If you live in the Mill Valley city limits the City's Municipal Code states that the owner of a sewer lateral is responsible for maintaining their sewer lateral all the way to the City main, including the portion within the right-of-way. This includes the fitting that branches the lateral off the main.
However, if you live in any of the unincorporated areas of Mill Valley or Tiburon, homeowner responsibility may differ. Please contact your sanitary district. To find your sanitary district, please go to our SASM Agency Boundaries page.