Bridge over the Great Fish River - Boy Retief Bridge
Click to view large map
|See more photographs|
The Boy Retief Bridge was designed as a single lane road bridge with a reinforced concrete structure. It comprised of ten equal spans of 19 080 mm (62' 6") supported on nine free-standing piers and two abutments. The total span of the bridge - between abutments - was 190 800 mm (625' 0"). The total width of each road deck (including the narrow raised kerb edging on either side) was 4 600 (15' 0") and the single lane road width was 3 400 (8' 0"). The width of th narrow raised kerb edgings on either side measured 600 (2' 0"). A concrete balustrade of vertical posts and horizontal rails was constructed on the outer edge of the kerb edging.
The southern abutment of the bridge was located a considerable distance from the southern bank of the river - within the flood plain - while the northern abutment was located close to the edge of the river - founded directly onto an exposed bedrock ledge.
In 1974 - eighteen years after the Boy Retief Bridge had been taken into service - construction of a new double carriage-way road bridge had commenced just upstream. This was clearly required to cater for ever increasing road traffic volumes.
In April 1974 very significant rain fell in the catchment area of the Fish River, causing extreme flood conditions. The volume of flood water and the intensity of the water flow damaged the preparatory construction work on the new bridge but more importantly caused the foundations of the Boy Retief bridge to show signs of distress - it started shaking, which became more and more violent. The central pier of the bridge was duly undermined by the force of the water and collapsed along with the two adjacent spans.
The Boy Retief Bridge bridge was at that time the only crossing point over the Fish River (in proximity to the coast) and was therefore the only route between East London and Port Elizabeth since the approaches to all other bridges - as far inland as Cradock - had been damaged by the flood waters.
It was critical that the bridge be repaired as soon as possible. A team of engineers from Johannesburg visited the site to determine the nature of the problem. Their solution was to provide two substantial steel girders to span across the entire width of the opening. Each girder was to be 38 m long with a depth of 2.4 m and with a top and bottom flange of 500 mm. The girders were duly designed and manufactured in Johannesburg by Dorman Long. Each of the girders was made up of four individual lengths which were to be connected with bolted gusset plates.
The repair girders were transported to site by road in 9.5 m lengths and were bolted together on site into 19 m lengths. The first two girder lengths were lowered into position using two large derricks - lifting the 19 m lengths into place from each side. The two girder lengths were were then bolted together at mid-span to form a 38 m long girder. The second girder was similarly installed and was tied into the first girder with diagonal braces. The completed width of the two girders - including the top flanges was 2 920 mm. The bridge deck appears to have been formed with heavy timber baulks - presumably to limit the weight - fixed to the steel structure.
The repair was completed and the bridge re-opened for use in only 10 days – an exceptional achievement.
The bridge is still extant - albeit unused - and stands downstream of the newer bridge. The two steel girders are still in place, though somewhat rusted and with substantial portions removed by metal collectors. The southern approach to the bridge has also been completely washed away with access now only possible onto the northern half of the bridge.
Site inspection and measuring of the extant bridge structure by Carl Vernon, Viv Mostert and William Martinson on 1 July 2018.
Post Script: P. F. ("Boy") Retief, was the Assistant Provincial Roads Engineer in the Cape Province and was described as 'a fine practical engineer, a great man who spoke out when needed, and a helpful boss' from Ross, G.L.D. MOUNTAIN PASSES, ROADS & TRANSPORTATION IN THE CAPE: A GUIDE TO RESEARCH, 5th Edition, June 2013.)
Submitted by William Martinson, July 2018.