Louth County Council
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Louth County Council Establishment of Groundwater Source Protection Zones Termonfeckin Water Supply Scheme Termonfeckin Borehole Groundwater Source Protection Zones November 2011 Revision: E Prepared by: Peter Conroy On behalf of the Geological Survey of Ireland With contributions from: Dr. Robert Meehan, Consultant Geologist; Jenny Deakin TCD; Natalya Hunter Williams, GSI And with assistance from: Louth County Council Geological Survey of Ireland Termonfeckin Public Water Supply Groundwater Source Protection Zones PROJECT DESCRIPTION Since the 1980’s, the Geological Survey of Ireland (GSI) has undertaken a considerable amount of work developing Groundwater Protection Schemes throughout the country. Groundwater Source Protection Zones are the surface and subsurface areas surrounding a groundwater source, i.e. a well, wellfield or spring, in which water and contaminants may enter groundwater and move towards the source. Knowledge of where the water is coming from is critical when trying to interpret water quality data at the groundwater source. The Source Protection Zone also provides an area in which to focus further investigation and is an area where protective measures can be introduced to maintain or improve the quality of groundwater. Louth County Council contracted GSI to delineate source protection zones for eight groundwater public water supply sources in Co. Louth. The sources comprised Ardee, Cooley (Carlingford and Ardtullybeg), Collon, Greenore, Termonfeckin, Omeath (Esmore Bridge and Lislea Cross), Drybridge and Killineer. This report documents the delineation of the Termonfeckin source protection zones. A suite of maps and digital GIS layers accompany this report and the reports and maps are hosted on the GSI website (www.gsi.ie). i i Geological Survey of Ireland Termonfeckin Public Water Supply Groundwater Source Protection Zones TABLE OF CONTENTS 1 INTRODUCTION .............................................................................................................................. 1 2 METHODOLOGY ............................................................................................................................. 1 3 LOCATION, SITE DESCRIPTION AND WELL HEAD PROTECTION ........................................... 1 4 SUMMARY OF BOREHOLE DETAILS ........................................................................................... 3 5 TOPOGRAPHY, SURFACE HYDROLOGY AND LANDUSE ......................................................... 4 6 HYDRO-METEROLOGY .................................................................................................................. 6 7 GEOLOGY ........................................................................................................................................ 6 7.1 BEDROCK GEOLOGY .............................................................................................................. 7 7.1.1 Karst Geology .................................................................................................................... 9 7.2 SOILS AND SUBSOILS ............................................................................................................ 9 7.2.1 Subsoil Permeability ........................................................................................................11 7.3 DEPTH TO BEDROCK ...........................................................................................................11 8 GROUNDWATER VULNERABILITY .............................................................................................12 9 HYDROGEOLOGY .........................................................................................................................12 9.1 GROUNDWATER BODY AND STATUS ................................................................................14 9.2 GROUNDWATER LEVELS, FLOW DIRECTIONS AND GRADIENTS ..................................14 9.3 HYDROCHEMISTRY AND WATER QUALITY .......................................................................17 9.4 AQUIFER CHARACTERISTICS .............................................................................................19 10 ZONE OF CONTRIBUTION........................................................................................................22 10.1 CONCEPTUAL MODEL ......................................................................................................22 11 DELINEATION OF SOURCE PROTECTION AREAS ...............................................................22 11.1 OUTER PROTECTION AREA ............................................................................................24 11.2 RECHARGE & WATER BALANCE .....................................................................................25 11.3 INNER PROTECTION AREA ..............................................................................................26 12 GROUNDWATER PROTECTION ZONES .................................................................................26 13 POTENTIAL POLLUTION SOURCES .......................................................................................29 14 CONCLUSIONS ..........................................................................................................................29 15 RECOMMENDATIONS ...............................................................................................................30 16 REFERENCES ............................................................................................................................30 APPENDIX 1 POINT DATA, WATER QUALITY DATA & BOREHOLE DATA APPENDIX 2 PUMPING TEST ANALYSES ii ii Geological Survey of Ireland Termonfeckin Public Water Supply Groundwater Source Protection Zones TABLES & FIGURES TABLES Table 1 Summary of Source Details ........................................................................................................ 4 Table 2 Bedrock Geology and descriptions around Termonfeckin Public Supply .................................. 7 Table 3 Aquifer types around Termonfeckin Public Supply ..................................................................20 Table 4 Estimated groundwater flow velocity (v, m/d) range in the bedrock aquifer.............................22 FIGURES Figure 1 Termonfeckin PWS site location map ...................................................................................... 2 Figure 2 Covered chamber for borehole PWSBH01 .............................................................................. 3 Figure 3 Mouth of borehole PWSBH01 inside borehole chamber. ........................................................ 3 Figure 4 Data points in the vicinity of Termonfeckin PWS site............................................................... 5 Figure 5 Bedrock geology of the study area........................................................................................... 8 Figure 6 Subsoil geology of the study area .......................................................................................... 10 Figure 7 Groundwater vulnerability around the study area .................................................................. 13 Figure 8 Borehole PWSBH01 Hydrograph December 2005 to May 2010 ........................................... 15 Figure 9 Borehole PWSBH01 Hydrograph on 29/04/2010 ................................................................... 15 Figure 10 Bedrock aquifer groundwater contours (non-pumping)........................................................ 16 Figure 11 Graph of Bacteria and Ammonia Concentrations at Borehole PWSBH01........................... 18 Figure 12 Graph of Nitrate and Chloride Concentrations at Borehole PWSBH01 ............................... 18 Figure 13 Graph of Manganese, Iron, Potassium and Potassium:Sodium Ratio at Borehole PWSBH01 ............................................................................................................................................................... 19 Figure 14 Bedrock aquifer and gravel aquifer map of the study area .................................................. 21 Figure 15 Schematic conceptual model of groundwater flow to Termonfeckin WSS borehole ........... 23 Figure 16 Source Protection Areas around Termonfeckin WSS borehole ........................................... 27 Figure 17 Source Protection Zones around Termonfeckin WSS borehole .......................................... 28 iii iii Geological Survey of Ireland Termonfeckin SPZ 1 INTRODUCTION Groundwater Source Protection Zones are delineated for the Termonfeckin Borehole source according to the principles and methodologies set out in ‘Groundwater Protection Schemes’ (DELG/EPA/GSI, 1999) and in the GSI/EPA/IGI Training course on Groundwater Source Protection Zone Delineation. The Termonfeckin borehole source supplies domestic water to the town of Termonfeckin. In this report, the borehole is referred to as PWSBH01. The objectives of the report are as follows: To outline the principal hydrogeological characteristics of the area surrounding the source. To delineate source protection zones for borehole PWSBH01. To assist the Louth County Council in protecting the water supply from contamination. Groundwater protection zones are delineated to help prioritise the area around the source in terms of pollution risk to groundwater. This prioritisation is intended as a guide in evaluating the likely suitability of an area for a proposed activity prior to site investigations. The delineation and use of groundwater protection zones is further outlined in ‘Groundwater