Permeable Pavement Systems – May 2011

By wmadministrator

Workers install a permeable interlocking concrete paver system with mechanical help to reduce manpower expense.

Storm water flooding and runoff at homes, businesses and our communities is having a growing impact on our day-to-day lives. However, several permeable pavement systems are available to the homeowner, business owner and municipality that can significantly improve the sustainability of properties.

Assessing which low-impact development pavement system might handle a property’s storm water on site depends on the budget available and the immediate need. There are a variety of situations where permeable pavement systems can be used, and around Kentucky such systems are being installed in driveways, patios, walkways, trails, alleys, streets and parking lots. Wherever conventional asphalt or concrete pavement can be used, permeable pavement systems are an option.

The three most popular types of permeable pavement systems are pervious concrete, pervious asphalt and permeable interlocking concrete pavers (PICP). Each system has its own installation requirements, features and aesthetic value.
The common feature all three share is the below-the-surface use of open-graded washed stone or concrete aggregates that vary in size and depth. The depth of this cross section depends on local storm water requirements.

These open-graded aggregates allow storm water to infiltrate into a property’s subgrade soil or be detained and moved into a rain garden, bio-swale, bio-retention pond or even back into the storm water system.

Cost comparison of permeable pavement systems to conventional asphalt or concrete systems must take into account associated storm water controls. Permeable systems often eliminate costs for catch basins, clean outs, large concrete drain pipes and retention ponds.

Lexington Housing Authority officials said last year using permeable pavement in redevelopment of an 80-acre former public housing project site saved more than $1 million in costs for storm water control infrastructure.

Some communities, including Louisville and Lexington, have financial incentives to encourage use of permeable systems.

Installation costs are also important. Pervious asphalt has the least costly installation per square foot. Pervious concrete and permeable interlocking concrete pavers have comparable installation costs; however, if a permeable-pavers project is mechanically installed, installation costs will be less than that of pervious concrete.

When it comes to the installation of each system, both pervious asphalt and pervious concrete require a certified installer from the supplier to ensure success. Permeable interlocking concrete pavers can be installed by any residential or commercial landscape contractor that has experience installing any type of pavers. Permeable concrete pavers can be installed by hand or, for larger projects, by machine to reduce labor costs.

Pervious asphalt and pervious concrete thicknesses vary according to whether the surface will be used for foot or vehicular traffic. Permeable concrete pavers have a high load-bearing capacity and come in one thickness that supports not only foot traffic but heavy-axle loads such as firetrucks.

Where aesthetics are important, permeable concrete pavers are a slam-dunk choice – an unlimited number of colors, shapes and sizes are available. This gives a homeowner or landscape designer a wide range of selections to blend with other landscape materials.

Pervious asphalt and pervious concrete color are black and concrete grey, respectively. In some cases, pervious concrete can be stained a color at an added cost.

Maintenance on all three permeable systems is similar. All share a recommendation of sweeping and vacuuming the surface at least once per year. For pervious concrete and pervious asphalt in areas that clog more quickly, a pressure washer is used to push any blockage through to the base aggregates.
For permeable concrete pavers, sweeping the surface by hand or by machine for larger projects is all that is needed; power washing is not necessary and fill chips in the space between pavers can be easily replaced if needed.

The lifespan of permeable pavement systems varies by the finished product, but the installation process can play a key role in longevity. Pervious asphalt and pervious concrete have an average life of 20 years. Permeable interlocking concrete pavers have a lifespan of 35-plus years thanks in part to their low absorption rates and 8,000-plus PSI strength capacity.

All three systems comply with federal NPDES Phase II rules for storm water, and are recognized by the EPA as a Best Management Practice for storm water control.

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