Supplementary engineering services, procurement and supply of project-specific materials (P), construction and installation works, pre-commissioning and start-up of turbocompressors and peripheral equipment and other services included in the contractor’s work description, for the connection project of gas pressure boosting facilities of the fifth pipeline (Khormouj, Abpakhsh and Sardasht) to the 6th national pipeline and the installation of Khormouj and Abpakhsh gas pressure boosting facilities of the 5th national pipeline by PC method