Oweninny Wind Farm. Oweninny Power Ltd. Environmental Impact Statement. Chapter 18. Hydrogeology of Iron Flush Areas

Transcription

1 Oweninny Power Ltd. Chapter 18 Hydrogeology of Iron Flush Areas Copyright ESB International Limited, all rights reserved.

2 Table of Contents 18. IRON FLUSH HYDROLOGICAL AND HYDROGEOLOGICAL ASSESSMENT INTRODUCTION APPROACH AND METHODOLOGY NPWS and An Taisce consultation process Sources of information DESK STUDY REVIEW Rainfall & evaporation Regional and Local Hydrology Geology Hydrogeology Review of previous investigation findings IRON FLUSH HYDROGEOLOGICAL INVESTIGATION Field Investigations Vegetation survey Drainage Window Sampling, Peat Augering and Water Level Monitoring Groundwater & peat water level monitoring installations Water Levels Hydrochemistry RECEIVING ENVIRONMENT BELLACORICK IRON FLUSH Introduction Geology Hydrology Hydro-geology Hydrochemistry Surface Water Input (i.e. rainfall) Shallow Ground Water (peat iron accumulation theory) Discrete Deep Groundwater upwells (iron rich bedrock groundwater) Flush Surface Water Catchment & Groundwater Recharge Area Summary Hydro-geological Conceptual Model IMPACT OF THE DEVELOPMENT - BELLACORICK IRON FLUSH Introduction Components of development which could impact on the iron flush Description of Borrow Pit Area Disruption of Groundwater Flow Paths Towards the Iron Flush Reduction in Groundwater Recharge to the Iron Flush Impact on Groundwater Levels in the Vicinity of the Iron Flush Potential Release of Hydrocarbons & other Chemicals Iron Flush- Hydrology and Hydrogeology ii

3 Alteration of Surface Water Drainage in the Vicinity of the Iron Flush Potential Hydrochemical Effects on the Flush due to Introducing Concrete Piles MITIGATION MEASURES BELLACORICK IRON FLUSH Disruption of Groundwater Flow Paths Towards the Iron Flush Reduction in Groundwater Recharge to the Iron Flush Impact on Groundwater Levels in the Vicinity of the Iron Flush Potential Release of Hydrocarbons & other Chemicals Alteration of Surface Water Drainage in the Vicinity of the Iron Flush Potential Hydrochemical Effects on the Flush due to the Introducing Concrete Piles CONCLUSIONS ON BELLACORICK IRON FLUSH WIDER HYDROLOGICAL STUDY Introduction Schedule and methodology WIDER AREA HYDROLOGY & HYDROGEOLOGY Locations assessed WIDER AREA IMPACT ASSESSMENT CONCLUSION ON WIDER AREA List of Tables Table 18-1: Summary of Subsoil Water Level Monitoring Data ( ) Table 18-2: Results of Rising Head Tests (EDA, 2003) Table 18-3: Summary of Site Investigation Methods Table 18-4: Total Flush Discharge Measurements from D Table 18-5: Site investigation and related water monitoring locations Table 18-6: Summary of Piezometer Network Table 18-7: Summary of Permeability Analysis Table 18-8: Water Level Data for Phreatic Piezometers Table 18-9: Water Level Data for Deep Peat/Subsoil Interface Piezometers Table 18-10: Water Level Data for Mineral Subsoil Piezometers Table 18-11: Water Level Data for Perimeter Boreholes Table 18-12: Surface Water Field Hydrochemistry Table 18-13: Phreatic Surface Field Hydrochemistry Table 18-14: Deep Peat Field Hydrochemistry Table 18-15: Mineral Subsoil Field Hydrochemistry Table 18-16: Hydrochemical Results for Round 1 of Sampling Table 18-17: Hydrochemical Results for Round 2 of Sampling Iron Flush- Hydrology and Hydrogeology iii

4 Table 18-18: Hydrochemical Results for Round 3 of Sampling Table 18-19: Hydrochemical Results for Round 4 of Sampling (Part 1) Table 18-20: Hydrochemical Results for Round 4 of Sampling (Part 2) Table 18-21: Summary of Water Type Analysis Table 18-22: Development Setback Distances from csac Boundary Table 18-23: Results of Wider Study Hydrochemical Analysis List of Plates Plate 18-1: Bellacorick Iron Flush Mineral Subsoil Water Level Monitoring ( ) Plate 18-2: Coupled Piezometers within csac Plate 18-3: Continuous Water Level Plot Plate 18-4: Exposed Subsoils to the East of the Flush Plate 18-5: Mineral subsoils beneath flush area Plate 18-6: Flush Discharge on the Northern Boundary of csac (D4) Plate 18-7: Sources of Iron to the Flush Plate 18-8: Schematic of Iron Mass Balance for the Flush Plate 18-9: Iron Oxide on the Surface of Flush Plate 18-10: Spring/seepage area on the southeast of wind farm site Plate 18-11: Poor flush area on the east of wind farm site List of Figures Figure 18-1: Bellacorick Iron Flush Site Location Map Figure 18-2: regional Hydrology Map Figure 18-3: Local Soils Map Figure 18-4: Local Subsoils Map Figure 18-5: Bellacorick Iron Flush csac Drainage and Vegetation Map Figure 18-6: Bellacorick Iron Flush csac Local Drainage Map Figure 18-7: Peat Depth Map Figure 18-8: Bellacorick Iron Flush csac Site Investigation Network Figure 18-9: Bellacorick Iron Flush csac Hydrochemistry Map Figure 18-10: Durov Hydrochemistry Plot Figure 18-11: Hydrogeological Cross Section A Figure 18-12: Hydrogeological Cross Section B Figure 18-13: Bellacorick Iron Flush csac Groundwater Contour Plot Figure 18-14: Bellacorick Iron Flush csac Regional Groundwater Catchment Iron Flush- Hydrology and Hydrogeology iv

5 Figure 18-15: Bellacorick Iron Flush Recharge Area Figure 18-16: Wider Hydrological Study Figure 18-17: Wider Hydrological Study Flush Location Map Figure 18-18: Wider Hydrological Study Formoyle Flush Catchment Iron Flush- Hydrology and Hydrogeology v

6 18. IRON FLUSH HYDROLOGICAL AND HYDROGEOLOGICAL ASSESSMENT INTRODUCTION The Bellacorick Iron Flush candidate Special Area of Conservation (SAC) is situated within the Oweninny site boundary. The flush area is owned by An Taisce with an additional buffer area around the flush owned by the Department of Arts, Heritage and the Gaeltacht (National Parks and Wildlife Service). This flush area supports a unique flora ecology with the rare and protected species Marsh Saxifrage located there. The iron flush area ecology is dependent on the rate of groundwater flow through it and also its hydrochemistry. To the east of the Oweninny site, but outside its boundary, there is a second protected area, the Formoyle Flush. This also supports rare plant species dependent on groundwater flow and hydro-chemistry. A specific assessment of the potential for impact arising from the proposed development on these flush areas was requested by National Parks and Wildlife Service and An Taisce. NPWS also requested the assessment of impact on other smaller flush features within the site and also of a petrifying spring identified during ecological surveys. The Bellacorick Iron Flush SAC site has a total area of approximately 17.3ha. It is surrounded by an expanse of cutover bog. Within the csac and especially on the lower lying western side of the site the blanket bog remains relatively intact. It should be noted that the csac boundary does not delineate the extent of the flush. The flush area itself, which has an approximate area of 2.3ha, only accounts for 13.3% of the csac. A site location map is shown as Figure The csac site is characterised by an isolated east west orientated knoll on the east of the site. The western, lower lying side of the site, where the iron flush exists, slopes to the west / northwest in the direction of the Sruffaunnamuingabatia Stream which runs near the western boundary of the csac. The iron flush can be best described as an area of intact blanket bog that receives mineral-rich groundwater in what is otherwise an ombrotrophic (peat water) setting. The flush area is more akin to a fen system where the predominant source of water is mineralrich groundwater. The flush gets its name ( Iron Flush ) from the precipitates of iron (oxide) and other metals that leave an ochre colour in the discharge from the flush. The iron flush has been designated as a candidate Special Area of Conservation under the EU Habitats Directive. The site has been designated due to the presence of Marsh Saxifrage, a species listed in Annex II of the EU Habitats Directive. The Conservation Objectives are as follows (NPWS, 2009): To maintain the Annex II species for which the csac has been selected at favourable conservation status; Marsh Saxifrage; To maintain the extent, species richness and biodiversity of the entire site; and, To establish effective liaison and co-operation with landowners, legal users and relevant authorities. Iron Flush- Hydrology and Hydrogeology 18.1

7 18. 2 APPROACH AND METHODOLOGY A hydrological and hydrogeological characterisation of the Bellacorick Iron flush has been developed based on the acquired data from a desk study, review of previous investigations, and the site investigation and monitoring undertaken by Hydro- Environmental Services Ltd. A hydro-geological conceptual model was developed for the iron flush and the mechanisms that drive its hydrology are summarised. In order to assess the potential impacts of the proposed wind farm development the flush system s hydrology and hydrogeology was characterised and the groundwater recharge area supplying the flush with mineral groundwater delineated accurately and conservatively. Altering the groundwater recharge area would invariably reduce groundwater discharge at its outlet point; in this case the flush - implying a reduction in catchment area would also reduce the vertical hydraulic gradient maintaining the system. All site investigation works at the Bellacorick Iron Flush and Formoyle Iron Flush were guided by the project ecologist NPWS and An Taisce consultation process The iron flush site lies within the ownership boundaries of both An Taisce and the National Parks and Wildlife Services (NPWS). Hydro-Environmental Services (HES) along with ESBI and representatives of Oweninny Power Ltd attended consultation meetings at the offices of An Taisce and NPWS in order to provide an overview of the Oweninny wind farm development and give details of the proposed iron flush investigation methodology. Dates of the key milestones are as follows: Consultation meeting with NPWS on 22nd April 2012; Consultation meeting with An Taisce on 30th April 2012; Submittal of a Natura Impact Statement (Screening Report) along with a detailed Method Statement for proposed hydrogeological site investigation works to NPWS on 17th July 2012 see Appendix 14A. Receipt of permit from the Minister of the Arts Heritage and the Gaeltacht for consent for works within an csac on 3rd August 2012, Appendix 14B and, Receipt of license (No. FL 01/2012) from Minister of the Arts Heritage and the Gaeltacht to carryout work within a site containing a protected species, see Appendix 14C. Issue of a draft report to NPWS on 10th December 2012 with subsequent consultation; Additional monitoring and reporting Sources of information A desk study of the iron flush and its surrounding area was completed in advance of undertaking surveying and investigation work. This involved collecting all relevant geological, hydrological and hydro-geological data for the area. This included a review and consultation with the following sources: Environmental Protection Agency - Map Viewer ( Iron Flush- Hydrology and Hydrogeology 18.2

8 Geological Survey of Ireland - National Draft Bedrock Aquifer Map; Geological Survey of Ireland - Groundwater Database ( National Parks & Wildlife Services - Public Map Viewer ( Bedrock Geology 1:100,000 Scale Map Series, Sheet 6 (Geology of North Mayo). Geological Survey of Ireland (GSI, 2004); APEX Geoservices Ltd (2003) Draft Report on the Geophysical Survey for the Oweninny Windfarm at Bellacorick, Co. Mayo; Irish Drilling Ltd Bellacorick Wind Farm, Bellacorick, Co. Mayo Geotechnical Report (April 1992); Eugene Daly Associates Interim Report on the Hydrogeology of Bellacorick Iron Flush (May 2003); C. S. Muldoon (2011) Conservation Biology of Saxifraga Hirculus in Ireland (PhD Thesis); National Parks & Wildlife Service Conservation Statement Bellacorick Iron Flush csac (2009); and, Bellacorick Iron Flush Site Synopsis (NPWS, 2000) DESK STUDY REVIEW Rainfall & evaporation Long term rainfall and evaporation data was sourced from Met Éireann. The long-term (30-year) annual average rainfall (AAR) recorded at Bellacorick (Lachtanvack) is 1,424 mm. The closest synoptic station where the average potential evapotranspiration (PE) is recorded is at Belmullet, Co. Mayo approximately 32km west of the site. The long term average PE for this station is 518mm/yr. To determine Actual Evaporation (AE) a standard crop factor of 1.3 has been regularly applied to blanket bog settings in Ireland where the surface of the bog is dominated by sphagnum. However, at the Bellacorick site there is little or no sphagnum and a value of 1.3 would overestimate AE here. A conservative estimate of 1.1 is used for the Bellacorick site which equates to an AE of 570mm/year. A factor of 0.95 is generally used for grassland sites. The effective rainfall (ER) represents the water available for runoff or groundwater recharge. The ER for the site is calculated as follows: Effective rainfall (ER) = AAR AE = 1,424mm/yr 570mm/yr ER = 854mm/yr While these stated figures represent long term average for rainfall and evaporation, they are presented here in a general context for baseline characterisation of the climate in the Iron Flush- Hydrology and Hydrogeology 18.3

9 area of the site. Where water balance calculations are completed below, these average data are not used Regional and Local Hydrology The site is located in the catchment of the Oweninny River which is a sub-catchment of the Owenmore River within Hydrometric Area 33 (Western River Basin District). The Oweninny River flows in a southerly direction approximately 1.2km to the west of the Bellacorick Iron Flush site. Surface water from the csac and the surrounding cutover blanket bog drains to the Oweninny River via the Sruffaunnamuingabatia Stream which runs near the western boundary of the csac. A regional hydrology map is shown as Figure Geology The GSI soils map ( shows that blanket peat is the predominant soil type in the vicinity of the site. An area of poorly drained soils is mapped on the elevated ground immediately to the east of the iron flush. A soils map is shown as Figure The area mapped as poorly draining soil actually comprises of thin and cutaway peat with local exposures of mineral subsoil (till). The GSI subsoils map ( for the area also shows that blanket peat is the predominant subsoil type in the vicinity of the site. Sandstone tills are mapped to underlie the cutaway peat on the east of the site. A subsoils map is shown as Figure As mentioned above the subsoils are only exposed locally where the peat is absent. Based on the GSI bedrock map of the area the site is underlain by bedded sandstone and siltstone which are referred to collectively as the Downpatrick Formation. During a site investigation undertaken by Eugene Daly Associates (EDA) in peat depths of between 1 and 3m were reported in the cutover peat surrounding the iron flush. Peat depths within the flush itself were reported to be between 5 and 6m in the centre of the flush and between 2 to 3m at the northern and southern boundaries. The results of a geophysical survey undertaken as part of the investigation (APEX Geoservices Ltd, ) indicate that 20 to 30m of mineral subsoils underlie the peat in the area of the iron flush. The interpretation indicates that loose/medium gravels overlie dense / very dense silty gravels. As part of the EDA investigation, monitoring wells (BH1, BH3, BH4, BH5 & BH6 3 ) were drilled in 2003 on the boundaries of the csac. BH2A was drilled 600m to the south of the csac. Mineral subsoils comprising coarse till (30% fines) with lenses of dirty sands and gravels (10% to 20% fines) were encountered. Bedrock was not met. No iron pan was encountered during the drilling of the monitoring wells which is noteworthy. The locations of the monitoring wells, which are referred to as perimeter wells in this report, are shown on Figure Hydrogeology The Downpatrick Formation which underlies the site and surrounding area is classified by 1 Eugene Daly Associates Interim Report on the Hydrogeology of Bellacorick Iron Flush (May APEX Geoservices Ltd (2003) Draft Report on the Geophysical Survey for the Oweninny Windfarm at Bellacorick, Co. Mayo 3 Use of BH6 has been discontinued Iron Flush- Hydrology and Hydrogeology 18.4

10 the GSI as a Poor Bedrock Aquifer (Bedrock which is generally unproductive except for local zones). The hydrogeological regime of the bedrock aquifer was not assessed as part of any of the investigations mentioned above. The water level within the underlying mineral subsoils was reported (EDA, 2003) to be between 0.1 and 2.9 metres below ground level (mbgl) (i.e. BH1, BH2A, BH4 & BH5). In the area of the elevated ground to the east of the iron flush the groundwater level in the mineral subsoils was reported to be up to 6mbgl, (i.e. BH3). Long-term groundwater level monitoring data (October 2003 to November 2011, see Plate 18-1) for monitoring wells BH1 BH5 shows a typical seasonal change in groundwater levels with the highest levels observed in February / March and the lowest in September. The monitoring well hydrographs also show a slight increasing water level trend in some of the wells (i.e. BH1, BH3 & BH5). The reason for this is likely due to drain blocking which was undertaken as part of a bog rehabilitation initiative within the proposed wind farm site. Plate 18-1: Bellacorick Iron Flush Mineral Subsoil Water Level Monitoring ( ). The maximum range in subsoil groundwater levels for each of the monitoring wells for the period October 2003 to November 2011 is shown in Table 18-2 Taking a minimum peat depth range of 1 3m as reported by EDA (2003) it would appear that groundwater within the mineral subsoil layer beneath the csac is semi-confined by the peat during all or part of the year depending on recharge rates and water level fluctuations. The exception being BH3, which is located on the elevated ground to the east of the csac and where a minimum unsaturated subsoil thickness of 3.7m was reported. Table 18-1: Summary of Subsoil Water Level Monitoring Data ( ). Iron Flush- Hydrology and Hydrogeology 18.5

11 BH WL (mod) WL (mbgl) Max Min Max Min Range BH BH2A BH BH BH Based on rising head tests undertaken by EDA in 2003 on the perimeter boreholes, see Table 18-2, the mineral subsoils in the area of the csac were found to have a moderate permeability (i.e. k value of between 10-6 to 10-7 m/s). EDA (2003) describes a perched water table within the peat of the iron flush. This can also be referred to as the phreatic water surface of the peat layer and normally ranges between 0 and 0.1mbgl for intact peat. No data on peat water levels, gradients or fluctuations are available from the EDA interim investigation. Table 18-2: Results of Rising Head Tests (EDA, 2003). BH No. Screen Range (mbgl) Main Lithology Permeability (m/s) BH Sandy silty clay with gravel 1.2 x 10-6 BH2A Coarse dirty sand & gravel 1.06 x 10-6 BH Fine till with round cobbles 3.08 x 10-7 BH Fine till & dirty sand & gravel 2.53 x 10-7 Average 7.05 x Review of previous investigation findings The historic main findings of the interim investigation undertaken by Eugene Daly & Associates (2003) are reported as follows: The iron flush is recharged by rainfall and flow off the elevated ground to the east of the flush (the present study does not support this and offers an alternative explanation) by shallow drains to the north and south and to the Sruffaunnamuingabatia Stream at the north-western corner of the site; The reported recharge mechanism is rainfall infiltrating into the mineral subsoil deposits where the overlying peat is thin or has been removed by cutting; In the area of the iron flush the groundwater level in the mineral subsoils are below those of the peat and are isolated from them. The groundwater in the mineral subsoil does not appear to discharge through the surface pools of the iron flush; The hydraulic boundaries of the iron flush system are close to the flush boundaries (An Taisce area) and mainly within the conservation area (NPWS) surrounding the flush; and, Iron Flush- Hydrology and Hydrogeology 18.6

12 The discharge areas of the flush and most of the recharge areas are within the conservation area surrounding the flush IRON FLUSH HYDROGEOLOGICAL INVESTIGATION The following schedule of works has been completed as part of the iron flush investigation: A preliminary walkover survey and drainage mapping of the area outside the csac was undertaken on 23rd May Data loggers were installed in the existing perimeter boreholes for continuous groundwater level monitoring; A vegetation survey of the iron flush was undertaken by John Conaghan (project ecologist) on 20th August 2012 prior to any intrusive investigation works taking place within the csac boundary; Drainage mapping and field hydrochemistry measurements (i.e. ph, electrical conductivity & temperature) of surface water and flush water within the csac was undertaken on 20th August 2012 by HES; Window sampling, peat augering and installation of peat and mineral soil piezometers was undertaken by HES on 10th, 11th and 12th September 2012; An elevation survey of all groundwater and surface water monitoring installations was undertaken on 26th September 2012 by means of a differential Global Positioning System (dgps); Water level monitoring was completed in all installed boreholes, piezometers, and phreatic tubes on 12th and 27th September 2012, 16th and 24th October 2012 and 5th November 2012; Field hydrochemistry measurements and sampling of surface water and boreholes/piezometers was undertaken on 27th September 2012, 16th October 2012, 5th November 2012, 7th February 2013 and 14th February 2013; and, A v-notch weir for measurement of surface water runoff and discharge from the iron flush was constructed downstream of the csac on 5th & 6th November Field Investigations A summary of the main investigation methods carried out are summarised in Table 18-3 below. Table 18-3: Summary of Site Investigation Methods. Task Drainage mapping Field hydrochemistry measurements of surface water & flush water Peat Augering Methodology Walkover survey and mapping of significant drainage features including discharge and potential recharge zones. Measurement of surface water and flush zone hydrochemistry using a hand held YSI Multimeter probe. Locations were recorded using a hand held GPS. The thickness and lithology of the peat profile was Iron Flush- Hydrology and Hydrogeology 18.7

13 Task Window sampling (WS) Piezometer network Installation Groundwater & surface water sampling Iron flush discharge monitoring Methodology determined at select locations using a hand held soil auger. Peat was logged to Von Post Humification scale. WS is an intrusive technique that uses portable equipment to recover narrow cores of peat and subsoil for visual logging and sampling. WS was used where penetration into the mineral soils underlying the peat was required. Mineral soils and peat were logged according to BS5930 and Von Post Scale respectively. Installation of piezometer tubes (narrow 18mm & 22mm PVC pipes) for peat water and groundwater level monitoring within and surrounding the iron flush. Four rounds of surface water and groundwater sampling were undertaken for laboratory hydrochemical analysis. A v notch weir was constructed downstream of the iron flush to manually gauge discharge volumes. Only spot checks on flow have taken to date Vegetation survey Before any investigation works within the csac boundary were permitted it was requested by NPWS that a vegetation survey of the csac be undertaken by an ecologist. The purpose of the survey was to provide updated information on the ecological condition of the iron flush and also to map out sensitive areas of the csac that were to be completely avoided during the surveying and investigation works. (i.e. Saxifraga Hirculus locations). The coverage and extent of intact blanket bog, cutover bog, rich and poor flush areas and the locations of Saxifraga Hirculus, Marsh Saxifrage and Tomentypums Nitens within the csac are shown on Figure 18-5:. The survey report is provided in Appendix 14D Drainage A site drainage map for the csac is shown on Figure A Local drainage map for the area surrounding the csac is shown as Figure The majority of drains within the wind farm site have been blocked as part of a bog rehabilitation initiative. Surface water drainage patterns are therefore governed by the topography of the site and the layout of the cutover peat. The Sruffaunnamuingabatia Stream is the main surface water feature in the vicinity of the csac. This stream flows in a southerly direction near the western boundary of the csac. Spot flow measurements taken in this stream between 23 rd May 2012 and 5 th November 2012 show a discharge rate of between 618 1,500m 3 /day. The Sruffaunnamuingabatia Stream is a natural feature, however it is likely that it has been modified to some extent in the past, i.e. widened and deepened. In addition to the Sruffaunnamuingabatia Stream there are a number of manmade bog drains that exist within and close to the boundaries of the csac. These are described below as follows: Drain D1, which exists in intact bog, flows in a south-westerly direction close to the southern boundary of the csac and discharges to the Sruffaunnamuingabatia Stream close to the south-western corner of the site. Drain D1 also discharges into drain D2 approximately 10m west of BH4 on the southern boundary of the Iron Flush- Hydrology and Hydrogeology 18.8

14 csac. Drain D1 is initially a shallow man-made (ditched) bog drain with a depth and width of approximately 0.8m and 0.7m respectively. However, towards the western end of the man-made drain depth increases to approximately 2.5m and the base of the drain intercepts the mineral subsoils underlying the peat. Drain D2, which is a face bank drain, flows in a south-westerly direction at the foot of the cutaway peat bank which delineates the southern boundary of the csac. Drain D2 discharges back into drain D1 towards the south-western corner of the csac, see Figure 18-5:. Drain D3, which exists in cutaway bog, runs along the north-eastern boundary of the site and receives runoff from the elevated ground to the east of the iron flush. Drain D3 discharges onto an area of cutaway bog at the north-eastern corner of the csac which then drains westward to a culvert prior to entering the Sruffaunnamuingabatia Stream. The culvert exists close to the north-western corner of the csac as shown on Figure Drain D4, which is a face bank drain, flows in westerly direction along the foot of the cutaway bog bank close to the northern boundary of the csac. Drain D4 receives surface water runoff and groundwater seepage from the area of the iron flush. Originally drain D4 discharged at 3 4 outlet points towards the western end of the drain prior to entering the Sruffaunnamuingabatia Stream via the above mentioned culvert. A v-notch weir was installed upstream of the culvert on 5 th November 2012 and now all discharge from drain D4 is diverted towards the weir to enable measurement of total discharge from the iron flush. Spot flow measurements of discharge taken to date (including hydrochemistry measurements) are shown in Table 18-4 below. The local drainage map (Figure 18-6) for the area of the csac shows that the overall surface water runoff direction in the vicinity of the site is westward towards the Sruffaunnamuingabatia Stream with the northeast corner of the csac site draining eastwards. Table 18-4: Total Flush Discharge Measurements from D4. Date Discharge (L/s) Electrical Conductivity (µs/cm) ph 26/09/ /10/ /11/ /02/ /02/ Average Drain D5, which is a face bank drain, flows in a northerly direction at the foot of the cutaway peat bank on the west of the csac. Drain D5 discharges to the Iron Flush- Hydrology and Hydrogeology 18.9

15 Sruffaunnamuingabatia Stream via the culvert on the north-western corner of the csac. A cluster of bog pools exist within the central plateau area and southern end of the site. These bog pools, which have a depth of approximately mm, discharge towards drains D1 and D5. The local drainage map (Figure 18-6) for the area of the csac shows that the general surface water runoff direction in the vicinity of the iron Flush is westward towards the Sruffaunnamuingabatia Stream. There is a small area of the elevated ridge (east of the Iron Flush) draining towards the east locally. This combines with other field drains and eventually flows to the west towards the Sruffaunnamuingabatia Stream Window Sampling, Peat Augering and Water Level Monitoring A combination of peat augering and window sampling was undertaken to determine peat depths and to investigate peat and mineral subsoil lithology within the csac. Outside of the csac boundary random peat depth probing was undertaken to determine peat depths in the surrounding cutaway peat area. A summary of the augering and window sampling locations are shown in Table 18-5 below. Detailed site investigation logs are shown in Appendix 14E. A peat depth map for the csac and the surrounding area is shown on Figure Peat depth measurements within the cutaway bog surrounding the csac ranged between 0 and 2m while peat depth measurements within the csac ranged between 0.9m and 4.1m. Iron Flush- Hydrology and Hydrogeology 18.10

16 Table 18-5: Site investigation and related water monitoring locations Location Coordinates (ITM) Easting Northing Ground Elevation (m (OD)) Peat Depth (m) Summary of Mineral Subsoil Lithology C C C Slightly sandy CLAY over coarse to fine SAND Soft SILT/CLAY over dense to firm SAND Soft SILT/CLAY over dense to firm SAND C Grey, wet, fine silty SAND C5-PH N/A C5-PH N/A C C6A Dense sandy gravel over soft sandy SILT Fine silty SAND with bed of slightly gravelly coarse SAND C N/A C Gravelly SAND C SAND C SAND C11-PH N/A C11-PH N/A C12-PH N/A C12-PH N/A Note: N/A Peat depth only Groundwater & peat water level monitoring installations Couples of nested piezometers were installed to various depths within the peat and underlying mineral subsoil (Plate 18-2). Subsoil or subsoil/deep peat interface piezometers are numbered P1, with P2 series numbering indicating a shallower piezometer within the peat profile. The PH1 series are the shallow phreatic tubes to allow near surface monitoring of the free water table on the bog vegetated surface. A summary of the piezometer network installed by HES is shown in Table 18-6 below. The locations Iron Flush- Hydrology and Hydrogeology 18.1

17 of the installations are shown on Figure Plate 18-2: Coupled Piezometers within csac Table 18-6: Summary of Piezometer Network Location Phreatic Tube Mineral Soil Piezometer Deep peat/mineral soil interface piezometer C1 C1-PH1 C1-P1 C1-P2 C2 C2-PH1 C2-P1 C1-P2 C3 C3-PH1 C3-P1 C3-P2 C4 C4-PH1 C4-P1 C5-PH-1 C5-PH1 C5-PH-2 C5-PH2 C6 C6-PH1 C6-P1 C6-P2 C6A C6A-PH1 C6A-P1 C6A-P2 C7 C7-PH1 C8 C8-PH1 C9 C9-PH1 C9-P1 C10 C10-PH1 C10-P1 C11-PH1 C11-PH1 C11-PH2 C11-PH2 C12-PH1 C12-PH1 Iron Flush- Hydrology and Hydrogeology 18.2

18 Location Phreatic Tube Mineral Soil Piezometer Deep peat/mineral soil interface piezometer C12-PH2 C12-PH Water Levels A total of six rounds of water level monitoring have been undertaken since the completion of the piezometer network installation on 12 th September Generally water levels in the phreatic tubes and mineral subsoil piezometers are fastest to reach equilibrium conditions while water levels in the deep peat piezometers may take weeks to reach equilibrium due to the low permeability of the surrounding peat. A plot of water levels within the piezometers is shown graphically in Appendix 14F. The plots show that the phreatic and mineral soil piezometer water levels have generally reached equilibrium conditions with little variation over the monitoring period. Analysis of the water level recovery data (Hvorslev, 1951) for a number of the piezometers was undertaken using proprietary software Aqtesolve to determine the permeability of the subsoil and peat within the flush. This data is summarised in Table 18-7 below and the analysis plots are shown in Appendix 14G. The analysis shows that both the peat and underlying subsoils have low permeability. Table 18-7: Summary of Permeability Analysis. Piezometer Name Substrate Permeability (m/s) C1-P1 Subsoil 7.7 x C1-P2 Peat 5.6 x C2-P1 Subsoil 6.9 x C2-P2 Peat 1.9 x C3-P2 Peat 6.1 x C4-P1 Peat 4.9 x C6-P1 Subsoil 3.5 x C6-P2 Peat 3.7 x Water level data from monitoring rounds four, five and six are shown in Table 18-8 to Table below. Water levels from the most recent round of monitoring (14/02/2013) are discussed below. The water level plots shown in Appendix 14F show that the water levels have remained relatively stable once they achieved full recovery (after installation). Water levels in the shallow phreatic tubes within the intact bog of the csac (i.e. PH1) ranged from between 0.07 metres below ground level (mbgl) to 0.09 metres above ground level (magl). Water levels in the deep peat/subsoil interface piezometers (i.e. P2/P1) ranged from between 0.705mbgl and 0.075magl while water levels in the subsoil piezometers (i.e. P1) ranged between 0.39mbgl to 0.13magl within the csac. The water levels in the surrounding perimeter boreholes, which are located on cutover Iron Flush- Hydrology and Hydrogeology 18.3

19 peat ranged between 4.689mbgl and 0.198mabgl. A continuous water level plot for the period 23 rd May 2012 to 14 th February 2013 is shown for a number of the boreholes and piezometers on Plate Plate 18-3: Continuous Water Level Plot Table 18-8: Water Level Data for Phreatic Piezometers. Piezometer W.L. (mod) 27/09/ /11/ /02/2013 W.L. (mbgl) W.L. (mod) W.L. (mbgl) W.L. (mod) W.L. (mbgl) Intact Peat C1-PH C2-PH C3-PH C4-PH C5-PH C6-PH C6A-PH C7-PH C8-PH C9-PH C10-PH C11-PH C12-PH Max Min Iron Flush- Hydrology and Hydrogeology 18.4

20 Piezometer W.L. (mod) 27/09/ /11/ /02/2013 W.L. (mbgl) W.L. (mod) W.L. (mbgl) W.L. (mod) W.L. (mbgl) Cutover Peat C5-PH C11-PH C12-PH Max Min Note: Negative values mean metres above ground level. Table 18-9: Water Level Data for Deep Peat/Subsoil Interface Piezometers. Piezometer W.L. (mod) 27/09/ /11/ /02/2013 W.L. (mbgl) W.L. (mod) W.L. (mbgl) W.L. (mod) W.L. (mbgl) C1-P C2-P C3-P C4-P C6-P C6A-P C9-P C10-P Max Min Note: Negative values mean metres above ground level. Table 18-10: Water Level Data for Mineral Subsoil Piezometers. Piezometer W.L. (mod) 27/09/ /11/ /02/2013 W.L. (mbgl) W.L. (mod) W.L. (mbgl) W.L. (mod) W.L. (mbgl) C1-P C2-P C3-P C6-P C6A-P Max Iron Flush- Hydrology and Hydrogeology 18.5

21 Min Note: Negative values mean metres above ground level. Table 18-11: Water Level Data for Perimeter Boreholes. Borehol e W.L. (mod) 27/09/ /11/ /02/2013 W.L. (mbgl) W.L. (mod) W.L. (mbgl) W.L. (mod) W.L. (mbgl) BH BH BH BH Max Min Note: Negative values mean metres above ground level Hydrochemistry Field measurements of unstable parameters (i.e. ph and electrical conductivity) of surface waters within the csac and flush area were undertaken on 20 th August A summary of the measurements taken and their location is shown in Table below. The locations of the measurements are shown on Figure Electrical conductivity values of surface water within the csac ranged between 58 and 439µs/cm while ph values ranged between 6.0 and 7.2. The spatial distribution of surface water hydrochemistry measurements is discussed in Section below. Table 18-12: Surface Water Field Hydrochemistry. Coordinates ph Conductivity Easting Northing (ph units) µs/cm) Iron Flush- Hydrology and Hydrogeology 18.6

22 Coordinates ph Conductivity Easting Northing (ph units) µs/cm) Max Min Field measurements of unstable hydrochemistry for groundwater and peatwater from the piezometer installations and from the existing perimeter boreholes were undertaken on the 27 th September A summary of the measurements taken are shown in Table to Table below. Electrical conductivity values for the shallow peat/phreatic surface ranged between 80 and 546µS/cm while ph values ranged between 6.3 and 7.1. Electrical conductivity values for the deep peat piezometers ranged between 214 and 539µS/cm while ph values ranged between 6.2 and 7.2. Electrical conductivity values for the mineral subsoil piezometers & perimeter boreholes ranged between 514 and 797µS/cm while ph values ranged between 6.8 and 7.6. Table 18-13: Phreatic Surface Field Hydrochemistry. Piezometer No. ph Electrical Conductivity Temperature ph units µs/cm C C1-PH C2-PH C3-PH C4-PH C5-PH Iron Flush- Hydrology and Hydrogeology 18.7

23 Piezometer No. ph Electrical Conductivity Temperature ph units µs/cm C C5-PH C6-PH C6A-PH C7-PH C8-PH C9-PH C10-PH C11-PH C11-PH C12-PH C12-PH BH4-PH BH5-PH Max Min Table 18-14: Deep Peat Field Hydrochemistry. Piezometer No. ph Electrical Conductivity Temperature ph units µs/cm C C1-P C2-P C3-P C4-P C6-P C6A-P C9-P C10-P Max Min Iron Flush- Hydrology and Hydrogeology 18.8

24 Table 18-15: Mineral Subsoil Field Hydrochemistry. Piezometer No. ph Electrical Conductivity Temperature ph units µs/cm C C1-P C2-P C3-P C6-P C6A-P BH BH BH BH Max Min Four rounds of surface water and groundwater samples were taken for hydrochemical analysis 1 on 27 th September, 16 th October, 5 th November 2012 and 7 th February Groundwater samples were taken from the existing perimeter boreholes and from a number of the P1 (subsoil) range piezometers within the csac. Phreatic peat water samples were taken from a number of the PH1 range piezometers within the csac. A sample of the discharge from the iron flush was also taken at the weir downstream of the csac. This sample is a combination of groundwater seepage and surface water from the flush. For comparison of hydrochemistry a sample was also taken from a bog pool at SG1 within the csac and from the Sruffaunnamuingabatia Stream (SW1) downstream of the csac. The results of analysis are shown in Table to Table below. Table 18-16: Hydrochemical Results for Round 1 of Sampling. Parameter Units BH1 BH3 BH4 C2-P1 SG1 SW1 ph ph Units Analysis was undertaken by City Analysts Ltd, Dublin ( ) and CLS laboratories, Connemara, Co. Galway ( ) Iron Flush- Hydrology and Hydrogeology 18.9

25 Parameter Units BH1 BH3 BH4 C2-P1 SG1 SW1 Electrical Conductivity µs/cm Total Hardness mg/l < Total Alkalinity mg/l <10 25 Bicarbonate mg/l < Sodium mg/l Potassium mg/l Chloride mg/l Sulphate mg/l < <5 <5 <5 <5 Nitrate (NO3) mg/l <0.44 <0.44 <0.44 <0.44 <0.44 <0.44 Nitrite (NO2) mg/l <0.017 <0.017 < <0.017 <0.017 Ammonia N mg/l Calcium mg/l <3 9 Magnesium mg/l <0.8 2 Aluminium µg/l 3 6 < Iron (Dissolved) Manganese (Dissolved) Ortho Phosphate (P04) Total Phosphorus (P) Total Dissolved Solids µg/l µg/l <5 50 <5 <5 <5 <5 mg/l <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 mg/l <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 mg/l Table 18-17: Hydrochemical Results for Round 2 of Sampling. Parameter Units BH1 BH3 BH4 C6A-P1 SG1 SW1 ph ph Units Electrical Conductivity µs/cm Total Hardness mg/l <33 41 Alkalinity mg/l <30 <30 Iron Flush- Hydrology and Hydrogeology 18.10

26 Parameter Units BH1 BH3 BH4 C6A-P1 SG1 SW1 (CaCO3) Bicarbonate mg/l <37 <37 Sodium mg/l Potassium mg/l <0.4 <0.4 Chloride mg/l Sulphate mg/l < <20 <20 <20 <20 Nitrate (NO3) mg/l <8.8 <8.8 <8.8 <8.8 <8.8 <8.8 Nitrite (N) mg/l 0.02 <0.005 < < Ammonia N mg/l Calcium mg/l < Magnesium mg/l <5 <5 Aluminium µg/l 399 <20 <20 < Iron (Dissolved) µg/l 606 <20 <20 < Iron (Total) µg/l Manganese (Dissolved) Manganese (Total) Ortho Phosphate (P) Total Phosphorus (P) Total Dissolved Solids µg/l <5 <5 µg/l mg/l <0.025 <0.025 <0.025 <0.025 mg/l mg/l Table 18-18: Hydrochemical Results for Round 3 of Sampling. Parameter Units C2-PH1 C3-PH1 C6A-PH1 Discharge ph ph Units Electrical Conductivity µs/cm Total Hardness mg/l Alkalinity (CaCO3) mg/l Bicarbonate mg/l Iron Flush- Hydrology and Hydrogeology 18.11

27 Parameter Units C2-PH1 C3-PH1 C6A-PH1 Discharge Sodium mg/l Potassium mg/l Chloride mg/l Sulphate mg/l < <5 <5 Nitrate (NO3) mg/l <0.44 <0.44 <0.44 <0.44 Nitrite (NO2) mg/l <0.017 <0.017 <0.017 <0.017 Ammonia N mg/l <0.005 <0.005 <0.005 <0.005 Calcium mg/l Magnesium mg/l Aluminium µg/l Iron (Dissolved) mg/l Iron (Total) mg/l Manganese (Dissolved) Manganese (Total) Ortho Phosphate (P) Total Phosphorus (P) Total Dissolved Solids mg/l mg/l mg/l < <0.01 <0.01 mg/l mg/l Table 18-19: Hydrochemical Results for Round 4 of Sampling (Part 1). Parameter Units BH1 BH3 BH4 SG1 SW1 Discharge ph ph Units Electrical Conductivity µs/cm Total Hardness mg/l < <33 Total Alkalinity mg/l <30 < Sodium mg/l Potassium mg/l Chloride mg/l Iron Flush- Hydrology and Hydrogeology 18.12

28 Parameter Units BH1 BH3 BH4 SG1 SW1 Discharge Sulphate mg/l 92.1 <20 <20 <20 <20 <20 Nitrate (NO3) mg/l <8.8 <8.8 <8.8 <8.8 <8.8 <8.8 Nitrite (NO2) mg/l <0.005 < <0.005 Ammonia N mg/l 0.04 < < <0.01 Calcium mg/l Magnesium mg/l Aluminium (Total) Iron (Dissolved) mg/l µg/l <20 <20 < Iron (Total) mg/l Ferric iron (III) mg/l <0.05 <0.05 <0.05 < Ferrous iron (II) mg/l <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Manganese (Dissolved) Manganese (Total) Ortho Phosphate (P) Total Phosphorus (P) Total Suspended solids Total Dissolved Solids µg/l < mg/l mg/l 0.05 <0.025 <0.025 <0.025 <0.025 <0.025 mg/l <0.05 <0.05 <0.05 mg/l <2 mg/l Table 18-20: Hydrochemical Results for Round 4 of Sampling (Part 2). Parameter Units C2-P1 C2-PH1 ph ph Units Electrical Conductivity µs/cm Total Hardness mg/l Total Alkalinity mg/l Sodium mg/l Iron Flush- Hydrology and Hydrogeology 18.13

29 Parameter Units C2-P1 C2-PH1 Potassium mg/l Chloride mg/l Sulphate mg/l <20 <20 Nitrate (NO3) mg/l <8.8 <8.8 Nitrite (NO2) mg/l <0.005 <0.005 Ammonia N mg/l Calcium mg/l Magnesium mg/l Aluminium (Total) mg/l Iron (Dissolved) µg/l Iron (Total) mg/l Ferric iron (III) mg/l <0.05 <0.05 Ferrous iron (II) mg/l <0.1 <0.1 Manganese (Dissolved) µg/l Manganese (Total) mg/l Ortho Phosphate (P) Total Phosphorus (P) Total Suspended solids Total Dissolved Solids mg/l <0.025 <0.025 mg/l mg/l mg/l Proprietary software AqQa was used to determine the hydrochemical water type of the groundwater and surface water samples. These results are shown in Table below. A Durov plot 2 of major anions and cations for each of the sample locations is shown in Figure A Durov plot of the PH1 piezometers and the flush discharge was not undertaken as these samples are a mixture of mineral subsoil groundwater from beneath the flush and rainfall landing on the flush. Table 18-21: Summary of Water Type Analysis. Sample Location Round 1 Results Round 2 Results Round 4 Results BH1 Ca-HCO 3 Ca-HCO 3 Ca-HCO 3 2 A Durov Plot is graphical presentation of the concentrations of cations and anions in a water sample Iron Flush- Hydrology and Hydrogeology 18.14

30 Sample Location Round 1 Results Round 2 Results Round 4 Results BH3 Ca-HCO 3 Ca-HCO 3 Ca-HCO 3 BH4 Ca-HCO 3 Ca-HCO 3 Ca-HCO 3 C2-P1 Ca-HCO 3 - Ca-HCO 3 C6A-P1 - Ca-Cl - SG1 (Bog Pool) Na-Cl Na-Cl Na-Cl SW1 (Stream) Ca-Cl Ca-Cl Na-Cl - Not sampled on that date RECEIVING ENVIRONMENT BELLACORICK IRON FLUSH Introduction The hydrological and hydrogeological characterisation of the iron flush presented in the following section is based on the data acquired from the desk study, review of previous investigations, and the HES site investigation and monitoring. A hydrogeological conceptual model has been developed for the iron flush and the mechanisms that drive its hydrology are summarised Geology The superficial geology in the vicinity of the iron flush comprises blanket peat overlying approximately 20 to 30m of sandstone till (mineral subsoil). The underlying parent material (i.e. bedrock) is mapped to be bedded sandstone. Measured peat depths surrounding the csac ranged between 0 and 2m (refer to Figure 18-7). Areas where peat is absent are generally located on the elevated ground to the east of the iron flush. Mineral subsoils are exposed here in places and it is likely that peat was naturally thin or has been removed by erosion after peat cutting (Plate 18-4). The maximum peat depth recorded on the elevated land to the east of the iron flush was 1.41m. In areas where peat has been mechanically removed (i.e. to the north and south of the csac) peats depths are generally less than 0.5m, and often absent, but with some local deeper zones of peat remaining with depths of up to 2m. Iron Flush- Hydrology and Hydrogeology 18.15

31 Plate 18-4: Exposed Subsoils to the East of the Flush. Blanket bog within the csac is generally intact with the exception of sections along the western and northern boundary of the site. The peat depths in cutover areas within the csac were found to be between 0.9 and 2.12m. The thickness of the intact peat within the csac was found to be between 0.91 and 4.1m. The deepest peat was found towards the central area of the csac (i.e. C9) while peat depths on the northern, southern and western verges of the intact peat were between 2.7 and 3.26m. The peat within the flush area was found to thin out to approximately 0.9m towards the elevated ground to the east of the site. Peat depths recorded in the core rich flush area itself were between 2.74 and 3.26m. The intact peat profile generally comprised of wet fibrous peat with vegetation roots over soft, brown, wet peat, with some visible vegetation fibres reducing with depth. The EDA (2003) investigation reported 2 3m of peat on the northern and southern boundaries of the csac which is in line with the HES investigation. However, EDA reported a maximum depth of 6m which is deeper than the maximum depth encountered in this investigation (4.1m). Therefore, this potentially indicates that deeper pockets of peat over 4.1m exist. Mineral subsoils comprising coarse till (30% fines) with lenses of dirty sands and gravels (10% to 20% fines) were encountered by EDA during the drilling of the perimeter boreholes in Similarly, subsoils encountered by HES underlying the peat within the csac were found to comprise predominately of fine to coarse SAND with minor constitutes of gravel and silt, (Plate 18-5). A layer of CLAY or SILT/CLAY was found to overlie the sand in some places. In addition, no iron pan was intercepted below the iron flush during the installation of the piezometers which is consistent with EDA (2003) investigation. There was no evidence of an iron pan in the surrounding drains and mineral subsoil exposures. Geological cross-sections (A & B) through the csac and iron flush are show on Figure and Figure The locations of the cross-sections are shown on Figure Iron Flush- Hydrology and Hydrogeology 18.16

32 Plate 18-5: Mineral subsoils beneath flush area Hydrology Water level monitoring in the phreatic tubes within the Bellacorick Iron Flush SAC show that the free standing water table within the intact peat (i.e. vegetated surface) was between 0.1mbgl and 0.09magl during the monitoring period. Phreatic water levels above ground level were recorded in C1-PH1, C2-PH1, C3-PH1, C9-PH1 and C10-PH1 during this period. Areas where the phreatic water level was recorded above ground level on intact peat were generally within the flush zone area with the exception of C10-PH1 and C9-PH1. The deepest phreatic water level (0.1mbgl) was recorded adjacent to the cutaway peat banks (i.e. C5-PH1) close to the boundary of the csac. The phreatic water level in piezometers located on cutover peat (i.e. C11-PH2 and C12-PH2) was generally above ground level due to surface water runoff and ponding. The water levels in the phreatic tubes indicate that the shallow lateral flow in the upper vegetated layer of the peat generally follows the topographic contours of the site. The north-western section of the csac which includes the flush area drains to the northwest of the site towards the peat face and shallow drain D4 (Plate 18-6). The discharge in drain D4 is a combination of rainfall runoff and groundwater seepage from within the flush area. The surface water catchment to the flush is delineated in Figure Spot flow measurements of discharge from D4 are shown in Table 18.5 above. Based on the measurements taken to date the average total discharge (surface & groundwater) from the flush was 1.2L/s (103.7m 3 /day). The eastern and southern sections of the csac drain south towards D1 which runs close to the southern boundary of the csac. A narrow section to the south of drain D1 drains towards drain D2. The central and western sections of the csac drain towards D5. A Iron Flush- Hydrology and Hydrogeology 18.17

33 phreatic water level contour map for water levels measured on 14 th February 2013 is shown on Figure The bog pools, which are perched within the blanket bog, drain towards D1 on the southern boundary and D5 towards the western boundary of the csac. It appears from site inspection that one of the purposes of drain D1 was to drain the bog pools. Plate 18-6: Flush Discharge on the Northern Boundary of csac (D4). Water levels in the deep peat piezometers (i.e. P2/P1) ranged from between 0.705mbgl and 0.075magl on 14 th February Areas where deep peat potentiometric water levels were recorded above ground level include C2-P2, C3-P2 C6-P2 and C9-P1. These piezometers are located within or adjacent to the flush area. The reason for the deep peat potentiometric water level existing above ground level in this area is as a result of an upward hydraulic gradient from the underlying mineral subsoils into the peat. On the 14 th February 2013 the highest vertical gradient was recorded in C3-P2 where a head of 0.076m was recorded over the phreatic water level Hydro-geology Based on rising head tests undertaken by EDA in 2003 on the perimeter boreholes, the mineral subsoils in the area of the csac were found to have a moderate permeability (i.e. k value of between 10-6 to 10-7 m/s). Analysis of recovery plots (Refer to Appendix 14G) in some of the flush piezometers indicated that the subsoils underlying the peat within the flush have a low permeability (i.e k value of m/s). The lower permeability of the subsoils directly beneath the peat of the flush can be explained by the presence of higher quantities of fine material (i.e. fine SILT & dense fine SAND) within the till. The presence of low permeability material directly underlying the peat would be expected as this is the reason the bog formed here in the Iron Flush- Hydrology and Hydrogeology 18.18

34 first place. The screens (i.e. slots in casing) of the EDA (2003) boreholes are deeper than the screens of the piezometers within the flush area and it may be the case that there is less fine material at depth within the mineral subsoils. Water level data from the perimeter boreholes show that (with the exception of BH3) the mineral subsoils are saturated beneath the base of the peat and are in some places actually confined (i.e. BH4 & BH5). BH4 is actually slightly artesian; however the upvc casing which was installed above to approximately 1m above ground level prevents over flow from the borehole. BH3 which is located on the elevated ground to the east of the iron flush had an unsaturated thickness of approximately 3.95m during the monitoring period and therefore the subsoils are not confined at this location. Hydrograph plots of continuous water level monitoring from various boreholes are shown on Plate 18-3 above. The plots show that there is limited variation in the subsoil groundwater levels over that period with the exception of BH3. There is a notable rise in the groundwater level in BH3 from November 2012 onwards compared to the other boreholes. This increase in groundwater level is likely as a result of recharge occurring on the elevated ground to the east of the iron flush over the wetter winter period. This indicates that recharge rates are higher in the area of the elevated hill compared to the surrounding cutaway bog areas and this is likely due to the mineral subsoil being exposed in this area. The more frequent water level fluctuations observed in BH5 are likely due to the fact that BH5 is located adjacent to the stream and is therefore sensitive to water level changes in the stream. BH4, which is located remote from the stream, shows very little groundwater level fluctuation. Using groundwater level data (14/02/2013) from the mineral subsoil piezometers and perimeter boreholes a subsoil groundwater contour plot was drawn up for the area of the csac as shown in Figure The contour plot shows that the groundwater gradient is generally west towards the Sruffaunnamuingabatia Stream. Horizontal groundwater gradients towards the flush and within the flush were calculated to be and 0.02 respectively. The steeper horizontal gradient within the flush is likely due to the effects of the Sruffaunnamuingabatia Stream drawing down the groundwater level to that of the water level within the stream (refer to paragraph below). Water levels in the mineral subsoil piezometers (P1) within the csac ranged between 0.39mbgl and 0.13magl on 14 th February Areas where the mineral subsoil potentiometric water level was recorded above ground level included C2-P1, C3-P1 and C6A-P1. Areas where the subsoil potentiometric water level was recorded within the peat included C1-P1 and C6-P1. These levels show that the mineral subsoils are confined by the peat in the area of the csac and this has resulted in an upward hydraulic gradient of mineral subsoil groundwater through the body of the peat. Where the vertical gradient is highest (i.e. C2, C3 and C6A) there is seepage of mineral subsoil groundwater onto the surface of the peat and hence creating the mineral rich flush area. Cross-sections through the csac and iron flush which show the phreatic water level and the mineral subsoil potentiometric water level are shown as Figure 18-11and Figure The cross-sections show that the Sruffaunnamuingabatia Stream is having a major effect on groundwater levels within the csac which is what you would expect as the stream is a major hydraulic boundary. The stream channel is inducing a downward movement of water on the western side of the csac and possibly within the flush area. This is reflected Iron Flush- Hydrology and Hydrogeology 18.19

35 in the horizontal groundwater gradients presented above. It also appears that drain D2 is having an effect on subsoil groundwater levels within the flush. Based on the measured groundwater flow direction the regional groundwater catchment up-gradient of the csac can be delineated as shown on Figure Please note that this catchment (Figure 18-14) is not the recharge zone to the flush (i.e. also referred to as the zone of groundwater contribution or ZOC). The groundwater recharge area to the flush is delineated below. The regional groundwater catchment is the area that potentially contributes groundwater flow to the csac and onwards towards the Sruffaunnamuingabatia Stream. The groundwater catchment extends back to the regional topographic divide which exists approximately 1.5km to the east of the csac. The regional groundwater catchment is important as it contains the entire potential groundwater flow paths that likely maintain the groundwater level in the vicinity of the csac. We return to this point later in the report during the groundwater flux impact assessment. ` Hydrochemistry Within the flush area itself the electrical conductivity of surface water ranged between 190 and 439µS/cm which is indicative of mineratrophic water, while ph values were between 6.2 and 6.7. The source of the mineratrophic waters on the surface of the bog within the flush are groundwater seepages as described in Section above. Electrical conductivity values for surface water outside the flush area were generally between 50 and 100µS/cm. These values show that the source of water within the majority of the man-made drains and on the vegetated surface of the blanket peat is meteoric in origin (i.e. from precipitation). The exception to this is drain D4 which receives runoff from the flush area of the csac and therefore showed an average electrical conductivity value of approximately 128µS/cm during the monitoring period (refer to Table 18-4). The electrical conductivity of the water in the bog pools within the csac was approximately 58µS/cm and therefore the source of water to these pools is also meteoric in origin and not from groundwater upwells. ph values for surface waters outside the flush area were generally in the same range as the flush water. As expected the field hydrochemistry of the phreatic tubes was essentially similar to the surface water hydrochemistry measurements, albeit slightly higher. Within the flush area electrical conductivity values were between 150 and 546µS/cm. Outside of the flush area (i.e. blanket bog surface) phreatic tube electrical conductivity values were generally between 70 and 90µS/cm which is characteristic of ombrotrophic peat water. The ph range was between 6.3 and 7.2 with the higher ph being recorded within the flush. For the deep peat piezometers (i.e. P1/P2) within the flush, electrical conductivity values ranged between 239 and 500µS/cm while ph values were between 6.2 and 7.2. The relatively high electrical conductivity values within the deep peat are a result of the upward gradient of mineratrophic water through the base of the peat. Outside the flush area deep peat electrical conductivity values were between 214 and 235µS/cm and this shows also that there is an upward gradient of mineral subsoil water into the blanket peat surrounding the flush, however the gradient is not sufficient to reach the surface of the bog as demonstrated by the deep peat water levels outside of the flush (i.e. C4 and C10). The hydrochemistry of the P1 piezometers (i.e. subsoil) and the boreholes is reflective of Iron Flush- Hydrology and Hydrogeology 18.20

36 the subsoil groundwater hydrochemistry beneath the peat. Within the deep perimeter boreholes electrical conductivity values ranged between 540 and 797µS/cm and ph ranged 6.8 and 7.6. Within the P1 piezometers inside the flush electrical conductivity values ranged between514 and 673µS/cm while ph ranged between 6.8 and 7.6. Higher electrical conductivities were generally observed in the deep perimeter boreholes, with BH3 and BH4 having the highest values. Analysis of groundwater from the perimeter boreholes and the P1 piezometers show that the groundwater is predominately a Ca-HCO 3 water type (refer to Table 18-21). However, a Ca-Cl water type was determined for piezometer C6A-P1 within the flush. Even where Ca-HCO 3 was determined as the water type, there were some notable hydrochemical variations between mineral subsoil groundwater of that type. This is thought to be due to the effects of recharge occurring on the elevated ground to the east of the flush as explained further below. In terms of spatial positioning BH3 and BH4 are located up-gradient and along gradient to the flush area respectively while BH1 and BH5 are located down-gradient (refer to Figure for groundwater flow direction). C2-P1 and C6A-P1 are located within the flush with C6A-P1 being up-gradient of C2-P1. The hydrochemical analyses show that electrical conductivity, total hardness, total alkalinity, dissolved solids and bicarbonate are generally higher in BH3 and BH4 compared C2-P1 and C6A-P1. BH3 is up-gradient of the flush and therefore it is likely that the groundwater here would have a similar hydrochemical makeup to that of the groundwater beneath the flush. The variation is less pronounced in sample round 4; however electrical conductivity was still notably higher in the up-gradient boreholes in comparison to the flush piezometer (C2-P1). This variation in hydrochemistry and water type between locations is likely due to the age difference between the deep regional groundwater flow and the groundwater flow which actually arises within the flush area. This variation in hydrochemistry can be explained by the effects of recharge occurring on the elevated ground to the east of the flush area. Where rainfall lands on exposed mineral soil it percolates down through the subsoil and forms a fresh layer of water on top of the deeper regional groundwater flow (limited mixing will occur in the short term). The groundwater level rise in the vicinity of BH3 as a result of recharge is shown on Plate 18-3 above. The hydrochemistry of the newly recharged upper groundwater layer will have lower levels of dissolved constituents due to the relatively short contact time with the surrounding geology compared to the deeper regional flow groundwater. The newly recharged water may also have higher levels of chloride (Cl - ) as a result of sodium chloride within sea spray (from frontal rain). This is potentially the reason why a Ca-Cl water type was found in C6A-P1 and not Ca-HCO 3. It is worth noting that C6A-P1 is the furthest up-gradient piezometer within the flush (that was sampled) and possibly intercepts a shallower groundwater type compared to the groundwater sampled at C2-P1. A Ca-HCO 3 type was recorded at C2-P1. The hydrochemical analysis completed to date indicates that it is the newly recharged groundwater that arises within the flush area and not the deeper regional groundwater as analysed in BH3 which is up-gradient of the flush (Note that BH3 was drilled to approximately 11.3m below ground level, with the screen interval between 9.3 and 11.3mbgl). This suggests that it is recharge within the elevated ground to the east of the csac that is Iron Flush- Hydrology and Hydrogeology 18.21

37 the hydraulic driving force which pushes mineratrophic water into the flush. The recharge within the elevated ground (i.e. the groundwater level at BH3 is approximately 1.2m over the potentiometric groundwater level at C2-P1 within the flush) facilitates a vertical hydraulic head up through the peat body and therefore creating groundwater upwells within the flush area. The water type of the bog pool water (which also represents the hydrochemistry of the phreatic water of the peat outside of the flush) and the surface water from the Sruffaunnamuingabatia stream are a Na-Cl and Ca-Cl type respectively. Both types indicate water that had little or no contact time with the mineral subsoil. The hydrochemistry of the Sruffaunnamuingabatia stream at the time of sampling indicates that the primary source of water was runoff from the peatland area, while the source of water to the bog pools is meteoric in origin (i.e. rainfall). Analysis of mineral subsoil groundwater outside and beneath the flush area showed relatively low levels of dissolved iron which is not reflective of the hydrochemistry on the surface of the flush where iron oxide precipitates are common. The maximum concentration of dissolved iron in groundwater sampled at C2-P1 and C6A-P1 was 31µg/l and <20µg/l respectively which is relatively low. In comparison the concentration of dissolved iron analysed in the phreatic tubes on the surface of the flush was between 1,100 and 33,240µg/l which is significantly higher than the underlying mineral subsoil groundwater. Ferric (III) and Ferrous (II) iron were reported at <50µg/l and <100µg/l respectively for the deep boreholes, and subsoil piezometer respectively. For SW1 and the flush discharge levels of Ferric (III) iron were reported at 70µg/l and 06µg/l respectively. Ferrous (II) iron was reported at <100µg/l for SW1 and flush discharge. The above hydrochemistry data indicates that iron is not present in significant concentrations within the underlying shallow groundwater system as analysed from the piezometers, and we have not seen iron pans or evidence of iron pans during the site investigation or within exposed mineral soils in the area of the csac. By eliminating an iron pan as a source of iron within the flush system, there are only three other possible sources of elevated iron in the discharge water from the flush that can be considered. These are listed below and shown schematically in Plate Surface water input (i.e. rainfall); 2. Shallow mineral soil groundwater (peat iron accumulation theory); and, 3. Discrete deep groundwater upwells (i.e. bedrock faults in the area of the csac). Iron Flush- Hydrology and Hydrogeology 18.22

38 Plate 18-7: Sources of Iron to the Flush Surface Water Input (i.e. rainfall) Analysis of bog pool water from within the csac shows that the concentration of iron in the water is generally less than 86µg/l, which is very low. The water in the bog pools is of rainfall origin and therefore rainfall can be ruled out as the source of iron to the flush Shallow Ground Water (peat iron accumulation theory) The high level of iron within the flush discharge water and not within the underlying shallow mineral subsoil could be as a result of iron retention within the body of the peat. It may be the case that as shallow mineral subsoil groundwater seeps up through the peat; the dissolved iron is removed from the groundwater and builds up in the peat over time. Studies relating to acid mine drainage have shown (J. Henrot & R. K. Wieder 1990) that peat has the ability to retain metals by means of chemical processes such as cation exchange, organic complexation and oxide precipitation which occur within the body of the peat. This means that high levels of dissolved iron within the groundwater flushing through the peat may not be required as a build up of iron within the peat will occur over time due to the chemical process mentioned above. The iron stored within the peat (along with various other metals) is then eventually released onto the surface of the flush as iron oxide. When the theory is assessed by means of mass balance of iron input and output from the flush (Refer to Plate 18-8), this theory is not plausible as the concentration of dissolved iron in the phreatic water (output) is greater than the concentration of dissolved iron in the shallow mineral subsoils groundwater (input). This means that there is more iron leaving the flush system than is being replaced by the groundwater from the shallow mineral subsoils (i.e. net loss of iron from the flush). It would be expected that the concentration of dissolved iron in the shallow mineral soil groundwater would be greater or equal to the phreatic tube water. Iron Flush- Hydrology and Hydrogeology 18.23

39 1,100-33,200 µg/l Fe Plate 18-8: Schematic of Iron Mass Balance for the Flush Discrete Deep Groundwater upwells (iron rich bedrock groundwater) The third possible source is that there is a discrete iron rich groundwater discharge from a deeper source, such as a fault in the bedrock, below the area of the flush which has not been detected by the perimeter boreholes or the mineral subsoil piezometers within the csac. There is no evidence locally to suggest this [no discrete spring within the flush, deep subsoils, no other anomalies in groundwater chemistry] is the case, but based on the concentration of iron in the flush discharge it is a possible source. Plate 18-9: Iron Oxide on the Surface of Flush. Iron Flush- Hydrology and Hydrogeology 18.24

40 Flush Surface Water Catchment & Groundwater Recharge Area Using the long term effective rainfall (854mm/yr) and the surface water catchment to the flush area, which is estimated to be 37,350m 2 (refer to Figure 18-5), the long term rain water input to the flush area is estimated to be 87.4m 3 /d (1L/s). This is in the same order as the total measured discharge from D4 which drains the flush area (i.e. combined surface water and groundwater input) which are presented in Table 18-4 above and was on average 1.2L/s over the monitoring period to date. This indicates that groundwater is a minor component of the flush discharge as rain water appears to make up much of the total discharge. [Note: The surface water catchment and the calculated average surface water discharge rate outlined above have no bearing on the groundwater calculations presented below, and the above are presented for characterisation purposes only]. To estimate the groundwater input to the flush area a back calculation of the mixing equation (shown below) was undertaken using (1) the average electrical conductivity of the mineral subsoil groundwater beneath the flush (i.e. at C2-P1 and C6A-P1), (2) the electrical conductivity of rainwater at the site (measured in bog pools), (3) the average electrical conductivity of the combined flush discharge measured at D4 and (4) the average discharge rate from the flush during the monitoring period measured in D4 at the v-notch weir. [Note: that the average effective rainfall is not used to determine the groundwater recharge/flow below]. C z x, y Q C x x, y Q x x Q C y Q y y Where: C z = Average electrical conductivity of the flush discharge at D4 (128µs/cm) Q x = Rainfall input - m 3 /d (to be determined by back calculation) C x = Rainfall electrical conductivity (a value of 60µs/cm is taken) Q y = Groundwater input - m 3 /d (to be determined by back calculation) C x = Average groundwater electrical conductivity analysed at C2 & C6A (546µs/cm) Based on an average total discharge rate of 103.7m 3 /d (1.2L/s) from the flush area the required surface water and groundwater flow input needed to give a downstream (i.e. after mixing) electrical conductivity of 128µs/cm in the discharge from D4 is 1.03L/s (88.9m 3 /d) and 0.17L/s (14.7m 3 /d) respectively. Based on an estimated groundwater discharge rate of 14.7m 3 /d the required recharge area to the flush can be estimated by determining a recharge coefficient that best reflects the geological conditions up-gradient of the flush. Recharge coefficients for various hydrogeological settings are published by the GSI and these are shown in Appendix 14H. Based on the local topography and an understanding of the hydrogeological conditions in the vicinity of the flush the maximum potential recharge area to the flush is estimated to Iron Flush- Hydrology and Hydrogeology 18.25

41 be 30,980m 2 (Refer to Figure 18-15:). Outside of this catchment area groundwater recharge is unlikely to contribute flow to the flush as it will flow away from the area of the csac. Based on this recharge area, the recharge rate (m/yr) required to sustain a long term groundwater discharge rate of 14.7m 3 /d at the flush is calculated as follows: Recharge (m/yr) = 14.7m 3 /day x 365 Recharge area (m 2 ) = 14.7m 3 /day x ,980 = 0.17m/yr Using an effective rainfall of 854mm/yr as calculated in Section 18.2 above, this equates to a recharge coefficient of 19.9% (0.17m/0.854m X 100%). Using the GSI recharge coefficient estimate table the hydrogeological setting that best describes the geological condition in the groundwater catchment to the flush is Peat in an Extreme vulnerability setting (Category 1.vi). This category has a suggested minimum recharge coefficient of 15% which is in the same order as the value calculated for the estimated maximum recharge area to the flush (19.9%). The water balance for the flush assumes that all recharge to the flush is occurring on the elevated ground to the east of the flush and does not consider that there is potentially discrete, deep, iron rich groundwater upwells arising from beneath the area of the csac. If it is the case that deep bedrock groundwater upwells are contributing flow to the flush discharge then the above water balance can be considered conservative as the surface area required to support shallow groundwater recharge (as indicated by the hydrochemistry) to the flush will actually be less. In addition a recharge coefficient greater than 19.9% is likely to apply for the recharge area to the flush area as peat is actually absent or very thin in places and exposures of mineral subsoil are visible on the surface. A higher recharge coefficient will mean a reduced recharge area and therefore the estimated current maximum recharge area of 30,980m 2 can be considered conservative and the actual recharge area required to sustain shallow groundwater flow to the flush is likely to exist somewhere within this zone. Following initial consultation with NPWS, and due to the importance and sensitivity of the flush, and also as a precautionary measure to ensure that there will be no potential impacts from any proposed future development in the area of the flush, the estimated maximum recharge area to the flush has been increased by 100%, and this extended area now accounts for some 61,960m 2. This extended area also covers all the higher ground on the ridge to the east of the flush, and therefore it also represents the likely maximum recharge area. Using a flush discharge rate of 14.7m 3 /d this gives a recharge rate of 0.086m/yr and a recharge coefficient of 10%, which is significantly under the GSI suggested minimum of 15%. The estimated and over estimated (by 100%) flush recharge areas are shown on Figure 18-15: Summary Hydro-geological Conceptual Model The superficial geology comprises moderate to low permeability sandstone tills which are saturated beneath the area of the csac and flush. The intact blanket bog overlying the mineral subsoils in the vicinity of the flush was determined to be between 0.9 and 4.1m by the HES investigation. Peat depths recorded in the core rich flush area itself were Iron Flush- Hydrology and Hydrogeology 18.26

42 between 2.74 and 3.26m. Previous studies indicate that depths of up to 6m could exist within the flush area. Groundwater level monitoring shows the mineral subsoil layer to be semi-confined by the peat in the area of the csac and flush. The potentiometric water level of the mineral subsoils was found to exist above ground level in the flush area. The semi-confined state of the groundwater beneath the peat has resulted in an upward hydraulic gradient through the base of peat and in some places (i.e. flush) onto the vegetated surface of the bog. The hydrochemistry of the surface water within the flush area confirms there is a mixing of ombrotrophic and minerotrophic waters and it is this hydrochemistry that sustains the flush vegetation. Analysis of mineral subsoil groundwater shows that there is a notable difference in the hydrochemistry up-gradient of the flush area and what actually discharges at the flush area. The groundwater which arises in the flush has slightly lower concentrations of dissolved solids, alkalinity and bicarbonate compared to the groundwater up-gradient of the flush. The difference in hydrochemistry indicates that it is a younger groundwater type that emerges within the flush and not older, deeper mineral subsoil groundwater flows. It is younger recharged groundwater within the elevated hill to the east of the csac that is the likely source of water to the flush. Water level monitoring shows the local subsoil groundwater flow direction beneath the flush to be in a westerly direction towards the Sruffaunnamuingabatia Stream. The regional groundwater catchment to the csac extends to the topographic divide to the east of the site. The regional groundwater catchment is also likely to be the source of any discrete, deep bedrock groundwater upwells that may be arising within the iron flush. For the purposes of the impact assessment on the flush it is assumed that the regional catchment is the source of the discrete deep groundwater flows that may be arising from the bedrock. Up-gradient of the flush (i.e. within the elevated ground to the east) the groundwater level is approximately 1.2m higher than the potentiometric groundwater level at the flush. This head difference combined with the partial-confining effects of the overlying peat is resulting in an upwelling of groundwater within the flush area. It is recharge on the elevated hill that is the mechanism that provides the head difference. Rainfall which lands and percolates into the mineral subsoils within the elevated ground forms the head difference over that of the flush area. It is this head difference that is the driving force which creates the groundwater upwells within the flush area. Based on conservative recharge estimates the groundwater recharge area to the flush exists completely within the elevated hill to the east of the csac. In order to be conservative an extended area covering the entire ridge has also been examined. Groundwater analysis shows that there are significantly lower concentrations of iron in the mineral subsoil shallow groundwater beneath the flush compared to the water on the surface of the flush. Three potential sources have been assessed and these include (1) rainfall input, (2) shallow, low dissolved iron, groundwater input/peat accumulation and (3) iron rich, deep groundwater upwells. The hydrochemistry indicates that rainfall is not the source due to very low levels of dissolved iron measured in the bog pools. The iron mass balance for the flush indicates that the peat iron accumulation model is also unlikely to be the case for the shallow groundwater. Based on the present understanding of the flush it is likely that the discrete, iron rich, deep groundwater upwells from bedrock is the possible Iron Flush- Hydrology and Hydrogeology 18.27

43 source. However, the impact assessment (as undertaken in Section 18.8 below) considers the potential shallow groundwater and deep groundwater sources in terms of potential impacts arising from the proposed wind farm IMPACT OF THE DEVELOPMENT - BELLACORICK IRON FLUSH Introduction The statutory criteria (EPA, 2002 and EPA, 2003) for the assessment of impacts require that likely impacts are described with respect to their extent, magnitude, complexity, probability, duration, frequency, reversibility and transfrontier nature (if applicable). The descriptors used in this environmental impact assessment are those set out in EPA (2002) Glossary Components of development which could impact on the iron flush The proposed wind farm development will comprise 112 turbines, 4 electrical substations, borrow pit, a visitor centre building and 85km of additional access roads. It is proposed that sand and gravel for turbine base and road construction will be sourced from an onsite borrow pit located at Easting and Northing (ITM centre point). As this section focuses on the iron flush area the location of the borrow pit including the locations of proposed turbines within 500m of the iron flush are shown on Figure and Figure The overall turbine layout is shown on Figure The setback distances from the csac boundary are shown in Table below. Table 18-22: Development Setback Distances from csac Boundary. Infrastructure Distance (m) T T T T Borrow pit 380 As regards proposed construction methods, the access roads will be excavated down to competent mineral subsoil and back filled with approximately 750mm of stone. In most parts of the site, and especially around the flush area, only approximately 1m of peat or less will require excavation to expose the underlying mineral subsoil. The turbine base foundations will be piled in the area of the csac to avoid dewatering that could be associated with foundation base excavation. It is proposed that the borrow pit, which will require excavation of gravels below the water table, will operate as a wet pit and thereby avoid the need for dewatering Description of Borrow Pit Area A shallow borrow pit is proposed to the southeast of the iron flush area. It has an area of approximately 171,200m 2 (or ~17Ha). The borrow pit area has some areas of shallow Iron Flush- Hydrology and Hydrogeology 18.28

44 residual peat remains overlying variable glacial tills, with a coarse sandy gravel horizon extending from approximately 0.6mbgl to 2.5mbgl. The proposed borrow pit is located approximately 380m to the southeast of the csac at its nearest point and approximately 980m at its furthest. A storage and loading area is proposed to the west of the borrow pit location. The borrow pit area drains to the southwest, with surface water flowing along the ground. It is proposed that the gravels in the borrow pit will be excavated to approximately 2m below ground level. Where the borrow pit requires excavation of gravels below the water table, it will operate as a wet pit, thereby avoiding the need for dewatering. The existing cutaway ground level in the borrow pit area lies in the range 98.0 to 100m OD, with an area at one corner at 101m OD. Hence the upper part of the borrow pit will drain from this corner to the centre. This will be similar to the present drainage system within the gravel from upstream. Based on the available site investigation data there is a high degree of variability within the till deposits at the proposed borrow pit, ranging from ([mainly] coarse GRAVELS to, sandy GRAVELS and gravelly SANDS in the central area to clayey GRAVELS on slightly higher ground to the west. With the evident variability in composition of the tills, there will also be an associative variability in permeability. While all locations have high water table, the coarse gravels have recorded high seepage rates and indicate high permeability, while where clay is noted seepage rates are recorded as minor. The material excavated from the borrow pit will be used for the construction of access roads and turbine base/hardstanding areas. The cleaner gravel dominant glacial tills recorded at the borrow pit have the potential to have higher permeability than surrounding clayey tills. The aerial photograph for the area and the digital elevation model indicate that the glacial ridge that forms the recharge area to the east of the flush bends towards the borrow pit in a south-south-easterly direction approximately 600m to the east of the flush discharge area. Given the topography (all of the borrow pit area is above the level of the discharge line within the flush at approximately 96mOD) and the variable nature of the till deposits, this area and the area of the borrow pit, could also potentially feed groundwater towards the groundwater catchment and recharge area of the iron flush. However, there are a number of factors that indicate that this potential flow regime is not possible: The glacial deposits are variable within the borrow pit and around it. As indicated above there are clayey gravels, which have lower permeability, recorded on the ridge to the north-northwest of the borrow pit area; BH2A drilling log, see Figure 18-4, records coarse gravels between 3-6mbgl, and this indicates that the more permeable gravels recorded in the central zone of the borrow pit area extend to the west-southwest [of the borrow pit] and will facilitate groundwater flow in that direction, i.e. the permeable gravels do not necessarily form a northnorthwest trend and therefore flow is not likely to contribute to the flush recharge area; Topographic contours show that ground levels fall from the borrow pit towards the west-southwest in the direction of the Sruffaunnamuingabatia Stream. This is in-line with the regional groundwater flow direction which was measured to be to the west/southwest in the area of the iron flush. Also, natural groundwater flow is more Iron Flush- Hydrology and Hydrogeology 18.29

45 likely to flow perpendicular to the local topography, unless there are significant variations in permeability, and the available geological data indicate that this is not the case; In order for groundwater to flow from the borrow pit to the flush area, groundwater would have to flow parallel to the topographic contours (i.e. north-northwesterly) of the borrow pit site and also against the regional groundwater flow direction which is to the west/southwest. The available site investigation data indicate that the geological conditions would not facilitate this potential flow regime. The flowpath from the centre of the borrow pit to the discharge zone in the flush is 1,120m long and the maximum groundwater flow gradient is The flowpath from the centre of the borrow pit to BH2A is 550m long and the maximum groundwater flow gradient is The flowpath from the centre of the borrow pit to the Sruffaunnamuingabatia Stream (perpendicular to contours) is 1,420m long and the maximum groundwater flow gradient is Given the indications that the gravels extend to the west-southwest below BH2A, and considering the higher gradients, groundwater flow from the borrow pit is occurring to the west-southwest, with discharge to the Sruffaunnamuingabatia Stream as per the regional groundwater flow model. Therefore, based on the points outlined above the regional groundwater flow below the borrow pit area is occurring independently of the flow regimes supporting the iron flush Disruption of Groundwater Flow Paths Towards the Iron Flush There are no proposed turbines, access roads or borrow pits located within the delineated recharge areas (current or maximum as defined in Section 18.6 above) to the flush area. Therefore there can be no direct impact on groundwater flow paths towards the flush within the recharge area. However, there are two proposed turbines, and associated access roads within the regional groundwater catchment up-gradient of the csac as shown on Figure These are offset from each other and would not form a continuous obstacle to groundwater flow. To assess the potential hydraulic effects of turbine bases on groundwater flow paths within the regional groundwater catchment towards the csac it is assumed that each turbine base is piled and that the piles act as a complete barrier to groundwater flow (which will not actually be the case as groundwater will simply flow around the imposed obstructions). The width of the turbine base perpendicular to the groundwater flow direction is approximately 30m. To assess the potential effects of a reduction in groundwater flow (flux) through the aquifer up-gradient of the csac, Darcy s Equation is applied as shown below: Q KAi Iron Flush- Hydrology and Hydrogeology 18.30

46 Where: Q = Discharge/flux (m 3 /d); K = Average Subsoil permeability (m/day); A = Cross-sectional area of saturated subsoils (average depth x width) upgradient of csac within the regional groundwater catchment; and, i = Groundwater gradient up-gradient of the csac. An average permeability of 7.05 x 10-7 m/s (0.061m/d) is taken for the mineral subsoil up-gradient of the csac (refer to Table 18-2 above). The results of a geophysical survey undertaken as part of the APEX Geoservices Ltd investigation (2003) indicate that 20 30m of mineral subsoil are present in the area of the csac. Using a conservative average subsoil thickness of 15m and a regional groundwater catchment width of 640m (refer to Figure 18-14), the cross-sectional area of saturated subsoils up-gradient of the csac is taken to be 9,600m 2. The horizontal groundwater gradient up-gradient of the csac is calculated to be (Refer to Section ). Using Darcy s Equation, the groundwater discharge rate (flux) through the mineral subsoils up-gradient of the csac prior to the installation of the piles is calculated to be ~7m 3 /d. Based on an average pile depth of 15m (i.e. depth to bedrock) and a turbine base width of 30m, the cross-sectional area of saturated subsoils up-gradient of the csac could potentially be reduced to 9,150m 2 across any one section of aquifer. Using Darcy s Equation, the groundwater discharge rate (flux) for this scenario is calculated to be 6.69m 3 /d. This accounts for a 4.7% reduction in groundwater discharge (flux) as a result of the piles being in place. However, in reality these piles will not act as a barrier to flow as groundwater will simply flow around any imposed obstruction, although there may be some slight mounding of groundwater up-gradient of the piles. The piling method of turbine base construction has been discussed with the construction team, and is considered the most appropriate method for the area up-gradient of the csac as there will be no requirement to dewater to install foundations. Approximately 41,500m 2 ( km 2 (0.415 ha)) of the proposed borrow pit area extends into the regional groundwater catchment up-gradient of the csac. As stated above, it is proposed that the borrow pit will operate as a wet pit (i.e. no dewatering), and in a manner that does not cause significant changes to the local or regional groundwater flow regime in the area, and therefore there will be no net loss of groundwater from the regional catchment area towards the flush. No Impact is predicted Reduction in Groundwater Recharge to the Iron Flush There are no proposed turbines, substations or access roads located within the delineated recharge areas (current or maximum as outlined in section 18.6 above) to the flush and therefore it will not be possible to reduce groundwater discharge from the flush Iron Flush- Hydrology and Hydrogeology 18.31

47 as a result of the proposed development being in place. However, there are approximately 0.013km 2 (0.13 ha) of proposed access road hardstanding (2.18km of 6m wide access road), km 2 (0.073 ha)of turbine base hardstanding (3,675m 2 per turbine) and m 2 (0.032 ha) of borrow pit loading area within the regional groundwater catchment up-gradient of the csac. The total area of the regional groundwater catchment up-gradient of the csac is approximately 1.3km 2 (13 ha). A significant reduction in recharge within the regional groundwater catchment up-gradient of the csac as a result of imposed hardstanding drainage could potentially result in a lowering of the water table in the vicinity of the flush and its direct recharge area. However, the total proposed hardstanding area within the regional groundwater catchment area only accounts for 1.8% of the total catchment area. Therefore there will be no impact on groundwater recharge within the regional groundwater catchment area up-gradient of the csac. Recharge will still occur from drains and attenuation ponds. The presence of 41,500m 2 ( km 2 ) of the proposed borrow pit within the regional groundwater catchment will not result in a net loss of groundwater flow towards the csac as there are no proposals for dewatering during its operation, and the pit will be operated in a manner that does not cause significant changes to the local or regional groundwater flow regime in the area. No impact is predicted Impact on Groundwater Levels in the Vicinity of the Iron Flush There will be no requirement to dewater during the construction of the turbine foundations. Also, as mentioned above the proposed borrow pit will operate as a wet pit and the turbine bases around the flush will be piled, thereby removing the need to dewater. As presented above, development within the regional groundwater catchment to the csac will not have the potential to impact on groundwater levels in the vicinity of the flush. No impact is predicted Potential Release of Hydrocarbons & other Chemicals There are no proposed turbines, access roads or borrow pits located in the delineated groundwater or surface water catchment to the flush area and therefore impacts on water quality within the flush cannot occur. No Impact is predicted Alteration of Surface Water Drainage in the Vicinity of the Iron Flush The surface water drainage in the vicinity of the iron flush is described in detail in Sections and above. The proposed locations of the turbines, roads and borrow pit in the vicinity of the iron flush do not drain to any of the man-made drains surrounding the flush. The catchment area to the drains in the vicinity of the flush are localised to the csac and therefore there will be no impact on the surface water drainage in the vicinity of the flush as a result of the proposed development, i.e. local drainage around the flush area will not be altered by any of the proposed wind farm construction works. No Impact is predicted. Iron Flush- Hydrology and Hydrogeology 18.32

48 Potential Hydrochemical Effects on the Flush due to Introducing Concrete Piles The piles used to support the foundation of the turbine bases will be made of reinforced concrete which has a high ph that could alter the ph of the flush. However, as discussed above there is no proposed development within the delineated recharge areas to the flush and therefore there can be no hydrochemical impact on groundwater emerging from within the flush. Introduction of piles within the regional groundwater catchment to the csac will not have an impact on groundwater emerging from the flush. The closest turbine is approximately 600m up-gradient of the csac and therefore the natural mixing/attenuation of groundwater within the subsoils would ensure that any alternation of the groundwater hydrochemistry would have returned to background levels on reaching the area of the csac. No Impact is predicted MITIGATION MEASURES BELLACORICK IRON FLUSH Assessment of potential impacts and mitigation measures (where required) during the construction phase of the wind farm are shown below Disruption of Groundwater Flow Paths Towards the Iron Flush Mitigation in place includes no dewatering in the area of the csac Reduction in Groundwater Recharge to the Iron Flush The proposed drainage network is designed so that all surface water runoff from hardstanding areas will be discharged into the same surface water catchment that it was originally collected in. Therefore, there will be no net reduction in groundwater recharge or surface water runoff within individual catchment areas Impact on Groundwater Levels in the Vicinity of the Iron Flush It is not anticipated that there will be any impact on groundwater levels due to the operation of the borrow pit. However, as a precautionary measure groundwater monitoring wells should be installed between the csac and the borrow pit location. Groundwater level monitoring should be undertaken prior, during and for a period after the operation of the pit. In the event of any significant change in observed groundwater levels, compared to baseline data recorded between 2003 and 2011, then the operations at the borrow pit could be reviewed and/or altered Potential Release of Hydrocarbons & other Chemicals As a general precautionary measure the following mitigation measures should be used in relation to refuelling and storage of hydrocarbons and other chemicals: No refuelling or maintenance of construction vehicles or plant should take place in the regional groundwater catchment area to the csac; On site re-fuelling should take place at a specific designated re-fuelling area. These refuelling areas should be bunded appropriately for the fuel usage volume for the time period of the construction and fitted with an appropriate oil interceptor; Iron Flush- Hydrology and Hydrogeology 18.33

49 Fuels stored on-site should be minimised. Where required, storage areas should be bunded appropriately for the fuel storage volume for the time period of the construction and fitted with a storm drainage system and an appropriate oil interceptor; and, The electrical substation should be bunded appropriately to the volume of oils likely to be stored, and to prevent leakage of any associated chemicals to groundwater or surface water. The bunded areas should be fitted with a storm drainage system and an appropriate oil interceptor Alteration of Surface Water Drainage in the Vicinity of the Iron Flush None required Potential Hydrochemical Effects on the Flush due to the Introducing Concrete Piles None required CONCLUSIONS ON BELLACORICK IRON FLUSH All of the proposed development areas in the vicinity of the iron flush are significantly outside the groundwater recharge area and surface water catchment area to the flush. As a result there is no potential to impact on groundwater flows or surface water to the flush area. In relation to the Habitats Directive, based on this assessment there will be no adverse impact on the integrity of the Bellacorick Iron Flush, and the Conservation Objectives set out in Section 18.2 of this report will not be affected as a result of the proposed wind farm development. As a precautionary measure it is recommend that monitoring of groundwater levels should be undertaken prior to construction, during construction and for a period after the operation of the borrow pit WIDER HYDROLOGICAL STUDY Introduction The purpose of the wider hydrological study is to identify other groundwater flush areas on the eastern part of the wind farm site and to undertake an assessment of potential recharge areas to these flushes. Potential impacts of the proposed wind farm development on these flushes are also assessed. A hydrological overview of the Formoyle flush (csac) is undertaken with respect to the location of the wind farm site and potential impacts on this flush area resulting from the proposed development are also assessed Schedule and methodology The following schedule of works has been completed as part of the wider hydrological study: Iron Flush- Hydrology and Hydrogeology 18.34

50 A GIS desk study mapping exercise of the wind farm site and the surrounding area was undertaken in order to identify mineral subsoil exposures and other potential recharge areas for flush zones; A one day workshop was undertaken on 15th June 2012 along with the project ecologists to locate potential flush areas by identifying changes in vegetation from aerial photography; A walkover survey along with field hydrochemistry mapping of pre-determined locations was undertaken by HES along with the project ecologist on 21st August and 28th September A brief walkover survey of a section of the Formoyle flush was also undertaken to assess field hydrochemistry and local drainage patterns; and, Surface water sampling at two identified flush zones within the wind farm site and at the Formoyle flush was undertaken on 28th of September 2012 (Refer to Table below) WIDER AREA HYDROLOGY & HYDROGEOLOGY In terms of regional hydrology the north-eastern section of the wind farm development lies within the Cloonaghmore River catchment while the south-eastern section lies within the River Moy catchment. Refer to Figure 18-2 for the Regional Hydrology map. The Downpatrick Formation which underlies the western section of the wind farm (including the Bellacorick Iron Flush csac) also underlies the eastern section of the wind farm. This bedrock type is classified as a Poor Bedrock Aquifer (Bedrock which is generally unproductive except for local zones). Soils in this area of the site are also dominated by cutover blanket peat. However, as with the western section of the wind farm, exposures of Devonian and Carboniferous sandstone tills and gravel deposits (i.e. esker like) are common in the area. The investigation of the Bellacorick Iron Flush indicates that shallow groundwater recharge zones to flushes are generally very localised to the flush area with the potential for more deeper iron rich bedrock groundwater upwells also. Areas where peat is absent or thin act as shallow groundwater recharge zones. This conceptual model of recharge (i.e. shallow recharge and deep groundwater upwells) has been considered when assessing the two small flushes zones located on the eastern section of the wind farm site as described below Locations assessed Petrfying Spring A spring/seepage area is located in an area of cutaway bog on the southeast of the wind farm site at coordinates E N (Refer to Figure 18-2). This is considered a good example of this rare habitat which is listed with priority status in Annex I of the EU Habitats Directive. This habitat is rated as having County Importance. Mineral subsoils here are exposed in the vicinity of the spring area. The spring comprises numerous low volume seepage points which appear to emanate from the mineral subsoils. The location of the spring is shown on Figure A photograph of the spring is shown on Plate Iron Flush- Hydrology and Hydrogeology 18.35

51 Plate 18-10: Spring/seepage area on the southeast of wind farm site. Peat in the area was noted to be generally absent. Exposures of sandstone till exist immediately to the east and north of the spring area. Discharge from the spring drains in a south-westerly direction towards a tributary of the Shanvolahan River (i.e. River Moy Catchment). Due to the numerous seepages zones within the spring area, measurement of flow was not possible on the day of the site visit. Field hydrochemistry measurements show a ph of approximately 8.2 and an electrical conductivity of 420µS/cm which indicates minerotrophic water. Hydrochemical analysis shows that the discharge from the spring is a Ca-HCO 3 which is the same groundwater type at the Bellacorick Iron Flush. The concentration of dissolved iron in the spring water was 29µg/l which is similar to the concentration of iron in the shallow groundwater beneath the Belllacorick Iron Flush (refer to Table below for hydrochemical analysis). The low levels of dissolved iron would suggest that deep iron rich groundwater is not contributing to the spring. Based on the topography of the area and the location of the mineral subsoil exposures, a preliminary groundwater catchment of approximately 48,000m 2 (0.48 ha) is delineated for the spring area (refer to Figure 18-16). Poor Flush Area A small poor flush area with a radius of approximately 25m is located in an area of cutaway bog on the southeast of the wind farm site at coordinates E N and Plate Cutover peat with an average depth of 1.5m exists in the area of the flush. The peat thins out towards the north of the flush area where mineral subsoil exposures were noted. A map showing the location of the flush is shown on Figure The poor flush area and the sounding cutaway peat drain in a north-easterly direction towards a tributary of the Cloonaghmore River. Measurement of discharge from the flush itself was not feasible due to surface water from the surrounding cutaway bog merging with water from the flush area. Field hydrochemistry measurements show a ph of approximately 7.5 and an electrical Iron Flush- Hydrology and Hydrogeology 18.36

52 conductivity of 200µS/cm which indicates minerotrophic water. Hydrochemical analysis shows that the water emerging from the poor flush area is a Ca-HCO 3 which is the same groundwater type as the Bellacorick iron Flush. The concentration of dissolved iron in the poor flush area water was 2000µg/l which is in the same range as the Bellacorick Iron Flush. No iron oxide deposits or iron pan were noted in the area of the poor flush area. This would then suggest that deeper iron rich groundwater upwells may also be contributing flow to this flush. Based on the topography of the area and the location of the mineral subsoil exposures a preliminary groundwater catchment of approximately 20,000m 2 (0,2 ha) is delineated for the flush area (refer to Figure 18-17). Plate 18-11: Poor flush area on the east of wind farm site. Formoyle Flush (within Bellacorick Bog ComplexcSAC) The Formoyle flush, which forms part of the Bellacorick Bog Complex (csac), is located adjacent to the eastern boundary of the proposed wind farm development an dis protected under Annex1 of the Habitats Directive. The flush area drains eastwards to the Owenmore River which is a sub-catchment of the regional Cloonaghmore River catchment. An estimate of the extent of the surface water and groundwater catchments to the flush is shown on Figure As part of the wider hydrological study a walkover survey of the western section of the Formoyle Flush was undertaken and therefore only findings of this survey are reported here. Located on the western side of the Formoyle flush are a series of discrete seepage points. Field hydrochemistry measurements show a ph of approximately 6.8 and an electrical conductivity of between 200 and 300µS/cm which indicates minerotrophic water. Iron Flush- Hydrology and Hydrogeology 18.37

53 Hydrochemical analysis shows that the discharge from the spring is a Ca-HCO 3 which is the same groundwater type at the Bellacorick Iron Flush. Based on the preliminary walkover survey of the site and the topography of the area the surface water catchment to the flush area is estimated to be approximately 1.4km 2 (14 ha). The estimated groundwater catchment to the discrete groundwater seepage points on the eastern side of the flush is 0.38km 2. As a conservative measure (as done with the Bellacorick iron flush regional catchment) the Formoyle flush groundwater catchment is extended west as far as the regional topographic divide. The potential for the proposed wind farm layout to impact on the water balance of this catchment and hence the Formoyle Flush is dealt with below. Table 18-23: Results of Wider Study Hydrochemical Analysis Parameter Units Spring Poor Flush Formoyle Flush ph ph Units Electrical Conductivity µs/cm Total Hardness mg/l Alkalinity (CaCO3) mg/l Bicarbonate mg/l Sodium mg/l Potassium mg/l <0.75 <0.75 <0.75 Chloride mg/l Sulphate mg/l 8 <1 <1 Nitrate (N) mg/l <0.2 <0.2 <0.2 Nitrite (N) mg/l <0.02 <0.02 <0.02 Ammonia N mg/l < <0.02 Calcium mg/l Magnesium mg/l Aluminium µg/l <5 <5 <5 Iron (Dissolved) µg/l Manganese (Dissolved) µg/l Ortho Phosphate (P) mg/l <0.02 <0.02 <0.02 Total Phosphorus (P) mg/l Total Dissolved Solids mg/l WIDER AREA IMPACT ASSESSMENT In relation to the spring located on the south-eastern section of the proposed wind farm site, there are no proposed roads or turbines located in the estimated groundwater catchment to the spring. No impact on the spring is anticipated. In relation to the poor flush located on the eastern side of the wind farm site there is one proposed turbine (T49) located within the estimated groundwater catchment to the Iron Flush- Hydrology and Hydrogeology 18.38

54 flush. Based on a geotechnical assessment, this has been determined to be the best location for this turbine as the peat depths at this location are thin compared to the surrounding peat. Locating the turbine outside of this area would create an unacceptable risk in terms of peat stability. In order to mitigate against impacting on the poor flush in terms of recharge, all runoff from the turbine hardstanding area will be discharged within the delineated groundwater catchment to the flush. The collected surface water runoff will be released by controlled outfalls onto the existing natural ground surface in the vicinity of the turbine. This method, which will assist in maintaining recharge volumes, will ensure that there will be no impact on the water balance of the poor flush. As stated above, the estimated surface water and groundwater catchments on the western side of the Formoyle flush csac appear to partially exist within the wind farm site boundary. However, there is no proposed infrastructure within the estimated surface water and groundwater catchments to the flush and therefore no impacts on the flush hydrology are anticipated. As a conservative measure the Formoyle flush groundwater catchment is extended west as far as the regional topographic divide which exists within the proposed wind farm site. This is the maximum (overestimated) groundwater catchment to the flush that could exist within the proposed wind farm site. The total area of this catchment is 2,000,000m 2 (or 2km 2 ) as shown on Figure There are approximately 15,000m 2 of proposed access road hardstanding (2.5km of 6m wide access road) and 22,050m 2 of turbine base hardstanding (3,675m 2 per turbine x no. 6) within this groundwater catchment up-gradient of the Formoyle Flush csac. This accounts for a total hardstanding area of 37,050m 2 within this catchment. A reduction in recharge within the overestimated groundwater catchment up-gradient of the Formoyle Flush as a result of imposed hardstanding drainage could potentially result in a reduction of groundwater flow to the flush. However, the total proposed hardstanding area within the overestimated groundwater catchment area only accounts for 1.8% of the total delineated catchment area. Therefore, there will be no impact on groundwater recharge within the overestimated groundwater catchment area up-gradient of the Formoyle Flush csac as a result of the proposed development. Also, the proposed drainage network is designed so that all surface water runoff from hardstanding areas will be discharged into the same surface water catchment that it was originally collected in. The collected surface water runoff will be released by controlled outfalls onto the existing natural ground surface locally within the catchment. The use of swales will also be established to promote recharge. These methods, which will assist in maintaining recharge volumes, will ensure that there will be no impact on the water balance of the flush. Therefore, there will be no net reduction in groundwater recharge or surface water runoff within individual catchment areas CONCLUSION ON WIDER AREA A small spring is located on the southeast of the wind farm at coordinates E N The spring comprises numerous low volume seepage points which appear to emanate from the mineral subsoil. Based on the topography of the area and the location of the mineral subsoil exposures, a preliminary groundwater catchment of approximately 48,000m 2 is delineated for the spring. There are no proposed turbines or road Iron Flush- Hydrology and Hydrogeology 18.39

55 infrastructure within the estimated groundwater catchment to the spring and therefore no impacts are anticipated. A small poor flush area with a radius of approximately 25m is located in an area of cutaway bog on the southeast of the wind farm site at coordinates E N The peat thins out towards the north of the flush area where mineral subsoil exposures were noted. No iron oxide deposits or iron pan were noted in the area of the flush. Based on the topography of the area and the location of the mineral subsoil exposures a preliminary groundwater catchment of approximately 20,000m 2 is delineated for the flush. There is one proposed turbine within estimated groundwater catchment to the flush. Drainage mitigation measures will ensure that there will be no net loss of recharge within the catchment to the flush. The Formoyle flush, which forms part of the Bellacorick Bog Complex (csac), is located adjacent to, but outside, the eastern boundary of the proposed wind farm development. Located on the western side of the Formoyle flush are a series of discrete seepage points which appear to be the source of minerotrophic water to the flush. The estimated groundwater catchment to the discrete groundwater seepage points on the western side of the flush is 380,000m 2 (or 0.38km 2 ). There are no proposed turbines or road infrastructure within the estimated surface water or groundwater catchment to the flush and therefore no impacts are anticipated. As a conservative measure the groundwater catchment is overestimated so that it incorporates the eastern side of the proposed wind farm development. The total area of the overestimated groundwater catchment is 2,000,000m 2 (or 2.0km 2 ) The total hardstanding area within this overestimated Formoyle flush groundwater catchment is 37,050m 2 (or km 2 ) which accounts for only 1.8% of the total catchment area. The small area proposed for development means that there will be no impact on surface water runoff or recharge within the catchment. Iron Flush- Hydrology and Hydrogeology 18.40

56 List of References APEX Geoservices Ltd 2003 Draft Report on the Geophysical Survey for the Oweninny Windfarm at Bellacorick, Co. Mayo. Eugene Daly Associates (EDA) 2003 Interim Report on the Hydrogeology of Bellacorick Iron Flush. Fojt, W Bellacorick Iron Flush, Co. Mayo. In: Mires Research Group, Field Excursion, Ireland 1988 (unpublished). IDL Ltd 1992 Bellacorick Wind Farm, Bellacorick, Co. Mayo Geotechnical Report (April 1992). Henrot J, & Weider K 1990 Processes of Iron and Manganese Retention in Laboratory Peat Microcosms Subjected to Acid Mine Drainage. Kelly M, 2005 Mineral Nutrient Analysis of Bog Flushes Containing Saxifrage Hirculus in. MSc Thesis (University of Dublin, Trinity College). Muldoon, C. S Conservation Biology of Saxifrage Hirculus L. in Ireland. PhD Thesis (University of Dublin, Trinity College). NPWS 2009 National Parks & Wildlife Services Conservation Statement Bellacorick Iron Flush csac (2009). Swarts M, Misstear BDR, Daly D & Farrell ER 2003 Assessing subsoil permeability for groundwater vulnerability.qj Eng Geol Hydrogeol 36: Iron Flush- Hydrology and Hydrogeology 18.41

57 Figure 18-1: Bellacorick Iron Flush Site Location Map Iron Flush- Hydrology and Hydrogeology 18.1

58 Figure 18-2: regional Hydrology Map Iron Flush- Hydrology and Hydrogeology 18.2

59 Iron Flush- Hydrology and Hydrogeology 18.3

60 Figure 18-3: Local Soils Map Iron Flush- Hydrology and Hydrogeology 18.4

61 Figure 18-4: Local Subsoils Map Iron Flush- Hydrology and Hydrogeology 18.5

62 Figure 18-5: Bellacorick Iron Flush csac Drainage and Vegetation Map Iron Flush- Hydrology and Hydrogeology 18.6

63 Figure 18-6: Bellacorick Iron Flush csac Local Drainage Map Iron Flush- Hydrology and Hydrogeology 18.7

64 Figure 18-7: Peat Depth Map Iron Flush- Hydrology and Hydrogeology 18.8

65 Figure 18-8: Bellacorick Iron Flush csac Site Investigation Network Iron Flush- Hydrology and Hydrogeology 18.9

66 Figure 18-9: Bellacorick Iron Flush csac Hydrochemistry Map Iron Flush- Hydrology and Hydrogeology 18.10

67 Figure 18-10: Durov Hydrochemistry Plot Iron Flush- Hydrology and Hydrogeology 18.11

68 Figure 18-11: Hydrogeological Cross Section A Iron Flush- Hydrology and Hydrogeology 18.12

69 Figure 18-12: Hydrogeological Cross Section B Iron Flush- Hydrology and Hydrogeology 18.13

70 Figure 18-13: Bellacorick Iron Flush csac Groundwater Contour Plot Iron Flush- Hydrology and Hydrogeology 18.14

71 Figure 18-14: Bellacorick Iron Flush csac Regional Groundwater Catchment Iron Flush- Hydrology and Hydrogeology 18.15

72 Figure 18-15: Bellacorick Iron Flush Recharge Area Iron Flush- Hydrology and Hydrogeology 18.16

73 Figure 18-16: Wider Hydrological Study Iron Flush- Hydrology and Hydrogeology 18.17

74 Figure 18-17: Wider Hydrological Study Flush Location Map Iron Flush- Hydrology and Hydrogeology 18.18

75 Iron Flush- Hydrology and Hydrogeology 18.19