County Tipperary (South Riding) Groundwater Protection Scheme
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County Tipperary (South Riding) Groundwater Protection Scheme County Tipperary (South Riding) Groundwater Protection Scheme Main Report 2nd Revised Version, August 2001 Edmond Flynn, B.E., C.Eng., F.I.E.I., Donal Daly, Margaret Keegan County Engineer and Geoff Wright, Tipperary (South Riding) County Council Geological Survey of Ireland County Tipperary (South Riding) Groundwater Protection Scheme TABLE OF CONTENTS 1 INTRODUCTION 1 1.1. Location 1 1.2. Reasons for Adopting a Groundwater Protection Scheme 1 1.3. Scope and Objectives of this Report 1 1.7 Acknowledgements 8 2 GROUNDWATER PROTECTION – A PRIORITY ISSUE FOR LOCAL AUTHORITIES 9 2.1 Groundwater – A Resource at Risk 9 2.2 Groundwater Protection through Land-use Planning: A Means of Preventing Contamination10 2.3 ‘Groundwater Protection Schemes’ – A National Methodology for Preventing Groundwater Pollution 10 2.4 Objectives of the South Tipperary Groundwater Protection Scheme 11 2.5 Scope of County Tipperary (South Riding) Groundwater Protection Scheme 12 2.6 Tipperary (S.R.) County Development Plan 12 2.7 Structure of Report 12 3 BEDROCK GEOLOGY 15 3.1 Introduction 15 3.3 Devonian (Old Red Sandstone) 16 3.4 Carboniferous 17 3.5 Tertiary Deposits 19 3.6 Structural History 19 4 SUBSOILS (QUATERNARY) GEOLOGY 20 4.2 Availability of Information 20 4.3 Subsoil Types 20 4.4 Till 21 4.6 Till-with-gravel 21 4.7 Marl 22 4.8 Alluvium 22 ii County Tipperary (South Riding) Groundwater Protection Scheme 4.9 Peat (Bog) 22 4.10 Subsoil Thicknesses 22 4.11 Distribution of Deposits 22 4.12 Hydrogeological Significance 24 5 HYDROGEOLOGY AND AQUIFER CLASSIFICATION 25 5.1 Introduction 25 5.2 Data Availability 25 5.3 Groundwater Usage 26 5.4 General Aquifer Classification 26 5.5 Silurian Rocks 28 5.4 Old Red Sandstone (ORS) 29 5.7 Kiltorcan Sandstone (KT) & Porter’s Gate (PG) formations 29 5.8 Dinantian Limestones 30 5.9 Volcanics 33 5.10 Namurian (NAM): Killeshin Siltstone (KN), Bregaun Flagstone (BE) & Giant’s Grave (GG) formations 34 5.11 Westphalian (Coal Measures) rocks 34 5.12 Sands and Gravel aquifers 35 5.13 Summary of Aquifer Categories 36 5.14 Potential for Future Groundwater Development in South Tipperary 36 6 - HYDROCHEMISTRY AND WATER QUALITY 38 6.1 Sources of information 38 6.2 Hydrochemical Characteristics 38 6.3 Water Quality 40 6.4 Implications for Vulnerability Assessment 40 6.5 Quality of the Sources 42 7 GROUNDWATER VULNERABILITY 43 7.1 Introduction 43 7.2 Sources of Data 43 iii County Tipperary (South Riding) Groundwater Protection Scheme 7.3 Method of Evaluation 43 7.4 Vulnerability Classification 45 7.5 Application of Vulnerability Classification in South Tipperary 45 7.6 The Vulnerability Map 45 8 GROUNDWATER PROTECTION 48 8.1 Introduction 48 8.2 Source Protection Areas 48 8.3 Resource Protection Zones 49 8.4 Groundwater Protection Response Matrices 49 8.5 Groundwater Protection Map 50 6.3 Groundwater Source Protection Reports and Maps 50 6.4 Conclusion 50 9 ADDITIONAL RECOMMENDATIONS 51 10 REFERENCES 52 iv County Tipperary (South Riding) Groundwater Protection Scheme GROUNDWATER PROTECTION IN COUNTY TIPPERARY (SOUTH RIDING) 1 Introduction 1.1. Location South Tipperary (Fig.1.1) encompasses an area of 2258 sq. km and is bisected by the River Suir. The central part of the county, comprising the valleys of the Suir and its tributaries, the Multeen, Ara, Aherlow, Anner and Tar, has a general elevation between 60 m and 122 m above sea level. This central area is fringed by upland areas: the Comeraghs and Knockmealdowns in the south, the Galtees in the west, Slieve Phelim and Slievenamon in the east, and the Slieveardagh Hills in the northeast. South Tipperary has five administrative authorities: Tipperary (South Riding) County Council, Clonmel Corporation, Tipperary, Carrick-on-Suir and Cashel Urban District Councils. Over half the population of approximately 77,000 lives in the urban areas. Agriculture is the most important industry, with more than 80% of the area comprising farming land, the vast majority with a wide use range. The two most important types of enterprise are cattle production and dairying. Pig production has increased slightly and has become specialised in recent years, developing large integrated pig units. Less than one tenth of the area is devoted to tillage; barley and wheat are the most important crops. The other 20% of the land is mountainous and predominantly under forestry. 1.2. Reasons for Adopting a Groundwater Protection Scheme Groundwater is widely used in South Tipperary. Demand for groundwater is continuing and is likely to increase. The numerous large springs and large baseflow in the rivers indicate a major groundwater resource which requires appropriate protection. Further development of agriculture and industry over recent years has increased the risk of groundwater pollution. Tipperary (South Riding) County Council commissioned this study to develop a Groundwater Protection Scheme to ensure that due account is taken of the ‘groundwater interest’ in the development process. 1.3. Scope and Objectives of this Report 1.3.1 Scope This report outlines the geology, hydrogeology and groundwater quality of South Tipperary. This basic information has been used to prepare interpretive maps which will facilitate planning and resource development in the form of a Groundwater Protection Scheme and associated Groundwater Protection Response Matrices. The purpose of the scheme is to enable initial screening of potentially polluting activities. The effectiveness of the scheme depends to a large degree on its integration into the County Development Plan. The quality of the data is such that the scheme can be neither pollutant- nor site-specific. However, it does reduce the number of areas to be studied in detail by identifying those with the greatest or least limitations. The scheme should be periodically modified as further relevant information becomes available. 1.3.2 Objectives a) An evaluation of the extent, value and general vulnerability of the groundwater resources of the county. b) Protection of groundwater in Tipperary (South Riding) by the formulation of a Groundwater Protection Scheme and associated Groundwater Protection Response Matrices. 1 County Tipperary (South Riding) Groundwater Protection Scheme 2 County Tipperary (South Riding) Groundwater Protection Scheme 3 County Tipperary (South Riding) Groundwater Protection Scheme c) A review of legislation relating to groundwater protection in Ireland and proposals for fitting the protection scheme into the County Development Plan. d) Detailed study of the vulnerability of a limited number of groundwater sources. Although the main focus is on groundwater protection, the overall objective was to collect, compile and assess all readily available data on the geology, hydrogeology and groundwater quality to facilitate both groundwater resource management and public planning. The general groundwater protection scheme guidelines used by the GSI are given in Chapter 2. These are the basis for the county protection scheme and provide the structure for this report. A suite of environmental geology maps accompany the report, as follows: (i) Primary Data or Basic maps • Bedrock geology map • Subsoils (Quaternary geology) map • Outcrop and depth to bedrock map • Hydrogeological data map (ii) Derived or Interpretive Maps • Bedrock aquifer map • Potential gravel aquifer map • Groundwater vulnerability map (iii) Land Use Planning Map • Groundwater Protection Zones Map These maps can be used not only to assist in groundwater development and protection, but also in decision-making on major construction projects such as pipelines and roadways. 1.4 Physical Characteristics The county of Tipperary (South Riding) has maximum dimensions east to west of 64 km and north to south of about 53 km. It is bisected by the River Suir. There are seven physiographic regions - five uplands and two lowlands (Fig 1.1 and Table 1.1). The five uplands are characterised by impermeable rolling ground dissected by numerous small streams. Gradients are steep, runoff is very rapid, and river flows tend to be very ‘flashy’. The lowlands are part of the limestone plain of the ‘Golden Vale’, drained by the lower Suir river and its tributaries. The water table is usually less than ten metres below ground. The surface drainage of the lower Suir basin (within South Tipperary) is shown in Fig. 1.2 and is divided into sub-catchment basins. 4 County Tipperary (South Riding) Groundwater Protection Scheme Table 1.1 Summary of Physiographic Regions in South Tipperary Physiographic Geological Main General Peaks/Highest Land Use Region Succession Rivers Ground Ground (m. O.D.) Elevation, m Slieve Phelim Quaternary Multeen 120 - 275 Knockastanna, 447 Mountain Uplands Devonian Knockalough, 428 sheep grazing, Amenity, Silurian Ring Hill, 426 Forestry Middle Suir Quaternary Suir 60 – 120 Killough Hill, 236 Tillage, Lowlands Carboniferous Multeen Mount O’Meara, 207 Grassland Sleieveardagh Quaternary Kings 120 – 275 Renaghmore, 344 Unsuitable for Uplands Carboniferous Munster Boggan, 335 tillage, limited potential for Clashawley grassland, forestry Slievenamon Quaternary Lingaun 120 – 450 Slievenamon, 722 Forestry, Uplands Devonian Anner Carrickabrock, 567 Sheep grazing Knockahunna, 504 Golden Vale Quaternary Suir 30 – 90 Bennets, 183 Tillage, Lowlands Carboniferous Aherlow Grassland Devonian Tar Anner Moyle Kockmealdo Quaternary Duag 120 – 400 Knockshanahulion, Forestry, wn Uplands Devonian Tar 565 Sheep grazing Farbreaga, 520 Galtee Quaternary Aherlow 120 - 640 Dawson’s Table, Thin soils, Uplands Carboniferous Behanagh 920 Forestry Devonian Attychraan Greenane, 803 Silurian Sturraken, 520 1.5 Soils and Land Use The nature of the parent material is a principal factor in determining differences in soil properties and hence soil types. There is a wide range of bedrock and subsoils and hence soil types in the county. The lowlands have well drained soils which are deep, medium textured, well drained, have good moisture holding capacities and are good for tillage. The parent materials are limestone tills, sands and gravels. The upland areas are characterised by poorly drained soils and therefore their uses are limited (Table 1.2).