EPW037107 ENGLAND (1931). Allotment Gardens and the Co-operative Wholesale Society Limited Butter Factory by Whitby Road, Evans Park and the River Avon, Brislington, 1931

22 miles? Surely a typo!

The information given on Avon Viaduct 22.71(73yards) is found in a publication 'Track Layout Diagrams of the Great Western Railway Section 19A Bristol Second Edition by R A Cooke.

All bridges on the railway are designated by their distance in miles and chains from a set point on the railway. in this case the datum is likely to be somewhere in the Frome area and all the structures along the line from Frome via Radstock are identified by their distance from Frome. The length of the structure is 73yards. I hope this clarifies the information.