Arboretum tests eco-friendly pavers
Thrilled as I was to watch the snow finally melt, its absence uncovered some glaring holes.
Divots, cracks and bona fide potholes emerged from winter's cover of snow on our driveway. Maybe the thaw-and-freeze cycle was just too much, or maybe I blissfully forgot the deferred maintenance needed.
Spring garden planning often includes new flowers, shrubs or trees, but sometimes you need to overhaul the hardscapes, too. Patios, sidewalks and driveways are expensive to replace, so what are some of the new options that offer both durability and environmental benefits?
New materials from recycled glass to permeable pavers are enticing for their aesthetics and touted eco-friendly claims. Whereas traditional hardscape materials like asphalt and concrete can create heat islands and promote stormwater runoff, permeable alternatives help cool the area and retain water where it's needed.
But can they stand the test of time?
To answer that question, the Morton Arboretum, in partnership with manufacturers and contractors, has installed a variety of permeable pavements in sidewalks and walkways around its Thornhill Education Center.
"My vision, as we continue to redevelop Thornhill as an education center, is to highlight sustainable options in whatever we do," says Kris Bachtell, the arboretum's vice-president of collections and facilities.
To that end, since 2005, five different permeable pavement products have been installed within immediate walking distance of the arboretum's education center. Permeable pavement allows water to flow through tiny, connected holes or pores into the gravel substrata beneath the pavement surface, then into the soil. This cools the water, and, with appropriate filtering plantings, helps remove pollutants that might otherwise go into storm sewers.
The five pavement products on display at Thornhill are recycled granite pavers, recycled glass pavement, pervious concrete and two types of permeable pavers. The recycled granite pavers, not in and of themselves permeable, have nonetheless been set into a permeable profile underneath.
Made from recycled scraps of granite countertops, the pavers make use of erstwhile landfill candidates. Bachtell says they offer a "residential look."
Recycled glass pavement -- made from crushed beer bottles and other glass -- comes in several different color options. The FilterPave crushed glass is tumbled and smoothed and mixed with a polyurethane binder to form a continuous surface when poured into retaining forms. It blends well into the landscape, even though a bit of glitter reminds you of frosty beverages past.
Two types of permeable pavers, Aqua-Bric by Paveloc and Eco-Optiloc by Unilock, offer different color options and configurations of the pavers. Bachtell notes that the pavers don't crack or break apart as easily as traditional concrete, but rather will "rise in a whole piece," moving as a unit.
Filtercrete, yet another sample being tested at the arboretum, is a pervious concrete mixture that "looks like cottage cheese" when it's poured, according to Bachtell. It is gray colored, like traditional concrete. The product bonds concrete with small rocks, thereby allowing air and water to filter through.
Bachtell says that, from a maintenance standpoint, the different paving options have, so far, held up as well as traditional materials. One material did need to be reinstalled, but that appeared to be an anomaly, possibly an installer error. Otherwise, the pavements have endured a few winters with no kid-glove handling.
One thing Bachtell cautions against is the use of sand or small grit in the winter. It will "clog the pores" of the permeable pavement. Generally, don't use anything smaller than the gravel used in the permeable pavement itself.
The arboretum's main parking lot near the Visitor Center showcases yet another installation of environmentally-friendly paving. With bioswales and native vegetation, the parking lot is an entire system working to filter and channel runoff to remove pollutants and redeploy water.
The arboretum website, mortonarb.org, contains detailed information and links to the manufacturers and installers of each product. Bachtell suggests contacting those representatives for pricing and estimates. Often, permeable products may cost more than traditional ones upon installation, however, manufacturers claim a longer product life span and less ongoing maintenance.
Explore these permeable pavement options at the arboretum before next winter's snow covers up the problem again!
• Cathy Jean Maloney writes for the Morton Arboretum.