Sanitary sewer improvements shall include the main line connected to the existing system, manholes and a lateral stubbed to the property line of each lot. Such laterals shall be marked on the top of the curb with the letter "S" at such time as concrete is placed. Septic tanks, cesspools, leach fields, or permanent force mains will not be permitted without specific written approval by the city engineer prior to tentative map approval. (Ord. 617 §2 (Exh. A), 2011; Ord. 474, 2002).