Harpers Field Silt processing
Harper’s Field silt processing gears up
by: Steve P
Early August saw the delivery of a 30-ton monster to Harpers field to process some of the dried silt that had been accumulated over the past years. The “Terex Finlay 873” to give it its full name is a vibrating shaker deck that can sort assorted loose material into piles of small medium and large sizes, with the sizes set by changing internal screens to different sizes.
The machine as delivered on a low-loader was impressive enough, but the team then watched as the installers “unfurled” it into an even larger machine over 12 metres long and wide with 3 conveyors to move the sorted material out from the central shaker deck. The expanded machine can then be moved around on its tracks using a wired remote control!
Les and Andy had decided that its first task would be to process a very large pile of dried silt into material <20mm across, which can hopefully be sold as a soil improver, plus mid and large size material some of which may be useable as hard core, so the machine was moved next to the silt pile. The pile had already been shaped and levelled so that the 13T excavator could load into the hopper from an elevated position – the trick here was to load it without undermining the excavator!
After a training session from the expert the machine was fired up and sorted silt soon started to come out of all 3 conveyors – fortunately most of the material proved to be the small size that we hope to be able to sell, but it still needed the dumper team to collect and move the larger material away as it accumulated.
By the end of the first week most of the initial mountain of unsorted silt had been converted into small medium and large size pieces, with the long reach excavator being used to spread out the pile of fine silt, and latterly to load the final material into the hopper since the excavator platform had by now been processed. The team then used some of the silt fencing around the sorted material so that this doesn’t get mixed in with unsorted material.
With this complete the soil screens in the shaker deck were changed for screens more suitable for aggregate, and work started on processing the large pile of mixed hardcore that had been donated from the Jubilee Ocean Bridge works. Vince had advanced digger training from Les to get the excavator onto a new elevated pad, and sorting then restarted. This produced a large pile of “Type 1” material that is 40mm or smaller and two other piles of medium and large hardcore; it is hoped that this sorted material can either be sold or used for work on towpaths, roadways, etc for Phase 1B
By Wednesday of the second week the team had completed the hardcore screening as well, and were able to take a well-earned rest from their 5-day working apart from Les and Andy who were back in on Friday for the monster machine to be folded up and removed from site. We now have many hundreds of tons of sorted silt and hardcore which hopefully will be both saleable to get income and useful for the ongoing work on the canal saving us from buying new material.
This week saw the team back in again clearing up the site and moving partially dried silt from the wet silt drying area to the secondary and final drying areas ready for more wet silt to be unloaded from the now full mud hoppers. Rumour has it that all the mud hoppers are now full, so it looks like next week will be busy as well although some of the team may get the bank holiday off!
Overall, the exercise has proven that we can screen the silt in large volumes, and hopefully if this can be sold as a soil improver then the canal has identified another revenue source to help fund the ongoing restoration. The dry summer helped, but hopefully we can repeat the exercise next year and both get some revenue and prevent the field from filling up with silt!
