Our garage currently pops you out onto subsoil for our driveway. We have erosion problems that might be corrected by the creation of a berm this summer but Papa wants to bring in road base and pour a 25′ pad. (Our driveway is around 100′.) The backyard is a wasteland of volunteer plants even though we use it constantly. A patio starting at the walk-out basement’s door would be wonderful for BBQs and driving around the Plasma Cars.
Using concrete is the most obvious and ubiquitous method for paving a driveway or creating a patio. For me, there are a number of problems.
- Land-use and exploitation of natural resources (excavations, quarrying, ground water, limestone). 10-11 millions tons annually world-wide of sand, gravel and crushed rock.¹
- Waste products from production
- Emissions (CO2, SO2, embodied energy throughout production, transport and construction)
- High embodied energy
- Heat reflected back onto building during summer
- Increased water run-off
- Increased erosion downhill of the concrete
Any material we use for the driveway pad needs to stand up to constant traffic. The patio would be a tad easier, as it doesn’t need to support a vehicle intended for anyone over the age of 12. Grass in Colorado is a no-brainer for me. It grows too slowly, takes constant care, looks awful during the winter and would become a soupy mud mess. No Thank You.
Today, I’m researching alternatives.
Bruce Ferguson, professor and director of the School of Environmental Design at the University of Georgia in Athens has identified nine categories of porous pavement. Six of these could be used for our driveway and patio.
Open-celled paving grids are open spaces with ribbing in between. A potential disadvantage is that they can be difficult to walk on, Ferguson observes. Turf needs time to grow over the grids and open spaces, and then they can work well.²
Open-graded aggregate is “the most permeable material and the lowest cost material you can get anywhere, including conventional dense asphalt.”²
Using road base for the driveway is a possibility but Papa wouldn’t be happy. He does all of our vehicle work and his back wouldn’t like to lie on rocks.
Gravel driveways look great when first installed but after time the gravel moves and compacts into the sub-base. This results in ruts and potholes requiring ongoing maintenance and more and more gravel. –EcoGrid
Open-jointed paving blocks are segmental pavers that bear enormous traffic. These pavements can handle high weights and perform in a variety of climates.²
Plastic geocells are plastic cells held together with ribs and filled with aggregate or turf.²
Plastic grid is a product that virtually eliminates erosion due to water run-off. It can be filled with gravel or soil, which is then over planted. I browsed through the Terrafirm Enterprises and InvisibleStructures websites. Both of their products are a few inches deep and can be finished off whichever way you prefer. There’s a good run-through at HGTV, if you’d like to take a look.
Porous asphalt was developed around 1970. The most widespread use of porous asphalt today is as an overlay on interstate highways.²
Pervious concrete is created by mixing water and cement-like materials into a paste that forms a thick coating around the aggregate particles, according to Pervious Concrete Pavements, published in 2004 by the Portland Cement Association. This mixture contains little or no sand and forms a system of “highly permeable, interconnected voids that drain quickly.” Pervious concrete is advocated as a best management practice (BMP) by the EPA.²
Other ideas: Pavers would look stunning and completely out of place for the driveway. Their embodied energy would be similar to just pouring concrete. They’re also much too much expensive for our budget. Two concrete strips are the driveway of choice where I grew up. The grass gets smooshed on the sides, the strips compact into the soil and the center is mud central. I also don’t think the children would be very accurate on aiming vehicle wheels once they begin to drive.
What will we use? I don’t know. For me, it comes down to cost and environmental impact. For Papa, it’s mostly about the cost. I’ll keep you posted as we make decisions.
Sources:
- Reducing the Environmental Impact of Concrete – Concrete International Oct 2001
- Advances in Porous Pavement – Stormwater, the Journal for Surface Water Quality Professionals
Photo Credit: Chris Blakeley CC Licensed Image
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