asphalt drive removal.

Dennis49(9)November 8, 2013

I'm removing an old asphalt driveway. It seems that under the asphalt is a layer of oily emultion & dirt that's approx. 3/4 inch thick. After removing both of these do I need to remove any more dirt, or do anykind of treatment, before amending the existing soil and planting trees, shrubs and lawn?

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If you can get down to dirt, then I'd say you're okay. If it were mine, I'd double dig down to 12+ inches just to eliminate the compaction, get some oxygen into the soil, etc. And while I was at it, I'd till in a whole buncha organic matter into the top 6 inches (or more).

It's probably wise to get a soil test (pre ammendments) to see if there are any ph issues, etc. I'd do one for the existing lawn + one for the new site if it was me just to compare. (So if you needed to add lime, it's easier to do so when you're already tilling stuff in rather than just topdressing.)

If it were a veggie garden, I'd consider getting the full-blown test to make sure there aren't any bad metals, chemicals, etc. that might be from the asphalt. I don't know if that's even a possibility; I don't know what sort of work goes into putting down a driveway.

If it's just lawn & shrubs, I'd get a soil test, follow their recs re: ph, etc., double dig it to un-compact it, till in a buncha compost, seed, fert, straw, water (a little, very often at first, then dwindle it down gradually over weeks--changing to light & frequent to deep and less frequent), and then proceed to curse the weeds that sprout in the middle of your new fescue. :-)

    Bookmark   November 8, 2013 at 10:39PM
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Any properly constructed paved driveway, Asphalt or concrete, the base will be a packed minimum of 6 inches of aggregate (stone) and that will need to be removed as well. Anything less means the drive will fail much too soon. It may look like that base is only 3/4 inch thick, but I would not rely on that.

    Bookmark   November 9, 2013 at 7:02AM
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seysonn(8a WA/HZ 1)

You have a lot of digging and tilling to do.
Depending on the type of native soil, you will need to ad a combination of topsoil, manure and compost, till them into the native soil. IMO, you will need a minimum of 12" deep good soil to start. Then you will have to add more following years to bring it up to par.

As suggested , a soil test is in order, to know exactly what the condition of the soil is, what the pH is, what is lacking..etc.
Otherwise it will be like shooting in the dark.

    Bookmark   November 9, 2013 at 8:10AM
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seysonn, define what you mean by "topsoil". "Topsoil" is the top 4 to 6 inches, or per some sources 12 inches, of soil form someplace and that term has no more meaning then does "garden soil". A person may get something worthwhile when they buy some "topsoil" or they may get junk, but mostly what I see peddled as "topsoil" is not much of anything. Also what passes for "topsoil" in the northwest will not be the same thing in the southeast or the northeast or the southwest.
People can make their own "topsoil" by adding organic matter to what they have and that would be a better investment of time, money, and energy then something as specious as "topsoil".

    Bookmark   November 10, 2013 at 6:53AM
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nil13(z21 L.A., CA (Mt. Washington))

c'mon kimmsr, when someone takes out a driveway they are going to be looking at a big trench with exposed subsoil. For that they are going to need fill to at least bring the soil level to grade. That fill should, except in rare circumstances, be a local topsoil like a 70:30. Now sure, they should get the best they can find. But when you're looking at a hole that big, simply carting in some organic matter isn't going to cut it.

    Bookmark   November 10, 2013 at 11:58AM
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Asphalt driveways seldom have crushed rock bases - typically they are laid directly on graded soil. If the asphalt has been removed plus whatever sludgy material that may be lurking underneath, I'd say you are good to go. Obviously, if that compacted "6 inches of aggregate" isn't present, there's no need to remove :-))

I would also be concerned about compaction. Importing enough soil to bring to level and then tilling the addition into the existing subsoil would be my preferred approach but it depends on what you are planting and how much soil you needed to bring in. In a lot of cases, the plant material will do the 'decompaction' quite efficiently itself, with the roots penetrating down and breaking up the soil.

I think sometimes we get too wound up in the semantics of term 'topsoil'. Hardly anyone sells real topsoil any more unless it is the land developer selling to the bulk soil distributor. But in many cases, even the topsoil from new developments stays in just gets moved around with grading and filling/leveling. Purchasing a soil mix - even those labeled as "topsoil" - from a bulk soil provider will generally get you a pretty decent, well-draining and semi-fertile planting medium that's good for just about any gardening purpose. It's the bagged stuff that I find tends to have the most issues, plus it is far too expensive compared to buying in bulk.

    Bookmark   November 10, 2013 at 6:26PM
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wayne_5 zone 6a Central Indiana

While finding really good topsoil may be the exception, a few years ago a local dealer bought a field of 7 or 8 acres and skimmed off the topsoil...I got some of that to fill in a few inches of a place I had.

    Bookmark   November 10, 2013 at 6:38PM
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seysonn(8a WA/HZ 1)

Posted by kimmsr 4a/5b-MI (My Page) on
Sun, Nov 10, 13 at 6:53

seysonn, define what you mean by "topsoil". "Topsoil" is the top 4 to 6 inches, or per some sources 12 inches, of soil form someplace and that term has no more meaning then does "garden soil"

Not any soil brought from someplace, is considered "Topsoil"

Here is my definition of "Topsoil":

"Topsoil" generally means an accumulation of organic matter over a long time that is partly mixed with and has changed a layer of the INorganic soil underneath. This happens in the woods and prairies etc. INORGANIC soil is debries from the rocks produced over time, which may have sandy .. or clay .. quality.

ALTERNATIVELY: one may haul soil from an established farmland that has been conditioned. That is also considered topsoil.

    Bookmark   November 11, 2013 at 12:43AM
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To quote from the article linked below,
"Myth #1: Topsoil means that it is going to be good, dark and rich soil.
Balloon popper: There is no legal definition of the word topsoil. Technically, it is whatever is on the top. Sight unseen, you could order 5 yards of anything from beach sand to adobe brick material. Always go to look at what you are buying if you are unfamiliar with the soil seller to know what you are purchasing."

If someone is going to buy soil they should have a good idea what they are looking for and not some undefined substance called "topsoil". A good soil to buy would be one that contains about 45 percent sand, 25 percent clay, 25 percent silt, and 5 percent organic matter.

Gardengal, if someone actually did lay down asphalt as you described they would experience very rapid failure. No paving contractor I know would even consider laying a driveway in that manner.

Here is a link that might be useful: The truth about topsoil

    Bookmark   November 11, 2013 at 6:30AM
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I would not worry about analyzing for toxins. Even if you did not have a thick crushed rock base underneath, removing the hardened asphalt and one or two inches of that oily layer underneath will be fine. The sub layer may be an oiled gravel/dirt driveway that was there before putting down the asphalt.

Asphalt does have potential toxins, including polycyclic aromatic hydrocarbons (PAH), but they do not leach down into the soil very well due to their low water solubility and the massive solid nature of the asphalt matrix. So, if it's visually gone you're OK, even for vegetables. If the dirt underneath was oiled, such as with used motor oil (they used to do that in the old days), the same applies. It's a little more mobile but if you can't see or smell it, there's not enough there to be a problem.

    Bookmark   November 14, 2013 at 1:40PM
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Thanks to all who replied. Lots of good info.

    Bookmark   November 20, 2013 at 10:48PM
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