Terra Firma  was retained to act as Consulting geotechnical and geo-environmental engineers for the £30M Trago Mills development in Merthyr Tydfil.

We designed, supervised and certified the stabilisation of the underground shallow mine workings associated with the Garw coal and Big Vein and Rosser Ironstone Veins, and the treatment of mine adits. The stabilisation process required pressure grouting using a mixture of Pulverised Fly Ash (PFA) and Ordinary Portland Cement. The works involved the drilling of 100km of rock, 4000 holes and 15000 tonnes of grout.

Terra Firma also arranged all necessary permissions to undertake the works from the Coal Authority and Environment Agency.

Working closely with the Environment Agency, we undertook extensive monitoring of the groundwater beneath the site, local surface waters and artesian groundwater at Glyndrys Mine Shaft some 3.5km SE of the site to confirm that there was no risk to the aquatic environment/controlled waters from the injection of grout.

Terra Firma also provided urgent response and engineering advice for slope stability issues arising from colliery spoil tipping and destabilisation by water and underground mining features.

As part of the reclamation of 120 acres of former ironstone and coal mining land, we provided supervision, monitoring and certification of extensive earthworks at the site, involving 1.3 million cubic meters of colliery shale and boulder clay.

Terra Firma designed and implemented a comprehensive geo-environmental investigation of the site including ground gas monitoring, soil chemical analysis, human health risk and environmental assessments and site conceptual modelling in order to satisfy Part IIA of the Environmental Protection Act 1990.