Seven hundred and fifty kilometres of shut down crude oil pipelines DN 700 were emptied, chemically cleaned and conserved by nitrogen in Latvian and Lithuanian territory. The result of these activities was that environmental pollution risk due to oil leakage was eliminated and the pipelines are decommissioned and prepared for the next possible use in the future. Thanks to the completely removal of hydrocarbon residues a permanent safety atmosphere was created inside of the pipelines for the assembly-welding activities without further necessary safety precautions against explosion. In this manner more than two thousands kilometres of oil pipelines in Europe have been decommissioned, abandoned, prepared for repair works or converted from crude oil to refined oil product transportation during the last 10 years.