Soon, rain that falls on the concrete courtyards amid the University of Hawai'i's student apartment buildings will sink through the surface and flow into the ground underneath.

In a push toward more environmentally sustainable practices, UH is using pervious concrete to pave some of the walkways and areas around the Hale Wainani and Hale Noelani student housing buildings.

Pervious concrete is designed to let water seep through to the underlying ground, and can reduce storm-water runoff and recharge groundwater supplies. While the product has existed for decades, it is relatively new in Hawai'i. More projects here may follow as interest in environmental practices and new technologies for storm-water management grows.

Last month crews installed pervious concrete in part of 'Ewa Beach Elementary School's parking lot as a demonstration project for the state Department of Education. Grove Farm of Kaua'i also is looking into the technology for a master-planned development.

UH used pervious concrete — believed to be a first on campus — to be more environmentally sustainable, said UH spokesman Gregg Takayama.

"Sustainable practices of all kinds are studied here at UH-Manoa and taught here, and so it's important that we practice it as well," Takayama said.

He said pervious concrete likely will be incorporated as other improvements are done throughout the campus.

The pervious concrete is a mix of 3/8-inch rock with cement and water; no sand is used, said Stephen Baginski, president of Kaikor Construction Co. Inc., contractor for the UH and DOE projects.

"A full 5-gallon bucket (of water) will disappear within seconds," when poured onto the pervious concrete, Baginski said. "It runs through it like there's almost nothing in its path."

Pervious concrete can help address storm-water drainage and runoff problems and could reduce the need for large drainage infrastructure, concrete experts say. It can recharge groundwater, and some projects are also designed to capture the water that drains through for irrigation.

Pervious concrete does have some limitations, however.

It doesn't have the inherent strength of traditional concrete and is recommended for low- to medium-traffic areas such as parking lots, residential roads and walkways rather than highways and truck loading areas.

According to the U.S. Environmental Protection Agency, porous pavement should not be used in areas where activities generate high levels of contaminated runoff, and soil permeability on the site also needs to be considered.

MORE EXPENSIVE

Pervious concrete typically is more expensive than traditional concrete, and experts say it must be designed correctly to keep sediment off, and installed properly.

Baginski said pervious concrete is about 10 percent to 20 percent more expensive than regular concrete and that it's more difficult to work with than regular concrete. Installers have a shorter amount of time in laying down pervious concrete, and the concrete must be covered with plastic sheeting for at least seven days to cure.

But Baginski and others say there are environmental benefits and potential savings with using the porous material, including possible reduced costs associated with drainage structures.

Kaikor Construction began laying down the pervious concrete at UH late last month and conducted a demonstration for several teachers and counselors participating in The Pacific Resource Partnership's "Tools of the Trade" construction internship program.

The company recently used pervious concrete at Hawaiian Waters Adventure Park to pave a small area near the wave pool as a demonstration project, Baginski said.

'EWA BEACH PROJECT

State education department officials also are interested in the technology. The education department's demonstration project, a joint effort with the Cement and Concrete Products Industry of Hawaii, involves paving two rows of parking stalls, about 4,200 square feet, at 'Ewa Beach Elementary, said Jadine Urasaki, public works manager for the department.

DOE officials are looking toward more projects using sustainable materials, and may use pervious concrete at other schools that have a soil substructure favorable for such pavement, Urasaki said.

Grove Farm, believed to be the first in the state to use pervious concrete, paved its employee parking lot with the permeable material about a year ago to test its performance and durability.

The company is considering incorporating porous pavement like pervious concrete or porous asphalt in its Wailani master planned project, which includes commercial, residential and industrial development, said Grove Farm senior vice president Michael Tresler.

"Our plan was to get experience and data on the pervious surface with the longer range plan to employ this pervious surfaces in our master plan project to recapture runoff water, recycle and reuse the gray water for irrigation," he said.

Tresler said so far the pervious concrete surface parking lot is holding up and working as hoped.

"When it rains, you don't see runoff," he said. "It pretty much percolates through. It's pretty neat, actually."

GROWING INTEREST

The use of pervious concrete has been growing "exponentially" in the country in the past five to 10 years, in part because of stricter U.S. Environmental Protection Agency requirements for storm-water management, said Bruce Ferguson, Franklin professor of landscape architecture for the University of Georgia. The concrete industry also established pervious concrete installation standards several years ago, he said.

He said in addition to controlling storm-water runoff, pervious concrete is being used to recharge groundwater and allow trees along sidewalks and in parking lots — which typically have limited rooting space — to grow to full maturity. It's also been shown to be a treatment medium for urban pollutants, he said.

Porous asphalt also is available but is not as widely used as pervious concrete, in part because the asphalt industry has not yet established installation standards, Ferguson said.

While the use of pervious concrete is relatively new in Hawai'i, the product has been around on the Mainland for decades, said Wayne Kawano, president of the Cement and Concrete Products Industry of Hawaii, a nonprofit trade organization.

"Before it might have been considered, 'Well, it costs too much,' " he said. "But now if you look at it as a whole ... water retention system, then it may certainly be more cost effective."

Projects in states like Florida and Georgia have used pervious concrete for more than a decade.

The first use of pervious concrete in Atlanta is believed to be the driveway and turnout for Southface Energy Institute in 1996, according to the Georgia Concrete and Products Association.

Southface, an environmental consulting group, hasn't experienced any problems with the pervious concrete, said Southface public relations coordinator Ku'ulei Sako.

"The pervious concrete at Southface allows rainwater to trickle through the driveway and sidewalks to provide water to the plants and trees, while providing storm-water drainage for the sidewalks, driveways and other public areas," Sako said. "In metropolitan cities, like Atlanta, it also helps to reduce the heat and provide cooler temperatures while minimizing the impact on the environment."

Gordon Kenna, executive director of the Georgia Concrete and Products Association, said a stadium parking lot paved with pervious concrete in Chattanooga, Tenn., was designed to collect the water that seeps through the concrete for irrigation.