Atoll. The Army leased on Johnston Atoll. Phase I of the operation took place in January and moved 150 tons of distilled mustard (HD), a blister agent chemically identical to mustard agent (H), manufactured by either the Levinstein or Thiodiglycol processes, but purified further so that it can be stored longer before polymerizing. The arrived at Johnston Atoll with a load of HD projectiles on January 13, 1971. Phase II completed cargo discharge to Johnston Atoll with five moves of the remaining 12,500 tons of munitions, in August and September 1971. They arrived in the following order: , , USNS Miller, USNS Sealift, USNS Pvt McGraw. The , under the command of a Captain Pilcher, was part of Operation Red Hat. Units operating under United States Army Ryukyu Islands (USARYIS) were 2nd Logistical Command and the 267th Chemical Company, the 5th and 196th Ordnance Detachments (EOD), and the 175th Ordnance Detachment. Originally, it was planned that the munitions be moved to Umatilla Chemical Depot but this never happened due to public opposition and political pressure. The United States Congress passed legislation on January 12, 1971 (PL 91-672) that prohibited the transfer of nerve agent, mustard agent, agent orange and other chemical munitions to all 50 U.S. states. Storage and destruction The 1971 weapons transfer voyages transported the chemical agents that became the first stockpile at Johnston Atoll. The chemical weapons brought from Okinawa included nerve and blister agents contained in rockets, artillery shells, bombs, mines, and one-ton (900 kg) containers. In 1985 the U.S. Congress mandated that all chemical weapons stockpiled at Johnston Atoll, mostly mustard gas, Sarin, and VX gas, be destroyed. Prior to the beginning of destruction operations, Johnston Atoll held about 6.6 percent of the entire U.S. stockpile of chemical weapons. The Johnston Atoll Chemical Agent Disposal System (JACADS) was built to destroy all the chemical munitions on the island. The first weapon disposal incineration operation took place on June 30, 1990. Transition from the testing phase to full-scale operations began in May 1993, and in August full-scale operations began. Twice, in 1993 and 1994, the facility had to be evacuated because of hurricanes; operations were delayed for as long as 70 days during these periods. On December 9, 1993, a spill of about 500 pounds (226 kg) of Sarin (Agent GB) occurred inside the Munitions Demilitarization Building. No sarin leaked beyond the building and the contingency