L.C.
I'm going to recommend another idea - permeable pavers. Where asphalt causes water to runoff into the storm drainage system and then our drinking water, permeable pavers allow water to seep through and be absorbed into your ground, thus filtering the water. Also, asphalt is dark and absorbs more heat, adding to global warming and heat around your house. Permeable pavers are lighter colored and reflect light - better for keeping your house cool and saving you money on a/c.
Here is some information: http://www.paversearch.com/permeable-pavers-introduction.htm
Just thought I'd give you food for thought.