Need information on root growth under roads - Water line coming

[kimsquared]

I am looking for research and documentation about the root structure of a tree in the following senerio:
-Black Locusts planted 1860 (an estimate) along a rural dirt road
-Road paved sometime before 1950 (still researching date)
-The center of these trees is 6′ from the edge of the asphalt
-4’5″ feet from the ground: circumfrence 120″, diameter 38″
-2018 a water line will be run down the middle of one of the two lanes of the road

The town contends that because there is asphalt on top, that the damage to the tree will be negligable when they trench for the new waterline. I contend that because the tree was mature long before the road was paved, that the tree roots extend beyond the other side of the street and are still critical to tree health. I am looking for research backing this up to include in a letter to the town. I want to insist that an arborist be present whenever they are working on a place on the road where one of these old trees remains. I can find research on many other facets of urban trees, but nothing on this scenario.

Thank you for your help. Kim

 

[JeffGu]

My guess would be that the trench will end up 10' ~ 12' from the trees on one side, an additional 10' from the trees on the other side. It seems unlikely that this would affect the stability of the trees, and equally unlikely it would do grave damage to any of them. Although that's still not an ideal scenario, it sure beats the alternative... trenching the water main in the right-of-way, which would mean removing the trees on one side. I certainly understand your concerns. Beautiful, old trees.

If this is replacement of an existing line, then the trenching done in the past doesn't seem to have adversely affected the trees... a positive sign. If it's a new line, then I have to assume there is a need for it that supercedes (in the minds of the town council, anyway) the risk to the trees. On a positive note, there are many places that would remove the trees and place the line in the right-of-way easement. The fact that they are willing to tear up the street and trench for the water line there, which makes any repairs to it more difficult and expensive, shows that they are concerned for the trees, as are you.

Having an arborist on hand to assess how much root damage is actually occuring is not an unreasonable request. They might be even more inclined to do that if you were able to locate a suitably knowledgable aborist in the area who would do this pro bono or for a low, fixed fee. Pointing out that it's good advertising for them to present a good image to the public, might help persuade such an arborist to do this.

I wish you the best of luck with this, as the needs of communities to expand their utility infrastructure can often run afoul of the trees that have the misfortune of being in the way. Regardless of the outcome, you can quite possibly convince the town council to have a backup plan in the event that the trees don't fair well... a tree replacement plan that would ensure that the pleasant, tree-lined road offers the same appeal to future generations. That's something the public can quite often get behind and support.