Originally built in 1963, Petersburg was one in a fleet of five tankers fitted with an offshore petroleum discharge system.
An Offshore Petroleum Distribution System (OPDS) provides a semipermanent, all-weather facility for bulk transfer of petroleum, oils, and lubricants (POL) directly from an offshore tanker to a beach termination unit (BTU) located immediately inland from the high-water mark. POL then is either transported inland or stored in the beach support area.
Major OPDS components are: the OPDS tanker with booster pumps and spread mooring winches, a recoverable single-anchor leg mooring (SALM) to accommodate four tankers up to 70,000 DWT, ship to SALM hose lines, up to four miles of six-inch (internal diameter) conduit for pumping to the beach, and two BTUs to interface with the shore-side systems. The Petersburg also contains stowage cradles for five OPDS utility boats (OUBs) and a 59 LT capacity crane to load/offload the OUBs.