Pervious Pavement

Soaking Up Green Perks

by Paula Widholm

Brian Lutey has a big job convincing owners, city officials, engineers and contractors in the Chicago area that pervious concrete really does work.

As vice president of green building for Mokena-based Ozinga Illinois, Lutey promotes and develops the concrete supplier’s pervious concrete program. He became convinced of the material’s advantages during his time as promotions manager for the Indiana Ready Mixed Concrete Association, where he helped develop a program to promote it. Now, the IRMCA has been asked to assist groups in more than nine states in developing their own pervious concrete programs.

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A big one is the city or Chicago. A $900,000 pilot Green Alley Program fully reconstructed five alleys in 2006 with pervious pavements (concrete, asphalt or pavers).

In 2007, green solutions were applied to the rehab of 22 alleys. Because rainwater drains through the pervious pavement, the city, which has standing-water complaints in more than 500 alleys, could benefit.

“We were one of the first agencies to try it,” says Cindy Williams, quality assurance manager for the Chicago Department of Transportation, which oversees 1,900 mi of alleys.

Pervious material contains little or no sand so that voids are created, according to the National Ready Mixed Concrete Association in Silver Spring, Md. Sufficient paste to coat and bind the aggregate particles together creates a system of highly permeable, interconnected voids that drains quickly.

The rocky mixture is placed like asphalt. It contains about half the water of regular concrete, and it is not finished like concrete.

“It’s like the gravel is the peanut and the cement is the chocolate coating,” Lutey says.

Pervious pavements haven’t been used much locally because owners and contractors aren’t familiar with it, and because “nobody believes research that’s done outside the area,” Lutey says. “In the Netherlands, pervious concrete is used on highways. In Japan it’s used all over roads and parking, but nobody believes it’ll work in Chicago.”

On the five pilot alleys, a few winters have passed to test the pervious pavement’s freeze-thaw holdup, and there have been plenty of heavy garbage trucks rumbling across them. So far, there’s been no trouble like rutting or cracking, but still there’s no rush to do all future alley projects with the material, Williams says.

“We’re still collecting and monitoring data from those five alleys,” she adds. “We’re going forward slowly and getting some standard specs. We are trying to use more green products and recycled content as much as possible.”

According to the National Ready Mixed Concrete Association, the initial costs of pervious concrete can be up to 1.5 times higher than for conventional concrete. On parking lots, pervious is 6 or more in. thicker than the 4-in. thickness for conventional.

On the upside, the NRMCA says the life-cycle costs can be lower for pervious pavements because there is a reduced need for large detention ponds since the pavement itself acts as a detention area. Parking-lot owners will also spend fewer dollars on labor, construction and maintenance of detention ponds, skimmers, pumps, drainage pipes and other stormwater management systems.

Nationally, the concrete industry is starting to embrace the material.

“When we first started looking at pervious concrete, the concrete industry was concerned that if anything went wrong it would be a huge setback,” Williams says. “Now, less than two years later, they think it’s the greatest thing since sliced bread. But, the industry still doesn’t have a full grasp on its own product.”

Lutey’s trying to change that by training contractors and touting its benefits.

Regarding its placement, Lutey says, “It’s not rocket science. It’s just different, and getting people to do things differently can be the most difficult part.”

The process is not difficult; it just requires different techniques and chemicals. “You actually cure it with soybean oil, which is environmental friendly,” Lutey says.

But Lutey adds that owners and contractors need to be convinced to use it.

“It looks like when water gets in there, it’ll fall apart,” he says. “I felt the same way when I started seven years ago. But it’s freeze-thaw resistant, and it has an anticlogging design so it’s not receiving a lot of sediment. There’s very little, if any, maintenance. It’s less likely to clog than any other porous pavement like pavers or asphalt.”

Pervious alternatives solve the many environmentally detrimental effects of traditional concrete and asphalt, such as the heat-island effect, clogged stormwater systems and depleted groundwater supplies. Also, since there are tiny air pockets throughout the material, tree roots can get air and water to grow, Lutey says.

Lutey was meeting in mid-May with Chicago officials to consider eliminating the requirement for curbs and gutters for lots that use pervious pavements.

“You don’t need curbs and gutters because there won’t be runoff,” he says. “You can take that money and put it toward trees. Instead of shipping water to the sewer system, you filter it through pervious concrete and pack it into the ground and you can go back and fill wells and pump water out of ground instead of shipping the groundwater away.”

Pervious concrete also eats the oils and grease washed in from its surface.

“It’s a big biofilter and sponge that leaves water clean,” Lutey says. “Most people don’t consider concrete to be green. You build with it 100% local material including slag from steel mills and cold fly ash.”

Bridgeview, Ill.-based Rose Paving and its subcontractors created a 6-acre parking lot near U.S. Cellular Field, home of the Chicago White Sox, in December with pervious concrete pavers. A new city ordinance that would have required the owner to build a $1.5 million underground storage tank largely influenced the decision to use the alternative method, Lutey says.

With the pervious pavers, rainwater soaks through the pavers into a 14-in. gravel base, created from recycling old foundations and slabs onsite. Since the ground absorbs the water, the lot creates no runoff.

The $3.6 million project saved $400,000 over the price of building the underground stormwater tank and creating a traditional asphalt lot, Lutey says.

“It costs less, lasts longer and looks better than asphalt,” says Charles Sampey, director of development & facilities for Illinois Sports Facilities Authority, owner or the stadium. “Pavers have been around for a really long time. This is an excellent example how to apply new methods to traditional materials.”

Building an underground stormwater system “is a very expense proposition,” Sampey says. “We were one of the first to price and see how the two systems compare. In addition to saving $400,000, we also gained the benefit that it will last 40 to 50 years, not the eight to 10 years of asphalt.”

Sampey says more owners aren’t opting for pervious material because “they’re not aware of it. Everyone’s so used to asphalt everything. Some people don’t need to have a parking lot last 40 years. It’s also a perception issue. Paving contractors are afraid of it or don’t know how to do it.”

One other benefit of pervious pavers is that installation goes quickly. A machine simply grabs 3- by 4-ft sections of the pavers and drops them on top of the gravel.

“The project’s goals were to put down 15,000 sq ft a day,” Sampey says. “We were starting to hit 20,000 sq ft a day.”

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