cannot be replaced. As an alternative, development of the island for seaside residential use was mooted and in 1970 a bridge from the mainland via Russell Island was under serious consideration by the Queensland government. The Queensland Government also proposed a large-scale redevelopment of the island in the mid-1980s which would have seen the population of the island increase tenfold. However, after a concerted bid by conservationists and planners concerned at the impact on wetlands, fish breeding grounds and the impact of population growth, the idea fell from favour in February 1986 when Premier Bjelke-Petersen ruled the idea was not "financially viable". In 1991, the Australian Government and sand mining companies ACI and CRL attempted to reach an agreement on surrender of some or parts of mining lease tenements to form a national park. Half of North Stradbroke Island was to become a national park in return for a guarantee that mining could continue for the life of several mines in high-grade areas.1 The agreement was not signed by either of the mining companies nor the Government and has lapsed. Sibelco Australia operated three sand mining sites on the island – Enterprise (by far the largest), Vance and Yarraman. Mineral sands and silica sands at Vance mine, near Dunwich, are mined from the surface. Rutile, zircon and ilmenite were dredged from the Enterprise Mine, southeast of Dunwich (and previously the Yarraman Mine, south of Point Lookout). Enterprise was the largest mine on the island and accounted for 60% of the island's production in 2011. It operated in close proximity to the Eighteen Mile Swamp along a migrating dredge path with a buffer zone from the wetlands prescribed by the Queensland Government. Conservationists have expressed concern that these buffer zones, the smallest of which is , are inadequate to protect the Ramsar-listed wetlands from pollution and will fail to protect the waterways, citing evidence from the 1976 inquiry into sandmining on Fraser Island which found even buffer between areas mined and wetlands was "totally inadequate". In 2009, of minerals were being produced by mining about 50 million tonnes of sand. Sibelco Australia produced of sand annually (approximately one per cent of North Stradbroke Island's total sand). The silica extracted was used mainly in glass production, but also in digital tablets such as iPads. The mineral sands were used in paints, plastics, metals, cosmetics and biotechnological devices (such as prosthesis), both for