Hydro G Final report - Kildare.ie

HYDROLOGICAL REPORT 

FOR LEIXLIP SPA 

CO. KILDARE 

FINAL REPORT 

PREPARED FOR: 

KILDARE COUNTY COUNCIL 

JULY 2008

Unit 13, Galway Technology Centre, Mervue Business Park, Galway. tel: 091 704848, fax: 091 755635 

Project No.: 07_136 

Report Title: Hydrological Report for Leixlip Spa, Co. Kildare 

Report Status: Final Report 

Date: 21/07/2008 

Prepared by: ___________________________ 

Anna Kuczynska 

Approved by: ___________________________ 

Dr. Pamela Bartley 

NOTES: 

All information supplied by the Client, the Client's staff and professional advisers, local authorities, other statutory 

bodies, investigation agencies and other stated sources is accepted as being correct. 

All data and methods of analysis presented are, to the best of our knowledge, valid at the time of report 

generation. 

Areas presented, off site distances and elevations are normally computed from Ordnance Survey maps and not 

from physical surveys. They are approximate unless otherwise stated. 

Project No.: 07_136 Leixlip Spa 

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Hydro-G FINAL REPORT 

PROJECT TEAM 

Dr. Pamela Bartley (B.Eng, M.Sc., Ph.D, MIEI) is a consultant civil engineer with over ten years 

field experience in hydrogeological investigations and site instrumentation. Project areas include 

groundwater investigations, local authority licensing of treated wastewater discharges, water 

resource assessment, subsoil hydrology, assessment of groundwater vulnerability, nutrient impact 

accounting, environmental risk analysis and design of stormwater, wastewater and constructed 

wetland systems. Pamela is a FETAC Certified Site Assessor and assists on the EPA/FAS led Site 

Suitability Course. She is a member of the committee of the International Association of 

Hydrogeologists (Irish Branch) and currently holds responsibility for the organisation and 

management of the National Irish Annual Groundwater Conference. She completed her doctoral 

research (2003) at Trinity College, Dublin in conjunction with Teagasc and the EPA under National 

Development Plan funded research concerning groundwater vulnerability and European Directives 

concerning Agriculture. In conjunction with Paul Johnston of TCD, Pamela completed an assessment 

of Chromium levels in Irish Aquifers in the midlands for the EPA. Subsequently, Pamela completed 

projects concerning design and site suitability of constructed wetlands for treatment of wastewaters 

in conjunction with partners from TCD, GSI, EPA, NPWS and Departments of Environment and 

Agriculture. She has held lecturing posts at third level Irish academic institutions (WIT and CIT) and 

demonstrated at TCD. 

Anna Kuczynska (B.Eng, M.Sc.,IEMA) is a consultant environmental engineer with hydrological, 

hydrogeological and hydro-ecological expertise. Project areas include environmental impact 

assessment, risk analysis, groundwater and surface water investigations and sustainability 

assessments for sensitive ecological areas of groundwater dependent terrestrial ecosystems (GDTE). 

Since she joined Hydro-G (July 2007), she has taken responsibility for projects including hydrological 

and hydrogeological assessments. Before that, she worked in WS Atkins, where she was involved in 

a number of projects assessing impacts on soil and water environments in relation to road schemes 

and private developments and also undertook an assessment of the hydrological regime along the 

Tolka River valley. Her expertise in hydro-ecology was gained at Trinity College Dublin, where she 

completed her doctoral research characterising the hydrology of Pollardstown Fen (Co. Kildare) with 

an emphasis on protection of the habitat of the rare species of molluscs Vertigo geyeri. Throughout 

her work in research, she gained a broad experience in multidisciplinary and technical investigations 

linking hydrology, hydrogeology and ecology. During this time she worked closely with ecological 

and hydrogeological consultants, NPWS and academics. Her work focused on identification of 

environmental impacts controlled by meteorology and hydrogeology, evaluation of vulnerability, risk 

assessment and implementation of mitigation measures for groundwater dependent terrestrial 

ecosystems. 

Project No.: 07_136 Leixlip Spa 

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EXECUTIVE SUMMARY 

Leixlip Spa site in Co. Kildare is a wetland area which developed on five distinct terraces with shallow 

bedrock and constitutes part of the Rye Water Valley Special Area of Conservation (site code: 

001398). The site contains many rare and protected habitats and species including calcareous 

grassland and petrifying tufa springs. The ecological monitoring of the wetland suggests that the site 

has been drying out for the past two decades. Hydro-G was engaged by Kildare County Council to 

investigate and evaluate water resources within Leixlip Spa, Co. Kildare to explain these ecological 

changes and to a construct conceptual model of water movement throughout the site for future 

conservation of the site. Investigation of local water resources included identification of springs and 

seepages, in situ physiochemical analyses, hydrochemical analyses of selected discharge locations 

and flow measurements. Results facilitated identification of different groundwater discharge zones 

and conceptualisation of groundwater flow pathways within the site. Review of historical information 

revealed that parts of the site were artificially modified which is likely to have impacted upon ecology 

of the site. This data added to the developed conceptual model. 

The findings of this study relate to monitoring conducted in December 2007 and January 2008, which 

in hydrological terms represents a recharge period. Seasonal variations may occur. 

The field monitoring and data analysis suggest that water at the Leixlip Spa site originates from a 

complex groundwater system combining two sources. The main source of water comes from a 

deeper, older and warmer groundwater system, discharging at the top of the first terrace through the 

Spa Well. The second is a more recent, shallow groundwater that flows through the karstified 

limestone bedrock with the main groundwater discharge located in the vicinity of the fen wetland 

habitat (‘filtering ponds’) at the most elevated, southern terrace. Rainfall runoff also plays a part. 

Hydrochemical analysis suggests that groundwater discharging from the warm spring at the Spa Well 

is highly mineralised and is the dominant source of water within the site. It is also evident that 

warm water discharging from the Spa Well drains northwards and flows into and through the shallow 

system, resulting in water being mixed with more recently recharged water. Overland flow is also 

apparent. The groundwater flow in the shallow system also occurs through conduits. Due to the 

steep topography of the site, shallow depth of subsoil (if any) and karstic nature of bedrock, 

groundwater can easily discharge through rock faces and later flow over ground toward the river Rye 

Water. A number of discrete springs were noted at the 2nd and 3rd terraces. The physio-chemical 

and hydrochemical analyses revealed that the Spa Well directly influences some conduit flows that 

are relatively distant from the Spa Well itself and that waters on the 2nd and 3rd terraces are a 

mixture of the Spa Well water and the shallow system groundwater. Water flow on the 4th and 5th 

terraces originates mainly from surface runoff contributions from the more elevated upper terraces. 

Hydrochemical analysis revealed also a leakage from the canal that occurs upgradient from the 

wetland area at the first terrace but its contribution to overall water resources within the site is 

relatively small. 

Review of historical information revealed that the original outflow from the Spa Well was in the north 

westerly direction. The historical evidence suggests that the outflow was diverted towards the north 

easterly direction in late 1970s or early 1980s. Subsequently, water from the Spa Well discharges 

into the ‘filtering ponds’ area that contains the cold springs. The implication of such engineering is a 

limitation in water delivery to the western side of the 1st terrace manifested in drying of this wetgrassland 

habitat. It is also possible that diversion of the groundwater flow away from the western 

side of the 1st terrace occurred unintentionally during sewage works undertaken in 1980s. Analysis 

of water quality within the Leixlip Spa site and in the Intel drain located at the western boundary of 

the 1st terrace showed different hydrochemical signature in the drain than in all other samples from 

the Leixlip Spa site suggesting different water origin. This further supports our interpretation that 

Project No.: 07_136 -iv- 

Leixlip Spa


the Intel boundary drain does not currently act as a drainage channel drawing groundwater from the 

wet-grassland habitat which has been reported to be drying out. Mitigation measures for this habitat 

could include reengineering of the present pipe layout to restore the original discharge from the Spa 

Well to the north – north westerly direction. However, this will result in reduction of groundwater 

flow towards the cold springs (‘filtering ponds’) and is likely to impact on the local ecology 

surrounding the ponds, which have adjusted to present conditions over time. Considering a probable 

local recharge of the cold springs, redirection of the groundwater discharge from the Spa Well might 

cause an increase in seasonal variation in water levels in the ‘filtering ponds’ area and subsequently 

could cause seasonal drying of this fen-wetland. Hydrochemical changes could also occur. Further, 

redirection of the outflow from the Spa Well away from the ‘filtering ponds’ will decrease a volume of 

water cascading to the 2nd terrace at the eastern side and this will affect distribution of water at 

down gradient terraces. This is likely to be compensated by more water flowing on the western side 

but is likely to lead to habitat transformations on a local scale. The potential risks posed to the 

healthy existing wetland habitat on the east side of the upper terrace suggest that it does not seem 

prudent to interfere again with the pipe layout, from a hydrological perspective. The other potential 

option for the grassland habitat restoration is to reengineer the ex-parking area south to the Leixlip 

Spa SAC. This area currently comprises compacted soil/hard standing surface with a topographic 

gradients towards the north and the west. Measures to harvest surface runoff water from hard 

standing surfaces and redirect collected water towards the western grassland habitat has potential to 

partially re-wet the area. These stormwater design measures are possible and require collaboration 

between Hydro-G and other project partners. 

With respect to the lowest terrace, which was reported to be drying out, Hydro-G’s investigation has 

not revealed any structural changes either in local hydrology or hydrogeology. Therefore, the most 

probable cause of these changes is natural habitat transformation resulting from plant growth, 

increased evapotranspiration needs and accumulation of organic matter, which has caused an 

increase in ground level on this terrace. Cessation of grazing may have contributed to the vegetation 

overgrowth of this floodplain. Future ecological characteristics of the floodplain rely upon 

management strategies with respect to the plant growth and accumulation of organic matter rather 

than management of water flows within the Leixlip Spa site. 

Project No.: 07_136 -v- 

Leixlip Spa


TABLE OF CONTENTS 

1. Introduction -------------------------------------------------------------------------------------1 

1.1. Project Objectives ---------------------------------------------------------------------------- 1 

1.2. Project Methodology-------------------------------------------------------------------------- 2 

1.2.1. Desk Study ------------------------------------------------------------------------------- 2 

1.2.2. Field Work -------------------------------------------------------------------------------- 2 

1.2.3. Reporting --------------------------------------------------------------------------------- 3 

2. Desk Study --------------------------------------------------------------------------------------4 

2.1. Environmental Settings ---------------------------------------------------------------------- 4 

2.1.1. Geological Settings ---------------------------------------------------------------------- 4 

2.2. Hydrogeology --------------------------------------------------------------------------------- 4 

2.2.1. Aquifer Characteristics------------------------------------------------------------------- 4 

2.2.2. Groundwater Quality--------------------------------------------------------------------- 5 

2.2.3. Water Levels ----------------------------------------------------------------------------- 5 

2.3. Hot Springs in the Kildare Area-------------------------------------------------------------- 5 

2.3.1. Historical Hydrochemical Data from Leixlip Spa Well ---------------------------------- 5 

2.4. Groundwater Quality Monitoring within Intel Ireland Ltd.---------------------------------- 7 

2.5. Additional Information ----------------------------------------------------------------------- 7 

3. Field Work Results ------------------------------------------------------------------------------8 

3.1. Site Observations----------------------------------------------------------------------------- 8 

3.2. Water Flow within the Site including Spring and Seepage Locations ---------------------- 9 

3.3. Hydrochemical Analyses --------------------------------------------------------------------- 10 

3.4. Assessment of Flow Volumes ---------------------------------------------------------------- 12 

4. Conceptual Model of Leixlip Spa Flow Patterns---------------------------------------------- 13 

5. Conclusions and Recommendations---------------------------------------------------------- 15 

REFERENCES---------------------------------------------------------------------------------------- 17 

FIGURES-------------------------------------------------------------------------------------------------------- 18 

Appendix A ----------------------------------------------------------------------------------------------------- 24 

Appendix B ----------------------------------------------------------------------------------------------------- 27 

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Leixlip Spa


LIST OF FIGURES 

Figure 1 Location of the Leixlip Spa site, (OS LicenceEN0043207).....................................................19 

Figure 2 Geology in vicinity of the Leixlip Spa site. Source: www.gsi.ie..............................................20 

Figure 3 Location map of Intel's groundwater monitoring wells. Source: Intel Ireland..........................21 

Figure 4 Site location including physio-chemical monitoring points, Leixlip Spa, Co. Kildare .................22 

Figure 5 Layout of the drainage at Leixlip Spa. Source: Kildare County Council ..................................23 

LIST OF TABLES 

Table 1 Summary of hydrochemical analysis of the warm and the cold springs at Leixlip Louisa Bridge 

site, 1981-1983, from Minerex, 1983.......................................................................................6 

Table 2 Results of in situ survey, Leixlip Spa, 10/12/2007 ...............................................................31 

Table 3 Results of in situ survey, Leixlip Spa, 16/01/2008 ...............................................................31 

Table 4 Results of hydrochemical analysis, Leixlip Spa, 16/01/2008..................................................32 

Project No.: 07_136 -vii- 

Leixlip Spa


1. Introduction 

In December 2007, Hydro-G was engaged by Kildare County Council to investigate and evaluate 

water resources within Leixlip Spa, Co. Kildare in light of increasing concerns about the site’s 

ecological health and integrity. 

The site is located on the outskirts of Leixlip, approximately 2km west of the town, between the Intel 

Ireland factory and the Royal Canal. The national grid reference for the site is 299500, 236500. The 

location map is presented in Figure 1. The site constitutes part of the Rye Water Valley Special Area 

of Conservation (site code: 001398) containing protected habitats including calcareous grassland and 

petrifying tufa springs, as well as rare and protected species of fauna including molluscs species 

Vertigo moulinsiana and Vertigo angustior. 

Topographically, the Leixlip Spa site lies on number of terraces carved in limestone bedrock, which 

were created during construction of the Royal Canal in the 18 th century. This bedrock exposure 

resulted in a number of wetland habitats that developed on subsequent terraces in response to a 

continuous discharge of water from the bedrock. The entire area of the site is 6000m 2 , 

approximately, 40m wide and 150m long with a topographic drop of 20m in a south-north direction 

towards the river Rye Water. 

In addition to its high ecological values the Leixlip Spa is known also for its archaeological features 

including a hexagonal well and a Roman Bath which were created in the 18 th Century following a 

discovery of a hot spring. The hot spring that supplies water to this Bath was discovered during the 

construction of the Royal Canal and water from the spring is highly mineralised, specifically rich in 

iron, for which it gained its spa status. The original hot spring is located underneath the Royal Canal 

and was diverted to a man-build Spa Well of a hexagonal shape that is located at the eastern side of 

the entrance to the site. 

The ecological and archaeological features of the Leixlip Spa have been extensively investigated 

throughout decades and some documentation dates back as far as the 18 th century. Nevertheless, it 

is the site’s unique fauna and flora that have been given most attention following the implementation 

of the EU Habitats Directive (92/43/EEC). The site’s ecological features are reported to have 

deteriorated over recent years and as the majority of the area comprises wetland habitats, there is a 

possibility that changes in the site’s hydrological controls merits investigation (Moorkens, Dooge, 

pers. comm.). 

1.1. Project Objectives 

Kildare County Council engaged Hydro-G to investigate the hydrological regime of the Leixlip Spa site 

and to develop a water management strategy to prevent further deterioration and to facilitate 

sustainable conditions. 

The specific objectives of the project were specified by Kildare County Council, as follows: 

“The objective of this hydrological study is to determine the movement of water through out the site 

to determine how this water can be used most efficiently to maintain the conservation status of the 

site particularily in relation to the Shining Sickle Moss (Drepanocladus vernicosus) and the semi 

aquatic snail species Vertigo angustior and Vertigo moulinsiana”. 

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Leixlip Spa


The issues to be addressed were specified as: 

Determine the source of water on the site and if there are other springs other than the 

existing spring in the Hexagonal pool on the site including the slope. Ascertain if leakage from 

the canal is contributing to the water feeding the site. 

Determine the effect of drain on the Intel side of the site is having on the site as a whole and 

if it contributed to the drying out of the left hand side of the site. 

Identify drainage pipes etc. on the site and the effect they are having on the hydrology of the 

site. 

Determine the potential for restoring the dry area (to wetland) of the site on the left hand 

side without impacting on the rest of the site. 

Determine how the water and the water movement through the site can be maximised to 

benefit the site as a whole. 

1.2. Project Methodology 

The project was carried out in three stages, namely a desktop review, site investigation and 

reporting. 

1.2.1. Desk Study 

Kildare County Council provided Hydro-G with existing documentation on the ecology and the 

archaeology of the Leixlip Spa. In addition, a contact with Intel Ireland was facilitated by Mr. Simon 

Wallace (Kildare Co. Co.) which provided additional information/data on local hydrology and 

hydrogeology gathered in accordance with the Intel’s IPPC licence agreement, which deems Intel 

Ireland responsible for biannual monitoring of groundwater levels and groundwater quality within the 

Intel site. Intel’s IPCC licence also requires monitoring water quality in the Spa Well. Additional 

information was gathered during an interview with Mr. Niall Meagher, a retired architect for Kildare 

County Council who has been involved in Leixlip Spa projects and consultations with Dr. Jim Ryan 

and Mr. Niall Lockhard of the National Parks and Wildlife Services. A search of the Geological Survey 

of Ireland archives was also undertaken. 

1.2.2. Field Work 

In total three site visits were undertaken. 

The first visit was undertaken on the 2 nd of December 2007 and involved a site meeting with 

ecologists Mr Declan Doogue and Mr Brendan O’Hanrahan. This meeting was facilitated by Mr. Simon 

Wallace (Kildare County Council). During that meeting, floristic aspects of the Spa were discussed 

and recent drying trends of the uppermost grassland habitat were outlined. This specifically refers to 

the western side of the gravel pathway which, according to Mr. Doogue, used to provide a suitable 

habitat for wet loving grasses and marsh orchids in the past. During this field visit, this area was 

reported as ‘not wet’ in winters within the past 20 years, leading to a loss of this habitat. 

The second visit was carried out on the 10 th of December 2007 and involved a meeting with Dr 

Evelyn Moorkens, malacologist, and an investigation of springs and seepages within the site. Dr 

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Leixlip Spa


Moorkens explained recent problems with Vertigo angustior habitat in the lowest terrace i.e. at the 

Rye River floodplain. The increasing density of grasses over the past years suggests that the site 

undergoes a drying trend. It has also been noted that the ground level increased due to 

accumulation of organic matter. The entire Leixlip Spa site was surveyed for springs and seepages 

and physio-chemical characteristics were measured. In total, 23 locations were surveyed. Water 

samples were collected from 10 no. locations. However, problems with the ionic balances obtained 

negated use of the initial laboratory results. 

During the third site visit, undertaken on the 16 th of January 2008, the in situ physio-chemical survey 

of springs and seepages was repeated to compare with December’s results and 8 no. water samples 

taken from selected locations. These were delivered to an accredited laboratory for hydrochemical 

analysis. Flow measurements were conducted to assess flow patterns within the site. 

1.2.3. Reporting 

A preliminary report was provided in December 2007 (Appendix A). 

This report presents the integrated assessment of the site’s hydrology, hydrochemistry and the 

emerging conceptual hydrological model for the Leixlip Spa site. 

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Leixlip Spa


2. Desk Study 

2.1. Environmental Settings 

The Leixlip Spa site is located on the Leixlip-Maynooth local road R148, approximately 2km west of 

the Leixlip town centre. The R148 constitutes the site’s southern boundary and an access to the site 

is also provided from this road. The site is adjacent to the Intel Ireland factory, which is to the west, 

and the eastern boundary runs along the Royal Canal. To the north, the site is bounded by the river 

Rye Water. The site location map is presented in Figure 1. 

2.1.1. Geological Settings 

The bedrock geology underlying the site is discussed in the GSI publication “Geology of Kildare - 

Wicklow, (McConnel et al., 1994). The 1:100,000 scale bedrock geology map for the area (Sheet 16) 

indicates that the subject site is underlain entirely by rocks of Calp Limestone Formation (CD), which 

was formed during Chadian age and belongs to Lower Carboniferous system (refer to Figure 2). 

During the Carboniferous period, the eastern part of Ireland underwent uplift and erosion after which 

there was a period of subsidence in the area. Throughout this time, the sea invaded the land 

allowing marine sediments to accumulate across most of the Sheet 16 map, including Leixlip. The 

Calp Limestone is a muddy limestone and was deposited in thick sequences in turns with muds in 

deep sea basins with a limited fauna. It consists of dark grey, fine grained, graded limestone with 

interbedded black, poorly fossiliferous shales. In later periods, subsequent erosions reworked the 

upper end of the Calp and overlying younger limestone deposits allowing for localized karstification 

(in places where the rock was temporarily exposed) and/or for deposition of granite boulders within 

the Calp. 

There are number of faults in this area. These are predominantly in an east-west direction. One of 

these faults runs in close proximity to the site, along it’s southern boundary, Figure 2. 

With respect to overlying strata, the majority of this area is covered by till of sea origin and derived 

from limestone and overlain with Grey Brown Podzolics and Gleys (Gardiner, 1980). The GSI (GSI, 

2007) reports these deposits to be less than 3m deep west of Lucan village and the groundwater 

vulnerability rating, which classifies this area as ‘high’ vulnerability, suggests depths to bedrock of 

approximately 3 - 5m. 

2.2. Hydrogeology 

2.2.1. Aquifer Characteristics 

According to the GSI Groundwater Body description (GSI, 2007), the Leixlip Spa Site is underlain by 

the Dublin Groundwater Body, which generally is low permeability and the majority of groundwater 

flow occurs along faults where permeability is increased by dolomitisation of the rock. The majority 

of flow occurs close to the surface and in isolated fractures at depths of up to 50m below ground 

level (bgl). Relatively low permeabilities deem this bedrock to be of limited development potential 

and therefore the Geological Survey of Ireland classified it as Locally Important aquifer, with 

moderate potential in local zones only. Groundwater yield potential is therefore highly dependent on 

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Leixlip Spa


local fracturing of the bedrock. The general flow direction is towards the sea i.e. to the east; 

however, local variations, conditioned by the presence of surface water channels, are likely. 

2.2.2. Groundwater Quality 

The general water quality in this limestone aquifer suggests very hard water with total hardness 

between 350-480 mg/l CaCO3 and alkalinity of 300-350 mg/l CaCO3. Electric conductivities are also 

high and can vary from 550-900 µS/cm. This water has a is calcium bicarbonate signature (GSI, 

2007). 

2.2.3. Water Levels 

Very little data exists on water levels in the area. The only available data were provided by Intel 

Ireland, which monitors groundwater levels within their site. These were not available as specific 

values; however, extracts from the monitoring reports provided by Intel stated that there are no 

trends in the groundwater level behaviour. 

2.3. Hot Springs in the Kildare Area 

A number of hot springs are reported in the Dublin Groundwater Body, which are aligned along the 

Lucan – Celbridge transect. These springs were extensively studied in 1983 (Minerex, 1983) and are 

associated with deep faults and/or synclines, which allow deeper and warmer water to surface. The 

temperature in these springs are reported to range between 12.5-25 °C. Historical data from the 

1970’s and 1980’s (Minerex, 1983) suggest high chloride and total dissolved solids content in springs 

that are specifically associated with synclinal structures. The Spa Well at Leixlip Spa classifies as one 

of these springs occurring close to the Celbridge Syncline. Water signature in these springs can be 

mostly associated with sodium-chloride waters and is usually indicative of an older water age. 

Historical data (Meagher, 1976) suggest that the Leixlip Spa Well contained also large concentrations 

of iron, for which it was often referred to as a Chalybeate spring. 

An assessment of flows in these springs (Minerex, 1983) suggests normal seasonal discharge 

patterns with increased flows in spring and decreased in autumn which suggests groundwater flow 

controlled by the hydrological cycle. Similar patterns were found in the monitored spring’s 

temperature variations. 

2.3.1. Historical Hydrochemical Data from Leixlip Spa Well 

Burdon’s report on Irish geothermal potential (Minerex, 1983) provides a good overview of the 

quality and annual characteristics of groundwater in the Leixlip Spa Well. The report contains 

information on two springs within the Leixlip Spa site, one warm (Spa Well) and one cold. The latter 

being sampled through a manhole, which implies that the spring and its channel were modified prior 

to the study period which was carried out between 1981 and 1982. Hydro-G attempted to identify 

the location of the cold spring and the sampling location, however this was unsuccessful. Some later 

documentation, retrieved from the NPWS’s archive (Ecoserve, 2006), suggests a cold spring is 

located in an area of the two ponds on the eastern side of the upper terrace of the Leixlip Spa, 

approximately 50m downhill from the Spa Well. 

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Leixlip Spa


Hydrochemistry data (Minerex, 1983) show significant differences between the warm and cold 

springs suggesting strongly that both springs are recharged from two different aquifers, although 

deeper water may be diluted with more recent recharge on its way up to the ground surface. As well 

as differences in water temperature, which for the warm spring ranged from 13 to 16 °C and for the 

cold spring it ranged from 8 to 13 °C, differences were found in electric conductivity, total dissolved 

solids, concentrations of chloride, sodium, sulphates, nitrates and to a lesser extent in concentrations 

of calcium, magnesium and bicarbonate. The warm spring water, generally, had a sodium-chloride 

signature with high electric conductivities (EC > 1500 µS/cm) and high total dissolved solids (TDS > 

1000 ppm). The cold spring water had a calcium bicarbonate signature with EC varying between 

700-1100 µS/cm and TDS 490-770 ppm. Chloride concentrations in the warm spring were > 450 

mg/l while in the cold spring they were < 50 mg/l. These differences are summarised in Table 1, 

which shows that the two springs belong to separate groundwater systems: a deeper system 

represented by the warm spring and a shallow system, dependent on more recent recharge and 

flowing through the upper limestone aquifer, represented by the cold spring. Full datasets are 

available on request from Hydro-G. 

Table 1 Summary of hydrochemical analysis of the warm and the cold springs at Leixlip Louisa Bridge site, 1981- 

1983, from Minerex, 1983 

Parameter 

Summer (August 1981) Winter (March 1982) 

Warm Spring Cold Spring Warm Spring Cold Spring 

Temperature [°C] 16.5 12.3 16.2 7.8 

Electric Conductivity [µS/cm] 1680 700 1800 1100 

Total Dissolved Solids [ppm] 

1176 490 1260 770 

Calcium [mg/l] 157 117 144 250.5 

Magnesium [mg/l] 35.5 20.5 34 25 

Sodium [mg/l] 123 25 340 42 

Potassium [mg/l] 7.2 3.6 6.7 3.5 

Bicarbonate [mg/l] 212 297 324 439 

Sulphate [mg/l] 63 119 55.9 397 

Chloride [mg/l] 447 33 483 38 

Nitrate [mg/l] 0.89 5.76 0.86 70 

Iron [mg/l] 0.36 0.26 0.11 0.29 

More recent water quality data for the warm spring were supplied to Hydro-G by Intel Ireland (Mr. 

Michael Cullen). These data span from 1998 until 2006 and conform with Burdon’s results, although 

relatively high variations in sodium, sulphate and calcium level were noted. However, the Spa Well 

is continuously being polluted with litter, which could affect its water quality. Nevertheless, the Intel 

results confirmed high temperature, EC, TDS and chloride levels in the Leixlip Spa Well (warm 

spring). 

With respect to iron concentrations, data presented by Burdon suggest relatively high concentration 

with comparison to the Intel data, for which only in 3 out of 8 measurements exceeded value of 0.1 

mg/l. Data provided by Intel are available on request from Hydro-G. 

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Leixlip Spa


2.4. Groundwater Quality Monitoring within Intel Ireland Ltd. 

Extracts from the groundwater quality monitoring reports for three monitoring boreholes located 

within the Intel Ireland site were also provided by Intel Ireland. Two of these wells (MW13 and 

MW15, Figure 3) are located approximately 400m west of the Spa Well. Another well MW14 is 

located adjacent to the western boundary of the site (~2m from the fence). The results presented in 

the report from Intel suggest different water signatures in monitoring boreholes MW13-MW15 and 

MW14, the difference being 5-7 times higher chloride levels in MW14 than in MW13 and MW15, and 

subsequently higher EC levels. This suggests that MW14 is influenced by water discharging from the 

Spa Well. The reports states also that chloride levels increased throughout 2006-2007 monitoring 

period. 

2.5. Additional Information 

During the initial site visit in December 2007, Mr Simon Wallace presented a current understanding 

of the flow mechanism, which suggested that water from the Spa Well is directed through an 

underground channel to two ponds, which, in the literature (Matthews, 2007), are referred to as 

‘filtering ponds’. These ponds are located approximately 50m down gradient from the Spa Well and 

their assumed function is to filter water from the Spa Well on its way the Roman Bath, built c. 100m 

away from the well in direction of the Rye Water river. However, other information (Ecoserve, 2006) 

suggests that these ‘filtering ponds’ are actually cold springs. The suggested layout of the 

underground channel from the Spa Well was parallel to the Royal Canal, i.e. north eastern direction 

(Figure 4). In addition, a sketch map (drawing) was presented by Mr. Wallace, which showed 

presence of a service pipe under the upper part of the site. This pipe runs in north eastern direction 

from the car park, towards the ‘filtering ponds’ and, approximately 20-30m down gradient from the 

Spa Well, it sharply turn eastwards towards and under the Royal Canal (Figure 5). Hydro-G 

contacted Water Services in Kildare County Council to investigate precise location, depth and 

circumstances of laying this pipe, but no further information was available on file. The approximate 

time of laying the pipe is early 1980s. 

Hydro-G initiated also a meeting with Mr. Niall Meagher, who is a retired architect for Kildare County 

Council. During that meeting, a drawing from 1981 was presented that included an underground 

pipe suggesting a discharge of water from the Spa Well in north western direction and later, after 

approximately 30m from the Spa Well, the pipe turning at 90° towards north east (Figure 3). 

Further literature review (Minerex, 1983) confirmed that the original outlet from the Spa Well is in 

north western direction (Photo 1). 

The above information suggests that the original discharge from the Spa Well is in north western 

direction, directly towards the Roman Bath. It is likely also that the underground pipe from the Spa 

Well was diverted in north eastern direction in 1970’s or early 1980’s. 

Project No.: 07_136 -7- 

Leixlip Spa


1983 2008 

Photo 1 Photographs of Leixlip Spa Well from 1983 (Minerex, 1983) and from 2008 (Hydro-G). 

3. Field Work Results 

The field work was designed to investigate the groundwater flow pathways within the study site and 

was initiated with a site walkover, during which majority of springs and seepages were identified. 

Further investigation of these springs and seepages included examination of their physio-chemical 

characteristics (temperature, EC, TDS, pH) and their hydrochemical signature to establish linkage 

between different groundwater discharge zones. Subsequently, this facilitated development of a 

conceptual model of the groundwater flow throughout the site. Flow measurements were taken, 

where possible, to assist building the conceptual groundwater flow model. 

3.1. Site Observations 

The entrance to the site leads though a hard standing area that in the past served as a car parking. 

This was created in 1980’s to facilitate access to the site. However, continued misuse of the parking 

resulted in gating access to the car park in early 1990’s. As a result, the remnant parking area 

comprises partially compacted soil and partially hard standing surface. 

Within the SAC boundary five terraces were identified, whose topography steeply dips in a northern 

direction. This distinct topography controls water flows within the site, which, due to the cascading 

nature of the bedrock, tends to overflow from one terrace to another or seep from the bedrock and 

through the relatively shallow soil. The features of the Leixlip Spa site are presented on Figure 4. All 

sampling locations were numbered as presented in Figure 4 and that is how they are referred to in 

this text. 

The first terrace extends from the site entrance to the Roman Bath. There are two ponds, an Upper 

Pond and a Lower Pond on the eastern extent of the site half way between the Spa Well and the 

Roman Bath. Historical documents (Matthews, 2007) suggest that these ponds act as filters for the 

spring water from the Spa Well on its way to the Roman Bath. As such, these ponds are often 

referred to as ‘filtering ponds’. However, marshy vegetation and presence of tufaceous deposits 

surrounding the ponds suggests water rich in calcium bicarbonate seeping through the ground in this 

location. There are no bedrock exposures at this terrace and the ground looks relatively dry, i.e. free 

draining except for the fen-wetland pocket around the ‘filtering ponds’. Behind the western edge of 

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this terrace, there is a deep drop in elevation, which is a natural feature although deepening by 

approximately 1m did occur in 1990’s to prevent people from entering the Intel site from the Leixlip 

Spa site (pers. comm. with Mr Cullen, Intel Ireland). After the Roman Bath end of this terrace, the 

topography drops significantly. 

The second terrace comprises a narrow strip with water flowing overland at its eastern side. This 

water originates from two streams that flow out from the Lower Pond of the first terrace. Water 

discharges into this terrace also from the outlet from the Roman Bath. This terrace is generally wet 

and it is difficult to distinguish whether water comes from the overland flow only or also seeps from 

the ground. Large amounts of calcium carbonate (tufa, calcite) are present in numerous locations on 

the ground surface. Well structured calcite can be found on a slope where water cascades from the 

two streams formed after the Lower Pond. However, small pieces of tufa can be also found on the 

ground throughout the terrace, which suggests that water seeps also directly from the ground. 

Flows are relatively strong at this terrace. However, sloping topography rules out measuring of 

these flows. 

The third terrace contains a small pond surrounded by wetland vegetation. Bedrock outcrops are 

visible and large calcite deposits can be found in various locations, but specifically in eastern parts of 

the pond (referred thereafter as ‘tufa pond’). A large hole was found in the bedrock face, on the 

eastern side of the terrace, and a distinct water discharge was recorded in this location. 

The fourth terrace covers an extensive area between (and beneath) the ‘tufa pond’ and the river 

floodplain. This terrace is overgrown with rush-like vegetation and the ground is soft and soggy. 

Water movement on this terrace is through numerous small streams, which run towards the river. 

Two major streams were recorded, one on the eastern end and one on the western end of the 

terrace. 

The floodplain constitutes the fifth terrace. A walkover survey was conducted. Streams were 

identified discharging into the river. No distinct springs were identified. However, this terrace is 

overgrown with dense reed-type vegetation. Other terraces are grass-moss covered. This area was 

grazed historically but this practice was discontinued in the 1980’s. 

3.2. Water Flow within the Site including Spring and Seepage Locations 

The following springs and seepages were identified during the Hydro-G’s site visits: 

1. The Spa Well – a warm spring at the most elevated, southern end of the site; 

2. Cold seepage springs at the east side of the first terrace (in vicinity of ‘filtering ponds’); 

3. Cold springs at the third terrace. There are numerous springs at this level. Distinct water 

discharges were identified at the southern verge of the ‘tufa pond’ and through a large hole 

in the bedrock face (0.3m x 0.4m) at the eastern side of the rock cliff and from the ground 

on the western side of the site; 

4. No distinct seepages and springs were identified at the fourth terrace. However, tufa 

deposition is common in a base of small streams that run on both western and eastern sides 

of the site. More solid deposits were identified in places where the topographic gradient is 

high and water cascades from one step to onother. 

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The general flow pattern noted during the site visits is that water discharges from the Spa Well 

(monitoring point 9, Figure 4) and drains underground in northern direction towards the two ‘filtering 

ponds’ (monitoring points 12-17) which create a small fen wetland on the eastern side of the first 

terrace. At the point where the underground drain from the Spa Well surfaces (monitoring point 8), 

a man made structure houses a 16” diameter pipe and a loud sound of cascading water was recorded 

to come from inside this pipe. A small spring (monitoring point 7) was noted immediately adjacent 

to the east of the 16’’ pipe (monitoring point 8). A large deposit of precipitated iron was recorded at 

the monitoring point 7. These two water sources (monitoring points 7 and 8) constitute a stream 

that flows for approximately 10 metres and then disperses into the wetland area (monitoring points 

12-17). There are two distinct ponds here, referred to as Upper and Lower; however, the eastern 

side of these ponds (at the Canal’s boundary) remains also waterlogged (monitoring point 18). From 

the Lower Pond water flows through a narrow stream (monitoring point 6), splits into two smaller 

streams (monitoring points 19 and 20) and flows over the ground into the second terrace. An 

underground pipe connects the Roman Bath (monitoring point 5) with either the Lower Pond directly 

or with the small stream discharging from it. The Roman Bath is located between (mid-way) the first 

and the second terrace. Water outflows from the Roman Bath into the second terrace through a 

sluice and then flows over ground into the third terrace. Additional groundwater sources were 

recorded at the third terrace and included a big opening in the rock face (monitoring point 3), which 

reveals the conduit nature of a very shallow bedrock with groundwater discharge into the site. 

Fractures are common in upper horizons of limestone bedrock and this assists discrete distribution of 

numerous springs at this level, which flow into and throughout a shallow ‘tufa pond’ located in the 

central area. From here, water flows on the surface through numerous small streams and seeps 

through the shallow soil. The general high topographic gradient of the site extorts relatively fast flow 

rates and this facilitates escape of CO2 from water at all terraces, which in turns causes calcite 

precipitation from groundwater. It is apparent though, that although calcite precipitation occurs in 

the vicinity of the ‘filtering ponds’ at the first terrace, it is much more abundant at the second and 

third terraces where big consolidated pieces of tufa can be found. This is usually associated with 

high topographic gradients. At the base of the fifth terrace, water was found in two streams at both 

western and eastern boundaries of the site (points 1 and 2). These streams discharge into the river 

Rye Water. 

3.3. Hydrochemical Analyses 

3.3.1. Introduction 

Water samples were collected from a variety of monitoring locations in December 2007 and January 

2008. However, the 2007 sample results were compromised by laboratory equipment failure. 

Therefore, only the January 2008 results could be used. The parameters were chosen in order to 

distinguish hydrochemical signatures of analysed water samples. Eight (8 no.) water samples were 

collected and the parameters analysed included ions of calcium, magnesium, nitrate, sodium, 

potassium, sulphate, ortho-phosphate, chloride, iron (dissolved and total), carbonate, bicarbonate, 

alkalinity and total hardness. In addition, Hydro-G carried out a physiochemical monitoring at 23 

locations throughout the site. Sampling locations are presented on Figure 4. The analysis was 

undertaken along the south - north transect. Field and laboratory data as well as the full 

interpretation of hydrochemical analyses are presented in Appendix B. The interpretive summary is 

presented below. 

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3.3.2. Hydrochemical Interpretative Summary 

The physiochemical monitoring carried out in situ revealed significant differences in water 

characteristics throughout the site during two sampling occasions (10/12/2007 & 16/01/2008) and 

this suggests presence of different sources of water within the site. 

It is evident that water temperatures decrease from the south to north direction, as does the electric 

conductivity. The relative increase in both water temperature and EC that was recorded in the ‘irony 

spring’ (monitoring point 7) suggests small leakage from the canal. In the next, further down 

gradient sampling location, it was also noted that both the temperature and EC were higher in the 

Upper Pond than in the Lower. In addition, lower temperature and EC in localised places around the 

ponds suggest multiple sources of water at these locations, i.e cold springs which mix with warmer 

water coming from the Spa Well. These cold springs are likely to originate in the shallow system, 

which is expected to be cooler and less mineralised in comparison to water discharging from the 

deeper system at the Spa Well. Abundance of calcite precipitated in this area and specifically around 

the Lower Pond (monitoring point 18) suggests that groundwater discharges at this location. 

Integration of field data suggests that while the Upper Pond is fed by the Spa Well, the Lower Pond 

also has inputs from the shallow groundwater system. 

Water flow on the second terrace is by flow along the ground surface, which prevented monitoring of 

physio-chemical parameters. 

At the third terrace, there was an abundance of water flow and sources. Water was noted to enter 

from both overland flow and also from various sources directly in the ground and bedrock face. 

There were two sampling points on the fourth terrace but these were located within formed surface 

water channels. No direct groundwater discharge points were identified. 

The drain on the Intel site at the western boundary of the Leixlip Spa site contains water at its 

northern end only, which finishes at the approximate elevation of the Roman Bath (monitoring point 

24). Hydrochemical data from this location suggested water originating from surface runoff. 

With respect to total dissolved solids (TDS), these were found generally high at all terraces ~700- 

1000 ppm and its distribution at different locations is similar to that of electric conductivities. 

All the sampling locations showed alkaline conditions and were lowest in the Spa Well water. 

Subsequently, lower pHs were also found in places linked to the underground discharge from the Spa 

Well (monitoring points 8 and 11). Higher pH levels were found in places associated with cold 

springs and that supports the hypothesis that this water originates from the shallow system which is 

in contact with the alkaline bedrock. At lower terraces, the pH was generally higher. 

All laboratory samples collected at the Leixlip Spa site show very high mineralisation. The ionic 

balance analysis based on the hydrochemistry results showed that the majority of samples are of 

sodium-chloride (Na-Cl) signature, except for one sample – the Intel drain, which presented calcium 

bicarbonate character (Ca-HCO3). The sodium-chloride water signature dominates at this site 

because of high concentrations of chloride delivered to the site from the Spa Well. Sodium-chloride 

water is associated with older groundwater (Minerex, 1983). This type of water was found at 

monitoring locations on all terraces of the site; from the discharge drain feeding from the Spa Well to 

the wetland ponds area, in the Roman Bath and as far down as at the boundary between the fourth 

terrace and the flood plain. The fact that all samples from the Lexlip Spa site are of the same 

character suggests that majority of water originates from the Spa Well, although some dilution with 

more recent, less mineralised water is evident. This is specifically reflected in decreasing chloride 

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concentrations as you move in a northerly direction towards the river Rye Water. The different 

character of water in the Intel drain suggests that its origin is surface runoff rather than groundwater 

drained from the Leixlip Spa site. These findings relate to monitoring conducted in 

December/January, which in hydrological terms represents a recharge period. Seasonal variations 

may occur and can be determined by further monitoring. 

3.4. Assessment of Flow Volumes 

In addition to the hydrochemical analysis, water flow rates were assessed in three locations to 

evaluate quantity of water discharged into and within the site. This was carried out in the stream 

feeding the ‘filtering ponds’ (above the Upper Pond, monitoring point 11), in the stream discharging 

from the ‘filtering ponds’ (below the Lower Pond, monitoring point 6) and at the entrance to the 

Roman Bath (monitoring point 5). Due to physical restrictions that limited conventional flow 

measurements, these measurements should be taken as approximate values only. 

In the stream feeding the ‘filtering ponds’ (monitoring point 11) the flow was determined at 9.05 

m 3 /hr. 

In the stream discharging from the ‘filtering ponds’ (monitoring point 6) the flow was measured at 

6.14 m 3 /hr. 

At the inflow to the Roman Bath (monitoring point 5) the flow was determined at 3.06 m 3 /hr. 

Field measurement suggest that water flows in the area of the ‘filtering ponds’ are dispersed and 

some seepage occurs into the bedrock, reappearing at lower terraces. These flow mechanisms could 

contribute to the high concentrations of chloride in the Intel’s monitoring borehole MW14. Seepages 

and interflows in the subsoil and upper limestone move throughout the site, mix with other 

groundwater sources, cold springs and rainfall to create a variable habitat controlled by hydrology. 

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4. Conceptual Model of Leixlip Spa Flow Patterns 

The observed flow patterns throughout the site were detailed in Section 3.2. Based on the 

physiochemical monitoring, hydrochemical analyses and flow rate assessments at the Leixlip Spa 

site, the following model of the hydrological regime is proposed: 

Water at the Leixlip Spa site originates from a complex groundwater system combining two 

sources: a deeper, older and warmer groundwater system, discharging at the top of the first 

terrace through the Spa Well; and a more recent, shallow groundwater that flows through the 

karstified limestone bedrock with the main groundwater discharge located in the vicinity of the 

‘filtering ponds’. Rainfall runoff also plays a part. 

Hydrochemical analysis suggests that groundwater discharging from the warm spring at the 

Spa Well is highly mineralised and is the dominant source of water within the site. It is also 

evident that warm water discharging from the Spa Well drains northwards and flows into and 

through the shallow system, resulting in water being mixed with more recently recharged water. 

Groundwater flow in the shallow system also travels through conduits, one of which is evident of 

the east side of the face of the terrace bounding the 2nd and 3rd terraces. Due to the steep 

topography of the site, shallow depth of subsoil (if any) and karstic nature of bedrock, 

groundwater can easily discharge through rock faces and later flow over ground toward the river 

Rye Water. 

The main source of water for the site is that from the warm spring known as the Spa Well. 

This water flows out of the well in northern direction through an underground drain. It is possible 

that this drain originally ran in a north westerly direction directly to the Roman Bath. However, 

this design was modified before 1981 and the drain was diverted towards the north east direction 

towards the two ‘filtering ponds’. 

It is possible that the original positioning of the underground drain linking the Spa Well and 

the Roman Bath, in a north western direction, was designed to bypass the cold springs (‘filtering 

ponds’) to avoid mixing with cooler water discharging from the upper bedrock. However, lack of 

any evidence of these cold springs on the 6 inch maps, which are usually very accurate for spring 

discharges, suggests that the cold spring could have resulted from digging out the substrate, 

which subsequently enhanced seepage and created the fen wetland habitat. 

Site layout drawings of the 1980’s (Meagher) suggest hat the drying out of the grass wetland 

on the Intel side of the 1 st terrace may be attributed to repositioning of underground drains and 

pipes rather than construction of the drain within Intel’s boundary. Further, water quality in the 

Intel drain shows different hydrochemical signature than samples collected within the Leixlip Spa 

site suggesting that this water originates from surface runoff. Very little or no water in the drain 

suggests that this depression does not act as a drainage channel and as such is unlikely to draw 

water from the grassland reported to be drying out. 

A cold spring is also located at the ‘filtering ponds’. Based on the disperse distribution of 

precipitated calcite at the ground surface around the cold spring, it is likely that there are many 

groundwater discharge points in this area, however the most pronounced is that at the northern 

end of the Lower Pond. Analysis of flow volumes suggested also that some seepage occurs into 

the bedrock in the area of the ‘filtering ponds’, reappearing at lower terraces. Seepages and 

interflows in the subsoil and upper limestone move throughout the site and mix with other 

groundwater sources, cold springs and rainfall to create a variable habitat controlled by 

hydrology. 

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There are two distinct water sources at the physical location where the drainage pipe from 

the Spa Well appears at ground level. Observations and field monitoring data suggest a small, 

but not significant, leakage from the canal. 

A number of discrete springs were noted at the 2 nd and 3 rd terraces. Water oozes from the 

ground and through the cliff face. The physio-chemical analysis suggests that this water is a 

mixture of the Spa Well water and the shallow system groundwater. Field data suggests that the 

Spa Well directly influences some conduit flows that are relatively distant from the Spa Well itself. 

Water flow in the 4 th and 5 th terraces (floodplain) originates mainly from surface runoff 

contributions from the more elevated upper terraces. No springs were identified within the 4th or 

5th terrace. 

Field data suggest that the Intel boundary drain does not currently act as a drainage channel 

drawing groundwater from the wet-grassland habitat which has been reported to be drying out. 

Data from a groundwater monitoring well on the Intel site suggests that water from the deeper 

groundwater system on the Leixlip Spa site influences hydrochemistry at that location. 

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5. Conclusions and Recommendations 

5.1 Field monitoring and data analysis suggest that water at the Leixlip Spa site originates from 

a complex groundwater system combining two sources. 

5.2 The main source of water comes from a deeper, older and warmer groundwater system, 

discharging through the Spa Well at the top of the first, most elevated, southern 

terrace. The second is a more recent, shallow groundwater that flows through the 

karstified limestone bedrock with the main groundwater discharge located in the 

vicinity of the ‘filtering ponds’, which are also on the first terrace. Overland flow is 

also apparent. 

5.3 The majority of groundwater discharge locations were identified within the 1st terrace. 

However, some discrete groundwater discharges exist also at the 2nd and 3rd 

terraces. No springs were identified within the 4th or 5th terrace (floodplain). 

5.4 Review of historical information revealed that the upper (1st) terrace underwent a series of 

modifications which are likely to have altered the original, natural groundwater 

pathways within the site. The original outflow from the Spa Well was in the north 

westerly direction. The historical evidence suggests that the outflow was diverted 

towards the north easterly direction in late 1970s or early 1980s. Subsequently, 

water from the Spa Well flows towards the cold springs (‘filtering ponds’). The 

implication of such engineering is limitation in water delivery to the western side of 

the 1st terrace manifested in drying of this wet-grassland habitat. To verify this 

hypothesis, further investigation is necessary and this could, for example, include 

geophysical or drain camera surveys that would determine the original layout of the 

Spa Well discharge pipe. It is also possible that diversion of the groundwater flow 

away from the western side of the 1st terrace occurred unintentionally during sewage 

works undertaken in 1980s. Knowledge of the exact location of service pipes within 

the upper extent of the site would also benefit the conceptualisation of groundwater 

flows at this location. If this hypothesis is confirmed, the subsequent mitigation 

measures would include reengineering the pipe layout so they could allow the Spa 

Well discharge to flow in north – north westerly direction. However, this will result in 

a reduction of groundwater flow towards the cold springs (‘filtering ponds’) and is 

likely to impact on the local ecology surrounding the ‘filtering ponds’ which have 

adjusted to present conditions over time. Considering a probable local recharge of 

the cold springs, redirection of the groundwater discharge from the Spa Well might 

cause an increase in seasonal variation in water levels in the ‘filtering ponds’ area 

and could cause seasonal drying of the fen wetland. Hydrochemical changes could 

also occur. Redirection of the outflow from the Spa Well, away from the ‘filtering 

ponds’, will also reduce the volume of water cascading to the second terrace at the 

eastern side and this will affect distribution of water at down gradient terraces. This 

is likely to be compensated by more water flowing on the western side but is likely to 

lead to habitat transformations on a local scale. 

5.5 Field data suggest that the Intel boundary drain does not currently act as a drainage 

channel drawing groundwater from the wet-grassland habitat which has been 

reported to be drying out. Data from a groundwater monitoring well on the Intel site 

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suggests that water from the deeper groundwater system on the Leixlip Spa site 

influences hydrochemistry at that location. 

5.6 The re-wetting of the western side of the first terrace could be potentially achieved by 

reengineering of the surface run-off from the area upgradient from the first terrace. 

This area is currently hard standing with surface runoff flowing both westwards and 

northwards, following the topographic gradient. Rainwater is collected therefore 

either in the Intel drain or infiltrates into the ground at the top of the first terrace. 

This water could be however conserved and directed towards the western parts of 

the first terrace where it could seep into the, currently drying, grassland habitat. 

5.7 With respect to the lowest terrace, which was reported to be drying out, the desktop review 

and interviews undertaken during the study have not revealed any structural changes 

in either local hydrology or hydrogeology. Therefore, the most probable cause of 

these changes is natural habitat transformation resulting from plant growth, 

increased evapotranspiration needs and accumulation of organic matter, which 

subsequently resulted in increased ground level in places. Cessation of grazing may 

have contributed to the vegetation overgrowth of this floodplain. 

5.8 This study was executed in the months of December and January, which is a recharge 

period and groundwater levels are expected to be at their highest. Considering the 

complexity of the Leixlip Spa system combining two groundwater sources, one deep 

and one shallow, the relative contribution of water from these sources may differ 

seasonally and this can further affect hydrochemistry on a local scale. It is advised 

therefore that if it is decided to re-engineer the site in any way, the site’s 

hydrological characteristics when groundwater levels recede (summer) requires 

characterisation. 

5.9 With respect to the future water management strategy for the Leixlip Spa site, the evidence 

collected suggest that alteration of the pipe network at the first, most southern, 

terrace may result in significant changes to the hydrological regime of the ‘filtering 

ponds’, which is difficult to predict quantitatively. Considering that the habitat in the 

vicinity of the ‘filtering ponds’ is of high ecological value, interference with the pipe 

layout does not seem prudent from a hydrological perspective. A management 

strategy is recommended for the floodplain area; however, this should focus on 

controlling plant growth and restricting accumulation of the organic matter. 

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REFERENCES 

Ecoserve (2006) Development of baseline ecological dataset for selected warm springs in Ireland. 

www.ecoserve.ie. Source: National Parks and Wildlife Service 

Gardiner (1980) Ireland. General Soil Map. Second Edition. An Foras Taluntais 

GSI (2007) Dublin Groundwater Body. Summary of Characterization. Unpublished 

Matthews N. (2007) The conservation of the Spa Well, at Louisa Bridge, Leixlip, Co.Kiladare. Report 

to Kildare County Council. 

Mc Connell B., Philcox M., Sleeman A., Stanley G., Flegg A., Daly E. Warren W. (1994). Geology of 

Kildare - Wicklow, Sheet 16, Geological Survey of Ireland 

Meagher N. (1976) Leixlip Spa. Information booklet. 

Minerex (1983) Irish Geothermal Project. Report to Geological Survey of Ireland. 

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FIGURES 

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5 km 

Site Location 

Figure 1 Location of the Leixlip Spa site, (OS LicenceEN0043207) 

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5 km 

Site Location 

Figure 2 Geology in vicinity of the Leixlip Spa site. Source: www.gsi.ie 

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Figure 3 Location map of Intel's groundwater monitoring wells. Source: Intel Ireland. 

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Figure 4 Site location including physio-chemical monitoring points, Leixlip Spa, Co. Kildare 

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EASTON 

LEIXLIP 

Figure 5 Layout of the drainage at Leixlip Spa. Source: Kildare County Council 

CONFEY 

Leixlip 

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Appendix A 

Leixlip Spa: Phase One Report 

Source: Hydro-G, 2007 

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Mr. Simon Wallace 

Senior Executive Parks Superintendent 

Kildare County Council 

Dear Simon 

Re: Preliminary report on the hydrological investigation of Leixlip Spa, Co. Kildare 

Our Ref: 07136_Leixlip Spa_D07 

17 th Dec 2007 

This report has been prepared by Hydro-G to inform Kildare County Council on a progress of the initial assessment of 

hydrological requirements of the Leixlip Spa SAC (code 001398). The report outlines site visits and field work 

investigations carried out to date. An interpretation of results will be provided at a later date when the results of the 

sampling regime are processed and hydrochemical results returned from the laboratory. 

In November 2007 Hydro-G was approached by Kildare County Council to undertake an investigation on the 

hydrological regime of Leixlip Spa, Co. Kildare. The site is located in Leixlip village, along the western side of the Royal 

Canal and between a regional road R 148 and the Rye River. The western boundary of the site is adjacent to the Intel 

factory. The ecological features of the site comprise a wide range of protected species and habitats including 

petryfying tufa springs (SAC Site Synopsis 001398) and alkaline fen habitat. These habitats rely on a stable discharge 

of groundwater saturated with calcite carbonate. Although it is well understood that the rare habitats and species 

found at the Leixlip Spa are dependent on the hydrological regime of the site, the latter is not well understood and very 

limited data on the site hydrology exist at present. Neither quantitative nor qualitative data are available. 

The site is located on a steep limestone ridge which is a remnant of a quarry created in the late 18 th century. The most 

prominent hydrological feature of the site is a warm spring located at the entrance to the site, east of the public 

pathway leading into the site. The spring was discovered in late 18 th century and merits attention due to the relatively 

high temperature and iron content in the water that it discharges. 

To date, Hydro-G conducted two site visits the first on the 2 nd and latter on the 10 th of December 2007. The purpose of 

these visits was to meet with ecologists involved in works on the site, namely Mr Declan Doogue, Mr Brendan 

O’Hanrahan and Ms Evelyn Moorkens. These site meetings facilitated greater understanding of the site’s ecology and 

its hydrological needs for sustaining a healthy habitat. It was established during these visits that ecological features 

have changed throughout the past 20-30 years of ecological monitoring. Specifically, the following two issues had 

been raised: 

• Drying of the upper zone, west of the gravel pathway. Historically this area provided a suitable habitat for wet 

loving grasses and marsh orchids. However Mr Declan Doogue reported this area had not been wet in 

winters within the past 20 years which led to loss of this habitat. 

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• Deterioration of the floodplain quality. Historically, this zone provided a suitable habitat for two rare species of 

molluscs listed in Annex II Habitats Directive, namely Vertigo angustior and Vertigo moulinsiana. While V. 

moulinsiana seem to enjoy current state of the habitat, decreasing numbers of Vertigo angustior suggest and 

on-going unfavourable change of this habitat. Dr Evelyn Moorkens reported increasing density of grasses 

which suggest that the site is undergoing a drying trend. It has also been noted that ground level has 

increased with obvious decomposed organic matter. 

A one day field investigation was carried out by Hydro-G on the 10 th of December 2007. This investigation focused on 

identification and classification of discharge zones within the study site. The site was surveyed for physio-chemical 

parameters, which were recorded at 23 locations. It is apparent from this investigation that water discharges through 

numerous springs and seepages along the S-W transect and at all terraces. Differences in physio-chemical 

characteristics suggest mixing of water from possibly more than one source which will be further interpreted by detailed 

hydrochemical analysis. A total of 10 no. of water samples were collected and were delivered to an accredited 

laboratory for hydrochemical analysis. These samples are currently being analysed for major anions and cations to 

allow for ionic balance determination. Additionally major nutrient levels will be established, including potassium, 

nitrates and ortho-phosphates. Hydro-G will integrate the results of the in situ physio-chemical monitoring programme 

with the results of the hydrochemical analyses and design the next stage of field investigations accordingly. 

This initial site investigation also mapped discharge locations within the site. These will be investigated again during 

the 2 nd site visit, planned for January 2008, to allow for quantitative analysis of flows throughout the site. It is hoped 

that such approach, bound with hydrochemical results will facilitate development a conceptual model of the 

hydrological regime within the site. This model will inform recommendations regarding future monitoring and 

conservation of the site. 

It is apparent that the site has undergone numerous modifications in the past. Modifications within the site include the 

installation of service pipes running through the upper part of the site and construction of a gravel access path. 

Modifications external, but adjacent to the Leixlip Spa site, include the construction of the Intel factory during which 

time large embankments and a drainage ditch were installed alongside the western boundary of the Leixlip Spa site. 

These events must be chronologically structured and compared with the observations of the ecologists. Thus, the 

January 2008 works will include liaison with the site’s ecologists, the site architect, Intel representatives, Kildare 

County Council Water Services, GSI and NPWS. 

We trust that the above is to your satisfaction. Should you wish to discuss any matters please feel free to contact me 

directly on (091) 704841. 

Yours truly 

__________________________ 

Ania Kuczynska B.Eng, M.Sc. 

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Appendix B 

Leixlip Spa - Hydrochemical Analysis 

Source: Hydro-G, 2007/2008 

and Complete Laboratory Solutions, Ros Muc, Co. Galway 

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Temperature, Electric Conductivity and Total Dissolved Solids 

It is evident that water temperatures decrease from the south to north direction, as does the electric 

conductivity. The highest temperatures and ECs were recorded in the Spa Well (monitoring point 9, 

T=13.5-15°C, EC = 1900-2000 µS/cm) and in the outflow from the underground drain (monitoring 

point 8). In the small ‘irony spring’ (monitoring point 7) both water temperature and EC were 

recorded at much lower levels (T = 8-10 °C, EC=~750 µS/cm), which were comparable with the 

Royal Canal conditions (monitoring point 10; T=5.9°C and EC= 617µS/cm; 10/12/2007) and as such 

suggest leakage from the canal. In the next, further down gradient, location in vicinity of the 

‘filtering ponds’ temperatures and ECs varied spatially across relatively small distances and were 

highest in central points in both ponds and lower at more outer locations. It was also noted that 

both the temperature and EC were higher in the Upper Pond than in the Lower and that EC measured 

in the Lower Pond on the second occasion were significantly lower than the first time in December. 

The depth of water in these ponds was investigated to reveal that both ponds are relatively shallow 

with 0.45m depth in the Upper Pond and 0.25m in the Lower Pond. Field investigations suggest that 

these ponds are underlain directly with bedrock. Lower temperature and EC in localised places 

suggest multiple sources of water at these locations, i.e cold springs which mix with warmer water 

coming from the Spa Well. These cold springs are likely to originate in the shallow system which is 

expected to be cooler and less mineralised in comparison to water discharging from the deeper 

system at the Spa Well. Abundance of calcite precipitated in this area and specifically around the 

Lower Pond (monitoring point 18) suggests that groundwater discharges at this location. Integration 

of field data suggests that while the Upper Pond is fed by the Spa Well, the Lower Pond also has 

inputs from the shallow groundwater system. Monitoring results down gradient of the ‘filtering 

ponds’ show temperatures at approximate level of 8-9 °C and EC at around 1750-1850 µS/cm (lower 

than in the Spa Well by ~5 °C and ~200 µS/cm). 

Water flow on the second terrace is by flow along the ground surface. This prevented monitoring of 

physio-chemical parameters. There is an abundance of ad hoc streams wherever topography allows. 

Large depositions of calcite were noted where water drops from the first terrace into the second 

terrace. Increased flow velocities and more dispersed nature of flow increases the release of the 

CO2 from the water, which facilitates higher calcite precipitation rates in this location. 

At the third terrace, there was an abundance of water flow and sources. It is likely that not all 

discharge points were identified. Water was noted to enter from both overland flow and also from 

various sources directly in the ground and bedrock face. Discharge from the bedrock face at the 

eastern side of the terrace (monitoring point 3) had relatively low temperatures (7-8 °C) and high EC 

values at ~ 1600µS/cm. Some deposition of iron was also noted in the opening in the bedrock, 

suggesting high iron content in water. Two other small outflows from the base of the bedrock were 

also noted; one in a shallow pool of water where distinct pieces of tufa are present (‘tufa pond’, 

monitoring point 22) and the second 1m above this pool (too shallow to measure physio-chemistry). 

Physio-chemical characteristics of the ‘tufa pond’ were: T at 6.3 - 8.3°C and EC at ~1480 µS/cm. 

There were two sampling points on the fourth terrace; one on the west side (monitoring point 1) and 

one at the east side (monitoring point 2). On the east side, water forms a stream of 0.15m width and 

0.05m depth and the flow is relatively fast. Deposits of tufa are present in the bed of the stream. 

Measured temperatures were 5.5 - 6.8°C on the west side and 6.6 - 6.9°C on the east side. Electric 

conductivity averaged 1550 µS/cm. 

The drain on the Intel site at the western boundary of the Leixlip Spa site contains water at its 

northern end only, which finishes at the approximate elevation of the Roman Bath. Water in this 

Project No.: 07_136 -28- 

Leixlip Spa


drain (monitoring point 24) was also sampled and showed temperature of 8.34°C and electric EC of 

651µS/cm suggesting water originating from surface runoff. 

With respect to total dissolved solids (TDS), these were found generally high at all terraces ~700- 

1000 ppm and its distribution at different locations is similar to that of electric conductivities. 

pH Level 

All the sampling locations showed alkaline conditions ranging from 7.15 to 9.48 pH on the 10th of 

December 2007 and from 7.29 to 8.74 on the 16th of January 2008. In the Spa Well (monitoring 

point 9) the pH was recorded at 7.15 and 7.99 and was relatively low in comparison to other 

locations. Subsequently, lower pHs were also found in places linked to the underground discharge 

from the Spa Well (monitoring points 8 and 11), where they were measured at 7.27-7.75. The Royal 

Canal (monitoring point 10) sample showed pH of 8.25 and the ‘irony spring’ (monitoring point 7) 

7.29. In the ‘filtering ponds’ (monitoring points 12-17) pH tended to exceed 8 on both occasions. 

Similar pH was found at the entrance to the Roman Bath (point 5) where it was measured at 8.52 

and 8.32 respectively. Higher pH in places associated with cold springs supports the hypothesis that 

this water originates from the shallow system which is in contact with the alkaline bedrock. At lower 

terraces, the pH was generally higher, above 8. 

Chloride 

Results of the hydrochemical analysis show very high chloride levels in the majority of samples, 

which explains relatively high EC and TDS values measured in situ. The highest chloride levels (~350 

mg/l Cl) were recorded at the Spa Well (monitoring point 9) and the discharge from the Spa Well 

(monitoring point 8). The high chloride level in the Spa Well was expected, following the literature 

review. Chloride concentrations decrease in a northerly direction. Samples from the bottom of the 

fourth terrace have Cl concentrations of ~ 260 mg/l Cl. This suggest that water collected at down 

gradient locations from the Spa Well represent mixing conditions of water coming from the Spa Well 

and from other sources (rainfall, surface runoff) that have lower chloride concentrations. Relatively 

low concentration of chloride was found in a sample taken from the Intel drain (monitoring point 24) 

and was found at 65.94 mg/l. This suggests that water gathered in the ditch collects the rainfall 

runoff rather than groundwater that could contribute to wetlands on the site. The high chloride 

concentrations within the study site, abnormal for Irish conditions, are associated with water coming 

from deeper, warmer rocks, where chloride dissolves from certain stratographies. 

Sodium and Potassium 

Sodium concentrations on the Leixlip Spa site range from 158-203 mg/l Na and followed similar 

pattern to that presented by chloride, i.e. the highest concentration was found in the Spa Well 

(monitoring point 9) and these decrease along the south-north gradient. The Intel drain had lowest 

sodium concentration (35 mg/l Na) which suggests that water in the Intel drain does not come from 

the Leixlip Spa site. Potassium concentrations were relatively stable across the Leixlip Spa site (7-10 

mg/l K). Significantly lower concentration of potassium was found in the Intel drain (monitoring point 

24, 2.8mg/l K). 

Calcium and Magnesium 

Calcium and magnesium concentrations were generally similar across the whole Leixlip Spa site. The 

magnesium concentration was significantly lower in the Intel drain (monitoring point 24) with 

comparison to other sampling points. 

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Leixlip Spa


Iron 

Iron concentrations varied throughout the site. An exceptionally high level of 20740 µg/l Fe was 

recorded in the wetland area (centre of the Lower Pond, monitoring point 16). Historical data 

(Meagher, 1976; Matthews, 2007) suggest high iron concentrations in the Spa Well water. Other 

elevated iron concentrations were found in the discharge from the Spa Well (monitoring point 8 - 

830µg/l Fe), above the Upper Pond (monitoring point 11 - 1450 µg/l Fe) and the bedrock face 

(monitoring point 3 -270µg/l Fe). The iron concentration in the Spa Well was found to be 150µg/l. 

Big differences in iron concentrations across the site are not well understood at this stage of the 

investigation. 

Project No.: 07_136 -30- 

Leixlip Spa


Table 2 Results of in situ survey, Leixlip Spa, 10/12/2007 

Monitoring 

Point 

Coordinates 

EC 

µS/cm 

pH 

- 

Temp 

ºC 

TDS 

ppm 

DO 

% 

DO 

mg/l 

1 N53°22.348' W006°30.362' 1594 9.48 5.51 795 91.40 11.61 

2 N53°22.346' W006°30.323' 1533 8.51 6.6 872 90.00 11.23 

3 N53°22.325' W006°30.350' 1671 8.24 8.31 835 70.80 8.29 

4 1742 8.90 6.3 872 85.00 

5 N53°22.300' W006°30.362' 1845 8.52 8.02 921 97.10 11.60 

6 N53°22.297' W006°30.355' 1857 8.12 7.9 928 96.10 11.32 

7 767 7.29 11.62 375 12.30 1.33 

8 2004 7.27 13.18 1006 31.10 3.63 

9 N52°22.249' W006°30.396' 2028 7.15 13.5 1014 23.50 

10 617 8.25 5.9 308 82.00 10.26 

11 N53°22.224' W006°30.579' 1971 7.75 12.62 985 37.00 3.97 

12 N53°22.282' W006°30.363' 1972 8.08 10.57 986 15.10 1.64 

13 1891 8.14 11.1 575 63.50 7.05 

14 N53°22.286' W006°30.365' 1926 8.17 10.43 965 65.80 7.13 

15 N53°22.291' W006°30.356' 1876 7.61 7.86 937 55.70 6.92 

16 N53°22.294' W006°30.354' 1811 8.11 8.01 905 8.50 

17 N53°22.296' W006°30.357' 1716 8.10 7 859 41.89 5.05 

18 1862 7.90 8.8 931 10.00 1.40 

19 N53°22.303' W006°30.340' 1719 8.36 7.89 860 96.40 11.48 

20 N53°22.305' W006°30.347' 1859 8.30 7.73 930 94.30 11.22 

21 1372 8.17 6.31 714 13.60 1.68 

22 N53°22.324' W006°30.348' 1468 8.70 6.34 754 

23 1680 8.36 6.04 843 82.30 10.26 

Table 3 Results of in situ survey, Leixlip Spa, 16/01/2008 

Monitoring 

Point 

Coordinates 

EC 

µS/cm 

pH 

- 

Temp 

ºC 

TDS 

ppm 

DO 

% 

DO 

mg/l 

1 N53°22.348' W006°30.362' 1554 7.85 6.75 777 79.1 9.46 

2 N53°22.346' W006°30.323' 1522 8.34 6.87 761 80.6 9.64 

3 N53°22.325' W006°30.350' 1530 7.84 6.81 765 63.3 7.51 

5 N53°22.300' W006°30.362' 1709 8.32 9.75 854 82.7 9.16 

6 N53°22.297' W006°30.355' 1793 8.11 8.63 1237 87.5 9.94 

7 728 7.29 9.91 364 15.1 

8 1988 7.4 11.02 952 22.4 2.22 

9 N52°22.249' W006°30.396' 1914 7.99 14.82 955 17.3 1.7 

11 N53°22.224' W006°30.579' 1856 7.52 13.74 926 24.3 2.4 

12 N53°22.282' W006°30.363' 1813 8.25 10.52 907 

14 N53°22.286' W006°30.365' 1955 8.07 9.32 977 83.5 9.23 

15 N53°22.291' W006°30.356' 1594 8.16 9.47 796 59.5 6.48 

16 N53°22.294' W006°30.354' 1416 8.27 10.08 708 82.3 9.01 

17 N53°22.296' W006°30.357' 724 8.74 8.74 362 64 7.22 

19 N53°22.303' W006°30.340' 1419 8.1 9.54 710 79.5 8.84 

20 N53°22.305' W006°30.347' 1662 8.18 9.58 831 82.7 9.19 

22 N53°22.324' W006°30.348' 1491 8.31 7.69 747 77.2 9 

24 N53°22.314' W006°30.395' 651 8.34 5.4 325 60.5 7.39 

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Leixlip Spa


Table 4 Results of hydrochemical analysis, Leixlip Spa, 16/01/2008 

Monitoring 

Point 

Alkalinity 

mg/l CaCO3 

Total 

Hardness 

mg/l 

CaCO3 

Ca Mg HCO3 CO3 Na K SO4 

Project No.: 07_136 -32- 

Leixlip Spa 

Fe 

(dissolved) 

Fe 

(total) 

mg/l mg/l mg/l mg/l mg/l mg/l mg/l µg/l µg/l mg/l 

2 225 350.6 94 26 245


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Hydro G Final report - Kildare.ie

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