ETAP is based on the development of a Central Processing Facility (CPF)-consisting of a Processing, drilling and Riser (PdR) platform bridge-linked to a Quarters and Utilities (QU) platform over Marnock and a normally unmanned installation on Mungo. The remaining fields, Machar, Monan, Mirren, Madoes and the Shell operated Heron, Skua and Egret fields all produce through subsea manifolds tied back to the CPF. The PdR and QU platforms of the CPF are sited approximately 60 metres apart and are linked by two bridges. This design separates the production risers and Marnock wellheads on the PdR platform from the people on the QU platform. The PdR design also separates the riser area and the Marnock wellheads from a jack-up drilling rig when this is present.