Author: Libby Hanson

When I was first developing GraniteCrete, I knew the importance of replenishing our water table; how precious water is to our planet.  When we had GraniteCrete tested and found out it was permeable we were ecstatic. Not only did we have a green alternative to asphalt and concrete, but it was indeed permeable!

-Geoff Smith, President of GraniteCrete

GraniteCrete, as a company, stands as a leader in the permeable paving industry and a strong advocate for permeable paving. Traditional, impermeable surfaces—such as concrete—cause unnecessary erosion through runoff. They play a huge role in the decline of watershed integrity in urban and urbanizing areas.  Impermeable surfaces degrade groundwater quality, increase damaging streamflow, and even increase the likelihood of flooding. The evils of impermeable paving include:

• Higher discharge

• 

  Bank erosion

• Sediment transportation
• Increased pollutant loads in streams
• Runoff to lakes and the ocean
• Reduced groundwater recharge

Make It Permeable!

Fortunately, permeable paving solutions exist.  Permeable paving allows rainwater to percolate directly into the ground, reducing runoff and all of its associated problems.  Many outdoor projects that now use non-permeable paving (such as concrete or asphalt) could use a permeable solution to produce a better-looking, more environmentally-sustainable landscape.  While choosing a permeable paving option may require a little more research than choosing a traditional paving option, it is well worth it.

Permeable pavement comes with both environmental and financial benefits.

Environmental benefits include:

• Reduces storm water runoff rate and volume
• Reduces water pollution by trapping pollutants in the pavement
• Replenishes groundwater, which can in turn be used by plants surrounding the pavement

Financial benefits include:

• Reduces the need for some conventional drainage features, such as curbs and gutters
• Lower installation costs, since underground piping and storm drains are not needed
• Reduced water-usage costs, since surrounding plants can benefit from the replenished groundwater

So, where to even begin when it comes to selecting a permeable paving option?  There are several to choose from.

General Permeable Paving Products

Loose decomposed granite is the least-expensive option, as it’s simply loose granite with no binders or additives.  While it has excellent drainage and the initial cost is low, loose decomposed granite can be costly to maintain.  It easily washes away due to rainfall, or gets tracked away from the installation site (and into homes, which may damage hardwood flooring).

Stabilized decomposed granite is comprised of a stabilizer combined with the granite aggregates.  This provides the decomposed granite with varying levels of permanence, depending on the stabilizer used.  Unfortunately, not all stabilizers are permeable and some may allow environmentally-harmful materials to leach into the groundwater.

Permeable concrete is a type of concrete that uses only large aggregates (no fine aggregates or sand, like conventional concrete).  It has a high porosity, which allows three to eight gallons of water per minute to pass through one square foot. However, it does not have the same strength as conventional concrete due to the lack of fine aggregates and the high porosity.

Permeable asphalt is a type of asphalt that uses only large aggregates; the absence of fine aggregates creates “voids” in the pavement that allows water to flow through to the ground below.   Sometimes polymer is added to the permeable asphalt to increase its strength, which increases the risk that environmentally harmful materials will also filter through into the groundwater.

Permeable pavers are similar to traditional pavers, but are somewhat thicker, and rest atop layers of crushed stone.  They’re attractive and versatile, however, the pavers themselves are not permeable – only the spaces in between them.

Specialized Permeable Paving Products

GraniteCreteTM is an admixture that contains no polymers, oils, or resins; so, no unnatural materials will leach into the ground as water passes through.  GraniteCrete is mixed with decomposed granite to create the finished product. It has the look and feel of a crushed organic surface, providing a permeable pathway that is solid and durable with the near-strength of concrete.  GraniteCrete will stand up to both foot traffic and light vehicular traffic, making it appropriate for pathways, driveways and parking lots. It is also exceeds ADA-compliance, making it a great choice for commercial and residential use.

Gravel Pave involves a continuous piece of geotextile fabric laid on the ground, that helps hold gravel in place.  While water can pass through the gravel and the fabric, the gravel runs the risk of being tracked away from the installation site which can lead to increased maintenance costs, as the gravel will need to be filled in.

Porous Pave is made with the rubber of recycled tires.  It is highly-permeable, allowing water to easily pass through to the ground below.  However, the rubber material could allow environmentally-harmful materials to leach into the groundwater.

Armed with the information here, anyone can take the first step toward choosing an alternative paving solution that will not only increase the aesthetic appeal of their yard, but the health of the environment. We believe, of course, that for many projects GraniteCrete is the right choice – and we appreciate how many of you agree with us! See how beautiful GraniteCrete can make your landscaping project while earning LEED points and supporting the health of the environment.