report hydrogeological impact assessment of waste water

WESTERN BRAND GROUP LTD.

Report

Hydrogeological Impact Assessment of Waste Water Treatment Plant Discharge at Ballyhaunis, Co. Mayo

December 2008

PROJECT NO. : 0130801

ALL COMMUNICATIONS RELATED TO THIS DOCUMENT SHOULD BE DIRECTED TO

Shane O’Neill O’Neill Ground Water Engineering Ltd. Unit B1, M7, Business Park, Newhall, Naas, Tel: 045-895668 Co. Kildare Fax: 045-881705 [email protected]

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Report Issue Form

Version No. : C1

Document Title :

Hydrogeological Impact Assessment of WWTP Discharge at Ballyhaunis, Co. Mayo

Comments :

One copy (plus one .pdf copy): Western Brand Group Ltd.

One copy: O’Neill Ground Water Engineering Ltd.

List Of Authors :

Colin O’Reilly Ph.D.

Client :

Western Brand Group Ltd.

Client Contact Ref : Martin Fox

Signature :

Approved For Issue :

EurGeol Shane O'Neill P.Geo Dip. CECLA

Signature : Date : 22nd December 2008

Version Codes:

A Draft

B Final Draft (may be submitted to client).

C Final Report

The numbering starts at 1, and each version is raised by 1.

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QUALITY CONTROL

The signing of this statement confirms this report has been prepared and checked in accordance with the OGE Peer Review Process.

Project Manager

Colin O’Reilly

Signed

Monday, 02 February 2009 Date

Peer Reviewer

Shane O’Neill

Signed

Monday, 02 February 2009 Date

IMPORTANT INFORMATION ABOUT THIS REPORT

Confidentiality Currency

This document and its contents are confidential and may not be disclosed, copied, quoted or

published unless O’Neill Ground Water Engineering Ltd. (“OGE”) has given its prior

written consent.

OGE accepts no liability for any loss or damage arising as a result of any person other than the

named client acting in reliance on any information, opinion or advice contained in this

document.

This document may not be relied upon by any person other than the client, its officers and

employees.

This document supersedes any prior documents (whether interim or otherwise) dealing with any

matter that is the subject of this document.

Recommendations

OGE accepts no liability for any matters arising if any recommendations contained in this document

are not carried out, or are partially carried out, without further advice being obtained from OGE.

Information

OGE accepts no liability and gives no warranty as to the accuracy or completeness of

information provided to it by or on behalf of the client or its representatives and takes no account of matters that existed when the

document was transmitted to the client but which were not known to OGE until

subsequently.

Outstanding Fees

No person (including the client) is entitled to use or rely on this document and its contents at any time if any fees (or reimbursement of expenses)

due to OGE by its client are outstanding. In those circumstances, OGE may require the return of all

copies of this document.

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O’Neill Ground Water Engineering Ltd. Unit B1, M7 Business Park, Newhall, Naas, Co. Kildare

T: 045-895668 F: 045-875444 Mb: 087-2300933 Email: [email protected]

Directors: S O’Neill (Managing) O O’Neill Registered Office as above. Registered No. 354725. VAT No. 3900664V

HYDROGEOLOGICAL IMPACT ASSESSMENT OF WASTE WATER TREATMENT PLANT DISCHARGE AT BALLYHAUNIS, CO. MAYO

1. Introduction

1.1. O'Neill Ground Water Engineering Ltd. (OGE) were engaged by Western Brand Group Ltd. (WBGL) to

respond to Item 2 of a Request for Further Information from the EPA. This information is required in

support of the Integrated Pollution Prevention and Control (IPPC) licence application under Article 10 of

the Regulations, in accordance with Article 11 (2)(b)(ii) of the EPA (Licensing) Regulations 1994 to

2004.

1.2. OGE personnel involved in the assessment were:

Colin O’Reilly PhD.

EurGeol Shane O'Neill P.Geo Dip. CECLA

Patrick Breheny

1.3. This report details the response by OGE to Item 2 of the information required by the EPA, which reads

as follows:

1.4. “Please provide a comprehensive assessment of the impact of the discharge of waste water from the

WWTP to the Ballyhaunis Turlough. A turlough is considered an outcrop of ground water and they are

prone to periods of low level or disappearance associated with seasonal ground water level fluctuations.

The assessment shall include a full hydrogeological study of the aquifer by a qualified hydrogeologist to

determine the fate and consequences of any pollutants discharged to the ground water/turlough – to

include identification of any vulnerable receptors (e.g. well users, ecosystems, etc.,). Regard should be

had to the joint EPA, DEHLG and GSI publication “Groundwater Protection Schemes” available from the

GSI publications office. Given that a turlough, by its nature, can be classified as ground water, you

must also demonstrate your ability to comply with Council Directive 80/68/EEC on the protection of

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Western Brand Group Ltd. Page 2 of 17 Project No. 0130801

Hydrogeological Assessment Report February 2009

ground water against pollution caused by certain dangerous substances, and Council Directive

2006/118/EC on the protection of ground water against pollution and deterioration.”

1.5. OGE staff visited the site on 8th April, 14th July and 13th November, 2008.

1.6. Information was compiled and collated by OGE from data sourced at the Geological Survey of Ireland

(GSI), Environmental Protection Agency (EPA), Office of Public Works (OPW), National Parks and

Wildlife Service (NPWS), Teagasc and Met Éireann.

1.7. OGE also reviewed certain public databases for the Ballyhaunis area. As OGE are implementing the

ground water aspects of the Water Framework Directive (WFD), 2000/60/EC, in the Western River

Basin District (WRBD), of which Ballyhaunis is a part, OGE have access to very large databases of

hydrogeological and related information. Also being part of the WRBD team, OGE sit on the

Groundwater Working Group, chaired by the EPA, which transposes the WFD into nationally approved

risk assessments and guidelines.

2. Site Description

2.1. The site is located approximately 4km west of Ballyhaunis, County Mayo, south of the R323 road to

Knock, as shown in Figure No. 1.

2.2. The general area is not associated with extensive agriculture, as a result of poorly drained land, which is

gently undulating with topographical elongations on a southeast to northwest orientation. The

processing plant itself is located on a minor ridge at an elevation of approximately 120m OD. The

marsh area which is the focus of this study has an elevation of approximately 110m OD.

Soils

2.3. The soils in the area, according to the General Soils Map of Ireland, are shown in Figure No. 2. The

soils surrounding the site are generally calcareous, typical of the limestone derived tills. The soils are a

mixture of poorly drained and well drained, depending upon elevation, with soils in depressions poorly

drained, and soils on hills and ridges showing improved drainage characteristics.

2.4. The poorly drained soil structure becomes massive at about 30 cm. Below this, soil consistency is

plastic and root penetration is poor. The drainage impedance is attributed mainly to the heavy texture.

The retentive nature of the sub-soil predisposes it to periodic water saturation. Moreover, the slow

surface runoff, typical of gentle slopes, accentuates this condition and a seasonal ‘perched’ water table

can result.

2.5. In areas where near-permanent saturation is occurring, i.e. the marshy area, soils consist primarily of

peat.

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2.6. As elevation increases about the depression, soils become deeper and well drained as the proportion of

well-drained acid brown earth increases. It is usually freely-drained to about 60cm, below which some

drainage impedance is typically evidenced by mottling.

Quaternary Geology

2.7. The quaternary period encompasses the last 1.6 million years and deals with the current soils that were

deposited over the bedrock described above. The Pleistocene (1.6 million years – 10,000 years ago) is

commonly known as the last Ice Age, which was a period of intense glaciation separated by warmer

inter-glacial periods. During the Holocene, i.e. today’s climate, the climate was previously warmer and

wetter approaching that which pertains to today. Glacial deposits resulting from this glaciation period are

widespread and are laid down in a wide range that differs in thickness, extent and lithology.

2.8. Quaternary deposits are shown in Figure No. 3, again with peat subsoils in the lowest areas beneath

the marsh area.

2.9. The primary subsoils in the surrounding area consist of limestone tills. These glacial tills have been

deposited in a drumlin-like formation. Drumlins are features formed from significant amounts of glacial

till, which were shaped by the ice to form small hills. These drumlins can vary in height, resulting in an

undulating landscape.

Bedrock Geology

2.10. The site is underlain by Visean Limestones (Figure No. 4). The Visean Limestone bedrock is a clean

limestone prone to karstification.

2.11. Structural geology shows faults with a southwest to northeast orientation. The nearest major fault is

located approximately 5km southeast of the site, at its nearest point. This structural pattern my extend

to the site.

Aquifer Classification

2.12. The bedrock is classified as a regionally important karstified aquifer with conduit flow (Figure No. 5).

The aquifer classification of karst aquifer with conduit flow would be consistent with Visean Limestone

bedrock.

Karst Features

2.13. The karst database has listed six swallow holes and four turloughs within a radius of 4km to the site

(Figure No. 6). One spring is listed a distance of 3.5km east of the site and adjacent to Ballyhaunis,

namely Ballyhaunis Spring. A swallow hole 0.5km to the south east of the WBGL site has been linked

via tracing to the spring near Ballyhaunis.

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2.14. The presence of swallow holes and turloughs are typical manifestations of karst limestone. The swallow

holes are points in the surface where surface water can drain down into the underlying karst fissure

system. The turloughs are shallow depressions that fill from the bottom up as the ground water rises in

response to recharge events.

2.15. There is no turlough mapped on the GSI database as being in the immediate vicinity of the site.

Similarly there are no turloughs recorded on the National Park & Wildlife database.

2.16. There are no features marked on the Ordnance Survey (OS) map which might indicate a turlough

immediately south of the WBGL site.

2.17. There are two swallow holes mapped at the eastern end of the marshy area adjacent to the site. These

are the only evidence of any karst features in the immediate vicinity of the site.

2.18. The GSI database shows there is a tracer line relevant to one of the swallow holes, showing

connectivity to Ballyhaunis Spring. Hydrochemical sampling is required to establish the fate of any

treated wastewater discharged to the marsh area.

2.19. The GSI karst features database indicates that there is a turlough called the “Greenwood Turlough” to

the northwest of the development. This is not the turlough referred to in the EPA correspondence.

2.20. The GSI’s database indicates four further swallow holes within the vicinity of the site: “Lasanny Swallow

Hole” and another unnamed swallow hole to the southeast of the site, and two unnamed swallow holes

to the northwest.

Vulnerability

2.21. The vulnerability map is presented in Figure No. 7. Vulnerability is high to low (indicating that the

vulnerability mapping for this area is yet to be completed). Areas of extreme vulnerability are

associated with the karst features.

3. Water Balance

3.1. During the site walkover, OGE visited the outfall of the discharge from the site, the receiving waters and

the adjacent marshy area into which the receiving waters drained.

3.2. Based upon local topographical contours, and observations made during site visits, the surface water

catchment boundary applicable to the marsh area has been delineated as shown in Figure No. 1. The

catchment has an area of 0.5 km2 (50 hectares).

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3.3. The area to the north of the processing plant drains to the surface water catchment of the River Mannin

and the area to the south of the processing plant drains to the surface water catchment of the Dalgan

River.

3.4. Rainfall and evapotranspiration data were sourced from Met Éireann. The average annual rainfall

(AAR), based on data from three rainfall stations nearest to the proposed development area, was

determined to be 1165mm (Table No. 1). The two rainfall stations are: Knock GS, 7 km northeast of the

site; Claremorris, 12.5 km southwest of the site, and Loughlinn, 18km northeast of the site.

3.5. The closest synoptic station to the site is Claremorris, 12.5 km southwest of the site. The average

Potential Evapotranspiration (PE) for Claremorris is 409 mm/yr. This value is used as a best estimate of

the site PE. Actual Evapotranspiration is estimated as 389 mm/yr (=0.95 PE). The multiplication factor

allows for the reduction in evapotranspiration during periods when a soil moisture deficit is present. The

multiplication factor used by the GSI is equivalent to 0.95 (Water Framework Directive, 2004).

Table No. 1: 30 year mean monthly rainfall data (in mm) supplied by Met Éireann (long term averages).

Station Grid Ref. Ht (mAOD) Opened Closed Knock M394832 94 1942 1984

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Annual 130 88 102 63 79 73 65 99 105 137 124 128 1193

Station Grid Ref. Ht (mAOD) Opened Closed Claremorris M345739 71 1943

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Annual 121 83 96 62 78 72 63 97 104 126 119 124 1145

Station Grid Ref. Ht (mAOD) Opened Closed Loughlinn M634860 98 1944

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Annual124 87 96 62 78 75 66 98 101 126 120 123 1156

Average 1165

3.6. The Effective Rainfall (ER) for the site is determined from:

ER = AAR – AE.

= 1165 mm/yr – 389 mm/yr

ER = 776 mm/yr

3.7. The catchment to the marsh area occupies an area of 50 hectares. Based on the ER value determined

above, the average volume that is available for runoff on the site foot print is given by:

Site Recharge / Runoff = Area x ER

= (50,000 m2) * (0.776 m/yr)

= 38,800 m3/yr (106 m3/d)

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3.8. Two streams flow into the area of the swallow hole, located at the eastern end of the marsh area

(145854E; 279590N; 97.56 mOD). One emanating from the direction of the marsh area to the west and

one from the east. The discharges were measured on the 30th June 2008 by OGE. Both open drainage

ditches appear to discharge to ground water which is visible at the entrance to the swallow hole. The

velocity and cross sectional area of both streams was measured prior to them discharging into the

swallow hole. The flow (m3) was then calculated using the Mean Mid Point Method (see below). The

channel dimensions were also imported into Flowmaster V6.1, a proprietary software package for a

second method of calculating the flow (see Appendix No. 1). Resulting values are presented in Table

No. 2 below.

Table No. 2: Stream Flow

Point Flow (m3/s) Flow (l/s)

Stream 1 entering swallow hole

0.0028 2.8

Stream 2 entering swallow hole

0.0037 3.7

4. Process Information

4.1. The WBGL operation in Ballyhaunis is a poultry processing facility. The factory processes chickens

prior to nationwide distribution. Two production lines are used for the manufacture of (i) whole birds,

and (ii) Cut-ups (chicken fillets, drumsticks, wings, etc).

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4.2. Freshwater is abstracted from an on-site well. Water supply is supplemented with water from a Local

Group Water Scheme during periods of dry weather. Water is pre-treated with a softener and

chlorination prior to use.

4.3. All blood and offal by-product is removed off-site.

4.4. Washwater and other wastewater streams emanating from the factory process drain network are treated

at the on-site waste water treatment plant. The plant has capacity to treat an average of 450 m3/d.

4.5. Western Brand Group Ltd. was issued a discharge licence by Mayo County Council on 03/09/1997 to

discharge treated trade effluent to waters. Under the terms of the discharge licence issued by Mayo

County Council the volume of discharge shall not exceed 455 m3/day.

4.6. All sludges and other waste are disposed of to the satisfaction of Mayo County Council.

4.7. Treated effluent is discharged via a 200mm diameter pipe to a drainage ditch from which it passes

eastwards toward the marsh area. It is not permitted to flow westwards due to the presence of an

earthen berm in the ditch.

4.8. A staff gauge is installed in this receiving ditch, approximately 30m downgradient of the discharge point.

4.9. A 250mm diameter borehole situated in a field adjacent to the site, under third party ownership, was

used as a monitoring borehole.

5. Ground Water Flow

Well Survey

5.1. The GSI have extensive databases containing borehole information throughout Ireland, on a county by

county basis. For each county, the information is separated in terms of spatial accuracy, with the

divisions being: 1 - 50m; 51 - 500m; 501– 1000m.

5.2. The nearest mapped well to the site within the 1-50m accuracy range is located 5km northwest of the

site. The nearest well to the site, within the accuracy range 51-500m is located 5.3km north. The

nearest well to the site within the accuracy range 501 – 1000m is located 1.6km to the east. The

proximity of the listed wells, combined with the lack of accuracy, limits the applicability of GSI borehole

data for this area.

5.3. A borehole is listed 3km to the east of the site, referring to Ballyhaunis Spring, where bedrock was

noted at 3m below surface. The only other borehole within a distance to the site that could be deemed

informative is situated 7km to the northwest. Bedrock depth was not provided at this point.

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5.4. OGE surveyed an on-site production well (PW1), the nearby monitoring well (MW1), two third party

wells within the vicinity, the turlough at Greenwood, and Ballyhaunis Spring. The groundwater levels

were recorded at these points on 14/06/08, as shown in Table No. 3.

Table No. 3: Well Survey Results on 14/06/08

Point Easting (m) Northing (m) Elevation (mOD)

Water Level (m bgl)

Water Level (mOD)

MW1 145596 279561 103.84 4.55 99.29

PW1 145469 279684 103.44 4.01 99.43

3rd Party Well 1 146411 279344 105.29 0.15 105.14

3rd Party Well 2 145217 280251 97.79 5.41 92.38

Greenwood Turlough 144677 280724 87.81 0 87.81

Ballyhaunis Spring 149123 279201 78.74 0 78.74

Ground Water Contour Map

5.5. The data presented in Table No. 3 were used to construct a ground water contour map as shown in

Figure No. 8. The map shows that the highest ground water level was recorded to the east of the site in

the townland of Knockroe. Water movement from here is toward Ballyhaunis Spring to the east;

northwards, possibly toward the swallow hole located at Ballindrehid; and westwards toward the marsh

area and site processing facility.

5.6. According to ground water gradients, flow from the marsh area is in a northwest direction toward the

WBGL factory, and subsequently toward the turlough and swallow holes at Greenwood (see Figure No.

6).

5.7. Whilst the groundwater contour map is a useful exercise, the groundwater flow lines presented are not

necessarily a true representation of ground water flow in the area due to the nature of the karst geology

in the region. The GSI tracer test showed surface water from the marsh area to re-emerge, via a

swallow hole, at Ballyhaunis Spring. This shows that it is difficult to accurately model ground water flow

patterns in the area. Long-term ground water level monitoring, along with hydrochemical investigation,

may provide further insight into the ground water flow patterns.

Groundwater Level Monitoring

5.8. A data logger was installed in MW1 to measure depth to groundwater on a continuous basis over 6

months. This data logger was removed by a third party some time between July and November 2008,

resulting in a loss of data for this period.

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5.9. OGE also installed a data logger within a temporary standpipe to measure the depth of water in the

marsh area on a continuous basis over 6 months.

5.10. A third data logger was used to measure atmospheric pressure.

5.11. The groundwater level data from MW1 are presented in Figure No. 9 along with the water level in the

marsh for a 1 month period in June-July 2008.

5.12. The data for MW1 highlighted relatively sharp fluctuations in ground water level on a weekly basis.

Following further enquiries, it was apparent that these fluctuations were a reaction to pumping

frequencies at PW1. Pumping occurs at PW1 between Monday and Friday, with recovery occurring in

the same well at weekends. Assuming pumping rates and durations are consistent, a gradual decline in

ground water level was also observed over the monitoring period. This is likely due to decreased

recharge from precipitation over the summer.

95.00

96.00

97.00

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103.00

104.00

105.00

18/06/08 21/06/08 25/06/08 28/06/08 01/07/08 05/07/08 08/07/08 11/07/08

Date/Time

Wat

er L

evel

(mO

D)

MW1Marsh

Figure No. 9: Water Level Monitoring Data June-July 2008

5.13. The groundwater level data in the marsh area are presented in Figure No.10 along with the water level

in MW1, for a 6 month period in June-November 2008.

5.14. The data showed that the water level in the marsh was relatively unchanged over the monitoring period.

The range of water levels recorded in the marsh was 98.63 – 98.76 mOD. No trend in water levels was

observed within this small range.

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95.00

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102.00

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105.00

18/06/08 05/07/08 22/07/08 07/08/08 24/08/08 10/09/08 26/09/08 13/10/08 30/10/08

Date/Time

Wat

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evel

(mO

D)

MW1Marsh

Figure No. 10: Water Level Monitoring Data June-November 2008

5.15. The water levels in the marsh area did not rise and fall in response to pumping at PW1, nor did they

show any longer term trend. The absence of an observed relationship shown by the monitoring data

between MW1 and the marsh would suggest that there is little connectivity between surrounding ground

water levels and water level in the marsh.

5.16. Rather than being controlled by groundwater levels, the water level in the marsh is possibly controlled

by the swallow hole at its most eastern edge. The swallow hole acts as an overflow mechanism in

response to the volume of precipitation entering the catchment.

5.17. The long term monitoring of water levels in the area suggest that the marsh area in question is not a

turlough but an overflow exit.

6. Hydrochemistry data

6.1. Monthly sampling was carried out at four monitoring points:

6.1.1. Treated effluent at discharge point (145555E; 279755N)

6.1.2. Standing water in the ditch downgradient of discharge point, adjacent to staff gauge (145573E;

2279755N), referred to as “6.75 area”, 25m downstream of discharge point;

6.1.3. Water entering swallow hole, referred to as “marsh area”, 320m downgradient of discharge

point;

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6.1.4. Water emerging at Ballyhaunis Spring, 4000m from discharge point.

6.2. The groundwater monitoring results are presented in Table No. 4. Certificates of Analysis are provided

in Appendix No. 1.

Table No. 4: Hydrochemistry data (concentrations in mg/l)

Parameter 04/06/08 09/07/08 13/08/08 24/09/08 26/11/08 Surface Water Regs.

(1989)

Final Effluent

pH 7.5 6.9 7.5 7.4 7.3 5.5 – 9.0

Ammonium (as NH3-N)

1.167 0.145 15.501 13.642 31.83 0.2

BOD 29 15 6 11 63 5

Suspended solids 17 6 11 9 65 50

Ortho-P 9.453 14.122 3.270 4.303 0.317 0.03†

OFG <1 <1 <1 <1 <1

COD 66 35 33 74 136 40

6.75 Area

pH 7.5 6.9 6.8 6.9 7.6 5.5 – 9.0

Ammonium (as NH3-N)

1.149 0.607 1.922 1.218 24.889 0.2

BOD <2 16 20 37 28 5

Suspended solids 14 8 23 63 33 50

Ortho-P 7.74 7.93 6.11 5.435 0.400 0.03†

OFG <1 <1 <1 <1 <1

COD 10 41 39 108 69 40

Marsh Area/Swallow Hole

pH 6.9 6.7 6.7 6.5 7.5 5.5 – 9.0

Ammonium (as NH3-N)

0.582 0.028 0.008 <0.005 0.636 0.2

BOD <2 <2 6 <2 <2 5

Suspended solids 13 6 27 <2 <2 50

Ortho-P 0.942 0.078 0.153 0.071 0.239 0.03†

OFG <1 <1 <1 <1 <1

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Parameter 04/06/08 09/07/08 13/08/08 24/09/08 26/11/08 Surface Water Regs.

(1989)

COD <10 <10 <10 14 20 40

Ballyhaunis Well

pH 6.8 6.7 6.6 6.7 5.5 – 9.0

Ammonium (as NH3-N)

<0.01 0.156 <0.005 <0.005 0.2

BOD <2 <2 6 <2 5

Suspended solids 2 <2 <2 <2 50

Ortho-P 0.055 0.054 0.131 0.057 0.03†

OFG <1 <1 <1 <1

COD <10 <10 11 15 40

† Interim Statutory Standards for Rivers

7. Groundwater Impact Assessment

7.1. The EPA has requested a hydrogeological risk assessment of the impact of the discharge of waste

water from the WWTP to the local identified receptors. This risk assessment approach adopted utilised

the Source-Pathway-Receptor model.

7.2. In the case of WBGL, the Source is the treated effluent discharging to the receiving waters.

Hydrochemical results have shown that the majority of the time the WWTP is capable of adequately

treating wastewater prior to discharge. However, on intermittent occasions the WWTP has not treated

wastewater to satisfactory levels. This is to be addressed as part of a review of the WWTP, and a long

term monitoring programme of the discharge to ensure that the WWTP is consistently achieving the

discharge standards outlined in the IPPC licence.

7.3. Orthophosphate concentrations in the most recent sample (26/11/08) were below the 0.5 mg/l limit set

out under the discharge licence as issued by Mayo County Council. Ongoing monitoring of the

discharge will show if this is an ongoing improvement. Ammonia concentrations in the discharge only

satisfied the 0.5 mg/l limit set out under the discharge licence in the July round of sampling. BOD

concentrations satisfied the 10 mg/l limit set out in the discharge licence in the August round of

sampling. Suspended solids concentrations were below the 10 mg/l discharge licence limit during the

July and September sampling rounds. Fats, oils and greases satisfied the limits of the discharge

licence in all samples. It is noted that different parameters are being removed adequately prior to

discharge with different efficiencies, at different times. The problems causing elevated parameter

concentrations will be identified as part of a comprehensive review of the WWTP.

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7.4. The Pathway is considered to be the body of water receiving the discharge. It is disputed as to whether

this body of water is a turlough or otherwise. The area in question resembles a poorly drained marsh

area/wetland. OGE carried out a monitoring programme of water levels in this area, and

simultaneously, ground water levels in a nearby borehole.

7.5. OGE defined the surface water catchment to this area, and performed a well survey of ground water

boreholes in the locality. The marsh area in question is located in a depression within a surface water

catchment of approximately 50 hectares. Ground water contours showed ground water flow to be in a

northwest direction toward Greenwood Turlough. A tracer test performed by the GSI showed surface

water from the marsh area to re-emerge, via a swallow hole, at Ballyhaunis Spring.

7.6. Groundwater level monitoring showed that the water levels in the marsh area were relatively static and

did not show any longer term trend. The lack of a relationship shown by the long term monitoring data

between MW1 and the waterbody would imply that there is little connectivity between surrounding

ground water levels and water level in the waterbody.

7.7. Rather than being controlled by groundwater levels, the water level in the marsh area is possibly

controlled by the swallow hole at its most eastern edge. The marsh area is also not prone to drying up

during the summer. The swallow hole acts as an overflow mechanism in response to the volume of

precipitation entering the catchment. A detailed study of the swallow hole could not be carried out as

part of this study due to access issues.

7.8. As per Item 2 of the correspondence issued by the EPA, “a turlough is considered an outcrop of ground

water and they are prone to periods of low level or disappearance associated with seasonal ground

water fluctuations.”

7.9. The marsh area in question would therefore appear to be more akin to a poorly drained depression than

to a turlough.

7.10. The classification of the marshy area has implications for the risk assessment and the potential impact

of the fully treated effluent. Turloughs have characteristic hydraulic regimes and ecology. In particular

turloughs have distinct vegetation types.

7.11. As the marsh area is receiving the treated effluent discharge, it is considered to be a pathway. The

swallow hole and the destination of this transported water is considered to be the receptor, along with

underlying groundwater, which would be receiving a quantity of water from vertical percolation through

the marsh area.

7.12. The ground water is the final receptor and the swallow holes at the eastern end of the marshy area have

been linked by tracer studies to the spring in Ballyhaunis. This means that the spring is a potential

receptor.

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7.13. OGE undertook a six month monitoring programme to assess the potential impact upon the Ballyhaunis

Spring. The hydrochemical characteristics of the final fully treated effluent, the receiving water as it

enters the marshy area and is fully mixed, the water as it leaves the marshy area at the south western

end and the spring in Ballyhaunis that has been linked by tracing to the swallow holes in the vicinity of

the marshy area, were measured as part of this risk assessment.

7.14. The trends of change in concentration of ammonia and orthophosphate in water, against distance from

discharge point, are presented in Figure No. 11 and Figure No. 12, respectively.

0

2

4

6

8

10

12

14

16

0 25 320 4000

Distance from discarge point (not to scale)

Orth

o-P

Conc

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(mg/

l)

JuneJulyAugSeptNov

Figure No. 11: Change in orthophosphate concentration in samples against distance from discharge point

0

5

10

15

20

25

30

35

0.1 25 320 4000

Distance from discarge point (not to scale)

NH3

-N C

once

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(mg/

l)

JuneJulyAugSeptNov

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Figure No. 12: Change in ammonia concentration in samples against distance from discharge point

7.15. The data presented in Figure No. 11 shows that orthophosphate is assimilated within the marsh area,

and concentrations decrease as distance from the discharge point increases. Orthophosphate

concentrations in the discharge exceed the Surface Water Regulations (1989) and this will need to be

addressed under a review of the waste water treatment system.

7.16. The data presented in Figure No. 12 show a similar trend in ammonia concentrations, which decrease

as distance from the discharge point increases. However, ammonia concentrations in the discharge are

elevated and will also need to be addressed as part of a review of the wastewater treatment system.

Out of four samples taken at Ballyhaunis well, ammonia concentration exceeded that permitted under

the Surface Water Regulations (1989) on only one occasion. Ammonia concentrations in water entering

the swallow hole satisfied the Surface Water Regulations (1989) in three of the five samples taken. The

exceedances are likely due to fluctuations in ammonia concentration in the discharge.

7.17. Extremely elevated ammonia concentrations recorded in November at the sampling location 25m

downgradient of the discharge would infer that the wastewater treatment plant was not functioning

adequately at this time.

7.18. The hydrochemical data shows that the water quality at Ballyhaunis Spring is not strongly correlated to

the quality of final treated effluent being discharged from the factory premises. The flow of surface

water input from the two streams entering the swallow hole may facilitate a dilution effect on the outflow

from the marsh area also. This would suggest that while there may be a degree of connectivity between

the swallow hole and Ballyhaunis Spring, the swallow hole is not the sole source of water to the spring.

7.19. The marsh itself is functioning as a wetland or reed bed system. As the water moves from the

discharge point across the area of the marsh, to the swallow hole, chemical constituents of the

discharge are being removed by natural processes, typical of a wetland system.

7.20. Providing issues with the consistency of the discharge quality from the WWTP are resolved, the marsh

area will continue to serve as a tertiary treatment system. Continuance of the water quality monitoring

programme will provide evidence of this.

8. References

GARDINER, M.J. AND RADFORD, T. 1980. Soil Associations of Ireland and their Land Use Potential. Teagasc,

Johnstown Castle, Wexford.

GSI. 1999. Geology of South Mayo, Sheet 11. Geological Survey of Ireland.

NPWS. 2008. National Parks and Wildlife Service. www.npws.ie on 13th November 2008.

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Western Brand Group Ltd. Project No. 0130801

Hydrogeological Assessment Appendices December 2008

APPENDIX NO. 1

LABORATORY CERTIFICATES

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report hydrogeological impact assessment of waste water

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