The San Manuel property is a former integrated mining, milling and smelting operation located in central Arizona, USA. Large-scale mining activities started with underground block cave operations in the 1950s. In the mid-1980s, mining was expanded to include a surface heap-leach facility and an in-situ leach operation within the active cave area. Seven miles to the south, the mill, smelter and refinery processed ores from the San Manuel mine. Ultimately, the mining operation encompassed over 300 acres, the plant site operation covered approximately 400 acres, and the tailing storage facilities over 3,000 acres.
In June 1998, BHP Billiton suspended operations at San Manuel. By 2004, BHP elected to permanently close the mine and plant sites. Given the scale of the combined operations, this decision triggered one of the largest, owner-funded, mine and plant closure programs in the world.
Beginning in 2000, SRK staff worked closely with the BHP Billiton project team during the critical decision phases of the project. After the public announcement of closure of the mine site in 2002, SRK continued to provide technical support for conceptual closure planning, site investigation, and assessment of value recovery. This support included evaluating short-term and long-term closure strategies, from cost estimating to preliminary designs. We provided technical assessments of closure requirements, long-term predictions of changes in site conditions, navigating the regulatory framework, as well as contributing to stakeholder consultation with local and regional organisations.
Once the closure strategy was defined, SRK proceeded with detailed permitting and engineering support. During this process in 2004, BHP Billiton announced that the plant site would also be closed. The SRK team built on the success of the mine site program and applied this experience to closing the plant site, including a 750M ton tailings facility.
In 2005, permitting and design work advanced to the point that construction was possible. SRK provided field engineering and construction oversight throughout the 2-year construction period. The estimated cost of the combined closure program totaled more than US$200 million. Over a 6 year-period, SRK helped BHP Billiton move from a strategic evaluation of closure alternatives to the successful, full-scale implementation of the preferred closure design.
