Permeable Surfaces

Storm water runoff is caused by impervious surfaces (roofs, paving, compacted soil) blocking rain from infiltrating into the ground and replenishing the ground water causing the storm water to drain into the sewers.  In dense urban areas, this problem multiplies and can overwhelm the sewer system creating back ups and flash flooding.  In order to mitigate this issue, it is important to minimize the amount of impervious surfaces in a design and incorporate as much semi-pervious materials as possible.

In the Lofts of Broadway, there was much attention placed on the ground water runoff.  As you can see in the diagram, 32% of the site is covered with pervious or semi-pervious materials (fig 1).  By locating parking under the building roof, using brick pavers and reserving 14.5% of the site for landscaping, we were able to reduce the storm water runoff by 75% during a typical storm (figure 2&3).  This translates to 6,000 cubic feet of less water that has to be piped and treated by the cities sewer system. 

For more information:
http://en.wikipedia.org/wiki/Stormwater_runoff
http://www.duluthstreams.org/stormwater/toolkit/tools.html
http://www.njstormwater.org/tier_A/pdf/NJ_SWBMP_9.7.pdf