Creagh Concrete Limited

Brackagh QuarryGravity Dewatering

County: Tyrone.
Mineral: Glacial Sand and Gravel.
Project: Planning Application for Extension to Existing Quarry.
Planned Workings: Combined pumped and gravity dewatering during workings. Permanent gravity groundwater drainage following restoration.
Mitigation: Provision of support drainage to adjacent wetland plant habitat.
Approximate Consented Reserve: 6mt.
Project Areas: EIA, FRA.

The potential for continued working, expansion and restoration of Brackagh Quarry to impact upon the water environment was assessed as part of an EIA undertaken by BCL.

No site specific hydrogeological data were available at initiation of the study. BCL provided a specification for piezometers drilling that led to the installation of a network of piezometers. Monitoring data provided by the piezometers network assisted the understanding of local hydrogeological conditions. This quickly established that, contrary to established understanding, workings at the quarry had extended below the watertable for many years prior to the planning application. Within this context, a planning application was formulated that sought to expand the area of subwatertable workings for the maximisation of recoverable reserve within the area available to the applicant.

Working closely with ecological and geological specialists, and using the results from computer-based numerical ground-water flow modelling, BCL designed a system of gravity drainage for the quarry. The intention of this system is to allow the quarry to be worked for a significant part of its anticipated lifespan without recourse to pumped dewatering and to provide sufficient drainage to ensure a sustainable agricultural restoration for the Site.

Study found that the proposed workings would cause a localised re-balancing of the existing groundwater / surface water relationship, with the effect of altering stream flow rates. However, computer modelling demonstrated that these effects would be extremely localised. Mitigation measures were devised for the safeguarding of an important botanical habitat that ecological survey found to border the proposed extension. The potential for impact upon a single nearby water supply well was satisfactorily mitigated by a commitment by the operator to provide an alternative supply should it be required.

EIA: Environmental Impact Assessment.
FRA: Flood Risk Assessment.