Although new to Iowa the concept of porous asphalt has been around since the late 60s. Its time has come! Due to Phase II of the federal regulations, National Permit Discharge Elimination System (NPDES) there are over 40 Iowa communities that are struggling with how to improve water quality. Although a complex issue, the current direction to meet these regulations is to greatly reduce the runoff generated by hard surfaces in urbanizing areas. One solution is found within the asphalt industry and porous asphalt pavement.

A typical porous asphalt pavement consists of porous asphalt course, a top filter course, a reservoir course (designed for runoff detention frost penetration and structural capacity), an optional bottom filter course, filter fabric, and existing soil or subgrade material. A properly designed porous asphalt pavement under the right conditions prevents storm water runoff problems for as the rain or water (it could be a car lot washing their cars) hits the pavement it drains into the underground reservoir. The reservoir is sized for a given storm event everything above that is released at a pre-determined rate, typically the post 100 year storm released at the pre 5 year storm rate.

While Iowa hasn’t installed porous asphalt on a large scale, the Iowa Heartland Resource Conservation and Development (RC&D) in Ankeny worked with Grimes Asphalt and the Metro Waste Authority in Des Moines to lay a porous asphalt trail trial near a wetland area at the Household Hazardous Waste Collection site in Bondurant. In order to gain “traction” and increase the use of porous asphalt in the state, the Asphalt Paving Association of Iowa in partnership with the National Asphalt Pavement Association is hosting a Porous Pavement workshop on October 11, 2005 in Cedar Rapids, Iowa.

Similar to the workshop held in Kansas City, MO late last year this will be an in-depth look at the challenges, opportunities and design criteria associated with porous asphalt use as it relates to preventing storm water runoff and improving the quality of water in Iowa. This is a tremendous learning opportunity that may lead to increased business opportunities for those in Iowa’s asphalt industry. We hope to see you there!