Natural Path Landscaping: Creating A Natural Work of Art Right Outside Your Door
Green paving technology manages storm water naturally
Permeable paving is specifically designed to allow the passage of water through the paving, and the temporary storage of water underneath the paving-all part of a process that minimizes oil and gasoline pollution of ground water. This is especially important if zoning requires a minimum percentage of impervious area or if storm water requires safe passage for groundwater recharge without runoff or a retention pond.
If a house sits lower than the street, permeable paving brings the added advantage of draining water into the driveway and into the crushed stone reservoir below, eliminating the need for an unsightly drain grate in the driveway. In fact, if the house is susceptible to basement flooding, pipes can even be put in the driveway reservoir to carry surplus water away from the home.
How it works
Interlocking concrete permeable paving allows storm water to enter the paving between crushed-stone-filled joints, then pass through to a layer of larger crushed stone, before entering a lower level of crushed stone voids for storage. Within these voids, naturally occurring micro-organisms digest oil and other pollutants that have accumulated. Finally the water in the voids filters back into the subsoil without the suspended solids and automobile-dripped pollutants contained in normal storm water run off.
During the winter months, permeable paving allows all precipitation and snow melt to be absorbed into the paving, eliminating surface puddles and potential for refreezing. In addition, experience suggests that the deep voids within the permeable paving may contribute to more rapid snow melt due to the warmer earth below.
Construction of permeable paving
These pictures show the proper construction of an interlocking concrete permeable paving driveway and parking area built on well-draining subsoil. First, the area is excavated to a depth of 21 inches below the final pavement surface. Then a 12"-thick, compacted layer of clean 1-1/2" to 2-1/2" crushed stone is installed. The thickness of this layer (and depth of excavation) depends upon how fast the subsoil can absorb the water that filters into the paving and how much storage capacity is desired. Our studies have shown that our large crushed stone base has about a 40% storage capacity between the voids, allowing a 12"-thick base to store almost 5" of water.
On top of the coarse crushed stone layer is a 4"-thick, compacted layer of clean 3/4" crushed stone. Next, a 2"-thick layer of smaller 3/8" clean crushed stone serves as the bedding layer directly under the 3-1/8"- thick interlocking permeable, concrete pavers. This same 3/8" clean crushed stone is swept between the joints of the permeable pavers. The pavers shown measure approximately 10" x 5" x 3-1/8"-thick with about 3/8"-wide joints partially around the perimeter. Granite edging restrains the pavement edges and extends down into the base layer.