Allied Glass Site, Leeds

Richard Pennock

Director

Tel: 01423 276000

Email Richard

Client

Adept Consulting Engineers

Services

  • Phase I Desk Study & Coal Mining Risk Assessment
  • Phase II ground investigation, including assessment of potential shallow mine workings
  • Delineation of former open cast highwall
  • Contamination assessment
  • Outline foundation appraisal
  • Client support during meetings with insurance underwriters

Phase I and Phase II Ground Investigation

CGL was commissioned to undertake a consolidated Phase I Desk Study and Coal Mining Risk Assessment (CMRA) and subsequent intrusive Phase II Investigation to assess potential contamination and geotechnical design issues at a former warehousing site on Cross Green Industrial Estate in Leeds.

Following a fire that destroyed the previous warehouse units, the site was cleared in preparation for the redevelopment, supported by the resultant insurance claim. The proposed redevelopment consisted of a number of new warehouses and associated offices.

The Phase I Desk Study and CMRA reviewed the environmental and geological setting of the site in the context of historical land uses, coal mining in the area and the development proposals. The potential risks, liabilities and development constraints were then outlined along with requirements for further investigation and assessment. CGL developed a detailed preliminary ground model that identified potential unrecorded shallow coal mine workings beneath part of the site and a backfilled open cast pit and highwall below the rest of the site.

A Phase II investigation was undertaken to verify the preliminary ground model and assess the potential geoenvironmental and geotechnical constraints identified by the Desk Study. The investigation comprised trial pitting and window sampling to assess the potential shallow contamination risks associated with the site’s former industrial and coal mining usage. In addition, gas monitoring was undertaken to assess potential risks from the backfilled open cast pit and former coal workings.

Combined rotary/percussive drilling assessed the depth of the open cast backfill and potential presence of unrecorded shallow workings. Due to the proximity of occupied properties in certain site areas and a potentially combustible coal seam, water flush drilling was undertaken in accordance with Coal Authority best practice.

Further detailed investigation was also undertaken to delineate the highwall location due to its position relative to a proposed warehouse unit. This enabled the client to adopt an appropriately designed foundation approach to mitigate the potential risks of differential settlement from the unit spanning the highwall.

The investigations identified the location and depth of the backfilled open cast workings and did not identify the presence of shallow coal mine workings underneath the site. The works allowed CGL to provide a contamination appraisal of the potential risks and outline foundation solutions for differing ground conditions; shallow bedrock in the north and open cast cohesive backfill with deeper bedrock in the south.