With a very wet summer predicted for many parts of South Africa, the increased use of pervious concrete and concrete block paving in urban roads and parking areas could play a major role in reducing toxicity in the country’s water resources.

Toxic elements in water

According to Bryan Perrie, CEO of Cement and Concrete SA (CCSA), pervious concrete ground surfaces allow rain, municipal and domestic gardening water, and other water to percolate through to replenish natural aquifers. “Run-off from impervious surfaces, such as asphalt, sends grease and other harmful chemical products into the surrounding rivers, streams and dams while pervious concrete paving naturally filters out pollutants.”

Especially in KwaZulu-Natal, the dangers of toxic elements forming part of flooding run-off have been shown on several occasions, with various beaches closed due to dangerous discharge and spillage from inland waters into the ocean.

The issue: Toxic elements end up in water resources via run-offs.

The solution: Pervious concrete helps with water absorption to prevent toxins from entering water resources.

Intensified water legislation

Pervious concrete was first used in the 19th century but is only now receiving renewed interest because of intensified clean water legislation in many countries, with its descriptive advertising slogan: “When it rains, it drains.”

• When water soaks through the sub-base of pervious concrete surfaces, natural filtration takes place to remove pollutants and impurities from the water.
• It can also prevent flash flooding by absorbing water rather than moving it into drainage or allowing it to build up on top of the surface.

Limited municipal budgets

Municipal budgets are extremely limited, so pervious concrete or permeable block paving can be used for stormwater attenuation to replace retention ponds.

Pervious paving has several benefits:

• Reducing the number and size of drainage infrastructure elements, it will save on materials and energy, and reduce future maintenance.
• The prevention of natural drainage of standing water and puddles on large, flat surfaces is difficult to prevent, but permeable paving increases the safety of pedestrians as it dries rapidly.
• Stormwater infiltrating through the ground provides a higher moisture content, but the voids of pervious concrete allow air for roots to breathe and grow into trees and plants.
• In low rainfall areas, pervious concrete can consequently increase the groundwater table.
• It is not strong enough for heavy-traffic pavements, but it has been used with success for low-volume roads, driveways, sidewalks, golf cart paths, retaining walls, slope protection and as French drains.

The proper utilisation of pervious concrete is a recognised best management practice by the United States Environmental Protection Agency (EPA) for providing first-flush pollution control and stormwater management.

For more information, contact the CCSA:
Tel: +27 11 315 0300
Website: www.cemcon-sa.org.za

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