Live Oak, Driveway Damage, Biobarrier Questions

[DRA]

Hello. I have a 27" DBH live oak tree that is located about 5' away from the driveway. (Live oaks of 35" or greater are protected by strict regulations.) During the past few years, the tree has caused increasing damage to the driveway and also lesser damage to the public sidewalk which has been sanded down by the county on one occasion to an acceptable level for the time being.

Because of my love for the tree, I have met with several arborists to try and determine what options there might be for preserving the tree and, of course, the driveway, too. The idea of applying for a permit to request county approval to remove the tree has also been considered, though I sense the odds of being approved may be low.

One arborist has suggested the option of installing Biobarrier by severing the tree roots to the depth of 12" for a total distance of 20' which would include the length of the driveway. However, a second arborist feels that cutting the roots is not an option, since the tree is so close to the driveway.

I am very concerned about the tree's future health and stability. Is Biobarrier a good option, and if yes, is the depth a good choice? Should the cut roots be treated to prevent invading disease?

I have been trying to do the impossible and determine how severe the driveway damage may become. I live where there's an HOA and driveway options such as replacing it, but changing its layout/design to avoid repeating this issue is not an option. Are there any other driveway options that you know of?

Any information that you can provide would be appreciated. Thanks.

 

[Raintree]

If Oaks of 35" plus are protected why a permit to remove a 27' tree?
I would second the 2nd Arborists feelings on the harmful root cutting idea.
Pics of the damaged drive would be helpful.
Trees growth can be slowed way down with growth regulators.
Raising drive grade can buy time.
Changing the surface material of the drive area affected by roots is a possibility.
Recommendation, cut & remove blacktop from area in question. Raise grade over roots with trap rock screenings. Leave as is or repave with oil & stone.

 

[DRA]

Thank you for responding. I just double checked the permit requirements. For trees with a 12" DBH or greater, a permit is required for developed residential lots, except for exempted trees which a live oak is not a part of. In the tree permit application, an arborist can submit their tree evaluation report for trees smaller than 34" DBH. Larger oaks have to be evaluated based on a natural resources staff visit. If a permit is approved for a grand oak, the tree must be replaced by one or two shade trees, depending on its DBH.

The driveway is concrete. I am doubtful that the HOA would approve a different type of driveway. The driveway also cuts through the sidewalk, so raising the grade could be an issue.

I just spoke with another arborist who thinks that air spading and finding the offending root(s) would at least minimize the root damage. He didn't mention root barriers, so I would imagine the root issue would return in time.

Thanks again.

 

[DRA]

Hello again. Does anyone have thoughts about the idea of installing Biobarrier in incremental stages to help reduce the shock to the tree? Another option being proposed is installing 10' of Biobarrier with a fungicide to treat the cuts, and then three months later, install another 10' Biobarrier. Thanks.

 

[treeseer]

As Rantree said, without a picture it's hard to advise.

Excavation by air or shovel seems like a good start, to find the offending root(s). Only then do you know your options.

 

[sac-climber]

Airspade is a great option. I deal almost daily with consults regarding root encroachment and excavation is really the only way to know exactly what your dealing with in sensitive situations like yours. If you love this tree do what you can to preserve it, even if that means tollerating some damage. My ending question to clients facing the choice of removal or mitigating damage is, "how much do you love this tree"? You may end up spending far more to preserve it than to remove and replace it so you need to evaluate if that's the road you want to go down.
Do post some pics for us though. I'm looking forward to following this thread.

 

[Toddppm]

Airspade to see what's going on, cut the offending roots and build a stronger reinforced driveway. At that point if it dies, they can't deny you a removal permit.

 

[Raintree]

Cutting large driveway heaving roots 5ft off a 27" Oak's stump, one may find that side of the tree wilting. Not to make note of destabilizing the trees anchoring system during a wind event.

 

[Toddppm]

Maybe? 27" isn't that big and we don't have any pics yet.....I'm betting the driveway is only a couple inches thick too.

 

[sac-climber]

Cutting large driveway heaving roots 5ft off a 27" Oak's stump, one may find that side of the tree wilting. Not to make note of destabilizing the trees anchoring system during a wind event.

I'm with RT here. Cutting anything more than 6" that close to the trunk is a big no-no in my book. I just handled a case where landscapers removed 12"+ roots less than 3' off the trunk in order to replace a sprinkler head. 60' Sycamore on an irrigated 35 degree slope facing a major roadway. Not a good situation.

I know that DRA's tree is not in a similar situation. Just thought I'd share.

 

[treeseer]

"You may end up spending far more to preserve it than to remove and replace it."

I hear this a lot, but the math seems to go the other way. Remember, a 27" tree is worth a lot of money; how much would it cost to grow one back in that place?

 

[sac-climber]

"You may end up spending far more to preserve it than to remove and replace it."

I hear this a lot, but the math seems to go the other way. Remember, a 27" tree is worth a lot of money; how much would it cost to grow one back in that place?

I say it because it's the truth, I don't use that as a blanket statement. A replacement tree comparable in size is generally not even an option for most people to consider. Mitigation of risk or damage is often a life long commitment and investment. Often a costly one when executed properly.

 

[treeseer]

"A replacement tree comparable in size is generally not even an option for most people to consider."

My point exactly. If it's not comparable, it's not a replacement is it? Unless you're fine with losing $20 out of your pocket and having that "replaced" with $2.
So removal and replacement costs way way more than maintenance. .

" Mitigation of risk or damage is often a life long commitment and investment. Often a costly one when executed properly.

I've found the opposite: Once an old tree starts growing downward, it may be on a 5+ year mtc. cycle, delivering more benefits per mtc. $ than any other life stage. This based on managing some hollow trees 20+ years; how long a timeframe are you talking about?

 

[sac-climber]

"A replacement tree comparable in size is generally not even an option for most people to consider."

My point exactly. If it's not comparable, it's not a replacement is it? Unless you're fine with losing $20 out of your pocket and having that "replaced" with $2.
So removal and replacement costs way way more than maintenance. .

" Mitigation of risk or damage is often a life long commitment and investment. Often a costly one when executed properly.

I've found the opposite: Once an old tree starts growing downward, it may be on a 5+ year mtc. cycle, delivering more benefits per mtc. $ than any other life stage. This based on managing some hollow trees 20+ years; how long a timeframe are you talking about?

Seems we've got off to a rough start treeseer. I'm not trying to assert or suggest that my knowledge base is superior to yours. I'm trying to provide insight from my perspective, not have a pissing match about trees.

What it really boils down to is what the client wants to happen. They might be fine replacing with 1" nursery stock and just be happy not to worry about their driveway anymore. Landscape and tree appraisals really are arbitrary values (and yes I do plenty), with the exception to courts and insurance companies. This tree might have more value as fuel then it does standing in its current situation. IDK, I haven't seen it.

Regarding your second point; if the guy/gal doesn't want the tree removed and is left with the option of raising the grade of the driveway, having cracks ground and patched every 2-3 years, etc. I promise that will cost more than removal. Replacement of something similar in size is irrelevant anyway, the location is clearly not suited to transplanting a large tree.

I'll just leave it at that.

 

[Raintree]

If I were the consulting Arborist in this case with my license & reputation on the line. I would advise the Homeowner he has 3 options. 1) do nothing. 2) raise, rebuild the drive 3) remove the tree. No way would I have my crew cutting big roots that close to the stump. Not going to have some other Arborist in a liability lawsuit point the finger at me & say you should have known better. Even with a hold harmless agreement signed by the owner, not going to happen, I'll pass.
What I would do is write up a detailed report on why this Oak is a liability with a recommendation to remove. Send it to the HOA putting the ball in their court, requesting a written response.

 

[sac-climber]

If I were the consulting Arborist in this case with my license & reputation on the line. I would advise the Homeowner he has 3 options. 1) do nothing. 2) raise, rebuild the drive 3) remove the tree. No way would I have my crew cutting big roots that close to the stump. Not going to have some other Arborist in a liability lawsuit point the finger at me & say you should have known better. Even with a hold harmless agreement signed by the owner, not going to happen, I'll pass.
What I would do is write up a detailed report on why this Oak is a liability with a recommendation to remove. Send it to the HOA putting the ball in their court, requesting a written response.

Bingo! Those seem to be the only logical options. Do nothing or removal being the most logical of the three. I'm not typically an advocate of removal but if damage cant be tolerated and mitigation is too costly or not feasible for whatever reason then that leaves you with one choice.

 

[treeseer]

I'm hearing some rather certain ideas of how much a small dose of root pruning tends to destabilize a tree. What are these opinions based on? Data, or fear?

Read the journal for work by Smiley et al. At the Biomechanics site, trees lost buttresses at the flare and only lost ~20% holding strength.

It NEVER boils down to remove-or-replace. There is always the option of arboriculture. We prune big branches all the time, but freak out about pruning roots? Not logical. Of course, crown pruning could mitigate any root pruning.

The OP could answer all this in 5 minutes of shovel work. Why is subterranean also subconscious?

 

[Raintree]

I'm hearing some rather certain ideas of how much a small dose of root pruning tends to destabilize a tree. What are these opinions based on? Data, or fear?

We are only speculating since we have not seen pics of the situation in question. By the description of the OP this Oak is at the drive entrance near the side walk. With road & walkway hindering root zone street side, thus the remaining root area becomes that more crucial. Saying that eliminating an other side of the box (under the drive) is just a small dose of root pruning is difficult to comprehend.

Read the journal for work by Smiley et al. At the Biomechanics site, trees lost buttresses at the flare and only lost ~20% holding strength.

Attended many of Dr. Smiley's seminars, the bio-mechanics of trees will differ wildly from species, regions, ground conditions & out side forces. In the real world if you knew by your actions you would be responsible for as little as 20% strength loss. On a large tree in a high traffic area would you take the action? Once you make those root cuts, you now own the tree in question for the foreseeable future.

It NEVER boils down to remove-or-replace. There is always the option of arboriculture. We prune big branches all the time, but freak out about pruning roots? Not logical. Of course, crown pruning could mitigate any root pruning.

Dealing day in & day out with tree customers that have very limited resources, it often boils down to remove & maybe replace. There is always an option for common sense and doing the right thing for a continuing relationship with your client. Wounding a healthy tree & inviting decay & the possibility of Phytophthora is not good arboriculture. Comparing pruning off a large limb to cutting a equal size root is not logical, nether is compensating with crown reduction pruning.

 

[treeseer]

"Limited resources" is right behind "Check's in the mail!" as popular misstatements.

Why is subterranean also subconscious? If "own the tree" indicates a liability concern, that's what i meant by "fear".

You're right -- without knowing where what roots are this is nowhere--5 minutes with a shovel would sort it out.

 

[Raintree]

"Limited resources" is right behind "Check's in the mail!" as popular misstatements.

Next time when I present my lavish grandiose arboricultural proposal to my clients, detailing the extravagant work needed on their properties. If they have the assiduity to inform me that due to lack of funds the project will have to be scaled back. I will sarcastically state, " Yeah & the checks in the mail."

Moving on.