Huge marine decontamination facility established approximately 30 kilometers offshore from Manhattan. Composed of two units, Shell 1 and Shell 2, with each unit made up of a central building surrounded by six legs. Resembles a tortoise shell when viewed from above.
The sinking of a tanker off Manhattan in 2007 caused a large quantity of crude oil to be discharged into the sea. The government immediately responded with the construction of an oil fence. Using chlorine derivatives, they sterilized the entire zone of polluted sea and constructed a huge marine decontamination facility. Biological reactors managed in nodes are installed inside Big Shell, and it is held up as a symbol of environmental protection.
Disguised as a decontamination facility, Big Shell was actually a facility for constructing the Navy's massive Metal Gear, "Arsenal Gear." The environmental protection episode was a cover story to conceal this fact. A tanker was intentionally sunk to pollute the ocean with crude oil. The decontamination effort that followed was staged in order to complete tests on Arsenal Gear and the GW neural AI.