Will the weight of a large excavator damage tree roots?

[ChicagoPete]

Hi looking to learn what I can here. We are putting installing a in ground pool next week at our home and there is debate from the pool company and my neighbor on the weight of the excavator running over the lawn between 30 foot tall trees and damaging their roots. I know nothing on the subject and I do not want to damage any of the trees on out yards, I already took down several last fall for this project. The salesmen said oh no problem coming in between the houses with equipment and near some trees, but now that the deal was signed; the man running the excavation crew was saying the equipment is quite heavy and much larger than the backhoe I was under the impression they would be using. Any advice would be really helpful and appreciated. Thanks!

 

[ATH]

You need to protect the soil from compaction if you want healthy trees. It is not the least bit unreasonable to expect them to do that as part of the job...at least in my opinion! There is an ANSI Standard (A300-Part 5) that will help - especially along with the corresponding Best Management Practice guide.

There are a few factors that come into play:
*Soil texture (clay compacts easier than sand...but even sand can be compacted)
*Soil moisture (wet soil compacts more than dry)
*PSI of equipment on the ground. An excavator usually has such large tracks that it is less than rubber tires...but that doesn't mean there is none!
*Number of passes. One pass with one piece of equipment on dry sandy loam soil is probably not causing a problem...but after just a few passes you quickly lose soil structure and compaction can be significant.

A few things you can do to reduce compaction:
*Limit equipment allowed to drive over the roots. For example: Not every contractor needs to drive their pickup truck back there every day. They can walk. Or, if they have heavy tools they need in a truck, consolidate them all into one truck.
*Protect the ground:
--One good way to do this is with an 8-10" layer of mulch (coarse is better than fine). Plan to remove this after the work is done - and make sure they are ON the mulch as they remove it!
--Mats (such as 3/4" plywood or AlturnaMATS) can be used for driving on. These are great for an area they will only drive over a couple of times (or days). If they are going to be back and forth a bunch over a couple of weeks, mulch may be a better solution.

You may also see if there is another way to get to the site. Sometimes a relatively minor inconvenience now will save a lot of headaches (tree removal, mad neighbors, loss of shade from dead trees, etc...) in the long-term. That applies to all of the above suggestions. Yes...they are inconvenient, but so is removing trees later.

 

[ChicagoPete]

ATH, Great Info! Thank you very much!! Were going to have them cart in the stone, need to look into how they're planning on doing the concrete. Thanks again!

 

[beastmaster]

ATH gave good advice. I would listen to it Compaction is easier to prevent then repair. The harm can take years to show.

 

[ChoppyChoppy]

How big of a machine?

A large excavator to me is likely not something that would normally be digging a homeowner sized pool. Talking in the ~50 ton and up range.

Even a "medium" sized machine, like a 200, is still around 16-17 tons.

I'd guess it's actually a mini-excavator and not a std sized one? That'd be logical to use for putting in a small pool anyhow.... so 4-6 ton area.

 

[Marshy]

A concrete truck is going to have more impact than an excavator.

 

[beastmaster]

It's the air pressure in the tires more then the weight of the machine.

 

[ChoppyChoppy]

It's the air pressure in the tires more then the weight of the machine.

I think the word you are looking for is ground pressure.

An average person is around 15psi,

Most dozers, excavators, etc aren't even 1/2 that. The wide pad stuff is often labelled as LGP... Like a Cat D6 LGP for example.

Not sure what a concrete truck would be at.

 

[Skeans]

Heck we run on tree roots all the time thinning, as long as the root isn’t exposed or doesn’t get barked up it should be fine.

Upwards of 50k on the ground there with a decent amount mainly on the rear bogie.


Sent from my iPhone using Tapatalk

 

[Griff93]

This kind of damage may take 5 to 7 years to show itself.

 

[northmanlogging]

Excavators tend to have less ground pressure then even much lighter tyred machines.

Just really need to take care not to scrape standing trees and roots. Even then they will likely be fine.

What normally causes damage from excavators is digging and disturbing of the root system, or worse burying part of the trunk.

In reality trees put up with some severe abuse and live through it

 

[Skeans]

Excavators tend to have less ground pressure then even much lighter tyred machines.

Just really need to take care not to scrape standing trees and roots. Even then they will likely be fine.

What normally causes damage from excavators is digging and disturbing of the root system, or worse burying part of the trunk.

In reality trees put up with some severe abuse and live through it

That’s not always true the newer wheel machines with the tracks over the tires will have half the ground pressure.


Sent from my iPhone using Tapatalk

 

[northmanlogging]

Tracks... over tires, equals tracks

 

[old CB]

When the PSI might be intolerable, a good operator will build a road of 3/4" plywood or similar. Your local folks hopefully understand the issue(s). Tracks better than tires, reduced PSI footprint.

But too many variables for anyone to address from a distance. Some soils--sandy gravel mountain soils where I live, for instance--don't know a thing no matter what you run across them. Other places--deep prairie loam, maybe what you have--especially when saturated, you could have an issue.

But I'm with Northy--healthy trees stand up to more abuse than you'd think they should. Healthy soils, healthy trees, a healthy environment--like other healthy organisms--will withstand some abuse. It's when you have organisms already stressed by other factors that such short-term damage as ground traffic causes real damage.

 

[BC WetCoast]

It also depends on the tree species. Some species do not like having their roots mucked around with, others are more tolerant.

As stated above, it's not the damage to the roots that will be the problem, it's the compaction of the soils. Root cells, like other living cells of the tree respire, that is need to transfer air into the cell and waste products out of the soil as part of cell life and growth. If the soils get compacted, then there is no air in the soil pores (because there's no soil pores) for respiration with the root cells to occur.

 

[TheTreeSpyder]

Reference mental benchmarks over the years: Have read intelligent references on
>>hard rain disrupting soil life
>>trees in clumps protecting soil space from large animal travel from all side, even in death for the rest
>>when planting tree, shovel itself can glaze hole somewhat enough for the b
>>life needs air, except nasty anaerobic , air only travels so deep, essential is the easiest to hurt top layers
>>sea of life in soil is well developed system, mychorhizae is delicate and amazing link, we even are trying to now mimic it's networking strategies and redundancies in computers!!
>>if take live dirt from hole, put on tarp and pour all back doesn't fill hole. Live soil is half air space in running stratified caverns and passes of gas, water and nutrient exchange teaming with life

Thus the compaction etc. from above ground we term as construction, is definitively the opposite in the soils that scurry to compensate as we compact and compress the life from it
Especially in drip line, then the extensions of which trying to encourage stabilizing wide, weighty underground to also encompass more soil to stabilize tree.
Short math is our kings of the jungle are Thee self -maximizing life form that made the planet land habital as we know it, for millions of years before us, and probably did better w/o us