Wal-Mart gets a lot of bad press. But lost in those stories is the positive impact the innovative retail giant has had on consumers and the competitive landscape it has encouraged.
Well known for breakthroughs in supply-chain management, information technology and low pricing, Wal-Mart has taken the lead in another area: sustainable construction. The Wal-Mart in McKinney, Texas, is the first of two experimental stores where the world's biggest retailer is showcasing sustainable building technologies and testing the results.
When you view the store in McKinney, you immediately notice the wind turbines, solar panels and vast green spaces. However, what you don't see is sometimes more important than what you do. For example, pervious concrete, heat islands and storm-water management aren't as glitzy as windmills, but they are proving to be cost-effective.
The use of pervious concrete isn't new. It's been applied in some parts of the U.S. for 20 years to solve storm-water problems. But the technique is now growing in popularity. The paving material, which resembles a Rice Krispies treat in composition, lets water percolate through the pavement into the ground or into a stone-filled storage area. In either case, the first-flush runoff issues are significantly reduced or eliminated. And, as it is a concrete material, heat island benefits are also achieved.
While pervious concrete parking areas are more expensive than traditional paving, in many cases retention ponds and storm-water piping needs can be eliminated. As a result, the overall cost can be mitigated. It goes without saying that local codes and regulations come into effect, and you may need to have your geotechnical engineer work with local authorities to attain these benefits. As time goes by, more and more states, cities and local code authorities are changing their statutes to make this easier.
NASA has done myriads of studies to prove the existence and effect of heat islands. Here's how they work: When land is developed and the natural foliage is removed, plants don't evaporate (transpiration) and provide a cooling effect. Combine that with the abundant use of dark materials such as petroleum-based pavements and roofing materials, and the problem is exacerbated. This creates a dome of warm air over an urban environment that impacts the local climate. The subsequent increase in ozone levels in the air causes more energy to be consumed in cooling the buildings. Heat islands are a significant and growing issue in all industrialized countries.
The heat island effect can be managed by making small design choices, which have long-term effects. By using light-colored roofing materials and light-colored concrete parking areas, streets and roads, you can dramatically reduce heat island issues. The NASA Web site, www.nasa.gov, features pictures that show concrete being significantly cooler than asphalt pavements. It's easy to understand why. Dark colors absorb heat and light colors reflect it. However, we continue to build with dark-colored materials.
In the majority of the cases I have seen, the light-colored concrete parking areas and roads actually pay for themselves thanks to reduced maintenance and lower life cycle costs. While asphalt can cost less during construction, the total cost of ownership is generally higher. It reinforces the old adage, “it takes money to make money.” You have to spend a little more up front to get the big savings later. Hopefully, we will soon see more people making the decision based on their wallets as well as the environmental benefit. The Wal-Mart in McKinney uses light-colored roofing and concrete pavements for the ability to combat the heat island effect.
When we create an environment, we add impermeable surfaces — buildings, roads and parking; they all create a “first flush” runoff when it rains. If you have a grassy field, some percentage of the rainwater is absorbed and does not run off. The absorbed water gets filtered by the soil and ends up recharging the aquifers where we get our drinking water. The runoff from the built environment is generally channeled through storm-water pipes, ditches or channels and rapidly raises the level of creeks, streams, rivers and lakes, sometimes causing flooding.
Storm-water concerns have prompted Wal-Mart to do a number of things at its McKinney store: utilize landscapes designed as water filters, apply pervious concrete, incorporate numerous green spaces, a unique dual retention pond system and numerous other actions were taken to address storm-water concerns. One technology that garnered significant interest during building tours and by the media was the pervious concrete area. When the tour group saw a five-gallon bucket of water immediately absorbed by the pervious concrete it caught everyone's attention.
Wal-Mart is calling the McKinney center and an upcoming store in Aurora, Colo., (suburban Denver) “experimental.” It has committed to sharing the results of the innovations with anyone who asks. This means that all retailers will have the opportunity to get an insight into the effects of implementing sustainable initiatives into their building programs. Sustainable construction is good for everyone. All you have to do is look at the gas pump the next time you fill up to see why.
Vance Pool is national resource director of Silver Spring, Md.-based trade group National Ready Mixed Concrete Association.