Has anyone out there any experience of using an air lance for soil
excavation around tree roots?
I recall Daniel Zanzi (sp?) writing in the Journal of Arb. several years ago
about soil replacement around existing street trees in Italy. He used a high
pressure water system and if anyone knows of any follow up on the
benefits/disbenefits of the operation I would be grateful.
I am looking at the possibility of retro fitting (Hallo Nina) new soils
around existing trees. The literature search is underway, practical
experiences gratefully received.
Thanks
Richard Nicholson
rnicholson@eastdorset.gov.uk

Reply to post by Richard Nicholson, on October 03, 2001 at 09:10:14:

I've had a fair amount of experience using an Air-Spade to excavate tree roots as part of hazard assessment and tree preservation projects. It works quite well for both of these applications, and the greatest limiting factors are: Depth of excavation; soil moisture content; severely compacted soils; rocks.
I believe that pnuematic excavation is generally much less trouble than hydraulic excavation due to the fact that hydraulic excavation requires a vacume to remove slurry, whereas the use of pnuematic excavation simply blows the soils out of the trench. Pnuematic excavation is also less likely to tear away bark from the roots than is hydraulic.
For more information you can contact:
Rob Gross at
Dendrotech
P.O. 766
Calistoga, CA 94515
(707) 942-9139, or 8836

Reply to post by Matt Rivers, on October 03, 2001 at 09:10:14:

I'd add one question to Matt's reply. I have no first hand experience but as I understand it on a larger air excavation a vacume unit is desirable to collect and remove the excavated material. That's logical in you think about it... the soil will only blow so far and the accumulate. If that accumulation is withing the excavation boundary you have to move it again. The air-spade web site I believe shows vacume equipped units. The concern would be more an issue in your total soil replacement aoolication than in trenching or root collar examination.

Reply to post by Scott Cullen, on October 04, 2001 at 17:31:07:

On compacted poor soils i have found that I can fracture the soil with the airspade then do a topdress with a mor desirable soil to augment instead of trying to remove all of the soil from the rootzone.

If you are doing a small scale job, then putting a tarp down ad blasting the soil in that direction usualy works well.

We get 80psi off of the irrigation system and I tried using a 1 inch hose to do basal excivation, rather messy. the A/S gets a 35-50 in dhb American elm cleard 1 ft down 3 ft out in less then an hour, this includes trimming the mats of fibrouse roots that get in the way. I have 40 of these trees on my DED PHC program and am getting them ready for the macros next spring.

One little tip, for getting through sod, I find cutting 1 x 2 foot peices with the A/S and they pull out quite handily.

Reply to post by Scott Cullen, on October 04, 2001 at 17:31:07:

Yes, some assistance is required for the removal of loosened soils from deeper trenches or pits. A vacume unit is not needed in the truest sense, as this can also be accomplished with a shovel, or a bucket. I've not used one, but I understand that the bigger Air-Spades have a higher volume of air flow, and move more soil from deeper excavations more easily.

Great precaution is advised before removing large amounts of soil adjacent to large trees, as there is a potential for reducing the tree's stability.

Reply to post by Matt Rivers, on October 05, 2001 at 08:29:58:

A good point. I've seen somewhere recomendations (A-300?) where a basal exam is done a few feet out and then only do remidiation on 2 oposing 1/4 sections of the rootplate