Permeable Pavers Protect Water Quality

Demonstrating Water Absorbtion of Pavers Stormwater management is an urban logistical requirement. Rainwater and the water from melting snow have to be dealt with. When plants and soil, which absorb water from rain and snow are replaced with buildings, roads, and other impervious materials, the water from a storm no longer goes into the ground where it can recharge the water table, but stays on the surface and has to be managed in some fashion to keep the streets and buildings from flooding. Low water tables lead to water shortages and increased costs for water supply. However, much of the stormwater that falls on towns and cities is treated as a waste material to be gotten rid of, rather than as a resource for the community and the region.  Water conservation is certainly one part of protecting our water supply.  But  stormwater is another part of the hydrological cycle , and better management of  that water can contribute significantly to improving water quality and decreasing resource consumption.
Some communities still even combine stormwater and sanitary waste into the same sewers, adding enormous load to their water treatment systems by requiring billions of gallons of relatively clean water to be processed. This consumes resources in terms of the energy and materials used in processing that water, as well as the infrastructure required (in terms of pipes and treatment plants) for that greater level of demand. Communities with combined storm and sanitary sewers are also at risk of raw sewage discharges, when the rate of water coming in is too great for the processing plants to be able to handle, the excess is simply discharged directly, without any treatment at all. Even where communities have separate sanitary and stormwater sewers, the stormwater is usually discharged to a nearby body of water, a lake or river where it washes dirt, oil and other debris from the surface into that body of water.

Pervious concrete sample On the other hand, when stormwater is allowed to infiltrate back into the ground, it is cleaned and treated naturally by percolating through the soil. Both permeable pavers, which are hard surface units typically made of concrete, and pervious concrete, which is a special mix of concrete with open pores that allows water to readily flow through it, will allow stormwater even from a heavy downpour to travel into the ground where it will be cleaned as it recharges the water table.

Chicago’s U.S. Cellular Field, the home of the Chicago White Sox, is also now home to the largest installation of permeable pavers in the country. A parking lot the size of four and a half football fields has been covered with pavers, instead of asphalt or concrete. The joints between the pavers allow stormwater to seep directly into the ground, rather than needing to be collected with drains and underground pipes. Permeable pavers and pervious concrete let the water directly into the ground, and the slow uptake of water across the entire surface is adequate to absorb the water from even the heaviest storms.

In addition to being better for the environment, the permeable pavers also saved money for the owner.

The ISFA ( Illinois Sports Facilities Authority, the project developer and owner) achieved a $400,000 cost savings compared with what it would have cost to install and maintain traditional asphalt paving, Royse said.

Not only does installation and maintenance of permeable pavement typically cost less than it would for poured-in-place concrete and bituminous asphalt, but it is highly durable and stronger that those materials and it lasts twice as long as traditional paving, according to an ISFA press statement.

It’s hard to argue with the combination of better for the environment and less expensive for the owner. While the pavers themselves might be more expensive than installing asphalt, the owner saves money by not needing to put in drains and pipes that would otherwise be needed to handle the stormwater. That avoids a lot of labor cost and material use. Furthermore, the light colored pavers help reduce the urban heat island effect by reflecting more solar energy rather than absorbing it where it becomes heat.

via: Medill Reports