Question: Which company operates the railway line that bounds Peterhead, South Australia on the west side?

full_context: Document 1: Adelaide–Darwin railway: The Adelaide–Darwin railway is a south-north transcontinental railway in Australia, between the cities of Adelaide, South Australia and Darwin, Northern Territory. Between 2000-2004 the line was extended from Alice Springs to Darwin as a Build, Own, Operate and Transfer back (BOOT) project by the AustralAsia Rail Corporation. This replaced the former narrow gauge line from Darwin to Larrimah and the narrow gauge/standard gauge Central Australia Railway from Port Augusta to Alice Springs which used a different route up to 200 km to the east.
Document 2: City of Port Adelaide Enfield: The City of Port Adelaide Enfield, located across inner north and north-western suburbs of Adelaide, is one of the largest metropolitan councils within South Australia. It was established on 26 March 1996 by the amalgamation of the City of Port Adelaide and the City of Enfield.
Document 3: Tonsley railway line: The Tonsley railway line is a suburban commuter line in Adelaide, South Australia that stems off the Seaford line at Mitchell Park to end opposite Science Park and close to the Flinders University and the Flinders Medical Centre. The line is single track for most of its length, from Celtic Avenue near Mitchell Park station to the terminus at Tonsley, with two intermediate stations. Services operate every 30 minutes on weekdays with no trains operating at night or on the weekend.
Document 4: Division of Port Adelaide: The Division of Port Adelaide is an Australian electoral division in the state of South Australia. The 181 km² seat extends from St Kilda in the north to Grange Road and Findon in the south with part of Salisbury to the east. Suburbs include Alberton, Beverley, Birkenhead, Cheltenham, Findon, Kilkenny, Largs Bay, Mansfield Park, North Haven, Ottoway, Parafield Gardens, Paralowie, Pennington, Port Adelaide, Queenstown, Rosewater, Salisbury Downs, Semaphore, Woodville, West Croydon, and part of Seaton. The seat also includes Torrens Island and Garden Island.
Document 5: Willunga railway line: The Willunga railway line ran through the southern Adelaide suburbs from Adelaide railway station to Willunga, over 45 km long (longer than the current Gawler line, 42.2 km ). The line was opened in Willunga by the Governor of South Australia Sir Henry Galway on 20 January 1915, and initially had 16 stopping places between Adelaide and Willunga. It closed beyond Hallett Cove in 1969 and was dismantled in 1972. The Seaford railway line continues from Hallett Cove along a different alignment before rejoining the route of the old line between Seaford Road and Griffiths Drive.
Document 6: Birkenhead, South Australia: Birkenhead is a north-western suburb of Adelaide 14 km from the CBD, on the Lefevre Peninsula, in the state of South Australia, Australia, and lies within the City of Port Adelaide Enfield. It is adjacent to Peterhead, Exeter and Glanville. It is bounded to the south by the Gawler Reach of the Port River, to the north by Hargrave Street and in the west and east by the Outer Harbor railway line and the Port River respectively.
Document 7: Peterhead, South Australia: Peterhead is a north-western suburb of Adelaide 15 km from the CBD, on the LeFevre Peninsula, in the state of South Australia, Australia and falls under the City of Port Adelaide Enfield. It is adjacent to Largs Bay and Birkenhead. The postcode for Peterhead is 5016. It is bounded to the north by Wills Street, to the south by Hargrave Street and in the west and east by the Outer Harbor railway line and the Port River respectively.
Document 8: Outer Harbor railway line: The Outer Harbor railway line is a suburban branch line in Adelaide, South Australia. It runs from Adelaide station through the north western suburbs to Port Adelaide and Outer Harbor. It is 21.9 kilometres in length, and shares part of its run with the Grange line. It is operated by Adelaide Metro.
Document 9: Marion railway station: Marion railway station is located on the Seaford line. Situated in the south-western Adelaide suburb of Marion, it is 11.4 kilometres from Adelaide station.
Document 10: Pennington, South Australia: Pennington is a northern suburb of Adelaide, South Australia, located about 10 km from the Adelaide city centre. It is located in the City of Charles Sturt.
Document 11: Coast to Vines Rail Trail: The Coast to Vines rail trail open to pedestrians and cyclists, runs for 34 km through the southern suburbs of Adelaide from Marino to Willunga. Much of the trail has been constructed on the disused Willunga railway line.
Document 12: Christie Downs railway station: Christie Downs railway station is located on the Seaford line. Situated in the southern Adelaide suburb of Christie Downs, it is 28.9 kilometres from Adelaide station.
Document 13: Melbourne–Adelaide railway: The Melbourne–Adelaide railway is a standard gauge railway corridor that runs between the cities of Melbourne, Victoria and Adelaide, South Australia. Most of the current traffic is freight, though the only named and perhaps best known regular train is the twice-weekly passenger service "The Overland", operated by Great Southern Railways
Document 14: Port Adelaide: Port Adelaide is the name of a region of Adelaide, approximately 14 km northwest of the Adelaide CBD. It is also the namesake of the City of Port Adelaide Enfield council, a suburb, a federal and state electoral division and is the main port for the city of Adelaide. Port Adelaide played an important role in the formative decades of Adelaide and South Australia, with the port being early Adelaide's main supply and information link to the rest of the world.
Document 15: Port Noarlunga, South Australia: Port Noarlunga is a suburb in the City of Onkaparinga, South Australia. It is a small sea-side suburb, population 2,632, about 30 km to the south of the Adelaide city centre and was originally created as a sea port. This area is now popular as a holiday destination or for permanent residents wishing to commute to Adelaide or work locally. There is a jetty that connects to a 1.6 km long natural reef that is exposed at low tide. The beach is large and very long and has reasonable surfing in the South Port area whose name is taken from its location - 'South of the Port'.
ground_truth: Adelaide Metro