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Three Mills Lock, also known as the Prescott Lock is a lock on the Prescott Channel on the River Lea in London. The project was led by British Waterways〔(''Revitalising London’s Olympic Waterways'' ) (British Waterways) accessed 1 August 2008〕 and the lock officially opened on 5 June 2009. The lock cuts off this section of the Bow Back Rivers from the tide, creating new opportunities for leisure boats, water taxis, trip boats and floating restaurants. It also helps freight traffic such as barges carrying construction materials to the sites of the 2012 Olympics and Stratford City. ==Design== Three Mills Lock has been built on the Prescott Channel, which was constructed in the 1930s as part of a scheme for flood prevention and the creation of employment. It bypassed the tide mills at Three Mills, and included a sluice structure, which was used to control levels in the Bow Back Rivers much as the present structure is. This original structure became inoperative by the mid 1960s, and was removed in the 1980s, as the Bow Back Rivers had been classified as Remainder Waterways by the 1968 British Waterways Act, and there was no funding for maintenance.〔(【引用サイトリンク】title=Bow Back Rivers - A potted history )〕 A consequence of this was that the rivers reverted to being tidal. This made navigation difficult, since there was not enough water at low tide, and at high tide, there was insufficient headroom,〔(【引用サイトリンク】title=Restoration Plans )〕 due to the low level of the Northern Outfall Sewer, which crosses the waterways. With the selection of the island formed by the City Mills River and the Lee Navigation as the site for the 2012 London Olympics main stadium, restoration of the channels was thought to be an important part of the site development, particularly as it might allow some of the construction materials to be delivered by barge. A new lock and sluice structure was therefore designed for the Prescott Channel, with a second sluice on the Three Mills Wall River to prevent tidal water flowing backwards through the Three Mills tide mill. Prior to the development, tidal levels on the Bow Back Rivers reached above ordnance datum (AOD) on spring tides. The sluice is designed to stabilise levels at AOD, and the lock structure therefore has to cope with levels on the downstream side which might be higher or lower than those on the upstream side. The new lock is long, wide and deep, and is able to hold two 350-tonne barges (the present locks on the nearby Lee Navigation limit barges to about 120 tonnes).〔(''Notes and News'' ) (April 2007) (Greater London Industrial Archaeology Society)〕 The tidal range is handled by the use of hydraulic sector gates at both ends of the lock, and the structure incorporates two large rising radial gates for flood control in the Bow Back Rivers.〔 A site in the river, just south of this lock is the resting place of the remains of the Euston Arch.〔''Euston Arch found at bottom of river'', ''The Times'' (4 June 1994).〕〔(Where are the remains of the arch? ) (Euston Arch Trust) accessed 16 July 2008〕 A footbridge for pedestrians and a fish pass for migrating fish is incorporated into the design of the lock,〔 and British Waterways claim there will be associated improvements to the navigation and tow path, as a part of the Olympic legacy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Three Mills Lock」の詳細全文を読む スポンサード リンク
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