​This active landfill site required additional tipping space for domestic waste which meant the construction of a new cell and also an extension of the bunds and cell walls surrounding a hazardous waste cell. Also included were temporary capping works for the finished portion of a sulphate cell.

The sulphate cell capping was used by JN Bently’s site agent, Sean Wilby to evaluate the scrapers performance compared to conventional methods because at this stage pull type scrapers were untried within the company. The objective was to cart approximately 5500 cubic metres of clay from a stockpile to form a  450mm thick temporary capping to the sulphate waste with a 1.5 metre bund along the edge of the active section to avoid dust and rainfall hazards. After initially grading the waste within the cap area, the clay was placed to specification using our Tractor pulling one 19 Cu Y scraper in 20 working hours with only a self propelled roller required to seal the clay following placement. Site agent Sean Wilby was very impressed with both the efficiency and associated cost savings demonstrated during this trial and immediately put the scraper to work on the remainder of the contracts detailed below.

Excavated spoil from the domestic waste cell (DWC) construction was used partly to form the bund extension for the hazardous waste cell (HWC) and after completing the temporary capping to the sulphate cell, our Tractor / scraper was involved in trimming the new DWC floor to level removing the bulk prior to a laser dozer fine trimming to finished level. Once completed we began to place the clay for the cell liner using three tractors with 19 cubic yard scrapers. The clay had been previously stockpiled and was located approximately 150 metres from the DWC area. Specification required it to be placed in four 250mm layers and tested for condition and compaction at various places on each layer using an NDG (nuclear density gauge) to ensure impermeability to liquid.

During the scraper loading process any lumps contained in the stockpile were broken down which conditioned the clay sufficiently to allow direct placement in the cell. Cycle times were around five minutes with the scrapers grading each layer to within the tolerances required. It was also noted at this stage that the layout of the four rear wheels on each scraper compacted the clay to NDG specification although a padfoot roller was still used to ensure even compaction and keying between layers. This operation was completed during a period of foul weather and despite this the scrapers were able to return to work much faster than using conventional methods because of their ability to grade haul roads, stockpiles and fill areas and also to clean up following rain.

The HWC bund required spoil sourced from various site stockpiles to be engineered in 250mm layers. Once completed to the required finished levels, a clay liner was placed in 250mm layers on the inside, 45 degree face of the bund using a bench system at one scraper width, (3M), to facilitate compaction which was then trimmed to the correct depth using a backhoe.

 

  Throughout these contracts the scrapers were noted to be very fuel efficient, safer due to fewer operatives on site and demonstrated a large cost per cubic metre saving compared to conventional earthworks methods because of minimal plant usage.

 

JN Bentley’s Sean Wilby commented  “Watching the scrapers placing and accurately trimming clay was a revelation, straightening up haul roads while returning to the stockpile coupled with obvious fuel/labour savings, the modern scraper offers versatility that is hard to ignore.”

 

Sean can be contacted through JN Bentley’s website at   http://www.jnbentley.co.uk/