Impervious-Pervious Demonstration Project by John Shepard

This parking lot and the cement ponds it drains into at the University of Minnesota's Landscape Arboretum in Chanhassen, Minnesota, are more than what meets the eye. The lot has been created as a demonstation project that shows how different approaches to design impact runoff pollution. Whenever it rains, "impervious" surfaces such as asphalt and cement don't allow water to seep into the ground. The right-most section of the lot demonstrates an approach with maximum impervious surface. During rains the cement pond in front of this part of the parking lot fills the fastest with water that carries dripped oil, gas, and other pollution from the cars using the lot. The next area, to the left, has grass buffers on the slope above the parking area and between the lot and its cement pond. The grass helps to absorb some of the polluted surface water. The impervious area in the middle has been reduced in size by a berm area at the far side and it has plantings between the lot and the pond. The next area has a larger impervious area, but two sunken drains running across the slope catch water flowing over the asphalt and allow it to seep into the ground. Finally, the area at far left has been covered with stone pavers that have gravel-filled spaces between them so that water seeps immediately into the ground. In accordance with these designs the cement ponds (which were been drained when the photo was taken) collect less water, less sediment, and less pollution moving from right to left. The project has been developed by by Minnehaha Creek Watershed District, Metropolitan Council, and Borgert Concrete Products.