The city of Lenexa constructed a porous asphalt parking lot at the Coon Creek Trailhead near K-7 off of Prairie Star Parkway. Porous asphalt allows water to seep through it. The water goes down into a layer of aggregate underneath the parking lot and then soaks into the soil below. This porous pavement parking lot is designed to treat and hold runoff from a storm event with 1.37 inches of rain that falls on the lot itself and on the approach road to the lot, which is approximately 200 feet long and not pervious. Excess runoff (storms with greater than the "water quality storm event" of 1.37 inches) is released into a drain system. The city of Lenexa is monitoring the quantity and quality of runoff from this BMP to see if it significantly reduces stormwter runoff so that porous asphalt may become a regional BMP.
City of Lenexa fact sheet
Johnson County Stormwater