Caton Road, Lancaster
Encapsulation of contaminated land
Geobind were asked by Glanville Civil and Structural Engineers to design and implement an in-situ stabilised solution to replace the traditional capping and sub base layer works at a new drive-through restaurant in Lancaster. The design was to eliminate the need for the muck away and disposal of contaminated soils containing asbestos. The initial ground investigation reports highlighted that the soil contained traces of asbestos which would be prohibitively expensive to remove, dispose of and replace with aggregate.
The design required a 2,500m2 capping and sub-base area to achieve CBR strengths of 30% and to be non-frost susceptible.
Samples were collected from site and sent to a UKAS accredited laboratory for analysis and testing.
To gain regulatory approval for stabilisation, Geobind undertook a suite of bench scale stabilisation trials to assess both the geotechnical and leachability performance. This was to establish the optimal mix design to satisfy the remediation objectives. The results were then validated within a verification report.
As the treated material volumes were less than 1000m3 Geobind were able to obtain an exemption for the works which would mean that there was no requirement to deploy an Environmental Permit. However, Geobind worked closely with the Environment Agency to notify them of the duration, nature and control measures in place, and ensure that works were in line with best practice and legislation.
Geobind, working with the client’s environmental consultants Pam Brown Associates, produced a remediation strategy and materials management plan, which was submitted and agreed by the relevant local authorities prior to works commencing on site.
The main contractor prepared site to level and maintained responsibility for the final levels of the job.
Geobind deployed its single pass dust free rotavator and mixed the GEOBIND® proprietary binder to the required depth of 320mm for the Class 2 foundation layer (capping and/or sub-base).
Geobind levelled the mixed material, then compacted with a 13 tonne vibro-roller; using no less than 8 passes to ensure the correct compaction.
Geobind carried out in-situ testing and sent samples of mixed material away for UKAS Laboratory testing. CBR strengths of over 30% were achieved in less than 24 hours.
Geobind were able to successfully encapsulate the contaminants to the required environmental and construction specifications utilising their unique patented binder and single pass dust free in-situ mixing process.
The required strength needed to exceed 150MPa; the actual strength achieved averaged 365MPa. The impermeability requirement of the GEOBIND® stabilised layer was exceeded with results of over 10–9. The total works programme was reduced from 6 days to 2 days by using the GEOBIND®, system achieving cost savings of greater than 30%.