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Environmental Solutions: Permeable Pavers

By Ray Rodenburgh, director of marketing for Unilock

In the design/build industry, "green" has become the day's buzzword. There is almost no commercial project design today that has not, in some way, been touched with "green" influences, whether they are regulatory or voluntary. "Green" design encompasses many facets of construction and landscaping. In fact, the landscape portion of the design can most often have the greatest environmental impact.

Paver bundles are manufactured in eight to 10 layers and placed in a row along the area of installment. The European-manufactured Optimas machine can pick up one full layer out of the bundle, installing about 10 to 12 square feet at one time. The goal is to try and make the machine as efficient as possible. Placing the paver bundles every 10 feet allows the machine to move the pavers with as little movement as possible. Photos courtesy of Unilock


Several organizations and environmental groups have emerged to take on the challenge of promoting, educating, and regulating "green" best practices. One such organization is the United States Green Building Council (USGBC). They have developed a "green" rating system called LEED(R) (Leadership in Energy and Environmental Design).

LEED was created to:

o define "green building" by establishing a common standard of measurement
o promote integrated, whole-building design practices
o recognize environmental leadership in the building industry
o stimulate green competition
o raise consumer awareness of green building benefits
o transform the building market

LEED provides a complete framework for assessing building performance and meeting sustainability goals. Based on well-founded scientific standards, LEED emphasizes state-of-the-art strategies for sustainable site development, water savings, energy efficiency, materials selection and indoor environmental quality. LEED recognizes achievements and promotes expertise in green building through a comprehensive system offering project certification, professional accreditation, training and practical resources.

Like any other type of paver, permeable pavers are made with high-density concrete. Their shape is what makes them different because it creates larger gaps between joints and allows more water to filter back into the soil rather than run-off into storm drains. All permeable pavers have a permeability ratio, like the Ecoloc pictured here, which has a 12% void ratio.

A More Conscious Design

Over the last several decades, many factors have led to the creation of groups like USGBC. Increases in population and expensive real estate have created intensively developed urban areas. These areas have not only taxed our infrastructure, but have also negatively affected our environment. We have come to the realization that sustainable development needs to be taken more seriously. Companies that manufacture concrete products have already taken note because their products are a large contributor to the "concrete jungle." In Europe, problems with a declining water table, heat islands in their major urban areas, and pollution in water coming off impervious paved areas, forced their hand to search for a solution. Concrete paver manufacturers saw the writing on the wall in Europe years before it became an issue in North America. These companies took the lead and introduced several permeable paver options to the design and civil engineering community.

Permeable pavers have many benefits. They...

o Accommodate detention facility requirements
o Qualify for Credit 6 - LEED: Limit disruption of natural water flows by minimizing storm-water runoff, increase on-site infiltration, and reduce contaminants
o Qualify for Credit 7 - LEED: Reduce heat island affect (light colored pavers)
o Offer long-term durability
o Are easy to repair
o Provide groundwater recharge
o Control erosion in streambeds and riverbanks
o Facilitate pollutant removal
o Reduce thermal [water] pollution
o Eliminate standing water on pavement

Paver Options

There are several options in permeable paving. They include: 1) unit pavers, which provide an automatic opening (void ratio), allowing water to percolate into the ground; 2) unit pavers that are spaced to allow for a void ratio; 3) gravel; and 4) turf. Your selection may depend on municipal or state regulations, proposed use, visual appearance, maintenance, and budget. Unit pavers that provide an automatic void ratio, such as Ecoloc, provide huge benefits for the environment, the designer, the end user and the installer. As mentioned, the environmental benefits virtually speak for themselves. For the designer/engineer, permeable unit paver systems can be engineered to accommodate the site conditions and the intended use. They are increasingly being used to pave international shipping ports where both performance and environmental concerns need to be dealt with. For example, Howland Hook, a major inter-modal shipping yard operating under the New York Port Authority, was paved with a permeable locking unit paver for just those reasons. From an installer's perspective, the pavers can be installed mechanically, providing efficiencies in paving large areas. For example, a three man crew can install anywhere from 5000 to 8000 square feet per day.

Residential Contractors

So what about the residential contractor? Where do they fit in? They are not installing huge shipping ports or parking lots, but the responsibility of design/build residential landscape contractors to develop "green best practices" is the same. Paved driveways upwards of 5,000 to 10,000 square feet are common. Much of the rain from these driveways gets directed into storm sewers and ultimately into adjacent streams and/or lakes. One consideration is to pave with a permeable unit paver, or even unit pavers that are spaced to allow for drainage. There are also concrete erosion control products that lock together like a giant mat, which can be used to line channels, ditches and ramps on the property. Why should a contractor look at these systems for residential use? Simply put, responsibility. Large urban centers will have organizations and engineers who will drive the permeable pavement movement, but the "green" paving around the residences of our suburbs will rest on the design/build contractors for now until such legislation comes into effect. Rhode Island has already enacted such legislation, and other states are expected to follow.

One concern for contractors is the availability of options when it comes to permeable pavers. Fortunately, there are quite a few different styles available that can also be customized in color and texture. Exposed aggregate and "brushed' surfaces can provide many design options. The other concern for many contractors is information and training. Knowing exactly how the base should be designed and constructed is critical for a successful permeable pavement installation. As the "green" building industry matures, more information will become readily available to designers and contractors. For now, contractors can look to organizations like USGBC to learn about green practices, and to the ICPI (Interlocking Concrete Paver Institute) to learn about permeable paving specifications. Manufacturers of ecological pavers can also provide you with information and specifications. Those contractors who advance and promote themselves as responsible "green" contractors, will ultimately gain the respect of their clients and will be contributors to a sustainable environment.

Permeable Pavers

Unlike regular interlocking pavers that have a base of sand, the base and layout of permeable pavers allow water to soak back into the soil. First, the soil is prepared and topped with geotextile, which helps prevent water contamination. Then, a base layer of open graded compacted (no. 57) aggregate is laid down. On top of that is 1.5 to two inches of granular bedding material (no.8) that has zero plasticity and contains no number 200 size particles. The pavers are then installed and the joints are filled with more of the granular bedding material.

Building Blocks

75-92 -Percentage of metals (copper, iron, lead, manganese and zinc) removed from parking lot of the Florida Aquarium in Tampa through the use of porous concrete with a swale.

23-59 - Percentage of metals removed from the same parking lot using asphalt pavement with a swale.

Source: Low Impact Development (LID) Center

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December 15, 2019, 8:13 am PDT

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