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Restricted Access Investigation



LEAP utilises the full range of intrusive investigation techniques including those specifically designed for sites with restricted access and/or limited headroom. LEAP is able to provide the client with specially modified drilling rigs and can provide crews of experienced groundworkers to hand dig boreholes, foundation inspection pits etc. This case study highlights some of those techniques and also provides an example of the many and varied historical sites investigated by the LEAP team.

Description and Investigation Design

Historically the site comprised part of a gas works and was more recently a builder’s yard. Contamination associated with the site’s former use and buried structures including gas holder bases and liquor tanks were anticipated on site.  The site is located on a principle aquifer (Chalk) and adjacent to a sensitive tidal river.   Redevelopment of the site with housing was proposed. 
LEAP was appointed to carry out a review of the previous investigation reports carried out by others and to produce quantitative risk assessments for both human health and controlled waters for the site to provide remedial targets for site clean-up.  
Seven intrusive investigations undertaken by various parties had identified elevated levels of petroleum hydrocarbons (TPH), phenols, cyanide and Polyaromatic hydrocarbons (PAH) as well as heavy metals in the shallow soils.  Groundwater sampling detected similar contaminants in the shallow groundwater.  Slightly elevated levels of TPH, PAH, phenol and metals were also detected in the deep groundwater within the chalk.  River water samples both up and downstream of the site contained traces of cyanide.

The client was proposing to refurbish an early Victorian building, to provide rehearsal and educational rooms for an internationally renowned theatre.  The site is set within an area which has had a long  and colourful history.  During the 16th and 17th centuries this area was occupied by play houses, bear baiting arenas, inns and brothels.  

Towards the end of the 17th century the area became industrialised with tin-glazed and stone ware potteries and glass working being carried out within and immediately adjoining the site in an area known as Bear Gardens.  Davies’ Bear-Garden is believed to have been an arena for various animal baiting sports and also to have contained stables and kennels etc. The stoneware was probably an example of one of the earliest delftware manufacturers in Britain. Access to the site was extremely restricted as was space within the building.  The client required a speedy response and was working to a very limited budget. 



LEAP Solution

Mindful of the budget but at the same time cognisant of the requirement to provide a robust and defendable remediation solution, LEAP quickly and efficiently carried out a thorough desk study and formulated a conceptual model for the site which enabled us to design a targeted and cost effective intrusive investigation.

The intrusive investigation utilised hand digging as well as specially modified drilling rigs suitable for use indoors and/or in areas with restricted headroom.

LEAP was able to demonstrate that no remediation was necessary for the proposed end use.


Project Overview



National Contractor



Sevices Provided

  • Thorough Desk Study 
  • Intrusive Geo-environmental Investigation
  • Quantitative Risk Assessment


Added Value

LEAP was required to provide a remediation strategy for a site which was understood from the outset to have had a long and colourful past and which was set within an area of historic and archaeological significance. 

LEAP was able to demonstrate with the use of low cost restricted access intrusive techniques and most importantly well considered and technically robust risk assessment that no remediation was necessary.