Case Study: Trago Mills
Client: Charles Robertson
Engineer: C D Gray
Main Contractor: BAM Nuttall Ltd
Location: Merthyr Tydfil
Date: 2005 - 2006
BAM Ritchies undertook a major mine treatment contract on the site of a new retail store on a brownfield site near Methyr Tydfil. The site is in an old industrial area typical of many parts of the south Wales valleys and was a former brickwork. There are a number of old coal and ironstone tips on the site.
The work was undertaken in two phases. The first phase consisted of the search for and treatment of a number of mine entries. This work involved probing by drilling to locate the 18 shafts and adits thought to exist on the site. The second phase consisted of treating development areas by bulk infill grouting and constituted the main element of the contract.
Drilling was executed using five drill rigs equipped with hydraulic top hammers. Holes up to 45 metres deep were being drilled with up to 24 metres of casing being required through the made ground, overburden and boulder clay present on the site.
Approximately 4,100 holes were needed resulting in around 110,000 metres of drilling. Perimeter holes were 110mm diameter with the infill holes being drilled at 89mm diameter. Approximately 15,000 tonnes of PFA/OPC grout were injected to stabilise the workings under the store.
The whole treatment programme was complex owing to the site conditions and multi-seam geology. The bespoke silo based grouting plant and water course monitoring systems ensured tight environmental control.