document control sheet - epaclient dun laoghaire rathdown county council/bray udc project title...

Shanganagh & Bray Main Drainage Scheme Wastewater Treatment Works EIS

MCOS\088-012-1-1-R023.doc

DOCUMENT CONTROL SHEET

Client Dun Laoghaire Rathdown County Council/Bray UDC

Project Title Shanganagh & Bray Main Drainage Scheme

Document Title Wastewater Treatment Works EIS

Document No. 088-012-1-1-R023.doc

This Document Comprises DCS TOC Text List of Tables List of Figures

No of Pages 1 3 63 1 1

Revision Status Author(s) Reviewed By Approved By Issue Date

D1 Draft J. O’Neill Glenn Starr Jerry Grant 19/12/00

D2 Draft J. O’Neill John McCarthy Jerry Grant 29/3/01

F1 Final Draft J. O’Neill

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TABLE OF CONTENTS

PART A - SUMMARY ................................................................................................................................. 1

A1 NON TECHNICAL SUMMARY ................................................................................................... 1 A1.1 Introduction ................................................................................................................................ 1 A1.2 The Existing Situation ................................................................................................................. 1 A1.3 Proposed Scheme and Alternatives ............................................................................................. 1 1.3.1 General .................................................................................................................................... 1 1.3.2 Technical Issues ....................................................................................................................... 2 1.3.3 General .................................................................................................................................... 3 A1.4 Potential Impacts and Proposed Mitigation Measures............................................................... 3 1.4.1 General .................................................................................................................................... 3 1.4.2 Odour ....................................................................................................................................... 3 1.4.3 Visual and Landscape .............................................................................................................. 4 1.4.4 Noise ........................................................................................................................................ 5 1.4.5 Construction............................................................................................................................. 6 A1.5 Conclusion .................................................................................................................................. 7

PART B – GENERAL & BACKGROUND INFORMATION ................................................................. 1

B1 GENERAL INFORMATION ......................................................................................................... 1 B1.1 Scope of EIS ................................................................................................................................ 1 B1.2 Legislative Context...................................................................................................................... 1 B1.3 Structure of the EIS..................................................................................................................... 2 B1.4 Public Consultation .................................................................................................................... 2 1.4.1 Public ...................................................................................................................................... 2 1.4.2 Statutory Bodies ....................................................................................................................... 3 B1.5 Interaction of Environmental Impacts ........................................................................................ 3

B2 BACKGROUND TO THE PROJECT ............................................................................................ 4 B2.1 Introduction ................................................................................................................................ 4 B2.2 Present Position .......................................................................................................................... 4 2.2.1 Catchments.............................................................................................................................. 4 B2.3 Existing Loads............................................................................................................................. 5 B2.4 Receiving Waters ........................................................................................................................ 5 2.4.1 Bray Historical Water Quality ................................................................................................. 5 2.4.2 Shanganagh Historical Water Quality..................................................................................... 5 B2.5 Need for the Scheme.................................................................................................................... 6 B2.6 Do Minimum Situation................................................................................................................ 6

PART C – PROPOSED PROJECT ............................................................................................................ 7

C1. DESCRIPTION OF THE PROPOSED PROJECT.......................................................................... 7 C1.1 Introduction ................................................................................................................................ 7 C1.2 Proposed Scheme........................................................................................................................ 7 1.2.1 Procurement............................................................................................................................ 7 1.2.2 Future Loading ....................................................................................................................... 7 1.2.3 Wastewater Process Options................................................................................................... 8 1.2.4 Sludge treatment process options............................................................................................ 9 1.2.5 Design Issues .......................................................................................................................... 9 1.2.6 Planning.................................................................................................................................. 9 1.2.7 Operation .............................................................................................................................. 10 1.2.8 Phased Upgrading ................................................................................................................ 10 1.2.9 Bio-Solids Disposal............................................................................................................... 10 C1.3 Off-Site Developments............................................................................................................... 12 1.3.1 Foul and Storm Sewers ......................................................................................................... 12 1.3.2 Wastewater Storage at Bray.................................................................................................. 12 1.3.3 Wastewater Conveyance from Bray ...................................................................................... 13

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C2. ALTERNATIVES CONSIDERED............................................................................................... 14 C2.1 Introduction .............................................................................................................................. 14 C2.2 Separate Treatment at Shanganagh and Bray .......................................................................... 14 C2.3 Greenfield Sites......................................................................................................................... 14 2.3.1 Site Option C.......................................................................................................................... 14 2.3.2 Site Option D.......................................................................................................................... 14 2.3.3 Site Option E.......................................................................................................................... 14 C2.4 Alternative Sites Elimination .................................................................................................... 15 2.4.1 Environmental and Practical Issues ...................................................................................... 14 2.4.2 Cost Comparison ................................................................................................................... 14

C3 PUBLIC CONSULTATION......................................................................................................... 16 C3.1 Introduction .............................................................................................................................. 16 C3.2 Submissions............................................................................................................................... 16

PART D – SIGNIFICANT IMPACTS...................................................................................................... 19

D1. HUMAN BEINGS ............................................................................................................................. 19 D1.1 Description of Existing Environment ........................................................................................ 19 D1.2 Socio-Economic ........................................................................................................................ 19 D1.3 Potential Significant Impacts and Mitigation Measures........................................................... 19 1.3.1 Health & Safety...................................................................................................................... 18 1.3.2 Nuisance................................................................................................................................. 19 1.3.3 Visual/Intrusion Obstruction.................................................................................................. 19 1.3.4 Amenity/Green Areas ............................................................................................................. 19 1.3.5 Construction........................................................................................................................... 20 D1.4 Residual Impacts....................................................................................................................... 21 D1.5 Compensatory Measures........................................................................................................... 21

D2. AIR AND ODOUR ............................................................................................................................ 22 D2.1 Introduction .............................................................................................................................. 22 D2.2 Wastewater Treatment Works Odours ...................................................................................... 22 2.2.1 Odour emissions from wastewater processes......................................................................... 22 2.2.2 Odour standards for wastewater treatment plants................................................................. 22 2.2.3 Odour abatement at wastewater treatment plants ................................................................. 22 D2.3 Odour Dispersion Model .......................................................................................................... 24 2.3.1 Treatment works odour emission estimates ........................................................................... 23 2.3.2 Existing plant - Results of dispersion analysis....................................................................... 23 2.3.3 Option A1; Process odour emission estimates ....................................................................... 24 2.3.4 Option A1; Results of dispersion analysis.............................................................................. 24 2.3.5 Option A6; Process odour emission estimates ...................................................................... 24 2.3.6 Option A6; Results of dispersion analysis.............................................................................. 24 2.3.7 Odour control measures......................................................................................................... 25 2.3.8 Residual Impacts.................................................................................................................... 25

D3. CLIMATE........................................................................................................................................ 27 D3.1 Introduction .............................................................................................................................. 27 D3.2 Energy Requirements ................................................................................................................ 27 D3.3 Greenhouse Gas Emissions....................................................................................................... 27

D4. NOISE AND VIBRATION........................................................................................................... 29 D4.1 Introduction .............................................................................................................................. 29 D4.2 Methodology ............................................................................................................................. 29 D4.3 Existing Environment................................................................................................................ 29 D4.4 Typical Noise Emissions ........................................................................................................... 30 D4.5 Potential Impacts and Mitigation Measures ............................................................................. 30 D4.6 Residual Impacts....................................................................................................................... 30

D5. LANDSCAPE............................................................................................................................... 32 D5.1 Introduction .............................................................................................................................. 32 D5.2 Outline of Proposed Development ............................................................................................ 32 D5.3 Description of Existing Environment ........................................................................................ 32 5.3.1 Landscape Characteristics..................................................................................................... 38 D5.4 Potential Significant Impacts .................................................................................................... 39

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D5.5 Mitigation Measures ................................................................................................................. 40 D5.6 Residual Impacts....................................................................................................................... 40

D6. FLORA AND FAUNA ................................................................................................................. 41 D6.1 Introduction .............................................................................................................................. 41 D6.2 Habitats..................................................................................................................................... 41 6.2.1 Amenity Grassland................................................................................................................. 41 6.2.2 Hedgerow............................................................................................................................... 41 6.2.3 Adjacent Habitats................................................................................................................... 41 D6.3 Fauna........................................................................................................................................ 42 D6.4 Site Evaluation.......................................................................................................................... 43 D6.5 Potential Impacts ...................................................................................................................... 43 D6.6 Mitigation Measures ................................................................................................................. 43 D6.7 Residual Impacts....................................................................................................................... 43

D7. MARINE ENVIRONMENT......................................................................................................... 44 D7.1 Introduction .............................................................................................................................. 44 D7.2 Legislation and Guidelines ....................................................................................................... 44 7.2.1 Shellfish and Bathing Water Directives ................................................................................. 44 7.2.2 Urban Wastewater Treatment Directive ................................................................................ 44 7.2.3 Current Outfall Effluent Characteristics................................................................................ 45 D7.3 Dispersion Model Development................................................................................................ 45 7.3.1 Existing Contamination Parameters ...................................................................................... 46 7.3.2 Dispersion Model Results - Bray ........................................................................................... 46 7.3.3 Dispersion Model Results - Shanganagh ............................................................................... 47 D7.4 Future Situation - Flowrates and Concentrations .................................................................... 48 D7.5 Future Situation Results............................................................................................................ 49 7.5.1 Bray........................................................................................................................................ 49 7.5.2 Shanganagh............................................................................................................................ 49 7.5.3 Dalkey Island/Muglins Island ................................................................................................ 49 D7.6 Existing Marine Environment ................................................................................................... 50 7.6.1 Methodology .......................................................................................................................... 50 7.6.2 Water Chemistry .................................................................................................................... 51 7.6.3 Sediment Chemistry................................................................................................................ 51 7.6.4 Fauna ..................................................................................................................................... 51 D7.7 Conclusion ................................................................................................................................ 52 7.7.1 Potential Significant Impacts and Mitigation Measures ........................................................ 52 7.7.2 Residual Impacts.................................................................................................................... 52

D8. GEOLOGY, HYDROGEOLOGY AND SOIL ............................................................................. 53 D8.1 Introduction .............................................................................................................................. 53 D8.2 Description of Existing Environment ........................................................................................ 53 D8.3 Potential Significant Impacts .................................................................................................... 53

D9. MATERIAL ASSETS................................................................................................................... 54 D9.1 Introduction .............................................................................................................................. 54 D9.2 Description of Existing Environment ........................................................................................ 54 D9.3 Potential Significant Impacts .................................................................................................... 54 D9.4 Mitigation Measures ................................................................................................................. 54 D9.5 Residual Impacts....................................................................................................................... 55

D10. CULTURAL HERITAGE............................................................................................................. 56 D10.1 Introduction........................................................................................................................... 56 D10.2 Description of Existing Environment .................................................................................... 56 D10.3 Potential Significant Impacts ................................................................................................ 56 D10.4 Mitigation Measures and Residual Impacts.......................................................................... 56

D11. CONSTRUCTION PHASE .......................................................................................................... 57 D11.1 Introduction........................................................................................................................... 57 D11.2 Construction Period.............................................................................................................. 57 D11.3 Advance Work for Utilities.................................................................................................... 57 D11.4 Traffic Management.............................................................................................................. 57 D11.5 Programme of Works ............................................................................................................ 58

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D11.6 Effects on Human Beings and Proposed Mitigation Measures............................................. 58 11.6.1 Residential Property .......................................................................................................... 58 11.6.2 Noise .................................................................................................................................. 58 11.6.3 Vibration ............................................................................................................................ 57 11.6.4 Working Hours................................................................................................................... 57 D11.7 Effects on Flora and Fauna .................................................................................................. 59 D11.8 Effects on Soils ...................................................................................................................... 59 D11.9 Effects on Watercourses........................................................................................................ 59 D11.10 Effects on Air......................................................................................................................... 60 D11.11 Effects on Climate ............................................................................................................. 60 D11.12 Effects on Landscape ............................................................................................................ 60 D11.13 Effects on Material Assets..................................................................................................... 60 D11.14 Effects on Cultural Heritage ................................................................................................. 60 D11.15 Damage to Existing Roads.................................................................................................... 61 D11.16 Mud on Roads ....................................................................................................................... 61 D11.17 Privately and Publicly Owned Services ................................................................................ 61 D11.18 Conclusion ............................................................................................................................ 62

List of Figures

Fig A1 – Existing Facility Fig A2 – High Tankage option Fig A3 – Low Tankage option Fig A4 – Indicative view from Shanganagh Cliffs Fig A5 – Odour Modelling Results Fig B2.1 – Existing Shanganagh Works Fig B2.2 – Shanganagh and Bray Catchment map Fig C1.1 – Proposed layout – High Tankage Process Option Fig C1.2 – Proposed layout – Low Tankage Process Option Fig C1.3 – Proposed Sections Fig C1.4 – Shanganagh Site Land use Zonings Fig C1.5 – Transfer Pipeline & Site Options Fig D2.1 – Option A1: 98%ile Odour Isoline Fig D2.2 – Option A6: 98%ile Odour Isoline Fig D4.1 – Location of Baseline Noise Measurements Fig D5.1 – Indicative view from Bayview Fig D5.2 – Indicative view from Shanganagh Cliffs Fig D5.3 – Indicative view from Open Space at Beach Fig D7.1 – Location of Marine Sampling Sites

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List of Tables Table A1. – Potential Significant Environmental Impacts Table B2.3 – Existing Load as Population Equivalent Table C2.4 – Cost of Treatment Options Table D7.2 – Outfall Effluent Sampling Results Table D7.3 – Existing Model Parameters Table D7.4 – Future Model Effluent Discharge Parameters at Bray & Shanganagh Table D7.5 – Future Situation Results

LIST OF APPENDICES

Appendix 1 - Report on “Control of Odour Emission” Appendix 2 - Report on “Noise Aspects” Appendix 3 - Report on “Marine Sediment, Water Chemistry & Benthic Fauna”

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PART A - SUMMARY

A1 NON TECHNICAL SUMMARY

A1.1 INTRODUCTION Dun Laoghaire-Rathdown County Council (DLRCC) proposes to upgrade the existing Shanganagh Wastewater Disposal Works by enlarging the existing site so as to accommodate full secondary treatment. In accordance with the legal requirements for such a scheme an Environmental Impact Statement has been prepared and this is the summary in non-technical language of that statement. The purpose of this scheme is to upgrade the existing plant at Shanganagh in line with the Urban Wastewater Treatment Directive and associated Irish Regulations and to comply generally with other EU directives and National Regulations pertaining to the protection of the environment. The E.I.S. is prepared in accordance with the requirements of the European Communities (Environmental Impact Assessment) Regulations 1989 – 2000. The E.I.S. involves a description of the proposed scheme and alternatives (Part C) and detailed appraisal of environmental impacts under a range of headings (Part D). It is available for inspection or purchase at DLRCC council offices Dun Laoghaire. This non-technical summary briefly describes the significant impacts of the scheme. Following completion of the E.I.S., it will be submitted to An Bord Pleanala for assessment.

A1.2 THE EXISTING SITUATION At present the existing Dun Laoghaire -Rathdown County Council site at Shanganagh caters for pumping screened sewage directly to the sea via a 1.6km outfall pipe off the shore at Killiney Beach. In 1983 the plant was upgraded to cater for a potential population equivalent (“PE”) of 250,000, though the actual current load is in the order of 60,000 – 70,000 population equivalent. The design capacity in 1983 included provision for Bray. The separate pumping station and outfall at Bray were commissioned in the early 1990’s to serve Bray independently of Shanganagh. There are, under prevailing conditions, genuine concerns relating to water quality at Bray Beach, Killiney Beach, Bullock Harbour, Dalkey Sound and Island. An extension of the collecting networks to service newly developed areas with increase in loads could result in water quality degradation and increased public health risks. There are no special designations or conditions in the area, which should warrant more than normal secondary treatment.

A1.3 PROPOSED SCHEME AND ALTERNATIVES A1.3.1 General The existing site at Shanganagh, somewhat enlarged, will accommodate upgrading of the facilities to full secondary treatment. This will entail extension of the site southwards so as to facilitate a treatment works with the capacity to treat both catchments (Bray & Shanganagh) on a single combined site. There will also be ancillary works involving catchment modifications including the installation of a pipeline from Bray, all of which are dealt with under separate planning procedures.

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The level of treatment proposed corresponds to normal secondary treatment, providing for over 90% removal of organic pollution load and suspended solids and achieving around a 50-100-fold reduction in bacteria. The effluent is discharged to the open sea and detailed studies have shown that there is no requirement for nutrient removal or tertiary treatment (with the possible exception of disinfection). The level of bacterial removal has been demonstrated to comfortably satisfy “Blue Flag” criteria at Killiney Beach. Retrofitting of disinfection treatment could be implemented in the future, for water quality improvement around Dalkey Island, if future conditions warrant it. Present loads from both catchments are estimated at 103,000 Population Equivalent (PE). The plant will provide for 160,000 PE to satisfy proposed developments, with scope on site to go to 200,000 PE ultimately if necessary. The outfall capacity of 250,000 PE can comfortably cater for future needs of both Bray and Shanganagh. The current public policy as outlined by the Department of the Environment and Local Government is to procure wastewater treatment facilities by a Public Private Partnership (PPP) contract. There are several types of PPP contract arrangements and the one favoured in this case is a Design Build Operate (DBO) approach, where a Contractor is procured to design and build a plant and operate it for a defined period of years to clearly defined standards. For the DBO process to work correctly it is important that the tenderers are not confined too rigidly in their options while meeting the performance criteria defined in this EIS. To this end, several process options and site layouts are identified and described in this document to define the type of development, which is likely. In a DBO contract, a contractor will be appointed to carry out detailed design, construction and long term operation of the works in accordance with this EIS. A1.3.2 Technical Issues

Wastewater Process Options – The standards required necessitate normal secondary treatment solutions. Hence there are a number of different processes, which would be suitable and are described in more detail by the EIS document. The Shanganagh existing pump station and outfall will be retained and incorporated into the proposed works. The treatment plant will be highly automated with some redundancy built in to accommodate maintenance and some load variations. The potential different processes involved are represented by a high tankage option (Fig A2) and a low tankage option (Fig A3);

Sludge Treatment Process Options – various options are described in relation to

sludge including digestion, dewatering and thermal drying to produce totally innocuous and dry biosolid material;

Planning - Expansion of the site will be required to accommodate a secondary treatment

plant for the combined Bray and Shanganagh Catchments. The existing site is currently operating as a preliminary treatment works and the proposed upgrading of the plant would be consistent with this existing use and is an objective of the 1998 Development Plan. The site will be extended into the open green space with a land take of around 1.5ha. The Contractor will also require a temporary site compound of around 1.0 ha adjacent to the site. In the development of the site, the objective of protecting and improving residential amenity is recognised and the architectural, landscape and boundary treatment of the site will reflect this objective;

Phased Upgrading – Space will be allowed on the site to cater for a future population

equivalent of 200,000, with a mid term capacity for 160,000.;

Biosolids Disposal – Septic tank sludges from the DLRCC area will be brought into the treatment plant by tanker to be combined with sludges generated on site. Disposal options considered for treated sludge biosolids are re-use to land within DLRCC, Bray Urban District Council (BUDC) and County Wicklow boundaries or in neighbouring counties on agricultural, amenity or forestry lands as a general-use fertiliser, or otherwise

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as permitted by County Sludge Management Plans. In the future, disposal by incineration as part of the Dublin Waste Management Plan may be possible. Total traffic volume from the collection and disposal of sludge will be around seven return journeys per week;

Local Liaison Committee – This committee will be set-up at the beginning of the

consultation phase to inform and consult the public and affected parties local to the site. It will also have a mandate to discuss possible compensatory measures to mitigate the impact on community facilities and will continue to be active during the construction phase, (see below);

Site Expansion - the expansion of the site to the south to accommodate the

development will result in loss of amenity and recreational facilities. This impact will be mitigated by provision of compensatory facilities as part of the development;

Offsite Developments – These include foul and storm sewer separation and

rehabilitation, wastewater storage at Bray and wastewater conveyance from Bray to Shanganagh. The works at Bray and the pipeline from Bray to Shanganagh will be subject to separate statutory process; and

Construction – The required development is relatively large so the construction phase

will require careful management. To this end, a Local Liaison Committee will be set-up to co-ordinate the timing of critical activities and to serve as an information conduit between the Contractor, the Council and the Public, with a view to mitigating adverse environmental impacts during the construction phase.

A1.3.3 Alternatives Considered:

Separate Treatment at Shanganagh and Bray – not suitable due to restricted area and

high cost of separate plant at Bray, with loss of efficiency for two plants, and Greenfield sites – while some options are technically feasible, they would involve large

additional costs and would not be consistent with planning objectives. The most cost effective whole life option strongly favours a combined wastewater treatment plant at Shanganagh with potential savings in the order of £15-20million.

A1.4 POTENTIAL IMPACTS AND PROPOSED MITIGATION MEASURES A1.4.1 General The upgrading of Shanganagh Wastewater Treatment Works will have potential impacts on various aspects of the environment. These impacts may be direct or indirect. The impacts on all of the issues considered are covered comprehensively in Part D of the EIS and are summarised in Table 1. However, the most important ones are discussed in more detail below: A1.4.2 Odour Prior to the installation of the Shanganagh Pumping Station in 1984 there were severe offensive odours generated at the site from septic tank treatment of the wastewater. The installation of the pumping station significantly reduced the odour levels. However, most of the tankage and storage skips for screenings, etc., are open to the air and some odours are currently generated, though nuisance levels are minimal. The proposed secondary treatment plant at the site will result in a further reduction of odour generation at the site, through containment of contaminated air and treatment to remove odours before discharge.

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Odour modelling was conducted on the option with the highest potential for odour, that is, Option A1 which has a high proportion of open tankage. The model development consists of applying typical odour generation rates to the various types of process tankage; the unit of measure being the Odour Unit (OU). The OU’s numerical value is quantified as the number of dilutions with clean air required to reach the odour perception threshold. The odour perception threshold is the lowest odour concentration, which is detectable by half the members of a test panel (half the members do not detect any smell while the other half still smells something). At a concentration of 2 OU/m3 an odour is faintly perceivable, at 3 OU/m3 it is clearly perceivable while at 5 OU/m3 is strongly perceivable and, if unpleasant, is likely to give rise to environmental nuisance. The wind regime is also very important for odour modeling and a typical year of wind strength and directions was input into the model. Specific odour control measures were assumed for the site including covering and foul air treatment of the inlet works, sludge facilities and primary sedimentation tanks. The resultant odour generation at the site was then estimated at significantly less than the present condition; this is represented on Figure A5. Figure A5 displays 98 percentile – 1 OU isolines, which represent the extent of odour detection (not nuisance) which will occur 2% of the time. That is, for 98 % of the time the detection threshold will be closer to, or inside, the plant boundary. The reason why the isolines are reasonably in line with the plant boundary is that the critical time for odour generation occurs during low wind conditions where the benefits of mixing are not apparent. The results of the modeling are consistent with the recent observations made by the study tour group to Denmark where a number of treatment plants were visited with houses constructed right up to the plant boundary. In some cases the treatment plants, although well designed and managed, had limited odour control facilities and yet no odour problems were exhibited. A1.4.3 Visual and Landscape The treatment plant will be a large development as displayed on Figures A2 and A3 and has therefore been given careful consideration with respect to landscape mitigation measures. The existing treatment plant facility is located on a well-maintained site, which is not widely visible or visually intrusive. In effect, visibility is restricted to the nearest edge of development at Bayview and Shanganagh Cliffs and from occasional areas along the coastal open space. The overall visibility is greatly reduced by the flat nature of the landscape, the extent of surrounding development, the presence of the elevated DART line and the existing planting associated with the rail-line, the Shanganagh stream and the southern boundary of the site. However, the treatment plant is visible from the upper rear floor windows of the immediate residences along Bayview Lawns, Bayview Close and Shanganagh Cliffs. From Bayview the development has little visual impact because of the low-level nature of the existing development; the narrow angle of view and the presence of the intervening elevated rail-line and associated planting in the foreground. Importantly, the development does not restrict open views eastwards to the sea. From the rear of Shanganagh Cliffs Estate, the landscape rises slightly towards the site where the combination of the presence of an old remnant hedgerow and the low level of the development screens all but the upper levels of the main building.

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The proposed development will involve new buildings, tanks and other structures (Fig. A2,A3 and A4) described in more detail in the main volume and which will be mitigated by the following measures:- Taller tank structures would be located in the south-west corner of the site where ground

levels will be reduced, thereby setting the structures into surrounding ground levels and minimising visual intrusion to Bayview or Shanganagh Cliffs Estates;

Where possible the various buildings would be collected together and arranged in a coherent

‘courtyard style’ layout to the south of the site thereby avoiding visual clutter within the site and visual intrusion on views from the open space. In siting the buildings the top of development level should take into account the top of ridge levels of the houses in Shanganagh Cliffs; thereby retaining the views south to Bray Head. Some local reduction of ground levels in the site will be required to achieve this objective;

With the exception of the existing pumping station, high development will be avoided along

the eastern boundary of the site, where only low tanks or ground-based development is located. Furthermore, the existing pumping station, which is to be retained will be upgraded architecturally to reflect the finish of the new building design;

The same coherent architectural treatment will extend to all building units including the

Inlet/Screening building, which is centrally located in the site;

A granite faced boundary wall will be constructed along the southern boundary and part of the eastern boundary as far as the existing site boundary fence. This will assist in screening the development from the Shanganagh Cliffs area. The existing planting along part of the eastern boundary will be retained and extended along the full eastern boundary; and

The open space between the site and the rear of Shanganagh Cliffs Estate will be remodeled

to provide additional screening, augmented by new planting. A1.4.4 Noise Noise monitoring was conducted adjacent to the site at Bayview and Shanganagh Cliffs Estates to determine the existing background levels. The resultant night-time background level was determined at around 40 decibels dB(A). Due to the continuous nature of the plant operation, the night-time operation is of major importance, as this requires a lower limit than daytime. There are no statutory limits for environmental noise emissions for this type of plant, or industry in general, in this country. In general, noise is likely to provoke complaints when its level exceeds the level of the background noise level by a certain margin or when certain absolute levels are attained. The criteria for industrial noise generally lie in the range 35-45 dB(A) at night and 45-55 dB(A) by day. The lower values are normally applicable to rural areas and hospital zones, and the higher values are sometimes applicable to city centre areas or special cases such as mining or quarrying. Currently the most widely applied criteria for industry are that of 45 dB(A) (night-time) and 55 dB(A) (daytime) with no impulsive or tonal characteristics. Selection of the preferred noise criteria values within the range of values above depends on the pre-existing noise levels, the character of the area and the nature of the development. Taking the above into account and the existing “background” noise at the proposed location the following criteria are defined as being appropriate for minimal impact at Bayview and Shanganagh Cliffs Estate.

Night : 43 dB (hourly) Day : 55 dB (hourly)

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The night time level of increase over the existing background level will be barely detectable by the average person. This will be achieved by enclosing all significant noise producing elements so that a noise nuisance is not experienced outside the boundaries of the site. A1.4.5 Construction The proposed treatment facility will be a major construction exercise so careful consideration will be given to reducing the impacts and accommodating local concerns where possible. The following issues will be the most critical: Traffic Management There will be a significant amount of construction traffic during the estimated two-year contract period. There was a fatality in the Shanganagh Cliffs Estate during a gas pipeline construction, which indicates that particular care and attention needs to be paid to this aspect to ensure public, and in particular children’s safety. Some or all of the following measures would be appropriate for increasing public safety:

A 15 km/hr speed limit through the Shanganagh Cliffs Estate and appropriate limits in the adjoining estate

Traffic safety officer to ensure enforcement of the speed limit and to keep pedestrians off the road

Pointsmen during intense traffic movements at key intersections Installation of physical speed controls Construction of a temporary parallel access road on the seaward side of the Cliffs estate with pedestrian fencing

Tenderers will be instructed on the critical issue of public safety and the need to allow for it in their price. The successful tenderer will then be required to submit a detailed traffic management plan before construction commences, to be subject to the approval of Dun Laoghaire – Rathdown County Council traffic department. Noise and Vibration The impacts associated with noise and vibration levels come from construction plant such as excavators, dump trucks and compaction equipment. Contract documents will clearly specify that the contractor undertaking the works will be obliged to take specific noise abatement measures and comply with the recommendations of the British Standards. This will ensure noise impacts are kept to a minimum during the construction phase. Ground vibration from construction work is not expected to cause undue disturbance or structural damage. The contractor will be expected to limit vibrations, measured as peak particle velocity to less than 3mm/s for vibration from mechanical plant activity. Road Damage and Cleaning The movement of heavy goods vehicles transporting plant and materials along the existing local roads may cause damage and soiling to the roads.

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MCOS\088-012-1-1-R023.doc 7 Rev F1

Tracked plant will not be permitted on road surfaces outside the site boundaries unless adequate protective measures have been taken to safeguard the integrity of the road surface and the approval of Dun Laoghaire Rathdown County Council has been obtained. Measures to reduce mud nuisance will include, but not necessarily be limited to: The provision of easily cleaned hardstandings for vehicles entering, parking and leaving the

site. The provision of wheel washing facilities including, where practicable, mechanical wheel

spinners. The use of an approved mechanical road sweeper to clean the site hardstanding or any mud

or debris deposited by site vehicles on roads or footpaths in the vicinity of the site. The road sweeper is to be readily available whenever the need for cleaning arises and will be properly used and maintained.

The adequate sheeting of each lorry load of spoil removed to prevent spoil falling off during

its journey to the tip concerned. Working Hours Working hours during construction will be confined to the period 07:30 hours to 20:00 hours, Monday to Saturday, except for emergencies or as otherwise approved by the Dun Laoghaire – Rathdown County Council in exceptional circumstances.

A1.5 CONCLUSION The overall scheme including catchment modifications will help to improve economic and social conditions through the provision of a wastewater infrastructure capable of supporting a significant increase in residential, commercial and recreational development in the Bray-Shanganagh Catchments. The scheme will also improve the quality of the wastewater discharge at Shanganagh, which will benefit the Shanganagh and environs marine resources. Removal of the wastewater discharge at Bray, and reduction in the incidence of stormwater overflows, will similarly benefit water resources in the Bray area. The proposed facility is a relatively large development so there will be some moderate visual and landscape effects. These effects will be significantly mitigated due to a high standard of architecture, contro l led structure heights and effective screening. Some loss of amenity and community facilities will arise from the need to enlarge the site and will be mitigated by appropriate compensatory measures. The odour emission levels at the facility will be significantly improved from the current situation thus creating a residual positive effect. The noise level increase from treatment plant operation will be barely detectable. Construction impacts will be moderate at times, which will vary in magnitude during the construction phase. The Local Liaison Committee will serve a crucial function during the construction phase to inform the public of potentially disruptive events and to provide a conduit for public concerns.

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MCOS\088-012-1-1-R025.doc 8 A1

Table. A1 Potential Significant Environmental Impacts Section Category Environmental

Issues/Effects Potential Impact (+ve or –ve)

Mitigation Residual Impact

Human Beings

Health & Safety Boundary security

Negative

Secure gates and fencing and mature planting to exclude members of the public

None

Amenity Loss of recreational area

Negative

Appropriate Landscaping and provision of compensatory measures (refer to Figures A1-A4)

Slight

Sludge and biosolids truck traffic

Public Safety and disturbance

Negative Speed restrictions, low volume, truck washing requirement

Slight

Construction Traffic, noise, dust and vibration

- Refer to Construction Section -

Air & Odour

Odour

Nuisance

Negative

Provision of odour control and treatment facilities for all process units (refer to Figure A5)

Positive

Climate

Greenhouse gases Increase in Greenhouse gas effect

Negative Plant design options will result in negligible effect None

Noise & Vibration

Nuisance Increase in background noise levels

Negative Specified criteria will set limits on noise emissions so that there will be no significant increase in background noise levels

Slight

Landscape

Visual Obstruction Aesthetics Land take

Negative Negative Negative

Restricted structure heights and coherent layout Appropriate walls, screening and planting Landscaping of remaining space (refer to Figures A1-A4)

Moderate Moderate Slight

Flora & Fauna

Habitats Removal of on-site habitats

Negative Appropriate screen planting will initiate recolonisation from surrounding plant and animal species

Slight

Marine Environment

Water Quality Sediment Quality Marine Fauna

Deterioration Deterioration Deterioration

Negative Negative Negative

Provision of secondary treatment Provision of secondary treatment Provision of secondary treatment

Positive Positive Positive

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MCOS\088-012-1-1-R025.doc 9 A1

Table. A1 Potential Significant Environmental Impacts (Con’d) Section Category Environmental

Issues/Effects Potential Impact (+ve or –ve)

Mitigation Residual

Geology, Hydrogeology and soil

Site development Earth disturbance No Impact None Required None

Material Assets

Visual Land-use

Intrusion/Obstruction Amenity/Aesthetics

Negative Negative

Elevated screening and low level roofing Appropriate planting and maintenance of buffer zone (refer to Figures A1-A4)

Moderate Moderate

Cultural Heritage

Archaeology Disturbance of Archaeological material

Negative Archeological monitoring during topsoil strip None or positive

Construction

Human Beings Flora & Fauna Watercourses Landscape Material Assets Road conditions

Noise, Air, Traffic & Working hours Removal of habitats Siltation, erosion & pollution Visual Access & Nuisance Damage to existing roads and mud on roads

Negative Negative Negative Negative Negative Negative

Defined standards relating to noise levels, working hours, control of dust and emissions, siting of equipment. Traffic management plan and monitoring of noise and vibration. Active Local Liaison Committee during construction. Removal is temporary with a comprehensive planting programme as mitigation to replace and enhance lost habitat Installation of temporary sedimentation ponds to receive site run-off Visual intrusion will fluctuate according to location and type of activity Maintenance of access to houses and prior consultation with relevant properties Provision of appropriate daily maintenance systems and final reinstatement

Moderate Slight Slight Slight Slight Slight

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MCOS\088-012-1-1-R023.doc 1 Rev F1

PART B – GENERAL & BACKGROUND INFORMATION

B1 GENERAL INFORMATION B1.1 Scope of EIS This Environmental Impact Statement (EIS) examines the potential significant impacts of the proposed upgrading of the Shanganagh Wastewater Disposal Works. The purpose of the scheme is to upgrade these facilities in line with the Urban Wastewater Treatment Directive and to comply with the other EU directives and national regulations pertaining to protection of the environment. The statement has been prepared on behalf of Dun Laoghaire-Rathdown County Council and Bray Urban District Council by a team of specialist consultants who examined and identified the potential impact of the proposed scheme on the receiving environment. Mitigation measures are recommended to minimise any potential negative impacts. These recommendations have been incorporated into the scheme design, where possible within the bounds of engineering feasibility and within the terms of the clients brief. The statement has been prepared in accordance with the following:

The EU Directives on Environmental Impact Assessment (85/337/EEC) & (97/11/EEC) and associated National Regulations referred to as the European communities (Environmental Impact Assessment) Regulations, 1989 - 2000 (S.I. No. 349/1989, S.I. No. 84 of 1994, S.I. No. 101 of 1996, S.I. No. 351 of 1998, S.I. No. 93 of 1999 & S.I. No. 450 of 2000).

The Local Government (Planning and Development) Regulations, 1994 (S.I. No. 86 of 1994).

Advice notes on current practice in the preparation of Environmental Impact Statements published by the Environmental Protection Agency (1995).

The following legislation in relation to Irish Sea waters was also considered with respect to the marine environment adjacent to Shanganagh

Shellfish Water Directive (79/923/EEC) & National Regulations (S.I. 200 of 1994). Bathing Water Directive (76/160/EEC) & National Regulations (S.I. 155 of 1992). Urban Wastewater Treatment Directive (91/241/EEC) & National Regulations (S.I. 419 of

1994). B1.2 Legislative Context The EC Directives 85/337 & 97/11 on the assessment of the effects of certain public and private projects on the environment has been transposed into Irish legislation by the European communities (Environmental Impact Assessment) Regulations, 1989 - 2000 (S.I. No. 349/1989, S.I. No. 84 of 1994, S.I. No. 101 of 1996, S.I. No. 351 of 1998 & S.I. No. 93 of 1999 & S.I. No. 450 of 2000) and The Local Government (Planning and Development) Regulations, 1994 (S.I. No. 86 of 1994). The legislation requires that an authority prepare a statement of the likely effects on the environment of a proposed development such as the upgrading of Shanganagh Wastewater Disposal Works. The statement must include a description of the likely significant effects, both direct and indirect, on:

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MCOS\088-012-1-1-R023.doc 2 Rev F1

human beings, flora and fauna soil, water, air, climate and the landscape material assets cultural heritage the interaction between any of the matters referred to above

The legislation also requires that the public be notified, through the press, that the statement has been prepared and submitted to An Bord Pleanala. This notification must include the locations where the EIS may be viewed or purchased and the date by which written submissions in relation to the likely effects of the proposed effects of the proposed development on the environment must be received by An Bord Pleanala. An Bord Pleanala may request the relevant authority submitting the EIS to furnish him/her with specified additional information in relation to likely environmental effects of the proposed development. Before approving the proposed development, An Bord Pleanala shall consider the EIS, any additional specified information requested from the authority, and any submissions made by the public or prescribed bodies. An Bord Pleanala may also make provision for a public inquiry in relation to the proposed development. An Bord Pleanala may approve a proposed development with or without modification or he/she may refuse to approve such a development. An Bord Pleanala’s decision shall be published in the press. B1.3 Structure of the EIS The EIS comprises four main parts: Part A is a non-technical summary of the information contained in the EIS.

Part B gives general information about the project and discusses background and peripheral issues. Part C outlines the need for the scheme, describes the characteristics of the proposed scheme and looks at the alternative schemes considered. Part D describes the current receiving environment, examines and identifies the likely significant impacts of the proposed scheme on that environment, proposes measures to mitigate adverse impacts and identifies any residual impacts after mitigation. Potential impacts relating to the construction of the development are addressed in a separate chapter. B1.4 Public Consultation 1.4.1 Public The public was invited to take part in a number of consultation sessions during the development of the proposed scheme. These consultations were advertised by house to house leaflet delivery in the general vicinity of the site and in local press and radio. This process was a preliminary consultation ahead of the statutory process. It was conducted in order to facilitate any specific concerns for presentation in this formal EIS document. Displays were on view at Shanganagh Park House on 13th & 15th July & 3rd August, 2000 and at Dunlaoghaire-Rathdown County Hall, during office hours from Thursday 13th July until Friday 18th August 2000. Displays were also on view at Bray UDC offices on 19th & 20th July, 2000. County Council/Consultant staff were in attendance at these displays to answer questions on the proposed development.

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MCOS\088-012-1-1-R023.doc 3 Rev F1

A total of 25 submissions were received by Dun Laoghaire Rathdown County Council in respect of the overall Shanganagh – Bray main drainage scheme. A considerable amount of comments related to aspects concerning the Bray storm tank and proposed transfer pipeline, which are outside the scope of this EIS. No comments relating to the current proposal at Shanganagh were raised at the Public consultations in Bray. Issues raised in relation to Shanganagh submissions are listed and addressed in C3.2. 1.4.2 Statutory Bodies A list of the statutory bodies, government agencies and Non-Governmental Organisations (NGO’s) consulted during the development of the scheme and in relation to the preparation of this EIS are listed below:

Eastern Regional Fisheries Board; An Taisce; Birdwatch Ireland; Bord Failte; Coastwatch Europe; Duchas; Eastern Health Board; Environmental Protection Agency; Geological Survey of Ireland; Health and Safety Authority; Irish Underwater Council; Bord Iascaigh Mhara; Department of Marine and Natural Resources.

B1.5 Interaction of Environmental Aspects All aspects of the environment interact with one another to greater or lesser extent. A potential impact of the development on one aspect of the environment may have a significant knock-on effect on another aspect. For example any potential detrimental impact on water quality due to effluent discharges could potentially impact on the amenity value of the receiving waters in terms of bathing or fishing which in turn may have a detrimental impact on tourist potential. The most significant interactions between environmental aspects in relation to the proposed development are identified below. Interactions between one aspect and another are addressed under each aspect heading in Part D rather than in a specific interaction section

Human beings; the impact on human beings interacts most significantly with the following aspects of the environment; air quality, noise, landscape, cultural heritage, material assets and the marine environment in terms of amenity value and public health.

Flora and fauna; the impact on flora and fauna interacts most significantly with water

with respect to the marine environment and with air quality, noise, climate & soil with respect to the terrestrial environment.

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MCOS\088-012-1-1-R023.doc 4 Rev F1

B2 BACKGROUND TO THE PROJECT B2.1 Introduction The brief for this project requires the preparation of a Preliminary Report for a scheme, which would cover upgrading of the collection system, wastewater treatment and sludge disposal arrangements and the preparation of an Environmental Impact Statement (EIS) for any proposed wastewater treatment facilities identified. MC O’Sullivan Consulting Engineers were commissioned in 1998 to complete this work by Dunlaoghaire Rathdown County Council and Bray Urban District Council in conjunction with Wicklow County Council. The funding for this current investigation and future work will come from the Department of the Environment and Local Government. These studies include for the catchments of Shanganagh and Bray, including their county environs in Dun Laoghaire – Rathdown and Wicklow County Council areas respectively. The purpose of this scheme is to upgrade these facilities in line with the Urban Wastewater Treatment Directive and to comply generally with other EU directives and national regulations pertaining to protection of the environment. The work is being carried out in two parts as follows:

Preliminary Report (Part 1) & EIS; covering the wastewater and sludge treatment works, where the final Preliminary Report was presented to the Council in October, 2000. This EIS relates to the disposal works upgrading at Shanganagh.

Preliminary Report (Part 2) covering the catchment studies and upgrading of the foul sewer drainage network. This report will follow major field surveys currently in progress and is scheduled to be completed in approximately September 2001.

B2.2 Present Position 2.2.1 Catchments The existing works at Shanganagh provide for preliminary treatment before discharging via a 1200 mm diameter long sea outfall approximately 1.6km off the shore at Killiney beach. This plant was completed and commissioned in 1983 (Fig. B2.1). Historically there had been a treatment plant at this location, which was upgraded in 1983 to cater for significant population growth in the catchment. At that time, the outfall and pumping station were sized for up to 250,000 Population Equivalent (PE) and initially included provision for Bray. The plant provides screening and grit removal, before pump assisted discharge through the marine outfall. The Shanganagh and Bray catchments are shown in Fig. B2.2. The Shanganagh catchment in Dunlaoghaire – Rathdown County comprises the Deansgrange area, extending from Ballybrack to Foxrock and including such areas as Cabinteely, Clonkeen, Newtownpark Avenue and Leopardstown. It also includes the Carrickmines sub-catchment covering Stepaside, Ballyogan, Carrickmines and the southern area of Foxrock. The latter catchment has significant undeveloped areas, which are now zoned for development. The Bray catchment covers the town of Bray and some contiguous areas in Co. Wicklow and Dun Laoghaire – Rathdown. It is served by a system of sewers, some of which are combined in the older areas, draining to a major pumping station located adjacent to the river Dargle and the Harbour.

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MCOS\088-012-1-1-R023.doc 5 Rev F1

Following screenings and grit removal, the Bray sewage is pumped through a 680mm diameter and 1.6km long outfall. The Bray catchment includes older sewers in the town centre, which accept stormwater as well as foul flows and may also have significant infiltration (infiltration surveys currently in progress). The pumping station and outfall are relatively new, commissioned in the early 1990’s, but do not comply with the present requirements for urban wastewater treatment. B2.3 Existing Loads An assessment of current loads has been made from population studies and in-sewer measurements indicating the following:- Table B2.3 Existing load as Population Equivalent (PE)

SOURCE Shanganagh Bray Total

Domestic 57,700 29,800 87,500

Industrial 3,000 5,500 8,500

Landfill Leachate 5,000 2,000 7,000

Total 65,700 37,300 103,000

B2.4 Receiving Waters The following provides a little background information in relation to the marine environment. Chapter D7 examines this aspect in more detail. 3.4.1 Bray Historical Water Quality The Bray Beach is a popular and important holiday destination and is popular for swimming in the height of summer. However it has, until recently, been unable to satisfy the water quality criteria required for Blue Flag status. No recent capital or operational improvements to the system have occurred so it is questionable for how long the status can be retained under present conditions. The contamination at Bray comes from a number of sources including:

Urban stormwater run-off Birdlife in the River Dargle General contamination of the River Dargle Wastewater overflows from the Bray pumping station Wastewater discharge from the long sea outfall with on-shore conditions

3.4.2 Shanganagh Historical Water Quality The main bathing location adjacent to the outfall is Killiney Beach. However, the discharge also potentially impacts on Bullock Harbour, and around Dalkey Head on the flood tide. Killiney Beach consistently complies with the Bathing Water Directive guideline figures and has generally attained Blue Flag status. However during 1996 there were some failures of the Blue Flag guidelines, possibly due to adverse environmental conditions. Monitoring results for Bullock Harbour are not available. However, this area would historically have been affected by a local outfall now being intercepted through the provision of a new pumping station linking the Bullock Harbour area to the main Dun Laoghaire catchment, which is then pumped to Ringsend.

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MCOS\088-012-1-1-R023.doc 6 Rev F1

Dalkey Sound and Island are not strictly used for bathing, although it is a popular location for scuba diving and snorkelling and hence should be considered in relation to the water quality standards. There is no historical sampling data from this area however as part of this investigation 10 water quality samples were taken at three locations around Dalkey Island, which generally showed compliance with the standards. Contrary to this result, dispersion modelling work predicts possible non-compliance during certain conditions – the modelling is considered to be more reliable in this instance considering the short sampling sequence. Hence there is an existing contamination issue around Dalkey Sound and Island. B2.5 Need for the Scheme The marine environment adjacent to Bray and Shanganagh is not considered sensitive and there is no designation requiring advanced effluent treatment over and above normal secondary treatment. There is, however, the following relevant legislation that must be complied with in relation to these Irish Sea waters:

Shellfish Water Directive (79/923/EEC) Bathing Water Directive (76/160/EEC) Urban Wastewater Treatment Directive

Treatment of sewage effluent discharged to a minimum of secondary treatment standard is considered necessary to comply with this legislation B2.6 Do Minimum Situation The do minimum situation would involve only extending the collection network to service the new development areas. This would result in the following effects:

Annual fines could be levied by the EU on the central government. Risk of wastewater overflows during rain events would increase thereby jeopardising

public health and fresh water ecology. Further degradation of the water quality at Bray Promenade. Increased risk of contamination at Killiney Beach. Possible non-compliance of mandatory water quality limits at Dalkey Sound. The Shanganagh & Bray catchments without this development will have difficulties in

socio-economic terms by being at a distinct disadvantage in relation to catering for proposed new residential, commercial and leisure developments.

All of the issues above have significant adverse implications attached whether considered on their own or in various combinations. The probability of these effects being realised is quite high. The “do minimum” situation is therefore not acceptable from a statutory compliance or environmental risk management perspective.

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MCOS\088-012-1-1-R023.doc 7 Rev F1

PART C – PROPOSED PROJECT

C1. DESCRIPTION OF THE PROPOSED PROJECT C1.1 Introduction The proposed development involves the upgrade of the existing Shanganagh Wastewater Disposal Works to facilitate the treatment of sewage generated in the Shanganagh and Bray catchments (Figs C1.1 – 1.4). There will be ancillary works involving catchment modifications including the installation of a pipeline from Bray, all of which are dealt with under a separate planning procedure but which are described generally here for completeness (C1.5). C1.2 Proposed Scheme 1.2.1 Procurement The conventional procurement process would involve the local authority commissioning a Consulting Engineering company to develop the detailed design and drawings for construction of this facility. The Consultant would then call for Construction Companies to tender for the work as designed by the Consultant. The completed facility would then be handed over to the Local Authority who would allocate staff for the operation and maintenance and to ensure that all of the environmental parameters are complied with. Currently, the Department of the Environment and Local Government has a policy for procuring wastewater and water treatment facilities by a Public Private Partnership (PPP). This involves the public (represented by the Local Authority) forming a partnership with a private company for the provision of services – in this case wastewater treatment. The main reasoning behind this approach is that the private sector can be better able to handle the risk of operating complex facilities and can generally perform more efficiently and economically. These cost savings are then passed on to the local community by a reduction in water charges. There are several types of PPP structures and the one favoured by the Department of the Environment and Local Government is a Design Build Operate (DBO) approach. This involves a private company designing, building then operating the facility for a fixed period, typically 20 years. The choice of process and the precise arrangement of structures/facilities on the site is left up to the private company. However they must work within rigorous performance standards and environmental constraints as laid out in this document. For the DBO process to work correctly, it is important that the tenderers are not confined too rigidly in their options. To this end several process options and site layouts are identified and described in this document to give an indication of the type of development, which is likely. 1.2.2 Future Loading There is considerable potential for development in the Shanganagh catchment, particularly the Carrickmines/Stepaside area and there is also scope for some infill in existing developed areas. Within Bray, the major scope for imminent development relates to the existing Bray Golf Club lands and GAA lands within the town area. It is also necessary to cater for the small Corke Abbey catchment within Dun Laoghaire/Rathdown and for new development towards Kilmacanogue and Fassaroe. The existing treatment plant at Corke Abbey will be decommissioned and replaced with a small pump station.

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MCOS\088-012-1-1-R023.doc 8 Rev F1

Studies into the development potential of the catchment result in the following estimated loads for treatment by 2020: Shanganagh – 109,500 Population Equivalent (PE), including 6,800 of industry; Bray – 57,900 PE, including 11,200 of industry; Total - 167,400 PE; It is prudent to allow for future development of the catchments beyond the existing development plan considering that the life expectancy of the works is in the order of forty plus years (given mechanical refit). To this end, the ultimate capacity is taken at 200,000 PE, around 20% greater than the 2020 estimation. 1.2.3 Wastewater Process Options The effluent standards that are required under the Urban Wastewater treatment regulations, that is 25 mg/l of BOD5 and 35 mg/l of Suspended Solids, are not particularly onerous and will be satisfied by basic secondary treatment solutions. Hence there are a number of different processes, which would be suitable, and are described below. Conventional Primary Sedimentation & Activated Sludge Primary clarifiers remove a significant amount of solids as the wastewater enters the plant. The wastewater is then aerated and put through secondary clarifiers to remove partially stabilised solids. Conventional Activated Sludge The wastewater is aerated directly after screening and grit removal (no primary settling) and then passes to secondary clarifiers for the removal of partially stabilised solids. Submerged Biological Aerated Filter (SBAF) Primary clarifiers remove a significant amount of solids before the SBAF unit. The SBAF unit contains a media upon which a biomass grows to consume the biological contaminants. Oxygen is supplied to the biomass to sustain an aerobic type growth. Sequencing Batch Reactor (SBR) This is similar in principle to activated sludge although all functions are accommodated by a single tank (reactor). Wastewater is introduced then aerated in the reactor and then left to settle for a period. Partially stabilised solids are removed from the bottom while clear supernatant is removed from the surface. This process results in a relatively low tankage site option, refer to Figure C1.2 and C1.3. Primary Sedimentation and SBR This is the similar to the option described above with the inclusion of primary sedimentation and anaerobic digestion to reduce energy demand. This process results in a relatively high tankage site option, refer to Figure C1.1 and C1.3.

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MCOS\088-012-1-1-R023.doc 9 Rev F1

1.2.4 Sludge treatment process options Anaerobic Digestion Primary and secondary sludge is digested in an enclosed tank in the anaerobic digestion process. Methane is produced which is collected and used as an energy source to supply heat and electricity for the wastewater treatment plant operation. Sludge Hydrolysis Sludge is heated and pressurised to destroy cell structures to produce a substance that is more readily digestible. This process significantly increases energy recovery and process stability. Sludge Drying Dewatered sludge is produced by thermal drying in a rotating drum by hot air. The product is a pathogen-free granule with a low water content. 1.2.5 Design Issues As with any major civil engineering project there are constraints on what can be achieved. In order to reduce the visual impact of the tanks, it would be desirable to design deep tanks (to reduce surface area) and sink them in the ground. Unfortunately, the site is quite low lying and the soils are relatively permeable so it would not be economically feasible to construct large tanks below the high tide level, as significant dewatering would be required. Hence, the high tide level sets the practical foundation limit for large tanks. The heights and plan areas of the plant buildings have been developed by allowing for typical machinery that would be used in this type of facility. It will be necessary to lower the existing ground-lines marginally to reduce the roof height to the limits shown, refer to figure C1.3 for indicative roof levels. The existing pump station and outfall will be retained and incorporated into the future works. 1.2.6 Planning Expansion of the site would be required to accommodate a secondary treatment plant for the combined Bray and Shanganagh Catchments (Fig C1.4). Construction within the existing confines of the site would be achievable but at significantly increased cost with a reduction in flexibility of the site use and potential treatment process options. Expansion of the site is achievable only to the south, as the open space to the north (across the Shanganagh River) is not suitable in terms of river impact and potential impact on Bayview Estate. The expansion of the site to the east would involve impinging on open space lands and the linear walkway between works and shoreline. The existing site is currently operating as a wastewater disposal works and the proposed upgrading of the plant would be consistent with this existing use and is an objective of the 1999 Development Plan. In the Development Plan, the area around the site has land-use zoning Objectives A and F, which is “to provide and/or improve residential amenity” and "to preserve and provide for open space and recreational amenities respectively, refer to Figure C1.4. Public services, including wastewater treatment works are “permitted in principle” within the residential zoning objective, while it is only "open for consideration" in the open space objective. The classification “open for consideration” in the zoning objective is not considered a material contravention of the

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