artificial fertilizers and chemicals to become productive again. As the erosion continues and plants start dying off, even more soil can be displaced. In extreme cases, this process can lead to desertification, where all but the hardiest plants die off.
When used as a parking surface, permeable pavers prevent the underlying soil from being washed away during heavy storms, which would cause concrete or asphalt surfaces to buckle or crack. Porous pavers can also be used specifically to combat erosion, by placing them in sensitive areas, like slopes, to cover and weigh down the underlying soil, keeping it in place. This can prevent landslides on hills, and it can keep nutrient-rich soil where it belongs, reducing the use of fertilizers and chemicals that can harm the environment.
In addition to being environmentally friendly, porous pavers are also easy to install, economical, durable and simple to maintain. They are great for any type of project, residential, commercial or industrial.