When I started my small garden plot last year, I was appalled at the state of the soil. Looking back at the blog post, I didn’t say much about it, but I recall loosening the soil and discovering a thin layer of topsoil over greasy red clay. I worked some leaf compost into the plot and went from there. I also noticed that in digging up the roughly 80 square feet of garden, I found only a couple of earthworms.

At the end of the growing season last year, I seeded the plot with crimson clover as a green mulch and leaf mulched the swiss chard in hopes of having some of it survive the winter. This spring, when I started planting, I noticed that the soil seemed much healthier – black and a bit deeper, and nicely crumbly. Most excitingly, when I was digging up some of that weird 6-leaved running ground cover that had crept in from the edges, I found that I couldn’t lift a spade of soil without turning up at least one earthworm. Fantastic!

More on porous asphalt

I posted a quick note earlier about installing porous asphalt in a green community in Oregon. In that note, I made an offhand comment questioning the water quality coming off the road. After posting the article, I also wondered if the lifetime of the surface would be shorter in areas prone to freezing weather due to the expansion and contraction of ice in the pores.

It turns out that had I been less lazy in doing my research, I’dve had all these questions answered much more quickly. I just found a great article on porous asphalt that covers a lot of topics, including water quality (82% removal efficiency for organic carbon) and lifetime in freezing weather (longer than standard asphalt).

Additionally, the article points out that the porosity allows for less use of salts for deicing and that:

The water drains through the pavement and into the bed below with sufficient void space to prevent any heaving or damage, and the formation of “black ice” is rarely observed. The porous surfaces tend to provide better traction for both pedestrians and vehicles than does conventional pavement. Not a single system has suffered freezing problems.

Pretty darned cool, if you ask me. One has to ask what the factors are that are keeping this from being installed in every new parking lot being built. Undoubtedly, the subsurface strata affect the design – this is also covered in the article – but I suspect strong that the major factor is simply ignorance.

On a lighter note, the best quote from the article is this one: “Fortunately, even without regular maintenance, the systems continue to function (we routinely send graduate students and recent hires out in hurricanes to confirm this).”

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Porous streets

After reading this post from WorldChanging, I wondered a bit about the wisdom of porous pavement. Sure, I understand the issues that are caused by stormwater runoff, but I’m a little concerned about what gets washed off the streets through the pores in the pavement.

There are probably good ways to handle this, including beds of Stropharia mushrooms on either side of the road to mycoremediate the waste water stream or even a filter layer underneath the pavement.

I also wonder what is actually underneath that pavement. Is it the sand and gravel bed that typically underlies roadways? Or is it something else more porous? The percolation through a layered gravel bed might reduce the pollution in the water that passes through.

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