Version 1 December Hydrometric and Groundwater Section Office of Environmental Assessment

Transcription

1 METHODOLOGY FOR ESTABLISHING GROUNDWATER THRESHOLD VALUES AND THE ASSESSMENT OF CHEMICAL AND QUANTITATIVE STATUS OF GROUNDWATER, INCLUDING AN ASSESSMENT OF POLLUTION TRENDS AND TREND REVERSAL Hydrmetric and Grundwater Sectin Office f Envirnmental Assessment Versin 1 December 2010

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3 METHODOLOGY FOR ESTABLISHING GROUNDWATER THRESHOLD VALUES AND THE ASSESSMENT OF CHEMICAL AND QUANTITATIVE STATUS OF GROUNDWATER, INCLUDING AN ASSESSMENT OF POLLUTION TRENDS AND TREND REVERSAL Authrs: Matthew Craig and Dnal Daly Hydrmetric and Grundwater Sectin Aquatic Envirnment Office f Envirnmental Assessment Envirnmental Prtectin Agency An Ghnímhaireacht um Chamhnú Cmhshail Jhnstwn Castle Wexfrd Ireland Telephne: LCall: Fax: inf@epa.ie Web site: i

4 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Envirnmental Prtectin Agency 2010 Althugh every effrt has been made t ensure the accuracy f the material cntained in this publicatin, cmplete accuracy cannt be guaranteed. Neither the Envirnmental Prtectin Agency nr the authr(s) accept any respnsibility whatsever fr lss r damage ccasined, r claimed t have been ccasined, in part r in full as a cnsequence f any persn acting r refraining frm acting, as a result f a matter cntained in this publicatin. All r part f this publicatin may be reprduced withut further permissin, prvided the surce is acknwledged. METHODOLOGY FOR ESTABLISHING GROUNDWATER THRESHOLD VALUES AND THE ASSESSMENT OF CHEMICAL AND QUANTITATIVE STATUS OF GROUNDWATER, INCLUDING AN ASSESSMENT OF POLLUTION TRENDS AND TREND REVERSAL Published by the ENVIRONMENTAL PROTECTION AGENCY, IRELAND Versin 1 December 2010 ii

5 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Acknwledgements The authrs wish t gratefully acknwledge the UKTAG Grundwater Task Team, the Irish WFD Wrking Grup n Grundwater and all thse wh cntributed t and reviewed this publicatin. In particular the authrs wuld like t acknwledge Jenny Deakin fr reviewing the publicatin, the Department f the Envirnment, Heritage and Lcal Gvernment fr their advice and SNIFFER fr the WFD Visual image ( iii

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7 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Cntents 1. Intrductin 1 2. Threshld Values Ratinale fr Threshld Values Drinking Water Prtected Areas and General Chemical tests Surface Water Eclgical/Chemical and GWDTE Chemical tests Saline (r Other) Intrusins test Applicatin f Threshld Values Reprting f Threshld Values 7 3. Chemical Status Classificatin Saline (r Other) Intrusins Test Impact f Grundwater n Surface Water Eclgical/Chemical Status Test Grundwater Dependent Ecsystems (GWDTE) - Chemical Assessment Test Drinking Water Prtected Area Test General Chemical Assessment Test Quantitative Status Classificatin Saline (r Other) Intrusins Test Impact f Grundwater n Surface Water Eclgical/Quantitative Status Test Grundwater Dependent Ecsystems (GWDTE) - Quantitative Assessment Test Water Balance Test Trends and Trend Reversal Assessments f Pllutin Intrductin Backgrund Requirements fr Trend and Trend Reversal Assessment Methdlgy Future Requirements References 44 Annex 1 46 iv

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9 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends 1 Intrductin The Eurpean Cmmunities Envirnmental Objectives (Grundwater) Regulatins, 2010 (S.I. 9 f 2010) establish a new strengthened regime fr the prtectin f grundwater in line with the requirements f the Water Framewrk Directive (2000/60/EC) and the Grundwater Directive (2006/118/EC). Parts (IV) (VI) f the Regulatins identify the Envirnmental Prtectin Agency as the respnsible bdy fr establishing and maintaining a list f Threshld Values (TVs) fr pllutants in grundwater, assessing the chemical and quantitative status f grundwater bdies and undertaking pllutant trend and trend reversal assessments. Under Regulatins 48 52, the Envirnmental Prtectin Agency is required t establish, and where apprpriate maintain and update, a list f TVs fr pllutants in grundwater. Threshld Values nly have t be derived fr pllutants placing a grundwater bdy at risk f failing t achieve a WFD bjective. The values are used as triggers t help determine whether the cnditins fr gd chemical status are being met. Regulatins identify the cnditins fr assessing grundwater bdy status. The achievement f gd grundwater status invlves meeting this series f cnditins, which are designed t satisfy the criteria defined in the WFD and the Grundwater Directive. In rder t assess whether these cnditins are being met, a series f tests has been prescribed fr each f the quality elements defining gd (chemical and quantitative) grundwater status. There are five chemical and fur quantitative tests (Figure 1). Each test is applied independently and the results are cmbined t give an verall assessment f grundwater bdy chemical and quantitative status. The wrst-case classificatin frm the relevant chemical status tests is reprted as the verall chemical status fr the grundwater bdy, and the wrst-case classificatin f the quantitative tests is reprted as the verall quantitative status fr the grundwater bdy. The wrst result f the chemical and quantitative assessments is reprted as the verall grundwater bdy status. Part VI f the Regulatins indicates that the Envirnmental Prtectin Agency shall undertake an assessment f pllutin trends. This includes the identificatin f significant and sustained upward trends in the cncentratin f pllutants in grundwater bdies r grups f bdies identified as being at risk f failing t achieve the bjectives f the WFD. Where necessary, the Envirnmental Prtectin Agency shuld undertake an assessment f trends t verify that plumes frm cntaminated sites d nt expand t such an extent that they put a grundwater bdy at pr status. The Envirnmental Prtectin Agency must als identify the starting pint fr trend reversal. The starting pint fr trend reversal is t be expressed as a percentage f the relevant grundwater quality standard r TV. The start date fr trend reversal is based n the significance f the trend and the risk assciated with failing an bjective f the WFD. The assessment f trends in grundwater pllutant cncentratins is als required in tw f the chemical status assessments. Fr the Drinking Water Prtected Area and Saline Intrusin tests, trend assessments are required, n a case by case basis, where TVs have been exceeded fr ne r mre pllutants. The classificatin assessments have generally fllwed the prcedures set ut in EU Guidance Dcument N. 18: Guidance n Grundwater Status and Trends (EC, 2009), UKTAG Paper 11b(i): Grundwater Chemical Classificatin fr the purpses f the Water Framewrk Directive and the Grundwater Daughter Directive (UKTAG, 2008a), UKTAG Paper 11b(ii): Grundwater Quantitative Classificatin fr the purpses f the Water Framewrk Directive (UKTAG, 2008b) and UKTAG Guidance n Grundwater Trend Assessments (UKTAG, 2009). 1

10 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Figure 1 Overview f the status assessment (Classificatin) prcess (UKTAG, 2008a) The results f chemical status, quantitative status, verall status and trend assessments are reprted in the River Basin Management Plans fr each River Basin Management District 1, and are available frm the WFD Ireland Water Matters website ( Regulatin 58 places a duty n the Envirnmental Prtectin Agency t prepare and publish a detailed technical reprt cntaining: a) The methds and prcedures used t assign grundwater quantitative status; b) The methds and prcedures used t assign grundwater chemical status; c) All Threshld Values established fr all bdies r grups f bdies f grundwater, tgether with a summary f the infrmatin regarding the relevant pllutants and their indicatrs; 1 See individual River Basin District websites fr the reprts, e.g. fr the Suth Eastern River Basin District. 2

11 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends d) The methds and prcedures used t identify thse bdies which are subject t a significant and sustained upward trend in cncentratin f any pllutant, r which are shwing a reversal f that trend, and hw trend assessment frm individual mnitring pints within a bdy r a grup f bdies f grundwater has cntributed t this identificatin; e) The reasns fr the starting pints fr pllutin trend reversal; f) Where undertaken by the Agency and ther parties, the results f the additinal mnitring and trend assessments fr identified pllutants used t verify that plumes frm cntaminated sites d nt expand, d nt cause the chemical status f the bdy r grup f bdies f grundwater t deterirate and d nt present a risk t human health and the envirnment. The remainder f this reprt prvides infrmatin n the establishment f TVs and hw they are used in the chemical status assessments. The reprt then dcuments the methds and prcedures used t assess the chemical and quantitative status f grundwater bdies. Finally, the dcument prvides infrmatin n the methds and prcedures used t assess pllutin trends and trend reversal. 3

12 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends 2 Threshld Values Threshld Values are grundwater quality standards that are t be established by each Member State fr the purpse f assessing the chemical status f grundwater bdies 2. Threshld Values are als used when undertaking trend assessments. They can be set natinally r n a lcal grundwater bdy scale. They are triggers, such that their exceedance prmpts further investigatin t determine whether the cnditins fr Gd Status have been met. As such, they d nt represent the bundary between gd and pr status. Regulatin 40 states that when assessing chemical status, the grundwater quality standards fr nitrates and pesticides, prescribed in the Directive, shall be used. Hwever, Schedule 4 f the Regulatins indicates that mre stringent TVs may be required fr nitrates and pesticides t ensure the requirements f ther Directives are met. In additin, TVs are required fr ther pllutants that have been identified as cntributing t the characterisatin f grundwater bdies being at risk f failing t achieve a WFD bjective. Schedule 2 f the Regulatins prvides the minimum list f pllutants that need t be cnsidered when setting TVs. The grundwater quality standards prescribed fr nitrate and pesticides are used in the assessment prcess in the same way. Hwever, if all standards and TVs are met at all mnitring pints in the Natinal Grundwater Mnitring Netwrk then, under Regulatin 43(a), the grundwater bdy is cnsidered t be at Gd Status and n further investigatin is necessary. The TV fr each status test must be apprpriate t the receptr being cnsidered fr that test, e.g. an assciated surface water bdy, a grundwater dependent terrestrial ecsystem (GWDTE) r grundwater that is used, r culd be used fr drinking water supply. The way in which mnitring data are cmpared t the TVs during classificatin (i.e. whether data are aggregated acrss the grundwater bdy r used in islatin) varies between the individual classificatin tests. This is essential t ensure a reliable assessment f status. 2.1 Ratinale fr Threshld Values Threshld Values nly have t be derived fr pllutants placing a grundwater bdy at risk f failing t achieve a WFD bjective. In ttal there are five chemical status tests, althugh in practice, the bjectives f the Drinking Water Prtected Areas and General Chemical tests are similar, in that they are bth designed t assess the impact f pllutants n water that is used, r culd ptentially be used, fr human cnsumptin. The Surface Water Eclgical/Chemical and GWDTE Chemical tests are als similar in nature, in that they are designed t assess the impact f pllutants n receptrs assciated with grundwater bdies. 2.2 Drinking Water Prtected Areas and General Chemical tests Drinking water standards are expressed as maximum admissible cncentratins, i.e. peak cncentratins. Therefre, t ensure cnsistency, the assessment f grundwater in relatin t drinking water criteria, i.e. fr the Drinking Water Prtected Area and General Chemical status tests, shuld als be made against peak cncentratins. As grundwater quality mnitring prgrammes are nt cntinuus, it is likely that peak cncentratins in pllutants will be missed. Cnsequently a statistical apprach is required t take accunt f this. T ensure a cnsistent apprach thrughut classificatin, cmparisn f mnitring data against a standard r TV shuld be based upn a 95 th percentile r equivalent apprach (UKTAG, 2008a). Hwever, grundwater quality data are ften nt cllected frequently enugh t derive statistically rbust 95 th percentiles. If the 95 th percentile cannt be used, a suitable TV is required, against which mean cncentratins in the mnitring data can be cmpared with 2 Whilst the standards and cnditins that are applied t envirnmental permits shuld reflect the need t meet all WFD bjectives, including gd chemical status, these are nt TVs. 4

13 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends adequate cnfidence (UKTAG, 2008a). The utcme shuld, as far as pssible, be equivalent t using a 95 th percentile. Where there are sufficient reliable mnitring data fr each individual site, then the 95 th percentile value is calculated and used as the TV. Where data are insufficient t calculate 95 th percentiles fr individual sites, the TV must be set s that, if the mean f a dataset is nt exceeded, there is a reasnable expectatin that the 95 th percentile wuld nt exceed the maximum admissible cncentratin, if thse 95 th percentiles culd be calculated. On this basis, the UKTAG guidance (2008a) prpses that were insufficient data are available t determine the 95 th percentile, the TV shuld be set at a value f 75% f the relevant drinking water standard. This percentage has been selected because it takes int accunt the large variability in hydrgelgical settings, ptential tempral variability in parameter values and because it intrduces what is believed t be an adequate degree f prtectin such that the risk f misclassificatin is acceptable. Insufficient data were available t calculate the 95 th percentile fr mnitring sites in the Irish Natinal Grundwater Mnitring netwrk during the 1 st River Basin planning cycle. Therefre, 75% f the relevant drinking water standard has been used t calculate the TV. The 95 th percentile will be calculated during the 2 nd River Basin planning cycle, and TVs will be revised if the 95 th percentile is significantly different t the current TVs. As part f the Article 5 Risk Assessment (Wrking Grup n Grundwater, 2005), anthrpgenic pressures and histrical grundwater quality data were used t determine which pllutants were causing grundwater bdies t be at risk f failing t meet the WFD bjectives. Hwever, with regard t drinking water, TVs culd nt be derived fr parameters that did nt have an existing drinking water standard. Additinally, in Ireland very little data were available t determine if pint surce pllutants were impacting n drinking water surces, as very few f these pllutants require assessment under the Drinking Water Regulatins (S.I. 278 f 2007). In general, the main pllutants (r indicatrs f pllutin) that are putting grundwater bdies at risk f failing WFD bjectives with regard t drinking water requirements are derived frm the fllwing pressures: Agricultural Pressures: Nitrate, Electrical Cnductivity, Nitrite, Ammnium, Chlride and Pesticides; Pint Surce Pressures (e.g. Landfill, Cntaminated Land, Urban Pressures, Discharge t Grundwater): Nitrate, Electrical Cnductivity, Nitrite, Ammnium, Chlride, Sulphate, Sdium, Brn, Cyanide, Chrmium, Arsenic, Lead, Nickel, Mercury, Cadmium, Cpper, Aluminium and selected Organics; Mining: Electrical Cnductivity, Chlride, Sulphate, Chrmium, Arsenic, Lead, Nickel, Mercury, Cadmium, Cpper and Aluminium. The TVs fr metals in the Grundwater Regulatins are taken t be disslved metals, whilst the Drinking Water Standards fr metals are taken t be ttal metals. Althugh the TVs are derived frm the Drinking Water Standards fr metals, it shuld be recgnised that the standards relate t different assessments. TVs have been derived fr disslved metals and nt ttal metals because, frm an envirnmental perspective, the disslved fractin is a better representatin f the bilgically active prtin f the metal when cnsidering water ging t rivers and springs. Mst grundwater supplies are unfiltered because there is little sediment and in mst instances the results f ttal and disslved analysis in grundwater shuld be similar, if nt the same. Therefre, while the TVs are based n Drinking Water Standards, frm an envirnmental perspective the disslved fractin is mre representative than what is measured at the tap (which includes metals bund t sediment in the water supply netwrk). The disslved metal 5

14 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends cncentratin shuld be similar t the ttal cncentratin in grundwater befre it reaches the water supply netwrk, and as such, it is a cmparisn f the disslved metal cncentratin that shuld be made with the TV. 2.3 Surface Water Eclgical/Chemical and GWDTE Chemical tests In surface waters and wetlands, TVs are nly required fr thse pllutants that are cnsidered t be cntributing t water quality prblems in thse surface waters r wetlands, and where a surface water Envirnmental Quality Standard (EQS) r wetland trigger actin value has been established. As the assciated receptr must be at less than Gd Status, r have suffered eclgical damage, the TV shuld relate t the water quality standard r trigger actin value that has caused the prblem in the assciated receptr. The grundwater cntributin t surface water bdies and wetlands varies because f differences in rainfall distributin, sil and subsil type, aquifer type, hydraulic cnnectivity with the receptr etc. T ensure cnsistency in the status assessments, the TV needs t be derived frm the surface water EQS r wetland trigger actin value. Thereafter, if the TV is exceeded at a mnitring pint in the grundwater bdy, further investigatin will cnsider the site-specific dilutin and attenuatin factrs and the grundwater cntributin t the assciated receptr. Surface Water EQSs have been established fr rivers, lakes and transitinal and castal water bdies (see S.I. 272 f 2009 fr mre infrmatin). Mlybdate Reactive Phsphrus and Ammnium EQSs are tw f the key pllutin indicatrs that have been established fr river water bdies. Mlybdate Reactive Phsphrus is regarded as the key limiting nutrient that causes eutrphicatin in rivers. Sme f the ther surface water EQSs that have been established, such as Temperature, are nt applicable fr status assessments in grundwater. Additinal TVs may be required in the future, e.g. fr Nitrate (in relatin t transitinal and castal waters), Ttal Phsphrus (in relatin t lakes), sme metals (in relatin t the impact f mines n surface water) and parameters relating t the impact f pint surces n surface water bdies (e.g. metals, rganics etc.). 2.4 Saline (r Other) Intrusins test Schedule 6 (Part B) f the Grundwater Regulatins indicates that, as a minimum, Electrical Cnductivity TVs shuld be established where grundwater abstractins culd ptentially be causing saline intrusin. Other ptential indicatrs r saline (r ther) intrusins culd be Chlride r Sulphate. The latter parameter is mre indicative f deeper cnnate water intrusins, rather than castal intrusins. As these parameters ccur naturally in grundwater, the TV shuld be set at the Natural Backgrund Level fr these parameters, i.e. when cncentratins are abve the typical natural cncentratin, this will trigger further investigatin. The Natural Backgrund Levels fr these parameters have been established in Ireland (OCM, 2007). Threshld Values were established fr Chlride and Electrical Cnductivity, as these parameters are bth indicative f saline intrusin. A TV was nt established fr Sulphate because this parameter is nt causing grundwater bdies t be at risk f failing t meet a WFD bjective and mnitring data des nt suggest that any abstractins are causing ingress f deeper cnnate water. 2.5 Applicatin f Threshld Values Exceedance f a TV triggers further investigatin, i.e. an assessment f whether the pllutin is f sufficient magnitude t prevent the grundwater bdy achieving its status bjectives under the WFD and is therefre nt just causing a lcalised impact. This further investigatin is undertaken as part f the status assessments, fr example, t determine the pllutant lading frm grundwater t surface water ecsystems. It is nly if the cncentratin f pllutants exceeds the TV and any supprting evidence cnfirms the presence f an impact that cmprmises the achievement f WFD status bjectives, that the grundwater bdy is classified as Pr Status. 6

15 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends 2.6 Reprting f Threshld Values Threshld Values are listed in Schedule 5 f the Grundwater Regulatins. If the Envirnmental Prtectin Agency wishes t amend the list f TVs, it may d s by making recmmendatins t the Minister f the Envirnment. 7

16 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends 3 Chemical Status classificatin An assessment f grundwater bdy status is required t cmply with the Water Framewrk Directive (2000/60/EC) and the Grundwater Directive (2006/118/EC). In 2005, the WFD Article 5 Risk Assessments (Wrking Grup n Grundwater, 2005) were undertaken t identify grundwater bdies that were at risk f failing t meet bjectives f the Water Framewrk Directive (WFD). Status assessments are required fr all such grundwater bdies that were identified as being at risk. Status assessments are undertaken at the end f every six year river basin management planning cycle and are used t generate a snap sht that shws the impacts f abstractin and pllutin n grundwater. The risk assessments are carried ut at the beginning f the six year cycles. Whilst similar in nature, the gals f status assessments and nging risk assessments are different in that the risk assessments help determine the requirements fr future mnitring and investigatin, and help identify areas where future develpments culd impinge n the grundwater status bjectives f the WFD. Essentially, the risk assessments are assessments f whether bjectives f the WFD may nt be achieved in the future, whilst status assessments cnsider cmpliance with the WFD bjectives in the past. Additinally, status assessments cnsider widespread impact acrss a grundwater bdy. Therefre, a grundwater bdy can be at Gd Status, but there can still be an envirnmental risk, e.g. where the lcal impacts n grundwater quality are nt substantial enugh t impact n the status f the whle grundwater bdy. Hwever, where a grundwater bdy has been classified as being at Pr Status, this implies that there is als a risk f failing WFD bjectives in the future. Chemical classificatin f grundwater bdies is split int five tests (Figure 2). The tests are designed t assess whether the bjectives f the WFD are being met. The wrst case is reprted fr a grundwater bdy, s failure f ne r mre f the tests causes a grundwater bdy t be at Pr Status. Figure 2 Chemical Status Assessment Tests Due t the lack f infrmatin n trigger actin values fr GWDTEs, the GWDTE eclgical/chemical assessment culd nt be undertaken. This assessment will be undertaken in the 2 nd River Basin planning cycle. 8

17 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends 3.1 Test 1: Saline r Other Intrusins Test Key cncept: Status, and the presence f an intrusin f pr quality water int the grundwater bdy, is determined thrugh an assessment f trends in Electrical Cnductivity r ther indicatr substances. The test is designed t detect the presence f an intrusin that is induced by the abstractin f grundwater. Threshld Values: Set at the upper limit f the natural backgrund range fr key determinands. Threshld Values are nly used in cmbinatin with trend assessment(s). The cnditins fr gd quantitative status are nt met when: Threshld Values are exceeded and there is either a significant and sustained rising trend in ne r mre key determinands at relevant mnitring pints r there is an existing significant impact n a pint f abstractin as a cnsequence f an intrusin. (UKTAG, 2008a) Intrductin The Saline (r Other) Intrusins Test is intended t identify grundwater bdies where there is intrusin f pr quality water as a result f grundwater abstractin and this intrusin is leading t sustained upward trends in pllutant cncentratins r a significant impact n ne r mre grundwater abstractins (UKTAG, 2008a). Nte: the saline intrusin test mirrrs the test undertaken fr the Quantitative Status assessment Backgrund This test is undertaken t identify where grundwater quality is deterirating, r there have already been impacts n the quality f abstracted water, as a result f the intrusin f pr quality water int the grundwater bdy. The EU guidance (EC, 2009) and UKTAG guidance (UKTAG, 2008a) indicates that the intrusin must be caused by grundwater abstractin and must be sustained, i.e. temprary intrusins shuld nt be cnsidered. Therefre, the test fcuses n grundwater bdies where there is a risk that abstractin pressures may cause significant and sustained intrusins. Grundwater intrusin can ccur when the saline-freshwater interface in castal regins is drawn inland and upwards by abstractin. Grundwater abstractin can als lead t upward mvement (up cning) f pr quality deeper water, the leakage f saline surface waters t an underlying grundwater bdy, r drawing in f prer quality grundwater frm an adjacent aquifer. The EU and UKTAG guidance indicates that parameters in grundwater that are indicative f intrusin shuld be assessed, e.g. Electrical Cnductivity and Chlride. Where Electrical Cnductivity and Chlride cncentratins are abve Natural Backgrund Levels and there is either a significant upward trend 3 in cncentratin f that parameter, r there is already an impact n a pint f abstractin (e.g. where a water supply has been decmmissined due t saline intrusin), then the grundwater bdy will be at Pr Status. Otherwise it will be at Gd Status. The WFD indicates that cnfidence in the status assessment needs t be reprted. As per UKTAG guidance (UKTAG 2008a), a weight f evidence apprach has been adpted when assigning cnfidence, with High Cnfidence (HC) r Lw Cnfidence (LC) assigned t status assessments. Fr example, cnfidence is high where there is evidence f significant and 3 Further infrmatin n trend assessments is prvided in Sectin 5 f this reprt. 9

18 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends sustained upward trends and there is evidence f impact at a water supply. Cnfidence is lw when the evidence is less cmprehensive, e.g. n impact n water supplies r when mnitring is limited. Cnfidence des nt indicate hw clse the grundwater bdy status is t the status bundary. The linkages between Risk, Status and Cnfidence are summarised in Table 1. Table 1 Risk Assessment and Status fr the Saline Intrusin Test Risk assessment Abstractin in GWB Abstractin <20km frm the cast Cncentratin at Mnitring Pint >TV Elevated Cncentratin Caused by Abstractin Upward Trend in Cncentratin Status & Cnfidence N Gd-HC Yes N Gd-HC Yes Yes N - - Gd-HC Yes Yes Yes N - Gd-LC Yes Yes Yes Yes N Gd-LC Yes Yes Yes Yes Yes Pr-LC Yes Yes Yes Yes Yes Pr-HC* * Evidence f impacts f saline intrusin n nearby receptrs Infrmatin Required fr This Test The Saline (r Other) Intrusins Test assesses the presence f an intrusin f pr quality water int the grundwater bdy as a result f grundwater abstractin and is determined thrugh the identificatin f upward trends in Electrical Cnductivity and Chlride. The fllwing infrmatin was gathered fr this test. Threshld Values 4 Threshld Values were nly derived fr pllutants that are indicative f saline (r ther) intrusins. Electrical Cnductivity = 800 µs/cm Chlride = 24 mg/l. Grundwater Quality Data Fr each site, six years f Electrical Cnductivity and Chlride mnitring data ( ), frm the EPA s Natinal Grundwater Mnitring netwrk, were assessed t identify and calculate the maximum and average parameter cncentratins respectively. Ten years f mnitring data ( ), were used t assess trends in the parameter cncentratin. Mnitring Pints Assessed Grundwater bdies identified in the Article 5 Risk Assessment (Wrking Grup n Grundwater, 2005) as being At Risk frm saline intrusin: Mnitring lcatins were assessed in grundwater bdies that were at risk f failing t meet WFD bjectives in relatin t Saline Intrusin, as reprted in the Article 5 Risk Assessment. Castal lcatin: All mnitring lcatins, within 20 km f the cast r castal inlets, were assessed if the average Electrical Cnductivity and Chlride cncentratins exceeded the TV, r where the averages were lwer than the TV, but the maximum Electrical Cnductivity and Chlride cncentratins were significantly higher than the TV. Grundwater bdies with abstractin pressures: Mnitring lcatins were assessed in grundwater bdies that were at risk f failing t meet WFD bjectives because f unsustainable abstractins. 4 TVs determined as the upper limit f the Natural Backgrund Level (NBL) frm OCM,

19 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Methdlgy The steps undertaken as part f the Saline (r Other) Intrusin Test are utlined belw: Trend assessments were undertaken using the MAKESENS Mann-Kendall/Sen s nn-linear trend analysis mdel (Salmi et al, 2002). The mdel was used t identify statistically significant upward trends in Electrical Cnductivity and Chlride at mnitring pints. Sectin 5 f this reprt cntains mre detail n the trend analysis that was undertaken. The annual average cncentratins fr Electrical Cnductivity and Chlride were calculated at mnitring pints, ver a perid f ten years ( ), if the maximum Electrical cnductivity and Chlride cncentratins exceeded the TV during that perid. Annual averages have been calculated because the annual mnitring frequency has varied histrically and prir t 2007 the mnitring frequency was insufficient t distinguish seasnal variatins in parameter cncentratins. The trend assessment was nt undertaken when a mnitring pint had less than six years data during the ten-year perid because MAKESENS requires at least six years data t determine significant trends. Where trends culd be determined at individual mnitring pints, the statistical significance f the trend was determined using MAKESENS. Trends were identified as being nn-existent, upward r dwnward and the statistical significance f the trend was reprted as being 90%, 95%, 99% r 99.9% significant, r the trend was nt statistically significant. When assessing the impact f saline intrusin n grundwater, the presence f a statistically significant upward trend in bth Chlride and Electrical Cnductivity at any individual mnitring pint resulted in the grundwater bdy being classified at Pr Status. Mnitring lcatins with significant upward trends in Chlride, but nt in Cnductivity, r vice versa, remained at Gd Status, but are at risk f failing WFD bjectives in the future. These mnitring pints will be investigated further in the 2 nd River Basin Planning cycle. Infrmatin n the reasns fr water supplies being decmmissined was unavailable. Often water supplies are decmmissined when new water infrastructure prjects are being undertaken and it was nt clear if water quality prblems are a cntributry factr t supplies being decmmissined. The verall assessment apprach is summarised in Table 2. Table 2 Summary f criteria t determine status and cnfidence Status Cnfidence Example Criteria Gd Pr High Lw Lw High N exceedance f the TV levels, OR Exceedance f TV levels nt caused by abstractin Exceedance f TV levels but further investigatin has determined there are n sustained rising trends OR Pssible risk identified but n mnitring available Exceedance f TV levels caused by abstractin with sustained rising trends OR Exceedance f TV levels caused by abstractin AND impacted abstractin Exceedance f TV levels with sustained rising trends caused by abstractin AND The Intrusins have caused a significant impact n abstractin(s) Future Develpments The Natinal Grundwater Quality Mnitring netwrk has undergne significant develpment since 2007, with many new sites added t the netwrk. Summary statistics fr grundwater 11

20 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends quality are therefre based, in many cases, n limited data. There are currently insufficient data at many mnitring sites t carry ut rbust trend assessments. Lnger recrds f mnitring data will enable mre reliable trend assessments t be carried ut at all mnitring sites in the Natinal Grundwater Quality Mnitring netwrk in the 2 nd River Basin Planning cycle. 3.2 Test 2: Impact f Grundwater n Surface Water Eclgical/Chemical Status Test Key cncept: Status is determined thrugh a cmbinatin f surface water classificatin results and an assessment f chemical inputs frm grundwater bdies int surface water bdies. The surface water bdies can cmprise rivers, standing waters and transitinal waters. The test is designed t determine whether the cntributin frm grundwater quality t surface water quality, r any cnsequent impact n surface water eclgy, is sufficient t threaten the WFD bjectives fr these assciated water bdies. Threshld Values: Surface water quality standards adjusted by dilutin and, where apprpriate, attenuatin factrs. The cnditins fr gd chemical status are nt met when: An assciated surface water bdy des nt meet its bjectives, TVs are exceeded and grundwater cntributes at least 50% f the relevant surface water standard. (UKTAG, 2008a) Intrductin The Impact f Grundwater n Surface Water Eclgy and Chemistry Test is undertaken in thse grundwater bdies that are cntributing t a surface water bdy that is nt meeting its gd eclgical r chemical status bjectives because f diffuse pllutin pressures (UKTAG, 2008a) Backgrund Mst rivers and standing waters (lakes) derive their water frm bth surface water runff and grundwater discharge. The cntributin frm each cmpnent varies during the year and with aquifer type underlying the surface water bdy. In sme cases a large prprtin (50 100%) f the surface water can be made up f grundwater discharge and s the quality and quantity f grundwater discharging t surface water will have a big influence n surface water quality. This test is undertaken t identify surface water bdies that receive a significant prprtin f flw frm grundwater, and where pllutant cncentratins in grundwater are elevated and may cntribute significantly t thse assciated surface water bdies nt meeting their envirnmental bjectives, i.e. Gd Status r better. There are a number f elements that are assessed in determining verall surface water eclgical status, but the key element fr this test is chemistry. Fr surface water bdies t be at Gd Status r better there must be n significant impact n the eclgy r failures f the EQSs that have been established fr surface water. Where pllutant cncentratins in grundwater are elevated abve Natural Backgrund Levels and this plluted grundwater is cntributing significantly t a crrespnding surface water bdy failure; then the grundwater bdy will be at Pr Status. When making this assessment, cnsideratin is given t the dilutin effects in the surface water by estimating the cntributin f grundwater t the verall flw r vlume in the surface water. Cnsideratin is als given t the attenuatin (degradatin) ptential within the grundwater system, where this is knwn. 12

21 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Infrmatin Required fr This Test The Impact f Grundwater n Surface Water Eclgy and Chemistry Test assesses the ptential adverse impacts f grundwater pllutants t assciated surface water bdies (rivers, lakes and transitinal and castal waters) that are at less than Gd Status. The fllwing infrmatin was gathered fr this test. Threshld Values This test was undertaken fr parameters identified as causing a surface water bdy t be at less than Gd Status. The TVs were based n the parameter EQS fr the assciated surface water receptr. Mlybdate Reactive Phsphrus (as P) = 35 µg/l (based n River EQS) Ammnium (as N) = 65 µg/l (based n River EQS) Grundwater Quality Data Fr each site, six years f mnitring data ( ), frm the EPA s Natinal Grundwater Mnitring netwrk, were assessed t calculate the average parameter cncentratins. Grundwater Bdies Assessed The assessment was undertaken fr grundwater bdies assciated with surface water bdies designated as being at less than Gd Status due t diffuse pressures. The assessment was nt undertaken where pint surce discharges were the cause f the less than Gd Status designatin. Additinally, the assessment was nt undertaken where an verriding element (e.g. alien species r absence f a prtected area species, such as the Margaritifera pearl mussel) had caused the less than Gd Status designatin. Mnitring Pints Assessed Grundwater bdies identified in the Article 5 Risk Assessment (Wrking Grup n Grundwater, 2005) as being At Risk f having an adverse impact n assciated surface water bdies: Mnitring lcatins were assessed if they were lcated in grundwater bdies r grups f grundwater bdies that were At Risk f failing WFD bjectives in relatin t grundwater impacts n surface water eclgy/chemistry in the Article 5 Risk Assessment. Surface water bdies at less than Gd Status: Mnitring lcatins were assessed if they were lcated in grundwater bdies r grups f grundwater bdies assciated with surface water bdies designated as being at less than Gd Status due t diffuse pressures Methdlgy The steps taken t assess the impact f grundwater n the eclgical and chemical status f surface water bdies are detailed belw. (i) A cnceptual understanding f the grundwater cntributin t surface water bdies was develped fr each grundwater bdy. On behalf f the Shannn RBD, RPS Grup used the MIKE NAM mdel (DHI, 2004) t develp a cnceptual representatin f the hydrgelgical cycle fr typical settings in Ireland (RPS, 2009). In simple terms, the mdel separates rainfall int three different stres: verland flw, intermediate flw and deep grundwater flw. RPS (2009) have defined the cmpnents f the three stres as fllws: Overland flw: Surface runff, including flws in subsurface land drains; Intermediate flw: Interflw thrugh sils and subsils and shallw (tp f bedrck) grundwater; Deep grundwater flw: Grundwater flw beneath the water table that interacts with the surface water system. Mdelling was undertaken n surface water catchments natinwide and flw apprtined t the three cmpnents fr a ttal f 124 catchments (RPS, 2009). 13

22 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends The WFD defines grundwater as all water which is belw the surface f the grund in the saturatin zne and in direct cntact with the grund r subsil. In undertaking this test, the grundwater input cnsists f bth the deep grundwater flw and the shallw tp f the rck grundwater flw. The intermediate flw cmpnent was separated using hydrgelgical infrmatin n the aquifer, subsil and sil types within each mdelled catchment. The calculated shallw grundwater flw cmpnent was added t the deep grundwater flw cmpnent t give a ttal grundwater cmpnent in line with the WFD definitin. Mdelling in the karst dminated grundwater bdies was nt straightfrward because f difficulties apprtining/splitting the intermediate flw cmpnent, as grundwater can ften behave in a similar manner t surface water in karst aquifers and can be difficult t distinguish in a river hydrgraph. Therefre, a water balance apprach was devised t calculate the grundwater cntributin frm the karst dminated aquifer types (Rk and Lk aquifers 5 ). Five karst dminated catchments were selected fr a water balance assessment. It was assumed that the ttal vlume f water entering the catchment was equal t that leaving the catchment. Therefre, the karst cmpnent is the ttal vlume f water, less the surface water cmpnent and the grundwater cmpnent frm any ther aquifers types in the catchment (which had already been calculated using the mdel). The remaining vlume f water was assumed t be the Rk and Lk karst grundwater cmpnent. The annual average grundwater cntributin t surface water bdies was calculated fr each aquifer type acrss all the 124 mdelled catchments. The results are shwn in Table 3. An verall water balance was calculated fr each aquifer type in each grundwater bdy. This was calculated by dividing the ttal grundwater cmpnent fr each aquifer type by the ttal vlume f water entering the catchment, i.e. rainfall less evaptranspiratin. The grundwater cmpnents frm each aquifer type were summed and divided by the ttal vlume f water entering the catchment t give an verall grundwater cntributin t surface water bdies fr each grundwater bdy. Table 3 Estimated grundwater cntributins t surface water fr different aquifer types Aquifer type Annual Average Grundwater cntributin (%) Pl/Pu 21 Ll 27 Rf/Lm 65 Rk/Lk 74 Rg/Lg 90 (ii) Surface water bdies at less than Gd Status due t diffuse pressures were identified frm the Surface Water Classificatin results. A Gegraphical Infrmatin System (GIS) shapefile f the grundwater bdies was verlaid with the shapefile f surface water bdies at less than Gd Status and grundwater bdies ptentially cntributing t these surface water bdies were identified. (iii) The average cncentratin f Mlybdate Reactive Phsphrus (MRP) was calculated using six years f data fr mnitring pints within grundwater bdies (and assciated gruped grundwater bdies) ptentially cntributing t surface water bdies at less than Gd Status. 5 Infrmatin n the aquifer categries in Ireland can be btained frm the GSI website ( 14

23 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Whilst lcally elevated cncentratins f ammnium in grundwater culd impact n the eclgy and chemistry f a river, ammnium cncentratins at grundwater mnitring lcatins were generally lw and were nt cnsidered t have a reginal impact n surface water. Therefre, the test was nt undertaken any further fr ammnium. Nte: the WFD allws gruping f grundwater bdies, and use f data frm mnitring pints within gruped grundwater bdies, where the hydrgelgical settings and pressures are similar (EC, 2007). (iv) The test requires an assessment f grundwater inputs (lading) t determine if grundwater cntributes greater than 50% f the lading t the surface water bdy that wuld result in a breach f the surface water EQS, i.e. 35 µg/l fr MRP in rivers. Therefre the surface water lading relating t the MRP EQS was calculated using the ttal vlume f water entering the catchment x 35 µg/l. (v) The grundwater lading f MRP t rivers was calculated using the ttal vlume f grundwater entering the river system (ttal vlume f water entering the catchment x average grundwater cntributin acrss the grundwater bdy x average MRP cncentratin acrss the grundwater bdy). (vi) Grundwater bdies that cntributed greater than 50% f the lading that wuld result in a breach f the surface water bdy EQS were at Pr Status. Grundwater bdies that cntributed less than 50% f the lading were at Gd Status. Cnfidence was high where there was extensive mnitring in the grundwater bdy and/r gd supprting evidence f the grundwater cntributin. Where mnitring and/r the evidence were mre limited, cnfidence was lw. The verall assessment apprach is summarised in Table 4. Table 4 Summary f criteria t determine status and cnfidence Status Cnfidence Example Criteria Gd High Lw N surface water bdy at less than Gd Status OR Surface water bdy at less than Gd Status, but grundwater cncentratins < 50% f EQS and therefre Grundwater unable t cntribute > 50% f the lad t surface water. Surface water bdy at less than Gd Status, but further investigatin indicates grundwater lading < 50% f lading required t breach EQS OR Elevated pllutin cncentratins in grundwater unlikely t impact n the assciated surface water bdy, e.g. where MRP is likely t be bund r attenuated by the verlying subsil Pr Lw High Surface water bdy at less than Gd Status, and further investigatin indicates grundwater lading > 50% f lading required t breach EQS Surface water bdy at less than Gd Status, and further investigatin indicates grundwater lading > 50% f lading required t breach EQS AND Detailed site specific studies (e.g. grundwater tracing) identify and quantify direct cnnectin between grundwater and surface water Methdlgy Issues and Future Develpments The mnitring netwrk has undergne significant develpment ver the last six years with many new sites added t the netwrk. Summary statistics fr grundwater quality are therefre based, in many cases, n limited data. Lnger recrds f mnitring data will enable mre reliable trend assessments t be carried ut at all mnitring sites in the Natinal Grundwater Quality Mnitring netwrk in the 2 nd River Basin Planning cycle. 15

24 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends There is cnsiderable uncertainty abut the interactins between grundwater and surface water and the input frm grundwater t surface water, s the assessment is based n lgical, but relatively simple assumptins. Assessments f the cntributin f grundwater t lakes that are at less than Gd Status will be undertaken when mre data are gathered in the 2 nd River Basin Planning cycle. The grundwater cntributin t transitinal and castal waters will als be undertaken in the 2 nd River Basin Planning cycle. The study f grundwater/surface water interactins fr transitinal and castal waters are likely t be highly cmplex, invlving the study f the interactins between grundwater, rivers and estuaries, and will require the establishment f relevant surface water EQSs, which can then allw the derivatin f grundwater TVs. Whilst the whle grundwater bdy is assessed in this test, it is likely that measures and pllutin cntrls will fcus n the areas surrunding the surface water bdy r areas f extreme grundwater vulnerability, where pllutants such as MRP can readily get int grundwater as they bypass the sil and subsil where attenuatin can ccur. Onging research is required in this area t imprve ur understanding f grundwater/surface water interactins. 3.3 Test 3: Grundwater Dependent Terrestrial Ecsystems Chemical Assessment Test Key cncept: Status is determined thrugh a cmbinatin f GWDTE assessments t determine eclgical damage and an assessment f chemical inputs frm grundwater bdies int GWDTEs. The test is designed t determine whether the cntributin frm grundwater quality t GWDTEs and cnsequent impact n GWDTE eclgy is sufficient t threaten the WFD bjectives fr these assciated GWDTEs. Threshld Values: Wetland quality standards r actin values adjusted by dilutin and, where apprpriate, attenuatin factrs. The cnditins fr gd chemical status are nt met when: The eclgy f an assciated GWDTE is damaged due t the chemical cntributin frm the grundwater bdy, TVs are exceeded and grundwater lading is sufficient t cause a breach f the relevant GWDTE quality standard Intrductin This sectin describes the methd used t assess the chemical status f grundwater bdies with respect t significant damage t GWDTEs, i.e. wetlands. The test is nly applied t wetlands/gwdtes that have been frmally identified as prtected areas under Regulatin 8 f S.I. 722 f Backgrund GWDTEs are defined here as wetlands where habitats and species are dependent n grundwater t maintain the envirnmental supprting cnditins that are required t sustain the habitat and/r species. This test cnsiders the cncentratins f nutrients (primarily phsphates, nitrates and ammnium) in grundwater bdies and the ptential fr these t affect grundwater dependent wetlands, such that the grundwater chemistry causes significant damage t the wetland eclgy. 16

25 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Where significant damage as a result f chemical pressures is cnfirmed, the grundwater bdy is at Pr Status. T assess the impact there is a need t determine whether, and if s hw, chemical pressures in the grundwater bdy affect the quality f the water supprting the wetland and als whether the change in water quality (if any) affects the grundwater dependent eclgical features (flra and fauna). The Natinal Parks and Wildlife Service (NPWS) prduced a list f Sites f Special Scientific Interest (SSSIs) which they cnsider t be GWDTEs fr the Article 5 Risk Assessment in The Article 5 Risk Assessment (Wrking Grup n Grundwater, 2005) identified GWDTEs where the eclgy was ptentially damaged and therefre may have been impacted by grundwater abstractin r pllutin. Hwever, generally the cause f the damage was unclear, and may have been caused by quantitative r chemical cntributins frm grundwater, r bth. A small number f wetland studies have been undertaken since the Article 5 Risk Assessment, but these have been site specific. Mre generic attempts t classify the requirements f GWTDEs, in terms f grundwater chemistry (mainly nutrients) and the quantity f grundwater (bth flw and levels) have been unsuccessful, and clearly highlight the cmplexity f wetlands as they may be extremely sensitive t any fluctuatins t the habitat s supprting cnditins. A number f prjects were established t help determine the chemical (and quantitative) requirements f the wetlands, e.g. fr Turlughs. The findings f these prjects will be used t derive actin values fr generic wetland types, which in turn will enable the determinatin f TVs fr grundwater bdies. Until these prjects are cmplete, it will nt be pssible t undertake chemical status assessments f the grundwater bdies that are assciated with GWDTEs. Initial wrk frm the GWDTE prjects has resulted in imprved GWDTE bundaries (within the SSSIs) and has enabled NPWS t update the GWDTE list and imprve upn the initial Article 5 Risk Assessment Methdlgy fr Future Assessments Future assessments f GWDTEs will require cnfirmatin that the eclgy f the wetland is damaged (r at risk f being damaged) and that this damage is being caused by change in the reginal grundwater cntributins t the wetland. This grundwater cntributin t the wetlands culd be quantitative (flw r levels) r chemical (pllutants), r bth. Where pllutants are cntributing t the eclgical damage in the wetland, chemical standards (r actin values) will need t be established fr the wetland, and in turn TVs will be established fr the grundwater bdy. The develpment f TVs will take accunt f natural backgrund cncentratins fr a particular pllutant. If pllutants exceed these TVs at mnitring pints in the Natinal Grundwater Mnitring netwrk that are lcated in the assciated grundwater bdy, then further investigatin will be undertaken t determine if grundwater is cntributing t eclgical damage in the assciated GWDTE. Once TVs have been established fr a GWDTE, the grundwater lading t the wetland will be calculated in a similar manner t the surface water eclgical/chemical status test. Grundwater inputs (lading) t the GWDTE will be calculated fr the parameters f cncern. If the lading frm grundwater exceeds the envirnmental supprting cnditin f the GWDTE, then the grundwater bdy will be at Pr Status. The verall assessment apprach is summarised in Table 5. 17

26 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Future Develpments There is cnsiderable uncertainty with this test and there are a number f research prjects that aim t address these issues. Currently there is little mnitring f water quality n GWDTE sites and therefre there are few measurable data n the nutrient envirnmental supprting cnditins requirements f the wetland flra and fauna r f the effects f elevated nutrients n the flra and fauna. Table 5 Summary f criteria t determine status and cnfidence Status Cnfidence Example Criteria Gd Pr High Lw Lw High N eclgical damage t GWDTE OR Eclgy f GWDTE damaged, but grundwater cncentratins < wetland trigger actin value/cncentratin Eclgy f GWDTE damaged, but further investigatin indicates grundwater lading < lading required t breach wetland trigger actin value/cncentratin Eclgy f GWDTE damaged, and further investigatin indicates grundwater lading > lading required t breach wetland trigger actin value/cncentratin Eclgy f GWDTE damaged, and further investigatin indicates grundwater lading > lading required t breach wetland trigger actin value/cncentratin AND Detailed site-specific studies identify and quantify direct cnnectin between grundwater and GWDTE. There is als a need t research the level f attenuatin f nutrients between the grundwater bdy and discharge n site, and infrmatin is required n the hydraulic linkages between grundwater and the wetland. In future there is a need t extend the scientific knwledge f grundwater dependency f the wetland eclgy. Critically, infrmatin is required n the chemical, flw and water level requirements f the eclgy. This test will be undertaken in the 2 nd River Basin Planning cycle. 3.4 Test 4: Drinking Water Prtected Area Test Key cncept: Gd chemical status requires an assessment, at the pint f abstractin fr water intended fr human cnsumptin, f whether there is deteriratin in grundwater quality due t anthrpgenic influences that culd lead t an increase in purificatin treatment. Nte: the stated aim f the Drinking Water Prtected Area (DWPA) bjective in the WFD is t prvide the necessary prtectin t avid deteriratin in water quality in rder t reduce the need fr purificatin treatment. This has been interpreted as a minimum requirement t prevent deteriratin in grundwater quality at the pint f abstractin fr drinking water supply. Threshld Values: An apprpriate percentage f Drinking Water Standards r any ther requirement t ensure that drinking water is free frm cntaminatin that culd cnstitute a danger t human health (in accrdance with the Drinking Water Directive). The cnditins fr gd chemical status are nt met when: There is a significant and sustained rising trend in ne r mre key determinands at the pint f abstractin and TVs are exceeded. (UKTAG, 2008a) 18

27 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Intrductin This sectin describes the steps that were taken in classifying the chemical status f grundwater bdies fr the Drinking Water Prtected Area Test. The test identifies grundwater bdies which are currently failing t meet the DWPA bjectives defined in Article 7 f the Water Framewrk Directive and thse that are risk f ding s in the future. In Ireland, all grundwater bdies are DWPAs and s this test applies t all grundwater bdies Backgrund The DWPA bjectives f the WFD require that grundwater is prtected t avid deteriratin in water quality that wuld lead t an increased level f treatment at pints f abstractin. DWPAs are grundwater bdies that are used fr the abstractin f mre than 50 m 3 /day f water intended fr human cnsumptin, r fr supplying mre than 50 peple. Because f these lw threshlds, all grundwater bdies have been designated as DWPAs in Ireland. This test is undertaken t identify where there is likely t be a need fr water purificatin treatment in the future, r an increase in the level f existing treatment, as a result f deterirating water quality that has been caused by pllutin. The test requires an assessment f the cncentratins f pllutants in grundwater and hw they are changing ver time at a representative selectin f drinking water abstractins. Trend assessments were used t identify current exceedances f drinking water standards and t prject pllutant cncentratins int the future, in rder t identify exceedances f drinking water standards that were likely t ccur in the next tw River Basin Management cycles (i.e. by 2021). It is at these surces (and assciated grundwater bdies) that there may be a need fr increased treatment f raw water in the future. Grundwater bdies were at Pr Status where there was evidence that there was an existing exceedance f a TV and where there was a significant upward trend in the cncentratins f the relevant pllutant(s). Where there was evidence that cncentratins were less than the TV, but there were significant and sustained upward trends in the cncentratins f the relevant pllutant(s) and the cncentratins were prjected t exceed the TV by 2021, the grundwater bdy was at Gd Status, but was at risk f failing t meet its WFD bjectives in future. The relatively lw frequency f sampling at mnitring sites means that exceedances f drinking water standards may nt be easily detected in the natinal mnitring prgramme. Therefre, the nly reliable statistic that can be used effectively fr assessment is the mean cncentratin. Hwever, because the drinking water standards relate t maximum admissible cncentratins, the TVs have t be set at a lwer value than the drinking water standard, t allw cmparisn f mean cncentratins. The use f this TV is equivalent t cmparing the maximum cncentratin with the drinking water standard (see Sectin 2 n Threshld Values fr mre infrmatin). Where there was evidence f exceedances and significant upward trends at a mnitring pint and lcal authrity data shwed similar cncentratins, cnfidence in the assessment was high. Where limited r n lcal authrity data existed, r there was cnflict between the datasets, then cnfidence was lw. Cnfidence des nt indicate hw clse the grundwater bdy status is t the Gd/Pr status bundary Infrmatin Required fr This Test The Drinking Water Prtected Area Test assesses trends in the cncentratin f pllutants at representative drinking water surces. This test is nly undertaken fr pllutants that have a prescribed standard relating t the human use f water, i.e. drinking water standard. Mst water supplies already have chlrinatin in place, s this frges the need fr micrbilgical assessment, althugh viruses and prtza such as cryptspridium, are mre difficult t assess. If additinal treatment is required t reduce the impacts f pllutin (including increased chlrinatin), then the mnitring pint, and therefre the assciated grundwater bdy, default t Pr Status. The fllwing infrmatin was gathered fr this test. 19

28 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Threshld Values Threshld Values were nly derived fr pllutants that are placing a grundwater bdy at risk f failing WFD bjectives and where these pllutants have a prescribed drinking water standard. Threshld Values were derived fr the fllwing pllutants: Nitrate (as NO 3 ) = 37.5 mg/l Ammnium (as N) = 175 µg/l Electrical Cnductivity = 1,875 µs/cm Nitrite (as NO 2 ) = 375 µg/l Chlride = mg/l Sulphate = mg/l Sdium = 150 mg/l Brn = 750 µg/l Individual Pesticides = µg/l Ttal Pesticides = µg/l Trend Assessments Trend assessments were undertaken using the MAKESENS Mann-Kendall/Sen s nn-linear trend analysis mdel (Salmi et al, 2002). Further infrmatin n the trend assessment is prvided in Sectin 5 f this reprt. The MAKESENS mdel reprts the significance fr the trend assessment, i.e. trend nt significant (<90% significance) r the trend is 90%, 95%, 99%, r 99.9% significant. Grundwater Quality Data Ten years f mnitring data ( ) frm the EPA s Natinal Grundwater Mnitring netwrk, were used t identify trends fr this test. The lcal authrities supplied supplemental water quality data fr drinking water abstractins >100 m 3 /d. These data were used as part f the risk assessment and t imprve cnfidence in the assessment, but were nt used t determine status because the lcal authrity data is sampled after treatment has taken place. Mnitring Pints Assessed Drinking Water Abstractins. All mnitring lcatins in the EPA s Natinal Grundwater Mnitring netwrk that are als used fr drinking water supply Methdlgy The steps taken in carrying ut the Drinking Water Prtected Area test are utlined belw. (i) Grundwater mnitring data were cmplied fr representative mnitring pints in the EPA s Natinal Grundwater Mnitring netwrk that are als drinking water abstractins. (ii) The maximum and annual average cncentratins were calculated fr a 10 year reprting perid ( ) at these mnitring sites. (iii) Initially the data were screened at these mnitring sites n further assessment was undertaken where the average cncentratin was less than the screening value (half the drinking water standard) r where there were n measured individual cncentratins abve the TV. These sites default t Gd Status (with high cnfidence). (iv) Where elevated cncentratins fr a determinand were detected at mnitring pints, checks were made t determine if the natural backgrund cncentratins were elevated in the aquifers being mnitred, e.g. fr irn and manganese. If the natural backgrund levels were higher than mnitred cncentratins, these sites default t Gd Status (high cnfidence). (v) Further assessment was required at the remaining sites: The EU guidance (EC, 2009) defines the cncentratin in 2007 as the baseline cnditin fr future trend assessments. At each site with elevated determinand 20

29 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends cncentratins, the mean cncentratin was calculated (fr the relevant pllutants) fr the year 2007; Where the mean cncentratin fr a pllutant was greater than the TV in 2007, further assessments were undertaken t determine if there were significant upward trends in the pllutant cncentratin. Where the mean cncentratin fr pllutants was less than the TV in 2007, the sites default t Gd Status, but trends were assessed t determine if the site was at risk f failing WFD bjectives in the future. Nte: increases in determinand cncentratin beynd the baseline cnditin are allwable, as lng as they d nt exceed the TV r bring abut the need fr an increased level f purificatin / treatment at the water supply. Trend assessments were undertaken at individual mnitring sites t determine if there are statistically significant upward trends in pllutants: T undertake the statistical assessment, a minimum f 80% real data in the dataset was required, i.e. there must be n mre than 20% LOD/LOQ data. Statistically significant trends culd nt be calculated fr datasets with less than six years data because the MAKESENS mdel cannt detect significant trends with less than six years f data. The trend significance was calculated using the MAKESENS mdel. Where the baseline cnditin cncentratin was abve the TV, but trends were dwnward r were nt statistically significant, r assessments culd nt be undertaken because f a lack f data, then the mnitring sites default t Gd Status (with lw cnfidence). Where the baseline cnditin cncentratin was belw the TV, but assessments culd nt be undertaken because f a lack f data, then the mnitring sites default t Gd Status (with lw cnfidence). Where the baseline cnditin cncentratin was belw the TV, and trends were dwnward r were nt statistically significant, the mnitring sites default t Gd Status (with high cnfidence). Where statistically significant upward trends were detected at mnitring sites, the trend was prjected frward until 2021 (using the MAKESENS mdel), t determine if the trend will be envirnmentally significant in the future, i.e. will breach a TV befre Where there was a significant trend and the cncentratin already exceeded the TV, these sites (and assciated grundwater bdies) were at Pr Status (high cnfidence) in the 2009 reprting perid. As the TV has already been exceeded, the starting pint (year) fr trend reversal is Where there was a significant trend and the baseline cnditin cncentratin was belw the TV, but was prjected t exceed the TV by 2021, these sites (and assciated grundwater bdies) were at Gd Status (lw cnfidence), but were at risk f failing t meet the WFD bjectives in the future 6. In the case f the previus pint, the year when 75% f the TV cncentratin is breached was identified frm the MAKESENS mdel. This is the starting pint (year) that trend reversal shuld begin, i.e. measures shuld be intrduced prir t this year. Crsschecks in the assessment were undertaken using lcal authrity drinking water returns: Where the annual average cncentratin fr a determinand was similar t that calculated abve, then there was high cnfidence in the status assessment. 6 Nte that this apprach is slightly different t that undertaken by the UK. In the UK, when the baseline cnditin cncentratin was belw the TV, but there was a significant upward trend that was prjected t exceed the TV by 2012, these sites (and assciated grundwater bdies) were at Pr Status. 21

30 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Where the lcal authrity data prvided cnflicting evidence r did nt exist, then the initial status determinatin remained, but with lw cnfidence. The verall assessment apprach is summarised in Table 6. Table 6 Summary f criteria t determine status and cnfidence Statistically significant trend in data Mean cncentratin currently belw TV Mean cncentratin currently abve TV Dwn Gd (als nt at risk) Gd (at risk) N trend Gd (als nt at risk) Gd (at risk) Up Gd (at risk where predicted cncentratin in 2021 > TV, therwise nt at risk) Pr (at risk) Future Develpments The mnitring netwrk has undergne significant develpment ver the last six years with many new sites added t the netwrk. In many cases data recrds are nt lng enugh t carry ut rbust trend assessment. Prviding that mnitring is cntinued, better data will be available fr trend assessment in the future. Additinal infrmatin is required n the current level f treatment at water supplies. Blending f water frm multiple abstractin pints is cmmnly used t maintain the quality f water supplied frm drinking water schemes. Additinal water supply surces and abstractin pints are ften intrduced t maintain the status qu in water quality, but this wuld be perceived as additinal treatment under WFD and therefre the grundwater bdy wuld be at Pr Status. Therefre, infrmatin n the actual abstractins, blending and treatment regimes are required t ensure cmpliance with this WFD bjective in the future. 3.5 Test 5: General Chemical Assessment Test Key cncept: Status is determined thrugh an assessment f the areal extent f a grundwater bdy exceeding a TV fr a pllutant. It is nly cnducted fr determinands fr which: an EU prescribed standard is set; r the risk characterisatin prcess has indicated that pllutants may cause significant impairment f human uses f grundwater. Threshld Values: An apprpriate percentage f the EU prescribed standards fr nitrates and pesticides r a use-related standard that is apprpriate fr existing r planned use f the grundwater bdy. The cnditins fr gd chemical status are nt met when: Threshld Values are exceeded at individual mnitring pints, and a representative aggregatin f the mnitring data at the grundwater bdy scale indicates that there is a significant envirnmental risk r a significant impairment f human uses f the grundwater bdy. (UKTAG, 2008a) Intrductin The General Chemical Assessment Test identifies grundwater bdies where widespread deteriratin in quality has, r will, cmprmise strategic use f grundwater. The status f the grundwater bdy is Pr if there is a widespread exceedance f relevant grundwater TVs r quality standards (UKTAG, 2008a) 22

31 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Backgrund The General Chemical Assessment Test is undertaken where there is deteriratin in grundwater quality at a scale that may cmprmise strategic use f grundwater fr existing r planned, human cnsumptin and/r ther ptential purpses. The test is nt intended t identify lcal pllutin impacts. This test lks at cncentratins f nitrate, pesticides and ther pllutants in grundwater that put grundwater bdies at risk f failing t meet WFD bjectives. Where TVs are exceeded at individual mnitring pints, an aggregated average pllutant cncentratin acrss the grundwater bdy (r grup f bdies) is calculated. Where the pllutin f grundwater is cnfirmed as being widespread, i.e. widespread exceedance f the TV, the grundwater bdies are at Pr Status fr this test, therwise they are at Gd Status. This test assesses the impact f widespread diffuse pressures n grundwater quality, and includes an assessment f pllutants frm significant pint surces, e.g. mining activities and cntaminated land Infrmatin Required fr This Test The General Chemical Assessment Test assesses whether there is a widespread exceedance f relevant grundwater quality standards r grundwater TVs. This test is nly undertaken fr determinands that are applicable t human uses f grundwater. The fllwing infrmatin was gathered fr this test. Pressures As part f the initial grundwater characterisatin, grundwater bdies were delineated alng hydrgelgical bundaries. In additin, grundwater bdies were delineated when activities, such as cntaminated land r mining were cnsidered t be having a widespread impact n grundwater quality. The Article 5 Risk Assessment (Wrking Grup n Grundwater, 2005) identified grundwater bdies that were at risk f failing t meet WFD bjectives. Threshld Values Threshld Values were nly derived fr pllutants that are placing a grundwater bdy at risk f failing t meet WFD bjectives and where these pllutants have a prescribed standard relating t the human use f water, i.e. drinking water standard. Threshld Values were derived fr the fllwing pllutants: Nitrate (as NO 3 ) = 37.5 mg/l Ammnium (as N) = 175 µg/l Electrical Cnductivity = 1,875 µs/cm Nitrite (as NO 2 ) = 375 µg/l Chlride = mg/l Sulphate = mg/l Sdium = 150 mg/l Brn = 750 µg/l Individual Pesticides = µg/l Ttal Pesticides = µg/l Chrmium = 37.5 µg/l Arsenic = 7.5 µg/l Lead = µg/l Nickel = 15 µg/l Mercury = 0.75 µg/l Cadmium = 3.75 µg/l Cpper = 1500 µg/l Aluminium = 150 µg/l Cyanide = 37.5 µg/l 1,2-Dichlrethane = 2.25 µg/l 23

32 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Vinyl Chlride = µg/l Ttal Tetrachlrethene & Trichlrethene 7.5 µg/l Benzene = 0.75 µg/l Benz(alpha)pyrene = 7.5 ng/l Ttal Plycyclic Armatic Hydrcarbns = µg/l Ttal Trihalmethanes = 75 µg/l Grundwater Quality Data Fr each site, six years f mnitring data ( ), frm the EPA s Natinal Grundwater Mnitring netwrk, were assessed t calculate the average parameter cncentratins. Pint Surce Data Mines: Grundwater quality data were gathered fr histric mines by the Gelgical Survey f Ireland/Explratin and Mining Divisin. Data included samples taken frm wells and mine adits, as well as leach test data frm mine waste areas and mine wrkings. The data were cllectively assessed t determine the average cncentratins f different metals acrss the wrked mine area. Further infrmatin is available in the Classificatin f Grundwater Bdies: General Chemical Test fr Clsed Mines (GSI, 2009). Cntaminated Land: Grundwater quality data were gathered fr IPPC and Waste sites where there has been histrical cntaminatin at the site lcatin. The annual envirnmental reprts fr IPPC and waste sites were cnsulted t imprve cnceptual understanding f grundwater flw and identify the lcatins f grundwater mnitring and levels f cntaminatin. Urban Areas: Grundwater quality data were gathered fr mnitring sites in urban areas acrss Ireland. This included data gathered frm public water supplies, industrial supplies, private abstractins and mnitring at IPPC and waste sites. Further infrmatin is available in the Urban Pressures Further Characterisatin study (CDM, 2008). Histrical Landfill: The infrmatin required t assess the impact f ld dumps n grundwater quality was insufficient t undertake an assessment. Discharge t Grundwater: The infrmatin required t assess the impact f discharges t grundwater n grundwater quality was insufficient t undertake an assessment Methdlgy Data frm the EPA s Natinal Grundwater Mnitring netwrk were used t assess whether there was a widespread impact n grundwater quality acrss grundwater bdies. The steps taken in carrying ut the General Chemical Assessment Test fr a grundwater bdy are detailed belw: (i) Grundwater mnitring data were cmpiled fr individual mnitring pints in the EPA s Natinal Grundwater Mnitring netwrk. (ii) In accrdance with EU Guidance (EC, 2007), grundwater bdies with similar hydrgelgies and pressures were gruped, and mnitring data frm the grup f mnitring pints within these grundwater bdies were used t assess grundwater quality. (iii) Where a TV was exceeded at an individual mnitring pint, an aggregated average pllutant cncentratin was calculated acrss the grundwater bdy grup fr the relevant pllutant. This quantified the extent f the prblem and whether there are any significant risks t the envirnment r impairment t human use. The six year average cncentratin fr the relevant pllutant was calculated at all mnitring pints in the grundwater bdy grup. Data frm all mnitring pints in the grundwater bdy grup were aggregated and the six year average cncentratin fr the relevant pllutant was calculated fr the grundwater bdy grup. 24

33 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends Fr sme grundwater bdy grups, a weighting factr was applied t certain mnitring pints in the grup t ensure that the mnitring data was representative f the grundwater quality acrss the grundwater bdies. Hwever, fr mst grundwater bdy grups, a weighting factr was nt required and the aggregatin was an un-weighted average frm the mnitring pints. (iv) An assessment was undertaken t determine if the elevated cncentratins were due t natural cnditins. Where the natural backgrund cncentratins fr the relevant pllutant were higher than the average cncentratin, the grup f bdies defaulted t Gd Status. (v) Fr the remaining pllutants, where the aggregated cncentratin was higher than the TV, all grundwater bdies in the grup were at Pr Status. (vi) High cnfidence was assigned where there was gd evidence f widespread impacts n human uses f grundwater, i.e. cncentratins abve the Drinking Water Standard. Further assessment was undertaken t determine if pllutin, frm activities such as cntaminated land r mining, was impacting n the status f grundwater bdies. The assessment was based n a cnceptual understanding f cntaminant transprt frm the cntaminated areas f the grundwater bdy, taking int accunt variatin in grundwater quality acrss the whle grundwater bdy. (i) Grundwater mnitring data were cmpiled fr areas cntaminated by pint surces activities. (ii) Supprting evidence f impact n receptrs was als gathered, i.e. any evidence f impact n drinking water abstractins, surface watercurses r wetlands. (iii) Fr each f the assessed grundwater bdies, there were mnitring sites that were representative f the cntaminant plume and thse that were representative f the remaining areas f the grundwater bdy. The mean cncentratins f hazardus cntaminants in remaining areas f the grundwater bdy were assumed t be zer, unless there were additinal cntaminated land sites within the grundwater bdy (e.g. in urban areas); The mean cncentratin f the nn-hazardus cntaminants in the remainder f the grundwater bdy shuld reflect the mean cncentratins in the grundwater bdy that surrunds the cntaminated land site, i.e. the average cncentratins calculated frm the EPA s Natinal Grundwater Mnitring netwrk. (iv) An assessment was undertaken t determine whether the extent f the pllutin was significant enugh t impact n status f the grundwater bdy. An area-weighted aggregatin f the cntaminant plume was calculated using mnitring data frm the site (see belw). Area-Weighted Average Cncentratin = ((Plluted area x Estimated average cncentratin in plluted area) + (Area f the remainder f the GWB x Estimated average cncentratin in this area)) / Ttal GWB area If the area-weighted average cncentratin was higher than the TV, the grundwater bdy was at Pr Status. High cnfidence was assigned where there is gd evidence f widespread impacts f pllutin, i.e. recrded impacts n drinking water abstractins, surface watercurses r wetlands. (v) Crsschecks were made with EPA site inspectrs t ascertain if remediatin prgrammes were in place at the cntaminated sites and whether the remediatin wuld bring abut 25

34 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends marked imprvement by If remediatin was cmpleted r was nging, and was likely t cause a significant reductin in the cntaminant plume cncentratins and the extent f the plume, the grundwater bdy defaulted t Gd Status, but with lw cnfidence. (vi) Crsschecks were made with the GSI/EMD t determine if the elevated metal cncentratins at mines were natural r if they had been caused by the mining activities. If the cncentratins were nt directly caused by the mining activity, i.e. were cnsidered t be naturally elevated, the grundwater bdy defaulted t Gd Status, but with lw cnfidence. The verall assessment apprach is summarised in Table 7. Table 7 Summary f criteria t determine status and cnfidence Status Cnfidence Example Criteria Gd Pr High Lw Lw High N individual site cncentratins higher than TV(s) Aggregated pllutant cncentratin < TV(s), but individual site cncentratins higher than TV(s) OR Aggregated pllutant cncentratin > TV(s), but aggregated pllutant cncentratins lwer than Natural Backgrund cncentratins OR Evidence f remediatin causing a significant reductin in pllutant cncentratins Aggregated pllutant cncentratin > TV(s) Aggregated pllutant cncentratin > TV(s) and individual sample cncentratins greater than Drinking Water Standard OR Aggregated pllutant cncentratin > TV(s) and evidence f impact n drinking water abstractins, surface watercurses r wetlands Future Develpments The mnitring netwrk has undergne significant develpment ver the last six years with many new sites added t the netwrk. In many cases, summary statistics fr grundwater quality are therefre based n limited data. Future runds f classificatin will have mre rbust data and better summary infrmatin. Detailed infrmatin n the impacts f landfill and discharge t grundwater is required in the 2 nd River Basin Planning cycle t determine their impact n the status f grundwater bdies. Further detailed studies f cntaminated land sites and mines are required in the 2 nd River Basin Planning cycle. In particular, detailed infrmatin n the extent f cntaminant plumes is required. 26

35 Methdlgy fr Establishing Threshld Values, and the Assessment f Grundwater Status and Pllutin Trends 4 Quantitative Status An assessment f grundwater bdy status is required t cmply with the Water Framewrk Directive (2000/60/EC) and the Grundwater Directive (2006/118/EC). In 2005, the WFD Article 5 Risk Assessments (Wrking Grup n Grundwater, 2005) were undertaken t identify grundwater bdies that were at risk f failing t meet the bjectives f the WFD. Status assessments are required fr all grundwater bdies that were identified as being At Risk. Status assessments are undertaken nce every six years, at the end f the river basin management planning cycles, and are used t generate a snap sht that shws the impacts f grundwater abstractin and pllutin n grundwater. The risk assessments are carried ut at the beginning f the six year cycles. Whilst similar in nature, the gals f status assessments and nging risk assessments are different in that the risk assessments help determine the requirements fr future mnitring and investigatin, and help identify areas where future develpments culd impinge n the grundwater status bjectives f the WFD. Essentially, the risk assessments are assessments f where bjectives f the WFD may nt be achieved in the future, whilst status assessments cnsider cmpliance with the WFD bjectives in the past. Additinally, status assessments cnsider widespread impact acrss a grundwater bdy. Therefre, a grundwater bdy can be at Gd Status, but there can still be an envirnmental risk, e.g. a lcal reductin in water levels in clse prximity t an abstractin can impact n neighburing water supplies, but are nt substantial enugh t impact n the status f the whle grundwater bdy. Hwever, where a grundwater bdy has been classified as being at Pr Status, this implies that there is als a risk f failing t meet WFD bjectives in the future. Quantitative classificatin f grundwater bdies is split int fur tests (see Figure 3). The tests are designed t assess whether the bjectives f the WFD are being met. The wrst case is reprted fr a grundwater bdy, s failure f ne r mre f the tests causes a grundwater bdy t be at Pr Status. Figure 3 Quantitative Status Assessment Tests Due t a lack f infrmatin n eclgical flw standards fr surface water bdies, the surface water eclgical/quantitative assessment culd nt be undertaken. This assessment will be undertaken in the 2 nd River Basin Planning cycle. 27