Maintenance Concerns
As with any new construction, concern is always expressed for long-term maintenance and durability of the product. The non-profit organization LID Center has found that as with all the pavement systems—permeable concrete, permeable asphalt, permeable interlocking concrete pavers, and vegetated permeable pavements—“maintenance is low and has been shown to be quite resilient over time, as long as the openings remain permeable.”⁶ The pollution-trapping benefit of vegetated permeable pavements is apparent, but there may be some concern about this diminishing over time. With maintenance, these systems can reasonably last up to 20 years, according to several sources.

Here are some tips on keeping these systems functioning: 1) make sure drainage from other areas with sediment loads does not flow over the pavement, clogging the voids; 2) perform periodic inspections following storms greater than ½ inch in depth to observe any standing water; 3) consider choosing salt-tolerant grasses where de-icing is common, and adding Teflon runners to snow plow blades to prevent damage; 4) monitor the turfgrass for diseases, fungi, and insect infestations, using biological controls such as ladybugs and organic controls; and 5) consider implementing “resting periods” that vary access points and parking stall use to reduce wear on turf and giving it time to recover from heavy use; and 6) consider the benefits of overseeding and top dressing to promote healthy living turf. The City of Chicago, for instance, recommends special care during snow removal and might even require mowing turf at times.

Differentiating between Vegetated Permeable Pavements

Each type of vegetated permeable pavement system is designed to promote infiltration of rain and snowmelt. Each system contains openings to be filled with sand, soil, or a sand/soil mixture that in combination with the bedding layer becomes a rooting zone for vegetation such as turf or groundcover. Note that comparison of the four types of vegetated permeable pavements is very difficult based on their diversity and different properties. As Ferguson states, “Many manufacturers supply guidelines for installation of their products. However, the reinforced plastic/geocell-producing industry does not have the benefit of an industrial association to set uniform standards of comparison or to educate potential users about appropriate applications. Manufacturers' reports of strength and other characteristics are too often based on tests that are inconsistent between one manufacturer and another, and between geocells and other types of paving materials. In the absence of uniform measures of performance, potential users are left to rely on experience with specific models in specific types of settings.” He goes on to suggest that “An impartial industrial association would give guidance to users and credibility to suppliers. The formation of an industrial association or ASTM (American Society for Testing and Materials) committee to formulate uniform standards of plastic paving geocells is called for.”

It is noteworthy to understand that compressive strength is often used to compare plastic and concrete products. On the one hand, concrete products have a required compressive strength for load bearing; however, unit dimensions and resistance to wear ultimately determine their performance. Compressive strength for plastic products, on the other hand, can be derived from sand-infilled vertical plate lab tests. A substantial portion of the load is taken by the sand infill which increases the compaction of the material in the void space.