Water damage, Neighbor concerned repair may damage tree, zero lot line

[Jelly23]

What is the name of your state? California

I occasionally get water coming in to my family room and garage. This only happens after several days of heavy rain. The water is coming from the saturated ground, and only on the side that is next to my neighbors. Our house, in the front and back, is 97% concrete on that side. (Small gap for a hedge to grow through)

We have a zero lot line with a five foot easement. The neighbor has two or three tall palm trees in that easement next to our foundation. We want to inject a polyurethane foam into the ground all along the foundation on that zero lot line. This would create a below ground water proof barrier, and would be done without having to remove his trees. This product is safe and rated OK for drinking water. But neighbor is concerned and wants me to pay if a tree dies, or wilts, down the road. Note that the foam only expands two feet.

The easement does allow flowers, plants, and lawn, in the easement, but no permanent installations, and trees are not mentioned. Also, there is a drain that exits his property onto mine, that is not draining. The drain is underground, so we don't know what it should be doing, or where it actually goes. There is a chance if the drain was working that I would not have these water issues, since they only happen with many days of heavy rain.

So, am I responsible for his trees? Is he responsible for any cost of repairs, as I do have water damage beside the cost to fix future water intrusions. Can he block me from doing repairs? Would it legally be better, or the same, if I destroyed the trees by just putting in french drains? (I thought I was being nice by finding this solution, but most companies recommended the french drains.)

Edited to add more verbiage from easement regarding plants, and easement use of "permanent installation".

 

[Zigner]

A tree is a "plant".
If you are certain that no damage will done to his trees, then agree to it. If your procedure DOES damage the trees, then why should't you be responsible anyway?

 

[Jelly23]

The easement does state no permanent installations, and gives a few examples. It does state lawn, flowers and plants are allowed. And later it mentions we have access to do maintenance. I think the intent is nothing major that would block our ability to do maintenance. So replacing small plants is no big deal, but a large tree is. These tree could cost $20,000 or more each to replace. And is a large tree a permanent installation, as trees can be cut down and buildings can be torn down also?

What we are injecting is drinking water safe, so is safe to be used around trees. So I don't expect the tree to have problems right away. But this could block the tree from getting water from under our house, as it is a water barrier. Thus no guarantee that it will still get enough water. Also if a year or two from now the tree dies, unrelated to this, they could blame me.

The contractor will take before and after pictures, so above ground there will be no visible change.

Also, don't I just have a right to cut any roots that enter my property? Wouldn't this be similar. But instead of cutting, I am encapsulating just the roots right at the foundation of my property, the zero lot line and within the five foot easement.