Environmentally Friendly Paving

Green building is finally gaining momentum, especially in DC! They are retro-fitting existing buildings with green technology and even going for LEED certification in new buildings. (Of course, I haven’t seen any advertisements for green features in the hundreds of new, over-priced luxury condos around DC, but it’s a start!)

While meditating on two projects close to my heart, the new School of International Service building at American University, and the new Nationals Baseball Park, I began to wonder why green building is making such advances, while green pavement still has not caught on.

Pavement, asphalt, black top, concrete: all are bad news for our planet. Surfaces paved with traditional asphalt and concrete are impermeable to water. Any rain that falls onto this kind of pavement does not percolate down into the ground, but rather runs over the pavement and into down storm drains. On the way it picks up litter, pesticides, and toxic heavy metals from the tires that run over it all day. All of this bad stuff ends up in our waterways, and even drinking water. In case you thought otherwise, stormwater that runs through a “modern,” separated municipal system is not treated before it enters our lakes and streams. Stormwater coming from a system that operates combined sewer overflows is treated, but during a high-volume even can be even worse for the environment and human health, as it releases raw sewage into our streams and waterways with the stormwater.* EPA calculates that in the United States, stormwater runoff from residential, commercial, and industrial areas is responsible for 21% of impaired lakes and 45% of impaired estuaries. In the Mid-Atlantic region alone, stormwater is responsible for over 4,000 miles of impaired streams.

Not only does stormwater pollute ponds and creeks (and eventually major rivers and the oceans), but it also disturbs the local water cycle. When the water runs directly from the pavement to streams, local flora and fauna are deprived of this vital resource. Furthermore, areas with many acres under pavement, such as cities, can greatly affect the water table beneath them, depriving humans of necessary water.

What, you may ask, is the solution? On the market right now are pavements that allow water to pass through them. In fact, porous pavement has been around since the 1970’s, although it still isn’t widely used. This kind of pavement solves many of the problems caused by traditional pavement. Litter remains on the street to be picked up, instead of in streams where it can hurt wildlife. The water percolates naturally through the soil, which filters out most of the heavy metals, chemicals, and bacteria. Porous pavement helps prevent environmental degradation by acid rain, because the soil is a natural buffer, and neutralizes almost all of the acid. Water naturally enters the water table, giving plants, animals, and even humans more reliable access to water. And, best part of all, no puddles!

Porous concretes and asphalts look almost identical to their impermeable counterparts, and are cheaper to install for most construction projects. This is because although the porous material itself is slightly more expensive, it does not require the costly drain and sewer infrastructure of traditional pavement. Many studies have also found that the porous pavement wears better than traditional pavements, and needs to be replaced less often.

So, with all this new information in mind, why haven’t porous pavements caught on? I suspect it is because of ignorance of stormwater problems and their solution. You can do your part by being an advocate of porous pavements in your community. For more information, visit http://www.stormcon.com/sw_0305_porous.html.

* More than 27 billion gallons of raw sewage and polluted stormwater discharge out of 460 combined sewage overflows (“CSOs”) into New York Harbor each year. Scary? That’s just New York . . . CSOs are a major problem for water quality. While it may seem unbelievable that in this day and age raw sewage is still discharged into rivers, about 40 million people live in cities with combined sewer systems, and CSOs are a major water pollution concern for 772 cities. CSOs annually result in an estimated 850 billion gallons of untreated wastewater and stormwater being discharged into U.S. waterways. (See the EPA’s CSO report here.) According to the DC Water and Sewer Authority, 2,489 million gallons of raw sewage and stormwater are discharged annually from the District of Columbia. (More about DC WASA and combined sewer overflow here.)