A Watching Brief at the Free Bridge, Jackfield, Shropshire CONTENTS Page No SUMMARY 2 1 INTRODUCTION 2 AIMS AND OBJECTIVES 3 THE HISTORY OF THE BRIDGE by Dr P A Stamper 4 THE PHOTOGRAPHIC RECORD by Dr P A Stamper 5 THE WATCHING BRIEF 6 CONCLUSIONS 7 REFERENCES AND SOURCES CONSULTED 8 ACKNOWLEDGMENTS APPENDIX I - INDEX OF SELECTED PHOTOGRAPHS ILUSTRATIONS Fig. 1: Location of Study Area 1 A Watching Brief at the Free Bridge, Jackfield, Shropshire 1 INTRODUCTION The area of the crossing of the River Severn at Jackfield by the B4373 road linking Ironbridge and Broseley was one of the earliest crossing points of the river in the Gorge prior to the construction of the Iron Bridge. The crossing was by ferry, and a number of timber-framed buildings occupied both sides of the river in the vicinity. Tramways and wharves servicing the industry of the Gorge also lined both sides of the river in this area. Construction work on a new bridge across the River Severn at Jackfield began in June 1993. The existing bridge had been built in 1909 to provide the first toll-free crossing of the River Severn. The bridge was of considerable significance in engineering terms, being a fine example of Mouchel- Hennebrique ferro-concrete construction. However, corrosion and overloading had caused such structural damage to the bridge that a replacement was considered necessary. In view of the archaeological and historical significance of the area, it was decided that an archaeological watching brief would be required on the initial groundworks associated with the construction of the new Bridge, and on the demolition of the old Free Bridge. 2 AIMS AND OBJECTIVES A brief for the recording of the Free Bridge was prepared by M D Watson, Head of Archaeology, Leisure Services Department, Shropshire County Council. The recording and watching brief was required to comprise a number of different elements: Documentary and Historical Research: A search of all the relevant documentary sources was to be undertaken; this research would include the cartographic and aerial photographic sources for the study area, and the primary and secondary sources held at the County Sites and Monuments Record and the County Records and Research Unit. Photographic Record: A full photographic record was required of the existing Free Bridge both before and during its demolition, to include both general views of the bridge and its setting, and detailed photographs of structural and architectural features. Watching Brief: An archaeological watching brief would be maintained during all the initial groundworks associated with the construction of the new bridge. Any archaeological features or deposits encountered during the course of these works would be investigated, and a full written, graphic, and photographic record would be made of the findings. The Archaeology Service of the Leisure Services Department, Shropshire County Council, was commissioned by the County Surveyors Department to conduct this watching brief. 2 A Watching Brief at the Free Bridge, Jackfield, Shropshire 3 THE HISTORY OF THE BRIDGE The history of the bridge is well known, and a useful synopsis is provided in Clark 1989, pp. 16-24 (copy appended). Also known as the Haynes Memorial Bridge and the Subscription Bridge, the Free Bridge was built across the Severn in 1909. It was the first toll-free crossing of the river. The bridge was constructed using the relatively new Hennebique-Mouchel ferro-concrete technique, an attractive option because of its low cost. The design was by L G Mouchel and partners (copies of original drawings appended), the final version having a central arch of 87 feet with two smaller side spans each of 66 feet and with a clear 25 feet between normal water level and the underside of each arch. The bridge was designed to take a load of 140 lbs per square foot. Maintained initially by Wenlock Borough, the Free Bridge was transferred to Shropshire County Council in 1937. Inspection of the bridge at that date revealed crumbling concrete and exposed reinforcing. Repairs were done using the Guniting system, new mesh was added to hold additional concrete, and a 12 ton, 5 miles per hour weight and speed limit was imposed. Later, regular repairs to the parapet were necessitated by traffic damage, while in the 1960s polyester bonded concrete (Certite) was used for repairs including a major compression failure in a vertical spandrel strut in 1969. The weight limit, already reduced still further to 10 tons, was finally lowered in 1986 to 3 tons. In the same year, in order to regain the 10 ton ceiling, a Bailey bridge was placed over the existing structure, and that remained in use until the bridge's demolition in 1993. 4 THE PHOTOGRAPHIC RECORD Black and white photography was done both with a medium format Zeiss Bronica ETRS camera and with 35mm Pentax K1000 system. Film stock was mainly Ilford FP4. Colour transparencies were taken on the same 35mm system. The film stock was Boots own brand colour slide film. A selection of black and white prints and copy slides were supplied to the client, to the National Monuments Record (England), to the County Sites and Monuments Record, and to the Ironbridge Gorge Museum Trust library. The main archive of negatives and slides is held by the Archaeology Service. 5 THE WATCHING BRIEF On each side of the river, the groundworks initially comprised the preparation of the ground surface for the erection of a temporary bridge about 20m to the west of the old Free Bridge. This involved the removal of topsoil and some subsoil from the banks and the excavation of pits for the concrete abutments of the temporary bridge. The abutment pits were first sheet-piled and then excavated, affording minimal opportunity for observation of these excavations. On the south side of the river, the removal of topsoil revealed substantial dumped deposits of cinders and blast furnace slag mixed with some mid twentieth-century building debris around the abutment of the Free Bridge and 3 A Watching Brief at the Free Bridge, Jackfield, Shropshire against the Broseley road. These dumped deposits tailed away towards the river to reveal a dump of mixed clay immediately to the west of the existing bridge abutment and brown silty sandy alluvium over the rest of the waterfront area. The removal of topsoil also revealed the top of a wall set into this alluvium and running parallel to the river about 4.5m back from the water's edge. A short section of this wall could be seen immediately to the west of the construction site, with its northern face exposed. The wall was of drystone construction and built of rough limestone blocks and cobbles. About 9.5m length of wall was exposed within the site running towards the Free Bridge. The insubstantial nature of this wall precludes its having had any structural function, other than possibly acting as a retaining wall along the river bank; it may however simply have been a boundary wall. It is likely that the construction of the Free Bridge would have removed any further easterward extension of the wall. The top of another stone wall was visible running along the river edge just below the summer water line on the west side of the Free Bridge. The wall was built of blocks of what appeared to be a hard conglomerate stone ranging in size from about 0.25m x 0.25m to massive blocks over 1m3. Again in the vicinity of the Free Bridge, this wall appeared to end, and at this point there were a number of displaced stone blocks in the river. A section of this wall was disturbed by the construction of the abutment of the temporary bridge, and it was again encountered by the contractors during the piling for the abutment of the new bridge. This wall probably represented consolidation of the river edge, pre- dating the construction of the Free Bridge, at the approaches to the Jackfield wharfages to the east. No other archaeological features or deposits were observed on this side of the river. The removal of topsoil on the north side of the river again revealed dumped deposits of cinders and slag. The abutment for the temporary bridge was cut straight down through these deposits, and there was no opportunity to observe these excavations, which were carried out within a confined area surrounded by sheet-piling. The contractors did, however, report having encountered a stone wall whilst installing the sheet-piling. The construction of the abutments of the new bridge involved the excavation of sheet-piled coffer dams around bored concrete piles; these excavations confirmed the nature of the ground on both sides of the river as observed earlier in the construction programme, but revealed no new archaeological features or deposits. With the exception of the stone walls encountered during the construction of the temporary bridge, no significant archaeological features or deposits were observed during the construction works. Both banks of the river were the repositories of considerable quantities of dumped industrial waste. During the demolition of the Free Bridge, a number of constructional features, particularly of the reinforcing of the bridge, were recorded in the photographic 4 A Watching Brief at the Free Bridge, Jackfield, Shropshire record. One item, recovered by the Resident Engineer's team, was a "turn buckle", or "tapped socket pipe" as it was referred to on the original working plans (Mouchel and Partners, 1908, 2439 Working Plan No. 7), an uncommon structural element used to connect reinforcing rods (J Fisher, pers. comm.); this item has been kept as part of the site archive. (See Appendices I and II) 5 A Watching Brief at the Free Bridge, Jackfield, Shropshire 6 REFERENCES AND SOURCES CONSULTED Blackwall, A: Shropshire Bridges, Shropshire County Council (County Surveyor's Department Bridges Section Technical Library, ref.