Permeating Issues

‘I’ve taken up a fair amount of my column space in WaterShapes with discussions of the wise use of water, and for good reason: What could be more important to watershapers,’ wrote Bruce Zaretsky to open the April 2010 edition of On the Level, ‘than knowing how to make the best possible use of the material that defines our profession?

‘The common thread in all of this coverage . . . is that, ultimately, our aim must be to preserve the integrity of water, to cleanse it for return to the groundwater system and to use what we need and no more.’ He continued:

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‘One major topic I’ve yet to mention has to do with one of the single greatest threats to our waterways, whether they be lakes, rivers, streams or oceans: The plain fact is that much of the surface water that now flows into them is loaded with pollutants. With multiple generations of residential, commercial and industrial construction, we’ve steadily displaced soil, wetlands and woodlands and have replaced them with hard, impermeable surfaces . . . onto which we drip oil, antifreeze, transmission fluid and other toxins that wash off into our storm sewers and flow into our waterways.’

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‘Some of you are doubtless familiar with the array of permeable pavements now available in the marketplace, but my experience in the field tells me that many of us in the trades are not yet up to speed with this exciting surfacing technology. As I see it, this is something we should all get familiar with right away.’

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‘They function just as advertised: Instead of forming solid surfaces, permeable pavements allow water to pass through them and either percolate into the soil or flow into subgrade drainage systems for controlled release into waterways.’

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‘Beyond these direct substitutions for solid surfacing materials, there are also the permeable pavers that have become familiar in most markets. . . . Interestingly, these systems started out by offering a less-expensive method for installing pavements with the added advantage that the pavers could be pulled up and replaced fairly seamlessly if subsurface work needed to be done.’

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‘Seeing an opportunity in the desire for increased permeability, manufacturers have recently begun producing pavers that are designed and engineered for installation with significantly larger gaps to be filled with coarse sand or finely crushed stone (but still no stone dust, which tends to cake and become impermeable). The idea is to capture that much more water within the system before it can run off the surface.’

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‘To be sure, some pollutants might pass through the gaps in these systems, but much of the load would be captured in the bedding and base systems and would be significantly diminished as it moved through the system. Even in simple relative terms, this is far better than running all of the surface water to a catch basin or storm sewer for direct introduction to our waterways.’

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‘That sort of experience is being backed up by research. Indeed, a study done by the Toronto & Region Conservation Authority (TRCA) in 2005-2006 found that a permeable-paver test plot showed a runoff of less than 10 percent of the water from a two-and-three-quarter-inch storm of five hours’ duration. . . . TRCA also conducted a water-quality analysis to test for retention of heavy metals, oils, grease and other pollutants. . . . Suffice it for now to say that stopping the water before it runs unchecked into fragile waterways offers a better (if not the best) solution.’

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‘To be sure,’ Bruce concluded, ‘I’m still a major proponent of using raingardens, constructed wetlands and bio-retention swales to manage the runoff from parking lots, but I recognize that not all sites are suitable for such systems. . . . [W]hile I recognize that permeable surfaces are not the only solution to runoff issues, I see that in the right context and the right setting, they represent another option in a growing spectrum of ways we can make the best and wisest use of our most precious natural resource.

What’s been your experience in using permeable surfacing systems in your projects? Have the aesthetics reached a point where the materials are acceptable for high end project, or do you still need to find alternatives to these more-commercial solutions?

Bruce Zaretsky is president of Zaretsky and Associates, a landscape design/construction/consultation company in Rochester, N.Y. Nationally recognized for creative and inspiring residential landscapes, he also works with healthcare facilities, nursing homes and local municipalities in conceiving and installing healing and meditation gardens. You can reach him at [email protected].