The Port Bonython oil spill occurred on 30 August 1992, when the fuel tank of the tanker Era was pierced by the bow of the tugboat Turmoil during berthing operations in upper Spencer Gulf, South Australia. Wind and swell were high and 296 tonnes of bunker fuel were released into Spencer Gulf. The incident resulted in 500 oiled birds and damage to 15 km of mangrove and seagrass habitat south-west of Port Pirie.
Spill
30 August
The spill occurred at 10.52am, as the Era was berthing at the Port Bonython wharf in rough seas. The vessel had arrived to load oil for the Kwinana Oil Refinery. The Era was chartered by BP and the tugboat involved, Turmoil, was property of the Adelaide Steamship Company. Also present were the tugboat Taminga and the line-boat Wanilla. A lug on the Turmoil's bow pierced the hull of the tanker, leaving a 20 cm hole in the hull and rupturing her fuel tank. The 94,287 deadweight tonne vessel was listed 5 degrees to slow the flow of heavy bunker oil, and the leak was eventually stopped at 2.12pm. A total of 296 tonnes of heavy fuel oil had escaped into the sea.
Response
The slick was described in the official report as "a moderate sheen with streaks of heavy dark oil moving round the stern of the vessel." Tug boats were driven through the slick in an attempt to break it up, and the spraying of chemical dispersant commenced soon after the spill occurred. 400 litres of Corexit 7764 and 4200 litres of Corexit 9527 were supplied by Santos.
The absence of an appropriate crane at the jetty made loading Turmoil with dispersant at Port Bonython impossible. Instead, the tugboat proceeded to Whyalla to load, while the dispersant was transported there by road. The Santos-owned Shark Cat Tregalana loaded in Santos' boat harbor. The other vessels present were unable to assist due to the Wanilla requiring towing by the Taminga. A line had fouled its propeller during the berthing of the Era.
Three different chemical dispersants were used: Corexit 7764, Corexit 9527 and Ardrox 6120. Strong north-westerly winds of up to 25 knots combined with tide and current initially transported the oil slick eastwards, towards Port Germein. The high winds prevented the early use of containment booms.
Assisted by the Department of Environment and Planning, volunteers prepared for the possibility of a 'massive clean-up'.
31 August – Day 2
The 20 cm hole in the fuel tank of the Era was temporarily repaired, and the tanker was loaded in preparation to sail for Kwinana, Western Australia in the evening. The Department of Marine and Harbors announced that the oil spill posed no threat to wildlife. At this time, only 30 tonnes of oil was left at the sea's surface. The slick was estimated to be dense, 500 m long and 100 m wide.
1 September – Day 3
The Era departed Port Bonython for Kwinana, Western Australia at 5.30am, laden with 22,990 tonnes of crude oil from the Cooper Basin.
The spill had attracted national news media attention. A visible 10-20 tonne slick remained on the water's surface after the majority of the oil had been sprayed with chemical dispersant. The dispersal of the slick involved 50 people, five boats, a helicopter and spotter aircraft.
25 Special Emergency Services (SES) personnel were placed on standby. Staff from the Australian Marine Oil Spill Centre (AMOSC) were present to supervise the use of booms to channel the oil, and some oil was recovered by this method. At this time, there had been no reports of dead fish or birds. About 10 volunteers were ready at Port Pirie to handle any oiled wildlife. Council workers were also dispatched from the Mount Remarkable District Council to assist.
Local pilot Syd Cheesman said that he had seen places where "the oil is on the bottom and the water is on top of it." He also described the slick as covering "an extensive area".
2 September – Day 4
About 10 tonnes of oil had washed into mangroves overnight. A slick 15 km long had been seen drifting 1 km off Port Pirie. A makeshift animal hospital was established in Port Pirie. Small boats searched at first light for oiled birds.
The visible oil was described by David Gray of the Australian Maritime Safety Authority as 'a sheen on the water'. Some of this sheen impacted the mangroves and a number of tidal creeks to the south-west of Port Pirie.
The estimated number of impacted birds was revised from 100 birds to up to 500 birds as the search and recovery efforts began. Rescuers expressed concern about the birds' ingestion of oil as a consequence of preening.