LISHEEN MINE DOCUMENT TO SUPPORT THE APPLICATION TO THE EPA FOR A NEW CONSENT LIMIT FOR AMMONIA

Transcription

1 LISHEEN MINE DOCUMENT TO SUPPORT THE APPLICATION TO THE EPA FOR A NEW CONSENT LIMIT FOR AMMONIA October /R4 Prepared for: Lisheen Mine Killoran, Moyne Thurles Co Tipperary Republic of Ireland Prepared by: 23 Swan Hill Shrewsbury Shropshire SY1 1NN

2 CONTENTS Page 1 INTRODUCTION Background Ammonia concentrations Clarification of terminology Report objectives 2 2 RIVER USAGE Potable water supplies Livestock watering Irrigation Aquatic life 3 3 RIVER FLOWS Natural flow conditionsa Mine water discharge 6 4 WATER QUALITY Baseline water quality Discharge water quality Ammonia concentrations in the rivers The Drish The Rossestown Dissolved Oxygen concentrations in the rivers Assessment of downstream ammonia concentrations for increased ammonia limits 11 5 ECOTOXICOLOGY Literature review Ammonia Dissolved Oxygen Fish trials Ecological impacts of elevated ammonia concentrations in the discharge Assessment of factors influencing fish life 19 6 SUMMARY, CONCLUSIONS & IMPACT ASSESSMENT Impact assessment Summary & Conclusions 21 7 REFERENCES 23

3 Contents TABLES 3.1 Estimates of natural flows in the Drish at various points downstream for median and low flow conditions Estimates of natural flows in the Rossestown at various points downstream for median and low flow conditions Summary statistics for Total Ammonia for June 1st to August 31st Partitioning of NH3/NH4 as determined by ph and temperature ph dependent toxicity for total ammonia (Salmonid fish, 30 o C; US EPA, 1985) Guidelines for Ammonium, Ammonia & Dissolved Oxygen for salmonid rivers Toxicity data (1 day LC50 s) used for the effect probability plots for the mine water discharge (data derived from US EPA Aquire database) Toxicity data (1 day LC50 s) used for the effect probability plots for the mine water discharge (data derived from US EPA Aquire database) (continued) Factors influencing fish species composition Factors influencing fish species composition (continued) 20 FIGURES 3.1 Flow duration curves (1 day duration) for the Drish River and Rossestown River, Ammonia concentrations at the two discharges Ammonia concentrations in the Drish recorded by Lisheen Ammonia concentrations in the Drish recorded by the EPA Ammonia concentrations in the Rossestown Dissolved Oxygen concentrations in the Drish recorded by Lisheen Dissolved Oxygen concentrations in the Drish recorded by the EPA Dissolved Oxygen concentrations in the Rossestown Estimated percentile end of mixing zone ammonia concentrations for a 1.5mg/l discharge Estimated percentile end of mixing zone ammonia concentrations for a 2 mg/l discharge Estimated percentile end of mixing zone unionised ammonia concentrations for a 1.5 mg/l discharge Estimated percentile end of mixing zone unionised ammonia concentrations for a 2 mg/l discharge Joint probability curve/exceedance profile for the Drish, derived from exposure and toxicity probability functions and based on a constant discharge concentration of 1.5 mg/l ammonia. 20

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5 1 1 INTRODUCTION 1.1 Background The Lisheen Mine operates a groundwater dewatering system. In order to maintain safe working conditions, groundwater from the mine is continuously pumped to the surface. More than 65% of the water is collected directly from natural fracture systems occurring underground and does not have any significant contact with the mine workings. A portion of this water is collected from the workings themselves and is pumped to the water treatment plant. Excess water from the tailings management facility is also pumped to the water treatment plant. The natural groundwater and treated water are mixed in the conditioning pond system. The mixed water is discharged via pipelines into the Drish and Rossestown Rivers. The discharge points are located some 15 and 12 km, respectively, upstream of the River Suir. Lisheen must meet a series of water quality conditions at the discharges which are laid out in their Integrated Pollution Control License (IPCL). 1.2 Ammonia concentrations The current consent limit for Total Ammoniacal Nitrogen is an 80 percentile of 1 mg/l (0.78 mg/l as N) with a maximum allowable concentration of 1.2 mg/l (0.94 mg/l as N). This limit poses difficulties for the mine operation and current discharge values are typically in excess of the current consent limit. Part of the natural groundwater that flows towards the mine comes from beneath an area of bog to the east and northeast. Natural ammonium levels in the groundwater beneath the bog are typically greater than 5 mg/l. As a result, future management of ammonium to comply with the discharge limit of 1 mg/l is not practical. The current discharge limit of 1 mg/l will also impact on the ability to manage the water such to achieve an optimised final closure and reclamation programme for the site. Treatment of the water volumes at Lisheen to 1 mg/l total ammonium would be technically very difficult and cost prohibitive. Total ammonium values in excess of 1 mg/l already occur upstream of the mine discharge locations, particularly in the Rossestown as a result of sewage treatment discharges.

6 Introduction Clarification of terminology Confusion is often created through the terminology used in ammonia assessments. The following clarifies the accepted terminology and explains the terminology used throughout this report: Ammonia: Compound with the formula NH 3. Usually present as a gas but also present in solution as un-ionised ammonia. It is the un-ionised form of ammonia that is toxic to aquatic life. It is not practical to analyse for ammonia in solution and concentrations are calculated from Total Ammoniacal Nitrogen analyses using ph and temperature data. Ammonium: Cation with the formula NH 4. Also known as ionised ammonia. Total Ammoniacal Nitrogen/Ammoniacal Nitrogen/Total Ammonia: These three terms are used to describe the sum of ammonia species in solution which equates to the sum of dissolved ammonia gas, or unionised ammonia, and the ammonium ion, or ionised ammonium. This is often referred to in chemical analysis as ammonia and all chemical analysis undertaken by Lisheen and the EPA refers to this parameter. Throughout the course of this memo ammonia will actually refer to Total Ammoniacal Nitrogen and dissolved ammonia will be referred to as un-ionised ammonia. A second source of confusion arises from the units of measurement which can either be mg/l or mg/l as N. All values discussed and plotted in this report are in mg/l. These values can be converted to mg/l N by multiplying be Report objectives The objectives of this report were to: Present all relevant information on river usage and receptors. Review all available data on river water biology, flows and water quality. Review the results of fish trials and evaluate the key factors influencing aquatic life in the rivers. Assess the likely the impacts of elevated ammonia concentrations in order to determine the maximum acceptable discharge limit for ammonia. If appropriate, suggest an increased discharge limit for ammonia and any works required to confirm the acceptability of this revised limit.

7 3 2 RIVER USAGE The purpose of this section is to describe the usage and status of the rivers, the potential receptors and their sensitivity to ammonia. 2.1 Potable water supplies The EPA compiled National Abstraction Register has been reviewed to confirm the locations of potable water supplies on the Drish, Rossestown and Suir Rivers. There are no sources of public water supply on any of these rivers. Checks for abstractions from the Suir were carried out down to Waterford. The only potable water supplies obtained from surface waters are those at Clonmel. It has been confirmed through discussions with Clonmel Borough Council that these abstractions are taken from two tributaries of the Suir River, not the Suir River itself. It has therefore been confirmed that there are no potable water supplies downstream of the mine discharges. 2.2 Livestock watering Livestock watering is an important use of water in the Drish and Rossestown catchments. The WHO 2003 background paper (WHO, 2003) states that LC50 s for animals are typically n the range of 350 to 750 mg/kg of body weight. The same paper concluded that Ammonia is not of direct importance for health in the concentrations to be expected in drinking-water. A health-based guideline has therefore not been derived. It is therefore clear that ammonium concentrations in the 1 to 2 mg/l range will have no impact on livestock. WMC have not been able to locate any specific livestock drinking water standards for ammonia. 2.3 Irrigation It has not been possible to confirm whether the Drish, Rossestown and Suir are used for irrigation although any such use will be limited, if indeed it happens at all. Ammonia in irrigation water will have no detrimental impact on crops and ammonia compounds are frequently applied as fertilizers. The FAO (1985) state that the normal range for ammonia in irrigation water is 0 5 mg/l. 2.4 Aquatic life Alongside cattle watering, fishing is one of the main uses of the Drish and Rossestown Rivers. Although neither are listed in SI as salmonid rivers, the Drish would be considered to have better fishing with a population of trout. Of all the receptors on the Drish and Rossestown salmonid species are by far the most sensitive to elevated ammonia concentrations.

8 River usage 4 The biological status of river waters in Ireland is assessed using the Q-system. This is based on the species and abundance of aquatic invertebrates collected in a kick-sample. The pollution tolerance of the organisms has been assigned to a five point scale from which is computed a Q-value ranging from 1 to 5. This scoring system is based on the sensitivity of the organisms to organic pollution and dissolved oxygen, and may not correlate well with other pollutants. Values of 4 and 5 indicate good to excellent water quality and are expected to represent waters of good ecological status as defined by the Water Framework Directive (WFD). Biological surveys and assessments have been carried out at six sites on the Drish River in 2004, 2005 and 2006 (Sweeney, 2006). Sites 100 m upstream of the discharge and at Longfordpass (5 km upstream) have values of Q2-3; essentially the same as the 100 m downstream values. Further downstream, at bridges northeast and northwest of Castletown, and at Boolabeha Bridge, the values only reach Q3. Although further examination of the invertebrate groups present and their abundance at these sites revealed some effects relating to sedimentation and possibly metal toxicity, no impacts can be directly attributed to elevated ammonia levels. Biological data are not available for the Rossestown. There is no recent detailed macrophyte survey of the rivers in the region of the discharge points. The brief description and photographs in the referenced biological survey report indicate healthy river margins, typical of freshwaters. Early surveys conducted in 1983 indicated the presence of a diverse aquatic plant community upstream and downstream of the discharge points. Surveys conducted for the baseline (RPS Cairns, 1992) and the recent biological surveys show an increased presence and coverage of filamentous algae growth upstream and downstream of the discharge points, probably because of increased plant nutrients such as phosphates and nitrates.

9 5 3 RIVER FLOWS The Lisheen mine discharges into both the Drish and Rossestown rivers, which are lowland streams whose headwaters are peat bogs. Both rivers are also tributaries of the Suir River which is situated approximately 15km downstream of the Lisheen discharges. 3.1 Natural flow conditions River gauging stations operated by the Office of Public Works are located on the lower Drish River (16001 Athlummon) and Rossestown River (16051 Clobanna) towards the confluences with the Suir River. Flow duration curves have been calculated for the premine discharge years of and standardised by dividing the flows by the catchment area of each river gauging station (Figure 3.1). Catchment areas have been estimated for the various monitoring locations downstream of the mine. The catchment areas and unit flows from Figure 3.1 have been used to estimate natural flows at the downstream locations for median (50 percentile) and low flow (95 percentile) conditions. These flows are presented for the Drish and Rossestown rivers in Tables 3.1 and 3.2 respectively. Table 3.1 Estimates of natural flows in the Drish at various points downstream for median and low flow conditions Location Distance from mine water discharge km Catchment Area km 2 50 percentile m 3 /s 95 percentile m 3 /s Castletown Bridge (d/s sampling site) Second bridge Castletown Boolabeha Bridge Ballyduff Bridge Athlummon gauging station (16001) Drish Bridge Suir River confluence

10 River usage 6 Table 3.2 Estimates of natural flows in the Rossestown at various points downstream for median and low flow conditions Location Distance from mine water discharge km Catchment Area km 2 50 percentile m 3 /s 95 percentile m 3 /s Downstream sampling point Derryville Lisaticy Bridge Kilclonagh Bridge Ballyduag Bridge Clobanna gauging station (16051) Suir River confluence Mine water discharge Typical mine water discharge rates are around 0.19 m 3 /s for the Rossestown and 0.81 m 3 /s for the Drish. The maximum consented discharge rates (as per the IPCL daily limit) are 0.23 m 3 /s for the Rossestown and 1.16 m 3 /s for the Drish. A comparison of these discharge rates with the natural flow conditions clearly illustrates the influence the mine discharge has on the flow regime of the rivers. Typical mine water discharges to the Rossestown are around 90% higher than the natural median flow and around 21 times the 95 percentile low flow. During low flow periods the mine water discharge to the Rossestown will account for more than 80% of its flow at the confluence with the Suir 15km downstream. Typical mine water discharges to the Drish are around 40% higher than the natural median flow and around 15 times the 95 percentile low flow. During low flow periods the mine water discharge to the Drish will account for for more than 80% of its flow at the confluence with the Suir 15.5 km downstream.

11 7 4 WATER QUALITY 4.1 Baseline water quality Baseline water quality analysis was undertaken at five locations along the Drish (RPS Cairns, 1995) during the baseline monitoring programme which ran from August 1991 to July Dissolved oxygen data was high during each of the five baseline sampling rounds with all readings in excess of 9 mg/l. This may be a reflection on the flow rates at the time of the sampling events as the data produced by the Kilkenny Regional Water Laboratory showed dissolved oxygen levels dropping as low as 66% saturation. High ammonia concentrations were detected with a value of 0.09 mg/l unionised ammonia being recorded at the Boolabeha bridge on the Drish. Values in excess of 0.02 mg/l were also recorded at the Drish Bridge. Relatively elevated values of BOD were also recorded. Samples from the tributaries of the Drish showed some very poor water quality with very low dissolved oxygen levels and BOD readings up to 39 mg/l. Elevated ammonia readings were also recorded in the tributaries of the Drish. A total of six water quality monitoring sites were set up on the Rossestown for the baseline sampling programme. The impact of the Templetouhy sewage effluent is clearly evident with total ammonia concentrations as high as 2.21 mg/l being recorded. Slightly depleted dissolved oxygen levels are also reported downstream of the effluent discharge. There is an increase in dissolved oxygen and a decrease in total ammonia concentrations in the sampling sites further downstream as the impacts of the sewage effluent are reduced through dilution. 4.2 Discharge water quality Ammonia in the discharges at Lisheen has come from: 1) Natural elevated groundwater concentrations, especially in the Bog Zone deposit 2) Ammonia based reagents used in the process plant, ammonia based explosives in the mine The vast majority of the ammonia has historically come from groundwater and Lisheen stopped using ammonia based reagents in the plant during early 2007 in a bid to minimise ammonia concentrations in the discharge. This ammonia was partially the reason for the elevated ammonia levels in the TMF (~7mg/l). It is not possible to source non-nitrogen based explosives; however water sampling before and after blasting show that explosives contribute a very small quantity to the overall ammonia burden.

12 Water quality 8 The historical time series trend for total ammonia at the Drish and the Rossestown discharges is shown in Figure 4.1. The discharge data should be treated with a degree of caution for the following reasons: 1) The sampling device in place at the Drish discharge was shown to under estimate the total ammonium concentrations for a periods up until late This issue has now been resolved. 2) There is believed to have been some natural biological breakdown of ammonia in the pipeline that discharges to the Rossestown prior to mid 2006, an increase in the discharge volume through this pipe appears to have halted this process. 3) Analytical problems in 2003 resulted in a delay in analysing some samples and insufficient stabilising resulted in a loss of ammonia prior to analysis. Despite the uncertainties that result from these three factors the data can still be used to evaluate general trends in the dataset. The data show that elevated ammonia was present in the discharge during 2001 and 2002 with concentrations frequently exceeding the discharge limit of 1 mg/l. Concentrations then subsided and remained within the consented limits through until late 2006 when dewatering of the Bog Zone ore body commenced. At this time there was also an increase in the rate of reclaim water from the TMF to reduce the water cover and provide emergency water storage. Total ammonia concentrations peaked between November 2006 and mid January 2007 at between 2 and 2.5 mg/l at the discharges. Total ammonia concentrations have since declined and recent data indicates that the majority of readings are in the 1 to 1.5 mg/l range. This decline in ammonia is likely to be due to a combination of two factors: A reduction in flow from Bog Zone with a corresponding drop in ammonia loading. A possible improvement in Bog Zone water quality as oxidising recharge waters replace the reduced groundwater that made up the initial abstractions. The phasing out of ammonia based reagents in the process plant will take up to 18 months to have a substantial impact on the ammonia concentrations in the TMF water. After this time it is expected that TMF water will be reduced from its current 7mg/l to 2-3mg/l (the approximate concentration in dirty water in the mine. Trials into passive nitrification in the conditioning ponds are taking place and it is possible that these are having a knock-on effect at the final discharge. Summary statistics for the ammonia concentrations at the two discharges are shown in Table 4.1. The results indicate the high level of correlation between the two discharges which shows that conditions within the two discharge pipelines are comparable. It is also believed that there is negligible breakdown or ammonia within the pipelines although current data is not available for the point of entry, previous monitoring campaigns have shown this to be the case. The statistics presented in Table 4.1 show that Lisheen is currently exceeding is IPCL limit between 35 and 42%. The IPCL states that the eighty percentile should be 1 mg/l and the maximum 1.2 mg/l

13 Water quality 9 Table 4.1 Summary statistics for Total Ammonia for June 1 st to August 31 st 2007 Drish discharge Rossestown discharge Maximum %ile %ile Median Ammonia concentrations in the rivers The water from the conditioning pond discharges into the Drish River at point PWE-1 and into the Rossestown River at point PWE-2. The Drish is the larger of the two discharges. For each river, Lisheen analyses both the discharge and the river water at locations downstream of the discharge point on a daily basis for a range of determinants. Weekly upstream samples are also analysed, other sites are analysed at a weekly or monthly frequency. The EPA also undertakes quarterly sampling of both rivers. EPA data is available for six locations on the Drish, one of which is upstream, and three locations on the Rossestown, all of which are downstream The Drish Figure 4.2 shows the Drish river water quality data collected by Lisheen. During low river flows, some upstream migration of the discharge occurs because the Drish is fairly wide and deep near the discharge point, with low water velocity. As a result there is some evidence of upstream water quality being impacted by the mine water discharge at times of low flow. A review of sulphate data suggests that mine discharge influences the upstream water quality in about 15% of the samples collected. This complicates the interpretation of upstream ammonia data although there are a number of occasions when upstream concentrations exceed those downstream which does suggest that there are sporadic inputs of ammonia from other sources upstream of the Drish. The downstream sampling point on the Drish is 300 m downstream of the discharge point so concentrations are likely to be representative of mixed conditions. The data indicates that ammonia concentrations have historically been within the limits of the IPCL with the exception of two samples that exceed the 1.2 mg/l maximum. Recent data has however exceeded the maximum with readings of 1.4 and 1.6 mg/l in the last two sampling rounds. The second downstream sampling point (2 nd bridge, Castletown), which is about 1.5km downstream, has historically shown ammonia concentrations that are substantially lower with all but one reading below 0.6 mg/l (which equates to half the IPCL maximum limit). The only reading above 1 mg/l was recorded April It is not clear if this elevated reading is associated with mine water discharge. Significant dilution of the discharge would normally be anticipated in April which would suggest that some other source of ammonium may be responsible but no flow data is available to confirm this. However, there are clearly other sources of ammonia in this area. A limited number of samples are available for a drain outfall at the Castletown bridge where ammonia concentrations frequently exceed 2 mg/l with a maximum of 31 mg/l.

14 Water quality 10 Water quality at Boolabeha bridge which is about 4.5km downstream of the discharge is consistently well within the IPCL limits with an average concentration of 0.14 mg/l and a maximum of 0.5 mg/l. The EPA data for the Drish is shown as Figure 4.3. The data corresponds well with the Lisheen data for the sampling points near the mine. The EPA also sample at Athlummon (8.5km downstream), the Drish bridge (12.5 km downstream), and upstream of the Suir confluence (15.5 km downstream). Maximum ammonia concentrations at these locations are 0.33, 0.23 and 0.18 mg/l respectively The Rossestown Ammonia concentrations for the Rossestown are shown on Figure 4.4. Lisheen sample the river upstream and downstream of the outfall. The upstream water quality on the whole is generally worse than the downstream with respect to ammonia and a number of spikes are evident in the dataset. These spikes are thought to be associated with discharge from the Templetouhy sewage treatment works although it is possible that other upstream sources of ammonia are responsible. Downstream water quality has historically been good with no exceedances of the 1.2 mg/l IPCL maximum that cannot be attributed to upstream sources of ammonia. The EPA do not collect any upstream data but results from the downstream sampling point correspond well with the Lisheen data. The EPA also collect data at two sampling locations further downstream at a bridge west of Ballyerk (the precise location of this site is not known but it is thought to be approximately 6km downstream), and upstream of the Suir confluence (15km downstream). Downstream concentrations on the Rossestown are generally slightly higher than on the Drish with maximums of 1.47 and 0.6 mg/l respectively at the two downstream sampling locations. The EPA sampling round in March 2007 showed a rising trend in downstream concentrations at all three sites although only the site immediately downstream was in excess of the IPCL maximum. Ammonia concentrations had dropped to 0.62 mg/l, or about half the IPCL maximum at the second downstream sampling location. Ammonia concentrations at the upstream sampling location also showed elevated concentrations shortly after the EPA sampling round so the elevated ammonia concentrations are likely to be attributable to a combination of the Lisheen discharge and the upstream sources. 4.4 Dissolved Oxygen concentrations in the rivers Dissolved oxygen concentrations upstream of the mine discharge on the Drish regularly decrease below 5 mg/l dissolved oxygen during the summer months. Readings between 2 and 3 mg/l are present in both the Lisheen and EPA datasets (Figures 4.5 & 4.6 respectively). It is noteworthy that all of these readings are taken during the day; there is a strong diurnal variation in dissolved oxygen concentrations with daytime concentrations exceeding night-time concentrations. Photosynthesis is responsible for the increased dissolved oxygen concentrations and this only occurs during daylight hours. Dissolved oxygen concentrations can be considerably higher in the late afternoon than they are shortly before sunrise. This would suggest that neither the EPA or the Lisheen datasets pick up the true minimums in dissolved oxygen concentrations as they are likely to occur shortly before sunrise. These low dissolved oxygen levels recorded upstream on the Drish are probably associated with low flow conditions and relatively high plant cover. Dissolved oxygen concentrations downstream of the mine discharge are considerably higher as a result of the increased flow. It is clear that the mine discharge has a positive impact on the Drish with respect to dissolved oxygen.

15 Water quality 11 On the Rossestown the mean dissolved oxygen levels are generally higher than on the Drish with only the occasional upstream value dropping below 5mg/l. There is a very good correlation between the upstream and downstream concentrations recorded by the mine (Figure 4.7). The EPA do not record upstream water quality on the Rossestown but their downstream datasets indicate concentrations within the same range as the Lisheen dataset. 4.5 Assessment of downstream ammonia concentrations for increased ammonia limits The following section presents an assessment of potential downstream water quality for a total ammonia discharge concentrations of 1.5 mg/l and 2 mg/l respectively, which corresponds to a 50% increase and a doubling of the current IPCL limit respectively. The flow data presented in section 3 have provided flow statistics that have been used to estimate the concentration of ammonia downstream of the discharge points for potential discharge consent limits of 1.5 and 2 mg/l. A background upstream ammonia concentration of 0.24 mg/l for the Drish and Rossestown rivers has been used in the calculations based on the upstream ammonia concentrations recorded in the period. Figures 4.8 and 4.9 show the probability distribution of ammonia concentrations at the downstream sampling points on the two rivers for constant discharge concentrations of 1.5 and 2 mg/l respectively. The low level of dilution that is present at times of low flow is clearly illustrated with 95 percentile downstream concentrations of around 1.4 and 1.85 mg/l. Probability plots for the more toxic unionised ammonia concentrations (Figure 4.10 & 4.11) have also been generated using typical average ph and temperature data recorded by the EPA during August and September sampling events. These two months corresponds with the typical periods of low flow and will therefore be most relevant for the minimum flow and maximum concentration events. The unionised ammonia is higher in the Drish despite the total ammonia being lower because the ph is fractionally higher. The ammonium-unionised ammonia equilibrium is extremely sensitive to ph and any minor variation in ph will result in a significant variation is unionised ammonia concentrations. The ph and temperature data from the Rossestown is such that the salmonid standard (see section 5) is unlikely to be exceeded at any point for a discharge of 1.5 mg/l. This plot does not however take account of the occasional spikes in ammonia concentrations associated with upstream sources so some exceedances of the standard are possible when upstream concentrations exceed the 0.24 mg/l total ammonia assumed in the calculations. Unionised ammonia concentrations in the Drish are higher than those in the Rossestown due to the slightly higher ph values. There is only a minor exceedance of the salmonid standard for a 1.5 mg/l discharge and the maximum concentration remains below 0.03 mg/l unionised ammonia. Figure 4.11 shows the unionised ammonium probability plots for a discharge concentration of 2 mg/l total ammonium. This plot shows that the salmonid standard of mg/l will be exceeded for more than a third of the time on both the Drish and Rossestown rivers. Maximum concentrations will approach 0.04 mg/l on the Drish and be in excess of 0.03 mg/l on the Rossestown. The potential impacts of such concentrations on aquatic species are discussed in section 5.

16 Water quality 12 Concentrations of ammonia further downstream have been estimated but the results are of little value due to uncertainties surrounding ammonia breakdown rates. If it is assumed that ammonia is a conservative parameter, predicted concentrations at times of low flow were excessively conservative with concentrations upstream of the Suir confluence of around 90% of the mine discharge concentration. Water quality data described above clearly indicate that breakdown is occurring as downstream concentrations are a fraction of those at the discharge, even during the summer months when dilution is likely to be very low. It has not been possible to quantify ammonia breakdown rates using available water quality data as there is no flow data for the sampling locations which can be used to separate out the influences of ammonia breakdown and dilution. A review of the ammonia data has however been undertaken and it is clear that significant breakdown of ammonia is occurring in the rivers within a relatively short distance downstream. Ammonia concentrations recorded by the EPA typically reduce by more than half between the first and second downstream sampling points for example. If anything the reduction appears to be greater during summer months when flows are likely to be lower. This is probably an indication that the breakdown rates are increasing with increasing water temperature, and may also signify that seasonal variation in breakdown rates actually has a greater bearing on the downstream concentrations than the seasonal changes in the dilution capacity. Travel times to downstream sampling points will also be greater during the summer months due to the lower flow velocities, and this will also serve to increase the amount of breakdown over a given stretch of the river.

17 13 5 ECOTOXICOLOGY 5.1 Literature review Ammonia As discussed in the introduction, ammonia comprises two discrete un-ionized (NH 3 ) and ionized (NH + 4 ) aqueous species. Partitioning between NH 3 and NH 4 is critical to the ecotoxicological impact of any given ammonia concentration or load and, as such, a total ammonia reading in isolation provides only a generalized indicator of potential ecotoxicological risk. Dose-response curves for virtually all aquatic fauna (including salmonids) become more acute as the partial contribution of NH 3 increases. With few exceptions, this occurs with increasing ph, and to a lesser extent with increasing temperature. The partitioning between unionised ammonia and ammonium can be approximated using the following formula: NH 3 = Total Ammonia / ( pH ) + (2730 / ( Temperature)) Tables 5.1 and 5.2 show in general terms the influence of ph and temperature upon the toxicity of total ammonia to salmonids as a result of the changing ratio of the more toxic unionised NH 3 to NH 4. Table 5.1 Partitioning of NH 3 /NH 4 as determined by ph and temperature Percent of total ammonia as NH 3 Temp ph 6.5 ph 7.0 ph 7.5 ph 8.0 ph 8.5 (oc)

18 Ecotoxicology 14 Table 5.2 ph dependent toxicity for total ammonia (Salmonid fish, 30 o C; US EPA, 1985) Duration PH LC50 total ammonia (mg/l) 1 hour day hour day hour day hour day hour day 0.17 The US-EPA and federal fisheries authorities apply ph-dependent total ammonia toxicity criteria to reflect the variability in ammonia toxicity with ph (Table 5.1). Temperature and dissolved oxygen levels also influence ammonium toxicity and so should also be factored into specific site assessments. Generally increase in temperature increases the proportion of unionised ammonia; a rise of 10 o C can double the concentration of unionised ammonia. However the effect of temperature on species sensitivity to ammonia is variable both within and between different taxonomic groups of organisms. Low dissolved oxygen levels also increase the toxicity of unionised ammonia but the degree of this effect is dependent upon the concentration of free carbon dioxide in the water and again the relationship is not straightforward. In general; higher CO 2 concentrations reduce the magnitude of increase in toxicity that results from the lowering of dissolved oxygen level. The total ammonia and unionised ammonia guidelines related to salmonid rivers are listed in Table 5.3. Not all ammonia guideline levels that have been derived take account of the variation of toxicity with physicochemical conditions of a waterbody into which a discharge occurs. However this is a valid consideration on a site by site basis and the recent EU directive recognises this by qualifying the prescribed standard of 1 mg/l Total Ammonia with the following statement: In particular geographical or climatic conditions and particularly in cases of low water temperature and of reduced nitrification or where the competent authority can prove that there are no harmful consequences for the balanced development of the fish population, Member States may fix values higher than 1 mg/l (EU Freshwater Fish Directive, 2006/44/EC).

19 Ecotoxicology 15 Table 5.3 Guidelines for Ammonium, Ammonia for salmonid rivers Date Author / reference Total ammonia mg/l Ammonia unionised mg/l Irish Technical Committee on effluent and water quality. Memorandum 1. Water Quality Guidelines Waters capable of supporting freshwater fish EC (Quality of Salmonid Waters) Regulations Surface Water (fishlife) (classification) EU Directive (quality freshwaters for support of fish life) WQO Tables 5.2, 5.5 EC 78/659 Annex SI N.Ireland rule /44/EC Dissolved Oxygen Salmonid species are highly sensitive to dissolved oxygen concentrations and low dissolved oxygen levels are present in the Drish upstream of the mine discharge. The EC regulations on the quality of salmonid waters (Table 5.3) state that dissolved oxygen concentrations must exceed 9 mg/l for 50% of the time and should never drop below 6 mg/l. In general dissolved oxygen levels above 9 mg/l are considered to be necessary to support all lifecycle stages for salmonids with a 95 percentile of 5 mg/l. For coarse fish the median dissolved oxygen level for all lifecycle stages is considered to be 5 mg/l with 2 mg/l as the 95 percentile. 5.2 Fish trials The Lisheen Mine has undertaken fish trials to evaluate the potential chronic or acute toxicity of the mine water discharge every year since A population of rainbow trout were maintained in a tank supplied with the final minewater discharge to the Drish and a separate tank, which was supplied with water from upstream of the discharge point. The health of these fish were monitored during each trial, which lasted in the region of 6 months. In the tanks supplied with mine water, deaths occurred following 5 of 22 placements, with two of these resulting from power failures. No clear cause of death was identified on the other three occasions.

20 Ecotoxicology 16 By contrast the mortality of the majority of fish held in the tank supplied with water from upstream of the discharge occurred on 19 of the 23 separate occasions that fish were deployed: On six of the occasions low dissolved oxygen levels were identified as responsible for the mortalities. On three occasions system failures were responsible for fish deaths. On the remaining occasions no clear cause of death was identified. The results of the fish trials suggest that upstream water quality on the Drish is not capable of supporting fish populations throughout the year. The mine water discharge appears to provide a better environment for the fish as is evident from the significantly lower rate of mortality observed during the fish trials. The fish trials indicate that the upper reaches of the Drish under natural conditions would not be able to support salmonid species due to the depleted dissolved oxygen concentrations. Dissolved oxygen is generally restored to an acceptable concentration range to support salmonid lifecycles downstream. 5.3 Ecological impacts of elevated ammonia concentrations in the discharge One approach to determine the potential for chemicals introduced to the aquatic environment to cause adverse effects upon aquatic organisms is to compare the estimate of exposure to a chemical with a calculated threshold concentration for its adverse effects. The adverse effect concentration threshold is usually based on data for the most sensitive species tested with an additional safety factor applied to the estimated threshold value. This approach is a conservative one and does not necessarily take account of varying exposure concentrations and the ability of species to tolerate or avoid brief exposures to transitory higher concentrations of a chemical. An alternative approach to risk assessment of a chemical discharge or input to surface waters that provides a more realistic assessment of risk of adverse effects, considers the likelihood of particular exposure levels occurring together with the likelihood of effects that might occur as a result. This approach is termed probabilistic risk assessment and is commonly used in chemical risk assessments (Solomon et al., 2000). The probability plots presented in section 4.3 have been combined with an effect concentration distribution curve for unionised ammonia toxicity to a range of aquatic species (based on 1 day exposure durations) to produce a joint probability plot (species data used are not necessarily those present at this site but provide an indication of the sensitivity range of different groups of organisms), this is illustrated for a discharge of 1.5mg/l on the Drish (Figure 5.1). The dataset used for the toxicity curve is derived from the USEPA AQUIRE database with selection of good quality datasets (Table 5.4). Where the type of organism (or similar organisms in the case of the rainbow trout) tested is potentially present in the Drish or Rossestown the species name is included in the third column. Five fish species are included in the dataset, four of these are coarse fish and one - a rainbow trout - is a salmonid. The remainder of the dataset is made up of data from invertebrate studies. The most sensitive species in the dataset was the rainbow trout a salmonid commonly used in toxicity studies.

21 Ecotoxicology 17 The joint probability plots can be used to describe the nature of risks posed by the environmental concentrations measured. These plots indicate that less than 1% to 1% of species would be affected by the concentration of unionised ammonia resulting from discharges of 1.5 and 2 mg/l respectively and that these concentrations would occur for 1% of the time. The toxicity dataset used to derive these plots is based on laboratory data in which species are continuously exposed to unionised ammonia for up to a day, since the concentrations of unionised ammonia are less likely to remain above effects thresholds for this amount of time and the fact that many species can move from areas of higher concentration further reduces the likelihood of adverse effects. Table 5.4 Toxicity data (1 day LC50 s 1 ) used for the effect probability plots for the mine water discharge (data derived from US EPA Aquire database) Types of organism Tested Unionised ammonia concentration mg/l Species of greater relevance to discharge location Fish 0.1 Rainbow trout Molluscs 0.2 Molluscs 0.4 Fish 0.5 Carp Fish 0.5 Silver carp Fish 0.6 Fish 0.7 common carp Fish 0.7 common carp Fish 0.9 common carp Fish 1.0 common carp Fish 1.2 Crustaceans 1.5 Water flea Molluscs 1.6 Great pond snail Crustaceans 1.6 Water flea Worms 1.6 Crustaceans 1.7 Water flea Molluscs 1.8 Bladder snail Insects 1.9 Mayfly Crustaceans 2.0 Water flea Crustaceans 2.1 Water flea Worms 2.3 Tubificid worm, Oligochaete Insects 2.5 Midge Crustaceans 2.6 shrimp Insects 2.7 Damselfly Crustaceans 2.9 Water flea Fish 2.9 Invertebrates 3.2 Rotifer Crustaceans 3.3 Aquatic sowbug Fish 3.9 Invertebrates 4.6 Rotifer Fish LC50: Concentration that kills 50% of a sample population.

22 Ecotoxicology 18 Table 5.4 Toxicity data (1 day LC50 s 2 ) used for the effect probability plots for the mine water discharge (data derived from US EPA Aquire database) (continued) Types of organism Tested Unionised ammonia concentration mg/l Species of greater relevance to discharge location Crustaceans 6.3 shrimp Crustaceans 8.2 Water flea Crustaceans 8.2 Water flea Crustaceans 10.0 Crustaceans 13.2 Crustaceans 13.9 Aquatic sowbug Crustaceans 14.5 Aquatic sowbug Crustaceans 14.6 Molluscs 18.0 Molluscs 18.0 Crustaceans 22.9 Crustaceans 24.2 Crustaceans 27.0 Crustaceans 28.4 Crustaceans 32.5 Crustaceans 33.2 Crustaceans 35.6 Crustaceans 44.0 Crustaceans 50.3 Crustaceans 52.2 Crustaceans 59.5 Crustaceans 60.8 Crustaceans 66.7 Crustaceans 74.9 Fish 79.0 Crustaceans 93.6 Fish 94.0 Molluscs Crustaceans Fish Fish Molluscs Invertebrates Rotifer Crustaceans Invertebrates Rotifer Crustaceans To take account of the potential effects of more prolonged exposures to the low levels of ammonia that may occur in the Dish and Rossestown rivers toxicity data for unionised ammonia from the literature as well as that derived from the USEPA Aquire toxicity database has been reviewed. There is generally insufficient good quality and unambiguous chronic toxicity data to enable the probabilistic assessment described above to be applied, therefore chronic toxicity data are directly compared with measured concentrations for unionised ammonia on the Drish and Rossestown rivers. 2 LC50: Concentration that kills 50% of a sample population.

23 Ecotoxicology 19 The data indicate chronic toxicities (30 60-day LOEC 3 and 72-day LC50) of 0.05 mg/l unionised ammonia. On the basis of acute and chronic toxicity data, water quality criteria, ranging between mg/l for short-term exposures and mg/l for long-term exposures, have been estimated and recommended to protect sensitive aquatic animals (US Environmental Protection Agency, 1986, 1999; Environment Canada, 2001; Freshwater Fish Directive, 2006/44/EC). Based on the 1.5 mg/l discharge the mg/l unionised ammonia standard for freshwater fish (established in the freshwater fish directive to be adopted within the Water framework directive) would be exceeded on some occasions on the Drish but is not likely to be on the Rossestown discharge. However the Directive acknowledges that values for unionised ammonia may be exceeded as peaks in the daytime (EU Freshwater Fish Directive, 2006/44/EC) 5.4 Assessment of factors influencing fish life A number of factors are required to support fish life and these are summarised in Table 5.4 below together with an indication of whether these are likely to have significant influence in the Drish or Rossestown rivers. Factor Table 5.5 Factors influencing fish species composition Potential influence of factor in the Drish or Rossestown river Substrate composition Early survey data (Lisheen baseline report, 1992 spawning survey) indicate that substrate is suitable for trout/salmon spawning from faunal survey 2005/06 some evidence of increased siltation downstream of the mine discharge which might reduce quality of spawning sites Access (migration) Early survey data indicates populations of trout and salmon present Physical refuge Early survey data indicates that the aquatic plant community is reasonably diverse Spawning habitat As for substrate composition 2 Predators/Prey Healthy specimens of both trout 1 and pike noted in early surveys Level of potential effect (1-negligible; 5-extensive) 2 Evidence from faunal survey indicates siltation might extend to 300m downstream but not evident at 1.5km 1 1 Some reduction in plant species and dominance of pollution tolerant species downstream of the discharge 3 LOEC: Lowest Observed Effect Concentration

24 Ecotoxicology 20 Table 5.5 Factors influencing fish species composition (continued) Factor Pollution level Food (availability, quality) Dissolved oxygen Flow Regimes Potential influence of factor in the Drish or Rossestown river The concentration of unionised ammonia in the mine discharge has some potential to affect the quality of the trout Decrease in mayfly and stonefly species Dissolved oxygen concentrations downstream of the mine discharge are consistently higher than upstream concentrations and in a range that is consistent with habitat requirements for salmonids Downstream of the mine discharge the supplemented river flow rate maintains dissolved oxygen concentrations in a range that is consistent with habitat requirements for salmonids Level of potential effect (1-negligible; 5-extensive) 2 A discharge of 2.0 mg/l total ammonia on the Drish may reduce quality of habitat for salmonids but at a constant discharge at 1.5 mg total ammonia there is a very low likelihood of negative effects on salmonids on the Drish or Rossestown (the latter is also the case for a 2.0 mg/l discharge for Rossestown) 2 Macroinvertebrate species diversity and common diet choices for salmonids decreases downstream of the mine water discharge 1 (upstream this would be 4-5) 1 (upstream this would be 4-5) Increased flow rates resulting from mine discharge to the Drish and Rossestown rivers enhance conditions for salmonid spawning and development. Studies have shown that the highest trout densities are found in rivers with high water velocities and that are perennial with little or no flow variation throughout the year (Molony, 2001). Both rivers are subject to diffuse inputs along their length that promote eutrophic conditions and although the mine water discharge contributes to the nutrient status of the water, this is compensated for by the enhanced oxygenation of the river post discharge. Without the mine discharge the low dissolved oxygen concentrations observed upstream on the Drish would be likely to affect a far greater stretch of the river and preclude the rivers ability to support a salmonid population during times of low flow.

25 21 6 SUMMARY, CONCLUSIONS & IMPACT ASSESSMENT 6.1 Impact assessment The receptors and a summary impact assessment are presented in Table 6.1. Table 6.1 Summary impact assessment for increased ammonia discharge limit of 1.5 mg/l Receptor Impact assessment There are no potable water supplies on any of the rivers Potable water supplies downstream of the discharges so further consideration of this receptor is not warranted. The WHO state that LC50 s for animals are typically n the range of 350 to 750 mg/kg of body weight. The same paper concluded that Ammonia is not of direct importance for health in the concentrations to be expected in drinking-water. A health-based Livestock water supplies guideline has therefore not been derived. It is therefore clear that ammonium concentrations in the 1 to 2 mg/l range will have no impact on livestock. WMC have not been able to locate any specific livestock drinking water standards for ammonia. Ammonia toxicity is extremely complex and is influenced by a wide range of variables. A review of water quality data, Aquatic Life ecotoxicity literature, and on-site fish trials has shown that the risk posed to aquatic life by a discharge limit of 2 mg/l is low. Ammonia in irrigation water will have no detrimental impact on Irrigation water supplies crops and ammonia compounds are frequently applied as fertilizers. The FAO (1985) state that the normal range for ammonia in irrigation water is 0 5 mg/l. 6.2 Summary & Conclusions Naturally elevated ammonia concentrations in groundwater at the Lisheen mine are resulting in concentrations at discharge that are currently around 50% high than the IPCL limit of 1 mg/l. Concentrations in early 2007 had been around double the IPCL limit. The Lisheen Mine have taken all practicable steps to reduce ammonia concentrations in the discharge and to date this has shown that any further treatment would be impractical and cost prohibitive. Trials into passive nitrification and chemical treatment in the mine water treatment plants are on-going.