Tunstead Works is one of the largest cement producing facilities in Europe. Tunstead Quarry supplies the works with limestone for cement production as well as providing aggregate for the regional market. A Review of Mineral Planning (ROMP) necessitated the preparation of an Environmental Impact Assessment (EIA), of which water issues were an important component. Hafren Water was commissioned to undertake a Hydrogeological Impact Assessment (HIA) to support the ROMP submission.
Tunstead Quarry is located approximately 4km east of Buxton, Derbyshire. Carboniferous limestone is extracted for use in cement manufacture as well as for general aggregate use and quarrying has been on-going since 1929.
A Review of Mineral Planning (ROMP) assessment is periodically required to ensure Planning Conditions are appropriate and that they keep abreast of changing environmental legislation. The ROMP assessment included both Tunstead Quarry and the adjacent Old Moor Quarry. A comprehensive and long-running programme of environmental monitoring is maintained at the site, including groundwater level data which is available from 1990 to date. This formed the basis of the hydrogeological assessment for the ROMP.
Future restoration of the site will be primarily to farmland and habitat creation for the ecological benefit, with areas of ephemeral water in the lowermost elevations of the restored quarry voids. Restoration is a continual process and upper benches have already been completed by restoration blasting, land forming and extensive planting with indigenous species.
The Peak District Dales Special Area of Conservation (SAC) lies in close proximity to the east, west and south of the quarries. The SAC incorporates three ecological Sites of Special Scientific Interest (SSSI): the Wye Valley, Topley Pike & Deep Dale, and Monks Dale SSSIs, which are located to the south and east of the quarry.
Both sites are thought to be groundwater-fed. The Wye Valley SSSI to the south extends eastwards for 15 km from approximately 1.5 km west of Tunstead. The importance of the water environment to the integrity of the SAC was such that the scrutiny by the regulators of the potential for the permitted future mineral extraction to impact upon it was intense. The assessment of water issues to support the ROMP submission, therefore, had to be extremely robust.
The limestone within the quarry and its surrounds are karstified, with well-documented occurrences of springs, and flushes. These groundwater-supported features have intrinsic value as well as creating habitats with high ecological interest. The resurgence of groundwater in the bed of the River Wye to the south of the quarry provides support to maintaining river flow, especially during low flow conditions.
An extensive programme of data collation and fieldwork was devised to generate baseline data of the water environment. The scope of the investigations was discussed in detail with the Environment Agency and a programme of work agreed. The fieldwork included the drilling of additional groundwater level monitoring boreholes, stream flow monitoring, installation of data loggers and pressure transducers in selected boreholes, downhole geophysical logging and tracer testing. The first stage of the assessment process was to create a robust conceptual model of the water environment which was ground-truthed using data generated from the fieldwork. The conceptual model was then used to identify where potential impacts arising from the permitted mineral extraction could potentially occur.
The results of the investigations indicated that the permitted maximum depth of working was above the definable water table. Furthermore, tracer testing and detailed knowledge of the development of karstification in the region indicated that it was highly unlikely that water filled fissures or fractures (termed conduits) would be encountered as quarry deepening proceeded.
The ROMP was submitted in 2013. Various matters were subsequently raised by the statutory consultees which led to supplementary information and comment being provided. The ROMP was determined favourably in 2017. A comprehensive environmental monitoring programme is maintained on site and reported to the regulators on a two-yearly basis.