A pipeline installation and maintenance method and system is disclosed in which a number of interconnectible platform modules are assembled into drilling platforms from which a segmented pipeline route is flexibly installed. Using modified push/pull rigs to carry out a transverse drilling process established between platforms, successive portions of the pipeline are installed such that equipment used to create completed segments is moved down line and re-used in subsequent drilling and installation stages. Further segments of the line are similarly constructed, using one or more of the modified directional drilling techniques and transverse reaming processes disclosed herein. Ultimately, a long series of adjacent pipeline segments are installed along a desired pipeline route, while only minimal and temporary disturbance is caused to associated ground surfaces during installation and maintenance operations.