associated building of new sporting facilities such as the Sheffield Arena, Don Valley Stadium and the Ponds Forge complex. Sheffield began construction of a tram system in 1992, with the first section opening in 1994. Starting in 1995, the Heart of the City Project has seen public works in the city centre: the Peace Gardens were renovated in 1998, the Millennium Gallery opened in April 2001, and a 1970s town hall extension was demolished in 2002 to make way for the Winter Garden, which opened on 22 May 2003. A series of other projects grouped under the title Sheffield One aim to regenerate the whole of the city centre. Sheffield was particularly hard hit during the 2007 United Kingdom floods and the 2010 'Big Freeze'. The 2007 flooding on 25 June caused millions of pounds worth of damage to buildings in the city and led to the loss of two lives. Many landmark buildings such as Meadowhall and the Hillsborough Stadium flooded due to being close to rivers that flow through the city. In 2010, 5,000 properties in Sheffield were identified as still being at risk of flooding. In 2012 the city narrowly escaped another flood, despite extensive work by the Environment Agency to clear local river channels since the 2007 event. In 2014 Sheffield Council's cabinet approved plans to further reduce the possibility of flooding by adopting plans to increase water catchment on tributaries of the River Don. Another flood hit the city in 2019, resulting in shoppers being contained in Meadowhall Shopping Centre. Between 2014 and 2018, there were disputes between the city council and residents over the fate of the city's 36,000 highway trees. Around 4,000 highway trees have since been felled as part of the ‘Streets Ahead’ Private Finance Initiative (PFI) contract signed in 2012 by the city council, Amey plc and the Department for Transport to maintain the city streets. The tree fellings have resulted in many arrests of residents and other protesters across the city even though most felled trees in the city have been replanted, including those historically felled and not previously replanted. The protests eventually stopped in 2018 after the council paused the tree felling programme as part of a new approach developed by the council for the maintenance of street trees in the city. In July 2013 the Sevenstone project, which aimed to demolish and rebuild a large part of the