Pervious paving allows water to infiltrate into layers of limestone placed below the paving and then into soil and groundwater below. By infiltrating most of the storm water on-site, the amount of water and pollution flowing into storm sewers and directly to rivers and streams is greatly reduced. This, in turn, protects water quality, maintains more stable base flows to streams, reduces flood peaks, and reduces stream bank erosion. With infiltration, groundwater is recharged and streams are replenished with cool, clean groundwater in a more natural way. Pervious paving is one component of Low Impact Development (LID).
Depending on the site, pervious paving systems may result in significant savings by eliminating required retention and detention ponds and reducing conventional storm sewers.
Pervious paving systems may be installed at new or existing building sites. On a new or existing site, careful planning is important, including soils tests. Following design standards developed by manufacturers and government agencies is vitally important in assuring the systems work effectively.
Pervious paving systems can be designed to infiltrate any storm event, including the 100-year storm. They can also be used strategically with less costly traditional paving to infiltrate small, frequent rains and the first flush of large storms. Because the first flush of storm water carries the most pollutants, cleaning the first flush has excellent water quality benefits.
Types of Pervious Paving Systems
Porous asphalt or porous concrete installed over an infiltration storage bed of uniformly graded limestone.
Permeable Pavers (Modular Paver Blocks)
Modular concrete pavers that fit together with funnel-like openings installed over an infiltration storage bed of uniformly graded limestone.
To maintain pervious paving systems:
Inspect the site annually.
Vacuum the paving periodically to remove any build-up of leaves and dirt. Vacuum-type street sweeping is most effective.
Inspect after extremely large storms to assure full functioning.
Use scrapping and shoveling of snow and ice; avoid chemicals and sand.