Trenching damages Douglas Fir roots

Lute82

Recently, a developer in my city damaged a portion of the roots to a 60 foot tall douglas fir tree. The damage was roughly 10 to 30 feet from the trunk and represented an area less than 25% the circumference of the tree's root system.

Assuming the damage places the tree in jeopardy, how long would it be until the tree was a safety hazard? Is there any chance it could be an immediate safety issue?

The damage was related to grading for a driveway. I believe they never went more than 2 feet deep, possibly less than that.

Thank you.

treeshaveneeds

A pic would help immensely.What were the soil conditions? and what did it get regraded with -- gravel, sand, concrete, asphalt?

At 10 feet from the trunk, the damaged roots will likely not cause catastrophic failure unless the root system was growing very unusually. This is where a pics of the tree, the site, and the damaged area would all make formative opinions substantially easier to give. Digging down 1 to 2 feet would likely sever any roots in that area.

Eric Frei

This calculator will give us the numbers we need.

Use it to give us the CRZ, TPZ, total circle area and segment area affected.

Online Calculator for TPZs and SRZs as per AS4970-2009

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Lute82

Here is a link to an article with several pictures:

City of Edmonds probing tree damage involving ex-Golf Savings Bank CEO | My Edmonds News

dcarter

Slower growing the tree species, the longer to see the damage usually. Also, it usually takes some time (months to years) to see damage in older, mature trees due to the length of time for travel from root to leaves. (That's why foresters don't pay for fertilizer on mature forests--not enough yield to measure to make it worth the money. --Next, if a driveway is being put in that place I'd worry more about soil compaction issues than root pruning from the trencher----which brings me to another question. Trencher or excavator?? which was it and was it 10 feet or 30 feet, pics would definitely help.

Lute82

The root cutting allegedly occurred without city permission on Monday, June 28, after a representative for the contractor had visited City Hall asking how they should handle an apparent conflict between a large tree located on city right of way and development plans for the construction project, City Engineer English said.

City Staff at the counter told the contractor's representative it would have to be investigated, English said. The next morning, city engineering staff went out to the site and discovered that the contractors had already cut a significant amount of tree roots in preparing to build the driveway entrance to the development.

They had been given specific instructions not to proceed but they did anyway, English said.

At that point, the decision was made to allow the removal since the tree was now a safety hazard.

One of my main questions is how could the tree become an immediate safety hazard because of something done to a portion of its roots?

Garry Brockley

Quite simply cutting the roots can 1. destablise the tree and cause it to fall over in a strong wind, 2. cutting the roots can kill the tree, it allows fungi and bacteria to enter the tree through the severed root wounds and these can kill part or all of the tree, 3. by cutting the roots you are taking away its ability to absorb moisture and nutrients through the roots therefore reducing the trees food and water intake by a minimum of 25% as you dont know exactly what percentage of the root zone was damaged it could be as much as 50%.

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