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HomeMy WebLinkAbout2660156 - F.I. Received Doc. - SuDS 26/446 TE 2nd September 2026 Derek Niblock c/o Moffet Architectural Corlea, Ballybay, Co. Monaghan Re: Comprehensive Sustainable Drainage Systems Assessment and Stormwater Attenuation Design for Agricultural Development at Aghnaclea, Ballybay, Co. Monaghan. Dear Sir/Madam, Traynor Environmental Ltd. has been retained by the applicant to prepare a comprehensive Sustainable Drainage Systems (SuDS) Assessment and Surface Water Management Strategy for the proposed agricultural development at Aghnaclea, Ballybay, Co. Monaghan. This report has been prepared having regard to the principles of Sustainable Drainage Systems (SuDS), the CIRIA SuDS Manual C753 and relevant guidance relating to nature-based solutions for the management of rainwater and surface-water runoff. The assessment considers runoff quantity and quality, pollution prevention, source and site control, attenuation, exceedance management, protection of the receiving environment, and the segregation and management of clean and soiled water. Site-specific infiltration testing was undertaken to assess the suitability of managing clean surface water by infiltration. The testing identified relatively slow infiltration characteristics, with the recorded fall between the 75% and 25% effective test levels occurring over approximately 15 hours. Consequently, reliance on a conventional soakaway as the principal means of surface-water disposal was not considered appropriate for the proposed development. The final surface-water management strategy therefore provides for the collection, appropriate treatment and attenuation of surface-water runoff prior to controlled discharge to the existing drainage outfall identified on the proposed site-services layout. The attenuation and drainage calculations have been undertaken using site-specific rainfall parameters and assess storm events up to and including the 1 in 100-year return-period event incorporating a 20% climate-change allowance. The allowable discharge from the development has been established with reference to the pre - development greenfield runoff characteristics of the site. The IH124 assessment is based on a positively drained greenfield area of 1.639 ha, SAAR of 1,002 mm, Soil Index 4 and SPR of 0.47, resulting in a calculated greenfield QBar of 12.0 L/s. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Accordingly, discharge from the proposed attenuation system will be restricted by a Hydro-Brake, or equivalent approved vortex flow-control device, to a maximum design flow of 12.0 L/s. The proposed attenuation system has been incorporated into the final surface-water drainage calculations to demonstrate that runoff generated by the proposed development can be appropriately managed prior to controlled discharge to the existing receiving drainage network. The final Hydro-Brake calculation specifies a design flow of 12.0 L/s. The proposed drainage strategy does not rely upon infiltration to ground to achieve the required attenuation performance. The final calculations adopt zero infiltration through the base and sides of the attenuation system, with runoff managed through temporary storage and controlled discharge. Introduction Traynor Environmental Ltd. has been appointed to prepare a comprehensive Sustainable Drainage Systems (SuDS) Assessment and Surface Water Management Strategy for the proposed agricultural development at Aghnaclea, Ballybay, Co. Monaghan. The proposed development comprises the construction of 1 No. poultry house and 1 No. manure store, together with associated ancillary structures including meal storage bin(s), soiled -water storage tank(s), access arrangements, drainage infrastructure, landscaping and associated site-development works. The purpose of this report is to set out the proposed strategy for the management of surface water arising from the development and to demonstrate that clean surface water and potentially contaminated water will be managed through separate drainage systems. The assessment considers the collection, appropriate treatment, attenuation and controlled discharge of surface-water runoff, together with pollution-prevention measures to protect groundwater, surface water, existing drainage features and downstream environmental receptors. The proposed drainage strategy has been developed in accordance with SuDS principles and provides for the management of surface water through a combination of source control, segregation of clean and soiled water, appropriate pre-treatment, attenuation, controlled discharge and exceedance management. The final drainage arrangement provides for surface water to be conveyed to the proposed attenuation system before discharge through a Hydro-Brake, or equivalent approved flow-control device. The discharge will be restricted to the calculated pre-development greenfield QBar of 12.0 L/s before being conveyed to the existing drainage outfall. Site Location The proposed development is located at Aghnaclea, Ballybay, Co. Monaghan, within a rural agricultural setting surrounded predominantly by agricultural lands and dispersed rural development. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The subject site comprises agricultural lands upon which the proposed poultry house, manure store and associated infrastructure are to be constructed. Access to the development will be provided from the adjoining local road via the proposed site entrance and internal access arrangement shown on the site layout. The proposed drainage strategy has been developed having regard to the final development layout, existing topography, drainage characteristics and operational requirements of the proposed poultry development. Particular consideration has been given to the management of clean roof water and uncontaminated surface-water runoff, segregation of clean and soiled-water drainage systems, pollution prevention, attenuation and protection of groundwater and downstream surface-water receptors. Clean roof water and uncontaminated surface-water runoff will be collected through the dedicated surface-water drainage network and conveyed towards the proposed attenuation system. Runoff from areas presenting a potential sediment or hydrocarbon pollution risk will receive appropriate pre- treatment before discharge to the attenuation system. Following attenuation, surface water will be discharged through a Hydro-Brake, or equivalent approved vortex flow-control device, at a maximum design rate of 12.0 L/s before being conveyed to the proposed outfall identified on the final surface-water drainage layout. The final drawing, Drawing No. 26-446-100, identifies the proposed surface-water sewer arrangement and outfall. Soiled water, wash water and other potentially contaminated water associated with the operation and cleaning of the poultry development will be collected separately and directed to the dedicated soiled- water storage system. No soiled water or potentially contaminated agricultural wash water will be permitted to enter the clean surface-water drainage system, attenuation system or receiving drainage network. The location of the proposed development site and surrounding lands is illustrated in Figure 1. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Figure 1: Site Location Site Description The proposed development is located at Aghnaclea, Ballybay, Co. Monaghan, within a rural agricultural setting. The site and surrounding lands are predominantly agricultural in character, with dispersed residential development and agricultural holdings in the wider area. The proposed development area comprises agricultural land on which the poultry house, manure store, ancillary structures, access arrangements and associated drainage infrastructure are to be constructed. The site layout and available topographical information have been considered in the development of the proposed surface-water management strategy. The drainage system has been arranged to collect surface-water runoff generated by the proposed development and convey it through a dedicated drainage network towards the proposed attenuation system. Clean roof water and uncontaminated surface-water runoff will be managed separately from soiled water and other potentially contaminated water generated through the operation of the poultry development. Runoff from areas presenting a potential risk of sediment or hydrocarbon contamination will receive appropriate treatment prior to entering the attenuation system. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The proposed attenuation system will provide temporary storage of surface-water runoff during rainfall events before releasing it at a controlled rate to the existing drainage outfall identified on the site layout. The system has been developed having regard to the site infiltration characteristics, contributing drainage catchment and calculated runoff generated by the proposed development. The drainage design has been developed having regard to the existing site levels and drainage characteristics, with the objective of managing runoff in a controlled manner while minimising the potential for increased downstream flood risk or deterioration in water quality. The proposed site layout, surface-water drainage infrastructure, attenuation system and existing drainage outfall are illustrated in Figure 2. Figure 2: Site Layout Proposed Development The proposed development comprises the construction of 1 No. poultry house and 1 No. manure store, together with associated ancillary structures including meal storage bin(s), soiled -water storage tank(s), access arrangements, drainage infrastructure and associated site works. The development will result in the creation of new roof and hardstanding areas and consequently an increase in the rate and volume of surface-water runoff generated during rainfall events. A dedicated surface-water drainage system is therefore proposed to collect, appropriately treat, attenuate and control the discharge of surface water arising from the development. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The drainage strategy provides clear segregation between clean surface water and soiled water associated with the operation of the poultry unit. Clean roof water and uncontaminated runoff will be conveyed through the surface-water drainage system towards the proposed attenuation system, while soiled water, wash water and other potentially contaminated agricultural water will be directed to dedicated storage facilities and will not be permitted to enter the clean surface-water drainage system. The final drainage arrangement provides for temporary attenuation of runoff before controlled discharge to the existing drainage outfall. The detailed drainage design, attenuation requirements and flow-control arrangements are set out in the subsequent sections of this report. Planning Status and Purpose of this Report A planning application has been submitted to Monaghan County Council for the proposed agricultural development at Aghnaclea, Ballybay, Co. Monaghan. Following its assessment of the application, Monaghan County Council requested Further Information in relation to the proposed surface-water drainage arrangements. In particular, the Planning Authority requested clarification regarding the previously proposed soak-pit and demonstration that the proposed drainage solution is appropriate to the site ground conditions and will not adversely affect water quality. The Planning Authority also requested revised storm-water drainage proposals incorporating consideration of nature-based solutions, together with a revised site layout identifying the storm-water drainage network, direction of flow and proposed discharge/outfall locations. In response to the Further Information request, further assessment of the proposed means of surface - water management has been undertaken. Site-specific infiltration testing identified relatively slow infiltration characteristics, with the water level taking approximately 15 hours to fall between the 75% and 25% effective test levels. Having regard to the observed infiltration characteristics and the runoff generated by the proposed development, reliance upon a conventional soakaway as the principal means of surface-water disposal was not considered appropriate. Accordingly, the previously proposed soakaway has been omitted from the revised drainage strategy and superseded by a system based on collection, appropriate treatment, attenuation and controlled discharge. The final surface-water drainage arrangement has been assessed using dedicated drainage and attenuation calculations. These calculations consider the proposed contributing drainage areas, site - specific rainfall characteristics, applicable design storm events and an allowance for climate change. Surface water is temporarily stored within the proposed attenuation system before being released through a flow-control chamber incorporating a Hydro-Brake, or equivalent approved device, and conveyed to the existing drainage outfall. The allowable discharge has been established with reference to the calculated pre -development greenfield runoff rate. The final calculations establish a greenfield QBar of 12.0 L/s, which has been REC E I V E D : 1 7 / 0 9 / 2 0 2 6 adopted as the maximum design discharge from the attenuation system. The proposed Hydro-Brake has accordingly been specified for a design flow of 12.0 L/s. The revised drainage strategy also incorporates appropriate runoff treatment and pollution-prevention measures, including silt/sediment management and hydrocarbon treatment where required. Clean surface water and soiled water will be managed through separate drainage systems, with soiled water, wash water and other potentially contaminated runoff prevented from entering the clean surface-water drainage network, attenuation system or receiving drainage outfall. The purpose of this report is therefore to provide a comprehensive Sustainable Drainage Systems (SuDS) Assessment and Surface Water Management Strategy for the proposed development and to demonstrate how the revised drainage proposals address the matters raised in the Further Information request. The assessment considers runoff quantity and quality, pollution prevention, source control, treatment, attenuation, controlled discharge, exceedance management, nature-based drainage principles and the protection of groundwater, existing drainage features and downstream receiving waters. The detailed response to the individual surface-water drainage matters raised in the Further Information request is provided in the following sections of this report and illustrated on the accompanying revised drainage layout. Receiving Watercourses and Drainage Pathways The proposed surface-water management strategy has been developed having regard to the existing drainage characteristics of the site, the local field drainage network, the proposed development layout and the downstream receiving-water environment. The drainage strategy incorporates collection, pollution prevention, appropriate treatment, attenuation and controlled discharge to ensure that runoff generated by the proposed development is appropriately managed prior to leaving the site. The principal downstream surface-water receptor identified in the vicinity of the development is the Dromore_36 River (Waterbody Code: IE_NW_36D020090), located approximately 618 m south of the proposed development site. Two existing drainage features have been identified in the vicinity of the proposed development which form part of the local drainage network towards the Dromore_36 River. An existing drain is located along the western boundary in the vicinity of the site entrance, while a second existing drain is located along the southern boundary of the site. The southern boundary drain has been identified as the receiving drainage feature for the proposed controlled surface-water discharge, with the associated outfall identified on the final drainage layout. The proposed development will introduce additional impermeable surfaces associated with the poultry house, manure store and associated concrete apron, hardstanding and operational areas. In the REC E I V E D : 1 7 / 0 9 / 2 0 2 6 absence of appropriate attenuation and flow control, runoff from these surfaces could result in an increased rate of discharge to the existing drainage network. Accordingly, the proposed drainage strategy does not provide for unrestricted discharge from the developed site to the existing southern boundary drain. Surface water will instead be collected within a dedicated drainage network and managed through appropriate treatment, attenuation and flow- control measures prior to discharge. Clean roof water and uncontaminated surface-water runoff will be collected through the proposed surface-water drainage network. Runoff from areas presenting a potential sediment or hydrocarbon pollution risk will receive appropriate treatment prior to entering the attenuation system. Following attenuation, surface water will be released through a flow-control chamber incorporating a Hydro-Brake, or equivalent approved vortex flow-control device, before being conveyed to the proposed outfall to the existing open drain. The final drainage calculations establish a maximum controlled discharge rate of 12.0 L/s, corresponding with the calculated pre-development greenfield QBar. The proposed arrangement therefore retains the existing southern boundary drainage feature as the receiving drainage pathway while providing attenuation and flow control between the developed catchment and the receiving network. This will limit the rate at which runoff from the proposed development enters the downstream drainage system. A fundamental component of the drainage strategy is the segregation of surface water from soiled and potentially contaminated agricultural water. Soiled water, wash water and other contaminated water associated with the operation and cleaning of the poultry development will be collected and managed through a separate drainage and storage system. Such water will not be permitted to enter the clean surface-water drainage network, attenuation system, existing field drains or downstream receiving waters. During rainfall events exceeding the design capacity of the formal drainage system, exceedance runoff will be managed having regard to the existing and proposed site topography. Exceedance flows will, insofar as practicable, be directed away from buildings, sensitive areas, neighbouring property and areas where potentially contaminating material could be mobilised. Overall, the proposed drainage strategy establishes a managed and controlled connection between the proposed development and the existing southern boundary drainage network. The combination of clean and soiled-water segregation, appropriate runoff treatment, attenuation, flow control and exceedance management will minimise the potential for adverse effects on the existing drainage network and downstream Dromore_36 River. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Surface Water Drainage The proposed surface-water management strategy has been developed using a Sustainable Drainage Systems (SuDS) approach to ensure that runoff generated by the proposed development is appropriately collected, treated where required, attenuated and discharged in a controlled manner. The strategy seeks to manage runoff close to source, minimise any increase in downstream flood risk and protect surface water, groundwater and downstream environmental receptors. The drainage design has been informed by site-specific conditions including the proposed development layout, topography, existing drainage pathways, soil and infiltration characteristics, agricultural operational requirements and the location of downstream drainage and surface-water receptors. The adopted drainage strategy is based on the SuDS principles of prevention, source control, treatment, site control and exceedance management. Site-specific infiltration testing was undertaken to investigate the feasibility of disposing of clean surface water by infiltration. The relatively slow infiltration characteristics encountered, together with the scale of runoff generated by the proposed development, indicated that sole reliance upon a conventional soakaway would not provide the most appropriate drainage solution. The proposed strategy therefore provides for the collection and appropriate treatment of surface-water runoff followed by attenuation and controlled discharge to the existing drainage outfall located along the southern boundary of the site. The proposed surface-water drainage system incorporates the following principal elements: • collection of clean roof water from the proposed poultry house, manure store and associated roofed structures through dedicated roof drainage; • collection of uncontaminated surface-water runoff from relevant hardstanding and operational areas; • segregation of the clean surface-water system from soiled water, wash water and other potentially contaminated agricultural water; • appropriate sediment and silt treatment for runoff where required; • hydrocarbon interception for runoff from trafficked areas where a hydrocarbon pollution risk exists; • conveyance of clean and appropriately treated runoff to the proposed attenuation system; • temporary attenuation of runoff prior to controlled discharge; • controlled discharge through a Hydro-Brake, or equivalent approved vortex flow-control device, to the existing southern boundary drainage outfall; • separate collection and storage of soiled water and wash water generated through the operation and cleaning of the poultry development; and • management of exceedance runoff during rainfall events exceeding the design capacity of the formal drainage system. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The final surface-water drainage calculations have been undertaken for rainfall events up to and including the 1 in 100-year return-period event incorporating a 20% climate-change allowance. The attenuation system has been assessed without reliance upon infiltration to ground, with the calculations adopting zero base and side infiltration. The attenuation system will temporarily retain runoff generated during rainfall events and subsequently release stored water at the controlled design rate. This reduces the peak rate of discharge from the developed site and prevents unrestricted runoff from the new impermeable surfaces entering the existing southern boundary drain. The existing southern boundary drain forms part of the downstream drainage pathway towards the Dromore_36 River (IE_NW_36D020090). The proposed drainage strategy therefore provides a combination of source control, pollution prevention, treatment, attenuation, controlled discharge and exceedance management appropriate to the nature and scale of the proposed agricultural development. Breakdown of Site Areas The proposed surface-water drainage network has been designed to accommodate runoff generated by the positively drained surfaces associated with the proposed development. The final drainage calculations assign contributing areas to the individual storm-water nodes within the proposed network. The positively drained areas represented within the calculation are as follows: Drainage Node Contributing Area S1 0.200 ha S2 0.032 ha S3 0.080 ha S4 0.164 ha S5 0.110 ha S6 0.080 ha Total positively drained area 0.666 ha Equivalent area 6,660 m² The total contributing area represented within the final surface -water drainage calculations is therefore approximately 0.666 ha (6,660 m²). These areas represent the surfaces positively connected to the proposed storm-water network and should be distinguished from the 1.639 ha positively drained greenfield area used for the pre - development IH124 discharge assessment. The latter is used to establish the allowable greenfield discharge rate and does not represent the post-development impermeable drainage catchment. The IH124 assessment gives a greenfield QBar of 12.0 L/s. Surface water from the contributing drainage areas will be collected through the proposed network, receive appropriate treatment where required, and be conveyed to the proposed attenuation system before controlled discharge to the existing southern boundary outfall. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The detailed drainage and attenuation calculations, including the adopted rainfall parameters, attenuation storage provision, critical design events and performance of the proposed system, are presented in the subsequent sections of this report. SuDS Management Train The proposed surface-water management strategy has been developed in accordance with the principles of Sustainable Drainage Systems (SuDS) and the CIRIA SuDS Manual (C753). The strategy seeks to manage both the quantity and quality of surface-water runoff while protecting existing drainage features, downstream surface waters, groundwater and environmental receptors. The SuDS management train for the proposed development is based primarily on the segregation of clean and potentially contaminated water at source, followed by appropriate collection, treatment, attenuation and controlled discharge. Clean roof water from the proposed poultry house, manure store and associated roofed structures will be collected through dedicated roof drainage systems and conveyed to the clean surface -water network. Runoff from concrete apron, hardstanding and other positively drained areas will similarly be collected through the proposed surface-water drainage system. Soiled water, wash water and other potentially contaminated agricultural water associated with the operation and cleaning of the poultry development will be collected through a separate drainage system and conveyed to the dedicated soiled-water storage facilities. Such water will not be permitted to enter the clean surface-water drainage network, attenuation system or existing field drains. Runoff from trafficked hardstanding areas may contain sediment, suspended solids or trace hydrocarbons associated with vehicle and machinery movements. Appropriate pre-treatment will therefore be provided where required prior to runoff entering the attenuation system. Clean roof water represents a low pollution-risk source and does not inherently require hydrocarbon treatment. The proposed SuDS management train comprises: • Prevention – segregation of clean and soiled-water drainage systems and containment of potentially contaminated agricultural water at source; • Source Control – collection and management of clean roof water and surface-water runoff close to the point at which it is generated; • Treatment – provision of appropriate silt/sediment removal and hydrocarbon treatment for runoff from areas where a pollution risk exists; • Site Control – temporary storage of runoff within the proposed attenuation system to control the rate at which surface water leaves the developed site; • Controlled Discharge – release of attenuated runoff through a Hydro-Brake, or equivalent approved vortex flow-control device, to the existing southern boundary drainage outfall; and • Exceedance Management – provision for the safe management of surface water during rainfall events exceeding the design capacity of the formal drainage system. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The attenuation system forms the principal site-control measure and has been designed in conjunction with the final surface-water drainage network to temporarily store runoff generated during rainfall events before controlled release to the existing drainage network. The final flow-control arrangement restricts discharge from the attenuation system to the calculated pre- development greenfield QBar of 12.0 L/s. The Hydro-Brake incorporated into the final calculations is accordingly designed for a flow of 12.0 L/s. The proposed management train therefore provides multiple stages of runoff management and pollution prevention before surface water enters the existing southern boundary drain and downstream receiving- water network. SuDS Features Selection Hierarchy The selection of SuDS measures for the proposed development has been undertaken having regard to the principles of the CIRIA SuDS Manual (C753), the agricultural nature of the development, site topography, ground conditions, operational requirements, available space and the existing drainage network. Infiltration was initially investigated as a potential means of managing clean surface-water runoff. Site- specific infiltration testing was undertaken; however, the relatively slow infiltration characteristics encountered, together with the scale of runoff generated by the proposed development, mean that sole reliance upon a conventional soakaway is not considered appropriate. The preferred drainage strategy therefore adopts a combination of prevention, source control, treatment, attenuation, controlled discharge and exceedance management, while incorporating nature-based principles where reasonably practicable. The strategy also seeks to avoid unnecessary collection or treatment of runoff. Surrounding permeable areas will remain naturally drained where practicable, while positively drained surfaces will be connected to the proposed drainage network. Appropriate treatment will be provided according to the pollution risk associated with the contributing surface. The existing drain along the southern site boundary provides the receiving outfall for the proposed surface-water drainage system. Runoff from the developed catchment will not be discharged unrestricted to this drain but will first be appropriately managed through the proposed drainage and attenuation system. Table 2 summarises the SuDS measures considered and identifies those incorporated into the final drainage strategy. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Table 2: Hierarchy of Selected SuDS Features SuDS Measure Used Selection / Elimination Rationale Source Control Clean Roof Water Collection Yes Clean roof water from the proposed poultry house, manure store and associated roofed structures will be collected through dedicated roof drainage and conveyed to the clean surface-water system. Clean / Soiled Water Separation Yes Clean surface water will be maintained separately from soiled water, wash water and other potentially contaminated agricultural water. This represents the principal pollution-prevention measure at source. Soakaway / Infiltration No Infiltration was investigated through site-specific testing. The relatively slow infiltration characteristics encountered mean that reliance upon a conventional soakaway as the principal means of surface-water disposal is not considered appropriate. Swales No The layout and operational requirements of the poultry development limit the practical use of swales as the principal means of managing runoff from the positively drained development areas. Filter Strips No Runoff from the developed surfaces is collected through the dedicated drainage network. Filter strips would therefore provide limited hydraulic benefit within the proposed drainage arrangement. Site Control Attenuation System Yes Provides temporary storage of surface-water runoff during rainfall events and controls the rate at which runoff is released to the existing receiving drainage network. Controlled Discharge Yes Surface water stored within the attenuation system will be released through a Hydro-Brake, or equivalent approved flow-control device, before discharge to the existing southern boundary drainage outfall. Existing Southern Boundary Drain / Outfall Yes The existing drain will receive the controlled discharge from the proposed surface-water system and forms part of the downstream drainage pathway towards the Dromore_36 River. Treatment Measures Silt / Sediment Management Yes Appropriate measures will intercept sediment, debris and suspended solids from runoff where required before discharge to the attenuation system. Class 1 Petrol/Oil Interceptor Yes Hydrocarbon treatment will be provided for runoff from trafficked areas where a pollution risk exists. Clean roof water does not inherently require hydrocarbon treatment. Oil / Fuel Spill Management Yes Appropriate operational controls will minimise the potential for accidental fuel or oil contamination. Any spills will be contained and prevented from entering the clean surface-water drainage network. Nature-Based / Conveyance Measures Constructed Wetland No Not considered necessary or proportionate given the nature and scale of the development and the proposed combination of source control, treatment, attenuation and controlled discharge. Pond No Not considered necessary given the proposed attenuation and controlled- discharge arrangement and the operational requirements of the agricultural development. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Retention of Permeable / Vegetated Areas Yes Existing permeable and vegetated areas will be retained where practicable, allowing rainfall to continue to drain naturally at source rather than being unnecessarily collected within the piped network. Exceedance Management Overland Exceedance Routing Yes During events exceeding the capacity of the formal drainage system, exceedance runoff will, insofar as practicable, be directed away from buildings, sensitive areas and adjoining properties along appropriate overland flow routes. Nature-Based Solutions In response to the Further Information request, consideration has been given to the incorporation of nature-based surface-water management measures within the proposed development. The site comprises an agricultural development where areas are required for vehicle movements, access to the poultry house and manure store, and associated farm operations. These operational requirements influence the type and extent of open SuDS features that can practicably be incorporated within the active development area. The proposed strategy has therefore been developed to apply nature-based drainage principles in a manner proportionate to the nature, scale and operational requirements of the development. A key component of this approach is to avoid unnecessarily collecting runoff from areas that can remain naturally drained. Existing permeable and vegetated areas surrounding the proposed development will therefore be retained where practicable. Rainfall falling on these areas will continue to drain naturally at source rather than being unnecessarily intercepted and conveyed through the piped surface -water system. The extent of positively drained surfaces has been limited to those areas requiring formal drainage as part of the operation of the development. Runoff generated from these surfaces will be collected and appropriately treated before entering the proposed attenuation system. The attenuation system will temporarily retain runoff generated during rainfall events and regulate its subsequent release to the existing drainage network. The final drainage calculations do not rely upon infiltration through the attenuation system, with zero base and side infiltration incorporated into the calculations. This arrangement provides resilience where the site-specific ground conditions are not suitable for reliance upon conventional infiltration drainage, while allowing surrounding undeveloped areas to continue functioning as naturally drained permeable surfaces. The proposed approach therefore combines prevention, source control, retention of existing permeable areas, appropriate runoff treatment, attenuation, controlled discharge and exceedance management. The selected measures are considered appropriate to the agricultural nature of the development and REC E I V E D : 1 7 / 0 9 / 2 0 2 6 seek to maintain natural drainage processes wherever reasonably practicable while providing effective control of runoff from the positively drained development areas. Assessment Under the Four Pillars of SuDS Sustainable Drainage Systems are commonly considered against four principal objectives: water quantity, water quality, biodiversity and amenity. The proposed surface-water management strategy has been developed to achieve an appropriate balance across these objectives while recognising the operational requirements and rural agricultural nature of the proposed poultry development. The principal benefits of the proposed strategy relate to the management of runoff quantity and water quality. These are achieved through the segregation of clean and soiled water at source, appropriate treatment of runoff where required, temporary attenuation and controlled discharge to the existing drainage network. The agricultural and operational nature of the development limits the opportunity for SuDS features providing significant direct amenity or biodiversity benefits. Nevertheless, the retention of existing permeable and vegetated areas where practicable, together with protection of downstream water quality and controlled management of runoff, provides indirect environmental benefits. The performance of the principal SuDS measures incorporated within the proposed development is summarised in Table 3. Table 3: Assessment of Proposed SuDS Measures Under the Four Pillars of SuDS 4 Pillars of SuDS SuDS Feature Quantity Quality Biodiversity Amenity Clean Roof Water Collection Good Good Poor Poor Clean / Soiled Water Separation Good Good Moderate Poor Silt / Sediment Management Moderate Good Poor Poor Class 1 Petrol/Oil Interceptor Moderate Good Poor Poor Attenuation System Good Moderate Poor Poor Controlled Discharge Good Moderate Poor Poor Retention of Permeable / Vegetated Areas Moderate Moderate Good Moderate Overland Exceedance Routing Good Moderate Moderate Moderate Dedicated Soiled-Water Storage Moderate Good Moderate Poor The assessment demonstrates that the proposed drainage strategy provides particular benefits in relation to runoff quantity and runoff quality. The attenuation system provides temporary storage of surface-water REC E I V E D : 1 7 / 0 9 / 2 0 2 6 runoff and, in combination with the proposed flow-control arrangement, limits the rate at which runoff from the developed site is released to the existing southern boundary drain. Runoff quality is protected primarily through the segregation of clean and soiled water at source. Additional treatment is provided through appropriate silt and sediment management and hydrocarbon interception for runoff from trafficked areas where required. Soiled water, wash water and other potentially contaminated agricultural water will be separately collected and stored and will not be permitted to enter the clean surface-water drainage system. The proposed attenuation and treatment infrastructure provides limited direct biodiversity and amenity benefit. However, existing permeable and vegetated areas will be retained where practicable and allowed to continue draining naturally. In combination with the controlled management of runoff and protection of downstream water quality, this provides indirect benefits to the downstream aquatic and terrestrial environment. The overall drainage strategy is therefore considered to provide an appropriate balance between the operational requirements of the proposed agricultural development and the four principal objectives of Sustainable Drainage Systems. Attenuation System A dedicated surface-water attenuation system is proposed as the principal site-control SuDS measure for the management of runoff arising from the positively drained areas of the proposed development. The attenuation system will receive runoff collected through the proposed surface-water drainage network, including clean roof water from the proposed agricultural buildings and runoff from positively drained hardstanding and operational areas. Runoff presenting a potential sediment or hydrocarbon pollution risk will receive appropriate treatment prior to entering the attenuation system. Infiltration was initially investigated as a potential means of managing clean surface -water runoff. However, site-specific infiltration testing identified relatively slow infiltration characteristics, with the water level taking approximately 15 hours to fall between the 75% and 25% effective test levels. Reliance upon a conventional soakaway as the principal means of surface-water disposal was therefore not considered appropriate for the proposed development. The adopted strategy instead provides for the temporary storage and attenuation of runoff prior to controlled discharge to the existing drainage outfall located along the southern boundary of the site. The final drainage calculations do not rely upon infiltration through the attenuation system, with both the base and side infiltration coefficients set at 0.00000 m/hr. The final surface-water drainage calculations represent a total positively drained contributing area of approximately 0.666 ha (6,660 m²) within the proposed storm-water network. This is distinct from the 1.639 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 ha greenfield area used in the IH124 assessment to establish the allowable pre -development discharge rate. The attenuation structure incorporated within the drainage calculations has an invert level of 95.300 m, a plan dimension of approximately 27.070 m × 6.780 m, a depth of 1.440 m and an adopted porosity of 0.71. These parameters represent the attenuation structure incorporated into the drainage calculations and will be subject to the detailed specification of the selected proprietary system. The drainage and attenuation calculations consider a range of storm durations and return periods up to and including the 1 in 100-year event with a 20% climate-change allowance. Following attenuation, stored runoff will be released through a flow-control chamber incorporating a Hydro-Brake, or equivalent approved vortex flow-control device. The allowable discharge has been established from the pre-development greenfield runoff assessment, which gives a QBar of 12.0 L/s. The proposed Hydro-Brake has accordingly been designed for a controlled flow of 12.0 L/s. Following flow control, surface water will be conveyed to the existing drainage outfall and southern boundary drain, which forms part of the downstream drainage pathway towards the Dromore_36 River. The attenuation system therefore provides temporary storage and controlled release of runoff from the developed site without reliance upon infiltration to ground. Detailed drainage calculations and assessment of the performance of the attenuation system under the applicable design storm events are presented later in this report. Runoff Quality Assessment The proposed surface-water management strategy has been developed to ensure that runoff from the development is appropriately managed and that soiled or potentially contaminated agricultural water is prevented from entering the clean surface-water drainage system, existing field drains and downstream receiving waters. The principal source of low-risk runoff generated by the development comprises rainfall falling on the roofs of the proposed poultry house, manure store and associated roofed structures. Clean roof water will be collected through dedicated gutters and downpipes and conveyed through the clean surface- water drainage network towards the proposed attenuation system. Surface-water runoff from concrete apron, trafficked hardstanding and operational areas may contain sediment, suspended solids or trace hydrocarbons associated with vehicle and machinery movements. Appropriate treatment will therefore be provided according to the pollution risk associated with the contributing surface. Silt and sediment management measures will provide primary treatment by intercepting sediment, debris and suspended solids from relevant runoff. Runoff from trafficked areas where a potential hydrocarbon REC E I V E D : 1 7 / 0 9 / 2 0 2 6 pollution risk exists will additionally pass through a Class 1 petrol/oil interceptor, or equivalent approved treatment system, prior to discharge to the attenuation system. Clean roof water will not be unnecessarily routed through hydrocarbon treatment, as it does not present the same pollution risk as runoff from trafficked surfaces. The drainage arrangement will therefore ensure that treatment is targeted towards runoff sources presenting an identified pollution risk. Soiled water, wash water and other potentially contaminated agricultural water associated with the operation and cleaning of the poultry development will be collected separately and conveyed to the dedicated soiled-water storage system. No soiled water or wash water will be permitted to enter the clean surface-water drainage network, attenuation system, existing field drains or downstream receiving waters. Operational controls will also be implemented to minimise the potential for accidental oil or fuel contamination associated with vehicles and machinery. In the event of a spill, appropriate containment and clean-up procedures will be employed to prevent contaminants entering the surface-water drainage system. The proposed treatment train therefore comprises pollution prevention and segregation at source, appropriate sediment removal, hydrocarbon treatment where required, attenuation and controlled discharge. These measures will minimise the potential for sedime nt, hydrocarbons and other contaminants to be conveyed to the existing southern boundary drain and downstream receiving-water environment. Soiled Water Collection and Storage Soiled water and wash water generated in association with the proposed poultry development will be collected through a dedicated soiled-water drainage system, maintained entirely separate from the clean surface-water drainage network. Two underground reinforced concrete washings tanks are proposed for the collection and containment of soiled/wash water generated by the development: Location Capacity Dimensions Rear of proposed poultry house 3,500 gallons 2.85 m internal diameter × 2.70 m deep Front of proposed poultry house 5,000 gallons 5.01 m × 2.73 m internally × 2.57 m deep The 3,500-gallon tank will be located to the rear of the proposed poultry house and will comprise a precast reinforced concrete underground washings tank, approximately 2.85 m internal diameter and 2.70 m deep. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The 5,000-gallon tank will be located to the front of the proposed poultry house and will comprise a precast reinforced concrete underground elliptical washings tank, approximately 5.01 m × 2.73 m internally and 2.57 m deep. The locations, capacities and dimensions of both tanks are clearly identified on the accompanying site layout. The associated soiled-water drainage system is shown separately from the clean surface-water drainage network. All soiled water and wash water generated by the development will be directed to the dedicated storage tanks. No soiled water, wash water or other potentially contaminated agricultural runoff will be permitted to enter the clean surface-water drainage network, attenuation system, field drains or downstream receiving waters. The tanks will be maintained as sealed storage units and emptied as required, with the collected contents managed in accordance with the agricultural nutrient-management arrangements for the development. Treatment Train Assessment The proposed surface-water drainage system incorporates multiple stages of runoff management and treatment in accordance with the principles of the CIRIA SuDS Manual (C753). The treatment train is intended to prevent pollution at source, provide treatment appropriate to the pollution risk associated with the contributing surfaces, temporarily attenuate runoff and control the rate of surface -water discharge from the development. The proposed treatment train is summarised in Table 4. Table 4: Treatment Train SuDS Stage Measure Function Prevention Clean / soiled-water separation Prevents soiled water, wash water and other potentially contaminated agricultural water from entering the clean surface-water drainage system. Source Control Roof and hardstanding drainage collection Collects and manages surface-water runoff close to the point at which it is generated. Treatment Stage 1 Silt trap / sediment control Removes sediment, debris and suspended solids from relevant runoff prior to attenuation. Treatment Stage 2 Class 1 Petrol/Oil Interceptor Provides hydrocarbon treatment for runoff from trafficked areas where a pollution risk exists. Site Control Attenuation system Provides temporary storage of runoff and controls peak surface-water discharge from the developed site. Flow Control Hydro-Brake / vortex flow control Restricts discharge from the attenuation system to the allowable controlled rate before discharge to the existing southern boundary drainage outfall. Exceedance Overland exceedance routing Provides for the management of runoff during rainfall events exceeding the design capacity of the formal drainage system. Clean roof water represents a low pollution-risk runoff source and will be collected through dedicated roof drainage systems. Runoff from concrete apron and other trafficked hardstanding areas presents a REC E I V E D : 1 7 / 0 9 / 2 0 2 6 greater potential for sediment, suspended solids or trace hydrocarbons associated with vehicle and machinery movements and will therefore receive appropriate treatment. Soiled water, wash water and other potentially contaminated agricultural water associated with the operation and cleaning of the poultry development will be collected separately and directed to the dedicated soiled-water storage system. Such water will not be permitted to enter the clean surface- water drainage network, attenuation system or receiving drainage network. Following appropriate treatment, surface water will enter the proposed attenuation system, where runoff will be temporarily stored before being released through the proposed flow-control arrangement to the existing drainage outfall along the southern site boundary. The final flow-control arrangement incorporates a Hydro-Brake designed to restrict discharge to 12.0 L/s, corresponding with the calculated pre-development greenfield QBar. The proposed treatment train therefore combines pollution prevention, source control, sediment management, hydrocarbon treatment where required, attenuation and controlled discharge, providing a multi-stage approach to the management of both runoff quantity and runoff quality. Impact on Habitat and Water Quality The proposed surface-water management strategy has been developed to minimise the potential for the proposed development to adversely affect local habitats, groundwater, existing drainage features and downstream surface-water receptors. The principal pollution-prevention measure incorporated into the drainage strategy is the segregation of clean surface water from soiled water, wash water and other potentially contaminated agricultural water. Soiled and potentially contaminated water will be collected through a separate drainage system and directed to dedicated storage facilities and will not be permitted to enter the clean surface -water drainage network. Clean roof water from the proposed poultry house, manure store and associated roofed structures will be collected through dedicated roof drainage. Surface-water runoff from concrete apron and other trafficked areas will be subject to appropriate treatment having regard to the potential pollution risk associated with those surfaces. Silt and sediment management measures will reduce the quantity of sediment, debris and suspended solids conveyed through the drainage network. Where runoff originates from trafficked areas presenting a potential hydrocarbon pollution risk, additional treatment will be provided by a Class 1 petrol/oil interceptor, or equivalent approved unit. Following collection and appropriate treatment, surface water will be conveyed to the proposed attenuation system. The attenuation system will temporarily store runoff before controlled discharge to REC E I V E D : 1 7 / 0 9 / 2 0 2 6 the existing southern boundary drainage outfall, thereby reducing the rate at which runoff from the developed site enters the receiving drainage network. The principal downstream surface-water receptor identified in the vicinity of the development is the Dromore_36 River (Waterbody Code: IE_NW_36D020090), located approximately 618 m south of the site. Existing drains along the western and southern site boundaries form part of the local drainage network towards the downstream receiving environment, with the southern boundary drain receiving the controlled discharge from the proposed surface-water system. The proposed drainage strategy therefore incorporates a combination of pollution prevention, clean/soiled-water segregation, sediment control, hydrocarbon treatment where required, attenuation and controlled discharge. These measures are intended to minimise the potential for pollutants or elevated runoff rates to adversely affect the existing drainage network, groundwater or downstream surface-water environment. The potential impacts and associated mitigation measures are summarised in Table 5. Table 5: Impact on Habitat and Water Quality Receptor Potential Impact Proposed Mitigation Residual Impact Groundwater Accidental release of hydrocarbons or contaminated water Clean/soiled-water segregation, dedicated soiled-water storage, appropriate drainage controls and hydrocarbon treatment for runoff from relevant trafficked areas Low Existing Southern Boundary Drain Sediment, hydrocarbon contamination and increased runoff rates Silt/sediment management, hydrocarbon interception where required, attenuation and controlled discharge Low Dromore_36 River (IE_NW_36D020090) Indirect deterioration in downstream water quality or increased runoff through the connecting drainage network Pollution prevention at source, appropriate runoff treatment, attenuation and controlled discharge prior to entering the existing drainage network Low Local Habitats Sediment, contaminated runoff or mobilisation of pollutants Segregation and containment of potentially contaminated water, sediment control and appropriate surface-water treatment Low Downstream Water Environment Increased peak runoff and deterioration in runoff quality Treatment measures, attenuation and restriction of discharge to the calculated pre-development greenfield runoff rate Low REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Having regard to the proposed drainage controls, the development incorporates appropriate measures to minimise the potential for adverse effects on groundwater, surface -water quality and downstream habitats. Petrol / Oil Interceptor The proposed surface-water drainage system will collect clean roof water from the proposed poultry house, manure store and associated roofed structures, together with surface-water runoff from concrete apron, hardstanding and other positively drained areas. Runoff from trafficked areas has the potential to contain hydrocarbons or oils associated with vehicle and machinery movements. A Class 1 petrol/oil interceptor, or equivalent approved unit, will therefore be incorporated into the drainage system to provide additional protection against the conveyance of hydrocarbons to the attenuation system and downstream receiving drainage network. Appropriate silt and sediment control will also be incorporated within the drainage system to reduce the quantity of sediment, debris and suspended solids entering the interceptor and attenuation system. The interceptor will be appropriately sized having regard to the contributing catchment routed through the unit, the proposed drainage arrangement and the manufacturer's design requirements. The selected unit will be suitable for the anticipated hydraulic loading and installed in accordance with the manufacturer's recommendations. Following treatment, runoff will be conveyed to the proposed attenuation system, where it will be temporarily stored before controlled discharge to the existing drainage outfall along the southern site boundary. The interceptor will be located to permit safe access for inspection and maintenance. Regular inspection and removal of accumulated oil, silt and debris will be undertaken in accordance with the manufacturer's operation and maintenance requirements to ensure continued effective performance. A typical detail of a Class 1 Petrol/Oil Interceptor is presented in Figure 4. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Figure 4: Cross Section of a Class 1 By-Pass Petrol/Oil Interceptor Figure 5: Enlarged View of Proposed Surface Water Drainage Layout Surface-water runoff from the proposed roof areas, concrete apron, hardstanding and associated positively drained areas will be collected through the dedicated surface-water drainage network and conveyed towards the proposed attenuation system. The proposed drainage arrangement incorporates appropriate pollution-prevention measures prior to attenuation. A NSBE015 by-pass petrol interceptor, or similar approved unit, is proposed to provide hydrocarbon treatment for runoff associated with trafficked areas. Appropriate sediment and silt control will also be incorporated within the drainage system to minimise the conveyance of sediment, debris and suspended solids to the attenuation system. Following collection and appropriate treatment, surface water will be conveyed to the proposed StormTech Polytunnel attenuation tank, or similar approved system, which will provide temporary storage of runoff during rainfall events. In accordance with the final drainage layout, the attenuation system will provide a minimum storage capacity of 188 m³. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Discharge from the attenuation system will occur by gravity through a flow-control chamber incorporating a Hydro-Brake, or equivalent approved vortex flow-control device, restricting discharge to a maximum design rate of 12.0 L/s, corresponding with the calculated pre-development greenfield QBar. Following attenuation and flow control, surface water will be conveyed to the proposed outfall to the existing open drain located along the southern site boundary, as identified on the final surface -water drainage layout. Design Parameters The proposed surface-water drainage and attenuation system has been designed to collect and manage runoff generated from the positively drained areas associated with the proposed development prior to controlled discharge to the existing southern boundary drainage outfall. The proposed system does not rely upon infiltration to ground to accommodate the design runoff. Surface water will instead be temporarily stored within the proposed attenuation system and subsequently released through a flow-control chamber incorporating a Hydro-Brake, or equivalent approved vortex flow-control device. The principal design parameters adopted within the final surface-water drainage calculations are summarised below. Design Parameter Adopted Value Post-development positively drained area represented in drainage calculations 0.666 ha Greenfield area used for IH124 assessment 1.639 ha Greenfield runoff methodology IH124 Calculated greenfield QBar 12.0 L/s Maximum controlled discharge 12.0 L/s Design return period 1 in 100 years Climate-change allowance 20% Attenuation base infiltration 0.00000 m/hr Attenuation side infiltration 0.00000 m/hr Minimum attenuation capacity shown on final drainage layout 188 m³ The pre-development greenfield assessment establishes a QBar of 12.0 L/s, which has been adopted as the maximum controlled discharge from the proposed attenuation system. The detailed surface-water drainage and attenuation calculations are provided in Appendix F of this report. Attenuation System A dedicated attenuation system is proposed to provide temporary storage of surface-water runoff generated by the proposed development prior to controlled discharge to the existing drainage network. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 The final drainage layout identifies a StormTech Polytunnel attenuation tank, or similar approved system, with a minimum storage capacity of 188 m³. The attenuation structure incorporated within the drainage calculations has an invert level of 95.300 m, an approximate calculated plan dimension of 27.070 m × 6.780 m, a depth of 1.440 m and an adopted porosity of 0.71. The drainage calculations adopt zero infiltration through both the base and sides of the attenuation system. The final proprietary attenuation system shall be installed in accordance with the manufacturer's requirements and coordinated with the drainage levels and connections shown on the final engineering layout. Flow Control and Discharge Surface water will be temporarily stored within the attenuation system before discharge through a flow-control chamber incorporating a Hydro-Brake, or equivalent approved vortex flow-control device. The allowable discharge has been established using the IH124 greenfield runoff assessment. This gives a pre - development greenfield QBar of 12.0 L/s, which has been adopted as the maximum design discharge from the proposed attenuation system. The final drainage calculations specify a Hydro-Brake design flow of 12.0 L/s, with an invert level of 95.284 m and design depth of 1.456 m. Following flow control, attenuated surface water will discharge by gravity to the proposed outfall to the existing open drain along the southern site boundary, as shown on the final drainage layout. Infiltration Testing and Groundwater Conditions Site-specific infiltration testing was undertaken to investigate the suitability of infiltration as the principal means of surface-water disposal. The observed time for the water level to fall between the 75% and 25% effective test levels was approximately 15 hours, indicating relatively slow infiltration characteristics. Having regard to the infiltration test results and the scale of runoff generated by the proposed development, reliance upon infiltration as the principal means of surface-water disposal was not considered appropriate. The proposed drainage strategy therefore provides attenuation and controlled discharge to the existing southern boundary drainage outfall. No allowance for infiltration has been incorporated into the final attenuation calculations. The attenuation structure has been assessed using base and side infiltration coefficients of 0.00000 m/hr, such that the calculated drainage performance does not depend upon infiltration to ground. No groundwater was encountered within the trial pit to the investigated depth of approximately 1.5 m below ground level at the time of the site investigation. Groundwater conditions below the investigated depth have not been directly confirmed. The final formation level and installation arrangement of the attenuation system shall therefore be confirmed during construction having regard to the actual ground conditions encountered, final drainage invert levels and the REC E I V E D : 1 7 / 0 9 / 2 0 2 6 proprietary system manufacturer's installation requirements. Should groundwater be encountered during excavation, the installation arrangement shall be reviewed by the project engineer and attenuation-system supplier as appropriate. Drainage Calculation Results Detailed surface-water drainage calculations have been undertaken for the proposed drainage network and attenuation system using the final development layout and drainage arrangement. The assessment considers a range of storm durations and return periods up to and including the 1 in 100 -year event incorporating a 20% climate-change allowance. The calculations incorporate the proposed attenuation system and the controlled 12.0 L/s discharge through the Hydro-Brake. The assessment demonstrates the performance of the proposed drainage system under the applicable design rainfall events. The complete surface-water drainage calculations, including network details, rainfall parameters, flow-control specification, attenuation parameters and simulation results, are provided in Appendix F. Conclusion of Attenuation Assessment The proposed surface-water management system provides for the collection, appropriate treatment, attenuation and controlled discharge of runoff generated by the proposed development. The final drainage arrangement incorporates a StormTech Polytunnel attenuation tank, or similar approved system, with a minimum capacity of 188 m³, together with a Hydro-Brake restricting discharge to the calculated pre- development greenfield QBar of 12.0 L/s. The attenuation assessment does not rely upon infiltration to ground and incorporates a 20% climate -change allowance for the applicable design rainfall events. Following attenuation and flow control, surface water will discharge by gravity to the proposed outfall to the existing open drain along the southern site boundary. On this basis, the proposed drainage arrangement provides a controlled surface-water management solution appropriate to the proposed development, with the supporting engineering calculations provided in Appendix F. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Figure 7: Site Layout Aghnaclea, Ballybay, Co. Monaghan showing Location of Tested Area REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Figure 8: Cross-Section of Proposed Stormwater Attenuation System at Aghnaclea, Ballybay, Co. Monaghan. NB: • A silt trap and Class 1 by-pass petrol/oil interceptor, or similar approved treatment units, shall be incorporated into the surface-water drainage system upstream of the attenuation system where required by the final drainage arrangement. • The proposed attenuation system shall provide a minimum storage capacity of 188 m³, as indicated on the final drainage layout. • The attenuation system shall be designed, supplied and installed in accordance with the proprietary system manufacturer's requirements, the final engineering design and all relevant applicable standards. • Discharge from the attenuation system shall pass through a flow-control chamber incorporating a Hydro-Brake, or equivalent approved vortex flow-control device, restricting the maximum discharge rate to 12.0 L/s. • Following attenuation and flow control, surface water shall be discharged to the proposed outfall to the existing open drain along the southern site boundary, as shown on the final drainage layout. • All elements of the surface-water drainage system, including the silt trap, petrol/oil interceptor, attenuation system, inspection chambers, flow-control chamber and associated pipework, shall remain accessible for inspection and maintenance. • The silt trap and petrol/oil interceptor shall be inspected, cleaned and emptied as required to prevent accumulated sediment, debris, hydrocarbons or other contaminants from reducing the effectiveness of the drainage treatment system. • The attenuation system shall be installed with the proprietary geotextile, geomembrane, stone surround or other ancillary materials required by the selected attenuation-system manufacturer and final detailed design. • Clean, washed angular stone of the grading and specification required by the proprietary attenuation- system manufacturer shall be provided where applicable as part of the attenuation installation. • Appropriate separation shall be maintained between the attenuation system and building foundations, site boundaries, services and other infrastructure in accordance with the final engineering design and proprietary manufacturer's requirements. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 • Site investigation identified no groundwater within the trial pit to the investigated depth of approximately 1.5 m below ground level at the time of investigation. As the final attenuation excavation may extend below this depth, the formation level and installation arrangement shall be confirmed during excavation having regard to the actual ground and groundwater conditions encountered. • Should groundwater, unsuitable material or other unforeseen ground conditions be encountered during excavation, the installation arrangement shall be reviewed by the project engineer and proprietary attenuation-system supplier and any necessary measures incorporated into the final construction detail. • The proposed attenuation strategy does not rely upon infiltration to ground to achieve the required drainage performance. The final drainage calculations adopt zero infiltration through the base and sides of the attenuation system. • Only clean roof water and appropriately treated surface-water runoff shall enter the attenuation system. Soiled water, wash water and other potentially contaminated agricultural water shall not be permitted to enter the clean surface-water drainage network, attenuation system or receiving drain. • The final attenuation-system configuration, chamber arrangement, excavation dimensions, formation level, cover depth, stone surround, structural requirements and inlet/outlet details shall be coordinated with the final engineering drawings and proprietary supplier's detailed design. Should you have any queries on this, do not hesitate to contact me. Yours sincerely Nevin Traynor BSc. Env, H.Dip I.T, Cert SHWW, EPA/FAS Cert. For Traynor Environmental Ltd Encl – Appendices A-F REC E I V E D : 1 7 / 0 9 / 2 0 2 6 SOAKAWAY TESTING TO BRE DIGEST 365 SITE AT AGHNACLEA, BALLYBAY, CO. MONAGHAN COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX A – TRIAL PIT LOG REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Trial Pit Number TP A Traynor Environmental Ltd Unit 6, Belturbet Business Park Creeny Belturbet Co. Cavan Sheet 1 of 1 Client Derek Niblock Job Number: 26/446 TE Logged By NT Method 13 ton digger Ground Level Start Date 13.08.26 Description Legend Reduced Level Depth Water Strike (m) Installation Backfill Sample Test Notes Silt/Clay intermixed with stone Crumb Nature Low Density Brown Colour - 0.00m- 0.40m - - - - - Clay Intermixed with stones Crumby Nature Low Density Brown Colour Clay Intermixed with stones Crumby Nature Medium Density Brown Colour - 0.40m- 1.50m - - - - - Trial Pit Completed at 1.50m BGL. Remarks: Groundwater: None Encountered to 1.50 m BGL at the time of excavation Bedrock: None Encountered to investigated depth Infiltration testing subsequently identified relatively slow infiltration characteristics. Pit Dimensions Length: 2.30m Width: 1.50m Photo REC E I V E D : 1 7 / 0 9 / 2 0 2 6 SOAKAWAY TESTING TO BRE DIGEST 365 SITE AT AGHNACLEA, BALLYBAY, CO. MONAGHAN COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX B – SITE PHOTOGRAPHS REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Photographs From the Soakaway Test No. 1 Side View Of Soakaway Test Hole No 1 Prior To Test Front View Of Soakaway Test Hole No 1 Prior To Test Filling of Soakaway Hole Removed from Soakaway REC E I V E D : 1 7 / 0 9 / 2 0 2 6 SOAKAWAY TESTING TO BRE DIGEST 365 SITE AT AGHNACLEA, BALLYBAY, CO. MONAGHAN COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX C – MET EIREANN RAINFALL RETURN PERIODS REC E I V E D : 1 7 / 0 9 / 2 0 2 6 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 SOAKAWAY TESTING TO BRE DIGEST 365 SITE AT AGHNACLEA, BALLYBAY, CO. MONAGHAN COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX D – MAPS USED AS PART OF THE DESK STUDY REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Maps Used As Part of the EPA Site Suitability Assessment Groundwater/Aquifer Map From the GSI Groundwater Aquifer Map Site is classified as PI – Poor Aquifer - Bedrock which is Generally Unproductive except for Local Zones Vulnerability Map The site is classified as ‘Moderate’ groundwater vulnerability. REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Bedrock Map From the GSI Bedrock Map Site is classified as Silurian Metasediments and Volcanics Teagasc Subsoil Map From the Teagasc Subsoil Map Site is classified as Sandstone and shale till (Lower Palaeozoic) REC E I V E D : 1 7 / 0 9 / 2 0 2 6 SOAKAWAY TESTING TO BRE DIGEST 365 SITE AT AGHNACLEA, BALLYBAY, CO. MONAGHAN COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX E – PI INSURANCE DETAILS REC E I V E D : 1 7 / 0 9 / 2 0 2 6 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 SOAKAWAY TESTING TO BRE DIGEST 365 SITE AT AGHNACLEA, BALLYBAY, CO. MONAGHAN COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX F – SURFACE WATER DRAINAGE AND ATTENUATION CALCULATIONS REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Alan Traynor Consulting File: Tranor Derek flow design.pfd Network: Storm Network Jake Blewitt 01/09/2026 Page 1 Flow+ v18.0 Copyright © 1988-2026 Causeway Technologies Ltd Simulation Settings Rainfall Methodology Rainfall Events FSR Region M5-60 (mm) Ratio-R Summer CV Winter CV Analysis Speed Skip Steady State Drain Down Time (mins) FSR Singular Scotland and Ireland 14.900 0.273 0.750 0.840 Normal x 240 Additional Storage (m³/ha) Starting Level (m) Check Discharge Rate(s) 1 year (l/s) 10 year (l/s) 30 year (l/s) 100 year (l/s) Check Discharge Volume 100 year 360 minute (m³) 20.0 ✓ 10.0 16.5 19.9 23.6 ✓ Storm Durations 15 30 60 120 180 240 360 480 600 720 960 1440 Return Period (years) Climate Change (CC %) Additional Area (A %) Additional Flow (Q %) Return Period (years) Climate Change (CC %) Additional Area (A %) Additional Flow (Q %) 1 10 20 20 0 0 0 0 30 100 20 20 0 0 0 0 Pre-development Discharge Rate Site Makeup Greenfield Method Positively Drained Area (ha) SAAR (mm) Soil Index SPR Greenfield IH124 1.639 1002 4 0.47 Region Growth Factor 1 year Growth Factor 10 year Growth Factor 30 year Growth Factor 100 year Betterment (%) 11 0.83 1.37 1.65 1.96 0 QBar Q 1 year (l/s) Q 10 year (l/s) Q 30 year (l/s) Q 100 year (l/s) 12.0 10.0 16.5 19.9 23.6 Pre-development Discharge Volume Site Makeup Greenfield Method Positively Drained Area (ha) Soil Index Greenfield FSR/FEH 1.639 4 SPR CWI Return Period (years) Climate Change (%) 0.47 100 0 Storm Duration (mins) Betterment (%) PR Runoff Volume (m³) 360 0 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Alan Traynor Consulting File: Tranor Derek flow design.pfd Network: Storm Network Jake Blewitt 01/09/2026 Page 2 Flow+ v18.0 Copyright © 1988-2026 Causeway Technologies Ltd Design Settings Rainfall Methodology Return Period (years) Additional Flow (%) FSR Region M5-60 (mm) Ratio-R CV Time of Entry (mins) FSR 100 0 England and Wales 14.900 0.273 0.750 5.00 Maximum Time of Concentration (mins) Maximum Rainfall (mm/hr) Minimum Velocity (m/s) Connection Type Minimum Backdrop Height (m) Preferred Cover Depth (m) Include Intermediate Ground Enforce best practice design rules 30.00 50.0 0.71 Level Soffits 0.600 1.200 ✓ ✓ Nodes Name Area (ha) T of E (mins) Cover Level (m) Diameter (mm) Easting (m) Northing (m) Depth (m) Invert Level (m) S1 S2 S3 S4 S5 S6 S7 S8 Outfall Atten Tank 0.200 0.032 0.080 0.164 0.110 0.080 5.00 5.00 5.00 5.00 5.00 5.00 5.00 98.400 98.400 98.400 97.400 97.400 97.400 98.400 98.400 98.100 98.400 1200 1200 1200 1200 1200 1200 1350 1500 1350 81173.960 81262.349 81256.019 81157.189 81151.266 81172.170 81216.725 81215.984 81178.824 81219.211 122720.503 122706.557 122666.439 122717.472 122679.937 122676.616 122672.674 122668.441 122651.812 122667.622 1.500 1.947 2.150 1.500 1.690 1.796 3.095 3.116 3.020 3.100 96.900 96.453 96.250 95.900 95.710 95.604 95.305 95.284 95.080 95.300 Links Name US Node DS Node Length (m) ks (mm) / n US IL (m) DS IL (m) Fall (m) Slope (1:X) Dia (mm) T of C (mins) Rain (mm/hr) Name Vel (m/s) Cap (l/s) Flow (l/s) US Depth (m) DS Depth (m) Σ Area (ha) Σ Add Inflow (l/s) Pro Depth (mm) Pro Velocity (m/s) 1.000 S1 S2 89.482 0.600 96.900 96.453 0.447 200.0 300 6.35 50.0 1.000 1.108 78.3 27.1 1.200 1.647 0.200 0.0 122 1.010 1.001 S2 S3 40.614 0.600 96.453 96.250 0.203 200.0 300 6.96 50.0 1.001 1.108 78.3 31.4 1.647 1.850 0.232 0.0 132 1.049 1.002 S3 S7 39.786 0.600 96.250 95.380 0.870 45.7 300 7.24 50.0 1.002 2.331 164.7 42.3 1.850 2.720 0.312 0.0 103 1.964 2.000 S4 S5 37.999 0.600 95.900 95.710 0.190 200.0 300 5.57 50.0 2.000 1.108 78.3 22.2 1.200 1.390 0.164 0.0 109 0.959 2.001 S5 S6 21.166 0.600 95.710 95.604 0.106 200.0 300 5.89 50.0 2.001 1.108 78.3 37.1 1.390 1.496 0.274 0.0 146 1.094 2.002 S6 S7 44.729 0.600 95.604 95.380 0.224 200.0 300 6.56 50.0 2.002 1.108 78.3 48.0 1.496 2.720 0.354 0.0 170 1.161 1.003 S7 S8 4.297 0.600 95.305 95.284 0.021 200.0 375 7.30 50.0 1.003 1.277 141.1 90.3 2.720 2.741 0.666 0.0 219 1.352 1.004 S8 Outfall 40.711 0.600 95.284 95.080 0.204 200.0 375 7.83 50.0 1.004 1.277 141.1 90.3 2.741 2.645 0.666 0.0 219 1.352 3.000 Atten Tank S8 3.329 0.600 95.300 95.284 0.016 208.1 375 5.04 50.0 3.000 1.252 138.3 0.0 2.725 2.741 0.000 0.0 0 0.000 Node S8 Online Hydro-Brake® Control Flap Valve Replaces Downstream Link Invert Level (m) Design Depth (m) Design Flow (l/s) x x 95.284 1.456 12.0 Objective Sump Available Product Number Min Outlet Diameter (m) Min Node Diameter (mm) (HE) Minimise upstream storage ✓ CTL-SHE-0152-1200-1456-1200 0.225 1500 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Alan Traynor Consulting File: Tranor Derek flow design.pfd Network: Storm Network Jake Blewitt 01/09/2026 Page 3 Flow+ v18.0 Copyright © 1988-2026 Causeway Technologies Ltd Node Atten Tank Carpark Storage Structure Base Inf Coefficient (m/hr) Side Inf Coefficient (m/hr) Safety Factor Porosity 0.00000 0.00000 2.0 0.71 Invert Level (m) Time to half empty (mins) Width (m) Length (m) 95.300 148 6.780 27.070 Slope (1:X) Depth (m) Inf Depth (m) 300.0 1.440 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Alan Traynor Consulting File: Tranor Derek flow design.pfd Network: Storm Network Jake Blewitt 01/09/2026 Page 4 Flow+ v18.0 Copyright © 1988-2026 Causeway Technologies Ltd Results for 1 year +20% CC Critical Storm Duration. Lowest mass balance: 99.31% Node Event US Node Peak (mins) Level (m) Depth (m) Inflow (l/s) Node Vol (m³) Flood (m³) Status Link Event (Upstream Depth) US Node Link DS Node Outflow (l/s) Velocity (m/s) Flow/Cap Link Vol (m³) Discharge Vol (m³) 15 minute winter S1 10 97.013 0.113 24.5 0.4285 0.0000 OK 15 minute winter S1 1.000 S2 24.0 0.934 0.307 2.3257 15 minute winter S2 11 96.578 0.125 27.7 0.1828 0.0000 OK 15 minute winter S2 1.001 S3 26.5 1.157 0.339 0.9438 15 minute winter S3 11 96.343 0.093 35.7 0.1748 0.0000 OK 15 minute winter S3 1.002 S7 35.1 1.411 0.213 1.1321 15 minute winter S4 10 96.001 0.101 20.1 0.3350 0.0000 OK 15 minute winter S4 2.000 S5 19.5 0.729 0.249 1.0268 15 minute winter S5 11 95.854 0.144 33.0 0.3504 0.0000 OK 15 minute winter S5 2.001 S6 32.6 0.918 0.416 0.7570 15 minute winter S6 11 95.764 0.160 41.8 0.3229 0.0000 OK 15 minute winter S6 2.002 S7 41.2 1.113 0.526 1.6569 120 minute winter S7 88 95.660 0.355 31.3 0.5074 0.0000 OK 120 minute winter S7 1.003 S8 29.3 0.458 0.208 0.4687 120 minute winter S8 88 95.659 0.375 29.3 0.6629 0.0000 SURCHARGED 120 minute winter S8 1.004 Outfall 11.7 0.782 0.083 0.6109 90.4 120 minute winter Outfall 90 95.152 0.072 11.7 0.0000 0.0000 OK 120 minute winter Atten Tank 88 95.659 0.359 18.1 40.8500 0.0000 OK 120 minute winter Atten Tank 3.000 S8 -18.1 -0.410 -0.131 0.3643 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Alan Traynor Consulting File: Tranor Derek flow design.pfd Network: Storm Network Jake Blewitt 01/09/2026 Page 5 Flow+ v18.0 Copyright © 1988-2026 Causeway Technologies Ltd Results for 10 year +20% CC Critical Storm Duration. Lowest mass balance: 99.65% Node Event US Node Peak (mins) Level (m) Depth (m) Inflow (l/s) Node Vol (m³) Flood (m³) Status Link Event (Upstream Depth) US Node Link DS Node Outflow (l/s) Velocity (m/s) Flow/Cap Link Vol (m³) Discharge Vol (m³) 15 minute winter S1 10 97.056 0.156 43.0 0.5941 0.0000 OK 15 minute winter S1 1.000 S2 42.2 1.070 0.539 3.5545 15 minute winter S2 11 96.628 0.175 48.7 0.2560 0.0000 OK 15 minute winter S2 1.001 S3 47.8 1.346 0.610 1.4493 15 minute winter S3 11 96.378 0.128 64.0 0.2396 0.0000 OK 15 minute winter S3 1.002 S7 63.3 1.428 0.384 1.9492 15 minute winter S4 10 96.038 0.138 35.3 0.4564 0.0000 OK 15 minute winter S4 2.000 S5 34.5 0.816 0.440 1.6220 120 minute winter S5 96 95.981 0.271 21.9 0.6583 0.0000 OK 120 minute winter S5 2.001 S6 22.1 0.846 0.282 1.4532 120 minute winter S6 98 95.981 0.377 28.5 0.7613 0.0000 SURCHARGED 120 minute winter S6 2.002 S7 27.9 0.771 0.356 3.1498 120 minute winter S7 96 95.979 0.674 52.3 0.9648 0.0000 SURCHARGED 120 minute winter S7 1.003 S8 49.8 0.502 0.353 0.4739 120 minute winter S8 96 95.978 0.694 49.8 1.2270 0.0000 SURCHARGED 120 minute winter S8 1.004 Outfall 12.0 0.787 0.085 0.6202 153.5 30 minute winter Outfall 47 95.153 0.073 12.0 0.0000 0.0000 OK 120 minute winter Atten Tank 98 95.978 0.678 38.2 82.3528 0.0000 SURCHARGED 120 minute winter Atten Tank 3.000 S8 -38.2 -0.592 -0.276 0.3672 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Alan Traynor Consulting File: Tranor Derek flow design.pfd Network: Storm Network Jake Blewitt 01/09/2026 Page 6 Flow+ v18.0 Copyright © 1988-2026 Causeway Technologies Ltd Results for 30 year +20% CC Critical Storm Duration. Lowest mass balance: 99.14% Node Event US Node Peak (mins) Level (m) Depth (m) Inflow (l/s) Node Vol (m³) Flood (m³) Status Link Event (Upstream Depth) US Node Link DS Node Outflow (l/s) Velocity (m/s) Flow/Cap Link Vol (m³) Discharge Vol (m³) 15 minute winter S1 10 97.082 0.182 54.4 0.6898 0.0000 OK 15 minute winter S1 1.000 S2 53.4 1.129 0.682 4.2548 15 minute winter S2 11 96.657 0.204 61.6 0.2985 0.0000 OK 15 minute winter S2 1.001 S3 60.7 1.426 0.775 1.7328 15 minute winter S3 11 96.397 0.147 81.2 0.2748 0.0000 OK 15 minute winter S3 1.002 S7 80.6 1.475 0.489 2.0810 180 minute winter S4 148 96.244 0.344 12.6 1.1398 0.0000 SURCHARGED 180 minute winter S4 2.000 S5 12.6 0.669 0.161 2.6759 180 minute winter S5 148 96.243 0.533 21.1 1.2967 0.0000 SURCHARGED 180 minute winter S5 2.001 S6 20.2 0.814 0.258 1.4905 180 minute winter S6 148 96.243 0.639 26.1 1.2920 0.0000 SURCHARGED 180 minute winter S6 2.002 S7 23.8 0.665 0.304 3.1498 180 minute winter S7 148 96.242 0.937 46.6 1.3408 0.0000 SURCHARGED 180 minute winter S7 1.003 S8 45.8 0.473 0.324 0.4739 180 minute winter S8 152 96.242 0.958 45.8 1.6927 0.0000 SURCHARGED 180 minute winter S8 1.004 Outfall 12.0 0.787 0.085 0.6201 220.0 600 minute summer Outfall 315 95.153 0.073 12.0 0.0000 0.0000 OK 180 minute winter Atten Tank 148 96.241 0.941 33.0 116.5990 0.0000 SURCHARGED 180 minute winter Atten Tank 3.000 S8 -33.0 -0.493 -0.239 0.3672 REC E I V E D : 1 7 / 0 9 / 2 0 2 6 Alan Traynor Consulting File: Tranor Derek flow design.pfd Network: Storm Network Jake Blewitt 01/09/2026 Page 7 Flow+ v18.0 Copyright © 1988-2026 Causeway Technologies Ltd Results for 100 year +20% CC Critical Storm Duration. Lowest mass balance: 99.21% Node Event US Node Peak (mins) Level (m) Depth (m) Inflow (l/s) Node Vol (m³) Flood (m³) Status Link Event (Upstream Depth) US Node Link DS Node Outflow (l/s) Velocity (m/s) Flow/Cap Link Vol (m³) Discharge Vol (m³) 15 minute winter S1 10 97.118 0.218 70.3 0.8290 0.0000 OK 15 minute winter S1 1.000 S2 68.9 1.188 0.880 5.2122 15 minute winter S2 11 96.701 0.248 79.5 0.3617 0.0000 OK 15 minute winter S2 1.001 S3 78.1 1.470 0.998 2.1348 180 minute winter S3 168 96.598 0.348 30.9 0.6523 0.0000 SURCHARGED 180 minute winter S3 1.002 S7 30.9 1.083 0.188 2.8017 180 minute winter S4 168 96.599 0.699 16.3 2.3197 0.0000 SURCHARGED 180 minute winter S4 2.000 S5 15.5 0.674 0.198 2.6759 180 minute winter S5 168 96.599 0.889 26.0 2.1628 0.0000 SURCHARGED 180 minute winter S5 2.001 S6 24.0 0.824 0.306 1.4905 180 minute winter S6 168 96.598 0.994 31.6 2.0105 0.0000 SURCHARGED 180 minute winter S6 2.002 S7 30.8 0.675 0.394 3.1498 180 minute winter S7 160 96.597 1.292 60.9 1.8490 0.0000 SURCHARGED 180 minute winter S7 1.003 S8 59.5 0.539 0.422 0.4739 180 minute winter S8 168 96.598 1.314 59.5 2.3223 0.0000 SURCHARGED 180 minute winter S8 1.004 Outfall 12.0 0.787 0.085 0.6202 254.0 1440 minute winter Outfall 840 95.153 0.073 12.0 0.0000 0.0000 OK 180 minute winter Atten Tank 168 96.597 1.297 47.7 162.8933 0.0000 SURCHARGED 180 minute winter Atten Tank 3.000 S8 -47.7 -0.549 -0.345 0.3672 Water Quality (TSS) Node Treatment Effectiveness SuDS Component Mitigation TSS Cumulative TSS Atten Tank Outfall Carpark 1.0 Permeable Surface 0.700 0.000 0.000 Water Quality (Metals) Node Treatment Effectiveness SuDS Component Mitigation Metals Cumulative Metals Atten Tank Outfall Carpark 1.0 Permeable Surface 0.600 0.000 0.000 Water Quality (Hydrocarbons) Node Treatment Effectiveness SuDS Component Mitigation Hydrocarbons Cumulative Hydrocarbons Atten Tank Outfall Carpark 1.0 Permeable Surface 0.700 0.000 0.000 REC E I V E D : 1 7 / 0 9 / 2 0 2 6