Using permeable surfaces in the garden
By Helen Newling Lawson
As gardeners, we know how precious water is. So when we get a good downpour, the last thing we want is to see it go down the drains. And all that runoff hitting our streams, rivers, and wetlands isn’t good for the environment either. It brings with it a host of pollutants, including excess fertilizer, oil from cars, and more. Not allowing water to absorb into the soil can also lead to flooding, the most common natural disaster in the United States.
Asphalt, concrete driveways, sidewalks, roofs, and even wood decks are all known as “impervious surfaces,” meaning water cannot filter through them. But hard surfaces in our home landscapes can also help improve usability and safety. They give us a place to park our cars, walk without getting muddy, maneuver wheelchairs and strollers, and keep chairs and tables level. They can also help direct foot traffic so that most of your soil remains uncompacted and plants are not trampled.
The good news is that there are many options for making these surfaces permeable, providing the functional and aesthetic benefits without creating runoff or other problems. Instead, the rain can go where it should – back into the water table.
There are many permeable paver options on the market. Some are made of concrete and are designed to interlock. All permeable paving solutions rely on gaps between the pavers to allow water to filter through, and require crushed stone, sand, or even grass to fill these crevices. You can even create a water reclamation system to harvest and reuse the water that drains through. To keep water draining properly, the pros at Old House Journal warn you will need to sweep or vacuum your pavers once a year to clear leaves and other debris from the joints.
This surfacing solution is mixed on site and poured in place to form one continuous sheet. One such product on the market, Porous Pave (visit their website here), is made from recycled tires, stone aggregate, and “a proprietary binding agent.” The company literature promises that it installs faster than pavers and is more easily finished than concrete and can qualify for several different categories of LEED points.
Crushed granite, also known as M10 aggregate, can also be used, either as a filler between permeable pavers or on its own. The material compacts well, making for solid, even footing once settled.
Grass pavers are made of a sturdy plastic mesh that gives your lawn the ability to hold up to heavy foot traffic or even parked cars. The plastic structure bears the weight to avoid root compaction. Information from Invisible Structures about their Grasspave2 (visit their website here) product says it also slows storm water movement and helps increase the soil’s water storage capacity.
If a walkway is needed, try limiting impervious area by setting stepping-stones into ground cover.
PROTECT WATER QUALITY
Allowing storm water to soak back into the soil is just one way to keep waterways cleaner. You can also help limit pollution by:
• Using the correct amount of fertilizer for your lawn (a soil test will tell you how much you actually need).
• Reading label directions to avoid overusing pesticides and other lawn chemicals.
• Composting lawn and leaf debris.
• Properly disposing of household chemicals and other hazardous waste.
• Keeping cars maintained so they don’t leak oil onto driveways.
• Picking up pet waste.
• Ensuring appropriate septic tank maintenance.