My yard was installed when the prior owners built our house a dozen years ago. They did a decent job with the landscaping and yard. The problem is that some areas of the yard have settled and I'd like to "fill" those areas in without redoing too much of the yard.
The most obvious place where this has happened is where the water main comes into the house. If you look closely, you can see that the yard has a small "dip" in it the entire run from the house to the street where that pipe runs. The dip is small enough that it seems like a speed bump when pushing a lawn mower over it and never looks just right when mowed.
I'd like to fill in this dip or trench without needing to reseed the whole area, because the grass is fine on top; it's just not level.
Can I just add topsoil slowly so the existing grass will continue to grow? Or do I need to dig up the existing grass like sod and add new dirt underneath the existing root structure?
Is there anything else I can do?