In 1916, the Railway Commissioners set up their own mine, the Railway Mine, later known as the State Mine, on the western coal-fields at Lithgow. Coal was carried by rail to coal stages—ranging from massive structures to small stockpiles—at locations where steam locomotives were refuelled. Four of the electrical power stations in Sydney—Bunnerong on Botany Bay, and White Bay, Pyrmont and Ultimo on Sydney Harbour—were supplied with coal by rail. All these power stations were situated close to the waterfront but that was to obtain cooling water not port access. Two of the power stations—Ultimo and White Bay—initially were operated by the railways and all the power stations in Sydney were built after the rail connections from the coalfields to Sydney were completed. While the Bunnerong Power Station was being built, drilling was carried out to a depth of 2,730 feet (832 m) in an attempt to find suitable coal below the area of the power station site; although a seam of "burnt" coal—destroyed by the intrusion a volcanic dyke—was found at a depth of 2,600 feet (792 m), these efforts were unsuccessful, and it too was supplied with its coal by rail. The other power station, at Balmain, had no rail siding. It was coal-fired but also raised some steam by incinerating garbage. Its coal was landed from barges at the waterfront until 1965 and at least some of the coal for the Balmain Power Station came by sea; around 1919 that included coal from the Cardiff Colliery, which was shipped from Lake Macquarie. Coal and coke for the other states In parallel to the coastal trade to Sydney, there was an interstate coastal trade in coal and coke from the same ports to other Australian states, particularly Victoria, South Australia and Tasmania where black coal was needed for steamship coal bunkering, rail transport and industrial purposes and coke was needed for smelting ores. One notable early interstate trade, from 1866 to around 1893, was that between the Hunter River and the operations of the South Australian Copper-mining Company, at Wallaroo, in South Australia. Coal was carried from Port Waratah to Wallaroo, for use in smelting higher-grade copper ore. At Wallaroo, the empty colliers were loaded with low-grade copper ore, as ballast. The 'ballast' was then unloaded at Port Waratah, where it was smelted at the Port Waratah Copper Works, which had been established by the company for that