Architects and engineers designing large areas of pavement face tough challenges today. New EPA regulations and fees to municipalities cause great concern to property owners and developers. Retention ponds take up valuable real estate. Mechanical skimmers cost money to install and can still break despite required regular maintenance.
Many large paving areas are constructed with asphalt. That’s not good for Mother Nature. When asphalt pavements are used, there is a state of almost total runoff during any precipitation.
Cars sitting on asphalt surfaces become very hot causing automotive fuels to boil over. That means water flowing over the surface picks up more contaminants and returns them to the environment. The heated water also kills wild life, particularly fish in rivers and streams that catch runoff from paved areas.
As a result, valuable water resources are wasted and public water is needed for irrigation. Environmental pollution increases and ecosystems are damaged.
The Answer: Pervious Concrete – The Pavement that Drinks
A type of concrete called pervious concrete can be the answer to this pressing regulatory and environmental land mine. Pervious pavement is a gravel or stone, cement, water and sand. Using little or no sand in this mixture creates an open cell structure that allows storm water to filter through the pavement and into the underlying soils or act as a retention area while helping to protect our environment.
Pervious concrete paving models natural ground cover by filtering water through the surface. Pervious concrete can pass 3 to 5 gallons of water per minute through it’s open cells for each square foot of surface area, which is far greater than most rain events. This system reduces or eliminates storm water runoff and replenishes groundwater.
A pervious concrete system can reduce the need for large retention ponds because the pavement acts as a retention area. The volume of the open cells in a 5-inch thick pervious concrete pavement can retain up to an inch of rainwater before runoff occurs or water is percolated into the soil. Pervious pavement assists in efficient use of land and puts rainwater back into the ground where it belongs. Owners and developers can use expensive land for development and not for ponds that hold water.
A pervious concrete pavement helps to reduce the amount of untreated runoff discharging into storm sewers, rivers, and streams. The open cells provide a media for aerobic bacteria that break down pollutants such as oil and other hydro-carbon liquids that seep from parked cars. This helps to prevent much of the polluted runoff that normally occurs with traditional pavements. According to the US Environmental Protection Agency, 90 percent of pollutants are typically carried by the first 1-1/2 in. of rainfall through traditional horizontal runoff into rivers and streams.
In addition to the light color of pervious pavements, they also contain less thermal capacity due to the open pores in the material. That means they do not absorb and store as much heat as other pavements. That’s helpful in mitigating the heat island effect. Visit the Cool Communities section to find out more about how concrete is helping to save the planet.
Environmental & Financial Advantages
Owners, developers, architects and engineers using pervious concrete can take advantage of important benefits. This product can help satisfy certain EPA drainage and storm water discharge requirements.
When pervious pavement is in place, water resources are conserved. The resulting percolation recharges groundwater and runoff to the environment is cooler and cleaner. Adjacent landscaping receives more water and there is less need for irrigation.
As a result, the money spent on labor, construction, and maintenance of water management facilities such as retention ponds, skimmers, pumps, and irrigation systems can be reduced or eliminated. It can also mean that valuable land normally used for discharge and runoff mitigation can be developed for commercial gain.
While this thirsty pavement is an excellent option for certain situations, it does have certain limitations.
Because of the nature of the surface material, it is not appropriate for heavy truck traffic. It is also important to remember that proper construction techniques are crucial for good performance. Concerns about clogging of porous pavements can be “designed out”, by reducing erosion and sediment runoff through strategic design and water retaining ground cover. Studies indicate that pressure washing a “clogged” porous concrete pavement can restore 80-90% of the permeability. Click HERE for the Pervious Concrete Maintenance Guide.
See some examples of pervious concrete at various locations in the pervious concrete gallery.
Investigate how pervious pavement and other concrete products are part of the Cool Communities program, a global environmental solution.