[permaculture] Re: permaculture Digest, Vol 14, Issue 24

Albert Postema postema at nwlink.com
Sun Mar 21 10:08:16 EST 2004

Greetings mIEKAL,
re; alternatives to asphalt
Concrete or Brick, excellent for winter environments

If you look at the full life cycle of asphalt versus concrete, concrete will
come out on top due to its durability. It is definitely a considerable added
expense (2-3 times more) but it is a 150 yr plus installation versus asphalt
25 yr lifetime. This information is based on roadway use, where there is
heavy vehicle traffic, which typically is not the case in parking lots.
This is why you see our interstate system use concrete.

Concrete is sand, gravel, and cement.

This system is used all over in Europe. It has the added benefit of being
easily removed for later underground utility installation and or repair. My
experience is from Holland, where they use it extensively in cities, due to
underground repair aspects. Here in the states, I would expect the expense
to be at least the cost of concrete, due to the limited use, hence
unavailability of skilled contractors. In Holland they have created an
amazingly skilled workforce and process for laying brick. I have watched a
four man crew install 2500 sq ft in a day.

Again the base material is the key to longevity. Keep it dry underneath and
you will not get freeze heaving. (this is one of the reasons why we have
ditches on both sides of our roadways, keeps the watertable low)  There is a
porous concrete product that is starting to see some usage, due to the fact
that it eliminates runoff, but I see drawbacks. More oil is spilled each
year due to vehicle oil leaks than tanker spills. It is a sad fact but one
that bears considering. Porous means loss of containment.

I expect your parking lot is being installed with drainage and some sort of
runoff control. It is here that I see the greatest potential for getting the
most bang for the buck. i.e.; the low hanging fruit.  Oil water separators.
These are installed before the outlet point after some sort of flow control.
1750 - 4000 gallon concrete tanks with a series of baffles to allow for the
separation of contaminants from the water. Typical cost should be between
$3000 to $6000 dependant on flow volumes. There is also ongoing monitoring
and periodic replacement of oil absorbency booms.

Incidentally for those of you with smaller parking pads or catch basins,
there are some fairly inexpensive retrofit options that will provide for oil
water separation.
One online resource is at www.newpig.com

Albert Postema
Earthwise Excavation
Snohomish WA

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