Cleaner Water with Asphalt Pavement? New research says Yes!
Asphalt has been used for decades to waterproof structures because of its ability to keep areas impenetrable by water and other substances. But can we really say that today’s asphalt, made of 5% asphalt cement, a petroleum product, and 95% stone provides cleaner water?
Chemists and engineers respond with a strong YES, as they have conducted many studies on this debatable issue.
Drinking Water. The Metropolitan Water District of Southern California has been using asphalt pavement-lined water reservoirs for more than 40 years. Several other drinking water reservoirs around the country also have thick asphalt liners, including the Devil’s Canyon Reservoir and the East Bay Municipal Utility District, which has been using asphalt liners since the 1950s. Water pipes that supply potable drinking water are also lined with products derived from asphalt binders.
Fish Hatcheries. Newly born fish, which are extremely sensitive to chemicals and contamination, are held in hatcheries lined with asphalt. In 1987, several state fish and wildlife agencies began using asphalt pavements to line their fish rearing ponds. During the delicate stages of incubation, the asphalt pavement allows fish and game experts to closely monitor and control the environment for the fish species. State agencies across the nation are pleased with the effectiveness of the liners and plan to use them for additional fish hatcheries and ponds.
Additionally, asphalt pavement keeps liquid industrial waste material from leaking into the soil below, giving industries time to treat liquid waste, and if needed, provide a platform for moving material to a processing location. Surprisingly, asphalt is often used to line and/or cap hazardous waste sites, preventing rainwater from draining through the hazardous waste and keeping our groundwater safe and clean.
In 1997, the Marine Science Institute (MSI) conducted a study which analyzed runoff water from the pavement. The pollutants found in the stormwater runoff were associated with vehicle emissions, crankcase oil drippings, industrial operations, etc., and not with the pavement itself. Since then, further studies have also proven that stormwater runoff is polluted by the vehicles using the pavements and not the pavements themselves.
Engineers are now using specialized asphalt surfaces including open-graded friction courses (OGFCs) or permeable friction courses (PFCs) to draw water from highways and
runways. These types of surfaces allow rainwater to drain vertically through the asphalt to an underlying layer and then laterally to the edge of the pavement. Studies have shown that these open graded surfaces can improve the quality of runoff water. One study showed reductions in pollutants of up to 90% when comparing highways with open-graded surfaces versus conventional pavements. Additional benefits of the OGFCs include reducing noise pollution from highways and improving visibility by reducing splash and spray from trucks. These factors have contributed to the decrease in the number of vehicle accidents during the rain.
Asphalt pavement, which has been used for over a hundred years in the United States and Europe, is a tried and true road pavement material. For improved drinking water, stormwater management, reduced roadside pollution, asphalt pavement is environmentally beneficial.
Visit our website to learn how we can manage stormwater drainage and contribute to this benefit.