June 9, 2011

Cameras flashed and people watched in amazement as water rushed out of a concrete mixer at the rate of 500 inches an hour and was quickly absorbed by the pervious concrete parking lot at the Christian County office of the University of Kentucky Cooperative Extension Servicein Hopkinsville.

Since its completion, the parking lot has served as an educational tool and demonstration site for builders, contractors and the general public to learn about the concrete’s environmental benefits and storing rainwater onsite.

Pervious or porous concrete has been used across the United States for several years but is a relatively new product in Kentucky. It is more environmentally friendly than other forms of pavement because it filters rainwater through the concrete to the water table, while leaving many of the sediments that accompany the rainwater on the surface.

Kelly Jackson, the county’s horticulture extension agent, read about the benefits of pervious concrete in landscaping magazines. When the county’s Extension District Board decided the office needed additional parking space, Jackson and the other Christian County extension agents approached the board about the possibility of using pervious concrete.

“Hopkinsville has a flooding issue,” Jackson said. “Some of the builders found out about what we’re doing and recognized it as a way to save land and reduce the amount of non-pervious taxes they pay.”

The north and south forks of the Little River run through Hopkinsville, which results in flooding problems during major rainfall events. Many of the flood-prone areas require contractors and builders to install retention basins before residential or commercial construction can begin.

“It’s ideal for any situation where you have drainage problems,” said Scott Merrifield, president of Shaw Creek Contracting, who installed the extension office’s parking lot. “It allows you to put in parking without having to install a retention pond and is a better use of land.”

Pervious concrete is more expensive than other forms of concrete. However, when compared to the cost of building a retention basin and the resulting loss of land for future development along with high-storm water fees, it potentially could pay for itself. While the concrete requires yearly maintenance to remove any small debris, it is a minimal cost compared to resurfacing and other maintenance issues associated with other forms of pavement. It can also help builders achieve Leadership in Energy and Environmental Design (LEED) certification.

Finley Messick, executive director of the Kentucky Ready-Mixed Concrete Association has worked with pervious concrete for 11 years. Through his position, he helped the city of Frankfort secure a grant to install the first pervious concrete surface of significant size in the state in Frankfort’s Public Safety Building parking lot. Like the Christian County extension office, the parking lot is also being used as an educational tool.

“Before the pervious concrete was installed, 100 percent of the runoff from that parking lot was going directly into the Kentucky River,” he said. “We took that site down to 0 percent runoff.”

Dennis Smith, president and CEO of DDS Engineering, lead two of the largest pervious concrete projects in the state. His firm designed pervious concrete parking lots at the Green River Regional Educational Cooperative and Western Kentucky University. At both sites, he was able to achieve 0 percent storm water runoff.

“It’s a little different process for contractors to learn, but it’s quicker once you get used to it,” he said. “Pervious concrete will continue to be used more and more as contractors learn that it is economical when you don’t need retention basins and can meet the EPA Clean Water Act requirements.”