The site had been variously used from the 1880’s as rail sidings with a goods station, associated works buildings and crane tracks; industrial and commercial buildings; an engineering works; a petrol station with garage and a scrap yard. The site was also affected by underground mining for limestone and was subjected to a partial programme of mine stabilisation in 1991/1992.
The Client wished to redevelop the site with housing including three and four storey apartment blocks.
Georisk undertook a detailed intrusive ground investigation to assess the contamination and foundation aspects for the proposed development. The site investigation comprised the excavation of trial pits, the sinking of shallow percussion boreholes and the drilling of deeper rotary boreholes to investigate the former abandoned mineworkings. The investigation indicated that the past mining activities had left voids below ground between 3.20 and 3.69m thick in addition to remnant crownhole collapses.
A detailed quantitative risk assessment was carried out in addition to a gas risk assessment to assess ground contamination aspects and to formulate a cost effective strategy to adequately deal with the problems identified.
The contaminated materials were excavated and removed from site; located underground fuel tanks and adjacent hydrocarbon impacted soils were also removed from site; clean blinding layers were then placed in all garden and landscaped areas. The areas of weak ground associated with the crownhole collapses were treated by grid drilling and grouting. Foundation solutions for differing buildings varied across the site to take into account the variable ground conditions.
Varney House, 91 Spon Lane, West Bromwich, B70 6AB
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