Reducing Water Run-off
Is it time to replace your driveway or the walk to your front door? Have you considered installing some type of permeable paving instead of the traditional asphalt or concrete? Permeable or pervious paving allows water to pass through the paving material’s seemingly solid surfaces rather than run off of the surface. Water run-off from driveways, walks, and paved parking lots can erode surrounding soil, damage lawns, and flood streets. This becomes a problem when we pave over previously vegetated areas and decrease the area’s natural ability to handle stormwater.
Types of permeable paving include porous/semi-porous pavers, concrete turf block, and plastic grass paving. Porous or semi-porous pavers can be concrete or a plastic-based product. Size of the particles that comprise the pavers allow more water penetration than normal concrete products. Concrete turf blocks are a segmented concrete paving system with voids that allow grass growth between or the areas to be filled with gravel. These are excellent for use as driveways or parking lots. Plastic grass paving is a plastic interlocking paving system that also has voids which can be filled with grass or grass. The turf blocks or plastic grass pavers are often used in areas which are subject to large, intermittent parking requirements such as the land adjacent to sports fields which can be used for parking on game days or parking lots of religious institutions which need additional parking only a few days of the week.
Areas covered with gravel chips are completely permeable and can be used for walkways and driveways. Maintenance might include occasional raking to redistribute the gravel and insure an even walking surface. Consider installing two concrete strips for parking with grass planted between, rather than paving the entire area. Impermeable paving blocks spaced with wide joints filled with permeable material such as gravel or grass can also be used. Install a narrower driveway – this will cut down on the amount of water runoff and also reduce installed cost which is based on the square footage to be installed.
It is interesting to note that both concrete and asphalt can be made to be pervious, however to create a pervious surface with either material requires careful control. They must contain a single-size aggregate (usually 3/8 of an inch) to create voids that allow stormwater to sift through the material rather than run off the surface. Pervious concrete typically consists of specially formulated mixtures of Portland cement, uniform, open-graded coarse aggregate, and water. Even if the material is formulated correctly, improper compacting or troweling can reduce the pervious nature of the materials and reduce their effectiveness.
Permeable paving allows water to be ‘filtered’ through the material, rather than run off the surface and possibly wash pollutants into the stormwater system. Encouraging the use of these alternative paving options allows stormwater to be routed naturally and not enter what could be an over-burdened stormwater system.
Before installing any of the traditional or non-traditional materials, check with the local building authority for any paving guidelines which may describe the size of paved area allowed on a particular size building lot or additional drainage that may be required when adding paved areas.
