Convoys Wharf: From Tudor Warfare to 21st Century Redevelopment
Outline optioneering for the potential regeneration of Convoys Wharf in Deptford, London, gave Geotechnics Limited the opportunity to showcase their sensitive collaborative approach to site investigation and its management on a site rich with significant heritage.
Convoys Wharf, once called the King’s Yard, has played a significant role in London’s and Great Britain’s maritime history, having been the location where some of the most famous exploration vessels and warships were built. The site covers some 40 acres of what was once Deptford Dockyard - the first of the Royal Dockyards - which was built in 1513. The Convoys Wharf site also covers most of the site of Sayes Court, which was the manor house and gardens of diarist and poet John Evelyn.
HMS St Albans being launched onto the Thames at Deptford in 1747, as depicted by John Cleveley the Elder
Today, a number of structures of significant historical importance remain, specifically the 19th century Great Dock, the Grade II listed Olympia building and the 1513 Tudor storehouse (a scheduled ancient monument).
Geotechnics Limited was appointed by Hutchison Property Group, and worked closely with their Engineers BuroHappold on site to deliver a challenging ground investigation on a complex and sensitive site.
Prior to Geotechnics Limited’s involvement,
the site had previously undergone extensive large scale Stage 1 and Stage 2
archaeological investigations in 2010. These investigations exposed a number of historic dockyard structures
below surface, as well as limited evidence of prehistoric and Roman use of the
site. Archaeologists also found evidence
of early walls beneath an 18th century building on the site of Sayes
court, but could unfortunately find no trace of Evelyn’s famous gardens.
The site investigation project team led by
Steve Chapman and Ian Boyle alongside South East Drilling and
Geodrill was faced with a significant challenge to ensure that the intrusive
investigation locations avoided damage to the archaeological remains whilst
still addressing the geotechnical objectives of the work. Detailed planning and
liaison with the archaeologists and engineers was essential throughout,
responding to the findings in a sensitive manner as the work progressed.
Before the main phase of drilling commenced,
the consequence of more recent historical warfare led to a programme of
unexploded ordnance investigation using the Magcone CPT equipment in order to
identify and locate any bombs remaining on the site from World War II. Other hazards
included timber and stone block obstructions from this 500 year old site.
Once the site was cleared for the main intrusive phase, Geotechnics Limited proceeded to undertake a number of cable percussive boreholes with rotary Geobore-S and wireline follow-on to depths up to 75m. This technique proved to be very successful, with excellent recovery in the underlying chalk strata.
However, the site presented the team with a couple of further problems to overcome. Firstly, trial pits were required along the river wall and around the foundations of the Grade II listed Olympia building to investigate the structures and their foundations. These required a considered and patient approach and were completed successfully.
Further, more detailed investigations were required to investigate the construction of the river wall and to focus on areas of failing brickwork. Vertical and inclined probes were attempted along the river wall, both land-side and river-side, utilising custom built hand-held equipment. Horizontal and inclined concrete cores were obtained from the face of the wall and two letterbox sized openings were cut into it to further investigate significant areas of failing brickwork.
Access to these areas proved one of the most difficult challenges, but Geotechnics’ idea of utilising a truck-mounted cherry picker to gain access to the face of the river wall without having to gain access via the river itself proved very effective.
Site investigation is a fundamental part of the construction process, and without it we simply don’t know the hidden geological sequence or historical industrial influences below the ground surface. Our team particularly enjoyed working at Convoys Wharf and overcoming its challenges. As Shakespeare recognised, “Much more in this great work… should we survey the plot of situation and the model, consent upon a sure foundation, question surveyors, know our own estate, how able such a work to undergo”.
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