If the preliminary soil report indicates the presence of critically expansive soils or other soil problems which; if not corrected; would lead to structural defects; a soil investigation of each lot in the subdivision may be required; prepared by a civil engineer specializing in soil mechanics and registered by the state of California. The soil investigation shall recommend corrective action intended to prevent structural damage to each dwelling proposed to be constructed on expansive or unstable soil. The report shall be filed with the city building department. (Ord. 1046 NCS §1 (part), 1972; prior code §22.6.207.)