The landfill comprised significant quantities of ash, bottles, metal, plastic, asbestos and reworked soils. It presented significant stability issues to both the proposed development and an adoptable road.
Construction of the residential development was nearing its final stages which significantly reduced the area available to work on the landfill. Historically, there had also been extensive infestations of Japanese Knotweed on the landfill area. These had been treated during initial development works but rhizome and active plants were still known to be present meaning any earthworks needed to be tightly controlled to minimize the risk of spreading infestation to other parts of the site.
Soilfix implemented a remediation scheme to stabilise the embankment which included:
- Excavation, classification and processing of landfill wastes to form consistent material streams that could be re-used within the embankment;
- Classification and processing of construction arisings to make suitable for use in embankment;
- Lime stabilisation of wet/cohesive soils to improve compaction and structure within the embankment;
- Precision excavation of detailed profiles on steep incline with restricted access including to tie in with existing re-enforced embankment;
- Construction of re-enforced embankment using multiple layers of interwoven geo-grid between layers of processed/improved and highly compacted soils;
- Placing topsoil on a steep embankment stabilised with geo-mat and hydro-seeded with grass;
- Construction of a new footpath along length of new embankment;
- Comprehensive geotechnical verification testing and regulatory signoff; and,
- Health, Safety & Environmental controls within a potentially high risk working environment to meet Crest Nicholson’s stringent requirements.
All works were successfully completed to enable commencement of highway works on-programme with site specific geotechnical requirements met.
