Expect the plumber to clear the line and run a camera from the basement cleanout toward the tank, recording where roots, offsets, or breaks appear and how far they sit from the foundation. They may also open the tank inlet to see whether wastewater is reaching it freely.
Replacing pipe is a change to the plumbing system, and Norwell requires a plumbing permit through the Inspections Department for that work. Work on the septic tank, distribution box, or leaching area falls under the Board of Health, which reviews septic plans and witnesses soil and percolation tests.
On a wooded lot with wet soil and boulders, ask whether trenchless lining or pipe bursting is realistic or whether an open trench is the only option, and how the plumber will keep groundwater out of the dig.