Quarry Infilling

Client / Deeley Freed Estates
Site / Barnhill Quarry
Value / £3m
Timescale / 2 Years

Summary

Sanctus was appointed by Deeley Freed Estates to undertake the construction of a development platform within the former Barnhill Quarry to the north of Chipping Sodbury. The project comprised the restoration of the southern end of a quarry to ground level, where the floor is some 30m below surrounding ground level, to a standard where some 170 houses could be built upon it. In addition to the importation of material Sanctus had to contend with a high groundwater table that required the continuous pumping of water from the site to prevent the inundation of the works. The construction of the development platform required the importation of some 800,000m3 of soil to the site. In addition to the development platform, Sanctus were also required to construct an access ramp down to the base of the quarry to the north of the site.

As the works allowed for the importation of contaminated material to the site, Sanctus constructed a Soil Treatment Centre within the quarry to allow the importation of contaminated material to site whereupon it could be treated to decrease the contamination to a level agreed by the Environment Agency.

Sanctus were able to recover large volumes of contaminated material for re-use that would have otherwise been sent for disposal at landfill sites.

The granular material that was laid in alternating layers was obtained from the Hanson Quarry adjacent to the site and comprised the clean, waste stone that was not commercially viable for use.

Each contaminated soil type was stockpiled according to the type of contamination determined, with soil samples being collected to confirm the treatment had been successful prior to distribution of the material across the site. This allowed the material to then be reused onsite as part of the infilling works.

The construction of the platform comprised the deposition of alternating layers of cohesive and granular material approx. 300mm thick with each layer being compacted using a system known as LandPac that has been found to consolidate material with a greater efficiency than the traditional vibrating drum roller. Throughout the works the platform underwent numerous rounds of geotechnical monitoring to ensure its settlement to ensure a usable final level. This careful approach produced a platform suitable for the construction of some 170 houses within 2 months of its completion. Similar projects require the site to be allowed to settle for at least a couple of years before the construction phase could begin.