I would take a guess and say it depends on what side of the sidewalk the valve is on. If it's on the lawn side you can probably abandon the tree side with no problem.
Just find the pipe and cap it off. See what happens.
Or fix the leak.
Thanks!
The valve is on the lawn side. In fact, the valve and the controller are in the backyard of the house.
The leak would be hard to fix, since the tree is really mature and would probably require a lot of tricky digging.
How would I go about capping off the line and where?