In order to determine the design and path of underwater pipelines and cables, surveys of seabed topography and investigations of local currents enable engineers to evaluate the potential occurrence of scour and the need for freespan measures.
Eliminating unacceptable freespans, resulting from undulating sea floors, will require pipeline supports that meet the regulatory requirements, following design codes such as DNV-RP-F105 for freespans. Seabed scour around pipelines and structures will occur as a result of increased velocities caused by localized currents. Fabric formed concrete mattresses can be designed and installed to protect both new and existing pipelines from the loss of supportive sediment.
Engineers used computer modeling software to identify tens of potential freespans that would need addressing along a recently completed project, in the Bay of Bengal, that required formwork supports for a new 32 in export pipeline and a 14 in intra-field pipeline.