Humber River Basin District WFD Investigation
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Humber River Basin District WFD Investigation Mining Pollution: Catchment Characterisation Report (up-dated 10 January 2014) Project details Project name Gunnerside Gill catchment characterisation Contact John Barber, GWCL-Yorkshire Area NoCam assessment Probably Not Impacted: Score = 1: Rank = 355 (Eng) River length impacted Gunnerside Gill = 6km downstream of mines Mining Waste Directive inventory Yes (Bunton Lead Mine) Water body summary information Surface Water Body ID GB104027069090 (Humber River Basin District) Surface Water Body Name Gunnerside Gill (Gunnerside Beck) Surface Water Catchment Swale, Ure, Nidd & Upper Ouse (SUNO) Surface Water Body Type Mid, Small, Siliceous (Secondary River) Groundwater Body ID GB40402G701900 (Humber River Basin District) Groundwater Body Name SUNO: Millstone Grit & Carboniferous Limestone RBP Measure in WAP None (Good Status - but see below) RFF Database No Figure 1. Gunnerside Gill location within the Humber River Basin District (in pink) 1 Background information Surface water body classification Status in 2009 Ecological Status Good Biological Status Good General Physico-Chemical Status High Hydromorphological Status Not High Hydromorphological Designation Not a Heavily Modified Water Body Specific Pollutants Overall High Chemical Status Does Not Require Assessment Groundwater body Status Confid Predicted Reason for not classification in 2009 -ence Status achieving good status Disproportionate cost Chemical Status Overall Poor High Good by 2027 Technically infeasible Saline Intrusion Good High Good - Surface Water Impacts Poor Low Good by 2027 Technically infeasible Wetland (GWDTE) Impacts Good Low Good - Drinking Water Protected Area Poor High Good by 2027 Disproportionate cost General Chemical Assessment Poor Low Good by 2027 Technically infeasible Upward Pollutant Trend Yes - - - Figure 2. Gunnerside Gill catchment location 2 Pollution from abandoned metal mines adversely impacts both surface water quality and aqueous ecology with potential reduction in WFD status. The metal pollution derives mainly from minewater discharges out of drainage adits/levels, spoil tip run-off, and spoil tip erosion. Metal bearing river sediments are remobilised during high rainfall and high river flow events then transported downstream with potential spreading onto floodplains used for farming. Gunnerside Gill (8km long), located in the northern part of the Humber River Basin District (see Figure 1 above), is a steep-sided tributary of the River Swale in the Yorkshire Dales National Park; with the confluence some 29km upstream of Richmond. Gunnerside Gill catchment (13km2) is shown in Figure 2 above, with recent water quality monitoring points shown as yellow circles. Gunnerside Gill drains a former lead mining area, where the minerals extracted included galena (PbS), sphalerite (ZnS) and barite (BaSO4). Gunnerside Gill was identified with elevated metal concentrations (Pb, Cd, Zn) in the EA Yorkshire Metal Mines Study (2010) from a single sample at the confluence of Barney Beck with the River Swale. These results were subsequently confirmed by a sampling programme conducted by Hull University in 2010 and by the EA in 2011 for the MWD project. These previous water quality results are summarised in the table below, where the metals identified are consistent with the ores formerly mined in the catchment; cadmium being an impurity in the main lead and zinc mineral ores The metal concentrations were compared to current 2013 annual average EQS values with exceedences high-lighted in pink in the table below. The EQS values for zinc, cadmium and copper are variable and depend on the hardness of the receiving waters. The mean hardness in the samples shown below was 67mg/L and in all the samples in this project the mean hardness was 74mg/L. These fall into the hardness band from 50-100mg/L and so the relevant EQS values are: 50g/L for zinc; 0.09g/L for cadmium; and 6g/L for copper. Pb Zn Cd Ni Cu Flow Date Location NGR (g/L) (g/L) (g/L) (g/L) (g/L) (L/s) Gunnerside Beck at Feb-10 SD951983 22 199 1.7 1.1 <1 500 Gunnerside Jul-10 Bunton Level Discharge NY940012 54 1285 10 2 2 2 Sir Francis Level Jul-10 NY934000 72 2003 12 5 2 12 Discharge Bank Discharge to Jul-10 SD941999 183 679 6 7 2 0.1 Gunnerside Beck Gunnerside Beck u/s Feb-11 NY939014 7 18 0.1 1.1 <1 - Bunton Level Bunton Level Feb-11 NY940012 41 780 8.3 3.6 <1 ~10 Discharge Gunnerside Beck d/s Feb-11 NY939012 10 40 0.4 1.3 <1 - Bunton Level Feb-11 Water Sykes NY940011 4 51 0.3 <1 <1 - Gunnerside Beck u/s Sir Feb-11 NY940000 19 56 0.6 1.1 <1 - Francis Level Gunnerside Beck d/s Sir Feb-11 SD941998 22 140 1.3 1.4 <1 - Francis Level Gunnerside Beck at Feb-11 SD951984 26 194 1.7 1.3 <1 - Gunnerside EQS Annual Average (g/L) 7.2 50 0.09 20 6 - The above water quality monitoring identified significant metal pollutants in Gunnerside Gill that were not originally identified in the first RBMP of 2009, because of the limited range of parameters in the routine analysis suite. 3 Mining Waste Directive The following sites in the Gunnerside Gill catchment are on the MWD Article 20 Inventory. URN Site Name Mine Type Reason Easting Northing MWD Inventory 1229 Bunton Lead Mine Metalliferous Water pollution 394258 501303 Potential MWD Inventory - none - - - - Other Potential Sites not on MWD Inventory - none - - - - Mining History Summary Gunnerside Gill drains an area of former lead mining, which was carried out extensively throughout the catchment from about 1700 to 1900, most actively in the 1800s, followed by some reworking of spoil tips until the 1990s. The orefield comprises lead-zinc mineral deposits within Carboniferous Limestone and Millstone Grit host rocks. Galena (PbS) is the most common mineral with associated ‘gangue’ minerals including sphalerite (ZnS), chalcopyrite (CuFeS2), barite (BaSO4), fluorite (CaF2) and calcite (CaCO3). These minerals occur mostly in vertical veins along fault planes, as shown on Figure 3, Figure 4 and on Figure 5 below. Early mine workings were open cuts, with shafts used to work deeper in later years, but exploitation was initially limited by the water table. The scouring technique of hushing was used until about 1850 to expose mineral veins at the surface by the erosive power of water released from temporary dams. Horizontal drainage levels (adits) were driven from the valley bottoms to enable deeper working and for easier removal of minerals from the mines. The ore was crushed and dressed at the surface close to the mines to further concentrate the metal before smelting at sites close to the mines. Water power was used at ore dressing floors and smelt mills and so these sites and their spoil tips are often located next to rivers. The main mining features in Gunnerside Gill catchment are as follows. Lead Mines NGR Adits/Levels Hushes Spoil Tips Smelters B Upper Blakethwaite Blakethwaite NY 9387 0295 B Lower Lownathwaite North Lownathwaite Sun Hush Sun Dolly Dolly Lownathwaite NY 9330 0133 Woodward Priscilla Blind Gill Bunton Bunton Bunton Water Sikes Friarfold Bunton NY 9398 0123 Sir George Gorton Barbara Sir Francis Sir Francis Sir Francis SD 9402 9996 Silver Hill Gunnerside Kining SD 9563 9926 Kining Kining 4 Figure 3. Aerial photograph showing mining scars along mineralised faults Figure 4. BGS map detail (1985) showing levels and mineral veins 5 Figure 5. BGS map (1985) showing levels and mineral veins 6 Historical Ecological Data Prior to the current project ecological sampling has generally been sporadic at best and Gunnerside Gill has not been sampled since the early 1990s. Prior to the project ecological sampling was primarily undertaken as part of the ‘headline indicator’ programme which formed part of the General Quality Assessment (GQA) classification. However as the GQA network was reduced Gunnerside Gill was removed from the programme. From 2013 routine sampling has been reinstated under the new Ecological Status Indicator (ESI) programme and will form the basis of WFD classification from 2014 onwards. Historic ecological monitoring events in the Gunnerside catchment are shown below, but the results have not been obtained as part of this study. Diat Inverte Macro Site Ref Site Name Date Fish Reason oms brates phytes 14/05/90 YES NO NO NO 15/08/90 YES NO NO NO Headline 30/10/90 YES NO NO NO Indicator 09/04/91 YES NO NO NO 02/03/92 YES NO NO NO 29/07/92 YES NO NO NO Local Routine 2002 NO NO NO YES ? 2003 NO NO NO YES ? 165 Gunnerside Gill at 2004 NO NO NO YES ? (GG6) Gunnerside 2005 NO NO NO YES ? 2006 NO NO NO YES ? 2007 NO NO NO YES ? 2008 NO NO NO YES ? 2009 NO NO NO YES ? 2010 NO NO NO YES ? 2011 NO NO NO YES ? 2012 NO NO NO YES ? 02/09/13 NO NO NO YES ? Despite coming back onto the WFD assessment programme the impact of metal pollution may not show up through WFD classification. This is because both of the relevant WFD classification tools, River Invertebrate Classification Tool (RICT) and Diatom Assessment of River and Lake Ecological Quality (DARLEQ), are underpinned by indices designed to assess specific pressures, but none of these are metal pollution. For invertebrates RICT uses two indices, Average Score Per Taxon (ASPT) and Number of scoring Taxa (NTAXA). ASPT is designed to measure the impact of organic pollution on an invertebrate community, so will not pick up the impact to metals. In fact many species that are known to be tolerant of metal pollution are intolerant of organic pollution. NTAXA is the number of different species present in a sample and is thus a measure of diversity of the invertebrate community.