OFFALY COUNTY COUNCIL

EDENDERRY SEWERAGE IMPROVEMENT SCHEME

PRELIMINARY REPORT

VOLUME I

For inspection purposes only. Consent of copyright owner required for any other use.

Nicholas O’Dwyer Ltd., Offaly County Council, Consulting Engineers, County Buildings, Nutgrove Office Park, Charleville Road, Nutgrove Avenue, Tullamore, Dublin 14. Co. Offaly. Revision B – June 2005

PROJECT NO. 20290 Prepared by Approved by Issued by Initials Date Initials Date Initials Date Revision Reason for Revision GM 12/12/03 GM 12/12/03 JP 12/12/03 A Incorporate Client comments. GM 13/12/04 GM 13/12/04 JP 13/12/04 B Final Revisions GM 13/06/05 GM 13/06/05 JP 13/6/05 C D

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CONTENTS

VOLUME I

1. INTRODUCTION & SCOPE OF WORK 1 1.1 General 1 1.2 Scheme Objectives 1 1.3 Terms of Engagement 1 1.4 Scope of Work 3 1.5 Staging of Scheme 4 1.6 Environmental Impact Statement 4 1.7 Scheme Catchment Area 4 1.8 Importance of the Scheme 5

2. DATA COLLECTION AND EXISTING CONDITIONS 6 2.1 Wastewater Disposal and Population Served 6 2.2 Wastewater Generation and Pollution Load 6 2.3 Stormwater and Groundwater Infiltration 6 2.4 Wastewater Disposal Facilities 6

For inspection purposes only. 2.5 Receiving Waters Consent of copyright owner required for any other use. 7

3. EXISTING SYSTEM 8 3.1 General 8 3.2 Edenderry Wastewater Collection Network 8 3.2.1 Introduction 8 3.2.2 Foul / Combined and Surface Water Sewers 9 3.2.3 Existing Pumping Stations 11 3.2.4 Existing Overflows 15 3.3 Hydraulic Modelling of Existing System 17 3.3.1 General Methodology 17 3.3.2 Construction of Edenderry Hydraulic Model 20 3.3.3 Hydraulic Model Calibration 22 3.3.4 Hydraulic Analysis of Existing System 23

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3.4 CCTV and SUS 2000 Survey 25 3.5 Existing Wastewater Treatment Plant 28 3.5.1 Introduction 28 3.5.2 Existing Wastewater Treatment Works Overview 28 3.5.3 Operation and Maintenance 31 3.5.4 Flow and Load Survey 32 4. POPULATION PROJECTIONS, WASTEWATER FLOWS AND STAGING OF THE SCHEME 38 4.1 General 38 4.2 Population Projections 38 4.3 Low Growth Trend 39 4.4 Medium Growth Trend 44 4.5 High Growth Trend 46 4.6 Phasing of the Works 48

5. EFFLUENT QUALITY 50 5.1 Receiving Waters 50 5.2 Effluent Quality 50 5.3 Urban Wastewater Treatment Regulations 51 5.4 River Boyne Water Quality Management Plan (WQMP) 52 5.5 Aspects of Boyne Catchment Hydrology 53 For inspection purposes only. Consent of copyright owner required for any other use. 5.6 River Boyne Water Quality 54 5.7 Required Effluent Standards 55 5.8 Recommended Effluent Standards for the River Boyne at Edenderry 58 5.9 Summary of Effluent Standards Adopted for Discharge to the River Boyne at Edenderry 60 5.10 Discharge Options to the River Boyne 60

6. WASTEWATER TREATMENT OPTIONS 61 6.1 General 61 6.2 Treatment Plant Capacity 62 6.3 Treatment Process Selection 63 6.3.1 Process Option 1 (Extended Aeration Plant) 64 6.3.2 Process Option 2 (SBR) 66

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6.3.3 Process Option 3 (Membrane Bioreactor) 67 6.3.5 Conclusions 68 6.3.6 Recommendations 69 6.4 Tertiary Filters 69 6.5 Treatment and Disposal of Solids Residues 70 6.5.1 Screenings & Grit 70 6.5.2 Sludge 70 6.6 Augmentation of Flow and Balancing of Effluent Flow 71

7. WASTEWATER COLLECTION NETWORK PROPOSALS 72 7.1 General 72 7.2 Hydraulic Model 72 7.3 Methodology 72 7.4 Upgrading of Pumping Stations 75 7.4.1 General 75 7.4.2 Connyborough Pumping Station 76 7.4.3 Clonmullen Lane Pumping Station 77 7.4.4 Carrick Road Pumping Station 77 7.4.5 Derrycorris Pumping Station 78 7.4.6 Corkery Lane Pumping Station 78 7.4.7 Killane Road Pumping Station 78 7.4.8 Blundell Wood Pumping Station 79 7.4.9 Rising Mains 79 For inspection purposes only. 7.5 Removal of OverflowsConsent of copyright owner required for any other use. 80

7.6 Sewer Upgrading 81 7.7 Extensions to Existing Collection System 85 7.8 Sewer Repair and Rehabilitation Works 86 7.9 Storm Handling Facilities at Wastewater Treatment Works 86 7.10 Summary of Proposed Measures 90

8. DESIGN PARAMETERS AND LAYOUT OF WASTEWATER TREATMENT PLANT 93 8.1 Summary of Design Parameters 93 8.2 Preliminary Layout of the Wastewater Treatment Works 93 8.3 Stormwater Tanks 94

9. SEPTICITY AND ODOUR CONTROL 95

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9.1 General 95 9.2 Physical Conditions for Septicity 95 9.3 Preventive Measures 97 9.4 Recommendations 98

10. STORMWATER NETWORK 99 10.1 General 99 10.2 “Assessment of Surface Water Drainage in Edenderry” 99 10.3 “Upper Boyne Flood Study” 100 10.4 Future Development 100 10.5 SUDS – Sustainable Urban Drainage Systems 102 10.5.1 General Description 102 10.5.2 Initial Data Required 103 10.5.3 Design Strategy for Drainage System 104 10.5.4 SUDS Conclusions 105 11. COST ESTIMATES 107 11.1 Preparation of Cost Estimates 107 11.2 Wastewater Treatment Works Expansion 107 11.2.1 Estimated Cost of Phase I 107 11.2.2 Estimated Cost of Phase II 107 11.2.3 Estimated Cost of Phase III 107 For inspection purposes only. 11.2.4 Summary ofConsent Estimated of copyright Waste owner requiredwater for anyTreatment other use. Works Costs 108

11.3 Annual Operation and Maintenance Costs 109 11.4 Improvements to Existing Wastewater Collection Network 109 11.4.1 Estimated Cost of Sewer and Manhole Rehabilitation 109 11.4.2 Estimated Cost of New and Upgraded Sewers 110 11.4.3 Estimated Cost of New Rising Mains 111 11.4.4 Estimated Cost of New / Upgraded Pumping Stations 111 11.4.5 Estimated Costs of Removing Combined Storm Overflows 113 11.4.6 Summary of Estimated Wastewater Collection Network Costs 113 11.4 Proposed Extensions to Wastewater Collection Network 114 11.5.1 Overall Summary Costs of Edenderry Sewerage Improvement Scheme 115

12. PROCUREMENT STRATEGY AND IMPLEMENTATION 121 12.1 Benefits of Traditional Procurement vs. DB/DBO Contracts 121 12.1.1 Design and Build 122

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12.1.2 Operating 122 12.1.3 Programme 123 12.2 Procurement Strategy 123

13. CONCLUSIONS AND RECOMMENDATIONS 124 13.1 Conclusions 124 13.2 Recommendations 125

VOLUME II

APPENDICES Collection Network - Hydraulic Model Calibration Report

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LIST OF DRAWINGS

20290/01 Edenderry Development Boundary 20290/02 Wastewater Collection Network - Existing 20290/03 Wastewater Treatment Works - Existing 20290/04 Wastewater Treatment Works Outfall Pipeline - Existing 20290/05 Flow and Rainfall Logger Locations 20290/06 CCTV / SUS Survey Results 20290/07 Existing Collection System Hydraulic Analysis - 1 Year Return Period 20290/08 Land Use Zoning Map (2003) 20290/09 Proposed Wastewater Treatment Works Extension - Option 1 Layout 20290/10 Proposed Wastewater Treatment Works Extension - Option 1 Sections 20290/11 Proposed Wastewater Treatment Works Extension - Option 2 Layout 20290/12 Proposed Wastewater Treatment Works Extension - Option 2 Sections 20290/13 Proposed Wastewater Treatment Works Extension - Option 3 Layout 20290/14 Proposed Wastewater Treatment Works Extension - Option 3 Sections 20290/15 Details of Existing & Proposed Pumping Station at Connyborough 20290/16 Details of Existing & Proposed Pumping Station at Killane Road

20290/17 Collection System H ydraulic For inspection Analysispurposes only. Following Proposed Upgrading of Consent of copyright owner required for any other use. Pumping Stations & Removal of Combined Sewer Overflows 20290/18 Proposed Sewer & Rising Main Upgrades 20290/19 Plan of Proposed Relief Sewer 20290/20 Proposed Foul Relief Sewer - Longitudinal Section 20290/21 Plan of Proposed Foul Sewers & Surface Water Scheme on Rhode Road & St. Mary’s Street. 20290/22 Proposed Foul Sewers - Longitudinal Sections - Rhode Road - ‘A’ Line 20290/23 Proposed Foul Sewers - Longitudinal Sections - St. Mary’s Street - ‘A’ Line 20290/24 Surface Water Scheme - Longitudinal Sections - ‘B’ Line and ‘C’ Line 20290/25 Proposed Combined Sewer on St. Mary’s Road - ‘D’ Line 20290/26 Proposed Foul Sewer & Rising Main at Connyborough - ‘E’ Line 20290/27 Land Use Zoning Map & Proposed Wastewater Collection System

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1. INTRODUCTION & SCOPE OF WORK

1.1 General

Edenderry is a medium sized town situated in East Offaly close to the border with North-West Kildare. The town is situated closed to the upstream section of the River Boyne which forms the border between the two counties.

In the 2003 Offaly County Development Plan, Edenderry is designated as a District Centre along with Tullamore, the county town and Birr. Edenderry’s role is further defined by its location within the Dublin commuter belt. The N4 National Primary Route is accessible from the town via the R401 and R402 regional roads which join the N4 at Kinnegad and Enfield respectively. The Edenderry Town Plan 1999 and its Variation of 2001 aims to facilitate an increased regional role for Edenderry by seeking to improve the link with Dublin and its designation as a District Centre.

1.2 Scheme Objectives

The Edenderry Sewerage Improvement Scheme provides for the immediate and long term improvement and expansion of the existing scheme of collection, treatment and

disposal of wastewater generated For inspection from purposesthe town only. of Edenderry and its environs. Consent of copyright owner required for any other use.

1.3 Terms of Engagement

This Report has been prepared in accordance with the original Brief prepared by Offaly County Council in May 2002 and subsequent letter of appointment of 4th April 2003.

The Scope of Work as set out in the brief and agreed with Offaly County Council is summarised below:

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1. Examine existing records of the foul and surface water collection systems and advise on their condition and any remedial action required. Provide for separate foul sewers for any new development.

2. Detail any works required to upgrade the capacity of the existing foul network either through stormwater separation or the provision of new sewers and/or pumping stations.

3. Detail any extensions required to the network to serve the development needs of the town.

4. Submit proposals for dealing with infiltration and damage to existing sewers (storm sewers to be designed for a return period of 5 years).

5. Examine existing stormwater discharges and make recommendations on any alterations or modifications required. Provide general recommendations in relation to the management of surface water runoff.

6. Determine projected flows from Domestic, Commercial, Institutional and Industrial Users over a 25 year horizon.

For inspection purposes only. Consent of copyright owner required for any other use. 7. Identify the relevant characteristics of the waste water to be treated.

8. Examine the existing treatment works site and advise on the feasibility of extending it.

9. Determine the effluent quality parameters required taking into account the quality of the receiving waters.

10. Examine the performance of the existing treatment works.

11. Make a comparison of different treatment options which would be suitable from an environmental and economic standpoint and produce an indicative layout.

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12. Advise on phasing of the expansion of the WWTW’s.

13. Advise on Environmental Standards to be adopted for the proposed development.

14. Prepare detailed estimates for the construction costs and advise on strategy of the scheme.

15. Recommend the most cost-effective solution with reference to the application of value engineering principles.

16. Prepare a Polluter Pays Report in line with current Water Pricing Policies.

1.4 Scope of Work

This Section describes the particular scope of work used in the preparation of this Preliminary Report prepared in accordance with the terms of engagement.

To address the Brief the Report includes the following components:

For inspection purposes only. i) Current and futureConsent population of copyright owner projections required for any to other the use. year 2028.

ii) Current and future effluent loads for domestic and industrial contributions.

iii) Review of the Development Plan together with a review of possible stage development of the scheme based on projected population equivalents and loads.

iv) Review of flows and assimilative capacity of the River Boyne.

v) Review of storm overflows and pumping stations.

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vi) Review of the treatment process and treatment standards selected in the light of current EC requirements and regulations.

vii) Review of sludge treatment and disposal options in line with the current Sludge Strategy Plan for Co. Offaly.

viii) Preparation of Preliminary Plans and Drawings of pipelines, pumping stations and treatment works for inclusion in the Report.

ix) Preparation of a Preliminary Report.

1.5 Staging of Scheme

The Preliminary Report estimates the needs and makes recommendations for the provision of wastewater collection and treatment facilities for the Scheme horizon of 25 years to the year 2028. The development under this report is envisaged in three Phases, Phase I to the year 2010 and Phase II to the year 2015 and Phase III to the year 2028.

1.6 Environmental Impact Statement

For inspection purposes only. Consent of copyright owner required for any other use.

In view of the estimated future population equivalents of greater than 10,000 an Environmental Impact Statement shall be required for the expansion of the Wastewater Treatment Works. The EIS shall be prepared as a separate document based on the projected population equivalents, effluent standards and indicative layouts set out in this Preliminary Report.

1.7 Scheme Catchment Area

The Scheme Catchment Area covers Edenderry and its environs and is all within the boundary of Offaly County Council. Drawing No. 20290/01 shows the Development Boundary of Edenderry as set out in the Offaly County Development Plan 2003.

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1.8 Importance of the Scheme

The scheme is important in respect of improving the quality of the receiving waters to which the treated wastewater effluent from the catchment area is discharged. This has a direct bearing on the collection, treatment and disposal facilities to be provided for under the scheme.

The wastewater treatment works is currently at maximum capacity and therefore the overall growth and expansion of the town is being restricted due to inadequate treatment facilities. Similarly elements of the collection system are at maximum capacity particularly in times of stormflows thus also limiting growth. As Edenderry has undergone significant increased levels of pressure for residential and commercial development in recent years the overall system is imposing a severe constraint on the economic growth and sustainability of the catchment area. As development pressures are expected to continue for the foreseeable future due to the strategic location of the town an upgraded sewerage scheme is of critical importance to ensure the proper development of the area.

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2. DATA COLLECTION AND EXISTING CONDITIONS

2.1 Wastewater Disposal and Population Served

Data has been collected on the current population served by the sewerage system in Edenderry and the future population projections are based on these figures.

Data on the present wastewater collection system serving the population in Edenderry and its environs was collected and sample verification has been undertaken in the field.

2.2 Wastewater Generation and Pollution Load

The present pollution load being discharged to the existing works is estimated to be

466 kg BOD5 /day. The present dry weather flow (DWF) is estimated at 1,850 m3/day. Data on the influent and effluent is discussed in Section 5 of this Report. From examination of the data, it is evident that the existing plant is at maximum capacity or slightly overloaded particularly in terms of pollutional load. The plant is a conventional extended aeration process, designed for a population equivalent of 7,000 P.E. with a BOD load of 420 kg/day (60 g/h/day) and a hydraulic load of 1,750 3 For inspection purposes only. m /day (250 l/h/day). Consent of copyright owner required for any other use.

2.3 Stormwater and Groundwater Infiltration

The existing collection network is generally a combined network. Surcharging and flooding occur in some areas at normal rainfall conditions each year. A review of the stormwater network is carried out in Section 10 of this Report.

2.4 Wastewater Disposal Facilities

Wastewater disposal facilities exist for the town of Edenderry. Details of these existing facilities were collected and examined and are presented in Section 3 of this report.

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2.5 Receiving Waters

Data in respect of the receiving waters of the River Boyne was obtained from the Water Quality in Ireland 1998-2000 published by the Environmental Protection Agency and the Water Quality Management Plan published in November 1997.

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3. EXISTING SYSTEM

3.1 General

The Edenderry Sewerage Scheme consists of a wastewater collection system and treatment works with an outfall pipeline to the River Boyne.

The Wastewater Collection System serving the Edenderry Urban Catchment has been in operation for a number of years. The capacity and structural condition of the system is discussed in this section of the Report.

The Wastewater Treatment Works has recently been expanded to cater for a population equivalent of 7,000 p.e. A description of the process involved together with current operational details is provided in this section of the Report.

The layout of the existing sewer system for Edenderry together with sewer system for Edenderry together with details of the location and layout of the existing Wastewater Treatment Works are shown on Preliminary Report Drawing Nos. 20290/02, 20290/03 and 20290/04.

For inspection purposes only. 3.2 Edenderry WastewaterConsent Collection of copyright Networkowner required for any other use.

3.2.1 Introduction

The Edenderry catchment is served by an interconnecting foul/combined sewer system gravitating to the wastewater treatment works located off the Rhode Road. A number of pumping stations, serving areas in the periphery of the town, feed into the network.

The town is also served by some six separate surface water sewer networks, discharging to ditches and streams.

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There are a number of overflows from the foul/combined system into the surface water system.

An overall Plan of the Edenderry Wastewater Collection Network is shown on Drawing No. 20290/02.

3.2.2 Foul / Combined and Surface Water Sewers

The existing town of Edenderry is served by a number of arterial gravity sewers draining towards the town centre as shown on Drawing No. 20290/02. Pumping stations transfer flows from the low-lying areas at the edge of the town into the town centre. The main sewers are described hereunder. Sewers which were monitored as part of the flow survey are discussed in Section 3.3.

1. St. Mary’s Street A 150/225 mm foul/combined sewer along St. Mary’s Street from the south west, turning at St. Francis Street. This sewer collects flows from Killane Pumping Station and from the primary and secondary school along St. Mary’s Road. Foul effluent from a partially complete housing development called The Sycamores is also pumped to the St. Mary’s Road sewer. Most of its catchment

is combined apart from Fora inspectionsmall purposessection only. of surface water sewer near the town Consent of copyright owner required for any other use. centre.

2. JKL Street A 225 mm foul/combined sewer along JKL Street from the Blundell Wood Estate and connected to the main collector on St. Conleth’s Road. This sewer serves the Blundell Wood Estate as well as many of the commercial properties in the town centre. A separate surface water sewer drains part of the Blundell Wood Estate and a portion of JKL Street.

3. Fr. Murphy Street A 225 mm foul/combined sewer along Fr. Murphy Street to the south east which collects flows from the Greenwood Park housing estate as well as other properties to the south east of the town. Derrycorris pumping station pumps to

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the head of the sewer. The sewer runs along the backs of the houses to the north of Fr. Murphy Street and into Fr. Kearns Street.

The Greenwood Park Estate is also served by a separate surface water network which outfalls into a stream behind No. 18 Fr. Murphy Street.

An overflow on the foul/combined system discharges to the surface water network during heavy rainfall.

4. Dublin Road A 225mm foul/combined sewer along Dublin Road to the east which outfalls into Connyborough Pumping Station. This in turn pumps into the sewer on Fr. Kearns Street. The Dublin Road Sewer collects flows from all of the properties along Dublin Road as well as the new Connyborough housing estate. The area is partially combined as there is no evidence of any surface water drainage.

5. Clonmullen A 225mm foul/combined sewer draining to Clonmullen Pumping Station which pumps into the main outfall sewer. This sewer collects from the mainly ribbon development as well as the new apartment blocks in the area. The area is

partially drained by a Forseparate inspection purposes surface only. water network so there would be Consent of copyright owner required for any other use. negligible surface water contribution to the foul sewer.

A new pumping station has recently been constructed at the site of a new residential development. This pumping station currently accepts effluent from the recently completed properties in this development and pumps effluent to the existing gravity system at Windsor Terrace. Ultimately it is anticipated that the existing Clonmullen Pumping Station shall be abandoned with all flows directed to the new station.

6. Carrick Road 2 No. 225 mm foul/combined sewers drain to Carrick Road Pumping Station to the north of the town. This pumps directly to the wastewater treatment works. These sewers collect from all of the development to the north as well as the

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Industrial Estate on Carrick Road. There are no surface water sewers in the area so there would be a reasonable surface water contribution to the foul sewers.

7. Rhode Road A 225 mm foul/combined sewer along Rhode Rd which collects foul and some surface water flows from the Castleview Estate and properties along Rhode Road and Gilroy Avenue. This area is also served by an old surface water sewer which has been re-routed to the foul/combined network due to its combined nature. This sewer collects mainly surface water flows from Corkery Lane Pumping Station to the west and from the new Industrial Estate (part) on Rhode Road. The two sewers run in parallel along Rhode Road / St. Francis Street before turning north and connecting to the main inlet sewer to the rear of properties along Francis Street. It is proposed to return the old surface water sewer to surface water only under the Edenderry Surface Water Scheme. This contract which is due to commence on site shall divert flows to Weaver’s Drain.

8. Main Collector The main collector sewer runs from Fr. Kearns Road to the east of the town centre, along Colonel Perry Street, along the backs of the properties to the north of JKL Street, and St. Mary’s Street before outfalling into the wastewater

treatment works located Forto inspectionthe north purposes of only. Rhode Road. The sewer increases from Consent of copyright owner required for any other use. 225 mm to 800 mm at the inlet to the Works.

3.2.3 Existing Pumping Stations

There are ten foul pumping stations located in the periphery of Edenderry, all of which pump into the town centre foul/combined sewer system as located on Drawing No. 20290/02. A detailed survey of the pumping stations was carried out by Such Salinger Peters in June 2003. Their Report is included in the Appendices. Each pumping station is summarised below:

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1. Blundell Wood Pumping Station is located to the southwest of the Blundell Wood Estate near the Grand Canal. The station collects flows from the southern half of the estate and pumps via an 80 mm cast iron rising main to a sewer in the northern half. There are 3 No. incoming 225 mm sewers. There are 2 submersible pumps on a duty/standby basis although one pump was removed at the time of the survey. The maximum pumping rate was measured as 7.1 litres/sec.

The overall state of repair of this pump station is poor with 1 No. pump missing, a damaged control kiosk and apparent inlet pipe infiltration from a nearby spring.

2. Carrick Road Pumping Station is located on Carrick Road to the north of the town. There are 2 x 225 mm sewers entering, from the south and north. A 100 mm cast iron rising main pumps directly to the wastewater treatment works on Rhode Road. There are 2 submersible pumps on a duty/standby basis. The maximum pumping rate was measured as 17.7 litres/sec. A high level 225 mm overflow pipe discharges to an adjacent stream.

A monitor was installed Forupstream inspection purposes of th only.e pumping station on the northern sewer Consent of copyright owner required for any other use. as part of the flow survey and model calibration. The measured data showed that the pumping station was not able to cater for excessive stormwater in the sewer and caused backing up in the sewers upstream.

The covers to the wet well were in poor condition and the site was generally overgrown.

3. Clonmullen (2 Pumping Stations) Pumping Station is located to the northeast of the town. The station collects flows from 2 x 225 mm sewers and pumps via a 100 mm cast iron rising main to a manhole on Colonel Perry Street. There are 2 submersible pumps on a duty/standby basis. The maximum pumping rate was measured as 9.7 litres/sec.

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A new pumping station has recently been constructed at the site of a new residential development. This pumping station currently accepts effluent from the recently completed properties in this development and pumps effluent to the existing gravity system at Windsor Terrace. Ultimately it is anticipated that the existing Clonmullen Pumping Station shall be abandoned with all flows directed to the new station.

4. Connyborough Pumping Station is located on the Dublin Rd to the east of the town. There are 2 No. 225 mm sewers entering which serve the properties along Dublin Road and the Connyborough Estate. Flows are delivered via a 100 mm cast iron rising main to the town centre sewers. There are 2 submersible pumps on a duty/standby basis. The maximum pumping rate was measured as 9.8 litres/sec.

Monitors were installed upstream of the pumping station on both incoming sewers as part of the flow survey and model calibration. The measured data showed that the pumping station was not able to cater for excessive stormwater in the sewer and caused backing up in the sewers upstream. The valve chamber was flooded with water at the time of the survey.

5. Corkery Lane For inspection purposes only. Consent of copyright owner required for any other use. Pumping Station is located off Rhode Road to the west of the town. There are 3 No. 225 mm sewers entering which serve properties to the extreme west of the town. Flows are delivered via a 50 mm cast iron rising main to a 150 mm sewer in the new industrial estate on Rhode Road. There are 2 submersible pumps on a duty/assist basis. The maximum pumping rate was measured as 8.8 litres/sec.

6. Derrycorris Pumping Station is located at the end of Fr. Murphy Street to the southeast. It serves the properties to the extreme south of the town and pumps to a manhole on Fr. Murphy Street to the north, via a 100 mm rising main. There are 2 submersible pumps on a duty/assist basis. The maximum pumping rate was too low to measure.

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7. Killane Pumping Station is located to the south west on St. Mary’s Street adjacent to George’s Bridge over the Grand Canal. There is one 225 mm sewer entering which serves the large Killane housing estate on St. Mary’s Road and extends as far north as Rhode Road. Flows are pumped via a 100 mm rising main to the gravity sewer on St. Mary’s Road adjacent to the Health Centre. There are 2 submersible pumps on a duty/assist basis. The maximum pumping rate was measured as 12.5 litres/sec.

A monitor was installed upstream of the pumping station on the incoming sewer as part of the flow survey and model calibration. The measured data showed that the pumping station was not able to cater for excessive stormwater in the sewer and caused backing up in the sewers upstream. This was confirmed during the pumping station survey where evidence of surcharge past the cover level was noted.

8. Murphy Street Pumping Station is located on Fr. Murphy Street opposite Greenwood Park Estate. The pumping station serves only a few properties and pumps via a 100mm rising main to the foul sewer on Fr. Murphy Street. There are 2

submersible pumps on aFor dut inspectiony/assist purposes basis. only. The maximum pumping rate was Consent of copyright owner required for any other use. measured as 7.3 litres/sec. This pumping station was not modelled due to the small catchment that it serves. The valve chamber was flooded at the time of the survey.

9. The Sycamores Pumping Station is located in a new housing estate which is currently under construction between St. Mary’s Road and the Grand Canal. The pumping station currently serves the housing estate and delivers effluent to the existing gravity sewer on St. Mary’s Road. There are 2 submersible pumps on a duty/standby basis. The maximum pumping rate was measured as 19.76 litres/sec.

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3.2.4 Existing Overflows

There are 8 overflows and bifurcations within the town’s foul/combined sewer network. A detailed survey of all overflows was carried out by USA Ltd as part of the overall manhole survey. A separate report detailing the results of this survey has been provided. An assessment of the overflow performance during the flows survey is included under the section on Model Calibration. The overflows are described hereunder and shown on Drawing No. 20290/02.

1. Overflow No. 1 This is located on Rhode Road to the west of the town centre. A high level 225 mm overflow pipe connects the foul sewer to the old surface water sewer on Rhode Road. As aforementioned the surface water sewer now outfalls into the combined system upstream of the wastewater treatment works. However, it is proposed under a separate scheme that this sewer be returned as a surface water sewer and to divert the outfall into the Weaver’s Drain. As this watercourse has negligible assimilative capacity and in accordance with proper environmental practice, it is recommended that this overflow be removed. It is further recommended that this work be carried out as part of the Edenderry Surface Water Scheme which is due to commence shortly.

For inspection purposes only. Consent of copyright owner required for any other use. 2. Overflow No. 2 This is located adjacent to No. 9 Gilroy Avenue. A high level 150mm overflow pipe connects the foul sewer on Gilroy Avenue to the old surface water sewer on Rhode Road. As aforementioned the surface water sewer now outfalls into the combined system upstream of the wastewater treatment works. However, it is proposed under a separate scheme that this sewer be returned as a surface water sewer and to divert the outfall into the Weaver’s Drain. As this watercourse has negligible assimilative capacity and in accordance with good environmental practice, it is recommended that this overflow be removed.

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3. Overflow Nos. 3 & 4 These 2 overflows are located adjacent to No. 21 St. Francis Street / Rhode Road. Excess flow discharges over a weir from the foul sewer in Manhole SN62325604 and into a 225 mm overflow pipe which flows into Manhole SN62325609. There appears to be another overflow at this manhole. Further investigation of these overflows will be undertaken. In any case, the outfall from this overflow discharges into Weaver’s drain, which has negligible assimilative capacity. In accordance it is therefore recommended that this overflow be removed. It is further recommended that this work be carried out as part of the Edenderry Surface Water Scheme which is due to commence shortly.

4. Overflow No. 5 This is located on Rhode Road / St. Francis Street at its junction with Gilroy Avenue. Excess flow discharges via a high level 185 mm overflow pipe. It is assumed that this is connected to the old surface water sewer on Rhode Road. For reasons given earlier, it is recommended that this overflow be removed. It is further recommended that this work be carried out as part of the Edenderry Surface Water Scheme which is due to commence shortly.

5. Overflow No. 6

This is located on the Forma inspectionin outfall purposes seweronly. behind JKL Street. Excess flow Consent of copyright owner required for any other use. discharges over a 2-sided weir into a 300 mm overflow pipe. This in turn outfalls to an adjacent watercourse. As this overflow is located close to the main inlet works at the wastewater treatment works, it is recommended that it be removed and storm flows handled at the works.

6. Overflow No. 7 This is located opposite No. 70 JKL Street. A 225 mm overflow pipe discharges excess flows from the foul sewer on JKL Street to the main combined sewer which runs behind and to the north of JKL Street. This relief sewer was put in to alleviate surcharging in the JKL Street Sewer.

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7. Overflow No. 8 This is located opposite No. 18 Fr. Murphy Street. A high level 225 mm overflow pipe discharges excess flows from the foul sewer into the Greenwood Park surface water network, which in turn outfalls into a small stream behind No. 18 Fr. Murphy Street. As this watercourse has negligible assimilative capacity and in accordance with proper environmental practice, it is recommended that the Greenwood Park overflow be removed.

3.3 Hydraulic Modelling of Existing System

3.3.1 General Methodology

3.3.1.1 Hydraulic Model Construction

1. Modelling Software Used The InfoWorks CS Suite of modelling software produced by Wallingford Software Ltd has been used for this Study. Infoworks CS is the latest generation of hydraulic modelling packages for sewerage systems produced by Wallingford, following Wallrus, Spida and Hydroworks.

InfoWorks CS including a GIS (Geographical Information System) capability that can For inspection purposes only. Consent of copyright owner required for any other use. be used to superimpose the models onto digital mapping. The software is also compatible with the GIS software Mapinfo, and with data handling software such as MS Access and Excel.

2. Sewer Data The system manholes are surveyed on site by a specialised Contractor and the Manhole Database subsequently delivered in SUS25 format. The database is then converted into Infoworks format. Any gaps or anomalies in the data is reported and re-surveyed if necessary. Where manholes were impossible to locate or open, their data can be interpolated from neighbouring manholes using the Infoworks software.

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Prior to performing any hydraulic analysis, the model information is validated to highlight any potential errors in the data (e.g. missing information, decreasing diameters, negative gradients etc).

3. Other Survey Data As well as providing information on the manholes, it is also necessary to carry out an internal condition CCTV survey of the sewers in the network in order to assess their existing structural condition. A rehabilitation programme can then be undertaken to rectify the most serious defects noted.

The CCTV survey data can also be input into the model as sediment depths, hydraulic roughness, infiltration and also as a check of the physical sewer data (pipe size, material, etc). It is possible to import the relevant information directly from the Examiner software or any spreadsheet format into the Infoworks model.

Data from the pumping station survey and pump tests is also input into the model at this stage.

Although the data from the Flow Survey is primarily used in the Model Calibration stage (see below), the information provided can also give a good indication of the

degree of surface water infiltration For inspection (direct purposes only.or otherwise) into the combined sewer Consent of copyright owner required for any other use. upstream of the monitor.

4. Sub-Catchments A drainage sub-catchment contains information on the following: ƒ Foul loading – calculated from the number of houses, and other properties in the sub-catchment; ƒ Surface water loading – determined by the extent of impermeable and permeable areas in the sub-catchment. The impermeable area / permeable area contribution can be ascertained from on site observations and from the CCTV connection information. ƒ Node Reference – The manhole on the hydraulic model to which the above loadings will drain.

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5. Final Validated Model Following construction and validation of the hydraulic model and inputting of the drainage sub-catchments, the model is ready for calibration and further analysis.

3.3.1.2 Model Calibration

Calibration of the hydraulic models is essential to establish confidence in the physical data and in the loading data input into the model and hence, in the results predicted by the model. In order to confirm that the model correctly represents the real system these hydraulic models will be calibrated, with the use of flow and rainfall data.

Model Calibration against flow survey data is achieved by comparing the flows predicted by the model, when subjected to a known event, with the actual flows measured in the sewer network for the same event. Normally 5 Events are selected from the Flow Survey for analysis, 3 Rainfall Events and 2 Dry Weather Day Events.

Corrections are made to the Model during the calibration process only where the flow monitor is known to be recording accurately, and where the physical condition of the sewers and the contributing impermeable areas are independently checked. When agreement is achieved between the Model and the flow survey (or where a

satisfactory explanation can be For inspectiongiven purposesfor di only.sparity in the results) for 2 out of the 3 Consent of copyright owner required for any other use. significant rainfall events selected from the Flow Survey, the Model is considered to be calibrated.

It should be noted that due to restrictions in the flow monitoring equipment, it is usually impossible to adequately verify against dry weather flows for upstream monitors where the flows are very low.

The Code of Practice For The Hydraulic Modeling of Sewer Systems (ref.3.1) states that the modelled flows/depths compared with the observed flows/depths should meet the following criteria:

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ƒ Peak flow rate + 25% to - 15%

ƒ Volume of flow + 20% to - 10% over the period for which the observed flows are expected to be accurate

ƒ Surcharge should be +0.5 m to - 0.1 m

ƒ The general shape of the two hydrographs should be similar and should continue until substantial recession has occurred

If the above criteria are met for two out of the three rainfall storms, the Model may be considered to be calibrated.

3.3.1.3 Hydraulic Analysis of the Existing System

Following calibration of the sewer system hydraulic model, the existing system is analysed using a rainfall event of 1 year return period in order to highlight the existing weaknesses in the system.

At this stage the effect of the contribution to the system from stormwater and

infiltration is also assessed. ForThis inspection will purposes demonstrate only. the loss of capacity in the foul Consent of copyright owner required for any other use. system, due stormwater ingress and readily demonstrate the effects of network rationalisation.

3.3.2 Construction of Edenderry Hydraulic Model

3.3.2.1 A survey of all of the manholes in Edenderry was carried out by USA Ltd. between July and October 2003. A SUS 25 database containing all of the survey information was submitted by USA in early October 2003. In all, the database contained 511 manhole records as follows:

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Use Number of Manholes Pipelength (km) Combined 150 7.4 Foul 229 9.4 Storm 132 5.8 Total 511 22.6

3.3.2.2 Following receipt of the manhole database in SUS 25 format, the Model Build process was carried out as follows;

1. Original Import from SUS 25 to Infoworks. The database was initially converted to the Mapdrain format which is MSAccess based. This enabled the Node and Pipe records to be stored in tabular format for copying into Infoworks.

2. The original database contained a number of gaps and anomalies. There were over 60 manholes in the original survey which were not surveyed for various reasons, including inaccessible and buried manholes and surcharged manholes. Where information on these manholes was not available from sewer records, their levels and diameters were inferred from surrounding manhole levels and pipe diameters.

For inspection purposes only. Consent of copyright owner required for any other use. 3. Surveys and pump capacity testing were carried out on each of the town’s pumping stations and overflows as previously outlined. This information was added to the model.

4. Simplification of the network model was carried out to exclude small and unimportant pipe lengths. These are represented by increased storage in the downstream nodes.

5. After correction of any remaining errors in the model, the model is assumed to be validated.

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6. Sub-catchment information (i.e. impermeable areas and populations) were then input into the validated model. The populations were calculated based on the import of the Geo-Directory database, which contains a unique point for each property in the catchment. The initial impermeable areas estimated were measured taken off the background mapping based on an original runoff assessment.

7. The validated model is then ready for calibration against observed data.

3.3.3 Hydraulic Model Calibration

3.3.3.1 A Flow Survey was carried out by Capital Water Systems Ltd. between 13th May and 24th June 2003, and consisted of 11 Flow Monitors and 3 Raingauges, as shown on Drawing No. 20290/05.

As per the requirements above, three rainfall and two dry weather events were selected from the flow survey for use in the model calibration as follows:

Table 2.1 – Rainfall Event Details

Events Day Start Finish Duration (mins) For inspection purposes only. 1 03-JunConsent of copyright owner09:00 required for any other use. 19:00 600

2 07-Jun 03:00 11:00 480 3 10-Jun 05:00 10:00 300 4 - Dry 13-Jun 00:00 00:00 1440 5 - Dry 16-Jun 00:00 00:00 1440

3.3.3.2 Calibration Summary

In summary, the majority of the monitors showed reasonable correlation between Observed and Predicted data for 2 out of the 3 selected rainfall Events. A number of operational issues were noted throughout the course of the survey, as follows:

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1. The flow survey was carried out in advance of the sewer cleaning and CCTV contract. This was done in order to obtain accurate data on how the network was actually performing at that stage. However a large build-up of silt was found at a number of sewer locations which affected the flow regime in the town. Also ragging and silting of the monitors caused their failure on a number of occasions.

2. The flows during the 2 dry weather events was in most cases too low to record.

3. Four of the monitors were installed in the downstream pipes at manholes. Turbulence picked up as the flow passes through the manhole affected the velocity and depth readings and this reduced the confidence in the monitored data.

4. Most of the pumping stations in the town were found to be under capacity during heavy rainfall. Surcharging in the sewers upstream affected the velocity measurements in some of the upstream monitors.

However, as aforementioned, it was possible to calibrate the main monitors in the town and therefore the hydraulic model can be used with a reasonable degree of

confidence. For inspection purposes only. Consent of copyright owner required for any other use.

Calibration plots for all of the flow monitors in the flow survey are included in Volume II ( Appendices) of this Preliminary Report. A brief description of each monitor is also included.

3.3.4 Hydraulic Analysis of Existing System

3.3.4.1 The main hydraulic issues in Edenderry as established by the model calibration were:

1. There are capacity problems at most of the pumping stations.

2. The amount of storm flows entering the foul network. All of the 11 monitors displayed some response to rainfall.

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3. Many of the existing town sewers have capacity problems.

After establishing confidence in the hydraulic model of the existing system, its performance under design rainfall conditions is analysed to identify its hydraulic weaknesses under existing loading conditions. The model is initially tested using rainfall of 1 year return period

3.3.4.2 Drawing No. 20290/07 below illustrates the performance of the existing network for a 1 year 30 minute rainfall event. Sewers which are surcharged through hydraulic incapacity are shown in blue. Those surcharged because of downstream conditions are shown in green. Flooding at a node is shown as blue circles around the node – the extent of flooding denoted by the number of circles.

3.3.4.3 The main weaknesses in the existing network as indicated from the 1 year analysis are:

1. Pumping Stations Surcharging in the sewers upstream of a number of pumping stations caused by these facilities being under capacity during storm conditions.

For inspection purposes only. Consent of copyright owner required for any other use. 2. Sewers ƒ Capacity of the sewer from Fr. Paul Murphy Street around the backs of the houses to Fr. Kearns Street and back westwards towards the WWTW via Colonel Perry Street. This sewer currently takes combined flow from the Greenwood Park Estate as well as some further areas along Dublin Road (including the flows from Connyborough pumping station) and the town centre. Most of this sewer is currently under capacity causing surcharging during the 1 year event.

ƒ Capacity of the existing St. Mary’s Street sewer. This sewer serves a large area to the south-west of the town including the Killane Estate, the new Sycamores development and the schools along St Mary’s Street. The sewer is currently under capacity causing surcharging and flooding during the 1

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year event. A separate surface water scheme, proposed for the town, includes for the laying of a new surface water sewer along this street - this should alleviate most of the problems under existing loadings by removing much of the surface water runoff from the foul/combined sewer.

ƒ Capacity of JKL Street Sewer. This sewer serves many of the commercial properties in the town as well as Blundell Wood Estate. Although there is a relief sewer from JKL Street to the main collector, there is still nonetheless surcharging in this sewer under design rainfall.

3. Overflow Discharges The existing Edenderry network contains a number of overflows, which have been constructed over time to relieve the foul network as more areas were added to the town. The location of these overflows is shown on Drawing No. 20290/02. These overflows discharge to the surface water network and in some cases directly to ditches. From an environmental perspective, there are currently no available watercourses with adequate assimilative capacities in the vicinity of the town. It is therefore recommended that the overflows should be eliminated entirely.

This will obvious ly have For an inspection impact purposes on only. the sewers downstream of the overflows Consent of copyright owner required for any other use. and it follows that these will need to be upsized to cater for the increased flows. The impact of removing these overflows is further discussed in Section 7 of this report.

3.4 CCTV and SUS 2000 Survey

A CCTV and SUS 2000 survey of the existing pipelines and manholes along the wastewater collection system was carried out by USA Ltd. between June to October 2003. The results of this survey and all digital records, drawings and data are available as separate reports. This report details for each survey run, in terms of drawings, interpretation and CD-rom format:

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ƒ Shape ƒ Material ƒ Use (Foul / Combined / Storm) ƒ Lengths between upstream and downstream manholes ƒ Sewer Defect (if any).

Remarks were recorded along the length of the survey according to silt / water level, obstructions, general condition and structural condition of sewer. Surface water infiltration into the sewer through cracks or displaced joints was also noted.

The purpose of this survey was twofold. Firstly very limited ‘As – Constructed’ information was available of the existing system which would allow it to be hydraulically modelled and analysed as set out above. Secondly the survey was necessary to examine the existing structural integrity of the system. Up to 22 km of pipeline and over 500 manholes were surveyed. The pipeline surveys were analysed using Examiner Software in order to allocate a Structural Grading to each section of pipeline. The grading and structural performance of the system was assessed using the Water Research Council “Sewer Rehabilitation Manual – Third Edition”.

This software grades pipelines between 1 and 5. A Grade 1 result indicates a pipeline

in a good state of repair with For noinspection visible purposes defect only. s of any nature. A Grade 5 result Consent of copyright owner required for any other use. indicates a pipeline in a critical or poor state of repair with major defects observed and in need of immediate attention. Generally in developing a repair and rehabilitation schedule for pipeline sections, it is recommended that structural grades 3 – 5 inclusive are considered. This range covers all minor and major defects observed. The CCTV and SUS 2000 reports also recommends the type of repair necessary in terms of repair, relining or replacement. This is further discussed in Section 7. Tables 3.4 and 3.5 below indicate the relevant pipeline diameters and lengths and manholes which currently need to be rehabilitated. This information is also shown on Drawing No. 20290/06.

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Table 3.4 – Pipeline Rehabilitation Schedule Pipe Diameter Length to be Repaired Structural Grade (m) 150 27.5 3 1219.4 4 527.4 5 225 172.3 2 441.2 3 4907.5 4 802.2 5 300 142.2 4 27.8 5 375 155.8 3 209.1 4 450 42 4 525 351.5 4

Table 3.5 – Manhole Rehabilitation Schedule

Works No. of Manholes Replace Cover 34 For inspection purposes only. Reline ManholeConsent of copyright owner required for any other use. 235

Repair Benching 85

Thus in terms of pipeline lengths over 44% of the entire network needs rehabilitation. The majority of the rehabilitation works require (91%) relate to critical defects (ie. in the Grade 4-5 range). Furthermore it should be noted that significant sections of pipelines had silt and grease levels of greater than 20%. These sewers had to be cleaned before the CCTV works could proceed. Obviously this level of silting effects the hydraulic performance of the network and the situation is likely to re-occur if the sewers are not regularly maintained. In terms of manholes 69% of manholes surveyed shall require rehabilitation.

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3.5 Existing Wastewater Treatment Plant

3.5.1 Introduction

The existing Edenderry Wastewater Treatment Works was refurbished and upgraded during the period 2002-2003 resulting in increasing the design capacity from 5,000 to 7,000 p.e. The layout of the existing Wastewater Treatment Works and Outfall Pipeline is shown on Drawing Nos. 20290/03 and 20290/04. The works generally involved the upgrading of the existing treatment units (with the exception of the existing clarifier) to achieve greater throughput and treatment capacity.

A new Inlet Pumping arrangement was provided to deliver screened effluent to an upgraded aeration tank. The works to the aeration tank involved a TWL increase, the construction of an anoxic zone and the provision of fine bubble diffusers. A new clarifier was constructed to replace the existing which had limited potential for upgrading. A 600 mm diameter outfall pipeline to the River Boyne was also constructed. Sludge Thickening and Dewatering Facilities and a new Administration Building were also constructed.

The existing works can treat loads up to 3 DWF. The storm tanks are capable of

holding flows in excess of 3 DWF For inspection and purposesup to only.a maximum of 5.5 DWF for a period of 2 Consent of copyright owner required for any other use. hours and anything in excess of this is discharged into the River Boyne following screening.

Due to recent developments in the town and increased industrial activity, the works are currently at or above the upgraded design capacity (7,000 p.e.) as set out further in this section.

3.5.2 Existing Wastewater Treatment Works Overview

3.5.2.1 General The Edenderry Wastewater Treatment process is a conventional extended aeration process and incorporates the following components.

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1. Mechanically Raked screen and de-gritting facility. (Pista grit trap). 2. Screening washer/compactor unit. 3. One Aeration basin designed to accept 420 kg BOD/day. 4. One Clarifier with a discharge to the River Boyne. 5. Sludge thickening and dewatering facilities. 6. Phosphate dosing facility. 7. Administration Building. 8. Storm holding Tank. 9. Foul, Storm, RAS and SAS pumps.

The existing plant has a design capacity of 7,000 p.e. and a design effluent quality of 20 mg/l BOD, 30 mg/l suspended solids, Total Phosphorus of 1 mg/l and a 50% reduction in Total Nitrogen.

3.5.2.2 Inlet Works The existing inlet works is a 12 m long structure and consists of the following:

ƒ Hand Raked Screen and J&A Mechanically Raked Screen ƒ Pista Grit Trap ƒ Grit Collection Chamber

ƒ Washer and Compaction Unit For inspection purposes only. Consent of copyright owner required for any other use. ƒ Open top skips

A flowmeter for inlet flow recording to the treatment units is also provided.

Aeration Basins

The main treatment process is by means of extended aeration. A 200 m3 anoxic zone with mixers is provided for denitrification at the main inlet to the aeration tanks. The aeration tank itself has a volume of 1,596 m3. Aeration is by means of fine bubble diffused aeration. Chemical dosing takes place at this location for the precipitation of phosphorous.

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This process is running without any major problems since being commissioned in 2003. The MLSS content of the sludge is maintained in the range 3,000 - 3,500 mg/l.

3.5.2.4 Clarifier Final settlement is achieved in a 17 m diameter hopper bottomed clarifier. Settled sludge is withdrawn from the clarifier and feeds by gravity to a sludge draw off chamber and on to the sludge pumping station from where sludge is either returned to the aeration tank or wasted to the sludge thickening tank. The clarifier is running efficiently and is producing a good quality effluent.

3.5.2.5 Picket Fence Thickener Settled waste sludge drawn from the clarifier is stored in a sludge holding tank. This sludge holding tank sized for 14,000 p.e. also doubles as a picket fence thickener, thickening the sludge to 3% d.s. before being pumped on to the sludge dewatering building.

3.5.2.6 Dewatering The sludge is then dewatered using a Centrifuge to 18% d.s. and the cake is pumped to covered skip for removal off site. The dewatering facilities has the capacity to cater for up to 14,000 p.e. of sludge.

For inspection purposes only. Consent of copyright owner required for any other use. 3.5.2.7 Phosphate Dosing Facility Chemical Dosing (Ferric Sulphate) is carried out on the existing works. This introduction of chemical dosing was carried out in order to remove orthophosphate in the effluent.

3.5.2.8 Administration Building The controls for the plant are automated and are designed on the basis of a full time operator not being required. The site is automated except for the sludge dewatering plant which requires some operator supervision.

3.5.2.9 Effluent Outfall The existing outfall (600mm dia) discharges the treated effluent into the Boyne River approximately 1,200 metres north of the existing works.

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3.5.2.10 Storm Tank There is storm water screening and detention tanks at the work. Flows in excess of 60.9 l/s (3 DWF for the design of the process units) are discharged to the stormwater tanks. The tanks have a capacity of some 380 m3 which is equivalent to a detention time of 2hours for flows of up to 2.5 DWF in excess of the 3 DWF that receives full treatment. Flows in excess of 5.5 DWF will be screened by means of storm overflow screens capable of handling 250 l/s in the Storm Holding tank before discharging into the River Boyne

The tank is also equipped with a washdown unit which operates both to keep solids from settling when there is a storm flow and also to wash down the tank when the storm condition has ended.

3.5.2.11 Foul & Storm Pumps 2 No. Foul pumps currently deliver flows up to 3 x DWF to the main process units. 2 No storm pumps return water to the main process flow when the incoming flow drops to 1.5 DWF.

3.5.2.12 Sludge Reception Facilities Edenderry Wastewater Treatment Works is designated as a satellite centre in the Sludge Management Plan for County Offaly, 2001. As such it must accept liquid For inspection purposes only. Consent of copyright owner required for any other use. sludge for Thickening and Dewatering from a number of surrounding centres before transportation in the form of sludge cake to Tullamore for further treatment. Works are due to commence on site to provide Sludge Reception Facilities to cater for 3,500 p.e. of imported sludge. The existing picket fence thickener and sludge dewatering unit have adequate capacity to deal with these increased loadings.

3.5.3 Operation and Maintenance

3.5.3.1 Responsibilities and Practices The operation and maintenance aspects are two important components for an efficient wastewater disposal system. The number of persons employed for operation and maintenance of the Wastewater collection and disposal facilities are summarised as follows:

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Table 3.6 – Persons Employed at Edenderry WWTW Edenderry Wastewater Treatment Works Persons employed (Caretaker) 1 (75% of time) Persons employed (Technician) 1 (50 % of time) Population served 5,500-7,000

The operation and maintenance of the sewerage system and sewage treatment facilities are undertaken by the Sanitary Services Section of the County Council. The overall performance of the plant is good and to acceptable standards.

3.5.4 Flow and Load Survey

The original plant design parameters are summarised as follows:

Population Equivalent BOD Load Hydraulic Load P.E. g/h/day kg/day l/h/day m3/day 7000 60 420 250 1750

There is storm water screening and detention tanks at the work. Flows in excess of 60.9 l/s (3 DWF for the design of the process units) are discharged to the stormwater For inspection purposes only. tanks where there is a deteConsentntion of copyright time owner of 2required hours for anyfor other flows use. of up to 2.5 DWF in excess

of the 3 DWF that receives full treatment. Flows in excess of 5.5 DWF will be screened by means of storm overflow screens capable of handling 250 l/s in the Storm Holding tank before discharging into the River Boyne.

A three day flow and load survey was carried out between 26th and 29th November 2003.

The results of this survey are presented in Figures 3.1 to 3.4. These results indicate a population equivalent at approx 7,700 in terms of BOD contributing to the works. It also indicates population equivalents of 7,450, 7,600 and 6,800 in terms of suspended solids, ortho-phosphorous and Total Kjeldahl nitrogen respectively. These figures indicate an average population equivalent in terms of influent load of 7,700. The

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Loads peak on the first two days between 4pm and 8pm indicating a normal diurnal nature of a typical flow to a Wastewater Treatment Plant. Peak of load during the day and minimum loads at night. The third day of the flow and load survey is from midday on the 28th November 2003 to midday on the 29th November 2003 (Fri-Sat) and the loads are noticeably lower over this period, possibly due to reduced activity in terms of schools and businesses.

As outlined above the population equivalent discharging to the works from the catchment is deemed to be 7,700. It should be noted that while these figures indicate that the existing Wastewater treatment may be overloaded by as much as 10% the plant has, by a combination of good design and careful operation continued to comply with its discharge standards. Examination of the results since January 2003 of tests on the composite flow samples from the effluent line have shown that all have been comfortably within the limits outlined in the regulations for flow to the river from the works. The grab samples from the effluent line (a much more onerous standard) have also been compliant in every case since the end of January 2003.

Furthermore the EPA ‘ Interim Report on The Biological Survey of River Quality, Results of the 2003 Investigation ‘ indicates that Q value of the river at two locations downstream of the works has recently improved from a Q1-2 to a Q3 and from Q3 to

Q4. This represents a consid erable For inspection improvement purposes only. on historical water quality data ( as Consent of copyright owner required for any other use. further discussed in Section 5 of this report ) and the EPA report further states ‘..significant improvements were recorded below Edenderry (0300,0400) and again below Trim (1400) and this is attributed to the upgrading of the sewage treatment plants at these towns.’

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BOD 00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 BOD Time (Hours)

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Kg 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 0: 0 90 80 70 60 50 40 30 20 10 100 Figure 3.1

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Suspended Solids 00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 Time (Hours) Suspended Solids

For inspection purposes only. Consent of copyright owner required for any other use.

Kg 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 0: 0 80 60 40 20 160 140 120 100 Figure 3.2

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Ortho-Phosphate 0:00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 Time (Hours) Time Ortho-Phosphate

For inspection purposes only. Consent of copyright owner required for any other use.

Kg 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 2 1 0

2.5 1.5 0.5 Figure 3.3

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Total Kjeldahl Nitrogen :00 4:00 8:00 12:00 16:00 20:00 0:00 4:00 8:00 12:00 Time (Hours) Time Total Kjeldahl Nitrogen

For inspection purposes only. Consent of copyright owner required for any other use.

Kg 12:00 16:00 20:00 0:00 4:00 8:00 12:00 16:00 20:00 0 8 6 4 2 0 16 14 12 10 Figure 3.4

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4. POPULATION PROJECTIONS, WASTEWATER FLOWS AND STAGING OF THE SCHEME

4.1 General

In this section, each component of the wastewater flow is assessed in turn by reference to the most relevant data available on forward projections.

4.2 Population Projections

In estimating domestic population projections for Edenderry it will be necessary to consider the following:

ƒ General trends from the 2002 Census Report ƒ Statutory Development Plans for Offaly County Council with particular reference to Land Use Zoning Maps ƒ Offaly County Council Housing Strategy ƒ Edenderry Land Use and Transportation Study Report 2003, Atkins

The recorded population for the Edenderry Urban Catchment from the 2002 Census Report is 4,222. However as outlined in Section 3 the existing wastewater collection For inspection purposes only. system extends to some Consentdegree of copyright outside owner the required Urban for any otherBoundary. use. This is particularly the

case at Corkery Lane (Monasteroris) and in the vicinity of the Killane Road Pumping Station. The 2002 Census Report figure for Monasteroris is 732. When this figure is added to the Urban Area figure (4,222) it gives a total recorded population for the existing Edenderry catchment of 4,954.

However, a count of all houses in the existing catchment was carried out using Geo- Directory data. Geo-Directory is a database of accurate postal and geographic addresses of properties in Ireland, formulated from a joint venture between An Post and Ordnance Survey Ireland. In mid-2003 the directory indicated that there were approximately 1,600 residential properties in the Edenderry catchment. Since this time it is estimated that an additional 50 No. houses have been constructed which are

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not yet on the database. Using a household occupancy of 3.1 (2002 rate for County Offaly) this amounts to a current population of 5,125.

The domestic population growth rate and population projections for this scheme will be examined for a 25 year horizon as follows:

1. Population growth based on the 3% annual growth rate observed in the Census over the period 1996 to 2002. (Low)

2. Population growth based on the land zonings in the development plan and the assumption that they are all developed. (High)

A further category (Medium) shall be examined which shall be based on the potential for an existing industry within the town expanding.

Furthermore preliminary discussions have taken place between representatives of Kildare and Offaly County Councils regarding the possibility of pumped wastewater loadings from village catchments along the Offaly / Kildare County border located being accepted at an upgraded Edenderry Works. The villages concerned are Derrinturn, Ticknevin and Carbury all in County Kildare. The feasibility of this

option versus a centra l treatment For inspection plant purposes or only. individual plants are currently under Consent of copyright owner required for any other use. separate examination. In the meantime the potential for inclusion of these loadings at an expanded Edenderry works are included in the medium and high categories.

The anticipated loadings from each category are derived as outlined in Sections 4.3, 4.4 and 4.5 below.

4.3 Low Growth Trend

Domestic The Census of Population Figures for the Edenderry Catchment from the years 1981 to 2002 are presented in Table 4.1.

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Table 4.1 – Population Growth Trends Year 1981 1986 1991 1996 2002 Urban 3,452 3,539 3,525 3,591 4,222 % increase per year -- 2.5% -0.4% 1.9% 17.6% Rural 596 630 611 582 789 % increase per year 5.7% -3% -4.7% 35% Combined 4,048 4,169 4,136 4,173 5,011 % increase per year -- 3% -0.8% 0.9% 20%

The population growth trends for the Edenderry Urban, Rural and Combined Catchments are presented. The analysis of population trends indicates that there was a 4% increase in the population of the Edenderry Urban area between the years 1981 to 1996. Population figures from the 2002 Census indicates that during the period 1996 to 2002 the population increased by 17.8%. Taking the combined catchment figures (urban and rural) the 2002 Census indicates that during the period 1996 to 2002 the population increased by 20% approximately. This represents an annual increase of 3.3%.

The increased population was realised during this period due to unprecedented development of the town and its increasing status as a commuter town for the Greater

Dublin Region. However while For inspection Planning purposes only.Permission for almost 1,600 residential Consent of copyright owner required for any other use. units have been granted in the town since 1996 there has been only 222 house completions1. This would suggest that the increase in population observed in the 1996 to 2002 was on the conservative side in terms of the overall development potential. Clearly market forces will determine how the development of the town will proceed over the coming years.

Certainly the town will remain an attractive location for first time buyers outside the Greater Dublin Region and within a viable commuting distance. The feasibility of the town as a commuting centre for Dublin will be further enhanced following the completion of the extension of the M4 motorway from Kilcock to Kinnegad, currently under construction. Likewise the proposed Edenderry-Enfield link road shall further enhance transport links and reduce commuting times.

1 Source : LUTS Report 2003 – Atkins

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Thus in view of the anticipated level of development within the town over the coming years it has been with representatives of Offaly County Council that an annual increase of population of 3% should be adopted to the year 2028.

This would result in the domestic population of the catchment increasing from 5,125 to 9,945 by the year 2028.

Industrial

Edenderry is not a highly industrialised town. The principal industry in the town is Glanbia Meat Processors located along the Kinnegad Road. Two smaller industries exist in the town namely S.C.A. Packaging on Francis Street and Drummonds Fertilisers at Fairgreen.

Glanbia is the most significant industrial load contribution in the town. The industry produces quite a high strength effluent. Their Integrated Pollution Control (IPC) Licence issued by the Environmental Protection Agency (EPA) in 1997 stipulates quite stringent discharge parameters for the effluent before it can be discharged to the municipal sewer in Edenderry. These standards are outlined in Table 4.2 below. An

on-site wastewater treatment Forplant inspection at purposesGlanbia only. is provided in order to achieve these Consent of copyright owner required for any other use. parameters.

Table 4.2 – IPC Discharge Standards - Glanbia Parameter Emission Limit Value Temperature 25˚C (max) pH 6.5 – 8.5 Volume to be emitted: Maximum in any one day : 51 m3 Maximum rate per hour : 35 m3 Up to January Jan. 1998 to Mar. From March 1999 1998 1999 mg/l mg/l mg/l BOD 115 100 75 COD 500 400 300 Suspended Solids 400 200 100

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Oils, Fats & Grease 30 20 20

Sulphates (as SO4) 100 100 100 Nitrates (as N) 10 5 5 Ammonia (as N) 130 50 10 Kjeldahl Nitrogen 75 50 50 Total Phosphorus (as P) 80 40 15 Chlorides 200 200 200

In terms of pollutional load, the IPC Licence permits 38 kg/d BOD to be discharged. This equates to a population equivalent of 635 approximately. However recent discussions with Glanbia’s environmental staff have indicated that the industry is in breach of their IPC discharge parameters. This is due to a variety of factors not least an increase in production at the Glanbia’s Edenderry plant. It is estimated by Glanbia that they are currently contributing a daily pollutional load to the works of 68 kg BOD/day. This figure is derived both by using figures produced by Glanbia’s environmental staff and the results of an independent Flow and Load Survey which was carried out at the plant in March 2003. This would equate to a population equivalent of 1,035 approximately.

The total estimated industrial load to the Edenderry Works is currently calculated at 1,393 p.e. This figure comprises the 1,035 p.e. contribution from Glanbia set out For inspection purposes only. Consent of copyright owner required for any other use. above plus a 358 p.e. loading from S.C.A. Packaging and Drummond Feeds and from Dry Industries on the Rhode Road.

The potential for the major industry Glanbia expanding in the coming years is examined further in the medium and high categories outlined below. In terms of the low growth category it is estimated that a potential increase in industrial loading to the works from new industry to the order of 600 p.e. could be anticipated. This figure is derived from an allowance for organic growth of existing industry plus an allowance for the anticipated increase in industry which would be needed to sustain an increased workforce. The increased workforce would be as a direct result of the anticipated increase in domestic population as set out earlier in this section.

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Thus it is estimated that, on a 25 year horizon, the anticipated industrial load to the Edenderry Works could equate to 1,990 p.e.

Educational

There are two primary schools and two secondary schools served by the Edenderry network. Details of the current size of these establishments are given in Table 4.3.

Table 4.3 – Loading from Educational Institutions Hydraulic Facility Numbers BOD Load Load Teachers Pupils kg/d m3/day Saint Mary’s Boys N.S. 13 210 4.46 10.035 Saint Mary’s Girls N.S. 30 475(1) 10.1 22.725 Saint Mary’s Secondary School 46 700 14.92 33.57 Oaklands Community School 26 355 7.62 17.145 Totals 115 1740 37.1 83.475 Note (1) Boys also attend this school until the age of 8yrs.

The wastewater from the above facilities will be domestic and a hydraulic flow of 45 l/h/day in nature and is assumed to have a BOD loading of 0.02 kg BOD/person/day. Using the hydraulic loading the existing P.E. contribution from the school is For inspection purposes only. Consent of copyright owner required for any other use. calculated at 375. The 2015 and 2028 P.E. contributions from education are 534 and 785 respectively.

Commercial

Exact details of the commercial contributions have been difficult to establish. However measured organic loading to the works has been assessed at 7,773 p.e. The known organic contributions are 5,125 p.e. from domestic, 1,393 p.e. from industry and 375 p.e from the schools. This would therefore imply that the commercial contribution is 880 p.e.

Clearly if the domestic and industrial loadings develop over the coming years as outlined above, then an increase in mixed use commercial development shall be

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necessary to serve this increase. Already a number of developers have expressed interest in constructing leisure and retail facilities within the town to cater for their planned residential developments.

Thus estimated commercial contributions of 1,320 p.e. in 2015 and 1,760 p.e. in 2028 are anticipated.

Summary

Based on the topics discussed above the anticipated loadings to the works based on the low category projection is outlined in Table 4.4 below.

Table 4.4 – Current and Future Population Equivalents - Low PE Component 2003 2015 2028 Domestic 5,125 6,986 9,945 Industrial 1,393 1,490 1,990, Commercial 880 1,320 1,760 Educational 375 534 785 Total 7,773 10,330 14,480

For inspection purposes only. Consent of copyright owner required for any other use. 4.4 Medium Growth Trend

The anticipated loadings from the domestic, commercial and educational elements of the catchment remain the same as outlined above. The medium category scenario is defined based on the following: i) The potential from the major industrial contributor Glanbia expanding. ii) The potential for effluent from rural parts of Co. Kildare close to the Co. Offaly border being pumped to the works. i) Industry

As outlined above Glanbia’s IPC Licence permits a pollutional load of 38 kg/d BOD to be discharged to the municipal sewer at Edenderry. However the current

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pollutional load being discharged is calculated at 68 kg BOD/day. This would equate to a population equivalent of 1,035 approximately.

Recent discussions with representatives of Glanbia has indicated that the company would intend consolidating their operations at Edenderry. This is as a direct result of the closure of a Glanbia plant at Rooskey, Co. Longford. In order to allow production at the Edenderry plant to increase Glanbia have indicated that they intend to upgrade their on-site wastewater treatment plant to cater for the increased loads. Following this upgrade a revised IPC Licence shall be sought from the EPA which shall permit a pollutional load of 270 kg BOD/day to be discharged to the municipal sewer. This would equate to a population equivalent of 4,500 being delivered to the Edenderry works.

Thus it is estimated that if the expansion of the Glanbia industry at Edenderry were to proceed the projected industrial contributions at Edenderry in the years 2015 and 2028 would equate to 4,955 p.e. and 5,455 p.e. respectively. As similar allowance for organic growth of additional industry as outlined in the low category projection has also been included in these figures. ii) Pumped Flows from Co. Kildare

For inspection purposes only. Consent of copyright owner required for any other use. The potential for effluent from rural parts of Co. Kildare close to Edenderry and the Co. Offaly border have been discussed earlier in this section. The anticipated loadings from both these catchments equates to 4,800 p.e.

Summary

Based on the topics discussed above the anticipated loadings to the works based on the medium category projections is outlined in Table 4.5 below.

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Table 4.5 – Current and Future Population Equivalents - Medium PE Component 2003 2015 2028 Domestic 5,125 6,986 9,945 Industrial 1,393 4,955 5,455 Commercial 880 1,320 1,760 Educational 375 534 785 Catchments - Kildare 4,800 Total 7,773 13,795 22,745

4.5 High Growth Trend

Domestic

The Edenderry Town Development Plan which is contained in the Offaly County Council Development Plan 2003 is shown on Drawing No. 20290/08. This Land Use Zoning Map indicates that approximately 287 ha of land is zoned for residential development. If it is assumed that all this land is developed by 2028 at a housing density of 20 houses / ha with an average occupancy of 2.9 persons per house then the domestic population would be 16,650 approximately. For the purposes of this For inspection purposes only. Consent of copyright owner required for any other use. evaluation it has been assumed that this figure 16,650 shall represent the total population figure for the catchment rather than the increase above the existing (5,125). This is because the majority of the existing population reside in infill developments which already form part of the land zoned for future residential development.

If the population were to increase to a figure of 16,650 this would represent an average annual growth rate of 5.1%.

Industrial

The amount of land zoned for industrial uses in Edenderry is approximately 43 ha. It is envisaged that with the exception of Glanbia’s future expansion this will primarily

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come under the category of light to medium industry. The water demand for such industry is approximately 28 m3/hectare/day. In calculating wastewater flows from this it is assumed that 95% of this demand goes back into the sewerage system. Therefore, the contribution from industry to the system will be approximately 1,204 m3/day. This would equate to a population equivalent of 5,350. However as the “medium” industry loading is higher at 5,455 p.e. due to the potential expansion of Glanbia it has been decided to adopt this latter figure to represent future industrial loading in the high category.

Commercial and Educational

A review of commercial and public / educational zonings within the town has revealed that the projected loadings for both in the low and medium categories should also be applied to this category.

Summary

Based on the topics discussed above the anticipated loadings to the works based on the high category projections is outlined in Table 4.6 below.

Table 4.6 – Current and Future For Population inspection purposes Equivalents only. - High Consent of copyright owner required for any other use. PE Component 2003 2015 2028 Domestic 5,125 10,462 16,650 Industrial 1,393 4,955 5,455 Commercial 880 1,320 1,760 Educational 375 534 785 Catchments - Kildare 4,800 Total 7,773 17,271 29,450

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4.6 Phasing of the Works

Edenderry has been designated as a District Centre within the 2003 Offaly County Council Development Plan. As such is a focal point for development in the East Offaly region. The Plan envisages the provision of adequate infrastructure and services to the town to allow residential, commercial and industrial development to proceed. The importance of the town is further enhanced due to its location on the border of the Greater Dublin Area. The current upgrading of transportation links with Dublin shall serve to further strengthen the development of the town as a commuter centre within the region.

The Low, Medium and High Projections for growth of the town outlined in Sections 4.3 to 4.5 address various development scenarios over a 25 year horizon. As a variety of factors, including market forces, shall determine how development of the town shall proceed it is impossible to predict with certainty which category represents the most realistic option. It is important therefore that the expansion of Edenderry Sewerage Scheme take place on a phased basis to ensure value for money and allow planned progressive development.

It is therefore recommended that the expansion of the WWTW’s take place on a

For inspection purposes only. phased basis as follows. Consent Each of copyrightPhase owner shall required represent for any other an use. increase in treatment capacity

at the works of 7,500 p.e. and correspond with the low, medium and high categories.

Table 4.7 – Phased Expansion of Edenderry WWTW’s Phase P.E. Year Review Phase I 14,500 2010 2008 Phase II 22,000 2015 2013 Phase III 29,500 2028

As outlined in Table 4.7 above the Phase I expansion shall involve the expansion of the Edenderry WWTW’s from a current design population equivalent of 7,000 to 14,500. This figure represents the total potential future population equivalent of the town in 2028 as derived in the low category. Thus it may well be that no further expansion of the works beyond its Phase I capacity is needed. However if the

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medium or high category projections develop it is possible that this Phase I Expansion may only provide capacity to the year 2010. Likewise whilst the Phase II Expansion may provide capacity to 2028 if the high projection scenario were to develop then full capacity would be reached by 2015. It is recommended that a full review of census figures and loadings to the works be carried out in the years 2008 and 2013 to determine whether Phase II (Medium) and Phase III (High) should proceed.

It is recommended that an Environmental Impact Statement be prepared at this stage for the ultimate (Phase III) loading of 29,500 p.e.

Finally due to current development pressures in Edenderry it is proposed to provide an initial 2,500 p.e. upgrade to the plant. This works shall be procured through a developer-led Advance Works Contract and shall be established in a modular-type format in order that it can be readily incorporated in the future phased works set out in this report.

For inspection purposes only. Consent of copyright owner required for any other use.

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5. EFFLUENT QUALITY

5.1 Receiving Waters

The River Boyne is the main watercourse in the region and flows from the east to the west through the north of the Edenderry catchment area. The existing treatment works site is located to the west of the town and the existing outfall is to the River Boyne. The outfall is approximately 1400m long. The approximate location of the discharge to the River is 1300 metres north of the existing and proposed treatment works. The impact of the proposed scheme on the River Boyne will be examined in detail in this section of the Report.

5.2 Effluent Quality

It is proposed to discharge the treated effluent from the Wastewater Treatment Works to the River Boyne. The primary objective in setting an effluent quality standard for the works is to ensure that the effluent quality must comply with all current statutory environmental regulations applying to discharges to freshwaters. The relevant regulatory guidelines in this case are found in the following documents:

For inspection purposes only. • Statutory InstrumentConsent (S.I.) of copyrightNo. 419owner requiredof 1994, for any otherEnvironmental use. Protection Agency

Act, 1992; (Urban Wastewater Treatment) Regulations, 1994. S.I. 419 gives effect in Ireland to the EU Urban Wastewater Directive of 1991 (91/271/EEC).

• Urban Wastewater Treatment Regulations, 2001 (S.I. No. 254 of 2001). Revoking the EPA Act 1992, giving further effect to the Council Directive 91/271/EEC.

• Local Government (Water Pollution) Act, 1977 (Water Quality Standards for Phosphorus) Regulations, 1998. S.I. No. 258 of 1998.

• The River Boyne Water Quality Management Plan, 1997.

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5.3 Urban Wastewater Treatment Regulations

Since this stretch of the River Boyne have not been classified as a “sensitive” water under the terms of the Urban Wastewater Treatment Regulations, the minimum effluent standards to be applied, as set out in the Second Schedule, Part I of S.I. 254, are given in Table 5.1.

Table 5.1a – Urban Wastewater Treatment Regulations Effluent Standards

Parameter Concentration Min. % Reduction *

BOD5 25 mg/l O2 70 – 90 (without nitrification)

COD 125 mg/l O2 75

Total Suspended Solids 35 mg/l 90

* Reduction in relation to influent load.

However, Phase I of the proposed new works will have a p.e. of more than 14,500. Under S.I.254, page 5, article 4., part 2 (a) “a sanitary authority shall provide treatment plants which provide more stringent treatment than secondary treatment or an equivalent treatment in respect of all discharges from agglomerations of more than 10,000 into sensitive areas or into the relevant catchment of sensitive areas where the

discharges contribute to the For pollution inspection purposes of only.these areas.” Although the Boyne at Consent of copyright owner required for any other use. Edenderry is not classed as “sensitive” it certainly discharges into the catchment of the section of the Boyne (6.5km section downstream of sewage treatment works outfall at Blackcastle, Navan, County Meath) which is classed as “sensitive”. The additional minimum effluent standards which apply to watercourses which are designated as sensitive are set out in Table 5.1b.

Table 5.1b – Urban Wastewater Treatment Regulations Effluent Standards – “Sensitive”

Parameter Concentration Min. % Reduction *

Total Phosphorus 2mg/l 80

Total Nitrogen ** 15 mg/l 70-80

* Reduction in relation to influent load. ** Total Nitrogen meaning the sum of total Kjeldahl nitrogen, nitrate- nitrogen and nitrite-nitrogen.

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5.4 River Boyne Water Quality Management Plan (WQMP)

The WQMP for the River Boyne provides a comprehensive evaluation of the water resource, including catchment hydrology, water quality, water uses and pollutional loads. It points out that in the case of the River Boyne the main uses to be considered are abstraction for potable and industrial supply and salmonid fisheries. Consideration of the published criteria indicate that those applying to fisheries would also offer adequate protection, in most situations, to abstractions. It recommends however that wastewater discharges should not be permissible for a specified distance upstream of a public water supply abstraction point. The water quality standards recommended in the WQMP are set out in Table 5.2.

Table 5.2 – Water Quality Standards (WQMP) Parameter Recommendation

Dissolved Oxygen (mg/l O2) > 4 for 99.9% of the time > 6 for 95% of the time > 9 for 50% of the time

BOD5 (mg/l O2) <5 for 95% of the time < 3 for 50% of the time

Non-Ionised Ammonia (mg/l NH3) < 0.02 for 95% of the time For inspection purposes only. Consent of copyright owner required for any other use. Total Ammonium (mg/1 NH4) < 1 for 95% of the time < 0.2 for 50% of the time Nitrate + Nitrite (mg/l N) < 11 for 99.9% of the time < 5 for 95% of the time < 3 for 50% of the time

The achievement of a salmonid water quality is a key objective of the WQMP. The River Boyne is included in the designated salmonid rivers in Schedule 1 of the European Communities (Quantity of Salmonid Waters) Regulations, S.I. 293/88. This Statutory Instrument (S.I.) gives effect in Ireland to EU Directive 78/659/EEC, which governs the quality of fresh waters needing protection or improvement in order to support fish life. The water quality requirements of S.I. 293/88 are given in Table 5.3.

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Table 5.3 – European Communities (Quality of Salmonid Waters) Regulations, S.I. 293/88

Parameter Value

Dissolved Oxygen (mg/1O2) 50% > 9 PH > 6 < 9 Suspended Solids (mg/1) < 25

BOD5 (mg/O2) < 5

Nitrite (mg/1 NO2) < 0.05

Non-Ionised Ammonia (mg/1 NH3) < 0.02

Total Ammonium (mg/1 NH4) < 1

5.5 Aspects of Boyne Catchment Hydrology

There is one hydrometric station in the Upper River Boyne catchment at the Kishawanny Bridge (07026). Until recently this station was classed as “inactive” by the Environmental Protection agency. This station is located approximately 2 km upstream of the existing outfall pipe. The river flow at the outfall pipe is defined by the following range of parameters:

Catchment Area 54 km2 95 Percentile Flow 0.143 m3/sec

For inspection purposes only. Consent of copyright owner required for any other use. The 95 percentile flow at the outfall location is based on the estimated catchment area at this location and the average yield calculated for the upper catchment region and for the recorded 95 Percentile flow for the Kishawanny Bridge (0.110 m3/sec). A new “state of the art” hydrometric station has just been installed at the Kishawanny Bridge. This new station in addition to flood studies currently being conducted on the Upper Boyne should confirm the 95 Percentile flow at the outfall pipe which is given above. It is possible that the figure of 0.143 m3/s is slightly too conservative or vice-versa. In either case adjustments to the requirements of the design would be immediately evaluated and implemented.

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5.6 River Boyne Water Quality

Water Quality Data for the River Boyne are given in Table 5.4. This data is derived from a sampling station at Boyne Bridge 2 km upstream of the existing discharge point and at Kinnafad Bridge approximately 0.5 km downstream of the discharge point. Q values for the River Boyne at these locations are presented in Table 5.5.

Table 5.4 – Water Quality Data (Offaly County Council) for Boyne River (Chemical Analysis) Jan 2002-July2003 Parameter Dissolved Oxygen BOD (mgO2/l) (mgO2/l) Station Min Med. Max. Min. Med. Max. 2 km U/S 5.08 9.32 10.11 0.56 2.09 3.18 0.5 km D/S 6.21 8.94 10.19 0.89 2.5 7.08

Parameter Total Ammonia Orthophosphate (mg/lP) (mg/l N) Station Min Med. Max. Min. Med. Max. 2 km U/S 0.141 0.263 0.439 0.026 0.07 0.15 0.5 km D/S 0.163 0.584 1.773 0.052 0.1215 0.62

Table 5.5 – Water Quality Data (EPA) for River Boyne at Edenderry (Q Values)

Biological Quality Rating Q Value

Year 1971 1973 1975For inspection 1977 purposes 1979only. 1981 1986 1990 1994 1997 Consent of copyright owner required for any other use. 2 km u/s 2-3 3-4 3-4 3 4 4 4 3 4 2-3 0.5 km d/s 2-3 2 - 3 2 1-2 2-3 4 4 - 3 2

where: Q5, Q4-5, Q4 : Unpolluted Q3-4 : Slightly Polluted Q3, Q2-3 : Moderately Polluted Q2, Q1-2, Q1 : Seriously Polluted

The river upstream of the outfall is generally classified as moderately polluted. However, the river downstream of the outfall is generally classified as seriously polluted since 1997.

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5.7 Required Effluent Standards

The primary regulatory guideline for effluent standards is the EU Urban Wastewater Treatment Regulations, 2001 which is implemented in Ireland through S.I. 254 of 2001 and the Water Quality Standards for Phosphorus (S.I. 258 of 1998).

While the requirements of the Urban Wastewater Treatment Regulations are set, water quality requirements are dependant on the background values and the 95 percentile flow in the river (i.e. assimilation capacity).

The BOD Waste Assimilation Capacity (WAC) is defined as:

WAC = (Cmax – Cback) x F95 x 86.4 kgBOD/day

Where: Cmax = maximum permissible BOD concentration (= 5 mg/l)

Cback = background (upstream) BOD concentration 3 F95 = 95 percentile flow (m /s) 86.4 = conversion factor

From analysis of the sampling results presented in Table 5.4 and 5.5 the background

value for BOD is taken as 2.09 For mg/l. inspection purposes only. Consent of copyright owner required for any other use.

BOD WAC = (5-2.09) x 0.143 x 86.4 = 35.95 kg BOD/day

Phosphorous

The phosphorous loads permitted in the river are governed by the Phosphorous Regulations (S.I. 258 of 1998). The salient features of these regulations are summarised below:

a) The standards quoted are in terms of Molybdate – Reactive Phosphate.

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b) The concentrations measured are median values determined using a minimum of 10 samples taken at intervals of four weeks or longer in any 12 consecutive month period.

c) The existing biological quality rating / Q index is to be improved to meet the minimum target biological quality rating / Q index as detailed in the Regulations.

The regulations state that the existing biological quality rating assigned between 1st January 1995 and 31st December 1997 is the rating upon which the improvements in Water Quality will be judged. In the case of the River Boyne the Q index upstream of the existing treatment plant at Boyne Bridge was determined as Q2-3 in 1997 and downstream received a Q index of Q2.

The minimum target ratings and concentrations for these stretches of water as defined in the Phosphorous regulations are given in Table 5.6.

Table 5.6 – Phosphorous Regulations Target Ratings and Concentrations

Existing Biological Minimum Target Molybdate Reactive Quality (Q) Biological Quality Phosphate Median Rating/Q (Q) Concentration IndexFor inspection purposes only.Rating /Q Index Consent of copyright owner required for any other use. (μg P/L) U/S 2-3 3 70 D/S 2 3 70

The assumption is made that the upstream water quality will improve to a Q3 rating (i.e. 70 μg P/1) and the stretch into which the WWTW discharge is proposed will be improved to a Q3 (i.e. 70 μg P/l). Therefore there is no allowable increase in the MRP Median Concentration. However in 1994 the waters upstream of the works has a Q rating of Q4 so it would seem that the upstream water quality should greatly improve provided proper agricultural and other controls were in place. Making a further assumption that this will be carried out before 2007 then the upstream water quality will improve to a Q4 rating (i.e. 30 μg P/l). Therefore the allowable increase in the river is 40μg P/l.

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Using the Waste Assimilation Capacity calculation the allowable increase in MRP concentration equates to the following loads to the river:

At 95% ile flow : 0.494 kg MRP/d.

The Total P load will be 1 kg/d as MRP approximately makes up 50% of the Total P load. As the regulations determine the Q index using the median of 10 samples over 12 months the enforcement of the load determined from 95%ile flows (0.143 m3/sec) is extremely onerous. The more realistic load is given by using the average flow in the river as this is more representative of the variable flows to be encountered during the 12 month sampling period. A value of 0.842 m3/s has been determined as the mean flow. Therefore it is assumed that the target MRP load to the river should be less than 2.9kg MRP/day. The Total P load will now be 5.8 kg/day as MRP approximately makes up 50% of the Total P load. Realistically 1mg/l of Total phosphorus is the best achievable effluent from the works thus 0.5mg/l is the best achievable MRP effluent from the works. For Phase I of the works a DWF of 3,262.5 m3/day will deliver 1.631 kg/day of MRP. For Phase II of the works a DWF of 4,950 m3/day will deliver 2.475 kg/day of MRP still well within the Target MRP load. For Phase III of the works the DWF of 6637.5 m3/day will deliver 3.319kg/day of MRP which exceeds the target MRP load. However the WAC equation does not take into

account the effect of the efflue Fornt inspection in the purposes river only. and thus for a situation like Edenderry Consent of copyright owner required for any other use. where the river is suffering from relatively low flows and the effluent flow will in this case make up some 9% of the river flow downstream of the effluent outfall. The MRP concentration in the river at this location is determined by:

()MeanFlowInRiver × MRP(riverupstream) + ()DWF29500 × MRP(effluent) MRP()riverdownstream = DWF29500 + MeanFlowInRiver

()72835× 30 + (6637.5× 500) MRP(riverdownstream) = 72835 + 6637.5 = 69μg P/l

This figure is less than the Q3 Target MRP level in the river of 70μg P/l.

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5.8 Recommended Effluent Standards for the River Boyne at Edenderry

The main considerations that determine the effluent standards to set are derived from the following:

• The requirement to meet the receiving water quality standards as set out in the WQMP.

• The statutory requirement to meet the minimum effluent standards as set out in S.I. 254 of 2001.

• The requirement as set out in the Phosphorous Regulations to improve the Biological Quality Rating of the receiving waters in line with preset target ratings.

The receiving water quality issues have been reviewed in the previous sub-section. Before selecting target effluent parameters it is necessary to assess the effects of critical parameters on the receiving waters.

With a proposed Phase I population equivalent of 14,500 P.E., a Phase II population equivalent of 22,000 P.E. and a Phase III population equivalent of 29,500 the

projected flows and loads are asFor inspectionfollows: purposes only. Consent of copyright owner required for any other use.

Table 5.7 – Projected Flows and Loads Phase I Phase II Phase III Concentration (14,500 PE) (22,000 PE) (29,500 PE) DWF 3262.5 m3/day 4950 m3/day 6637.5 m3/day 225 l/head/day BOD Load 870 kg/day 1320 kg/day 1770 kg/day 60 g/head/day S.S. 1087.5 kg/day 1650 kg/day 2212.5 kg/day 75 g/head/day Total Nitrogen 145 kg/day 220 kg/day 295 kg/day 10 g/head/day P 36.25 kg/day 55 kg/day 73.75 kg/day 2.5 g/head/day

The available dilution at the existing outfall location is given in Table 5.8.

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Table 5.8 – Available Dilutions DWF 95% Flow Dilution Factor Phase I 3262.5 m3/day 12355 m3/day 3.8 Phase II 4950 m3/day 12355 m3/day 2.5 Phase III 6637 m3/day 12355 m3/day 1.86

Taking a calculated WAC value of 35.95 kg/day the required standards for BOD removal are as follows:

Table 5.9 – BOD Parameters BOD (Influent) BOD effluent % Removal Effluent Required Concentration Phase I 870 kg/day 35.95 kg/day 95.8% 11 mg/l Phase II 1320 kg/day 35.95 kg/day 97.2% 7.2 mg/l Phase III 1770 kg/day 35.95 kg/day 98% 5.4 mg/l

Table 5.10 shows the percentage removal rate required for total phosphorous for the treated effluent. MRP phosphorous makes up 50% of total Phosphorus as a general rule. A load of 7 kg/day is made possible due to the higher level of flow to the river which has a dilution factor that is taken into account in Section 5.7.

However as the existing Wastewater For inspection purposes Treatment only. Plant is designed to achieve an Consent of copyright owner required for any other use. Effluent Phosphorous Concentration of 1 mg/l it is proposed to adopt this standard for the future phased expansions.

Table 5.10 – Phosphorous Parameters P Load P Load % Removal Effluent Influent Effluent Required Concentration Phase I 36.25 kg/day 6 kg/day 83.4% 1.8 mg/l Phase II 55 kg/day 6 kg/day 89.1% 1.2 mg/l Phase III 73.75 kg/day 7 kg/day 90.5% 1 mg/l

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5.9 Summary of Effluent Standards Adopted for Discharge to the River Boyne at Edenderry

The final effluent standards adopted for treatment process selection and preparation of preliminary designs and layouts are summarised as follows:

Table 5.11(a) – Phase I Effluent Standards for River Boyne Parameter Concentration (mg/l) % Removal BOD 11 > 95.8 S.S. * 15.4 > 95.3 Total Phosphorous 1 > 83.4 Total Ammonia. 5 > 88.75%

Table 5.11(b) – Phase II Effluent Standards for River Boyne Parameter Concentration (mg/l) % Removal BOD 7.26 > 97.2 S.S. * 10.1 > 96.9 Total Phosphorous 1 > 89.1 Total Ammonia. 3.2 > 92.59%

Table 5.11(c) – Phase III Effluent For inspectionStandards purposes for only. River Boyne Consent of copyright owner required for any other use. Parameter Concentration (mg/l) % Removal BOD 5.4 > 98 S.S. * 7.55 > 97.7 Total Phosphorous 1 > 90.5 Total Ammonia. 2.4 > 94.47%

* SS level determined by 7:5 ratio to BOD (i.e. 35/25)

5.10 Discharge Options to the River Boyne

The existing outfall pipeline to the River Boyne has adequate hydraulic capacity to handle increased flows up to the Phase III ultimate DWF at 6637.5 m3/day. The pipeline is capable of handling peak flows up to 4 DWF at the ultimate (Phase III) loading.

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6. WASTEWATER TREATMENT OPTIONS

6.1 General

The broad function of a municipal wastewater treatment system is the separation of the polluting load from its carrier water. The processes which effect this separation generate a number of solid residue streams as well as the treated effluent stream. The solid reside streams may require further processing to render them suitable for environmental disposal.

The liquid treatment stream may incorporate some or all of the following stages of treatment: • preliminary treatment • primary treatment • secondary treatment • tertiary treatment

A preliminary treatment stage is invariably included in municipal treatment systems, typically incorporating screening and grit separation. It generates two categories of waste solids, screenings and grit. For inspection purposes only. Consent of copyright owner required for any other use.

Primary treatment involves the removal of suspended particulate matter from the wastewater by sedimentation or flotation processes. It generates clarified effluent and primary sludge streams.

Secondary treatment involves the removal of suspended and colloidal particular matter in addition to dissolved organic matter, using biological, physiochemical or membrane processes. Biological processes are invariably used in municipal wastewater treatment systems, where secondary treatment is required. Secondary treatment generates a clarified liquid effluent and a sludge residue.

Tertiary or advanced treatment is included in municipal wastewater treatment streams where low residual effluent nitrogen and phosphorus levels are required or where the

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residual suspended solids must be reduced to a very low level. Advanced nitrogen removal is typically achieved by biological processes; advanced phosphorus removal may be achieved by biological and/or chemical precipitation processes; filtration processes are applied to achieve an advanced level of suspended solids removal. The solids streams may include screenings, grit, primary sludge and a variety of biosludges.

The technical considerations to be taken into account in the selection and design of appropriate treatment technologies for the liquid and solids streams can be conveniently grouped for discussion purposes under the following headings:

(i) size of works, including phased development (ii) required effluent quality (iii) options for sludge disposal (iv) site constraints, including environmental impacts

Economic evaluation is also applied to the selection/design process to ensure that the treatment system represents good value for money, taking into account capital and running costs.

6.2 Treatment Plant Capacity For inspection purposes only. Consent of copyright owner required for any other use.

The treatment works is to be developed in three phases for the following design loadings:

(a) Organic Loading

P.E. BOD (kg/d)

Phase I 14,500 870 Phase II 22,000 1350 Phase III 29,500 1770

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(b) Hydraulic Loading The wastewater network is being designed to cater for peak flows up to 6 DWF and the maximum flow to full treatment will be 3 DWF. Flows between 3 and 6 DWF will be diverted to storm tanks where a retention time of 2 hours will be provided at peak flows.

Flow to Full Flow to Storm DWF Treatment Treatment m3/day m3/day m3/hr Phase I 3,262.5 9,787.5 407.8 Phase II 4,950 14,850 618.7 Phase III 6,637.5 19,912.5 829.7

Due to the current development pressure in Edenderry it is proposed to provide an initial 2,500 p.e. upgrade to the plant. This works shall be procured through a developer-led Advance Works Contract and shall be established in a modular-type formal in order that it can be readily incorporated in the future phased works set out in this report.

6.3 Treatment Process Selection

For inspection purposes only. Consent of copyright owner required for any other use. In this Section various Process Options for the treatment of wastewater will be discussed.

Process Option 1 Preliminary Treatment Extended Aeration Plant Secondary Clarifier Stormwater Holding Tank

Process Option 2 Preliminary Treatment SBR Activated Sludge System Stormwater Holding Tank

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Process Option 3 Preliminary Treatment Membrane Bioreactor Sludge Holding Tank Stormwater Holding Tank

The preliminary treatment stage and stormwater holding tank is common to all the above options and includes the following: ƒ mm bar screen with ancillary screenings processing facilities ƒ Grit separator by detritor or grit channel with ancillary grit handling system ƒ Flow measurement flume ƒ Storm overflow weir to divert flows greater than 3 DWF to stormwater holding tank ƒ Stormwater holding tanks with a retention of 2 hours at peak flows and tipping buckets (and/or tank flushing units) for automatic cleaning of tanks ƒ Stormwater return pumping station

All the above process options produce a single stream sludge residue. The options for sludge handling are discussed separately later in this Section.

An examination of the four selected Process Options was carried out with the

following observations: For inspection purposes only. Consent of copyright owner required for any other use.

6.3.1 Process Option 1 (Extended Aeration Plant)

The extended aeration process is an activated sludge reactor designed to produce a fully mineralised effluent and an aerobically stabilised sludge. It is normally used without pre-sedimentation, based on a retention time of 24 to 30 hours. It is normally operated as a continuous process in conjunction with a downstream sedimentation process from which settled sludge is recycled back to the aeration basin.

A fine bubble diffused air aeration system will be installed in the aeration basin, and provision should be made for an anoxic zone (2 hours retention) for nitrogen removal. Chemical dosing for phosphorous reduction will also be provided. An anaerobic zone should also be provided to encourage biological removal of phosphorous, but would

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need to be operated in conjunction with chemical dosing to achieve the required effluent standard.

Preliminary Designs have sized this process option as follows:

Phase I: Three No. Aeration Tanks each with its own Anoxic and Anaerobic Zones and each sized for 2,500 p.e. Each Anaerobic Zone will have a volume of 48 m3 (i.e. Dimensions 4 x 2 x 6 m) Each Anoxic Zone will have a volume of 180 m3 (i.e. Dimensions 10 x 3 x 6 m) Each Aeration Basin will have a volume of 600 m3 (i.e. Dimensions 10 x 10 x 6 m) These figure assume a sludge age of >10 days and a MLSS concentration of 3,000 mg/l Flow will then continue onward to the 2no Final Clarifiers, each clarifier is sized for 3,750 p.e. Dimensions as follows: Diameter 12 m Sidewall depth 3.5 m Slope of floor 11o

Phase II: For inspection purposes only. Consent of copyright owner required for any other use. 2 No. Aeration Tanks each with its own Anoxic and Anaerobic Zones and each sized for 3,750 p.e. Each Anaerobic Zone will have a volume of 72 m3 (i.e. Dimensions 6 x 2 x 6 m) Each Anoxic Zone will have a volume of 270 m3 (i.e. Dimensions 10 x 4.5 x 6 m) Each Aeration Basin will have a volume of 900 m3 (i.e. Dimensions 15 x 10 x 6 m) These figures assume a sludge age of >10 days and a MLSS concentration of 3,000 mg/l Flow will then continue onward to the 2no Final Clarifiers, each clarifier is sized for 3,750 p.e. Dimensions as follows: Diameter 12 m Sidewall depth 3.5 m Slope of floor 11o

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Phase III: 2 No. Aeration Tanks each with its own Anoxic and Anaerobic Zones and each sized for 3,750 p.e. Each Anaerobic Zone will have a volume of 72 m3 (i.e. Dimensions 6 x 2 x 6 m) Each Anoxic Zone will have a volume of 270 m3 (i.e. Dimensions 10 x 4.5 x 6 m) Each Aeration Basin will have a volume of 900 m3 (i.e. Dimensions 15 x 10 x 6 m) These figures assume a sludge age of 10 days and a MLSS concentration of 3,000 mg/l Flow will then continue onward to the 2no Final Clarifiers, each clarifier is sized for 3,750 p.e. Dimensions as follows: Diameter 12 m Sidewall depth 3.5 m Slope of floor 11o

Nominally this process will produce a 25:35 BOD:SS effluent. In order to meet the stringent requirements of the effluent, a further tertiary treatment Phase would be required. For each Phase large Anoxic Zones have been sized to enable the maximum removal of nutrients.

Layout details and sections of Forthis inspection propo purposessed only.arrangement are shown on Drawing Nos. Consent of copyright owner required for any other use. 20290/09 and 20290/10.

6.3.2 Process Option 2 (SBR)

The SBR activated sludge system combines aeration and sedimentation in the same tank, through operation in a batch mode, based on a cycle of fill, aerate, settle and decant. The overall cycle time is typically 12 hours. With a single SBR basin, influent flow balancing is required to store the wastewater during the settle and decant phases of the cycle. With two or more basins, the basin cycles can be staggered to allow continuous inflow. More recent advanced SBR processes (e.g. Unitank) include multi stage tanks for biological nitrogen and phosphorous removal.

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As stormwater storage is being provided at the plant the SBR balancing tank volume could be provided within the storm tank.

Phase I: Three No. SBR tanks each sized for 2,500 p.e. As the tanks are sized for 12 hours hydraulic retention time each tank will have a volume of 290 m3 (i.e. Dimensions 8 x 10 x 4 m)

Phase II: Two No. SBR tanks each sized for 3,750 p.e. As the tanks are sized for 12 hours hydraulic retention time each tank will have a volume of 430 m3. (i.e. Dimensions 10 x 11 x 4 m)

Phase III: Two No. SBR tanks each sized for 3,750 p.e. As the tanks are sized for 12 hours hydraulic retention time each tank will have a volume of 430 m3 (i.e. Dimensions 10 x 11 x 4 m)

A Balancing tank of 635 m3 capacity would also be required. A capacity far in excess of this would be provided by the proposed storm tank.

For inspection purposes only. Consent of copyright owner required for any other use. Nominally this process will produce a 25:35 BOD:SS effluent. In order to meet the stringent requirements of the effluent, a further tertiary treatment Phase would be required.

Layout details and sections of this proposed arrangement are shown on Drawing Nos. 20290/11 and 20290/12.

6.3.3 Process Option 3 (Membrane Bioreactor)

MBR Technology is a recently developed process for the treatment of wastewater to a high standard. The final effluent produced is fully disinfected and the plant footprint is smaller than conventional treatment plants. The process is a single stage process and has a low sludge yield, typically 0.45 kg ds/kg BOD and surplus sludge is

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removed at between 2-3%. The average sludge yield for an extended aeration process is 0.5 kg d.s/kg BOD removed. The process also produces low odour problems. The process does not require a primary or secondary settlement stage and removal rates of greater than 96% have been achieved for BOD and S.S. removal. Typically effluent

rates of 5:5:5 for SS, BOS and NH3.

The stringent effluent discharge levels which are required to be met in the long term may make this process seem most attractive. At present the operating and installation costs are also higher than the conventional treatment plant. This option could prove attractive if a design build operate performance specification and associated penalties was the preferred method of construction.

Layout details and sections of this proposed arrangement are shown on Drawing Nos. 20290/13 and 20290/14.

6.3.5 Conclusions

Process Options 1 and 2 are all activated sludge-based with a design sludge age of not less than 20 days, thereby producing an aerobically stabilised sludge residue. This sludge is suitable for transfer to the sludge holding tank (up to 14,500 p.e.) and future

tank (for populations above For14,500 inspection purposesp.e.) only.for further processing, dewatering and Consent of copyright owner required for any other use. removal to the Tullamore hub centre. Their hydraulic capacities are limited to 3 DWF, hence stormwater storage is required. The SBR option does not require an external clarifier, but requires upstream storage and inflow pumping. The quality and quantity of sludge generated by each of these treatment options is effectively the same. There is also little to differentiate them in terms of operating costs, maintenance costs, and overall process reliability.

Process Option 3 is a new process technology which could provide attractive as more stringent effluent requirements are required in the long term, as the membrane process effectively produces a fully disinfected effluent.

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6.3.6 Recommendations

The foregoing evaluation leads to the following recommendations:

Process Options 1, 2 and 3 provide appropriate alternative solutions, each of which produces an aerobically aerated sludge, suitable for processing and final disposal. As there is little to differentiate between these systems in terms of process performance, the selection of the most economically advantageous option is most reliably made through the competitive tendering process based on a treatment process performance specification.

6.4 Tertiary Filters

Due to the effluent standard required for the discharge to the Boyne River the provision of tertiary filters is examined. There are a number of filters available on the market. For the purposes of this report the ‘DynaSand Filter’ was examined.

The DynaSand filter is based on the counter flow principle. The water to be treated is admitted through the inlet distributor in the lower section of the unit and is cleaned as it flows upward through the sand bed, prior to discharge through the filtrate outlet at

the top. The sand containing Forthe inspection entrappe purposesd only. impurities is conveyed from the tapered Consent of copyright owner required for any other use. bottom section of the unit by means of an air-lift pump to the sand washer at the top.

Cleaning of the sand commences in the pump itself, in which particles of dirt are separated from the sand grains by the turbulent mixing action. The contaminated sand spills from the pump outlet into the washer labyrinth in which it is washed by a small flow of clean water. The impurities are discharged through the wash water outlet while the grains of clean sand (which are heavier) are returned to the sand bed. As a result, the bed is in constant downward motion through the unit.

Thus, treatment and sand washing both take place continuously, enabling the filter to remain in service without interruption.

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Tertiary Filters are frequently used for the final filtration of biologically treated

wastewater. They primarily reduce the Suspended Solids and BOD5 concentrations in the effluent with no effect on the phosphorus levels. Tertiary Filters would be required for polishing the effluent from process options 1 & 2 to reduce BOD and SS.

6.5 Treatment and Disposal of Solids Residues

In treating the liquid stream, three types of solids residue are produced, screenings grit and sludge.

6.5.1 Screenings & Grit

In terms of the proposed works at Edenderry it is recommended that the most appropriate treatment of screenings is washing and compaction.

It is further recommended that a grit classifier be installed and the grit residue discharged to a closed container.

6.5.2 Sludge

The Sludge Management Plan 2001 for County Offaly examines a number of options For inspection purposes only. for the disposal of sewageConsent sludges of copyright in owner the required County. for any otherIt was use. recommended in this report

that dewatering facilities be provided at the Edenderry site and thus it would become a local hub centre for the area. At present the dewatering facilities at Edenderry, which consist of a picket fence thickener and a centrifuge, have a capacity of more than 14,000pe and a proposal for the construction of a sludge acceptance area to serve the sludge dewatering requirements (3,500 p.e.) from the locality is at Planning Stage. For Phase I of the works the existing dewatering facilities will prove more than adequate and it is proposed that further dewatering facilities be provided and commissioned as required as part of the Phase II works. This will provide dewatering for in excess of 29,500 p.e. which will meet the demands both of the WWTW at the Phase III horizon and of the WWTW responsibilities to act as a hub for local wastewater sludges.

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6.6 Augmentation of Flow and Balancing of Effluent Flow

Section 5 of this document outlines the fact that provided a high level of Tertiary Treatment or better is provided there is no difficulty in discharging the effluent from the Phase III loading to the existing outfall location on the River Boyne. Furthermore the outfall pipe is more than adequately sized for the hydraulic duty. However as there are periods of low flow in the River Boyne at Edenderry it may be useful to augment the flows to the river with clean water so that the negative environmental effects on the river are minimized. Similarly and simultaneously an “intelligent” outfall system could be used utilizing the proposed storm tank as a holding tank for balancing the load to the river throughout the day. Control for this balancing system would be by flowmeter in the river at the outfall in a hydraulic structure connected to a telemetry station with a radio and communicating the flow in the river every 15 minutes to the plants SCADA system and using this information to control the flow from the works to the river.

For inspection purposes only. Consent of copyright owner required for any other use.

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7. WASTEWATER COLLECTION NETWORK PROPOSALS

7.1 General

The existing wastewater network in Edenderry was discussed in Section 3 of this report.

7.2 Hydraulic Model

A hydraulic model of the existing collection system was constructed as set out in Section 3. This model identified capacity problems with the existing system under existing loadings and design rainfall events. The results of a CCTV Survey and SUS 2000 Survey of the structural condition of the existing pipelines and manholes are also presented in Section 3.

In this section the necessary upgrading works to the network are detailed to allow existing and future development to be handled in an efficient and environmentally sensitive manner. The works shall involve upsizing or replacement of existing sewer lines, the construction of relief sewers, upgrading of pumping stations and the construction of sewer extensions to serve lands zoned for development. For inspection purposes only. Consent of copyright owner required for any other use.

The repair and rehabilitation works necessary to the existing pipelines and manholes following the CCTV and SUS 200 to reduce blockages and infiltration to the network, shall also be set out in this section.

7.3 Methodology

As outlined in Section 4 of this report the future population equivalent for the town of Edenderry is expected to increase significantly over the coming years. Drawing No. 20290/08 presents the Land Use Zoning Map for Edenderry as set out in the Offaly County Development Plan 2003. This zoning map outlines the areas where future growth shall be concentrated. Table 7.1 below sets out the anticipated future population equivalent projections for Edenderry.

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Table 7.1 – Future Population Equivalent Projections PE Component 2003 2015 2028 Domestic 5,125 10,462 16,650 Industrial 1,393 4,955 5,455 Commercial 880 1,320 1,760 Educational 375 534 785 Catchments - Kildare 4,800 Total 7,773 17,271 29,450

The predicted future loadings as set out in Table 7.1 shall be input into the existing hydraulic model to examine performance. In accordance with the terms of the brief it shall be necessary to provide upgrading recommendations to cater for flows up to 2028. Thus flows equating to 29,500 p.e. shall be used in the analysis. However upgrading works or extensions to the existing system shall only be provided on a phased basis as follows:

i) upgrading works to existing sewers and pumping stations shall only be carried out where there are existing inadequacies or where inadequacies are to be For inspection purposes only. anticipated in the shortConsent ofterm. copyright owner required for any other use.

ii) extensions to the existing collection system shall only occur as and when development in these areas proceed.

As previously outlined in Section 3 the majority of the existing pumping stations in the catchment are overloaded during heavy rainfall events. These facilities will require to be upgraded and expanded for the existing and projected loadings. Two options have been considered as follows: i) increasing pumping capacity at each station to cater for future design flows from a 1 in 5 or 1 in 10 year return period event (>6 DWF ult), or ii) provide increased storage facilities at each station to limit the quantity of flows being pumped forward. The onward storage flow would be limited to a multiple of six times the upstream future dry weather flow (6 x DWF ult).

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The multiple of 6 times future ultimate Dry Weather Flow has been examined in the above options in order to avoid frequent spillages to adjoining watercourses none of which have the appropriate assimilative capacity. It is considered preferable that due to the generally combined nature of the existing network, traffic volume within the town and the fact that many pipelines run to the rear of properties that all flows should be pumped forward to the existing wastewater treatment works. Thus the high capital cost of providing extensive separate storm sewers throughout the town is avoided and flows are forwarded to a location where they can be handled in a proper manner.

Furthermore Option (ii) outlined above is considered preferable in that it would avoid excessive flows being pumped into the downstream sewers necessitating upsizing of same.

It shall also be necessary to examine each of the existing storm overflows within the collection system to determine how many can be removed or optimised by way of storage capacity in accordance with proper environmental practice.

Finally it shall be necessary to assess the capacity of the pipelines under design rainfall events. The pipelines shall be examined based on future loadings to

determine: For inspection purposes only. Consent of copyright owner required for any other use. a) the degree of surcharging during a storm of 1 year return period. b) the degree of significant flooding (>25 m3) during a storm of 5 year return period.

Where sewers fail on either of the above criteria recommendations for upgrading shall be provided. As a general rule pipelines shall be sized to cater for a 5 year design condition without surcharging.

In terms of extensions to serve future developments the land used zoning map as detailed on Drawing No. 20290/08 shall be examined and outline proposals presented.

Repair and rehabilitation works to pipelines and manholes shall be detailed in accordance with the results of the CCTV and SUS 2000 survey.

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7.4 Upgrading of Pumping Stations

7.4.1 General

Due to the topography of the catchment area all of the future development areas will ultimately be served by one or more of the existing pumping stations. Thus the anticipated increase in future population equivalent to an ultimate figure of 29,500 required to be allocated to a relevant pumping station for analysis purposes.

As outlined in Section 7.3 above, the design pumping rates for each of the upgraded pumping stations will be set at six times the upstream Dry Weather Flow. In order to simulate and quantify the design peak flows on a phased basis arriving at each of the pumping stations the model was run using peak dry weather flow (existing and future) in the absence of rainfall events. The results in terms of peak flows (pumping rates) to be handled at each pumping station are as set out in Table 7.2 below.

Table 7.2 - Pumping Station Peak Future Flows P.S. Ref. Pumping Rate (l/s) Phase III Phase II Phase I Connyborough 64 42 42 Clonmullen 10.5 7 7 For inspection purposes only. Carrick Road Consent of copyright 84 owner required for any other use.52 52

Derrycorris 36 23 23 Corkery Lane 12 12 12 Killane 36 23 23 Blundell Wood 6 6 6

Notes: 1. Unless otherwise stated, pump rate set to 6 times upstream dry weather flow (existing & future). 2. Flow rate at Corkery Lane was increased to reduce storage. 3. Minimum Submersible Pump Size of 6 l/s used for Blundell Wood. 4. Phase I Pumping Rates same as Phase II due to self-cleansing velocities.

In addition to altering the pump regime at each of the pumping stations, storage or balancing capacity was needed at some in order to limit the number of spills to a set amount per annum. As most of the accepting watercourses were found to have

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limited assimilative capacity it was decided that a limiting frequency of one spill every 2 years should be used.

The hydraulic model was run using peak future dry weather flow coupled with a return period of 1 in 2 years for the critical spill duration. This allowed the maximum spill volume at each pumping station to be determined and therefore the maximum volume of storage that would need to be provided at each facility. The results are presented in Table 7.3 below.

Table 7.3 - Pumping Station Storage Volumes Required

P.S. Ref. Storage Required (m3) Connyborough 3 Clonmullen 13 Carrick Rd 0 Derrycorris 0 Corkery Lane 13 Killane 73 Blundell Wood 7

It should be noted that the model was run with storm overflows removed from the system for the reasons outlined in Section 7.5 below. For inspection purposes only. Consent of copyright owner required for any other use.

The works necessary at each of these pumping stations in order to deliver the required flows and storage volumes are set out in Sections 7.4.2 to 7.4.9 below.

7.4.2 Connyborough Pumping Station

Connyborough Pumping Station is located on the Dublin Road to the east of the town. Whilst the storage capacity of the existing wet well is adequate to meet the requirements of Table 7.3 the plan area of the wet well and valve chamber is inadequate to allow the installation of new pumping plant and associated pipework. Table 7.2 sets out the required pumping capacity of the upgraded / new station.

Accordingly at Phase III flows Connyborough Pumping Station must be capable of pumping 64 l/s (6 DWF).

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It is proposed to install 3 No. 3 DWF pumps to operate on a Duty / Assist / Standby basis. The location of the new pumping station and associated site works is shown on Drawing No. 20290/15. A new Control Kiosk shall also be provided. The existing pumping station shall require to be maintained in operation until the new station is commissioned. Sufficient access and space is available on the existing site to allow the construction of the new station without interruption to the existing. Following completion of the new pumping station the old station shall be demolished.

It should be noted that the existing Connyborough Station may require to be relocated to a site further east should proposed industrial and residential development in this area proceed. This option is further discussed in Section 7.7.

7.4.3 Clonmullen Lane Pumping Station

The existing Clonmullen Lane Pumping Station as located on Drawing No. 20290/02 has inadequate pumping or storage capacity to deal with projected flows. The location of this pumping on the margin of the roadway is not suitable for the construction of an upgraded station.

A new pumping station has recently been constructed in the area as part of a housing For inspection purposes only. development. UltimatelyConsent the of copyrightexisting owner Clonmullenrequired for any other Lane use. Pumping Station shall be

abandoned and flows diverted to the new station. The new Clonmullen Lane Pumping Station shall ultimately require to have a pumping capacity of 11 l/s at 6 DWF and a storage capacity of 13 m3.

7.4.4 Carrick Road Pumping Station

The existing Carrick Road Pumping Station shall be upgraded in parallel with proposed residential and commercial developments in the area. Funding of the upgrade shall be provided entirely by the developers. The required pumping capacity and storage volumes shall be as per Tables 7.2 and 7.3 respectively.

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7.4.5 Derrycorris Pumping Station

The pumping station is located and the end of Fr. Murphy Street to the southeast of the town. Adequate storage capacity exists in the existing wet well to meet the recommended storage requirements of Table 7.3. Table 7.2 sets out the required pumping capacity of the upgraded station. Accordingly at Phase III flows Derrycorris Pumping Station must be capable of pumping 36 l/s at 6 DWF.

It is proposed to install 3 No. 3 DWF pumps to operate on a Duty / Assist / Standby basis. A new Control Kiosk shall also be provided.

7.4.6 Corkery Lane Pumping Station

This is a local pumping station which serves residential properties to the west of the town off the Rhode Road. Adequate storage capacity exists in the existing wet well to meet the recommended storage requirements as set out in Table 7.3. Table 7.2 sets out the required pumping capacity of the upgraded station. Accordingly at Phase III flows Corkery Lane Pumping Station must be capable of pumping 12 l/s at 6 DWF.

Due to the size of the station it is proposed to install 2 No. 3 DWF pumps to operate on a Duty / Assist basis. A new Control Kiosk shall also be provided. Due to the

location of the works on the road For inspection verge, purposes it is only. not proposed to carry out any additional Consent of copyright owner required for any other use. works at this site.

7.4.7 Killane Road Pumping Station

Killane Road Pumping Station serves a considerable amount of residential property to the south west of the town. It is located off the Tullamore Road adjacent to the Grand Canal. Significant amount of stormwater enters this station from the Killane Housing Estate during periods of wet weather.

Table 7.3 sets out the recommended storage capacity at each station. Accordingly 73 m3 must be provided at the upgraded station. As this is considerable in excess of the storage available in the existing wet well and due to the poor structural condition of

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the well, it is proposed that a completely new pumping station be constructed at Killane Road.

Table 7.2 sets out the required pumping capacity at the new station. Accordingly at Phase III flows the new Killane Road Pumping Station must be capable of pumping 36 l/s at 6 DWF.

As adequate space is available on the existing site it is proposed to construct the new pumping station adjacent to the existing station. 3 No. 3 DWF pumps to operate on a Duty / Assist / Standby basis shall be provided. A new Control Kiosk shall also be provided. The existing pumping station shall require to be maintained in operation until the new station is commissioned. The orientation of the new station and associated site works is shown on Drawing No. 20290/16. Following completion of the new pumping station the existing station shall be demolished.

7.4.8 Blundell Wood Pumping Station

This pumping station is located to the southwest of the Blundell Wood Estate close to the Grand Canal. Adequate storage capacity exists in the existing wet well to meet the requirements of Table 7.3.

For inspection purposes only. It is proposed to replace Consentthe existing of copyright ownerpumps required with for any 2 otherNo. use. 6 DWF pumps to operate on a

Duty / Standby basis delivering 6 l/s at 6 DWF. A new Control Kiosk shall also be provided. As this site and the station has fallen into a state of disrepair a considerable amount of remedial works shall also be required to provide a station that can be operated in a proper and safe manner.

7.4.9 Rising Mains

Table 7.4 below outlines the upgraded rising main diameters which shall be required following the increase of Pumping Capacities at each station. Existing diameters are adequate in all cases for Phase I loadings.

Nevertheless in order to minimise disruption within the town of Edenderry it is recommended that rising main diameters, where possible, be upgraded in parallel with

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works to the Pumping Stations and sewer upgrading as set out in Section 7.6 below. The only exceptions to this proposal relate to the Carrick Road and Derrycorris Rising Mains which cannot be upsized until the Phase II loadings are realised. Issues relating to pump flow rates to achieve self-cleansing velocities and residence time in the wet wells shall require consideration at pump selection and operation and maintenance phase of the works. Drawing No. 20290/18 indicates in plan the extent of the new rising mains proposed.

Table 7.4 – Rising Main Requirements Pumping Station Killane Derry- Conny- Clon- Corkery Carrick Blundell corris borough mullen Lane Road Existing Rising 100 100 100 100 50 100 80 Main (mm) Required Rising 150 150 200 100 100 275 80 Main (mm) Length (m) 755 587 501 - 908 806 -

7.5 Removal of Overflows

Section 3.7.4 of this report detailed the number and location of the storm overflows on the existing collection system all as shown on Drawing No. 20209/02. A total of 8

No. overflows were identifi ed For inspectionwhich purposes discharge only. to local watercourses in times of Consent of copyright owner required for any other use. increased flows. As recommended in Section 3 it is proposed to remove these overflows from the system due to the inadequacy of the accepting watercourses. Furthermore the discharge of unscreened or partially screened effluent during periods of high rainfall is no longer considered “best practice” from an environmental point of view.

The option of providing additional storage capacity at the overflows to limit the spill frequency was considered inappropriate for the following reasons:

ƒ Lack of adequate space at each of the existing overflow sites ƒ The necessity to upsize the main collector sewer as set out in Section 7.6 below ƒ Maintenance requirements at each site.

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As outlined in Section 7.4 above the upgraded pumping stations are designed with sufficient storage and pumping capacity to limit the spill frequency from emergency overflows.

7.6 Sewer Upgrading

The hydraulic model of the existing system was then re-analysed with the upgraded pumping station data and all storm overflows removed. The model was run with design storm return periods of 1 and 5 years to assess surcharging and flooding respectively. A peak flow of six times future Phase III dry weather flow was used in these design runs (pumping rates set to 6 times DWF).

Drawing No. 20290/17 presents the results of this analysis in terms of flooding and surcharged manholes.

The main areas of flooding as indicated on Drawing No. 20290/17 are summarised in terms of manhole numbers and flooding volumes in Table 7.5 below:

Table 7.5 – Summary of Flooding Data for Existing System and One Year Return Period Storm

Node Id Location Volume (m3) For inspection purposes only. Consent of copyright owner required for any other use. SN63326901 No. 14 Fr. Kearns Street 2,108 SN63326605 No. 46 Fr. Murphy Street 1,458 SN63326509 No. 56 Fr. Murphy Street 1,373 SN63326701 No. 37 Fr. Murphy Street 1,312 SN63326703 No. 37 Fr. Murphy Street 1,203 SN62327403 No. 92 St. Mary’s Street 1,031 SN63325803 No. 2 Fr. Murphy Street 1,009 SN63333001 Main collector behind O’Connell Square 591 SN63325501 No. 11 Greenwood Park 556 SN62327401 No. 918 St. Mary’s Street 370 SN63324801 Fairgreen nr. junction with Fr. Murphy Street 363 SN63325701 No. 1 Greenwood Park 305 SN63334004 No. 6 Colonel Perry Street 255 SN63325609 No. 66 Greenwood Park 163 SN62323702 No. 23 Rhode Road 58

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The main problem areas as a result of this analysis are as follows:

A. Fr. Murphy Street to Main Inlet Sewer (Relief Sewer)

The degree of surcharging of this sewer under existing conditions (see Section 3 and Drawing No. 20290/06) was exacerbated by the removal of the overflow in Greenwood Park and the addition of future development loadings along the length of the sewer.

It is proposed to construct a relief sewer parallel to the existing collector which will run from Fr. Murphy Street via Fr. Kearns Street, Colonel Perry Street, behind JKL Street and Rhode Road to connect with the main inlet sewer to the treatment works site. Drawing Nos. 20290/19 and 20290/20 indicate the proposed plan and longitudinal section of this sewer.

It is proposed to connect the following to the new collection sewer: ƒ Connyborough and Clonmullen Pumping Stations ƒ Existing collector sewer – a number of relief connections to be made. ƒ JKL sewer – connect directly to new sewer.

As indicated on the abovementioned For inspection drawpurposesings only. the new collector sewer will be 375 Consent of copyright owner required for any other use. mm is diameter for the first 294 metres of its run as far as Fr. Kearns Street / Colonel Perry Street, increasing to 450 mm for a distance of 518 metres as far as St. Conleth’s Road and a diameter of 525 mm for the final 411 metres as far as its connection with the existing sewer.

B. Foul Sewer on Rhode Road

Removal of the overflows between the foul and surface water sewers along the Rhode Road increases the degree of surcharging on the 225 mm foul sewer from existing and future loads.

Drawing Nos. 20290/21 and 20290/22 indicate in plan and longitudinal section the details of the proposed foul sewer. As shown it is recommended that 440 m of this

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sewer be upsized to 375 mm. In order to convey flows from Rhode Road to the main inlet sewer to the treatment works site it is proposed to augment the existing sewer by using the existing 450 mm surface water outfall which drains to the works. This is possible as a new 600 mm diameter surface water outfall is being constructed from Rhode Road to Weaver’s drain under a separate contract.

C. Sewer on St. Mary’s Street / JKL Street

In Section 3 of this report the degree of surcharging of this sewer was outlined as shown on Drawing No. 20290/07. Increased pump flows from Killane Road Pumping Station and increased flows from the Sycamores Housing Development and future development areas will exacerbate the problem.

It is proposed under a separate contract to construct a surface water sewer along a section of St. Mary’s Street. This in turn will remove some of the current surface water loading to the sewer. Nevertheless it is proposed to replace this sewer with a 375 mm diameter sewer along St. Mary’s Street from the connection with the rising main from Killane Road Pumping Station to the proposed connection to the existing 450 mm pipeline on Rhode Road as per Item B) above.

The overall length of sewer to For be inspection provided purposes along only. St. Mary’s Road / Rhode Road will Consent of copyright owner required for any other use. be approximately 950 m and is shown on plan and longitudinal section on Drawing Nos. 20290/21, 20290/23 and 20290/24. For ease of construction and to minimise traffic disruption in this area it is recommended that this section of foul sewer be constructed as part of the surface water scheme contract.

D) Sewer on St. Mary’s Street to Killane Road Pumping Station

Drawing No. 20290/06 indicates that the final sewer along St. Mary’s Street draining to the Killane Road Pumping Station is surcharged under existing loadings. Again the degree of surcharging increased under future loading conditions. The surcharging is largely due to the significant amount of stormwater entering the system from the Killane Housing Estate.

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It is proposed to replace this section of sewer with a 300 mm diameter sewer over a distance of 380 metres between the entrance to the Killane Estate and the Killane Road Pumping Station. The plan and longitudinal section of this proposed pipeline is shown on Drawing Nos. 20290/25.

Table 7.5 below presents the flood volumes after the hydraulic model has been re-run with the updated pumping station data upgraded sewer proposals and the stormwater overflows removed from the system. This table clearly indicates that flood volumes for 1 and 5 year events have been reduced to below the recommended thresholds which are: ƒ 25 m3 for combined / foul sewers ƒ 100 m3 for surface water sewers

Table 7.5 - Upgraded Model – Design Return Year Flooding (m³)

Node ID Location 1 Year 5 Year Comments

15 30 60 90 15 30 60 90 min min min min min min min min

SN62325650 No 17 Rhode 18.3 37.9 26 16.2 Surface Rd Water

SN62329702 Entrance to 7.4 10.9 8.8 4.8 Blundell Wood For inspection purposes only. Consent of copyright owner required for any other use. SN62322701 Rhode Rd west 8.9 9.4

SN63326605 No 46 Fr 1.5 2.1 1.9 1.3 5.2 6.4 7.3 6.4 Murphy St

SN62322602 Entrance to 5.6 5 Castleview Park

SN63325502 No 10 Green- 4.1 4.9 2.2 0.1 wood Park

SN61328101 Killane Heights 0.4 4.6 6.9 6.8

SN63326509 No 56 Fr 0 0.2 0.2 2.8 3.7 3.6 2.8 Murphy St

SN63324803 Fairgreen nr 2.9 3 0 junction with Fr Murphy St

SN63323901 No 38 JKL St 3.2 2.3

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7.7 Extensions to Existing Collection System

The proposed Land Use Zoning Map for Edenderry as set out in the Offaly County Council Development Plan 2003 is shown on Drawing No. 20290/08. Due to the topography of the catchment areas the majority of the future development areas will be served by one or more of the existing pumping stations. An exception to this will be elements of in-fill development which shall drain to existing gravity sewers in the town centre (JKL Street) or the proposed relief sewer as set out in Section 7.6.

Most of the land zoned for development to the north, south and west of the town will drain gravitationally or by means of localised pumping stations to the existing network. The exact location of where local branch pumping stations shall be developed cannot be determined until the layout and orientation of the proposed developments is established.

An exception to this is the lands zoned for development to the east of the town or the area between Connyborough and Kishawanny Bridge (Drawing No. 20290/08). Up to 12 ha. of the land is zoned for commercial in this area, 21 ha. for residential and 27 ha. for industrial. If development were to proceed in this area, particularly the industrial lands at Kishawanny Bridge a significant pumping station would be

For inspection purposes only. required in this location.Consent This of copyright pumping owner requiredstation for any would other use. pump all effluent back to the

existing Connyborough Pumping Station.

It is proposed to construct a new Pumping Station at Connyborough with increased pumping and storage capacities as outlined in Section 7.4.2. The option of relocating the new Connyborough Pumping Station from the site of the existing to a location in the vicinity of Kishawanny Bridge has been examined. The benefit of this approach is that a new station at Kishawanny could be sized to cater for the ultimate flow in the general sub-catchment (ie. future Connyborough flows and flows from industrial lands). Based on economies of scale this would lead to a value for money solution for Offaly County Council. Furthermore it would require pumping of effluent once only from the sub-catchment (ie. from the new Kishawanny Pumping Station to the existing gravity network).

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It is proposed to lay a new sewer from the gravity inlet to the existing Connyborough Pumping Station in an easterly direction all as shown on Plan and Longitudinal Section on Drawing No. 20290/27. The route of this pipeline would follow generally the route of the abandoned railway line. A new pumping station shall require to be constructed at Kishawanny Bridge. The exact location of this pumping station would required to be confirmed following consultation with the developers and/or Planning Officials in Offaly County Council.

7.8 Sewer Repair and Rehabilitation Works

The results of the CCTV and SUS 2000 survey, carried out between June to October 2003 are presented in Section 3.4 of this report. These surveys examined in detail the structural integrity and hydraulic capacity of all existing manholes and pipelines which form part of the Edenderry Wastewater Collection System.

As set out in Section 3.4, 44% of the entire collection network needs rehabilitation. The majority of the rehabilitation works (91%) relate to critical defects (ie. in the Grade 4-5 range). The types of repair techniques required shall include relining of pipes, sealing of laterals, localised repair and the removal of intrusions. In a number of cases it may be necessary to re-lay sections of pipelines if rehabilitation measures

For inspection purposes only. are considered inadequate.Consent of copyright owner required for any other use.

In terms of manholes 69% of manholes surveyed shall require rehabilitation. Generally the works shall involve the replacement of damaged or defective covers, relining of manholes to reduce infiltration and the repair of benching.

The estimated costs of these repair and rehabilitation works are included in Section 11.

7.9 Storm Handling Facilities at Wastewater Treatment Works

Section 7.3 outlined the proposed methodology for handling existing and projected storm flows in the generally combined existing system. Stormwater separation

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infrastructure is to be provided within the catchment where appropriate. Storm sewers discharging to suitable watercourses are to be provided where appropriate for all new developments. However for the majority of the network all flows are to be delivered to the upgraded wastewater treatment works. Thus storm flows can be handled and treated at a central location and discharged to the River Boyne in an environmentally sensitive manner.

Currently at the Wastewater Treatment Works an overflow exists at the inlet where flows in excess of 3 DWF (current) discharge into a rectangular stormwater holding tank. The volume of the existing stormwater holding tank is 400 m3. Excess storm flows overflow from this tank via a 6 mm storm overflow screen into a 600 mm diameter outfall sewer to the River Boyne. This outfall pipeline is sized to handle 4 DWF (Phase III) equating to approximately 280 l/s.

A hydraulic model of the proposed collection system was run following upgrading of the sewers, pumping stations and removal of overflows to determine the amount of storm flows which would be delivered to the Wastewater Treatment Works under a series of rainfall events. Following this simulation the analysis of the stormwater storage regime at the Wastewater Treatment Works was carried out in two stages as follows:

For inspection purposes only. Consent of copyright owner required for any other use. i) storage required to limit the number of overflow spills to the River Boyne. For this analysis an allowable spill frequency of once in one year was assumed with a 1 year return period. The storage was estimated for the three phases of development.

ii) following inputting of the required storage set out at i) above into the model an analysis was carried out to determine if additional storage is required to limit surcharging and possible flooding due to capacity issues with the outfall sewer from design storms of high return period. Again the storage was estimated for the three phases of development.

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Table 7.8 below presents the overall volumes of stormwater required at the Wastewater Treatment Works in order to limit the number of spills to one per year for a storm of a 1 year return period.

Table 7.8 – Overall Stormwater Storage Required for One Year Spill Frequency

Duration Phase III Phase II Phase I (mins) (m3) (m3) (m3) 60 697 653 650 90 669 695 690 120 734 770 767 240 611 720 785 Max. 734 770 785

As outlined in Table 7.8 a maximum storage volume of 800 m3 is necessary. This is an increase of approximately 400 m3 required at the works.

Tables 7.9 and 7.10 below shows the additional storage volume required (in excess of the 800m3 calculated above) to limit the degree of surcharging in the outfall pipe for 5 year and 10 year rainfall events.

For inspection purposes only. Table 7.9 - 5 Year AdditionalConsent Storage of copyright ownerat WWTW required for any other use.

Duration Phase 3 Phase 2 Phase 1 (mins) (m3) (m3) (m3) 60 143 8 0 90 149 29 3 120 207 69 24 240 106 39 5 Max. 207 69 24

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Table 7.10 - 10 Year Additional Storage at WWTW

Duration Phase 3 Phase 2 Phase 1 (mins) (m3) (m3) (m3) 60 271 149 36 90 308 140 80 120 396 190 137 240 292 176 104 Max. 396 190 137

Table 7.10 indicates that an additional 200 m3 will be required at the WWTW (in excess of the 800 m3 calculated above) under the Phase II loading at a 1 in 10 year return period. An additional 400 m3 will be required at the WWTW (in excess of the 800 m3 calculated above under the Phase III loading at a 1 in 10 year return period.

Table 7.11 below outlines the stormwater storage requirements at the WWTW for the projected loadings at a 1 in 10 year return period.

Table 7.11 - 10 Year Additional Storage at WWTW Phase Existing Storage Required Storage Increase (m3) (m3) (m3)

Phase I 400 1,000 600

For inspection purposes only. Phase II Consent of 400copyright owner required for any other 1,000 use. 600

Phase III 400 1,200 800

Thus it is proposed that 600 m3 additional storage capacity be provided at the works under Phase I which shall satisfy both the Phase I and Phase II conditions. A further 200 m3 shall be required at Phase III.

Provision for this increased storage, which shall limit the number of spills to the River Boyne to once in one year, has been included in the outline design and layouts for the expanded works as set out in Section 6 of this report.

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7.10 Summary of Proposed Measures

The hydraulic analysis of the Edenderry sewerage network demonstrated that there were a number of weaknesses in the existing system, as follows;

1. There are capacity problems at most of the pumping stations in dealing with storm flows, 2. There is a significant volume of storm flow entering the foul network, 3. Many of the existing town sewers have capacity problems, 4. As a result of the above, there are frequent spills from the town’s overflows into adjacent watercourse, very few of which have the assimilative capacity to deal with such spillages.

The problems mentioned above occur under existing loading conditions. The addition of future development areas which could see the existing Population Equivalent of 7,458 persons rise to 29,500 persons by 2028 (design horizon) will clearly worsen the existing situation.

In order to alleviate current problems and also to provide a network which will serve Edenderry for the next 25 years, the following measures are proposed. It is

For inspection purposes only. recommended that theseConsent works of copyright proceed owner required as for anysoon other use.as possible to allow proper

development of the town and reduce flooding and untreated discharges from overflows.

1. Upgrade or re-build all of the peripheral pumping stations, so that each will be capable of pumping forward a flow equivalent to 6 times the upstream dry weather flow, while providing sufficient storage to limit the number of overflow spills to adjoining watercourses.

2. Relocate existing Connyborough Pumping Station to Kishawanny Bridge if industrial development in this area proceeds. This shall involve the construction of:

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A) New Pumping Station

B) 641 m of Gravity Sewer

C) 1,110 m of Rising Main

It should be noted that this option should only proceed if significant development works proceed in lands zoned as industrial at Kishawanny.

3. Remove all of the town’s existing Combined Storm Overflows.

4. Construct a number of relief sewers in the town, as follows;

A. New collector sewer from Fr Murphy St to the outfall 294 metres of 375mm diameter sewer 518 metres of 450mm diameter sewer 411 metres of 525mm diameter sewer

B. New sewer along Rhode Road 440 metres of 375 mm diameter sewer

For inspection purposes only. Consent of copyright owner required for any other use. C. New sewer along St. Mary’s Street, JKL Street, as far as Rhode Road 950 metres of 375 mm diameter sewer

D. New sewer along St. Mary’s Street to the south to Killane Pumping Station 380 metres of 300 mm diameter sewer

5. Construct a series of new rising mains from pumping stations as follows:

A) 755 m of 150 mm diameter rising main from Killane Road Pumping Station

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B) 587 m of 150 mm diameter rising main from Derrycorris Pumping Station

C) 501 m of 200 mm diameter rising main from Connyborough Pumping Station

D) 908 m of 100 mm diameter rising main from Corkery Lane Pumping Station

6. Provide an additional 600 m3 of storage at the WWTW, under Phase I and II, in order to limit the number of spills to the River Boyne to once per annum for an event 1 in 10 year.

7. Ultimately provide a further additional 200 m3 of storage at the WWTW under Phase III, in order to limit the flows to the existing outfall sewer during a 1 in 10 year event. The overall capacities storage to be provided can be phased as follows;

Phase Year Storage Phase I 2007 1,000 m3 3 Phase II 2015For inspection purposes only.1,000 m Consent of copyright owner required for any other use. Phase III 2028 1,200 m3

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8. DESIGN PARAMETERS AND LAYOUT OF WASTEWATER TREATMENT PLANT

8.1 Summary of Design Parameters

The basic design parameters for the wastewater treatment plant can be summarised as follows:

Phase I Phase II Phase III Population Equivalent 14500 22000 29500 Wastewater Flow l/h/d 225 225 225 DWF m3/day 3262.5 m3/d 4950 m3/d 6637.5 m3/d l/sec 37.76 l/sec 57.29 l/sec 76.82 l/sec Max. Flow to Full Treatment 9787.5 m3/d 14850 m3/d 19912.5 m3/d (3 DWF) 113.28 l/sec 171.87 l/sec 230.47l/sec Storm Tank Volume Required 816 m3 1237.5 m3 1660 m3 (3 DWF for 2 Hours) Storm Tank Volume required 1,000 1,000 m3 1,200 m3 (based on Network Model Storm Tank Volume Provided 1,300 m3 1,300 m3 1,700 m3 Retention Time 3.2 hrs. at peak 2.1 hrs. at peak 2 hrs. at peak flow flow flow For inspection purposes only. Consent of copyright owner required for any other use.

8.2 Preliminary Layout of the Wastewater Treatment Works

Section 6 of this Preliminary Report set out the various process options which were examined to cater for the requirements of an expanded Wastewater Treatment Works. Indicative layout drawings and elevation details for each option are shown on Drawing Nos. 20290/09 to 20290/14. These indicative arrangements are also used in the Environmental Impact Statement for the expanded Wastewater Treatment Works.

Phosphate dosing facilities will be provided similar to those already provided for the existing plant. New sludge holding and dewatering facilities will be provided from the Phase II point onwards.

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As a minimum the 3 options for expansion of the works shall have the following common units:

- New Inlet Works shall be provided at the Phase I expansion which shall be sized to cater for the ultimate (Phase III) flows. - New Stormwater Holding Tanks shall be provided at Phase I to cater for the Phase I and Phase II flows. - Phosphate Dosing Facilities. - Increased Sludge Holding Facilities (15,000 p.e.) will be provided at the Phase II expansion.

Other facilities to be provided under Phase I include the following: (1) Administration building (2) Air Blower Building (3) Site roads and fencing (4) Process and drainage pipework (6) Tertiary Treatment (7) Telemetry and Scada control system (8) Landscaping

8.3 Stormwater Tanks For inspection purposes only. Consent of copyright owner required for any other use.

A minimum retention time of 2 hours will be provided for peak flows. Weir mounted storm overflow screens will be installed in the main inlet works overflow channel (6 mm screens) to ensure that solids will be retained in the main flow to treatment Stormwater flows will be retained and pumped back to the main incoming flow to receive full treatment when the main flow to treatment drops to 1.5 DWF. The overflow from the tank will discharge to the River Boyne. An analysis of the existing outfall shows sufficient capacity to transfer the storm flows from the tank at peak flows.

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9. SEPTICITY AND ODOUR CONTROL

9.1 General

It is important to reduce, if not, eliminate septicity of sewage within the various components of the sewage collection and treatment facilities.

The causes of septicity are generally anaerobic decomposition of sewage which releases obnoxious gases and creates odour problem in the process of sewage collection, treatment and disposal. Also the release of corrosive gases and certain types of bacteria causes corrosion to pipes and other appurtenances.

Also malodorous conditions can prevail due to release of gases from undigested sludge and release of methane during the process of settlement in sedimentation tank and in sludge digestion.

As the septicity increases due to increase in temperature, septic conditions could be experienced during the summer months if the causes of septicity are not eliminated from the system at the design stage.

9.2 Physical Conditions for Septicity For inspection purposes only. Consent of copyright owner required for any other use.

The physical characteristics that lead to septicity and odour can be expected under the following conditions:

(a) Sewerage System

(i) The septic conditions are caused by settlement of solids in the sewer due to low velocities in sewers at low flow conditions and overall oxygen depletion.

(ii) High retention time in sewage pumping stations and in the rising mains.

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(b) Sewage Treatment Plant

(i) Inadequate de-sludging facilities causing high sludge retention time in the Final Sedimentation Tanks.

(ii) High B.O.D. loading in Aeration Tanks and low Oxygen transfer causing depletion of dissolved oxygen.

(iv) Leakage or release of gases from covered sludge holding tanks and handling facilities.

(v) Removal of organic material in grit removal systems.

(vi) Inadequate facilities for cleaning, washing, handling and storage of screenings.

(vii) Inadequate facilities for cleaning stormwater/ detention tanks.

(c) Final Effluent Outfall

(i) Inadequate Treatment For inspection of purposes sewage, only. high retention time and high upward Consent of copyright owner required for any other use. velocity in Final Tanks causing sludge lift and solids in the Final Effluent.

The above problems are overcome by the following:

(A) Appropriate design in respect of flow, velocity, and loading. (B) Adequate control and sequencing of commissioning of the sewerage system and sludge handling facilities. (C) Avoiding Hydraulic and Biological Overloading of Biological Tanks. (D) Provision of appropriate equipment and procedures for cleaning and maintaining screenings handling facilities and effluent channels.

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9.3 Preventive Measures

Common causes and preventive measures for septicity and odour control to be adapted during detailed design of the scheme shall be:

(a) Sewerage System

(i) Avoidance of low velocity and depth of liquid in a sewer at initial stage flow of a scheme. The individual sewers when designed for ultimate flow condition, which is considerably higher than the initial flow condition, shall have adequate slope to have self cleansing velocity (minimum 0.75 m/sec) at the daily peak flow rate of the initial flow condition. The depth of liquid in a sewer pipe should not be less than 50 mm at any flow condition at DWF.

(ii) Avoidance of long retention times in the pump sumps and the rising main at initial stage flow of the scheme The retention time in the pump wet sump shall be kept to a minimum and shall allow a minimum capacity required to avoid high frequency

For inspection purposes only. (less thanConsent 10 ofper copyright hour) owner of required start for anyand other stop use. of the duty pump. If the

retention time is more than an hour at the initial stage flow when the wet sump is designed in consideration of ultimate stage flow, consideration should be given to the duplication of the sump at ultimate stage rather than a large sump which would operate at the initial stage.

(b) Inappropriate sequencing and control at the commissioning stage of a scheme shall be avoided.

(c) Any leakage in the sludge handling system shall be thoroughly investigated and remedial measures shall be undertaken promptly. Any hazards due to the combustible nature of sludge gas should be avoided. In this respect the

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housing of the sludge handling system must be provided with a de-odouriser combined with forced ventilation. Also gas detection equipment shall be located at strategic points in the sludge handling building.

9.4 Recommendations

In order to minimise the common causes for septic conditions and associated odour problems, the preliminary design of the Sewerage System and Treatment Plant takes account of the basic requirement as detailed above.

In relation to minimising odours at the proposed site of the Treatment Plant the following measures are proposed:

(i) Enclosed bagging units to be installed for collection of the dewatered screenings (ii) A Grit Classifier, complete with covered skip to be provided to ensure that organic material is returned to the main inflow to Treatment (iii) Tipping Buckets complete with automatic control for regular cleaning of the stormwater detention tanks after they are emptied (iv) High pressure water cleaning system for regular cleaning of influent and

For inspection purposes only. effluent channelsConsent of copyright owner required for any other use.

(v) Odour control to be provided for any sludge handling, storage and dewatering facilities (vi) A covered area, complete with odour scrubbing to be provided for the inlet works.

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10. STORMWATER NETWORK

10.1 General

The existing collection system in Edenderry as set out in Section 3 is essentially a combined system with a series of Combined Storm Overflows discharging to local streams and ditches. A number of dedicated surface water pipelines currently exist which drain to local watercourses and channels. Ultimately all watercourse, channels and ditches drain to the River Boyne. As two separate and stand alone reports have already been prepared on the surface water system in Edenderry and its impact on the River Boyne1,2 it is not proposed to deal substantially with Stormwater Network Proposals in this Preliminary Report.

10.2 “Assessment of Surface Water Drainage in Edenderry”

This report completed in May 2001 examined the existing surface water drainage system in Edenderry and made recommendations for improvements to same. A surface water drainage scheme based on the recommendations contained therein has since proceeded to tender, and works are expected to commence in the near future. In summary the works involve the laying of surface water pipelines along a section of For inspection purposes only. JKL Street, St. Mary’s ConsentStreet, of copyrightthe Tullamore owner required forRoad any other and use. the Rhode Road. Collected

stormwater is diverted to an open-water channel, Weaver’s Drain, which drains to the River Boyne. Clearing and re-grading of Weaver’s Drain and a series of additional open-water drainage channels are also included with the scope of works.

In this report (Section 7) the options for further separation of stormwater from the existing combined network were examined. It was considered unfeasible for a number of reasons to further construct a separate system and it was recommended that all remaining stormwater volumes be forwarded within the existing or improved combined system for treatment and disposal out the Wastewater Treatment Works.

1 “Assessment of Surface Water Drainage in Edenderry” - Nicholas O’Dwyer Ltd., May 2001. 2 “Upper Boyne Flood Study ” ( Draft ) - Nicholas O’Dwyer Ltd., December 2004.

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10.3 “Upper Boyne Flood Study”

A hydraulic model of the River Boyne in the vicinity of Edenderry was constructed as part of this study to examine how the river responded to various rainfall events combined with existing and future surface water loadings. As the River Boyne has a history of flooding on low-lying areas adjacent to the river and to the north of the town the study was necessary to best define the lands which are vulnerable. General recommendations were made as to the extent of development which could proceed in the flood plain and damaged areas without exacerbating the existing and predicted flooding in these areas.

10.4 Future Development

As indicated on Drawing No. 20290/08 a considerable amount of land is zoned for development within the Edenderry Urban Boundary. It is recommended that all future developments have separate foul and surface water drainage systems.

The Institute of Hydrology Report No. 124 outlines a method of estimating permissible outflow of stormwater from future development based on soil characteristics and rainfall events. This report also recommends the volume of on-site For inspection purposes only. storage required when thisConsent perm of copyrightissible owner flow required is forexceeded. any other use.

Tables 10.1 and 10.2 present general permissible run-off rates and storage volumes necessary based on various soil types as set out in the Institute of Hydrology Report. As a guide a soil index figure of 0.3 to 0.4 should be used for Edenderry. Whilst these tables present recommended parameters, the Institute of Hydrology Report No. 124 estimation equations should be used on a case by case basis due to the variability of soil type, impervious areas and rainfall.

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Table 10.1 - Mean Annual Maximum Flood Flows using IH No. 124 Flood Equation Soil Class 1 2 3 4 5 Soil Index 0.15 0.3 0.4 0.45 0.5 Area (ha) Run-off Rate l/s per ha 5 0.79 3.56 6.65 8.59 10.80 10 0.73 3.30 6.16 7.96 10.00 25 0.66 2.99 5.57 7.20 9.05 50 0.61 2.77 5.16 6.67 8.38 100 0.57 2.56 4.79 6.18 7.77 500 0.48 2.15 4.01 5.18 6.51 1000 0.44 1.99 3.71 4.80 6.03

Table 10.2 - Storage Volume Calculations (50 Year Storm Event) Soil Class 1 2 3 4 5 Soil Index 0.15 0.3 0.4 0.45 0.5 Site Area (ha) Required Storage Volume m3 5 1573 1110 830 740 550 10 4630 2300 1720 1530 1130 25 7990 6030 4510 4000 3600 Storm duration 170 20 7.5 5 3 (hrs) Duration to 351 39 16 11 6 empty (hrs) SAAR = 1000 mm, M5-1hr = 15.6 mm, M5-2day = 55.5 mm Percentage Impervious Area 50% For inspection purposes only. Permissible Outflow set toConsent esti matedof copyright Mean owner requiredAnnual for Maximumany other use. Flow

It is recommended that this report be used for the basis of determining and designing future stormwater drainage systems for all new developments. The design of such systems should also take cognisance of the findings of the Upper Boyne Flood Study Report particularly in terms of damaged (flooded) areas.

Where stormwater storage is required on site it is recommended that the option of using Sustainable Urban Drainage Systems (SUDS) techniques be examined. A description of SUDS is outlined in Section 10.5 below.

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10.5 SUDS – Sustainable Urban Drainage Systems

The following description of SUDS is compiled from selected extracts from the ‘Sustainable Urban Drainage Systems, design manual for Scotland and Northern Ireland’.

10.5.1 General Description

For new developments a solution for the drainage of surface water without causing flooding or pollution and without causing the sterilising of valuable land is required. Conventional drainage techniques can cause flooding and pollution and disrupt the water cycle to the detriment of water resources and the natural environment.

With SUDS the natural runoff from a site is mimicked. The quantity and quality of the runoff and the amenity value of the surface water in the urban environment are all taken into account. SUDS are made up of one or more structures built to manage surface water runoff, which are to be arranged in conjunction with good organization of the site to prevent pollution.

There are three preferable methods of control:

‰ filter strips and swales For inspection purposes only. Consent of copyright owner required for any other use.

‰ filter drains and permeable surfaces

‰ infiltration devices

Controls should be located as close as possible to where rainfall falls, providing attenuation for runoff. The controls also provide varying degrees of treatment for surface water using the natural processes of sedimentation, filtration, absorption and biological degradation.

SUDS do not operate as a series of isolated drainage devices, but should be devised and operated holistically.

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Filter Strips and Swales Filter strips and swales are vegetated surface features that drain water evenly off impermeable areas. Swales are long narrow channels whereas filter strips are gently sloping areas of ground.

Filter Drains and Permeable Surfaces

Filter drains and permeable surfaces are devices that have a volume of material below the ground to store surface water. Runoff flows to this storage area via a permeable surface. Filter drains are linear devices that drain off the impermeable area in a diffuse manner. Permeable surfaces act by directly intercepting the rain where it falls. They are currently in use in car parks, residential driveways, paths and patios.

Infiltration Devices

Infiltration devices drain water directly into the ground. They may be used at the source or they can be conveyed in a pipe or swale to the infiltration area. They include soakaways, infiltrations trenches and infiltration basins as well as swales, filter drains and ponds. Infiltration devices can be integrated into and form part of the landscaped area.

For inspection purposes only. Consent of copyright owner required for any other use.

10.5.2 Initial Data Required

Information relating to proposed developments will need to establish the following: ƒ Original Drainage Pattern ƒ Catchment Topography ƒ Local Rainfall and Runoff ƒ Locations of Discharges ƒ Ground Conditions ƒ The Proposed Development ƒ Existing Wildlife Habitats, Landscape Features and Community Uses

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10.5.3 Design Strategy for Drainage System

Once data has been collected drainage techniques can be selected. There will be a number of potential solutions especially when all the different combinations are taken into account. The drainage system should be influenced by the original drainage pattern.

Best Practices listed for designing sustainable urban drainage are as follows:

Preventative Measures

• Minimise Runoff, Increase the proportion of impervious area, gravelled surfaces can replace tarmac in parking areas and on domestic driveways

Recycle runoff in the development site

• Minimise directly connected areas Hard paving and roofed areas can be drained onto unpaved areas

Driveways and footpaths can be drained onto surrounding lawns

Good Housekeeping

• Education,

For inspection purposes only. Informing users Consentof the of copyright site ownerabout required the for wayany other the use. site is drained can prevent

contaminants from entering the drainage system.

Pollutants that need to be controlled are car oil and antifreeze, detergents from car washing, household chemicals and garden chemicals

• Road Sweeping, Many contaminants can be removed by regular sweeping before they are washed into the drainage system

• Wrong Connections, Connecting foul sewers to the surface water system can cause pollution. The use of swales and permeable surfaces can limit these misconnections by replacing underground drains

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• Roads, Good practice during cleaning, winter maintenance and general maintenance

Permeable Surfaces

• Surface Material, The type of surfacing material should be selected to suit the location and use of the area

Types of surfacing include:

Grass

Reinforced grass

Gravelled areas

Solid paving blocks with large vertical holes filled with soil or gravel

Solid paving blocks with gaps between the individual units

Porous paving blocks with a system of voids within the unit

Continuous surfaces with an inherent system of voids

• Sub-base, The sub-base material is where the run-off is stored. The nature and depth of the sub-base is dependent on the nature and use of the pavement. The sub-base For inspection purposes only. can be constructedConsent from of copyright materials owner required such for as: any other use.

Local subsoil (if suitable)

Sands and gravels

Layers of imported crushed stone

Suitable recycled aggregate

10.5.4 SUDS Conclusions

The Land Use Zoning Map contained in the Edenderry Town Development Plan (2003) indicates that a total of 370 ha of land has been zoned for future development. From both an environmental and flooding point of view, the possibility of using Sustainable Urban Drainage Systems (SUDS) techniques within new developments

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should be investigated. SUDS techniques which, represent source control, would greatly reduce the volume and rate of runoff to the sewer system within the development area. The volume of storage required would also be reduced. The controls, which make up the SUDS techniques, treat the surface water through natural methods of sedimentation, filtration, absorption and biological degradation. Unlike conventional drainage techniques the quality of the runoff is therefore taken into account. It would therefore be advisable to apply SUDS techniques within new development areas in Edenderry.

For inspection purposes only. Consent of copyright owner required for any other use.

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11. COST ESTIMATES

11.1 Preparation of Cost Estimates

The cost estimates for the Scheme are prepared under three categories, namely:

(a) Wastewater Treatment Works Expansion (Phase I, II and III) (b) Improvements to Existing Wastewater Collection Network (c) Proposed Wastewater Collection Network

The estimates are based on extensions to quotations received from suppliers and on recent Contract prices for similar work.

11.2 Wastewater Treatment Works Expansion

11.2.1 Estimated Cost of Phase I

The estimated cost for Phase I of the wastewater treatment plant is summarised below:

Wastewater Treatment Works (excl VAT) €4,548,720

For inspection purposes only. Consent of copyright owner required for any other use.

A breakdown of these costs is given in Table 11.1

11.2.2 Estimated Cost of Phase II

The estimated cost for Phase II of the Scheme is summarised below:

Wastewater Treatment Works (excl VAT) €1,953,600.00

A breakdown of these costs is given in Tables 11.2.

11.2.3 Estimated Cost of Phase III

The estimated cost for Phase III of the Scheme is summarised below:

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Wastewater Treatment Works (excl VAT) €1,491,600.00

A breakdown of these costs is given in Tables 11.3.

11.2.4 Summary of Estimated Wastewater Treatment Works Costs

The Wastewater Treatment Works Expansion Costs (excluding VAT) are detailed below:

Phase I €4,548,720.00 Phase II €1,953,600.00 Phase III €1,491,000.00 €7,993,320.00 Site Investigation Contract €15,000.00 Detailed Ground Profile Survey €6,000.00 Flow and Load Survey €20,000.00 Consultants Fees €428,205.00 Resident Engineer €125,000.00 Total Estimated Scheme Cost €8,587,525.00

For inspection purposes only. All construction and ancillaryConsent of copyright costs owner shall required be for anysubject other use. to a VAT rate of 13.5%.

Consultants Fees are subject to a VAT rate of 21%.

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11.3 Annual Operation and Maintenance Costs The estimated operational and maintenance costs per annum of the Phase I plant ( 14,500 p.e ) is outline below.

Costs for Operation and Maintenance of the Phase 1 WWTW per Annum

FIXED Labour: 1/2 manager, 2 operators, 1/2 technician, 1/4 chemist €130,000.00 Insurance / overheads €97,500.00 Capital replacement €10,000.00 Scheduled maintenance materials €10,000.00 Laboratory costs €13,032.00 Transport €10,000.00

VARIABLE Electricity costs €45,000.00 Materials/consumables costs €16,875.00 Chemicals €45,000.00 Sludge treatment and transport €82,125.00

Total Cost per Annum €459,532.00

11.4 Improvements to Existing Wastewater Collection Network

For inspection purposes only. Consent of copyright owner required for any other use.

Improvement works to the existing collection system shall generally involve the Rehabilitation of the network following the CCTV and SUS 2000 survey results, the construction of relief sewers, the upgrading of existing sewers and rising mains, the upgrading of pumping stations, the removal of pumping stations and the removal of combined storm overflows.

11.4.1 Estimated Cost of Sewer and Manhole Rehabilitation

The estimated costs of the rehabilitation to the existing network is €793,191.00 excluding VAT.

A breakdown of these costs is given in Tables 11.4 and 11.5.

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The total estimated costs of these works including preliminary and general items is €1,094,604.00.

11.4.2 Estimated Cost of New and Upgraded Sewers

A) St. Mary’s Road Sewer “D Line” Quantity € Sewers 383 m 18,572.00 Manholes 8 nr. 8,910.00 Ancillaries & Reinstatement 66,352.00 €93,834.00

B) Relief Sewer “R Line” Quantity € Sewers 1223 m 139,892.00 Manholes 19 nr. 20,350.00 Ancillaries & Reinstatement 114,782.00 €275,024.00

C) Foul Sewer on Rhode Road – “A Line (part)” Quantity € For inspection purposes only. Consent of copyright owner required for any other use. Sewers 436 m 33,572.00 Manholes 12 nr. 9,900.00 Ancillaries & Reinstatement 211,706.00 €255,178.00

D) Foul Sewer on JKL Street, St. Mary’s Road and Rhode Road “A Line (part)” Quantity € Sewers 1399 m 58,965.00 Manholes 19 nr. 19,800.00 Ancillaries & Reinstatement 679,304.00 €758,069.00

Note: Works involved at Item (D) shall be constructed as part of the Edenderry Surface Water Scheme)

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E) Summary Costs of New Pipelines € D Line 93,834.00 R Line 275,024.00 A Line (part) 255,178.00 A Line (part) 758,069.00 €1,382,105.00 Add Preliminary Items @ 15% 207,316.00 €1,589,421.00 Add Contingency / Provisional Sums 317,884.00 Total €1,907,305.00

11.4.3 Estimated Cost of New Rising Mains

Quantity € A) Killane Road Rising Main (150 mm) 755 m 99,660.00 B) Derrycorris Rising Main (150 mm) 587 m 77,484.00 C) Connyborough Rising Main (200 mm) 501 m 71,643.00 D) Corkery Lane (100 mm) 908 m 109,868.00 €358,655.00

For inspection purposes only. Add Preliminary ItemsConsent @ 15% of copyright owner required for any other use. 53,798.00

€412,453.00 Add Contingency / Provisional Sums 82,490.00 Total €494,943.00

11.4.4 Estimated Cost of New / Upgraded Pumping Stations

A) Connyborough Pumping Station € Civil Works Cost & Site Works 123,200.00 Pumping Plant 84,187.00 Electrics & Controls 34,096.00 €241,483.00

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B) Derrycorris Pumping Station € Civil Works (Upgrading) 30,000.00 Pumping Plant 47,354.00 Electrics & Controls 17,925.00 €95,279.00

C) Corkery Lane Pumping Station € Civil Works (Upgrading) 18,000.00 Pumping Plant 16,500.00 Electrics & Controls 6,392.00 €40,892.00

D) Killane Road Pumping Station € Civil Works Cost & Site Works 88,500.00 Pumping Plant 47,354.00 Electrics & Controls 17,925 €153,779.00 For inspection purposes only. Consent of copyright owner required for any other use.

E) Blundell Wood Pumping Station € Civil Works (Upgrading) 40,000.00 Pumping Plant 15,400.00 Electrics & Controls 11,000.00 €66,400.00

F) Clonmullen Lane (Provisional) €50,000.00

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G) Summary of Costs of New / Upgraded Pumping Stations € Connyborough Pumping Station 241,483.00 Derrycorris Pumping Station 95,279.00 Corkery Lane Pumping Station 40,892.00 Killane Road Pumping Station 153,779.00 Blundell Wood Pumping Station 66,400.00 Clonmullen Lane 50,000.00 €647,833.00 Add Preliminary Items @ 15% 97,175.00 €745,008.00 Add Contingency / Provisional Sums 149,002.00 Total €894,010.00

11.4.5 Estimated Costs of Removing Combined Storm Overflows The estimated cost (excluding VAT) of removing 8 No. Combined Sewer Overflows from the system is €27,500.00 including Preliminary Items, Contingency, etc.

11.4.6 Summary of Estimated Wastewater Collection Network Costs

The estimated cost to upgrade the existing network (excluding VAT) are detailed

For inspection purposes only. below: Consent of copyright owner required for any other use.

€ New and Upgraded Sewers 1,907,305.00 Rising Mains 494,943.00 Pumping Stations 894,010.00 Sewer and Manhole Rehabilitation 1,094,604.00 Combined Sewer Overflows removal 27,500.00 €4,418,362.00 Site Investigation Contract 110,000.00 Topographical / Site Surveys 30,000.00 Consultant’s Fees 261,461.00 Resident Engineer 150,000.00 Total Estimated Cost €4,969,823.00

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11.4 Proposed Extensions to Wastewater Collection Network

Section 7.7 outlined the potential for relocating the Connyborough Pumping Station should development of lands zoned at Kishawanny proceed.

The estimated costs (excluding VAT) if such works were to proceed are as follows:

A) Connyborough Sewer Extension Quantity € Sewers 641 m 37,593.00 Rising Main 641 m 19,872.00 Manholes 9 No. 18,700.00 Ancillaries & Reinstatement 69,861.00 Additional Pumping Station * 37,500.00 €183,526.00 Add Preliminary Items @ 15% 27,529.00 €211,055.00 Add Contingency @ 20% 42,211.00 Total €253,266.00

For inspection purposes only. * Note: This additionalConsent ofcost copyright relates owner to requiredthe increased for any other costs use. (Civil Works) over that set out in

11.3.4 for the Connyborough Pumping Station. These costs would be realised through have to provide a deeper wet sump at any relocated station.

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11.5.1 Overall Summary Costs of Edenderry Sewerage Improvement Scheme

The overall summary estimated costs of the total works proposed under the Edenderry Sewerage Improvement Scheme are as follows. Phasing of the expansion of the wastewater treatment works is discussed in detail in this report. With regard to phasing of the works to the collection network the entire works should proceed at this stage with the exception of the upsizing of Carrick Road and Derrycorris rising mains all as set out in Section 7. The extension of the Connyborough collection system to serve the Kishawanny area should only proceed development if the area commences.

Overall Summary Costs Cost (€)

Wastewater Treatment Works Phase I 4,548,720.00 Phase II 1,953,600.00 Phase III 1,491,000.00 Wastewater Collection Network 4,418,362.00 Wastewater Collection Network Extension 253,266.00 12,664,948.00

For inspection purposes only. Consent of copyright owner required for any other use.

Site Investigation Contract 125,000.00 Topographical Survey/Site Surveys 56,000.00 Consultants Fees 689,666.00 Resident Engineer 275,000.00

Total Estimated Cost (Excluding VAT) €13,810,614.00

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Phase I Cost Construction WWTW €4,548,720.00 Network €4,340,878.00 €8,889,598.00 VAT at 13.5% €1,200,095.73 Construction Total €10,089,693.73

Project Preliminaries Site Investigation €87,500.00 Topographical Surveys €39,200.00 €126,700.00 VAT at 13.5% €17,104.50 Preliminarys Total €143,804.50

Project Supervision Consultants Fees €482,766.00 Resident Engineer €192,500.00 €675,266.00

VAT at 21% For inspection purposes only. €141,805.90 Consent of copyright owner required for any other use. Project Supervision Total €817,071.90

Total Capital Cost Phase I (incl. VAT) €11,050,570.13

Annual Operation and Maintenance Cost Total Fixed Cost €270,532.00 Total Variable Cost €189,000.00 Total Operation and Maintenance Cost €459,532.00 VAT at 13.5% €62,036.82 Total Operation and Maintenance Cost (including VAT) €521,568.82

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Table 11.1 - Wastewater Treatment Works - Phase I Costs Item Description Amount (€) Total (€) A. Preliminary Treatment Plant Screenings washing and compaction 43,000 Grit classifier 26,000 Flow measurement equipment 13,000 Miscellaneous items 35,000 Associated accommodation Civils Work 120,000 237,000 B. Storm Treatment Plant Provision of new Storm tank and final pumping station 200,000 Cleaning mechanism 50,000 Storm overflow screen 30,000 Foul and Storm pumps 11,000 291,000 C. Inlet Pumping Station Civils works 80,000 Mechanical Plant 100,000 180,000 D. Secondary Treatment Plant Civils works 435,000 Provision of diffused air system 250,000 685,000 E. Additional Clarifiers Civils Works 180,000 Mechanical Plant 90,000 270,000 F. Tertiary Treatment Plant - Phosphorous Removal Additional Phosphate dosing plant 50,000 Chemical Dosing Building 35,000 85,000 G. Tertiary Treatment Plant - SS & BOD Removal 14500 PE Tertiary Treatment Plant 200,000 Civils Works 15,000 Pipework / instrumentation 20,000 235,000 H. Odour Removal Plant Inlet Works odour removal 70,000 70,000 For inspection purposes only. I. General Items Consent of copyright owner required for any other use. Electrical installation 100,000 Control panels 75,000 Connection to existing pipework 100,000 Flow Distribution Chambers 75,000 Instrumentation and control systems 75,000 Miscellaneous items / drawings / manuals / training 100,000 Siteworks 550,000 1,075,000 J. Buildings External Door Windows & Roofing 100,000 ESB Substation 28,000 New Air Blower Building 75,000 New Administration Building 115,000 318,000

Sub-Total 3,446,000 Add 20% for Preliminaries 689,200 Sub-Total 4,135,200 Add 10% Contingency 413,520 TOTAL € 4,548,720

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Table 11.2 - Wastewater Treatment Works - Phase II Costs Item Description Amount (€)

A. Aeration Basins Civils Work 410,000 Mechanical Plant 120,000 530,000

B. Secondary Clarifier Civils Work 180,000 Mechanical Plant 90,000 270,000

C. Tertiary Treatment plant BOD & SS Removal Civils Work 20,000 Mechanical Plant for 7500PE 130,000 150,000

D. Sludge Treatment Plant Sludge holding tank (glass-lined steel) 50,000 Picket fence thickener equipment: 30,000 Additional Sludge belt press and ancillaries 200,000 Additional Sludge pumping equipment 20,000 Pipework / instrumentation 20,000 Washwater and drainage pumps 30,000 350,000

E. General Items Electrical installation 10,000 Control panels 35,000 Instrumentation and control systems 35,000 Miscellaneous items / drawings / manuals / training 25,000 Siteworks 75,000 180,000

For inspection purposes only. Consent of copyright owner required Sub-Totalfor any other use. 1,480,000

Add 20% for Preliminaries 296,000 Sub-Total 1,776,000 Add 10% Contingency 177,600

TOTAL € 1,953,600

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Table 11.3 - Wastewater Treatment Works - Phase III Costs

Item Description Amount (€)

A. Aeration Basins Civils Work 410,000 Mechanical Plant 120,000 530,000

B. Secondary Clarifier Civils Work 180,000 Mechanical Plant 90,000 270,000

C. Tertiary Treatment plant BOD & SS Removal Civils Work 20,000 Mechanical Plant for 7500PE 130,000 150,000

D. General Items Electrical installation 10,000 Control panels 35,000 Instrumentation and control systems 35,000 Miscellaneous items / drawings / manuals / training 25,000 Siteworks 75,000 180,000

Sub-Total 1,130,000 Add 20% for Preliminaries 226,000 Sub-Total 1,356,000 Add 10% Contingency 135,600

TOTAL € 1,491,600 For inspection purposes only. Consent of copyright owner required for any other use.

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Table 11.4 - Pipeline Rehabilitation Costs Pipe Diameter Length to be Structural Cost Total Cost repaired Grade 150 27.5 3 € 114,142.00 1219.4 4 527.4 5

225 172.3 2 € 364,287.00 441.2 3 4907.5 4 802.2 5

300 142.2 4 € 28,293.00 27.8 5

375 155.8 3 € 12,000.00 209.1 4

450 42 4 € 1,228.00

525 351.5 4 € 10,592.00 € 530,542.00

Table 11.5 - Manhole Rehabilitation Costs

Works No. of Manholes Cost

Replace Cover 34 €10,200.00

For inspection purposes only. Reline ManholeConsent of copyright owner235 required for any other€218,049.00 use.

Repair Benching 85 €34,400.00 €262,649.00

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12. PROCUREMENT STRATEGY AND IMPLEMENTATION

12.1 Benefits of Traditional Procurement vs. DB/DBO Contracts

The advantages and disadvantages of a DB/DBO approach as against the traditional procurement approach of separate civil works and mechanical and electrical plant contracts needs to be examined. Consideration needs to be given to issues of cost, performance, time and risk as well as the overall feasibility of promoting the scheme using the DB/DBO approach.

It has been the experience with DB/DBO contracts that submissions from Contractors/Consortia at Tender Stage invariably include a variety of proposals intended to address the needs of the project. Each proposal generally brings together the expertise of Civil Works and Process Plant contractors. In a competitive situation these will strive to provide the most economical solution to the problem. Subject to adherence to the specified requirements of the project this tendering process can present the project promoter with a number of different and perhaps innovative solutions.

At the construction stage the co-ordinated approach of the construction team will For inspection purposes only. eliminate many of the schedulingConsent of copyright conflicts owner required inherent for any other inuse. the traditional method where

Civil Works and Plant Contractor interaction often leads to delay and disruption, with a consequent adverse affect on project cost.

An added advantage offered by a DB/DBO contract is that at an early stage in the project the likely out-turn can be established with greater certainty than with the traditional procurement method. This facilitates a more effective financial management of the project and indeed can have beneficial effects also for other projects whose funding is derived from the same source.

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12.1.1 Design and Build

For the procurement of a Wastewater Treatment Works the benefits of a design and build approach are clear. Flexibility can be exercised to ensure acquisition of the best value plant. The performance risk associated with advanced technologies is carried by those most able to manage it, the contractors. The advantages of the Design Build approach however do not benefit the pipelaying contract as this contract has little scope for innovation and would be very prescriptive.

12.1.2 Operating

Plants of this nature require well trained personnel to manage and operate them. This may be done by suitably trained council staff or let as an operating contract. If let as an operating contract there is no reason to divorce the plant operation from the design and build functions. There is also merit in tying operation to design as this ensures that the operation of the plant is clearly in the mind of the designers at an early stage.

The direct cost of operation may be higher in certain circumstances if it is let as an operating contract. This takes account of the profit and transfer of risk elements. However the higher direct cost may be more than covered by the indirect savings gained through efficient operation of the plant. It is important when drawing up the For inspection purposes only. Consent of copyright owner required for any other use. operating contract to consider carefully who is best able to manage potential risks. Often a policy of maximum transfer of risk results in higher than necessary operating costs.

The option of including the operation of the network in a DBO for the WWTW is a possibility however this would represent a large risk to any potential Contractor given the current condition of the network and uncertainty of the results of repair at tender stage. Therefore the inclusion of the operation of the network in this DBO Contract is not recommended. However including the new and refurbished pumping stations in the DBO contract allows the contractor the ability to exercise control on the flows to the plant at the same time as making him responsible for the construction and operation of the new/refurbished pumping stations.

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12.1.3 Programme

From contract award onwards a design and build approach is generally accepted to be quicker than a conventional contract. However preparation of the tender documentation, tender assessment and dealing with the planning aspects of a wider scope approach, generally requires a longer period of time.. On balance, there is no significant time saving to be gained by either approach.

12.2 Procurement Strategy

Having considered all the matters discussed above, the procurement strategy recommended for the Edenderry Sewerage Improvement Scheme is as follows:

Contract Strategy

Wastewater Treatment Works Design Build and Operate for 20 years

Wastewater Collection System Traditional

Pumping Stations Optional

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13. CONCLUSIONS AND RECOMMENDATIONS

13.1 Conclusions

On the basis of the examination set out in this Preliminary Report the following conclusions are drawn:

a) An extension of the existing Wastewater Treatment Works is necessary to cater for the projected increase in wastewater flows over the coming years. b) This extension should take place on a phased basis in accordance with development pressures up to the year 2028. c) The effluent quality standards from the selected treatment process must meet the requirements of all current statutory environmental regulations applying to discharges to fresh waters. d) The existing outfall pipe to the River Boyne has adequate capacity to cater for the projected flows. e) An Environmental Impact Assessment will be required for the expansion of the Wastewater Treatment Works. f) The option of Design, Build and Operate for 20 years is the preferred Procurement Strategy for the Wastewater Treatment Works Contract. For inspection purposes only. g) A mathematical modelConsent of ofcopyright the ownerWastewater required for any Collection other use. System has indicated that

the network is operating reasonably well in times of dry weather. h) During wet weather and storm conditions many sections of the network are surcharged leading to unscreened discharges at overflows and/or flooding. i) Likewise the pumping stations along the collection network experience similar operating conditions as the remainder of the network as set out in g) and h) above. j) Relief sewers and upgraded pumping stations shall need to be constructed in order to develop a proper collection system. k) Extensions to the collection network shall be required to cater for area zoned for future development.

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l) A CCTV and SUS 2000 survey of the existing pipeline system, manholes and pumping stations has highlighted areas which shall require repair and remediation. m) All proposed works to the Wastewater Collection System should be procured using the Traditional Method.

13.2 Recommendations

In consideration of the above, we recommend the following:

a) Expansion of the Wastewater Treatment Works should proceed on a phased basis to 2028 (25 Year Planning Horizon). Phase I which involves expansion of both the Wastewater Treatment Works and the Collection Network at a capital cost of €11,050,570 including VAT should proceed immediately. b) The proposed extension to the Wastewater Treatment Works should be constructed on lands adjacent to the existing works. c) An Environmental Impact Assessment should be prepared for the expansion to the Wastewater Treatment Works. d) Improvements to the existing Wastewater Collection System, including repair and rehabilitation to pipelines should proceed.

For inspection purposes only. e) Provision of increasConsented of copyright pumping owner required and forstorage any other use. capacity at pumping stations

should proceed. f) Extensions to the existing Wastewater Collection System should proceed in parallel with new development. g) Detailed topographical and site investigation surveys of the catchment will be necessary to produce Contract Documents. h) Generally the works as proposed for the Edenderry Sewerage Improvement Scheme as set out in this report should proceed in order to allow the planned progressive development of the town and to avoid further deterioration of the current receiving waters.

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We trust this report meets your current requirements. We are available at any stage to discuss any aspect of the report and in the meantime we await your further instructions.

Signed: ______G. Monaghan for NICHOLAS O’DWYER LTD.

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OFFALY COUNTY COUNCIL

EDENDERRY SEWERAGE IMPROVEMENT SCHEME

PRELIMINARY REPORT

VOLUME II

APPENDICES

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Nicholas O’Dwyer Ltd., Offaly County Council, Consulting Engineers, County Buildings, Nutgrove Office Park, Charleville Road, Nutgrove Avenue, Tullamore, Dublin 14. Co. Offaly. Revision B – June 2005

PROJECT NO. 20290 Prepared by Approved by Issued by Initials Date Initials Date Initials Date Revision Reason for Revision GM 12/12/03 GM 12/12/03 JP 12/12/03 A Incorporate Client comments. GM 13/12/04 GM 13/12/04 JP 13/12/04 B Final Revisions GM 13/06/05 GM 13/06/05 JP 13/6/05 C D

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