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►CS05 Windermere Gardens, Chester
| Development: | Slope failure adjacent 3 residential properties |
| Year: | 1993-2001 |
| Clients: | Wainhomes |
| Development Value: | Unknown |
Coopers were commissioned to investigate and mitigate a major slope failure to the rear of 3 No. properties in 1993. These properties were constructed by Wainhomes as part of a residential housing development named ‘Windermere Gardens’ in 1987. The land to the rear of the properties had been extended utilising non-engineered clay fill materials to form gardens for the properties, steepening the already existing slope into the adjacent Caldy Valley Country Park.
These fill materials were found to have failed during late 1987 to early 1988, and were remediated by Soil and Materials Testing who constructed a new “clay bund” to retain the poor quality fill. This remediation was not successful. After investigation by Coopers and John Moores University, it was determined, with no access for heavy construction plant, that soil nailing of the clay bund and the fills could provide long-term slope stability.
One hundred and fourteen soil nails were drilled into the entire slope by Keller Colcrete in December 1994, and fifteen inclined drains were added in February 1995 to remove surplus waters within and on top of the clay fill materials. Completion Reports were provided to the property owners.
Due to a resident selling their property in 2001, Coopers were requested to reinspect the slope and garden area of one of the properties for the purpose of their buildings insurance. All fencelines appeared true, and there was no evidence of tension cracking along the crest of the slope associated with the failure of a slope.
The slope face was observed from the Caldy Valley Nature Trail, beyond the rear of the plot, and the face of the slope appeared sound, with no signs of abnormal bulging, obvious cracking or potential slip planes.
We determined the stabilisation of the clay bund and the fill materials forming the rear gardens for these properties, which was completed by Keller Colcrete, was performing satisfactorily. The strengthening measures were successfully completed in February 1995 and are permanent measures designed to ensure the long-term stability of the embankment. The current foundations are not within the clay fill materials, and the property is founded in natural stiff clay away from the zone of influence from the former slope face. Written confirmation was provided to the property owner.