Commentary on Sections Part 1 – Works Section 2 – Bridge proportions
22.This section sets out limitations on the construction of the proposed bridge to ensure its safe operation and the safe operation of shipping and aviation interests that will pass respectively below and above the bridge.
23.The Firth of Forth is a navigational water. To provide certainty to vessels passing under the new bridge, section 2(a) sets out the headroom for the bridge. The headroom is the minimum height between the water level and the lowest point of the underside of the bridge or any attachments to the bridge. In the United Kingdom, heights above sea level are defined in terms of Ordnance Datum Newlyn, which is the mean sea level at Newlyn in Cornwall.
24.There are two navigational channels which pass under the area where the new bridge is proposed to be located. The three towers to support the bridge are not to be located in the navigational channels of the Forth. The navigation channel which passes between the proposed Central Tower of the bridge and the proposed North Tower is known as the Rosyth Navigational channel and the channel between the proposed Central Tower and the proposed South Tower is known as the Forth Deep Water Channel. The minimum distance between the towers as referenced in paragraphs (c) and (d) includes the whole of the relevant channel under that part of the bridge. The location of the proposed Central Tower will be, as stipulated within paragraph (b), on an islet known as Beamer Rock.
25.Paragraphs (e) and (f) provide a limit as to maximum height of the towers once constructed to ensure there is no interference with air traffic in the area.