One way to grow any type of business is to offer another service. One way for erosion control specialists to find additional services to offer is to look at the work of civil engineers, landscape architects, and other specialists who manage stormwater.
Stormwater runoff causes, or at least accelerates, erosion. Stopping that runoff or slowing its amount and velocity can be an effective means of controlling erosion.
Years ago, stormwater was usually managed by piping it off of the property as quickly as possible so that some other property owner or entity could deal with it. Federal and state regulations have constrained—if not eliminated—this poor practice. So have stormwater utility fees.
Stormwater specialists in many areas now strive to follow practices that infiltrate as much stormwater onsite as possible. One of the strategies they use is installing permeable, pervious, or porous pavers; porous pavement; or asphalt.
Pavers and pavement that permit stormwater runoff to soak into the ground instead of running off the surface are considered green infrastructure techniques. They allow the rainfall to act the way it would if the area were still in its predevelopment state.
These pavers or pavement offer a property owner two advantages. First, reduced stormwater utility fees—especially on a commercial property—can be significant now and in the years ahead.
Second, such pieces of green infrastructure can earn points that help a project qualify for Leadership in Energy and Environmental Design (LEED) certification, because they allow stormwater infiltration to reduce runoff volume and improve area water quality.
Stormwater utility fees are being implemented in increasing numbers in American cities. Reducing them by earning stormwater credits is one reason for the growing demand for permeable and pervious pavers. They’re being installed on properties ranging from small residential walks and driveways to large commercial sites.
A New Showroom
One of the largest permeable paver installations in the US is in the parking lot and hardscape area around the showroom at McCord’s Vancouver Toyota Scion in Vancouver, WA. The site has 100,000 square feet of permeable pavers, part of the construction of a new showroom that lasted from 2008–2010.
“We turned the entire parking lot into a stormwater facility. It’s a [detention] pond that isn’t a pond,” says Bob Sable, then a project manager, now communications director, at MacKay Sposito, a Vancouver, WA, civil engineering firm.
Sable notes that while the dealership “had to pay extra up front, we saved them from losing an acre or more to [an otherwise required] stormwater pond.”
“Half of the pavement was laid, then the showroom was built, then the rest of the pavers were laid,” says Gale Schroeder, manager at Willamette Graystone, the company that manufactured and supplied the permeable pavers for the project.
A family-owned firm since 1946, Willamette Graystone has branches in Eugene, Medford, and several other cities in Oregon. Along with permeable pavers, Willamette Graystone manufactures various concrete and masonry products.
The McCord dealership is located just over the Columbia River from Portland, OR. Its employees, like other area residents, know that removing pollutants is essential to the water quality of the Columbia River, as is reducing stormwater runoff volume.
The dazzling showroom building at McCord’s Vancouver Toyota received a LEED Silver rating in April 2012. Numerous green strategies and best management practices (BMPs) earned LEED points for the project.
Native plants and a drip irrigation system save water. Eighty-nine percent of construction waste was recycled. Rainwater is captured and used for the dealership’s car wash. LEED points were awarded for the permeable pavers that surround the dealership.
The pavers at McCord’s were designed by Advanced Pavement Technology of Yorkville, IL. They are part of the company’s Bio-Aquifer Storm System (BASS), which was designed and patented by company founder William Schneider.
Schneider has been in the paver business for more than 35 years. He is a founding member of International Concrete Pavers Institute (ICPI). He was ICPI’s first instructor and established the manual to teach and train level one certification.
The BASS created by Schneider can be put in place with any of four different shapes of pavers. All of them are manufactured to the specifications of ASTM C936, the Standard Specification for Solid Concrete Interlocking Paving Units. Each type can be installed by hand or by machine, and more than one type can be used on the same project.
All of these pavers are compliant with the Americans With Disabilities Act (ADA) so that wheelchair wheels, heels, and cane or walker feet can’t get trapped between them. Because they allow stormwater to infiltrate naturally and impurities to be removed from runoff as it percolates through the soil, they are used as BMPs for many types of projects.
For the McCord’s Vancouver Toyota site, the Aqua-Bric IV design was selected. Instead of being flat on top, the pavers have a stone texture. They are 3.125 inches thick and were put in place by machine.
The white color of the permeable pavers “meets the solar reflectability requirement” of LEED, says Schroeder. “They have a 33% reflectability.”
He notes that each 5- by 10-inch paver has a false joint “so that it looks like a five-piece cobble pavement.” This look is achieved by varied placement of grooves across the individual pavers. For example one paver has a groove across the middle, another paver adjoining it has a groove two-thirds of the way down, and the next paver has no groove.
“When they are laid in a herringbone pattern, that gives the impression of multiple-sized stones, but they are all the same size,” explains Schroeder.
These permeable pavers rest on a bedding layer 2 inches deep. This layer consists of ASTM-rated No. 8 stone, as per standard ICPI recommendation.
Directly below the bedding layer is the base layer, a choker course of medium-sized stone, ASTM No. 57. It measures 4 inches deep. The sub-base layer, 14 inches deep, consists of ASTM No. 2 crushed stone.
“Soil here is thicker than a sandy, gravel soil is. It is clay, so the site needed a deeper reservoir layer to wait for the slow [rate of] infiltration,” explains Schroeder. “It also needed a thicker base than normal because it had to be strong enough to support the transport trucks [large trailers bringing in new cars].”
Summing up, he says, “It was weight and storage [issues] that drove the design” for the permeable paver installation.
“The pavers had to be able to bear all that weight of the transport trucks standing there,” says Sable.
Sable notes a challenging aspect of the project. “The site had variable infiltration rates. Some acres were functioning fine, but some had almost no infiltration at all. The site was bowl-shaped, at the bottom of a drainage basin, too.”
Stormwater infiltrates on site. As a backup, at the lower end of the parking lot a tile channel was added to carry stormwater runoff to a bioswale.
“No water has ever flowed out of the tile. That’s remarkable on clay soil,” says Schroeder.
“It has worked very well,” says Sable. “There was a snowfall a few months later. Marv, the dealership’s owner, remarked how quickly the snow melted, and there was no ponding. It will easily hold runoff from a 100-year storm event.”
National Renewable Energy Laboratory
Energy consumption and the wise use of water and other natural resources is taken seriously at the US Department of Energy’s National Renewable Energy Laboratory (NREL) in Golden, CO. Of the seven LEED-certified buildings at NREL, six qualified for the LEED Platinum rating.
Each building on the NREL campus was designed to be energy efficient and environmentally friendly, inside and outside. Permeable pavers helped the NREL earn its LEED ratings. They were installed in five separate areas as buildings were added to the campus.
The first project was done in the summer of 2010. Three hundred linear feet of pavers were installed on the campus road along with 11,000 square feet of pavers at the Research and Support Facility (RSF) plaza.
The next RSF installation of permeable pavers, in the summer of 2011, included 1,400 linear feet on the campus road and 3,000 square feet at the plaza. The third RSF installation, during summer 2012, involved 350 linear feet on the campus road and 9,000 square feet on the plaza.
Earlier that year, in spring, permeable pavers were installed at the Energy Systems Integration Facility, the building that houses NREL’s supercomputer. The fifth project, in spring 2014, involved installing 750 linear feet of permeable pavers on the campus road.
Each area of permeable pavers at NREL has an underdrain system. These drains were necessary because of the poor infiltration rate of the soil.
“The soils on our site do not promote infiltration well as far as storage. [The permeable pavers] reduce the peak flow minimally,” says Michelle Slovensky, LEED AP BD+C, energy program manager at NREL. “We have a gravel underdrain system that collects and conveys [runoff] to our watershed basins that ultimately reach our detention pond. Its most effective use has been from a water-quality aspect. The filtration helps strip impurities that would otherwise reach our downstream discharge.”
All of the pavers at NREL are Eco-Priora from Uni-Paver, a division of Uni-Group USA. They were manufactured by the Pavestone Co. of Henderson, CO.
The design/build team was Haselden Construction of Centennial, CO, and RNL Design of Denver. Installation was done by Continental Hardscape Systems of Westminster, CO.
Pavestone blended together two of its standard paver colors, tan and limestone, to make a custom shade for all of the NREL pavers. This custom color has a higher solar reflectivity index (SRI), thus lowering heat gain on the NREL campus. Lower heat gain means less energy required for cooling and earns more LEED points.
“We call it ‘LEED White,'” says Mike Midyett, Pavestone’s general manager.
The Eco-Priora permeable pavers are 3.125 inches thick. Below the pavers is a 2-inch-thick bedding and joints layer composed of ASTM No. 8 stone.
The 12-inch-thick base layer directly below the bedding and joints layer is not composed of the usual stone. Instead, it consists of recycled concrete. Using this recycled material offered two advantages: it earned additional LEED points and it cost less than the stone.
Concrete bands separated the paving areas, and work space was tight. The pavers were installed by hand.
Eco-Priora pavers can be produced in a variety of square and rectangular sizes. Because they require minimal chamfers and have narrower joints than some others, they are ideal for pedestrian and ADA handicap-accessible paved areas. Eco-Priora pavers are also suitable for locations that have vehicular traffic.
The narrow pavers left room for the installation of solar paver lights in the outdoor café area for employees and their guests. The pavers are interspersed with small bioretention areas. Native plants in these areas include Rocky Mountain penstemon, desert four o’clock, and pussytoes.
Permeable pavers produced years ago did not always perform well when installed in cold climates; the repeated freezing and thawing sometimes caused damage. Fortunately that has not been the case with the Eco-Priora permeable pavers at NREL.
“There have been no issues of system failure or location displacement of the pavers in Colorado’s cold climate. In fact, they have reduced ice buildup since we have warm sunny days in winter. No ponding issues occurred in any location,” says Slovensky.
Maintenance needs are minimal. “Special equipment is necessary for snow removal, but when the correct equipment is used it poses no issues,” says Slovensky. “From time to time a topoff [is needed.] The gravel in between pavers must be replenished.”
American Modular Systems (AMS) of Manteca, CA, is one of the nation’s leading modular manufacturers. The company has been designing and building commercial and educational facilities since 1983.
Gen7 is the company’s line of schools and educational buildings. It was developed to make learning healthier and easier for students and to make such a system more affordable for school districts. Research shows that the quality of school buildings has a significant impact on how well students learn.
Gen7 modular buildings by AMS feature abundant natural light and excellent acoustics and air quality. Besides the highest energy efficiency, they are designed to be environmentally responsible facilities.
Gen7 meets the same LEED standards as a conventional building, yet can be built 60% faster and for 30% less cost. Because Gen7s are designed to meet LEED standards, the added expense of attaining LEED certification is modest.
To prevent weather delays, the AMS buildings are constructed within a climate-controlled factory. When they are delivered, they are 90% finished and are placed by crane.
The Gen7 design concept was used for the Regional Environmental Studies Center (RESC), which AMS built for the Manteca Unified School District (MUSD). Finished in September 2013, this building earned a LEED Gold rating from the US Green Building Council a year later.
Jason Messer, MUSD superintendent, says his school district “wanted to raise the bar by creating a multi-use learning center that is both energy-independent and environmentally responsible, providing a model for future learning spaces within our district and demonstrating our commitment to best-in-class environments that benefit our community, staff, and students.”
The modular RESC is a zero net energy building. It is also the first K-12 school supporting facility in California’s Central Valley to achieve the prestigious LEED Gold rating.
LEED points were awarded for various building and site features, including pervious pavers.
“This is a district office facility, not a school. We wanted to try out different things, such as an onsite stormwater drain, drought-tolerant native plants, and a rain catchment system to see if we wanted to install them in schools,” explains Aaron Bowers, MUSD’s director of operations.
Bowers and other school officials first saw the Xeripave Super Pervious (SP) pavers at a trade show. “The display at the trade show is what caught our eye. They had a hose turned full on, pouring water onto a paver, and the water was going right through,” says Bowers.
The school district decided to change the plans for the RESC, substituting some of these pavers for the originally planned concrete surfaces. The school district’s funds were limited, but Xeripave SW, the exclusive distributor of these pavers in California, decided to donate the needed pavers.
“We became aware of the project, and we felt that the donation would be good for us, since other school districts would come to see it,” says Gary Luiz, co-owner of Xeripave SW.
The pavers manufactured by Xeripave (an affiliate of Ultrablock) have an infiltration rate of about 1 gallon per second per square foot. That high infiltration rate is possible because each paver has a 35–40% void.
Luiz concedes that Xeripave pavers are more expensive than other permeable pavers. However, he says, they are more cost-effective than it first seems because they do not have to cover an entire surface. If only 12–18% of an area is covered with Xeripave SP pavers, runoff from the entire area can be infiltrated onsite.
Each Xeripave SP paver measures about 12 by 12 by 2 inches. They are made of an aggregate found only in California, Oregon, Washington, and Montana, bound with a two-part polymer. They are UV-resistant and are unaffected by freeze and thaw cycles.
The installation of the pervious pavers was done by the general contractor for the RESC building, C.T. Brayton of Escalon, CA. The driveway was graded with a two-degree slope so that water coming from the front of the building would flow to the pavers.
Finished in a color called Dupont, the pavers at the RESC building cover 384 square feet of the walkway from the street to the front entrance. There are five sections of the pavers, in line with each of the walkway’s five tree wells. A plaza section also contains some of the pavers.
Bowers notes that the pavers are “technically a bit smaller. We ended up installing some edge restrainers where the edges of the pavers were not contained by the concrete.”
MUSD has been pleased with the Xeripave SP section of the RESC facility. “So far it’s worked out well,” says Bowers.
Luiz says that testing after the pavers were installed showed “a coefficient of zero. Any water that hits that paver will go into the ground.”
Lincoln Park Zoo
At the Lincoln Park Zoo in Chicago, the macaques—commonly called snow monkeys—are popular with visitors. What’s popular with the macaques is their new exhibit, Regenstein Macaque Forest.
Covering 7,300 square feet, the outdoor exhibit includes a hot spring, stream, and artificial and natural trees. It was designed by The Portico Group of Seattle, a firm that specializes in designing zoos and parks.
Because the new exhibit involved extensive renovation, Lincoln Park Zoo officials decided to take the advantage of the chance to install permeable pavers to help with stormwater management. Besides the pavers outside the macaque exhibit, the zoo’s new west entrance has a permeable paver walkway. Together the two areas of permeable pavers total 8,200 square feet.
Lincoln Park Zoo’s permeable pavers are StormPave from Pine Hall Brick Co. of Winston-Salem, NC. The English Edge style paver is designed for institutional and commercial projects where impervious surface restrictions apply. StormPave has joint openings that meet ADA restrictions (less than ½ inch) when onsite retention/infiltration is required. The pavers are available in five colors.
Steve Thompson, senior vice president of capital and programmatic planning at Lincoln Park Zoo, says that in both locations the StormPave permeable pavers are “meeting our expectations.”
The Brick Industry Association (BIA) awarded Pine Hall Brick Co. a Silver Award in Paving/Landscaping for its west entrance and macaque exhibit renovation. (This is one category within the Brick in Architecture awards, given annually.)
As these projects show, controlling erosion by managing stormwater runoff via permeable or pervious pavers works in varied circumstances. Reduced stormwater utility fees and federal and state regulations can help make such green infrastructure more cost-effective.