Author

Dr Will Mayes, Dr Emma Gozzard, Dr Hugh Potter, Dr Adam Jarvis

Date

May 2005-December 2006

Project Type

Post-doctoral research

Subject

Environmental Science & Engineering

Datasets

OS County Series, National Grid; Geology (Bedrock, Superficial and Artificial sheets); OS 1:25000 rasters; OS Landform DTM

Sources: Digimap; hydrological and chemical data collected by Newcastle University and the Environment Agency

Dates/Editions: First-3rd Revision / 1969-1996

Scales: As available and as listed above.

Related Subjects

Hydrology, geology, chemistry

Key Words

Sustainability; GIS

Publishing Institution

Newcastle University and the Environment Agency

Summary

There has been considerable progress in developing treatment systems for point sources of mine water pollution in recent years; however there remains a knowledge gap in the characterisation and remediation of diffuse minewater sources. This study gathered data from the River Gaunless catchment, a historically heavily coal-mined catchment in the northeast of England. Reconnaissance field measurements and mapping exercises were undertaken to identify areas of potential mine water input to surface waters. Instream iron (Fe) loadings were monitored alongside loadings arising from point minewater discharges over a twelve month period to assess the dynamic importance of diffuse sources of mine water pollution. In low-flow diffuse sources account for around 50% of instream loading; a proportion which increases to 98% in high-flow conditions. The low-flow sources appear to be dominated by direct discharge of contaminated groundwater to surface waters in lower reaches of the catchment. In high-flow, spoil heap runoff from the extensive waste rock cover in the catchment (which amounts to 1.8% of the total catchment area) and instream resuspended Fe-rich sediments, which are both naturally occurring and derived from historic mining, become the dominant diffuse sources of Fe in the water column.

Aims

The aim of this research is to identify and quantify the dynamic contribution of point (e.g. mine adit drainage) and diffuse (e.g. spoil heap runoff) sources of mine water contamination (namely iron fluxes) in a heavily coal mined river catchment (River Gaunless, County Durham. This was achieved through the identification of point and potential diffuse sources of pollution in reconnaissance surveys and mapping exercises and the monitoring the contribution of these sources to instream iron (Fe) contamination through the catchment under varying flow conditions.

Methodology

The study catchment has an extensive history of coal mining for over 200 years up to the early 1980s. This mining activity has left a legacy of mine water pollution from various sources (e.g. contaminated groundwater, metal rich surface spoil heaps – see Figure 1). To identify these potential sources and sites, historic data-review exercises and reconnaissance water quality measurements were undertaken throughout the catchment. Mapping exercises were also undertaken to identify former mine sites and associated waste rock heaps. These spoil heaps have by and large been reclaimed since the closure of the mines (although they can still pose a pollution risk), such that they are not readily identifiable from contemporary OS maps. The full suite of historic maps available on Digimap cover the most active period of mining in the area and were therefore used to identify locations of former coal mines and their associated spoil (Figure 2). This data informed the design of the instream monitoring network through identifying potential sources of metal contamination from spoil heap runoff (i.e. sample points were then located upstream and downstream of areas of riparian spoil heap to quantify metal flux from them). Instream loadings of metals (i.e. flows and concentrations) were measured alongside loadings from point mine water discharges to highlight the relative contribution of point and diffuse sources under varying hydrological conditions throughout the 93km 2 catchment over a 1 year period.

Results/Outcome

The work identified the significant contribution of diffuse sources of mine water pollution which contributed to between 45% (low flow) and over 95% (high flow) of instream Fe contamination. The research also highlighted the modes of diffuse transfer in the catchment which included direct groundwater discharge to surface waters (which predominates in low flow), run-off from the extensive cover of waste spoil and resuspension of contaminated bed sediments (which dominate in high flow conditions) (ref:1-3). The work was funded by the Environment Agency (the chief environmental regulator in England and Wales) and has informed their policy with regard management of diffuse mine water sources, particularly in light of the recently implemented European Union Water Framework Directive. The outputs of the work have also been cited in an important Defra (Department for Environment, Food and Rural Affairs) consultation document on diffuse pollution issues in the UK (ref:4).

A free publication from the Environment Agency including and related to this research can be downloaded here.

Images

	Figure 1: A point mine water discharge in the River Gaunless, highlighting the legacy of aquatic pollution from former coal mining activity
	Figure 2: Former coal mine sites and the extent of colliery spoil – a potential source of mine water pollution - in the Gaunless catchment derived from historic Digimap data.

Acknowledgements

The work was funded by the Environment Agency under project SC030136/3. The views expressed here cannot be construed as representing those of the funding organisation. With thanks to the Hydrogeochemical Engineering Research and Outreach Group (HERO), The Sir Joseph Swan Institute, Institute for Research on the Environment and Sustainability (IRES)-University of Newcastle.

References

Mayes, W.M., Gozzard, E., Potter, H.A.B. and Jarvis, A.P. (2007). Quantifying the importance of diffuse minewater pollution in a historically heavily coal mined catchment, Environmental Pollution, in press, accepted February 2007. DOI: 10.1016/j.envpol.2007.02.008

Mayes, W.M., Gozzard, E., Potter, H.A.B. and Jarvis, A.P. (2006). Identifying diffuse sources of inorganic pollutants in post-industrial catchments. Proceedings of the 4 th CIWEM Annual Conference: Emerging environmental issues and future challenges, 12-14 September 2006, Newcastle upon Tyne, UK.

Mayes, W.M., Jarvis, A.P. and Younger, P.L. (2005). Assessing the importance of diffuse mine water pollution: a case study from County Durham, UK. Proceedings of the 9 th International Mine Water Congress, Oviedo, Spain 5-7 September, 2005, pp.497-505.