Consulting-Specifying Engineer - December 2007 - (Page 10) In The News NEWS AND TRENDS A trip to a greener Windy City leads through the city’s alleyways The city of Chicago and the Chicago Dept. of Transportation (CDOT) will attempt to green an area of the city longer than the distance from Chicago to Las Vegas. The development of the new Green Alley Project includes three main initiatives: the repaving of Chicago’s 1,900 miles of alleyways with permeable pavement, the use of high albedo pavement in sidewalks, and the use of energy-efficient dark sky lighting. The repaving of alleys with permeable pavement will help water trickle down into the purifying aquifer and help recharge the city’s groundwater system. The high albedo pavement will reflect the sun’s heat during the summer months and reduce smog levels and the heat island effect. Finally, the implementation of energy-efficient dark sky lighting for streetlamps, which focuses light downward rather than a 360-degree sphere, will reduce light pollution within the city’s limits. ing. The lower temperatures and improved air quality will eventually reduce the strain on a building’s HVAC system and help lower cooling costs, especially during the warmer months. In Europe, the acceptance of the more advanced photocatalysts or titanium dioxide concrete represents the future for the high albedo concrete in the city of Chicago. The titanium dioxide reacts with sunlight and absorbs UV light. Through the absorption of the UV light, the process enables a catalytic reaction to take place. The reaction destroys common pollutants from vehicle emissions, smog, and the heat island effect. In Chicago, the source of water remains Lake Michigan, but the source is not limitless and the search for more sustainable water and plumbing systems continues. The depletion of groundwater systems can lead to the addition of groundwater replenishment systems, similar to the systems in California, Colorado, and Florida, which purify sewer water to help replenThe new Green Alley Project includes three ish lowered levels of main initiatives: the repaving of Chicago’s groundwater. Greater 1,900 miles of alleyways with permeable acceptance and an pavement, the use of high albedo pavement expanded use of perin sidewalks, and the use of energy-efficient meable pavement in dark sky lighting. Chicago will result in a recharging of groundS t o r m w a t e r m a n a g e m e n t , a water systems and may result in a wide reduced smog effect, and an elimina- scale redesign of plumbing and a more tion of flooding in the alleyways will sustainable water system. be some of the effects in the early CDOT collaborated with S.T.A.T.E. stages of the Green Alley Project. Testing LLC, to oversee the concrete Chicago’s commitment to the advance- quality and control aspect of the ment of green technology will help Green Alley Project. Both CDOT and expand the uses and effects of these S.T.A.T.E Testing have discussed the technologies in the future. The high benefits and future possibilities of albedo pavement used in the side- such green technologies. walks will lower temperatures and Jay Behnke, PE, president of reduce smog, resulting in an improved S.T.A.T.E. Testing said, “There has yet outdoor air quality around the build- to be any talks of using the high albe- The green alleys of Chicago easily are identified. Green alleys will have plaques stamped into both ends that say “City of Chicago: Green Alley, Richard M. Daley, Mayor.” Source: Chicago Dept. of Transportation. do concrete in driveways and parking lots in subdivisions and office buildings. The strength has increased, the technology is advancing, and the cost is going down; there is no foreseeable reason why driveways and sidewalks all over the Chicagoland area should not be using this technology.” Behnke said the expanded use of these green technologies would influence the future of conceptual design and USGBC LEED certification processes. The age of the construction of megahigh rises should usher in new LEED standards. The inclusion of permeable pavement and high albedo concrete in the construction of the parking lots, sidewalks, and foundations should factor into the green building equation. By Patrick Lynch, Editorial Intern 10 Consulting-Specifying Engineer • DECEMBER 2007
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