COURTOWN WASTEWATER TREATMENT PLANT EXTENSION

Transcription

1 COMHAIRLE CHONTAE LOCH GARMAN WEXFORD COUNTY COUNCIL County Hall, Wexford Tel: (053)65000 Fax: (053) COURTOWN WASTEWATER TREATMENT PLANT EXTENSION ENVIRONMENTAL IMPACT STATEMENT FOR THE EXTENSION OF THE EXISTING COURTOWN This space is designed to hold PLANT WASTEWATER TREATMENT Co ns en to f c Fo op r i yr ns ig pe ht ct ow ion ne pu r r rp eq os ui es re o d nl fo y. ra ny ot he ru se. the main message of your flyer. Niall McGuigan Director of Services Wexford County Council County Hall Wexford Co. Wexford Ryan Hanley consulting engineers This is a good place to add information you want to call attention to. December 2005 EPA Export :22:46:02

2 Courtown Wastewater Treatment Plant Extension Environmental Impact Statement Table of Contents 1 PREAMBLE APPROVAL PROCESS EIS SUB CONSULTANTS STRUCTURE CONSULTATION PROJECT PROCUREMENT COURTOWN DRAINAGE SCHEME EIS, DESCRIPTION OF THE PROPOSED DEVELOPMENT GENERAL DESCRIPTION AND SCOPE OF THE PROJECT DESCRIPTION OF THE PROPOSED WORKS CONSTRUCTION OF THE PROJECT OPERATION OF THE PROJECT ALTERNATIVES CONSIDERED ASSOCIATED DEVELOPMENTS DESCRIPTION OF THE EXISTING ENVIRONMENT, IMPACTS ON THE EXISTING ENVIRONMENT AND MITIGATION MEASURES HUMAN BEINGS ECOLOGY SOILS WATER QUALITY AIR QUALITY ODOUR AIR QUALITY - NOISE CLIMATE LANDSCAPE CHARACTER AND VISUAL IMPACTS CULTURAL HERITAGE MATERIAL ASSETS INTERACTION OF FACTORS...75 APPENDIX A DRAWINGS...A APPENDIX B ECOLOGY... B APPENDIX C WATER...C APPENDIX D AIR QUALITY ODOUR...D APPENDIX E AIR QUALITY NOISE... E APPENDIX F LANDSCAPE CHARACTER AND VISUAL IMPACTS... F APPENDIX G - CULTURAL HERITAGE...G APPENDIX H OPEN DAY CONSULTATION...H APPENDIX I MARINE STUDIES AT COURTOWN... I APPENDIX J NEARFIELD DILUTION ASSESSMENT OF MARINE OUTFALL AT COURTOWN...J Ryan Hanley consulting engineers i December 2005 EPA Export :22:46:02

3 1 PREAMBLE 1.1 APPROVAL PROCESS The Environmental Impact Statement for the extension of the Courtown Wastewater Treatment Plant (WWTP) to treat sewage from Gorey Town and to fulfil the role of the sludge satellite centre for the Gorey area has been prepared for Wexford County Council in accordance with the provisions of: (a) The European Communities (Environmental Impact Assessment) Regulations 1989 to 2001 (S.I. No. 538 of 2001) referred to as the "Environmental Impact Assessment Regulations". These Regulations provide for the incorporation into Irish law, in respect of relevant developments other than motorways, of EU Directive on the assessment of the effects of certain public and private projects on the environment; Article 24 of the Environmental Impact Assessment Regulations specifies the developments which are subject to an Environmental Impact Assessment. This includes by virtue of 11(d) of Part II of the First Schedule of the Regulations the following: Wastewater Treatment Plants with a capacity greater than 10,000 population equivalent. The EU Directive on Environmental Impact Assessment refers to the duties of the "Developer" and the "Competent Authority". For the purposes of this project, the "Developer" is Wexford County Council and the "Competent Authority" is An Bord Pleanála. and (b) Planning and Development Regulations, (S.I. No. 600 of 2001). The proposed development is described under Part (d), the construction or erection of pumping stations, treatment works, holding tanks or outfall facilities for waste water or storm water The prescribed classes of development requiring an Environmental Impact Assessment are set out in Schedule 5 of the Planning and Development Regulations, (S.I. No. 600 of 2001). The following are relevant extracts from SCHEDULE 5: Part 2, 11 states: (c) (d) Wastewater treatment plants with a capacity greater than 10,000 population equivalent as defined in Article 2, point (6), of Directive 91/271/EEC not included in Part 1 of this Schedule. Sludge-deposition sites where the expected annual deposition is 5,000 tonnes of sludge (wet). Part 2, 13. (a) states: Any change or extension of development which would: Ryan Hanley consulting engineers 1 December 2005 EPA Export :22:46:02

4 (i) result in the development being of a class listed in Part 1 or paragraphs 1 to 12 of Part 2 of this Schedule, and (ii) result in an increase in size greater than - 25 per cent, or - an amount equal to 50 per cent of the appropriate threshold, whichever is the greater. The existing Courtown WWTP provides secondary treatment to cater for a design population equivalent (PE) of 12,000 PE BOD and 15,000PE Hydraulic. It was designed to provide for a future population equivalent of 16,000 PE BOD and 20,000PE Hydraulic. The treated effluent discharges through an outfall pipeline from the plant via a long-sea outfall to the Irish Sea east of Breanoge Head in Courtown Harbour. The site includes preliminary units, aeration tanks, settling tanks (clarifiers), a sludge holding tank, sludge dewatering plant, sludge storage tank and associated buildings, housings and site works. The Courtown WWTP extension will result in an increase in the footprint of the existing plant. Additional tanks, building area, equipment housing, paved area and associated works will be required. The proposed works will be contained within the boundary of the existing Courtown WWTP site. The extended plant will include: an extension to the existing wastewater treatment plant to cater for an equivalent population increase from 12,000 to 35,000 persons (Phase I) and from 35,000 to 45,000 persons (Phase II) a sludge acceptance facility to cater for imported sludges for an equivalent population of 15,000 persons (Approximately 32,000 tonnes of wet sludge per annum) and sludge dewatering and storage facilities for an equivalent population of 60,000 persons The project, therefore, is subject to an Environmental Impact Assessment under the above Regulations. 1.2 EIS SUB CONSULTANTS Ryan Hanley consulting engineers prepared this Environmental Impact Statement with assistance from a number of specialists as follows: Odour Monitoring Ireland carried out an Environmental Impact Study on the odour aspects of air quality. The study included a baseline study of the existing WWTP and odour modelling of the proposed layout. Biospheric Engineering carried out an Environmental Impact Study on the noise aspects of air quality. The study included a baseline study of the existing WWTP. Aqua-Fact International Services Ltd carried out an Environmental Impact Study on flora and fauna. Mitchell and Associates, Landscape Architects carried out a landscape character and visual impacts study. Hydro Environmental Ltd carried out the Marine Outfall Study. Byrne Mullins & Associates, Archaeologist carried out an Environmental Impact Study on Archaeology, Architectural and Cultural Heritage. Ryan Hanley consulting engineers 2 December 2005 EPA Export :22:46:02

5 1.3 STRUCTURE The EIS contains: 1. An assessment and baseline study of the existing environment at the WWTP and along the outfall pipeline with particular reference to flora, fauna, water quality, effluent discharge quality and amenity uses. 2. A technical description of the proposed works including its design capacity and quality of effluent discharged at the outfall and alternatives considered. 3. Beneficial and adverse impacts on the existing development of the construction and subsequent operation of the upgraded WWTP including mitigation measures to be incorporated into the design to mitigate adverse impacts. In preparing the Environmental Impact Statements reference was made to the "Guidelines on the Information to be contained in Environmental Impact Statements", Environmental Protection Agency 2002 and "Advice Notes on Current Practice (in the preparation of Environmental Impact Statements)", Environmental Protection Agency, The statement is prepared in accordance with the "Grouped Format Structure" whereby each of the environmental factors is considered as a single topic. Each of the environmental factors is considered in terms of (a) the existing environment (b) the impacts of the project and (c) mitigation measures. Table 1-1 shows where each of the topics set out in the Second Schedule of the Environmental Impact Assessment Regulations is dealt with in the report. TOPIC RELEVANT SECTION OF REPORT Human Beings 3.1 COMMENT Flora & Fauna 3.2 Included under Ecology Soil 3.3 Deals with Soils and Geology Water 3.4 Deals with Freshwater and Marine water. Air Quality - Odour 3.5 Deals with the Odour element of Air Quality Air Quality - Noise 3.6 Deals with the Noise element of Air Quality Climate 3.7 The Landscape 3.8 Cultural Heritage 3.9 Material Assets 3.10 The Interaction of the Foregoing 3.11 Deals with Landscape Character and Visual Impacts Deals with Archaeology, Architectural & Cultural Heritage Table 1-1 Topic Layout Ryan Hanley consulting engineers 3 December 2005 EPA Export :22:46:02

6 The reports prepared by the various specialists referred to in Section 1.2 are included in Appendices B to G. 1.4 CONSULTATION An Open Day was held in the Taravie Hotel on Wednesday, 30th of November 2005 from 11am to 6.30pm to inform local residents and interested parties of the proposals and also to take note of any public queries or comments. Notice of the meeting was conveyed through notices in local newspapers, The Gorey Echo and The Gorey Guardian. Details of the open day were broadcast on the local radio station South East Radio. In addition notices were hung at local authority offices and at a number of public locations in Courtown. Two display boards were erected showing the location of the WWTP site and outfall pipeline, layouts of the existing Courtown WWTP and future indicative layout. Attendees were provided with an information leaflet outlining the proposed works. A comment card was also provided to record details of those attending and to record comments relating to the project under consideration. Representatives from Wexford County Council, Ryan Hanley Consulting Engineers and JB Barry & Partners were present throughout the day to outline the proposed project and to deal with queries. Approximately persons visited the display during the day. The main areas of interest were the extent of the proposed works and receiving water quality and the reactions to the proposals were predominantly positive. A copy of the information leaflet, comment card, public notice, newspaper notice and a summary of comments recorded are in included in Appendix H. 1.5 PROJECT PROCUREMENT The proposed development may be procured through a Design, Build and Operate (DBO) contract. This would allow tenderers to design a plant with the most economic whole life cost. Thus, alternative designs and processes may be permitted at the detail design stage of the project provided that they are within the constraints set out in this EIS and any other requirements by Wexford County Council. These design options would ensure that Wexford County Council is ultimately provided with the most economical plant, in both capital and operational cost terms, while fully meeting the required operating and environmental standards. The use of DBO procurement encourages innovative design with lower whole life costs. Ryan Hanley consulting engineers 4 December 2005 EPA Export :22:46:02

7 1.6 COURTOWN DRAINAGE SCHEME EIS, 1996 An EIS was prepared for the Courtown Drainage Scheme in The scheme included the upgrading and extension of the sewerage network, the construction of a new wastewater treatment plant (Courtown WWTP) and an outfall pipeline to discharge treated effluent to the sea. As part of the EIS, specialist studies were carried out by sub-consultants as follows: MCS International carried out the Hydrographic Marine Survey. Fieldwork for the survey was carried out by Hydrographic Surveys Ltd. Irish Drilling Ltd, as subcontractor to MCS International, carried out sub-sea site investigation along the route of the proposed outfall pipeline and ground investigation along the pipeline routes. The Environmental Services Division of Forbairt carried out an Environmental Impact Study on air including noise and odour aspects. Aqua-Fact International Services Ltd carried out an Environmental Impact Study on ecology and water. Brady Shipman Martin, Planning Consultants, Architects and Landscape Architects carried out an Environmental Impact Study on landscape character and visual impacts. Markus Casey, Archaeologist carried out an Environmental Impact Study on Archaeology. These studies have been reviewed as part of this current EIS. The extensive hydrographic marine survey and modelling study carried out for the 1996 EIS by MCS International have been used as part of the current water quality study. Ryan Hanley consulting engineers 5 December 2005 EPA Export :22:46:03

8 2 DESCRIPTION OF THE PROPOSED DEVELOPMENT 2.1 GENERAL DESCRIPTION AND SCOPE OF THE PROJECT Introduction Courtown is a seaside tourist resort, located in the north east of County Wexford. It is situated approximately 5km south east of Gorey and is on the coastal road from Wexford (R742). Fig 2.1 shows the location of the Courtown WWTP. The recently completed Courtown Drainage Scheme included the upgrading and extension of the sewerage network and the construction of the new Courtown Wastewater Treatment Plant. The scheme included: Wastewater Treatment Plant to provide secondary treatment to cater for a design population equivalent (PE) of 12,000 PE BOD and 15,000PE Hydraulic and a future population equivalent of 16,000 PE BOD and 20,000PE Hydraulic. Outfall pipeline from the WWTP to discharge treated effluent via a long-sea outfall to the Irish Sea east of Breanoge Head. The Courtown WWTP is situated on a 3.34hA site on the Ballinatray Road. It was commissioned in August The existing process at the plant is described in Section The proposed development consists of the extension of the existing wastewater treatment plant (WWTP) at Courtown to treat sewage from Gorey Town, which will be pumped to the site from the existing Gorey Town sewage treatment works. This has been recommended by the Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision 4, The proposed development also provides for the Courtown WWTP assuming the role of the sludge satellite centre for the Gorey area. The requirements of the sludge satellite centre for the Gorey area are set out in the Wexford Sludge Management Study (Draft Final Report), T.J. O Connor & Associates, March This EIS examines the impacts associated with the construction and operation of the proposed extension to the existing Courtown WWTP and the subsequent impact of the treated effluent discharge of the water quality in Courtown Harbour including the bathing areas. Ryan Hanley consulting engineers 6 December 2005 EPA Export :22:46:03

9 Figure 2-1 Courtown WWTP Location Map Ryan Hanley consulting engineers 7 December 2005 EPA Export :22:46:03

10 2.1.2 Project Scope It is proposed to extend the wastewater treatment plant at Courtown to provide additional capacity to treat all foul loads arising at Gorey and to cater for the sludge dewatering requirements for the Gorey Sludge Satellite Area as set out in the Wexford Sludge Management Study (Draft Final Report), March The extended WWTP at Courtown will be designed to treat an average of 8,100 m³/day of wastewater as set out in Table 2-1. The extension of the WWTP will be carried out in two phases. In Phase I the plant capacity will be increased to 35,000PE, which is equivalent to an average of 6,300 m³/day of wastewater. The Phase I works will be designed to facilitate the future increase of the plant and may include tanks and equipment sized for the Phase II load. Phase II will increase the WWTP capacity to 45,000PE (8,100 m³/day) to meet the long-term needs of the Courtown and Gorey catchment areas. Source of plant loadings Courtown Load (Phase 1 of Courtown MDS) Future Courtown Environs Load Gorey Load Phase I subtotal Additional population growth projection in Gorey Total Load to Extended WWTP (Phase I & II) Load quantification PE allowance (Hydraulic) PE allowance (BOD) Total BOD Average Daily Flow to WWTP (DWF) Peak flow (3DWF) Peak flow 15,000 PE 5,000 PE 15,000 PE 35,000 PE 10,000 PE 45,000 PE 180 l/person/day 60 g/person/day 2700 kg/day 8,100 m³/day 3 DWF m³/hr 281 l/s Table 2-1 Wastewater flows to extended Courtown WWTP The plant will have sludge reception facilities to accept imported sludges from a population equivalent (PE) of 15,000 from treatment plants in the Gorey area. Sludge thickening and dewatering facilities will be provided to achieve a sludge with a dry solids content of 20% for all sludges on site i.e. for a 60,000 PE. Dewatered sludge will be transported to the Wexford Sludge Hub at the Wexford WWTW. The above elements define the scope of the project covered by this Environmental Impact Statement. Ryan Hanley consulting engineers 8 December 2005 EPA Export :22:46:03

11 2.1.3 Legislation & Policies The project is constrained by existing legislation and policies as follows: UWWT Directive The Urban Waste Water Treatment Regulations, 2001 give effect to the EC Directive 91/271/EEC concerning waste water treatment. The regulations set out the requirements of a sanitary authority to provide treatment plants and the effluent quality required. Under the legislation, secondary treatment or an equivalent treatment in respect of all discharges from agglomerations with a population equivalent of more than 10,000 is the basic requirement for all discharges to coastal waters. More stringent standards are prescribed for discharges into sensitive areas or into the relevant catchment areas of sensitive areas where the discharges contribute to the pollution of these areas. Courtown Harbour is not listed as a sensitive area in the regulations. The existing Courtown WWTP provides secondary treatment capacity for a population equivalent of more than 10,000. Similar standard treatment will be required for the higher loadings on the proposed extended plant. Tourism Policy The Wexford Development Plan has the stated aim of facilitating the strengthening and diversification of the tourism roles of traditional seaside resorts including Courtown. This includes the promotion of linkages to their rural hinterlands and the provision of a range of outdoor and wet weather facilities. The development plan also has the stated aim of maintaining the Blue Flag status at the beach in Courtown. Bathing Water Directive The Quality Of Bathing Waters Regulations, 1992 (S.I. No. 155/1992) sets the Irish National Limit values which relate to the quality of bathing waters standards including mandatory values for faecal coliform and faecal streptococci concentrations. The National Limits are based on the EC Guideline Values and EC Mandatory Values as set out in Directive No. 76/160/EEC concerning the quality of bathing water. The Blue Flag is a well-recognised, well respected eco-label, awarded to beaches and marinas with excellent environmental management. The Blue Flag beach standard in regard to bacterial impact requires that the EU Directive Guideline limit of 100 No./100ml faecal coliforms at 80% compliance and 100 No./100ml faecal streptococci at 90% compliance is met. An Taisce is the national operator for the International Blue Flag Campaign in Ireland. The Blue Flag bathing season runs from June to August. The general practice in establishing the effluent treatment standard is to comply with the Blue Flag Beach water quality standards at recognised bathing areas. In the case of Courtown Harbour the principal Bathing area beaches are located immediately to the north and the south of the Harbour inlet. These bathing beaches are located 550m west northwest and 350m west of the outfall point. Recommendations from Gorey Main Drainage Stage 2 Preliminary Report The Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision 4, 2001 recommends the provision of a treatment works with a Population Equivalent of 15,000 to serve the needs of Gorey Town and its environs until the year Subsequent to the Ryan Hanley consulting engineers 9 December 2005 EPA Export :22:46:03

12 issue of that report and following a review of recent population increases in Gorey and a review of the projected population growth, Wexford County Council have revised the projected 2025 population for Gorey from 15,000 to 25,000. It is proposed that the plant be upsized in two phases with Phase I to cater for the Gorey design population of 15,000 and Phase II to cater for the most recent projected population of 25,000 for Gorey. The Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision 4, 2001 concludes that effluent disposal to the Irish Sea at Courtown is the only environmentally sound solution available for the long term. The report considers the options of: Providing new wastewater treatment facilities at Gorey and pumping the effluent to the new sea outfall at Courtown (Option 1). Pumping the raw untreated sewage to the Courtown WWTP, increase the plants capacity and discharge the treated effluent via the long sea outfall (Option 2). It recommends that the sewage treatment requirements of Gorey be located in Courtown WWTP (Option 2) as it has the most economic Whole Life Cost (NPV) of the two suitable alternatives that were examined in detail. County Sludge Plan The Wexford Sludge Management Study (Draft Final Report), T.J. O Connor & Associates, March 2001 designated a number of satellite centres which would export sludges to the designated hub-centre in the Wexford WWTW. The purpose of these satellites is to minimise the sludge transportation costs and the road distances travelled and to provide centralised sludge dewatering facility for sludges arising from a number of works in a particular locality. In that report, the Gorey WWTW was designated as the Sludge Satellite Number 2. The recommendations of the Gorey Main Drainage, Stage 2 Preliminary Report include the treatment of all sewage from Gorey at an extended treatment works in Courtown. As a result of this recommendation, the Courtown WWTP will assume the role of the sludge satellite centre for the Gorey area. 2.2 DESCRIPTION OF THE PROPOSED WORKS Introduction The proposed development is intended to provide additional sewage treatment capacity to cater for wastewater from Gorey Town. The existing STW at Gorey is an extended aeration activated sludge plant which was commissioned in The original design population for the works was 4,500PE. The effluent discharges to the Banoge River. The Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision states that flow from the treatment works (1 x ultimate DWF) would have little more than 2:1 dilution available at certain times of the year. The report concludes that the Banoge must be ruled out of consideration to receive effluent from the increased capacity treatment works (at Gorey). Ryan Hanley consulting engineers 10 December 2005 EPA Export :22:46:03

13 The extended works at Courtown WWTP will assume the role of the sludge satellite centre for the Gorey area as set out in the Wexford Sludge Management Study. The plant will have a higher sludge load due to the increase in the wastewater load discharging to the plant and also due to the imported sludges from the Gorey satellite area that will be transported to the site for dewatering. To accommodate these loads, sludge reception facilities will be required for the imported sludges and greater capacity will be required for sludge thickening, dewatering and sludge storage for all sludges on site. The extent and location of the works can be seen on reference to the following drawings in Appendix A: Drawing No. 1757/001 Site Location Drawing No. 1757/002 - Existing Site Layout Existing Process Description The Courtown Wastewater Treatment Plant is located 250m north of Ballinatray Bridge on the Ballinatray Road as shown on Drawing No. 1757/001 (Appendix A). The works are situated on a site of total area 3.33ha. A layout for the existing wastewater treatment plant is shown on Drawing No. 1757/002 (Appendix A). An extract of that drawing is shown in Figure 2-2. The main treatment process flow path is from preliminary units to aeration tank to settling tank (clarifiers) to final effluent measurement flume to outfall. Sludge settling in the hoppers of the settling tanks is returned on a continuous basis to the aeration tanks so as to maintain the biomass in the tanks, a critical part of the extended aeration process. In addition sludge is periodically wasted to the sludge holding tank via the surplus sludge pumps. Sludge is then pumped to the sludge dewatering plant. Supernatant return pumps pump filtrate generated from the sludge dewatering process back to the inlet of the treatment process. Input Raw Sewage Outputs Treated Effluent Screenings (Washed and Compacted) Grit (Washed) Dewatered/Thickened Sludge Ryan Hanley consulting engineers 11 December 2005 EPA Export :22:46:03

14 Figure 2-2 Extract from Drawing 1757/002 (Appendix A) showing the layout of the existing Courtown WWTP site. The site contains the following structures: Single storey control building faced in forticrete blockwork with a pitched slate roof Single-storey sludge dewatering plant and workshop building faced in forticrete blockwork with a pitch slate roof Sludge thickening tank of concrete construction Thickened sludge holding tank of concrete construction A flow splitting chamber 4No. concrete aeration tanks 2No. concrete settling tanks Effluent measurement and sampling chamber. Site lighting and fencing The treated effluent from the plant discharges to a pipeline from the WWTP site and to the sea via a long sea outfall located 330m immediately east of Breanoge Head in Courtown Harbour. The existing WWTP is designed to treat the influent from Phase I of the Courtown Drainage Scheme. Ryan Hanley consulting engineers 12 December 2005 EPA Export :22:46:03

15 2.2.3 Proposed Wastewater Treatment Plant Overview The scheme will include the extension of the Courtown Wastewater Treatment Plant to treat the future Courtown Drainage Scheme influent (20,000PE) and the future Gorey Main Drainage influent (25,000PE). The design loadings for the existing and proposed wastewater treatment plant are shown in Table 2-2. A seasonal variation of the load from Courtown Riverchapel catchment is anticipated due to the seasonal nature of visitors to that area. The design loadings for the Courtown Riverchapel catchment are based on predicted summer loadings. Based on inlet flow data to the Courtown WWTP and water meter data, the current winter load is estimated at 3,300PE. Parameter Existing WWTP Design Loading Extended Plant Design Loading (Courtown & Gorey Loads) Units Equivalent Population (BOD) 12,000 45,000 persons Equivalent Population (Hydraulic) 15,000 45,000 persons Total BOD 720 2,700 kg/day Total DWF 3,750 8,100 m³/day Peak Flow ,012.5 m³/hour Peak Flow l/sec Table Courtown Wastewater Treatment Plant Existing & Proposed Design Loadings The proposed raw sewage from Gorey will be pumped from the site of the existing Gorey STW, discharging to the inlet chamber of the Courtown WWTP. The maximum pumping rate from Gorey will be equivalent to three times the dry weather flow (3 DWF). The existing flow regime to the plant from its existing catchment (Courtown-Riverchapel) will remain unaltered. The loads from that catchment will increase with population increases and collection network extensions as provided for in the Courtown Drainage Scheme (Phase I and Phase II). Plant Design The detailed design of the expanded wastewater treatment plant, including the sludge reception and treatment facilities, may be carried out by the successful tenderer in a Design Build & Operate (DBO) procurement process. The design of the works will be for the specified hydraulic and organic loadings as set out in Section This is based on a design period of 20 years extending from 2005 to The final effluent standards to be achieved are: Biochemical Oxygen Demand (BOD5) at 95-percentile Chemical Oxygen Demand (COD) at 95-percentile Total Suspended Solid (TSS) at 95-percentile Faecal Coliforms (FC) = 25mg/l = 125mg/l = 35mg/l = 1 x 10 6 No./100ml Ryan Hanley consulting engineers 13 December 2005 EPA Export :22:46:03

16 Figure 2-3 Extract from Drawing No. 1757/003 Rev C, Appendix A showing an indicative site layout (proposed structures are shown red) An indicative site layout is shown in Figure 2-3 (see Drawing No. 1757/003 Rev C, Appendix A for a larger scale drawing). The footprint of the WWTP will expand, but will be accommodated within the existing 3.3hA site. The layout of the wastewater treatment plant may vary from the indicative layout, however, the scale of the development in terms of the footprint area will be of the order indicated in the outline design and the structure heights will not exceed the heights indicated. This will allow the flexibility of designing, building and operating the most economic wastewater treatment plant within the environmental constraints of this EIS and any other requirements set out by Wexford County Council. Additional structures of the scale anticipated to meet the plant design requirements and based on the indicative site layout are described below. The layout of the final design may vary, however, the scale of the development will be similar to that of the indicative site layout. The existing process tanks may be modified. Additional Wastewater Treatment Capacity It is anticipated that a new inlet works with a top level up to 31.5mOD will replace the existing inlet works to cater for the increased flow discharging to the plant. The new inlet works will be located north west of the existing inlet works. The treatment process may be modified from the existing extended aeration process. It is anticipated that new process tanks will be required as follows: 1. Additional process tanks to the north west of the existing aeration tanks. 2. Additional process tanks beside (to the north east of) the existing aeration tanks. Ryan Hanley consulting engineers 14 December 2005 EPA Export :22:46:03

17 3. Additional process tanks beside (to the north east of) the existing final settlement tanks. The above tanks may serve as primary settlement, anoxic, aeration and final settlement and/or filtration tanks respectively, however, depending on the process type employed, the quantity, size and use of the tanks may vary. Additional Sludge Handling and Treatment Capacity The extended works will have a higher sludge load due to the increase in the load discharging to the plant and also due to the imported sludges that will be transported to the site for dewatering. To accommodate these loads, sludge reception facilities will be required for the imported sludges and greater capacity will be required for sludge thickening, sludge dewatering and sludge storage for all sludges on site. To fulfil its role as a sludge satellite centre, the Courtown WWTP will be provided with the following plant and facilities for sludge reception and treatment as set out in the Sludge Management Study: Screening of sludge imports and associated skips, water supply etc. Storage for 7 days of sludge arising in the satellite area over and above any storage provided for sludges arising in the satellite works itself. Mechanical thickening for imported sludges possibly in conjunction with waste activated sludge from main treatment streams Dewatering facilities (duty/standby) to take sludges to at least 20% DS. At least 2 tanker-unloading bays with a tanker turning circle. It is anticipated that additional sludge tanks in the western corner of the site will replace or augment the existing sludge thickening tank. These tanks will provide for sludge blending and sludge dewatering. The capacity of the tanks provides for storage of the 7 days of sludge arising in the satellite area as set out in the Sludge Management Study. In addition, a sludge reception area for tankers to unload the imported sludges and incorporating sludge holding and screening facilities will be provided. An extension to the existing dewatering building and the provision of a new dewatered sludge storage building of plan area up to 300m² adjacent to the dewatering building is anticipated to deal with the higher sludge throughput at the plant. Ancillary Items and Site Works Additional plant and site works will be required to cater for the additional wastewater and sludge treatment plant proposed. They include: Reconfiguring of existing and addition of new underground pipe work, ducts, chambers and pumping stations to suit the new site layout. Air handling units to minimise odour nuisance to acceptable levels. Smaller structures, such as kiosks to enclose telemetry and control equipment, and pump enclosures to reduce noise emissions, will be required throughout the site. The existing circulation road and hard standing areas within the treatment plant site will be extended to provide access to the various units. Ryan Hanley consulting engineers 15 December 2005 EPA Export :22:46:03

18 The existing perimeter mounding and landscaping will be supplemented by additional landscaping works as set out in the Landscape section of this report. Anti-intruder palisade fencing finished in green plastic coated steel currently surrounds the treatment works. Sections of this fence line will be relocated to provide a greater area within the WWTP site to accommodate the proposed units. The existing 1350mm high black plastic coated chain link fence along the boundary of the land acquired for the wastewater treatment plant site will remain. A number of additional lighting columns will be erected at the treatment works site. Outfall Pipeline The existing outfall pipeline will require additional hydraulic capacity to cater for the peak flows from the extended Courtown WWTP. This can be achieved through the provision of a parallel pipeline along part of the existing outfall and/or by the provision of pumping of the effluent from the Courtown WWTP. The hydraulic capacity of the sea outfall and the dilutions achieved by the outfall diffusers are adequate, without any modifications, for the new peak flows. Traffic to/from Courtown WWTP Traffic levels associated with the proposed works will consist of operating staff, visitors and both inward and outward sludge. The staff numbers on site will not increase significantly with an additional 1 2 staff anticipated. The number of visitors (including deliveries) to the site will increase slightly to an estimated level of visitors/week. There will be on average, 7 tankers delivering sludge from the Gorey sludge satellite area to the site each weekday (Monday to Friday). The sludge will be transported to site in sealed tankers of capacity up to 20m³. The dewatered sludge will be collected on site in a sealed skip or within an enclosed building. Transport of dewatered sludge from the works will be in a sealed skip. It will involve approximately trips/week when the plant is running at full capacity. 2.3 CONSTRUCTION OF THE PROJECT Introduction Construction of the extension to the Courtown Wastewater Treatment Plant, will involve a small-scale civil engineering project of 6-9 months duration Land Use Requirement The construction stage of the works will involve a land use requirement separate from that required for the permanent works: The Contractor appointed to carry out the construction works will be required to set up a site compound in the general vicinity of the wastewater treatment plant site for purpose of parking, offices, canteen and storage of materials. Ryan Hanley consulting engineers 16 December 2005 EPA Export :22:46:03

19 Construction of the works will result in surplus soil from excavation for pipelines, tanks, etc. The Contractor will be responsible for making arrangements for disposal of such surplus material in accordance with relevant legislation Proposed Construction Works At the commencement of the construction of the works the Contractor will prepare a programme for the execution of the works to take account of: Time allowed under the contract to complete the works. Any constraints on the programme under the terms of the Contract. Time of year at which works commences. The major temporary features associated with the construction of the works including track excavators, dewatering pumps, dump trucks, crane, stock pile, site compound, scaffolding and formwork. Significant Effects The construction of the works will have a number of temporary impacts: Construction plant, including excavators, rock breakers, dewatering pumps will result in increased noise levels. There will be increased temporary traffic flows due to the construction staff travelling to/from the site and from delivery of materials to the site. The disposal of surplus materials off site will also increase the traffic flow. Ground reductions associated with a development of this kind may uncover and disturb hitherto unrecorded sub-surface features, deposits, structures and finds of archaeological interest and potential. Environmental Protection Measures Mitigation measures to deal with the various construction impacts are given further consideration in Section 3 of this report under the appropriate topics. In addition, there are various statutes and regulations of relevance to the construction stage which will minimize the impacts under each of the above e.g. Safety, Health and Welfare at Work Act 1989 and various statutory instruments made under the Act. 2.4 OPERATION OF THE PROJECT The requirements of the project are set out above in the Section The operation of the plant will be in accordance with the Performance Management System (PMS) which has been developed by the Water Services National Training Group (WSNTG). It sets out a consistent approach to dealing with all relevant performance management issues at a wastewater treatment plant. The Performance Management System documentation defines the roles of the Plant Operator and the Caretaker and sets out templates in relation to the operating of the plant and reporting procedures to be employed. Ryan Hanley consulting engineers 17 December 2005 EPA Export :22:46:03

20 A Plant Operator will be responsible for the operation of the project on a day-to-day basis. It is envisaged that the Plant Operator will spend between 50 and 100% of his/her working week engaged on the project with most of the time spent at the wastewater treatment plant. The project will include a SCADA system for the monitoring and control of the wastewater treatment process and monitoring of energy consumption for the overall project. The Plant Operator will be assisted by a number of general operatives (1 to 3) for the purpose of carrying out routine maintenance work, for example, washing down of channels, maintenance of landscaped areas. There will also be occasional visits to the plant by Local Authority personnel, fitters, electricians, suppliers and specialist maintenance personnel. All such works will generally be carried out during normal working hours (8:00 am to 6:00 pm Monday to Friday). There may on occasion be visits to the plant outside of these hours in case of breakdown of the plant. Imported sludges will be transported to site in sealed tankers of capacity up to 20m³. On average this will result in 7 tankers per weekday. The tankers will transport sludge from wastewater treatment plants in the Gorey Satellite Centre area as outlined in the Sludge Management Plan for Wexford County Council, Draft, April 2001, TJ O Connor & Associates. Dewatered or thickened sludge will be transported off the site in 10m³ skips. This will result in a requirement of tankers per week at the design load. This is equivalent to just over 3 trips per day during a normal working week of Monday to Friday. In addition compacted washed screenings and grit will be transported off site. The dewatered sludge will be transported to the Wexford County Sludge Hub Centre at Wexford WWTW for further treatment and disposal. 2.5 ALTERNATIVES CONSIDERED Introduction This section deals with alternative locations considered for the site of the wastewater treatment works and outfall pipeline for the Gorey Main Drainage Scheme. A synopsis of the site selection process for the existing Courtown WWTP site is also included. The Courtown WWTP site selection is extracted from the Environmental Impact Statement for the Courtown Drainage Scheme (1996) Siting of Treatment Process for Gorey The existing STW at Gorey is an extended aeration activated sludge plant which was commissioned in The original design population for the works was 4,500PE. The effluent discharges to the Banoge River. Flow from the treatment works (1 x ultimate DWF) would have little more than 2:1 dilution available at certain times of the year. The Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision concludes that discharge of treated effluent to either the Owenavorragh River or the Banoge River is not feasible due to lack of assimilative capacity. It also states that effluent disposal to the Irish Sea at Courtown is the only environmentally sound solution available for the long term. Ryan Hanley consulting engineers 18 December 2005 EPA Export :22:46:03

21 2.5.3 Options for Location of Wastewater Treatment Process Two possible alternatives for the proposed Wastewater Treatment Works siting were considered in the Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision as follows: Option 1 Option 2 Construct a new Conventional Activated Sludge (CAS) plant on the existing wastewater treatment site at Gorey and pump the treated effluent to the sea outfall in the Courtown/Riverchapel MDS. Pump the raw untreated sewage to the Courtown Treatment Plant, increase the capacity of this plant and discharge the treated effluent via the long sea outfall. Both sites have existing sewage treatment facilities. The advantages and disadvantages of both options are described in the Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision as follows: Option 1 - Wastewater Treatment at Gorey Effluent Pumped to Courtown Advantages Located on the site of the existing (Gorey) works Benefit/reuse from plant and equipment installed under interim contract Any negative impact to Banoge/Owenavorragh river system is removed. Disadvantages More expensive whole life cost (than option 2) Two plants to be operated (interim and final) in addition to Courtown Table 2-3 Advantages and Disadvantages of Option 1 (Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision ) Option 2 - Wastewater Treatment at Courtown Advantages Any negative impact to Banoge/Owenavorragh river system is removed. Balancing of the severe seasonal effects of the Courtown catchment Single works serving Gorey and Courtown Less operational costs Disadvantages Possible septicity in long rising main of raw sewage. However a solution can be engineered should it arise Asset of land at Gorey will be underused Table 2-4 Advantages and Disadvantages of Option 2 (Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision ) Ryan Hanley consulting engineers 19 December 2005 EPA Export :22:46:03

22 2.5.4 Selected Wastewater Treatment/Disposal Options The Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision concludes that the proposed treatment works to serve Gorey should be located at Courtown (Option 2) as it has the most economic whole life cost (NPV) of the two suitable alternatives that were examined in detail. Details of the economic comparison from their report are shown in Table 2-5. Capital Cost Operating Cost (at year 2025) Total NPV Cost (Capital & Operational) Option 1 (Treatment at Gorey) 5,477, ,184 9,121,704 Option 2 (Treatment at Courtown) 5,738, ,724 8,602,857 Difference 260,850 58, ,847 Table 2-5 Economic Comparison of Option 1 and Option 2 Note: The Net Present Value (NPV) was calculated by capitalising operating costs over a 20-year period using the discount rate of 5% Although Option 2 has a marginally higher capital cost (4.75% higher) than Option 1, its operating costs are significantly lower (20% less) than Option 1. When these operating costs are capitalised over a twenty year period using the discount rate of 5.0%, Option 2 (Treatment at Courtown) is the cheaper option by 518,847. The detailed assessment of the Environmental Impact of the Courtown WWTP extension, which follows in Section 3, is based on Option Courtown WWTP site selection (from Courtown Main Drainage EIS, 1996) Introduction The following is a synopsis of the site selection process undertaken for the existing Courtown WWTP as part of the Environmental Impact Statement for the Courtown Drainage Scheme (1996). Further details of the site selection are available by consulting with that document. A comprehensive search for a suitable site was undertaken for the Environmental Impact Statement for the Courtown Drainage Scheme (1996). Initial screening was carried out on the basis of the site selection constraints, stated below, resulting in five alternative sites being considered. The location of the sites considered are shown in Figure 2-4. Constraints The existing drainage network was discharging to a septic tank located at the South Beach. Courtown Village drained by gravity to this point while sewage from the Riverchapel area was pumped to the sewer network in Courtown Village. Effluent from the septic tank discharged via an outfall point just south of the South Beach. Under the upgrading of the sewer network then proposed as part of the Courtown Drainage Scheme, sewage from Courtown Village would be collected to the general area of the Ryan Hanley consulting engineers 20 December 2005 EPA Export :22:46:03

23 existing septic tank with no feasible alternative to this. Sewage from the Riverchapel area would continue to be pumped to the main sewer network serving Courtown Village under the proposal. The Hydrographic Marine Survey, established that an outfall pipeline located in the general area of the existing outfall, but extending some 340 metres into the sea would be a suitable outfall for the effluent from the Courtown Wastewater Treatment Plant. Discharge of treated effluent to either the Owenavorragh River or the Breanoge stream was not feasible due to lack of assimilative capacity. The Office of Public Works designated a wooded area to the north of Courtown as a Natural Heritage Area. The Site Name for the Area is Courtown Dunes and Glen and the Site Code is Option 1 - South Beach This site is situated immediately south of the existing harbour adjoining the seafront. The construction of the treatment works at this site would involve the development of an enclosed plant. The enclosing building would be some 68 metres long and approx. 24 metres wide. Located adjoining the seashore and `dug into' the coastal embankment, the building would have a floor level of 7.0m O.D. with a roof and parapet level of 14.0m O.D. Option 2 - Seamount Hill This site is located south of the existing developed area of the town. It is some 500m from the harbour and some 70m from the foreshore. The site is an elevated location (30-32m O.D.) and situated close to the top of the cliffs. While there is no built development within close proximity, there is a caravan park located some 120m to the north. Option 3 - Adjacent to "Brick and Tile Works" This site is in the general vicinity of the site described in Option 5 below. Option 4 - Seamount Hill This site is located adjacent to the site described at Option 2 and 100m further away from the top of the cliff. Option 5 - Ballymoney Road (Location of Courtown WWTP) This site is located adjacent to the Ballymoney Road, 250m south of Ballinatray Bridge and approximately 1km north west of Courtown Harbour. Raw sewage would be pumped from the South Beach to a treatment plant on this site. Final effluent would be conveyed by means of an outfall pipeline to discharge to the sea some 340m offshore from the South Beach. Ryan Hanley consulting engineers 21 December 2005 EPA Export :22:46:03

24 Figure 2-4 Alternative sites considered for the Courtown WWTP (Extracted from Environmental Impact Statement for the Courtown Drainage Scheme, 1996) Ryan Hanley consulting engineers 22 December 2005 EPA Export :22:46:03

25 Selected Site Having examined the advantages and disadvantages of each of the five sites, it was considered that Option 5 was the optimum site for the location of the wastewater treatment works. The annual running costs for Option 5 were estimated to be greater than for Option 4 at the design stage of the Scheme. However, this difference was deemed insignificant in relation to the overall estimated annual running costs, and Option 5 had significant advantages over Option 4 in that its impact on the environment would be significantly less. The detailed assessment of the Environmental Impact of the Courtown Drainage Scheme (1996) was based on Option 5. The Courtown WWTP was subsequently constructed at the site considered under Option ASSOCIATED DEVELOPMENTS Outfall to Sea at Courtown The project will give rise to a need to reassess the existing sea outfall and assimilative capacity of the receiving waters to accept the higher hydraulic and biological loads resulting from the extension to the Courtown WWTP. The impact of the higher loads being discharged through the outfall pipeline is dealt with in Section 3.4 of this report. Effluent quality limits are reviewed and recommendations made to comply with the European Union Directive on Bathing Water Quality (76/160/EEC) and to comply with the requirements for Blue Flag accreditation at the Courtown North Beach Disposal of Sludge The upgraded Courtown WWTP facility will produce approximately 8,200m³/annum of sludge assuming a dry solids content of 20%. The sludge dewatered at Courtown will be transported by road to the Sludge Hub Centre at Wexford Town WWTW for further treatment and disposal. The facilities for further treatment and disposal of sludges arising from the proposed works are being provided in accordance with the Wexford Sludge Management Plan. Ryan Hanley consulting engineers 23 December 2005 EPA Export :22:46:03

26 3 DESCRIPTION OF THE EXISTING ENVIRONMENT, IMPACTS ON THE EXISTING ENVIRONMENT AND MITIGATION MEASURES 3.1 HUMAN BEINGS Human Beings in the Existing Environment Courtown is a seaside tourist resort located in the south east of County Wexford. Tourism is fundamental to the economic life of Courtown and it has hotels, guesthouses and a number of caravan parks to accommodate the large influx of visitors in the summer months. Courtown's popularity as a seaside resort depends to a large extent on its beaches and in particular the North Beach. The Wexford Development plan has the stated aim of facilitating the strengthening and diversification of the tourism roles of traditional seaside resorts including Courtown. This includes the promotion of linkages to their rural hinterlands and the provision of a range of outdoor and wet weather facilities. The development plan also has the stated aim of maintaining the Blue Flag status at the beach in Courtown. The recently completed Courtown Wastewater Treatment Plant provides for the existing and future sewage treatment requirements of Courtown and Riverchapel. Gorey Town is situated 4km west of Courtown. It has an existing wastewater treatment plant which was commissioned in The plant is currently overloaded. The Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision recommends the provision of a treatment works with a Population Equivalent of 15,000 to serve the needs of Gorey Town and its environs until the year Subsequent to the issue of that report and following a review of recent population increases in Gorey and a review of the projected population growth, Wexford County Council have revised the projected 2025 population for Gorey from 15,000 to 25,000. It is proposed that the plant be upsized in two phases with Phase I to cater for the Gorey design population of 15,000 and Phase II to cater for the most recent projected population of 25,000 for Gorey. The Gorey MDS Stage 2 Preliminary Report Part III, JB Barry & Partners Revision also recommends that this plant be located in Courtown as it has the most economic Whole Life Cost (NPV) of the two suitable alternatives that were examined in detail Impacts on Human Beings "Do Nothing Scenario" The lack of a wastewater treatment works to serve Gorey Town has a number of negative impacts on human beings: The existing receiving waters for the effluent from the Gorey STW, the Banoge River, can have very low flows resulting in very low dilutions and making it unsustainable for increased future discharges. The inadequacies of the existing wastewater treatment works is a restriction on the advancement of further development in Gorey Town. Ryan Hanley consulting engineers 24 December 2005 EPA Export :22:46:03

27 Positive Impacts: Completion of the project will overcome various negative impacts of the "Do Nothing" scenario and consequently will have a number of positive impacts on human beings: Improvement of quality of the River Banoge waters downstream of Gorey by the removal of the current effluent discharge to the river. It will remove a major impediment to the advancement of new developments in Gorey Town. The increased load at the Courtown WWTP will provide increased balancing of the severe seasonal effects of the Courtown catchment caused by the seasonal influx of visitors. The project will provide sludge dewatering facilities for sludges arising at the Courtown WWTP and imported sludges in the Gorey region. This will be part of a properly regulated and co-ordinated sludge treatment plan for the Gorey region in accordance with the requirements of the Wexford Sludge Management Study (Draft Final Report), T.J. O Connor & Associates, March Negative Impacts The Courtown WWTP will be extended resulting in an impact on human beings of a temporary nature during construction of the Works. Construction plant, including excavators, rock breakers, dewatering pumps will result in increased noise levels. There will be increased temporary traffic flows due to the construction staff travelling to/from the site and from delivery of materials to the site. The disposal of surplus materials off site will also increase the traffic flow. Completion of the project will have a number of negative impacts on human beings: There will be an increase in the quantity of odours produced within the site, however, the proposed odour abatement measures will reduce odours. The Courtown WWTP will act as a satellite centre for the reception of sludges arising in the Gorey area. This will result in an average of 7 tankers delivering to the site each weekday and additional sludge reception and treatment facilities within the site. Transport of dewatered sludge from the works will result in an increase in trips to/from the site from 1-2 trips/week for the current plant to approximately 16 trips/week when the plant is running at full capacity. Other traffic increases associated with the proposed works consist of operating staff, visitors, deliveries and waste removal. An additional 1 2 staff are anticipated to operate the extended WWTP. The number of visitors (including deliveries) to the site will not be significant. Mitigation Measures Mitigation and reductive measures to deal with increased noise levels are outlined in Section 3.6. The Contractor will be required to control dust levels on site through spraying of surfaces. The contractor will be required to keep all public roads adjacent to the site free from construction dirt. The Contractor will be required to use a road sweeper and to provide a wheel spray at the exit from the site to achieve this. The Contractor will be required to re-use all suitable excavated material within the site as fill or for landscaping to minimise the quantity of spoil transported off site. Ryan Hanley consulting engineers 25 December 2005 EPA Export :22:46:03

28 Transport of sludges to the site with a dry solids concentration of less than 8% will require a sealed tanker. Sludges with a dry solids content in excess of 8% being transported to/from the site will require a trailer/skip. The trailer or skip will be covered to prevent spillages of sludge and odour nuisance. Odour control measures for the WWTP including, the sludge reception and treatment facilities, are outlined in Section 3.5. It is anticipated that the overall traffic increase will not be significant. It should be noted that most of the heavy vehicle traffic movements generated by the development will access or egress from the N11 National Primary Road approximately 4km north west of the treatment plant site. The N11 currently passes through Gorey Town, however, on completion of the Arklow-Gorey By-Pass the distance between the site and the new N11 motorway will reduce to 2.4km and will be accessible from the Courtown WWTP before reaching Gorey Town. Thus it is anticipated that there will be minimal increases in heavy traffic movements through the two main population centres adjacent to the Courtown WWTP site. The affects of the project during construction and operation on air quality, water quality, landscape character and visual impact, cultural heritage and material assets are discussed in subsequent sections of this chapter. Mitigation measures are proposed in each respective section to minimise the impact of the development on human beings and the environment. The above mitigation measures will minimize the impact of the project on human beings. 3.2 ECOLOGY This element of the Environmental Impact Study is based on a study undertaken by Aquafact International Services Ltd. The full text of their report is included in Appendix B Ecology in the Existing Environment The Courtown WWTP site is not listed by the National Parks and Wildlife Service as a National Heritage Area (NHA) nor as a Special Area of Conservation (SAC) and is therefore not regarded as an area of scientific importance. Terrestrial Habitat The terrestrial habitat in the vicinity of the Courtown WWTP has been highly modified by agricultural practice. A mixture of rough pasture land and plantations are the two habitat types that are present around the proposed development site. The Courtown WWTP contains an existing WWTP and associated roads, structures, services and landscaped areas. The animals observed during the course of the original survey were typical of agricultural land with mammals such as rabbits, rats and fox and birds such as magpie, blackbird, starling, chaffinches and robins being seen. Subtidal Habitat The subtidal area was examined by taking samples at four locations in the vicinity of the existing sewerage outfall. The samples were taken using a 0.025m² stainless steel grab. On return to shore, the material collected in the grab was washed through a 1.00mm sieve Ryan Hanley consulting engineers 26 December 2005 EPA Export :22:46:03

29 prior to fixing in 4% buffered formalin and later preservation in 70% alcohol. On return to the laboratory, the samples were sorted by eye. All faunal returns were identified to species level where possible. The following species have been recorded off Courtown: Aphrodite aculeata, Eumida bahusiensis, Eteone longa, Anaitides groenlandica, Anaitides maculata, Nephtys hombergii, Tharyx sp, Scoloplos armiger, Spiophanes bombyx, Capitella capitata, Amphictene auricoma, Cultellus pellucidus, Nucula turgida, Donax vitattus, Ophiura sp and Amphiura sp. None of these species are considered rare or unusual. The community is attributable to a clean sand Donax community. The sediments of the subtidal in the area are medium to fine sands that are low in silt-clay levels. These types of sediments reflect medium current speeds that prevent the falling out of the finer sized (< 63 µm) particles. Marine Mammals Both Common and Risso s Dolphin, Minke whale, Fin whale, Orca, Beaked whales and Pilot whales are all recorded occasionally in the Irish Sea and have been sighted in the Courtown area. However, sightings are more common on the South coast in the Celtic Sea. The Wexford population of Grey seals was estimated as between 450 and 580 animals (Kiely et al. 2000) and a Grey seal colony exists on Raven Point. There is also a colony reported from the small island off Roney Point near Courtown beach. These seals are expected to use the waters of the proposed out fall site Impacts on Ecology (Terrestrial) The terrestrial communities in the vicinity of and within the Courtown WWTP have been altered by man s activities and are therefore of low ecological and conservation value. The extension of the treatment plant in the proposed area will not have any significant long term negative impacts. The area of land on which the existing plant is to be extended is within the boundaries of the land considered in the original EIS for the Courtown WWTP. The land is not listed as an area of scientific interest. During the construction phase, the flora will be affected due to the construction activities. However, the temporal effects of this will be short and the plants will quickly re-colonise available space once construction has been completed. Mammals will be disturbed during the construction phase of this project but as with the flora, this effect will be short term and these species regular activities should return to normal once construction is complete Impacts on Ecology (Marine) The marine flora and fauna present at Courtown were found to be representative of marine habitats along the east coast. No rare or unusual species or communities were recorded. The subtidal assemblage that has been described for the offshore area at Courtown occurs at several locations around the Irish coast. The sediments of these off-shore locations were fine sands with little slit-clay indicating relatively strong currents. Ryan Hanley consulting engineers 27 December 2005 EPA Export :22:46:03

30 The increase in discharge from the outfall pipe will have an impact on the biological communities in the vicinity of the pipe. There will be an increase in biomass of opportunistic species such as the polychaete Capitella capitata, a species that is well documented in being tolerant of organic enrichment. Less tolerant species e.g. Anaitides and the bivalve species Cultellus and Donax, are sensitive to increased levels of organic enrichment and will no longer be found in the area around the outfall pipe. Due to the high tidal velocities in the area, it is considered that the dispersion and dilution of effluent will be extensive and rapid and that the area of significant impact will be in the region of tens of metres north and south of the end of the pipe. Further more, as the effluent will be fresh water, the plume will rise to the sea surface thereby reducing the potential for impact on the sea bed. The effects of the increase in discharge from the outfall pipe on ecology are predicted to be low with no significant impact predicted for commercial fishing activities in the Courtown Area. The main commercially fished species in the Courtown area is the whelk and as its flesh is not affected by bacteria, the fishery will not be compromised. Marine Mammals Given high dilution and dispersion characteristics of the site, it is considered very unlikely that the cetacean and seal populations that occur in the area will be significantly negatively impacted by the proposed development Mitigation of Impacts on Ecology 3.3 SOILS The effects of the project on ecology are predicted to be minor. An Ecological Landscaping scheme will be implemented at the end of the construction stage which will assist native plant species to re-colonise available landscaping areas. No mitigation measures are proposed for the marine outfall Soils in the Existing Environment A Site Investigation was undertaken at the Courtown WWTP in May 1999 prior to commencement of the construction of the existing WWTP. The Investigation included trial pits, subsoil probes and Shell and Auger borehole tests. This part of County Wexford's east coast is known as the Macamores, from the Irish "An Maca Mór", or "the Big Marl". The name refers to a five mile long strip of marl, which is marine mud deposited inland by the Ice Age. Geological Survey maps of the area indicate that the site is underlain by Ordovician sandstones. As a result of the investigations undertaken the site geology can be broadly defined as brown silty clay (known as marl) overlying weathered shale. These components are described as follows: Marl Almost all of the boreholes encountered brown silty clay, known locally as yellow marl. The consistency of the marl was generally firm, becoming stiff and very stiff with depth, and frequently grading into a weathered shale. Ryan Hanley consulting engineers 28 December 2005 EPA Export :22:46:03

31 Shale The bedrock encountered is generally an extremely fractured and weathered shale or slatey shale of the Ordovician age. Rock comprises highly cleaved and steeply dipping turbidite sequences containing variable proportions of thinly interbedded volcanic lithologies. Turbidites are cyclical sequences of alternating "dirty" sandstones (i.e. greywackes), siltstones and mudstones Impacts on Soils The construction of the extension to the wastewater treatment plant will impact on soils on the site to the extent that excavation works will be undertaken and the site will incorporate underground tanks, buildings, paved areas, grassed areas, mounds and landscaping in place of existing paved and landscaped areas within the site. It is considered that these changes will be small scale and that there will be no negative impact on soils outside the boundary of the treatment works site. Previous excavations within the site indicate that small amounts of rock excavation may be required for the deeper excavations within the site. The site investigation indicates that the rock is of poor quality and accordingly should not be difficult to excavate. However, rock excavation may require the use of a mechanical rock breaker which would have a noise impact. This impact would persist for a short time only during the construction of the works. Construction noise impacts are dealt with in Section Mitigating Impacts on Soils All landscaped areas within the site will be completed/restored after the construction works are finished. Any impact on the soils should be temporary in nature. 3.4 WATER QUALITY Introduction Hydro Environmental Ltd. was appointed by Ryan Hanley & Co., Consulting Engineers Galway, on behalf of Wexford Co. Council to undertake a detailed hydrodynamic and water quality model study of the proposed Courtown and Gorey treated sewage effluent discharge to the Irish Sea via the existing Courtown Marine Outfall pipe. The full text of the report, tables and diagrams are included in Appendix C. Details of the outfall hydraulics and nearfield dilutions are contained in a separate report (included in Appendix J) entitled: Nearfield Dilution Assessment of Marine Outfall at Courtown, Hydro Environmental Ltd., November This study is a detailed review of the proposed WWTP effluent discharge and its impact on the receiving water quality. The study involved commissioning a detailed hydrographic field investigation of the flow and dispersion regime at the outfall site. This data was subsequently used in the development, calibration and application of a hydrodynamic and dispersion coastal model. Dispersion modelling was carried out to predict the spread and fate of the proposed discharge under a range of tidal and meteorological conditions in medium to far field regions (i.e. outside of the nearfield mixing zone). The model study also utilises the hydrographic measurement and modelling work was carried out in 1994/1995 EIS study for the original Courtown Scheme and a more recent survey (2003) Ryan Hanley consulting engineers 29 December 2005 EPA Export :22:46:03

32 that as carried out as part of the Courtown Marina Study. The model study also examines the outfall pipeline flow capacity and diffuser initial dilutions under the proposed effluent design load Proposed Discharge The proposed Courtown / Gorey upgraded sewerage schemes will collect and treat the combined sewage from both towns and discharge the final effluent to the receiving marine waters of the Irish Sea via the existing Courtown outfall located 330m off Breanoge Point. The proposed upgraded PE is 45,000 having a 1DWF flow of 8,100m 3 per day (94l/s) and a 3DWF flow of 24,300m 3 per day (281l/s). The WWTP capacity is 3DWF and the pumping capacity of the rising mains discharging to the plant will be limited to this capacity. Flows exceeding 3DWF arising in Courtown are stored in a storm water holding tank at the pumping station with a discharge via the Courtown outfall of flows exceeding the pumping and storage capacity of the pumping station. The proposed level of treatment will be secondary treatment producing final effluent standards of 25 mg/l BOD, 35mg/l and 1 x 10 6 No./100ml Faecal Coliforms (FC) Bathing Waters The designated Bathing areas at Courtown are the north and south beaches in the immediate vicinity of the town and harbour entrance. The Courtown North Beach, up to this year, enjoyed Blue Flag Status (EPA, 2004). Unfortunately, all of County Wexford s Blue Flag Beaches including the Courtown North Beach, lost their blue flag status in the latest published report (Taisce, 2005). This failure is attributed to anomalies in the water quality testing procedures as opposed to a notable deterioration in the water quality. Bacteriological parameters from water samples taken from the bathing areas in Courtown have been consistently within the Blue Flag parameter limits with the exception of the above mentioned anomalies. Weekly bathing water analysis has been carried out in Courtown between May and September All bacteriological results, without exception, during this period have been compliant with the Blue Flag standard. There are no designated Shellfisheries (i.e. licensed shellfishery sites by the Dept. of the Marine) in the coastline region of Courtown Harbour, however it is probable that wild shellfisheries exist in the region. The critical water quality standard influencing the sewerage scheme and the proposed final effluent standard is the bathing water directive and compliance with the Blue Flag bacterial standards at Courtown north and south bathing beaches. Bathing Water Standards The Quality Of Bathing Waters Regulations, 1992 (S.I. No. 155/1992) sets the Irish National Limit values which relate to the quality of bathing waters standards including mandatory values for faecal coliform and faecal streptococci concentrations. The National Limits are based on the EC Guideline Values and EC Mandatory Values as set out in Directive No. 76/160/EEC concerning the quality of bathing water. The bathing water standards are summarised in Table 3-1. The Blue Flag is a well-recognised, well respected eco-label, awarded to beaches and marinas with excellent environmental management. The Blue Flag beach standard in Ryan Hanley consulting engineers 30 December 2005 EPA Export :22:46:03

33 regard to bacterial impact requires that the EU Directive Guideline limit of 100 No./100ml faecal coliforms at 80% compliance and 100 No./100ml faecal streptococci at 90% compliance be met. An Taisce is the national operator for the International Blue Flag Campaign in Ireland. The Blue Flag bathing season runs from June to August. The Blue Flag for beaches is only valid during this time. The general practice in establishing the effluent treatment standard is to comply with the Blue Flag Beach water quality standards at recognised bathing areas. In the case of Courtown Harbour the principal Bathing area beaches are located immediately to the north and the south of the Harbour inlet. These bathing beaches are located 550m west northwest and 350m west of the outfall point. Total Coliforms (No./100ml) Faecal Coliforms (No./100ml) Faecal Streps (No./100ml) % Compliance EC Guideline Values % EC Mandatory Values 10,000 2,000-95% National Mandatory Values (S.I. No. 155/1992) 5,000 1, % 95% Table 3-1 Irish National and EU Directive Bathing Water Quality Standards Marine Hydrographic Survey Information The following hydrographic surveys were used in the impact assessment study and also in the development, calibration and verification of the hydrodynamic and dispersion model: Irish HydroData Ltd. Survey (2005) for the current Courtown/Gorey Sewerage Scheme EIS Study which was commissioned as part of this current EIS study (Report included in Appendix I). Irish HydroData Survey Ltd. (2003) for the proposed Courtown Marina feasibility Study on behalf of Wexford Co. Council. Hydrographic Surveys Ltd. Marine Survey for the Courtown Sewerage Scheme Preliminary Engineering and EIS study (1996) Irish Hydrodata Survey May 2005 Courtown/Gorey Sewerage Scheme EIS Irish Hydrodata Ltd. Cork was commissioned as part of this EIS study to carry out the following hydrometric survey work in the vicinity of the Courtown outfall. This data was used to calibrate and verify the hydrodynamic model and provide a better understanding of the mixing processes in operation at the outfall site. A Nortek Aquadropp 1MHz Acoustic Doppler Current Profiler (ADCP) was deployed just past the end of the outfall pipe on the 26 th May to the 19 th June 05. Current velocity profiles were recorded at 10-minute intervals using a 1-minute average. The sampling cell was 0.5m in the vertical providing x,y and z velocity measurements in 14 no 0.5m bin depths from 1.45m to 7.95m above seabed. The ADCP also recorded water depth at the site, which was converted to tide level. Ryan Hanley consulting engineers 31 December 2005 EPA Export :22:46:03

34 A recording weather station was deployed at the treatment plant on the 19 th May to 19 th June 05. Continuous measurements of wind speed and direction at 10minute intervals were obtained. Continuous Dye releases were conducted on 8 th and 9 th June. The release on the 8 th coincided with an ebbing tide while that on the 9 th corresponded to a flood tide. The dye was continuously injected into the outfall pipeline upstream of the diffuser outfall. Dye concentration measurements were made at depths of 0.5m and 2.5m below the water surface. An Interocean S4 vector averaging RCM was deployed on a surface-following buoy directly above the diffuser for the 24 h period during the dye release. Speed and direction data were recorded at 10-minute intervals using a 5-minute average. Streamline drogue tracking during the dye dispersion study was carried out to separate out the advection component of the dye movement. Irish HydroData Survey for the proposed Courtown Marina Scheme 2004 The scope of this marine survey carried out by Irish Hydrodata Ltd. in February 2003 was as follows: Detailed Bathymetric Survey of the shoreline immediately north and south of Courtown Harbour (1km longitudinally and 200m transversely). A more general bathymetric survey of the coastline waters north and south of Courtown was also carried out (2km by 500m). Tide velocities (near surface, mid-depth and near bottom) over complete spring and neap tidal cycles at two locations (5 th Feb and 12 th February 2003). Continuous tide elevation monitoring was carried out over the duration of the survey work (5 to 13 th February). Geophysical survey of the near shore region north of Courtown Harbour entrance Hydrographic Marine Survey for Courtown Drainage Scheme EIS 1996 Hydrographic marine survey fieldwork was carried out in July, August and September 1994, and the following data was obtained: Continuous tide level measurements for a period of 30 days, using a self-logging tide gauge instrument located in Courtown Harbour. Discrete tide elevation measurements at four locations. Wind speed, wind direction and barometric pressure for a period of 30 days, using automatic wind/climatological gauge recorders installed in Courtown Harbour. Continuous current velocity and direction measurements for a period of 30 days, using a self-recording multi-parameter meter installed at Site A. Drogue tracking data from surface, mid-depth and bottom `cruciform' drogues released during spring and neap tides at various stages of the tidal cycle. Fixed station current velocity, current direction and water quality measurements obtained during spring and neap tides. Dye dispersion data from four discrete dye releases carried out during spring and neap tides. Biological sampling information obtained from five locations, and at five stages of the tide for each location. Ryan Hanley consulting engineers 32 December 2005 EPA Export :22:46:03

35 Echo-sounding survey using digitised echo-sounding equipment to determine bathymetry data for the study area. Seismic seabed profiling using an acoustic sub-bottom profiling system to determine sub-sea profiles along the outfall pipeline route and along lines parallel to the route. Sub-sea site investigation fieldwork including shell and auger boreholes along the proposed pipeline route, rotary coring along the proposed pipeline route. Ryan Hanley consulting engineers 33 December 2005 EPA Export :22:46:03

36 Courtown WWTP Extension - Environmental Impact Statement Killbegnet Ballmoney Lower Duffcarrick R Courtown se ru Outfall to f c Fo op r i yr ns ig pe ht ct ow ion ne pu r r rp eq os ui es re o d nl fo y. ra ny ot he m below MSL ns en Co Roney Pt Glascarrig Pt Cahore Pt Figure 3-1 Model extent and modelled bathymetry Ryan Hanley consulting engineers 34 December 2005 EPA Export :22:46:03

37 3.4.5 Existing Environment of Receiving Waters at Courtown The ambient salinity at Courtown is generally 34 to 35ppt which represents a water density of to 1026 kg/m 3 at 12 o Celsius. The tidal ranges at Courtown are very small 0.6 to 0.8m spring tides and 0.3 to 0.5m neap tides. This is due to the sites proximity to an amphidromic nodal point located just off Arklow. Recorded tidal streams exhibit strong rectilinear, longshore flow pattern with well-defined ebb and flood tidal flow direction and magnitude. The vertical velocity profile at all surveyed sites was found to be very consistent in respect to direction and speed with velocity magnitude decreasing with increased depth in keeping with the 1-dimensional flow roughness laws. The flow directions are slightly east of north reversing to slightly east of south. The duration of ebb and flood flows is evenly split at 6 to 6.2 hrs. In the vicinity of the outfall the mid-ebb and flood (maximum) are of the order of 0.45 to 0.5 m/s and 0.35 to 0.4 on spring and neap tides respectively. At tidal reversal the duration of slack tides having velocities of less than 0.1m/s lasts for approximately 1hour. The seabed level at the Courtown outfall is 8.4m OD Malin giving a highwater and low water depths of 8.0 to 8.8m O.D. Malin spring tides. This depth of water is sufficient to achieve good initial dilution. Wind Frequency Data for the period 1 st January 1975 to 31 st December 2004 was obtained from the Meteorological Office for their Met station at Rosslare (the nearest and most relevant coastal meteorological station to Courtown. Direction All winds > 5knots >10knots >20knots > 30 knots North East East South East South South West West North West North Total Frequencies given as percentage Please note 1 knot equals m/s Table 3-2 Wind Speed and Direction Frequency Table Rosslare Met Station Adverse Wind Condition The frequency of occurrence of an onshore (adverse) wind direction in respect to Courtown bathing beaches is from the following sectors South East, East and North East. The critical wind speed in respect to lateral movement of a surface plume towards the shore is 5m/s (approx 10kts) or greater. The frequency of occurrence of such winds from the North East to the South East is 12.6% of the time. Larger winds exceeding 20 kts occur on average Ryan Hanley consulting engineers 35 December 2005 EPA Export :22:46:04

38 3.1% of the time from these sectors. These larger magnitude winds often produce surface wave effects resulting in greater vertical and horizontal mixing Existing Effluent Discharges The present design hydraulic load from the Courtown WWTP is 3,750m³/day with a peak treated flow of 2DWF equivalent to 86.8 l/s. Mean Flow Peak Flow 43.4 l/s 86.8 l/s The plant was commissioned in August At present the average daily discharge from the plant is approximately 1,100 m³/day during dry weather with peak discharges during extreme storm events up to 6,100m³/day. The treated effluent discharges by a gravity outfall pipeline to the Irish Sea at a point located 330m immediately east of Breanoge Head. The outfall from the WWTP consists of a 400mm and 500mm Ductile Iron pipeline up to the shore and an 800mm diameter HDPE pipeline from the shore to outfall point at sea. The outfall discharge point is located at E320578, N The outfall is fitted with a four riser single port diffuser. The diffuser ports are located 500mm above the seabed, are fitted with tideflex non-return valves that discharge horizontal and perpendicular to the flow direction. The diffuser length is 8m from first port to last port. Storm Overflows from Courtown Collection System For discharges to bathing waters, it is recommended that a restricted spill frequency during the bathing season should apply unless it can be shown that the design will achieve the water quality standards of the Bathing Water Directive for at least 98.2% of the time (Storm Water Overflows, G Galvin, 1994). The hydrodynamic and dispersion model has shown that the discharge from the outfall including storm overflows from the Courtown collection system will achieve the water quality standards of the Bathing Water Directive for at least 98.2% of the time. Bacteriological Sampling of Courtown Bathing Waters The 2003 summer faecal coliform sampling results for the Courtown bathing water are outlined in Table 3-3. The samples were taken weekly during the Blue Flag bathing season months (June, July and August). A maximum concentration of 15 No./100ml was recorded with the remaining samples below 5 No./100ml. Summer 2003 is the first summer since full commissioning of the Courtown WWTP. These results indicate that the WWTP and outfall are operating satisfactorily. Ryan Hanley consulting engineers 36 December 2005 EPA Export :22:46:04

39 Sampling Date & Time Faecal coliforms/100ml 11: : : : : : : : : :50 1 Table 3-3 Faecal coliform sampling results for Courtown Beach during summer Proposed Alteration to Discharge of Treated Effluent The proposed design hydraulic load for the combined Courtown and Gorey sewage effluent is 8,100 m³/day representing 180l/day/PE. The peak treated flow will be 3DWF or 281 l/s. Mean Treated Flow Peak Treated Flow l/s l/s The effluent standards for the proposed WWTP are: - Biochemical Oxygen Demand (BOD5) at 95-percentile = 25mg/l - Chemical Oxygen Demand (COD) at 95-percentile = 125mg/l - Total Suspended Solid (TSS) at 95-percentile = 35mg/l - Faecal Coliforms (FC) = 1 x 10 6 No./100ml The proposed mean (1DWF) hydraulic load represents a doubling (2.16 to be exact) of the existing mean discharge and a tripling of the (3.23 to be exact) peak flow Hydrodynamic and Effluent Dispersion Modelling The objectives of the water quality model study are as follows:- To simulate the water circulation patterns in the receiving coastal waters under different tide, wind and freshwater inflow conditions. To assess the environmental impact of the proposed treated effluent discharge from the Courtown outfall in terms of near and far field water quality impacts. The critical water quality parameter in respect to the Courtown Outfall discharge is faecal coliform concentration as an indicator of bacterial impact. Ryan Hanley consulting engineers 37 December 2005 EPA Export :22:46:04

40 To predict the spread and fate of faecal coliforms and other relevant parameters for specified loadings and wastewater treatment levels (i.e. raw, secondary, treated and disinfected). To this aim a two-dimensional depth-averaged hydrodynamic and water quality model of the Coastal Region off Courtown was developed, calibrated and validated against field survey data. In order to define accurately the shoreline geometry and seabed bathymetry of the receiving waters the model was constructed using a refined horizontal grid spacing of 50m x 50m. The extent of the model was from Cahore Point north to Kilbegnet east of Tara Hill, measuring 15.8km in length (south to north) and 8.5km west to east. Open sea boundary conditions had to be applied at three of the four model boundaries. A varying tidal elevation boundary condition was specified along the southern boundary, a streamline boundary (i.e. zero normal flux) along the east model boundary and a tidal varying velocity boundary condition along the north boundary. The western boundary is defined by the Wexford shoreline. The varying tidal elevation boundary was defined using 27 tidal constituents derived from the Irish HydroData ADCP survey at the outfall site (May / June 2005). The northern velocity boundary was also defined using the derived depth averaged U-V velocity tidal constituents (27No.) from the ADCP survey and scaled up as part of model calibration to produce the desired effect in the coastal waters near Courtown. The hydrodynamic and dispersion model were calibrated and validated against current metering, tide levels and dye survey results. Good agreement was achieved within the area of interest between computed and observed hydrographic data and thus confirming the confidence that can be placed on the model predictions. In this study the 2-D depth-averaged hydrodynamic and water quality model was used to: To determine the spread and fate of faecal coliform (i.e. bacteriological indicator) from the Courtown outfall under varying environmental/tide and effluent discharge conditions (1DWF and 3DWF flows). To provide hydrodynamic input to a 3-Dimensional particle-tracking model to investigate the impact of adverse wind conditions on the formation of a buoyant surface plume. To provide the hydrodynamics at the proposed outfall site for input to a near-field mixing / initial dilution model (CORMIX). A 3-dimensional particle-tracking model was developed to predict the spread and fate of an initially buoyant plume under the influence of tides and surface wind shear forces. This model used the computed depth averaged horizontal velocities and water depth and applied a theoretical vertical velocity profile (Prandtl s velocity distribution) to obtain the horizontal velocities at any given reference depth. Superimposed on this were the tideinduced currents. The effects of wind driven currents on the movement of particles throughout the water column were modelled by use of a logarithmic velocity profile. Vertical diffusion, tidal flow and wind horizontal dispersion and coliform die-off were modelled using a random walk technique. Full details of the both depth averaged 2-D hydrodynamic and dispersion models and the 3-D particle tracking surface plume models are given in the Hydro Environmental Report presented in Appendix C. Ryan Hanley consulting engineers 38 December 2005 EPA Export :22:46:04

41 Outfall Initial Dilutions For this assessment, the U.S. E.P.A approved Cornell Mixing Zone Expert System (CORMIX) (version 3.2) software package was used to simulate initial mixing and compute plume characteristics and centreline dilutions within a specified initial mixing zone. CORMIX was developed by Cornell University for simulating the initial mixing process of submerged and surface plumes from single and multi-port diffuser outfalls (Jirka et al., 1996). The software is approved by the U.S.E.P.A and is internationally recognised as the industry standard for such applications. The model is capable of simulating both the nearfield and far-field mixing, with the former being influenced by the initial jet momentum, buoyancy flux, and outfall geometry and the latter being influenced by buoyant spreading, advection and passive diffusion due to ambient turbulence. CORMIX computes the plume centreline dilution and plume geometry with respect to distance from the release point based on the hydrodynamic and geometric characteristics of the discharge and ambient receiving waters. CORMIX Initial dilution simulations were performed for the Courtown Diffuser which is shown in Ryan Hanley Drawing No. 1757/004 (Appendix A) for the proposed mean Flow of l/s and the proposed peak discharge of 281l/s subject to the following ambient hydrodynamic conditions: (i) (ii) Slack Tide condition (velocity of 0.02m/s) Spring Tidal Flows from 0.1 to 0.5m/s (iii) Neap tidal Flows from 0.1 to 0.4m/s The ambient density vertical profile was assumed uniform having a density of 1026 kg/m³. The local water depth at the site was set at 8.3m in all simulations. An ambient wind speed of 2m/s was specified For the slack flow conditions associated with high and low water slack tides (reversal of the tide) only nearfield initial dilutions could be calculated using CORMIX. Plume propagation outside of the mixing zone in CORMIX requires the specification of ambient currents, generated either by the tide or wind shear Impact of Proposed Discharge Depth Averaged Faecal Coliform Simulations The depth-averaged simulations showed that no direct plume impact on the bathing beaches at Courtown occurs with the plume advected longshore by the strong ebb and flood flows which were found to be of virtually equal strength and duration (mid-ebb/flood depth-averaged velocities typically 0.4 to 0.6m/s depending on the tide). The mechanism by which coliforms arrive at the Courtown shoreline and beach areas was identified to be by a process of lateral dispersion to the near shore waters and advection via the returning near shore currents. The 1DWF faecal coliform simulations show that the proposed discharge of 45,000pe at a final effluent concentration of 1.0 x 10 6 No./100ml do not breach the mandatory or Ryan Hanley consulting engineers 39 December 2005 EPA Export :22:46:04

42 guideline (Blue Flag) bathing water limits at Courtown, even when modelled with a reasonably conservative die-off rate ( t 90 of 24hrs). The north beach is the principal bathing beach where the blue flag status applies has a predicted 80-percentile concentration of 42 No/100ml for a 24hr t 90 die-off and only 11 No/100ml for a 12hr t 90 die-off. Little difference in concentration between neap and spring tides was observed with neap tides producing slightly higher percentile concentrations. Duffcarrick R. Courtown S1 S2 S3 S4 OUTFALL Roney Pt Figure 3-2 Location of Outfall and Observation sites (S1 to S4) Ryan Hanley consulting engineers 40 December 2005 EPA Export :22:46:04

43 OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-4 Spring Hydrodynamics 1 DWF, Die-Off Rate T 90 = 12hrs OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-5 Spring Hydrodynamics 1 DWF, Die-Off Rate T 90 = 24hrs OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-6 Neap Hydrodynamics 1 DWF, Die-Off Rate T 90 = 12hrs OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-7 Neap Hydrodynamics 1 DWF, Die-Off Rate T 90 = 24hrs The 3DWF spring tide and neap tide simulations using a t 90 of 24hours were found at the 80-percentile concentration to exceed the guideline bathing water limit of < 100No./100ml at (i.e. the Blue Flag standard) at both north and south beaches. The 3DWF simulations modelling a t 90 of 12hours were found to satisfy the Blue Flag requirements as the higher mortality rate limits the residual build-up of coliform numbers. The scenario of a continuous 3DWF discharging for at least 24hours is dependant on significant rainfall events with a high surface water run-off draining to the foul/combined collection network. Based on the high surface water run-off draining to the Courtown collection network at present, a rainfall event in excess in excess of 10mm in a 24 hour period is required to produce a flow to the WWTP approaching a continuous 3DWF for the existing plant hydraulic capacity of 15,000pe. The average number of days with a rainfall Ryan Hanley consulting engineers 41 December 2005 EPA Export :22:46:04

44 in excess of 10mm between 1985 and 2005 recorded at the Gorey weather station is 26.2 days per annum, which is equivalent to 7.2% of the time. A strict policy of storm water separation will apply to all new developments therefore limiting the storm water contribution when new foul loads are connected to the collection network. Consequently, the proportion of storm water discharging to the WWTP will reduce as the foul flow increases. The frequency of a continuous 3DWF discharging for at least 24hours with the extended WWTP will therefore lessen. Therefore the storm event frequency, coupled with a conservative summer die-off rate t 90 = 24hours is predicted to be reasonably infrequent and certainly less than 7.2% of the time. It is therefore predicted that the scenario of a continuous 3DWF discharging for at least 24hours will not exceed the 80percentile blue flag standard applicable over the entire bathing season. All other depth-averaged scenarios considered do not breach the Blue Flag standard. OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-8 Spring Hydrodynamics Continuous 3 DWF, Die-Off Rate T 90 = 12hrs OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-9 Spring Hydrodynamics Continuous 3 DWF, Die-Off Rate T 90 = 24hrs OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-10 Neap Hydrodynamics Continuous 3 DWF, Die-Off Rate T 90 = 12hrs OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE PERCENTILE Table 3-11 Neap Hydrodynamics Continuous 3 DWF, Die-Off Rate T 90 = 24hrs Ryan Hanley consulting engineers 42 December 2005 EPA Export :22:46:04

45 The 1DWF and 3DWF faecal coliform simulations easily meet the Irish and EU mandatory bathing standards of 1,000No./100ml at 90% compliance and 2,000No./100ml at 95% compliance at the Courtown north and south bathing beaches and within Courtown Harbour. Only in the vicinity of the outfall were such standards exceeded. Wind-advected Surface Plume Faecal coliform Simulations Long-term Met Eireann wind observations for Rosslare over the period indicate that the prevailing wind direction is from the SW and W direction. Onshore winds from the south east to the northeast sector which represent adverse wind direction for the bathing waters occur 23.75% of the time for all wind speeds and only 12.7% of the time for winds exceeding 10Kts (5.14m/s). The adverse wind sector in respect to plume movement towards Courtown shore is highlighted in yellow in Table Direction Frequency (%) All Speed >6kts Speed > 10kts Speed >21kts North North-East East South-East South South-West West North-West knot = 0.514m/s Table 3-12 Frequency analysis of Wind Speeds for the 8 principle wind directions The 1DWF dispersion simulations from the wind-advected surface plume faecal coliform simulations show that the proposed discharge of 45,000pe at a final effluent faecal coliform concentration of 1.0 x 10 6 No./100ml do not breach the mandatory or guideline (Blue Flag) bathing water quality limits at the Courtown Beaches under adverse winds of 5 and 10m/s. Stronger wind conditions were not considered as such conditions increase the wave action that enhances the vertical and lateral mixing and thus improving dilution rates and lessening the advective dominance of the wind on a surface layer plume. OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-13 Wind Calm - Mean Tide Hydrodynamics (1 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-14 Southerly Wind 10m/s - Mean Tide Hydrodynamics (1 DWF) Ryan Hanley consulting engineers 43 December 2005 EPA Export :22:46:04

46 OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-15 Westerly Wind 10m/s - Mean Tide Hydrodynamics (1 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-16 Northerly Wind 10m/s - Mean Tide Hydrodynamics (1 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-17 North Easterly Wind 5m/s - Mean Tide Hydrodynamics (1 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-18 North Easterly Wind 10m/s - Mean Tide Hydrodynamics (1 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-19 Easterly Wind 5m/s - Mean Tide Hydrodynamics (1 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-20 Easterly Wind 10m/s - Mean Tide Hydrodynamics (1 DWF) Ryan Hanley consulting engineers 44 December 2005 EPA Export :22:46:04

47 OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-21 South Easterly Wind 5m/s - Mean Tide Hydrodynamics (1 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-22 South Easterly Wind 10m/s - Mean Tide Hydrodynamics (1 DWF) The simulations show that the 3DWF load easily satisfies the Irish and EU mandatory bathing water quality standards at Courtown north and south bathing beaches and within Courtown Harbour. Only in the vicinity of the outfall are such mandatory standards not satisfied. The model simulations show that peak 3DWF flows will exceed the Blue Flag limit at Courtown under adverse winds blowing from the Northeast to Southeast sector. Wind frequency analysis indicates that adverse winds exceeding 5m/s occur 13% of the time from these sectors (135degree sector). The frequency of a continuous 3DWF discharging for at least 24hours coupled with an adverse wind condition is expected to be reasonably rare and it is therefore predicted that this scenario will not exceed the 80percentile blue flag standard applicable over the entire bathing season. OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-23 Wind Calm - Mean Tide Hydrodynamics (3 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-24 Southerly Wind 10m/s - Mean Tide Hydrodynamics (3 DWF) Ryan Hanley consulting engineers 45 December 2005 EPA Export :22:46:04

48 OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-25 Westerly Wind 10m/s - Mean Tide Hydrodynamics (3 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-26 Northerly Wind 10m/s - Mean Tide Hydrodynamics (3 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-27 North Easterly Wind 5m/s - Mean Tide Hydrodynamics (3 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-28 North Easterly Wind 10m/s - Mean Tide Hydrodynamics (3 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-29 Easterly Wind 5m/s - Mean Tide Hydrodynamics (3 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-30 Easterly Wind 10m/s - Mean Tide Hydrodynamics (3 DWF) Ryan Hanley consulting engineers 46 December 2005 EPA Export :22:46:04

49 OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-31 South Easterly Wind 5m/s - Mean Tide Hydrodynamics (3 DWF) OUTFALL S1 S2 S3 S4 AVERAGE PERCENTILE PERCENTILE PERCENTILE Table 3-32 South Easterly Wind 10m/s - Mean Tide Hydrodynamics (3 DWF) Outfall Pipeline Hydraulics The hydraulic assessment of the outfall pipeline indicate that the hydraulic capacity of initial section of pipeline from the wastewater treatment plant needs to be upgraded (chainage 0 to 1,160m) to accommodate the proposed peak flow. The remainder of the outfall pipeline and diffuser shows ample flow capacity available to discharge the proposed peak load of 281 l/s against a design tide of 2m O.D. This includes the marine outfall section of the pipeline. On upgrading of the capacity of the initial 1,160m of the outfall pipeline, the flow capacity of outfall pipeline is calculated to be up to 308 l/s. The proposed peak discharge will be 281 l/s leaving a spare capacity of up to 9.6%. The flow distribution between the 4 diffuser tideflex ports was found to be reasonably equally distributed among the four ports with the lowest flow occurring at the inner port, which is desirable. Outfall Initial Dilutions The CORMIX Initial Dilution Simulations predict a buoyant plume that rises to the surface mixing in the top 1m during slack tides, and generally occupying the top 2 to 2.5m during neap and spring tides for a 1 DWF discharge. The 3DWF flow being more buoyant was found to generally occupy the top 1.25 to 1.75m during neap and spring tides. In general the outfall simulations show that excellent dilutions should be achieved by the outfall configuration for both neap and spring tidal flows. Relatively low initial dilutions of 29 and 16 are predicted for mean and peak effluent flows in the Near Field Region (NFR) of the outfall under slack flow conditions which is generally the case with all outfalls. Such slack flow hydrodynamic conditions seldom occur due to large-scale turbulence and when they do they are of very short duration. Typically slack tide velocities of less than 0.1m/s were found based on the ADCP data not to last for more than 1hour in a given tide). Slack flows generally exceed 0.02m/s to 0.05m/s at all times. A summary of the initial dilution results for 1DWF and 3 DWF flows are presented in Table 3-33 and Table The average tidal dilution and plume thickness at travel distances of 100 to 1000m are also given in the Table below. Ryan Hanley consulting engineers 47 December 2005 EPA Export :22:46:04

50 Tide Velocities Longitudinal Distance Nearfield 100m 200m 500m 1000m Slack (0.2m/s) m/s m/s m/s m/s m/s m/s Average Tidal Dilutions 1DWF Load Tide Nearfield 100m 200m 500m 1000m NEAP SPRING Average Plume thickness Tide Nearfield 100m 200m 500m 1000m NEAP m 2.27m 1.70m 2.23m SPRING m 2.58m 2.07m 3.00m Table DWF Initial Dilutions CORMIX Model Results Tide Velocities Longitudinal Distance Nearfield 100m 200m 500m 1000m Slack (0.2m/s) m/s m/s m/s m/s m/s m/s Average Tidal Dilutions 3DWF Load Tide Nearfield 100m 200m 500m 1000m NEAP SPRING Average Plume thickness Tide Nearfield 100m 200m 500m 1000m NEAP m 1.58m 1.25m 1.34m SPRING m 1.80m 1.47m 1.72m Table DWF Initial Dilutions CORMIX Model Results The computed dilutions presented above in Table 3-33 and Table 3-34 represent the minimum centreline dilution with the average dilution across the plume width a factor of 1.8 higher, based on a Gaussian distribution. Ryan Hanley consulting engineers 48 December 2005 EPA Export :22:46:04

51 Remedial or Reductive Measures Durations and frequency of 3DWF flows should be limited by separating out where possible the storm water contribution from the sewage flows. A strict policy of storm water separation should be applied for all new connections to all sewerage networks ultimately discharging to the Courtown WWTP Monitoring A detailed on-going monitoring programme should be implemented to measure the effluent flows and respective concentrations and also the receiving water quality at a number of locations along the north and south beaches and within the Harbour. This will provide better information on the background concentrations from other pollutant sources and provide meaningful water quality data for model verification in respect to faecal coliform survival rates in the receiving water and the efficiency of the WWTP bacterial removal. Under the Urban Waste Water Treatment Regulations, 2001, 12 samples per annum are required to monitor the effluent quality from a plant of the capacity of the proposed extended Courtown WWTP. The samples should be tested for parameters outlined in the consent standards. During the bathing season weekly testing of the effluent leaving the treatment plant site should be carried out to ensure that the effluent complies consent standards set for faecal coliforms. Monitoring of the water quality of the Courtown bathing areas will continue as part of the Blue Flag requirements. Weekly water samples from Blue Flag beaches should be tested during the testing period for the Blue Flag bathing season. 3.5 AIR QUALITY ODOUR In examining the environmental impact on air quality of the Courtown WWTP extension, the topic is address ed under the headings of odour and noise. Odour impacts are considered in this section with noise impacts addressed in Section Introduction Odour Monitoring Ireland was commissioned by Ryan Hanley Consulting Engineers to perform an odour audit and predictive odour impact assessment of the current plant and proposed upgrade to Courtown Wastewater Treatment Plant (WWTP). The full text of the reports is included in Appendix D. Like the majority of industrial processes, the operation of the current and proposed WWTP in Courtown is faced with the issue of controlling odours causing impact to the public at large. In order to obtain site specific odour emission data for the site, an odour audit was performed in May 2004 utilising odour sampling and measurement techniques in accordance with PrEN13725:2003 European Standard on Olfactometry. This odour emission data was compared with library odour emission data. As the proposed upgrade to the WWTP may be procured as a Design/Build/Operate (DBO) project, quantifying future odour emissions from the site must cover a range of possible treatment processes. Ryan Hanley consulting engineers 49 December 2005 EPA Export :22:46:04

52 Therefore, utilising an indicative design and both site specific and library odour emission data; dispersion modelling techniques were used to establish maximum allowable odour emission rates from the proposed site in order to limit any odour impact on the surrounding population. The Odour Monitoring Ireland report suggests an odour impact criterion of 3.0 Ou E m -3. It recommends that all residential dwellings should be located outside the 3 Ou E m -3 contour for the 98 th percentile in one worst case meteorological year as determined by atmospheric dispersion modelling software. Methodology Data Collection In order to obtain point source air samples for odour assessment, a static sampling method was used where air samples were collected in 60 litre pre-conditioned Nalophan NA bags using a vacuum sampling device over a thirty-minute period. The sampler operates on the 'lung principle', whereby the air is removed from a rigid container around the bag by a battery powered SKC vacuum pump at a rate of 2 l min -1. This caused the bag to fill through a stainless steel and PTFE tube whose inlet is placed in the odour stream, with the volume of sample equal to the volume of air evacuated from the rigid container. In order to measure the odour emission rate from lagoon and area odour surfaces a calibrated wind tunnel method was used. This calibrated sampling hood allowed for the accurate determination of odour emission rate from the surface of the tanks. In combination with the point source static sampling method a 60-litre sample over a thirtyminute period was obtained (Jiang et al., 2002). Methodology Modelling The model used to examine the scenarios considered for the Courtown WWTP site is BREEZE Industrial Source Complex (ISC ST Ver ). This model is recommended in Environmental Protection Agency (EPA) guideline on Air Quality Modelling for applications to refinery-like sources and other industrial sources. It is used with meteorological input data from the nearest representative source. The most important parameters needed in the meteorological data are wind speed, wind direction, ceiling heights, cloud cover, and Pasquill-Gifford stability class for each hour. ISC ST 3 (Ver ) is run with a sequence of hourly meteorological conditions to predict concentrations at receptors for averaging times of one hour up to a year. It is necessary to use many years of hourly data to develop a better understanding of the statistics of calculated short-term hourly peaks or of longer time averages. Three years of hourly sequential meteorology data was used for the operation of ISC ST 3. This allowed for the determination of the worst-case meteorological year for the determination of overall odour impact from the proposed Courtown WWTP design on the surrounding population. All significant deviations in terrain are examined in modelling computations through terrain incorporation using AerMap software. All building wake effects are accounted for in the modelling scenarios (i.e. building effects on point sources) as this can have a significant effect on the odour plume dispersion at short distances. Ryan Hanley consulting engineers 50 December 2005 EPA Export :22:46:04

53 Three data sets for odour emission rates were calculated to determine the potential odour impact of the current and proposed WWTP operation and design utilising site specific and library individual source odour emission data. Individual source modelling was performed in order to assess which odour source contributed greatest to the odour impact area. The 3 scenarios modelled were as follows: Scenario 1: Predicted overall odour emission rate from current Courtown WWTP. Scenario 2: Predicted overall odour emission rate from proposed Courtown WWTP design without the incorporation of odour abatement protocols. Scenario 3: Predicted overall odour emission rate from proposed Courtown WWTP design with the incorporation of considered odour abatement protocols Existing Environment No elevated ambient H 2 S concentrations were detected in the vicinity of the currently operated WWTP on the day of monitoring with all levels within the recommended WHO guideline value. The plotted odour concentrations of 3.0 Ou E m -3 for the 98 th percentile for the current Courtown WWTP operation is illustrated in Figure 3-3. As can be observed, it is predicted that odour plume spread will have a radial spread of 600 metres. In keeping with currently recommended odour annoyance criterion in this country, no significant odour impact should be perceived by residents in the vicinity of the currently operating WWTP. Some complaints may be registered during warm summer peak emission months. It was concluded that the current operating WWTP should not cause any significant odour impact even though some odour complaints may be registered due to cyclic puff emissions from the sludge handling processes within the plant. Ryan Hanley consulting engineers 51 December 2005 EPA Export :22:46:04

54 Figure 3-3. Predicted odour emission contribution of current Courtown WWTP operation to odour plume dispersal for Scenario 1 at the 98 th percentile for odour concentrations 3.0 Ou E m -3 ( ). Ryan Hanley consulting engineers 52 December 2005 EPA Export :22:46:04

55 Characteristic of the Plant Upgrade It is proposed to extend the wastewater treatment plant at Courtown to provide additional capacity to treat all foul loads arising at Gorey and to cater for the sludge dewatering requirements for the Gorey Sludge Satellite area as set out in the Wexford Sludge Management Study (Draft Final Report), March The extended WWTP at Courtown will be designed to treat the wastewater from a population equivalent (PE) of 45,000. The plant will have sludge reception facilities to accept imported sludges from a population equivalent of 15,000 from treatment plants in the Gorey area. Sludge thickening and dewatering facilities will be provided to achieve a sludge with a dry solids content of 20% for all sludges on site, i.e. for a 60,000 PE. Dewatered sludge will be transported off site to the Wexford Sludge Hub at the Wexford WWTW. The size of the extended WWTP will be in the order of that shown in the indicative layout (Drawing No. 1757/003 Rev C, Appendix A). The procurement of the new works may proceed as a DBO contract. Thus, alternative designs and processes may be permitted at the detail design stage of the project provided that they are within the constraints set out in this EIS and any other requirements by Wexford County Council. It is anticipated that some or all of the following additional structures or similar will be required: - Modification to the inlet works with a top level up to 31.5mOD. The modified inlet works will replace/augment the existing inlet works, which has a top level of 28.5mOD. - Additional process tanks with top levels up to 27.0 mod to the north west of the existing aeration tanks. - Additional process tank to have a top level of mod to the north west of the aeration tanks. - Additional process tanks beside (to the north east of) the aeration tanks with top levels up to 26.0 mod. The existing aeration tanks have a top level of approximately 25.5mOD. - Additional process tanks beside (to the north east of) the existing final settlement tanks with top levels up to 25.5 mod. The existing final settlement tanks have a top level of approximately 24.6mOD. - Additional sludge tanks in the western corner of the site up to 29.5 mod. They will replace the existing sludge thickening tank, which has a top level of 27.5 mod. - An extension to the existing dewatering building (ridge level 30.5 mod) and the provision of a new dewatered sludge storage building of plan area up to 300m² and a ridge level of approximately 32.0 mod, adjacent to the dewatering building. All of the above tankage and plant was included in the odour impact modelling to cover a worst-case scenario. Ryan Hanley consulting engineers 53 December 2005 EPA Export :22:46:04

56 Courtown WWTP Extension - Environmental Impact Statement Co ns en to f c Fo op r i yr ns ig pe ht ct ow ion ne pu r r rp eq os ui es re o d nl fo y. ra ny ot he ru se. Potential Impact of the Proposal The plotted odour concentrations of 3.0 OuE m-3 for the 98th percentile for the proposed Courtown WWTP operation without any abatement measures is illustrated in Figure 3-4. As can be observed, it is predicted that odour plume spread is significant with approximately 24 residents perceiving an odour concentration greater than 3.0 OuE m-3 at the 98th percentile. In keeping with currently recommended odour annoyance criterion in this country, numerous complaints may be registered by residents living in the vicinity of the proposed WWTP, if it is operated without implementation of odour abatement measures. Figure 3-4. Predicted odour emission contribution of proposed overall Courtown WWTP operation without odour abatement protocols implemented to odour plume dispersal for Scenario 2 at the 98th percentile for odour concentrations 3.0 OuE m-3 ( ). Ryan Hanley consulting engineers 54 December 2005 EPA Export :22:46:04

57 3.5.3 Mitigation Measures Odour abatement and minimisation procedures will be required at the proposed wastewater treatment plant in order to prevent any odour nuisance in the surrounding vicinity. Phase I (WWTP increase to 35,000PE) The predicted overall odour emission rate from future Courtown WWTP Phase I design (35,000PE) with the incorporation of odour abatement protocols is summarised in Table Note: Source identity Exposed area (m 2 ) Volumetric airflow rate (m 3 s -1 ) Odour emission flux (Ou E m -2 s -1 ) Odour emission rate (Ou E s -1 ) % of odour emission contributio n (%) Inlet works (including flow channels, grit chamber, grit storage containers and inlet sewer line flow) 1 Primary settlement tanks 1 and Aeration tanks 1, 2, 3, 4, 5 and Final settlement tanks 1, 2 and Sludge thickening tank Dewatered sludge storage Sludge blending tank Sludge dewatering building Sludge reception tank Ou E m Ou E m Total , Table 3-35 Predicted overall odour emission rate from future Courtown WWTP Phase I design (35,000PE) with the incorporation of odour abatement protocols. 1 denotes installation of odour abatement system achieving an odour removal efficiency of at least 90%. The total combined odour emission rate from the odour abatement system should not be greater than 186 Ou E s -1. The volumetric air flow from the emission processes should be sufficient to capture and maintain each process under slight negative pressure. A stack height of 4 metres and efflux of 10 m s -1 was used within the dispersion model; 2 denotes installation of odour abatement system taking into consideration the cyclic odour flow from these sludge handling processes. The combined odour emission rate from the odour abatement system should be no greater than 1150 Ou E s -1. The volumetric airflow should be sufficient to contain and capture and odour emissions from these processes. Usually, the maximum filling rate of a tank including headspace and an air exchange rate of 8 air changes per hour should be attained. This will also maintain good air quality within the sludge dewatering building. If the building is sealed and good management practices are incorporated into the design (hood extraction and negative ventilation around dewatering equipment), this air exchange rate can be reduced. A stack height of 5 metres and efflux velocity of 10 m s -1 was used for a sludge process abatement system within the dispersion model. 3 denotes that sludge storage skips are tightly sealed and maintained in clean conditions. Ryan Hanley consulting engineers 55 December 2005 EPA Export :22:46:04

58 Phase II (WWTP increase to 45,000PE) The predicted overall odour emission rate from future Courtown WWTP Phase II design (45,000PE) with the incorporation of odour abatement protocols is summarised in Table Note: Source identity Exposed area (m 2 ) Volumetric airflow Rate (m 3 s -1 ) Odour emission flux (Ou E m -2 s -1 ) Odour emission rate (Ou E s -1 ) % of odour emission contribution (%) Inlet works (including flow channels, grit chamber, grit storage containers and inlet sewer line flow) 1 Primary settlement tanks 1 and Aeration tanks 1, 2, 3, 4, 5 and Final settlement tanks 1, 2 and Anoxic tank Flow splitter chamber Sludge thickening tank Sludge blending tank Sludge dewatering building Sludge reception tank Ou E m Ou E m Dewatered sludge storage building Ou E m Total , Table 3-36 Predicted overall odour emission rate from future Courtown WWTP design (45,000PE) with the incorporation of odour abatement protocols 1 denotes installation of odour abatement system achieving an odour removal efficiency of at least 95%. The total combined odour emission rate from the odour abatement system should not be greater than 112 Ou E s -1. The volumetric air flow from the emission processes should be sufficient to capture and maintain each process under slight negative pressure. A stack height of 5 metres and efflux of 15 m s -1 was used within the dispersion model; 2 denotes installation of odour abatement system taking into consideration the cyclic odour flow from these sludge handling processes. The combined odour emission rate from the odour abatement system should be no greater than 1393 Ou E s -1 (i.e. Odour emission contribution from sludge handling processes and primary settlement tanks). The volumetric airflow should be sufficient to contain and capture and odour emissions from these processes. Usually, the maximum filling rate of a tank +void volume and an air exchange rate of 8 air changes per hour should be attained on smaller tanks and contaminated process buildings, respectively. If any process air is added to the process then this should also be accounted for in the process (For example: A tank volume of 400 m 3 + a fill rate of 300 m 3 hr -1 + process air of 1000 m 3 hr - 1, then the volume to be removed will be equal to 1700 m 3 hr -1 and should be equally distributed across the surface of the tank to prevent zones of positive pressure). This will also maintain good air quality within the sludge dewatering building/dewatered sludge storage building. If the building is sealed and good management practices are incorporated into the design (hood extraction and negative ventilation around dewatering equipment), this air exchange rate can be reduced. A stack height of 5 metres and efflux velocity of 15 m s -1 was used for a sludge process abatement system within the dispersion model. 3 denotes that sludge storage skips are tightly sealed and maintained in clean conditions. Negative ventilation should be applied to the sludge skip storage building if any significant contamination of the building headspace occurs. With regard to the level of ventilation required, it will be dependent on the practices of the operator (possibly a DBO contractor) i.e. whether the skips, when in the building, are open, covered or sealed airtight. The preferred method would be to constrain the total odour emissions from the building (after abatement) so that the operator has the choice to operate within the building in his preferred method. Sludge storage skips will have to tightly sealed before leaving the building. 4 denotes both primary tanks will be covered leaving a total interfacial area of 0 m 2 exposed. Ryan Hanley consulting engineers 56 December 2005 EPA Export :22:46:04

59 The following odour abatement measures are proposed for the extended Courtown WWTP based on the predicted overall odour emission: 1. Odour scrubbing technologies will be installed on the inlet works and all sludge handling processes within the WWTP. Odours from these areas are considered more offensive than primary/secondary sedimentation and aeration processes and therefore more likely to cause odour complaints. 2. Odour scrubbing should also be performed from the primary settlement tanks*. 3. The maximum allowable odour emission rate from the overall WWTP should not be greater than 11,845 Ou E s -1 (see Table 3.4, Appendix D) inclusive of the odour emission contribution from the abatement systems installed on the inlet works and sludge handling processes (i.e. see Table 3.4-sludge handling odour control unit will handle process odourous air from the primary settlement tanks also). The maximum overall odour emission rate from the inlet works and combined sludge handling processes shall be no greater than 112 and 1,393 Ou E s Good housekeeping practices shall be implemented at the site (i.e. yard areas to be kept clean, etc.), closed-door management strategy (i.e. to eliminate puff odour emissions from sludge dewatering building), maintain sludge storage within enclosed ventilated buildings or sealed airtight containers and an odour management plan for the operators of the WWTP will be implemented (i.e. for preventative maintenance of odour abatement systems). 5. Accumulation of floating debris and persistent sediments in channels and holding tanks will be avoided by good design (i.e. flow splitters and secondary sedimentation tanks, etc.) 6. Sludge process/conditioning tanks, sludge handling processes and sludge acceptance and transfer processes shall be enclosed and sealed. 7. The proposed WWTP should be operated within specifications to eliminate overloading and under loading, which may increase septic conditions within the anoxic/aeration basins. * A simulation of the Phase I plant (35,000PE) as detailed in Table 3-35 showed that the odour scrubbing proposed at the primary settlement tanks will not be required for the Phase I load. The dispersion modelling undertaken as part of Odour Impact Study is valid for the indicative design discussed within this document. If overall odour emission rates from the actual designed WWTP increase from that of the indicative design, the actual WWTP design will be required to be assessed to ensure compliance with the odour limits. A limit of 3.0 Ou E m -3 at the 98 th percentile should be adopted as an odour limit at the nearest sensitive locations to the plant. Ryan Hanley consulting engineers 57 December 2005 EPA Export :22:46:04

60 3.5.4 Impact of the Proposal Following WWTP up-grade and installation of odour abatement measures, it is predicted all residences in the vicinity of the WWTP will perceive an odour concentration less than 3.0 OuE m -3 at the 98 th percentile in a worst case meteorological year. This is in accordance with currently recommended Irish Environmental Protection Agency maximum perceived ground level concentrations to limit odour nuisance. Figure 3-5. Predicted odour emission contribution of proposed overall Courtown WWTP operation with odour abatement protocols implemented to odour plume dispersal for Scenario 3 at the 98 th percentile for odour concentrations 3.0 Ou E m -3 ( ). Ryan Hanley consulting engineers 58 December 2005 EPA Export :22:46:04

61 The plotted odour concentrations of 3.0 Ou E m -3 for the 98 th percentile for the proposed Courtown WWTP (45,000PE) operation with abatement measures implemented is illustrated in Figure 3-5. As can be observed, it is predicted that odour plume spread is greatly reduced with all residents in the vicinity of the proposed WWTP perceiving an odour concentration less than 3.0 Ou E m -3 for the 98 th percentile. In keeping with currently recommended odour annoyance criterion in this country, no significant odour impact should be perceived by residents in the vicinity of the proposed operating WWTP. Those sources considered most offensive have been abated and therefore it is less likely that any resident will complain (see Table 3.1, Appendix D). Monitoring Following commissioning of the extended Courtown WWTP, the odour levels at the nearest sensitive locations to the plant will be verified by an approved expert in odour measurement. The Performance Management System (PMS) for the operation stage of project includes a procedure to deal with complaints by members of the public, should they arise. 3.6 AIR QUALITY - NOISE Introduction Biospheric Engineering Ltd. carried out an assessment relating to noise emissions from the existing and proposed Wastewater Treatment Plant (WWTP) in June The full text of their report is included in Appendix E. The purpose of the assessment is to provide existing background noise levels resulting from the operation of the plant and indicate the potential impact of increasing the capacity of the plant on the noise emissions. A study of noise emission levels was carried out on the 17 th of June 2004, measuring environmental noise at the boundary of the WWTP at the nearest noise sensitive location during the daytime. A corresponding set of measurements were carried out during the night time, with the exception of the perimeter of the plant which was not accessible. (Daytime being defined by the Environmental Protection Agency as 08:00 hrs to 22:00 hrs, with night time defined as 22:00 hrs to 08:00 hrs). Future noise levels were estimated and recommendations made to mitigate the impact of noise sources within the site. Characteristic of the Proposal It is proposed to extend the WWTP by addition of settlement and/or aeration capacity in addition to sludge thickening and dewatering equipment. The extended WWTP will be of the order of that shown in the indicative layout (Drawing 1757/003 Rev C, Appendix A). It is proposed that all machines with high or medium noise generating potential will be enclosed in noise attenuation equipment which will limit noise to 70dBA at 1 metre from the equipment and that all such equipment will be located within buildings with a high sound insulation level which will limit consequent noise levels to 45dBA at the nearest site boundary. Ryan Hanley consulting engineers 59 December 2005 EPA Export :22:46:04

62 Methodology Measurements were taken using a Bruel & Kjaer model 2260 type 1 sound level meters equipped with modular real-time noise analysis software BZ7210. During measurement the height of the microphone was 1.5 metres above ground and was equipped with an outdoor microphone kit model UA The monitoring locations chosen were determined by the geographical location of the treatment plant. Local factors included maintaining separation from reflecting surfaces and other noise sources while establishing the most representative monitoring point to reflect the noise climate at that site. Noise measurements were taken in accordance with International Standards Organisation Standard: ISO 1996 Acoustics Description and Measurement of Environmental Noise. The measurements were taken in attended mode and there were no adverse weather conditions that were likely to interfere with the results during the monitoring period. Other noises noted during the monitoring period were Traffic on the R742 Gorey Road, birdsong, aircraft, construction work and domestic noises such as grass cutting and dogs barking Existing Environment The Wastewater Treatment Plant is located to the northwest of Courtown in an area enclosed by woodlands on three sides. The location can be described as remote from residential areas and well screened by the adjoining woodlands. The site is accessed from a local road which has a high level of traffic. The treatment works includes a number of standard plant items associated with Wastewater Treatment Plants. The process includes initial screening and filtering, aeration, sludge settlement, sludge thickening and associated pumping works. All equipment on the site that has a potential to generate significant noise is located either indoors or in an acoustic enclosure. The hours of operation for WWTPs are 24 hours per day, 7 days per week, i.e. continuous operation. The WWTP itself is set back from the road and located on an elevated site but not at the crest of a hill. The site is effectively cut into the side of the hill thus providing effective screening to the North and Northwest directions. The woodlands provide screening to the other sides of the site. The plant is quiet in operation. On the date the measurements were taken the plant was inaudible at two of the site boundaries (South and East) while being barely audible at the other two locations. Noise measurements taken on the site close to the noise sources indicate that there are no particularly noisy sources on site. The sources with the greatest potential for noise emissions such as the blowers, pumps, etc are located indoors or in acoustic enclosures. These mitigation measures are effective in ensuring quiet 24 hour operation of the plant. Ryan Hanley consulting engineers 60 December 2005 EPA Export :22:46:04

63 Equipment Sound Pressure Level L 2 meters db(a) Estimated equivalent continuous sound pressure level L Aeq at site boundary db(a) Primary Settlement Tank Screen Area Screen Area Aeration Bed inlet Aeration Bed Aeration Bed Aeration Bed Aeration Bed Aeration Bed outlet Sludge Return pumping chamber Outside Blower hut Settlement Tank Settlement Tank Sludge Press (external) Water Pressurisation Pump (internal) Control Room Table 3-37: Noise Emissions from the Principal Noise Sources on Site Noise emissions from the principal noise sources on site are outlined in Table Values are calculated for distance to nearest site boundary and allowing for enclosure where appropriate. The predicted noise levels at the site boundary are confirmed by measurement indicating that boundary noise levels are within recommended limits. The nearest noise sensitive location is the residence to the Southwest and readings were taken at the rear entrance gate to this site. The WWTP was inaudible at this location. The Environmental Protection Agency have adopted an environmental Noise Limit value of 55 db(a) during the day period [08.00 hrs to hrs]and 45 db(a) during the night period [22.00 hrs to hrs]. As the plant operates on a 24-hour basis the significant criteria is the night time value of 45 db(a) at the nearest noise sensitive location. Noise measurements were taken at 5 locations adjacent to the Courtown WWTP as shown in Figure 3-6. A summary of the noise levels measured is outlined in Table Ryan Hanley consulting engineers 61 December 2005 EPA Export :22:46:04

64 Location Reference Figure 3-6 Noise measurement locations at Courtown WWTP Location Day L Aeq (30 m) db(a) Day L A90 (30 m) db(a) Night L Aeq (15 m) db(a) Pt 1 WWTP South Pt 2 WWTP West Pt 3 WWTP North Night L A90 (15 m) db(a) Pt 4 WWTP East Pt 5 Noise Sensitive Location Recommended Maximum (EPA) Table 3-38 Recorded noise levels at locations adjacent to the Courtown WWTP The cumulative noise level at the Southern and Eastern boundaries of the WWTP are above 45 db(a), due to traffic levels on the R742. The specific noise attributable to the WWTP (as evidenced by the continuous nature of the noise in the L 90 value in Table 3-38) is below the EPA guideline level. (L 90 is the noise level exceeded for 90% of the time). The levels at the other sites are below 45 db(a). Ryan Hanley consulting engineers 62 December 2005 EPA Export :22:46:04

65 At each of the sites the equipment in the treatment plant is audible. The equipment can be regarded as operating within EPA guideline noise values even though the noise is audible under quiet conditions. The background noise level in the absence of traffic noise and any noise from the treatment works (a condition that does not arise) is likely to be of the order of 35 db(a). Equipment noise emissions from the WWTP are of the order of 38 db(a). The combined noise level, without the consideration of any local traffic noise, is around 40 db(a) and the equipment noise is just audible above the background. Based on ⅓ octave analysis of the noise at all locations there is no audible tonal emission from the WWTP. As demonstrated from the measurement results outlined above the existing noise reduction measures employed on site are successful Impact on noise level On the basis of the noise emissions of the existing equipment and the existing noise levels adjacent to the site, indicative noise prediction maps have been prepared indicating the current noise impact and the future noise impact of adding the additional equipment at the WWTP (Figure 3-7 and Figure 3-8). It is estimated that the noise impact of the additional equipment will be an increase of about 3 db. This slight increase will have no significant impact on noise emission levels at the site boundary and will have no impact at the nearest noise sensitive location. Courtown WWTP Figure 3-7 Courtown WWTP Predicted Daytime Noise (Existing) Ryan Hanley consulting engineers 63 December 2005 EPA Export :22:46:04

66 Courtown WWTP Figure 3-8 Courtown WWTP Predicted Daytime Noise (Proposed) Impact of Project Construction During the construction stage of the project there will be noise from construction plant and construction operations. This noise will slightly affect lands adjoining the wastewater treatment plant site on a temporary basis. The criteria applicable to the permanent works will not apply at the construction stage on account of the temporary nature of the works. As the works will be carried out during day light hours the construction will not impinge to any extent on night time noise levels Mitigation Measures It is proposed that all machines with high or medium noise generating potential will be enclosed in noise attenuation equipment which will limit noise to 70dBA at 1 metre from the equipment and that all such equipment will be located within buildings with a high sound insulation level which will limit consequent noise levels to 45dBA at the nearest site boundary. On completion of the project, it is estimated that the noise impact of the additional equipment will be an increase of about 3 db. This slight increase will have no significant impact on noise emission levels at the site boundary and will have no impact at the nearest noise sensitive location. In addition, regular maintenance of silencers and enclosures should be carried out to minimise noise emission levels and WWTP equipment should not be left idling when not in operation Ryan Hanley consulting engineers 64 December 2005 EPA Export :22:46:04