Sewer line in neighbors yard need repair

[Jonathan Halverson]

I have a 3 unit rental property in Highlands, TX, just outside of Houston. I've had some issues with the plumbing backing up and have had the sewer line snaked a few times. It now looks like a portion of the sewer line needs to be replaced, but that portion is apparently in my neighbors yard. It appears my sewer line ties into my neighbors before it ties into the city system. My neighbor is not allowing a plumber to dig up his yard to replace my line. Any suggestions on how to proceed? It seems I should have access to repair my line, but my neighbor is making it difficult. My property manager has offered to pay him $500 to allow us to dig, but to no avail. I plan to contact the city water district and possibly a real estate attorney, but wanted to reach out here as well. Another option would be to reroute my sewer line from the back of the property to the front and tie into the city system there, but that would involve road work and I assume a lot more expense. Appreciate any input you have, thanks!