One major characteristic of urban areas is that they come with a great deal of concrete and asphalt. The high ratio of engineered building material to green space is the reason why you might have heard the term "heat island." This is what happens when the sun heats up a paved surface and the surface radiates the heat back into the atmosphere. (Think of sitting on a patch of grass versus a patch of pavement on a hot summer’s day). The temperature of the city is higher than the surrounding rural area, making it somewhat of an island in that regard. This increase in urban temperature can combine with urban smog to exacerbate respiratory problems.
Another reason that the concrete jungle creates such a problem is that when it rains, the majority of the water falls onto an impermeable surface. This causes all of the dirt, grease and debris to be washed off of the surface and deposited directly into the sewer. Normally, what would happen on a vegetated surface is that the water would fall onto the vegetation, into the soil, infiltrate as ground water into the water table and then flow underground to an aquifer. In our urban example, there is no delay in the process. The water ends up overflowing the storm basins in periods of high rainfall, increasing demand on the water treatment process.
Did You Know...
The most common cause of pollution of streams, rivers and oceans is caused by surface water running off of yards, city streets, paved lots and farm fields (Higher Education Symposium, Chicago, November 2008).
This is where the idea for "alternative paving" comes into play. There are some methods that allow for an area to have the structure and durability of a paved surface, but still allow water to infiltrate through. A couple of neat ideas from around the world are grass driveways and permeable pavement, both of which are easily Googlable.
What McMaster is doing:
A pilot program took place during the fall of 2009 which incorporated a grass paving system on McMaster's campus. The pilot project is located between parking lot G and the North quad residence buildings.
Two Sustainable Internship opportunities through the Faculty of Engineering are taking place in coordination with this initiative. One student is studying the installation and maintenance of the surface and another student is analyzing the sustainable benefits of this systems relating to air quality and water specifically. Both students will provide recommendation for future application at McMaster.
For more information the "garden grid" grass paving system used, please refer to the following link: Green Innovations
In addition, McMaster University has decreased the paving of bicycle parking. Leaving a green space wherever possible, or placing porous material such as gravel where needed for stability purposes, maintains the amount of campus green space, rainwater infiltration and storm water remediation as well as decreasing the potential for heat island effects.
December 19, 2011