Australia. During a submarine's ten-year operational period it undergoes regular planned maintenance activities at ASC's Western Australian operations at Henderson, adjacent to Fleet Base West. These include 12-month-long mid-cycle docking and several shorter duration maintenance activities. ASC and the Submarine Enterprise manages the upgrades to the Collins capability under the Collins Continuous Improvement Program (part of Defence procurement project SEA 1439). The sustainment, maintenance and upgrade of the Collins-class fleet underwent a Federal Government-commissioned root-and-branch review from 2011 by Dr John Coles, and major reforms were instituted in the following years, including an innovation program across deep maintenance operations at ASC in Osborne. ASC later was recognised by Engineers Australia with an award for the innovation and effectiveness of its improvements to Collins sustainment. The result of the system-wide reform by the Submarine Enterprise has been a "dramatic turnaround" in submarine availability for the RAN and the Collins-class program performing as an "exemplar". The latest review by Dr Coles found that ASC and the Submarine Enterprise were achieving submarine sustainment and availability at or exceeding international benchmarks. Operations and deployments The entire class is based at , also known as Fleet Base West, which is located on Garden Island, off the coast of Western Australia. The decision to locate all six submarines at Stirling was prompted by the lack of suitable long-term facilities on the east coast of Australia (although individual submarines can use Fleet Base East in Sydney Harbour as a forward staging facility), and the proximity to Australian offshore interests, including most of the nation's external territories, the oil and natural gas resources of the North West Shelf, and the Indian Ocean sea lines of communication, through which the majority of Australia's seaborne trade passes. The submarines' primary missions are patrolling the waters of Australia and nearby nations, and gathering intelligence through the interception of electronic communications by foreign nations and the deployment/retrieval of special forces operatives. Operational history Two boats, including Waller, reportedly operated in support of the International Force for East Timor (INTERFET) in 1999 providing an escort for transport ships and monitored Indonesian communications. Navy clearance divers who infiltrated into the Oecussi Enclave to conduct a covert beach reconnaissance ahead of an amphibious landing were reportedly inserted from Waller. During several multinational exercises and wargames, the Collins class has demonstrated its effectiveness in the hunter-killer role by successfully attacking both surface warships and other submarines.