WHAT PERMEABLE PAVING OPTIONS ARE AVAILABLE?
Each type of permeable paving material has its advantages and disadvantages. In terms of cost, gravel is the least expensive. However, it requires frequent maintenance and renewal, which over time, adds up to a higher cost for materials and labor. Permeable concrete and asphalt are next in terms of expense, and studies have shown that these materials are prone to clogging, negating their effectiveness. A study conducted by the Metropolitan Engineer’s Council in Denver, CO, showed a complete failure of permeable concrete under freeze-thaw conditions. Due to pervious pavement issues with clogging and vulnerability to freezethaw, the material is not ideal for all situations or climates. In fact, some cities have removed pervious asphalt and concrete pavement because of the problems with clogging and continued maintenance.
Another option for permeable paving is brick, concrete or stone pavers with permeable joints. The permeability and water-flow-through rate is dependent on the porosity of the material in the joints, the size of the joints and the entire substrate design. The joint material should adequately allow the passage of water to quickly drain, possess structural capability to withstand traffic loads and provide horizontal stability to the paving surface. Permeable pavers have the ability to infiltrate rapidly compared to most soils and a conservative approach should be taken in designing the system.
Natural stone materials, such as Porphyry, have been used for centuries throughout the world and have proven to be an excellent choice offering beauty, longevity and low maintenance. Natural stone life cycles are measured in decades with studies showing typical minimum of 60 years. Granites such as Porphyry last for centuries. Porphyry is extremely dense with a porosity of less than .6%. Using it in a permeable setting system requires the same pervious materials for the joints and attention to the details of the substrate discussed earlier, but offers an unparalleled surface for durability, low maintenance and overall functionality. The natural surface also meets the American Disability Act (ADA) for slip resistance and smoothness and is inert to chemicals.
It is beneficial for all landscape contractors to educate themselveson the art of permeable paving. With the rising popularity of segmental pavers, such as Porphyry, and the ecological benefits of permeable paving, it is likely that the demand for segmental permeable paving will continue to increase in the future. Cities such as Chicago, Boston and Detroit have started initiatives to “Green” their cities by installing permeable paving for storm water management. Other cities have allowed property owners to use more of the land area by shrinking or eliminating retention ponds if permeable paving is used on the property. It is necessary for a landscape contractor to have an understanding about the different types of permeable paving options available to fit their customers’ specific projects and capitalize on the growing number of Green initiatives in their markets. No matter the decision on the materials, it is essential for landscape architects and designers to fully understand the intricacies of permeable paving and different options available.