Case Study – Khranja Foods, Blackburn

Client: Khanja Foods

Value: £4.7m

Location: Blackburn, Lancashire


Brief Description


Others had dismissed this site as too expensive to build on. However, our GEO team present a robust cost effective solution and through geo environmental savings and value engineering the building this allowed the scheme to proceed.


Project Challenges


  • A site others had dismissed a not commercially or environmental viable

  • An infill site bound between commercial buildings and bounded by the canal

  • 5m deep of variable fill and domestic waste

  • Contaminated ground with methane and carbon dioxide – gas situation 4




  • A design with geo savings and value engineering provided a sustainable scheme

  • We carried out a series of trail pitting to establish a robust and cost saving design

  • Locally excavate and sort the refuse, retaining certain materials for re-filling

  • Clean air blanket, saving of 50% over a traditional passive system


The Challenge


This is a site that we had been aware of for several years, but finally turned up on our desk in 2008. This was an infill site between commercial buildings, bounded by the canal and having 5m of variable fill and domestic waste. In addition, the ground was contaminated, with methane and carbon dioxide giving a gas situation 4. This site had been vacant for some years, as others perceived that it was too expensive to build on.


When it arrived with us, our challenge was to build a high bay food warehouse, with three storey’s of office space and all on a recession busting budget.


The Solution


The obvious solution was to pile the whole building. However, with prohibitive costs, we embarked on a series of trial pitting to discover a robust yet cost effective design. In general, the trial pits indicated a loose granular fill over most of the area, but with pockets of refuse. This refuse was broken glass and bundles of waste paper. With a better knowledge of the site conditions and expertise in value engineering, we proposed the following:


  • Locally excavate the refuse and sort, keeping the glass/granular material for re-filling.

  • The small amount of rotting paper was taken off site.

  • Vibro compact the whole site, with lower values to the lorry areas.

  • Pile the building foundations.

  • Ground supported floor slab onto vibro compacted

  • Gas protection using a positive clean air blanket, with a 50% saving over a traditional passive system


The Benefits


  • Our geo-environmental savings, coupled with our value engineering to the building allowed the scheme to proceed within budget.

  • We quickly gained approvals from all regulatory authorities, including British Waterways, which allowed building works to proceed with haste.

  • The solution was sustainable in that we built on a site that was potential seen as scrap value. In addition, the amount of material taken and brought onto site for the sub-structure was minimised.

  • The active gas system, with automatic real time monitoring gave Khanja a confidence of gas protection that was not available with a more traditional passive system, with lower insurance costs.

Welcome to PWA Geo-Environmental:


Leading Geotechnical, Geoenvironmental and Regeneration Specialists


What makes us different...


  • Addressing and understanding site abnormals

  • Significant savings on final build costs

  • Delivering time savings

  • Sustainable value engineering

  • Viability and realising full site potential

  • Strong technical background