A £6.5 million project to strengthen the hillside, improve drainage and boost flood resilience at Scout Road in Mytholmroyd, West Yorkshire has been completed with the help of specialist ground remediation and soil stabilisation company Deep Soil Mixing Ltd for client Calderdale Council.
In early 2017 Deep Soil Mixing Ltd were approached by the Council to put forward a scheme for the stabilisation of a hillside and asbestos fibre encapsulation.
Using their controlled soil mixing technique, Deep Soil Mixing Ltd has transformed this challenging site through the use of mass mixing using Deep Soil Mixing Ltd's Allu bucket on a 20-tonne excavator.
The soil stabilisation process Deep Soil Mixing Ltd has undertaken on this hillside which covers approximately 3500M2 has proved to be an economical and practical solution - the soil had to be stabilised and the asbestos fibres contained in the ground locked in, before Calderdale Council could landscape the site.
Prior to commencement on site, Deep Soil Mixing Ltd undertook rigorous testing and assessment of the ground to assess its suitability for soil mixing. Laboratory tests were also undertaken using samples of the soil to be treated mixed with different proportions of a wide selection of binders to select the most appropriate mix. From these results, Deep Soil Mixing Ltd then prepared a detailed specification.
Deep Soil Mixing Ltd also installed a King Post Wall at the bottom of the affected area to create an anchor point for the stability of the slope. This was to ensure that any slips during the soil stabilisation works on the upper slope would be contained and would not affect the surrounding buildings and services. It also created a stable working platform from which the mixing operation could commence.
The slope had to be mixed in very carefully designed cells because of the risk of further slippages. This meant that precision was key during the stabilisation process and detailed records and daily monitoring was required to ensure the health and safety of the workforce and the neighbours was ensured.
The workforce had to be fully asbestos certified to work with and dispose of asbestos to commence work upon the site, and this ensured some tricky working conditions with full face masks and disposable clothes, as well as decontamination when exiting the working area. This made sure that the project was extremely challenging both from a health and safety perspective and on a technical level.
Deep Soil Mixing Ltd Director Colin Critchlow comments: "Soil Mixing has proved to be an ideal solution for this slope stabilisation project, but it can also be used in a wide variety of other applications. In addition to the environmental advantage, stabilisation of soft soils by adding binders to reduce settlements and/or improve the stability of the land can be both a quick and cost-effective solution compared to some traditional methods including piling.
"As well as being suitable for some contaminated ground, if developers have a site with soft ground being present including peat and alluvial deposits, glacial till, bogs, etc soil mixing will improve the soil using the soil mixing system.
"By making use of the existing ground and improving it to achieve a specified bearing capacity and shear strength, there is no need to excavate, cart away or dispose of the existing material off site and then bring in costly and bulky fill materials. It is not though, just about improving unsuitable ground but aims to turn poor quality soils into an acceptable foundation bearing strata.
Cllr Barry Collins, Calderdale Council's Cabinet Member for Regeneration and economic strategy, said:
"The completion of work at Scout Road is a key milestone in Calderdale's recovery from the floods. Along with borough-wide flood alleviation schemes and a range of natural flood management projects, it's a powerful example of our determination to build resilience against extreme weather events… It has been carried out to the highest possible standard and many of the techniques used have shown real innovation, leading to improved protection for over 80 nearby homes and around 30 non-residential properties."