Late 18th century culvert, 'Langford Ditch chunker', Chelmer & Blackwater Navigation, near Heybridge Mill (EHER 47325)

A timber culvert, known locally as a 'chunker', was built to carry the pre-existing stream known as the Langford Ditch underneath the new canal section of the Chelmer and Blackwater Navigation between Heybridge Mill and Black Bridge constructed 1793-1797 Archaeological monitoring was undertaken during its replacement works which were necessitated by the partial collapse and potential failure of this historic structure. <1>.

February-March 2010. Watching brief. A programme of archaeological monitoring was undertaken by Essex County Council Field Archaeology Unit (ECC FAU) on the removal and replacement of a late 18th century timber culvert, known locally as a ‘chunker’, beneath the historic Chelmer and Blackwater Navigation. The Blackwater Navigation was built between 1793 and 1797 to make the River Chelmer navigable between Chelmsford and Maldon. A new section of canal was cut to bypass Maldon and provide a new route to Heybridge Basin, which in the 19th century led to the growth of Heybridge as a port to rival the existing port at Maldon. Along the new route, timber culverts were laid beneath the canal to carry existing streams, one of which survives in the section between Heybridge Mill and Black Bridge. Prior to the watching brief, a section of the Langford ditch chunker had collapsed and required replacement by a modern pipe. The watching brief was able to confirm the presence and construction of the culvert, but waterlogging prohibited the identification of associated archaeological features and deposits. The chunker is a wooden structure that spans the width of the canal on a north-west to south-east alignment and finishes beneath artificial embankments either side. It is approximately 33m in length, 1m-wide and 0.6m deep and built from 3 inch (70mm) thick elm planks. Elm is often used in waterlogged conditions for its preservative qualities. Indeed, despite the partial collapse in the top (cause unknown) the timber was noted to have survived remarkably well over the past two hundred years. The south-east end, which drains back into the stream within the grounds of Heybridge Mill House, had been kept in position by large 1.6m stakes either side, made from a single split piece of timber. Other stakes were present on each section. Three discarded/disturbed broken stake-ends were found in the vicinity, one of which had a curious square cut-out end. <1> The chunker carried the stream from EHER 40171 to EHER 40173.