HomeMy WebLinkAbout2560402 - F.I. Received Doc. - Application - Cover Letter
Phone: 049-4371447/9
Fax: 049-4371451
E-mail: info@clw.ie
The Mews,
23 Farnham Street,
Cavan,
Co. Cavan
CLW Environmental Planners Ltd.
Directors: S. Clarke, O. Leddy B.Agr.Sc., P. Fay B.Agr.Sc.
V.A.T. Reg. No. 8277204J
Planning Department,
Monaghan County Council,
County Offices,
The Glen,
Monaghan.
27th March 2026
RE: Planning application for Trevor McBride.
Development Address ~ Shanemullagh, Clontibret, Co. Monaghan.
Your Ref: 25/60402
Dear Sir/Madame
I refer to the planning application for development on an existing poultry farm, made on behalf of Mr.
Trevor McBride and your subsequent correspondence in relation to same dated 4th February last. Please
find detailed below the response to the issues raised.
1.
The applicant is requested to submit a comprehensive Surface water drainage design that takes into
consideration the 5 Surface Water Drainage Polices as detailed in the Monaghan Development Plan
2025 to 2031.
A) Submit a detailed drainage design and report outlining the determination of Qbar for the
proposed development, the design/report should include the following:
I. Hydraulic design of storm runoff to be attenuated to be calculated on the basis of in 100 -year
storm return period (critical storm) and account for climate change.
II. Proposals to be submitted of design details, structural drawings and proposals for
construction of an attenuation storage system capable of retaining the additional storm
runoff which will be generated from the proposed development. Location of the propose d
attenuation tank/system and “Hydro brake”™, or similar approved, facility to be clearly
indicated on the site layout plan.
III. Surface water drainage calculations including detailed hydraulic analysis of the development
for stormwater sewer collection and disposal system providing verification that the gradients
and pipes sizes will produce flow velocities lying in the range betwe en 0.75m/s and 3.0m/s.
The drainage design schedule shall include the design capacity, the actual drainage capacity
required, the velocity, the water volume and the spare capacity for each drainage run.
IV. Separate Longitudinal sections to an approved scale for each of all proposed surface water
storm sewers indicating the following: pipe material and diameter, invert level and cover
levels of manholes, location of manholes and valves, existing & proposed gr ound levels,
gradients & chainages, bedding and surround details.
V. Attenuation storage calculations. RECEIVED: 27/03/2026
Phone: 049-4371447/9
Fax: 049-4371451
E-mail: info@clw.ie
The Mews,
23 Farnham Street,
Cavan,
Co. Cavan
CLW Environmental Planners Ltd.
Directors: S. Clarke, O. Leddy B.Agr.Sc., P. Fay B.Agr.Sc.
V.A.T. Reg. No. 8277204J
VI. Longitudinal section through the proposed attenuation storage tank clearly indicating design
and all invert and cover levels of storage system, invert level of inlet and outlet pipelines to
and from the system, invert level of discharge pipeline downstream of attenuation system,
existing and proposed ground levels to be clearly shown.
VII. Location of the proposed attenuation tank/system and “Hydrobrake™’’, or similar approved,
facility to be clearly indicated on the site layout plan.
VIII. Detailed management proposals in respect of the ongoing maintenance of any attenuation
structures shall be submitted. This shall address the ongoing maintenance of all SUDS
elements, storage, flow control devices, the removal of grit, debris and silt from structures,
manholes and gullies, Health and Safety and Waste legislation. It shall include a resourced
schedule of programmed maintenance covering both the development and post development
phases of the works (this may not be applicable if this is a MCC s cheme but a plan on
maintenance and operation (M&O Manual) would still be required if being handed over to
MCC as an asset).
IX. Inclusion and location of approved Class 1 by pass oil interceptor incorporating oil level alarm
system on storm sewer discharge pipeline from this development prior to discharge from this
site , located prior to discharge to the attenuation systems , details of proposed system along
with location on site layout plan to be submitted to the planning authority. The oil interceptor
installed shall be capable of handling the flows equivalent to, or greater than, the maximum
storm runoff possible from this premises/development. A regular inspection and
maintenance/desludging programme shall be implemented whereby oil/solid/debris trapped
within the interceptor will be removed and disposed of offsite by an appropriate waste
disposal contractor.
X. x. All works to comply with Monaghan County Council Storm Water Technical Guidance
Document 2017 including construction details for manhole construction including drop
manhole, bedding & surround of pipelines.
Please refer to enclosed report and Drawings by Traynor Environmental.
2.
The Municipal District Road Engineer has concerns in relation to the distance an HGV or other vehicles
must travel from the junction of R-184-1 along the LT-33302 to the site with no pull in space available
for 410m. In this regard the applicant is requested to submit how it is proposed to address this issue,
which should include a swept path analysis illustrating the turning movements of HGV vehicles both
entering and exiting the site in both directions at the proposed entrance.
The applicant has discussed the development with the local MD area office, and based a review of the
proposed additional traffic movements pertaining to the access road leading to the farm. Additional
detail pertaining to the site access/egress is detailed on the revised plans as enclosed.
RECEIVED: 27/03/2026
Phone: 049-4371447/9
Fax: 049-4371451
E-mail: info@clw.ie
The Mews,
23 Farnham Street,
Cavan,
Co. Cavan
CLW Environmental Planners Ltd.
Directors: S. Clarke, O. Leddy B.Agr.Sc., P. Fay B.Agr.Sc.
V.A.T. Reg. No. 8277204J
3. The proposed development is considered insufficient in terms of the environmental
information provided. In this regard, the applicant is requested to submit:
• An up-to-date Nutrient Management Plan Assessment demonstrating that the available spread
lands have the capacity to accept soiled waters arising from the development.
As detailed in the EIAR, the stocking rate for 2024 was 118 kg/ha on 39.2 Ha.
The updated statement shows Jan – Nov 2025 was 112 kg Organic N/HA (Corrected to year end = 122
Kg organic N/Ha, a marginal increase on 2024.
The application of c. 95 m3 of soiled water with an estimated N content of 1 Kg Organic N/Ha will
increase this organic N loading to c. 124.7 ( as opposed to 120-120.5 Kg Organic N/Ha as detailed in the
EIAR) and remaining well inside the 170 Kg Organic N/Ha limit.
• Details of the outlet for manure arising from the proposed development to include the
destination(s) and the purpose for which the manure will be used.
Manure from this farm will be used as an organic fertiliser, typically on Tillage lands. All manure is to
be removed by a DAFM registered contractor with the relevant records as required by S.I. 588 of 2025
to be provided, as detailed in the application. The customer farmers may change in line with demand
(as per any commercial relationship between them and the approved contractor ). Also the manure
may be used in Anaerobic Digestion or other such facilities in response to demand.
• Details on the outlet for dead birds from the proposed development. The address on the letter
submitted with the application is Downs, Clontibret, Co. Monaghan which is inconsistent with
the proposed development address.
Please refer to updated letter enclosed from College Proteins. RECEIVED: 27/03/2026
Phone: 049-4371447/9
Fax: 049-4371451
E-mail: info@clw.ie
The Mews,
23 Farnham Street,
Cavan,
Co. Cavan
CLW Environmental Planners Ltd.
Directors: S. Clarke, O. Leddy B.Agr.Sc., P. Fay B.Agr.Sc.
V.A.T. Reg. No. 8277204J
Should you have any queries in relation to this, or, require any further information please do not hesitate
to contact me at the above number.
RECEIVED: 27/03/2026
Phone: 049-4371447/9
Fax: 049-4371451
E-mail: info@clw.ie
The Mews,
23 Farnham Street,
Cavan,
Co. Cavan
CLW Environmental Planners Ltd.
Directors: S. Clarke, O. Leddy B.Agr.Sc., P. Fay B.Agr.Sc.
V.A.T. Reg. No. 8277204J
Yours Faithfully,
Paraic Fay B.Agr.Sc. RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
26/115 TE
25th March 2026
Monaghan County Council
Planning Department
Dublin Street
Monaghan
Re: Planning and Development Act 2000 (as amended).
Planning and Development Regulations 2001 (as amended).
25/60402 - planning permission to construct 1 No. poultry house together with all ancillary structures (to
include meal storage bin(s)) and site works associated with the development This application
relates to a development which is for the purposes of an activity requiring a licence under part
IV of the environmental protection agency (Licensing) regulations 1994 to 2013. An
environmental impact assessment report (E.I.A.R) will be submitted with the planning application
at Shanemullagh, Clontibret, Co. Monaghan.
Dear Sir/Madam,
I refer to your letter dated 24th November 2025, we now comment as follows
Item 1 - The applicant is requested to submit a comprehensive Surface water drainage design that takes
into consideration the 5 Surface Water Drainage Polices as detailed in the Monaghan Development Plan
2025 to 2031.
a)Submit a detailed drainage design and report outlining the determination of Qbar for the proposed
development, the design/report should include the following:
i.Hydraulic design of storm runoff to be attenuated to be calculated on the basis of in 100-year storm
return period (critical storm) and account for climate change.
ii.Proposals to be submitted of design details, structural drawings and proposals for construction of an
attenuation storage system capable of retaining the additional storm runoff which will be generated from
the proposed development. Location of the proposed attenuation tank/system and “Hydro brake”™, or
similar approved, facility to be clearly indicated on the site layout plan.
iii.Surface water drainage calculations including detailed hydraulic analysis of the development for
stormwater sewer collection and disposal system providing verification that the gradients and pipes sizes
will produce flow velocities lying in the range between 0.75m/s and 3.0m/s. The drainage design
schedule shall include the design capacity, the actual drainage capacity required, the velocity, the
water volume and the spare capacity for each drainage run.
iv.Separate Longitudinal sections to an approved scale for each of all proposed surface water storm
sewers indicating the following: pipe material and diameter, invert level and cover levels of manholes,
location of manholes and valves, existing & proposed ground levels, gradients & chainages, bedding
and surround details.RECEIVED: 27/03/2026
2
v. Attenuation storage calculations.
vi. Longitudinal section through the proposed attenuation storage tank clearly indicating design and all
invert and cover levels of storage system, invert level of inlet and outlet pipelines to and from the system,
invert level of discharge pipeline downstream of attenuation system, existing and proposed ground levels
to be clearly shown.
vii. Location of the proposed attenuation tank/system and “Hydrobrake™’’, or similar approved, facility
to be clearly indicated on the site layout plan.
viii. Detailed management proposals in respect of the ongoing maintenance of any attenuation structures
shall be submitted. This shall address the ongoing maintenance of all SUDS elements, storage, flow control
devices, the removal of grit, debris and silt from structures, manholes and gullies, Health and Safety and
Waste legislation. It shall include a resourced schedule of programmed maintenance covering both the
development and post development phases of the works (this may not be applicable if this is a MCC
scheme but a plan on maintenance and operation (M&O Manual) would still be required if being handed
over to MCC as an asset).
ix. Inclusion and location of approved Class 1 by pass oil interceptor incorporating oil level alarm system
on storm sewer discharge pipeline from this development prior to discharge from this site , located prior
to discharge to the attenuation systems , details of proposed system along with location on site layout
plan to be submitted to the planning authority. The oil interceptor installed shall be capable of handling
the flows equivalent to, or greater than, the maximum storm runoff possible from this
premises/development. A regular inspection and maintenance/desludging programme shall be
implemented whereby oil/solid/debris trapped within the interceptor will be removed and disposed of
offsite by an appropriate waste disposal contractor.
x. All works to comply with Monaghan County Council Storm Water Technical Guidance Document 2017
including construction details for manhole construction including drop manhole, bedding & surround of
pipelines.
Response – In response to Item 1 of the Further Information request, the Applicant has prepared and
submitted a comprehensive Surface Water Drainage Design Report together with all associated
drawings and calculations. The submission includes determination of QBar, hydraulic analysis for the 100-
year storm event including 20% climate change, detailed attenuation storage calculations, design
details and structural information for the proposed attenuation system and flow control device,
longitudinal sections of all proposed surface water sewers and the attenuation structure, pipe sizing and
velocity verification, oil interceptor details, and a maintenance and management plan. The location of
the proposed attenuation system and flow control device are clearly indicated on the updated site
layout drawings. All proposals have been designed in accordance with the Monaghan Development
Plan 2025–2031 and the Monaghan County Council Storm Water Technical Guidance Document (2017).
Should you require any further information, please do not hesitate to contact me.
Yours sincerely,
Nevin Traynor
BSc Env, HDIP IT, Cert SHWW, IAH RECEIVED: 27/03/2026
Surface Water Drainage Report
Client: Trevor McBride
Project: Shanemullagh, Clontibret, Co. Monaghan
Date: 25th March 2026
1.0 Introduction
water management, attenuation storage and discharge control for the proposed development at Shanemullagh.
The purpose of this assessment is to:
Quantify post-development runoff from impermeable areas;
Determine the required attenuation storage volume for the 100-year return period event including a 20%
climate change allowance;
Demonstrate that post-development runoff will be restricted to greenfield runoff rates;
Confirm that discharge to the receiving stream at the northern boundary will be controlled and managed
in accordance with best practice SuDS principles.
The drainage strategy has been developed using recognised hydrological methods in accordance with SuDS best
practice to attenuation provision.
2.0 Hydrological Methodology
Surface water runoff has been assessed using:
Flood Studies Report (FSR) rainfall methodology
IH124 method for greenfield runoff estimation (QBAR = 0.00108 × A^0.89 × SAAR^1.17 × SPR^2.17)
The following rainfall parameters have been adopted:
Rainfall Method: FSR
M5-60: 17.0 mm
Ratio R: 0.30
Coefficient of Variation (CV): 0.75
Climate Change Allowance: +20%
Storm durations assessed: 15 minutes to 1440 minutes
Return periods assessed: 1, 10, 30 and 100 years
The IH124 method was used to estimate the greenfield runoff rate (QBar), based on:
Site area
Soil Index
Standard Average Annual Rainfall (SAAR)
Percentage impermeability
The calculated greenfield runoff rate for the site is:
QBar = 2.6 litres/second
This rate has been adopted as the maximum allowable discharge from the developed site.
RECEIVED: 27/03/2026
Surface Water Drainage Report
2
3.0 Site Catchment Characteristics
Total Site Area: 9,757 m² (0.9757 ha)
Impermeable Area Draining to Attenuation: 4,462 m² (0.4462 ha)
Impermeable coverage = 46%
All roof and hardstanding areas will discharge via a piped system to the attenuation structure. No direct uncontrolled
discharge to the receiving stream will occur.
The remaining pervious areas will continue to drain naturally via infiltration and overland flow consistent with existing
conditions. A BRE365 infiltration test was undertaken at the site in accordance with BRE Digest 365 to assess the
suitability of the underlying soils for stormwater disposal. The testing confirmed that infiltration is feasible at this location,
with a recorded infiltration rate of approximately 0.00068 m/s, and that soakaway drainage could be utilised for
surface water disposal.
Notwithstanding the positive infiltration results, the proposed drainage strategy for the development adopts an
attenuation system with controlled discharge. This approach has been selected to provide a managed and controlled
outflow, ensure compliance with greenfield runoff rates, and deliver a robust and maintainable drainage solution for
the developed impermeable areas of the site.
4.0 Design Storm and Storage Requirement
Hydrological modelling of the impermeable catchment (0.4462 ha) indicates that total attenuation storage required
to accommodate the 100-year return period storm event including 20% climate change is:
198 m³
The critical storm duration governing the storage requirement occurs within the long-duration storm range (typically
360 480 minutes for similar catchment characteristics).
Storage calculations are based on balancing inflow hydrographs against a restricted outflow of 2.6 l/s.
5.0 Rainwater Harvesting Contribution
A 5,000-gallon rainwater harvesting tank is incorporated within the development.
For calculation purposes, this has been assumed to be:
5,000 imperial gallons = 22.7 m³
This volume contributes toward the total attenuation requirement prior to overflow to the main attenuation system.
After deducting the harvesting tank volume, the additional storage required is:
198 m³ 22.7 m³ = approximately 175 m³
This ensures that discharge from the site remains restricted to the greenfield runoff rate.
6.0 Proposed Attenuation System
The proposed attenuation system comprises modular StormTech MC-4500 chambers installed within a clean, crushed
angular stone surround.
The system provides both chamber storage and additional void storage within the surrounding stone.
RECEIVED: 27/03/2026
Surface Water Drainage Report
3
Storage Capacity
Minimum installed storage per MC-4500 chamber (including stone void contribution):
4.60 m³ per chamber
To provide approximately 170 m³ additional attenuation:
175 8 chambers
For design robustness, the system will comprise approximately 39 MC-4500 chambers arranged in a two-row
configuration to suit the available site footprint.
7.0 Indicative Footprint and Construction Depth
A practical multi-row layout results in the following indicative dimensions:
Length: ~26.5 metres
Width: ~6.9 metres
Overall Construction Depth: ~2.3 metres
Overall depth comprises:
Foundation stone layer
Chamber height
Cover stone layer
Final excavation depth will be confirmed at detailed design stage subject to ground levels and outfall invert
confirmation.
Minimum stone grading requirements
Geotextile wrapping
Compaction standards
Structural loading considerations
The attenuation system footprint has been optimised to reduce the overall length while maintaining the required
storage volume, thereby improving constructability and integration within the proposed site layout.
8.0 Discharge Control
Discharge from the attenuation system will be restricted to:
2.6 litres per second (QBar)
A suitable flow control device (hydrobrake or calibrated orifice plate) will be installed within a control chamber
downstream of the attenuation system.
The control will be sized to operate under low head conditions to ensure effective restriction at the available hydraulic
gradient.
9.0 Outfall Arrangement
Controlled discharge will outfall to the existing stream located at the northern boundary of the site.
The outfall will include:
Headwall or suitable pipe termination detail
Erosion protection measures RECEIVED: 27/03/2026
Surface Water Drainage Report
4
Non-return protection if required
In exceedance events beyond the design capacity, overland flow will follow natural site gradients toward the stream
without impacting structures or third-party lands.
10.0 Exceedance and Flood Risk Management
The system has been designed for the 100-year storm event including 20% climate change.
In the unlikely event of exceedance beyond this event:
Surface water will surcharge locally within the yard area;
Finished floor levels are set above surrounding ground levels;
Overland exceedance routing follows natural fall toward the receiving stream.
The development does not increase downstream flood risk.
11.0 Maintenance and Management
The proposed surface water drainage system will require periodic inspection and maintenance to ensure its continued
effective operation throughout the lifetime of the development. The drainage infrastructure incorporates Sustainable
Drainage System (SuDS) elements including an attenuation storage system, flow control device, manholes, catchpits
and associated stormwater drainage pipework.
A structured maintenance regime will be implemented to ensure that the attenuation system continues to operate at
its designed capacity and that the risk of blockage, sediment accumulation or mechanical malfunction is minimised.
Routine Inspection and Maintenance
The following maintenance activities will be undertaken as part of the ongoing management of the drainage system:
Routine inspection of the attenuation storage system to check for sediment build-up or blockages.
Inspection of inlet and outlet chambers to ensure unobstructed flow.
Annual inspection and testing of the flow control device (Hydrobrake or equivalent) to ensure correct
operation.
Periodic inspection of catchpits, gullies and manholes for accumulation of grit, debris or silt.
Removal of accumulated sediments, grit and debris from catchpits, gullies and drainage structures as
required.
Inspection of the drainage system following significant rainfall events to confirm correct operation of the
attenuation and discharge control system.
The modular chamber attenuation system allows access for inspection and cleaning using standard jetting equipment
where required.
Health and Safety and Waste Management
All inspection and maintenance activities will be undertaken in accordance with relevant Health and Safety
legislation, including safe access procedures where confined spaces are involved. Materials removed during
maintenance operations, including silt, grit and debris, will be collected and disposed of in accordance with
applicable Waste Management and Environmental Protection legislation by appropriately authorised waste
contractors where required.
RECEIVED: 27/03/2026
Surface Water Drainage Report
5
The following programmed maintenance schedule will be implemented to ensure the long-term operational
performance of the surface water drainage system:
Maintenance Schedule
Element Maintenance Activity Frequency
Attenuation storage system Inspection of inlet/outlet
connections and sediment
accumulation
Annually
Flow control device Operational inspection and testing Annually or as required
Catchpits and gullies Removal of grit, debris and silt Annually
Manholes Inspection and cleaning Annually
Surface water drainage network Inspection following significant
storm events
As required
Long-Term Management
Responsibility for the ongoing maintenance and operation of the surface water drainage infrastructure will rest with
the site owner/operator. Maintenance records will be retained to demonstrate that the drainage system continues to
operate in accordance with its design parameters.
Where required by the Planning Authority, a Maintenance and Operation (M&O) Manual will be prepared outlining
procedures for inspection, maintenance and record keeping for all elements of the surface water drainage system.
12.0 Oil Interceptor Provision
In accordance with the requirements of the Planning Authority and Monaghan County Council Storm Water Technical
Guidance Document (2017), a Class 1 bypass oil interceptor incorporating an oil level alarm system will be installed
on the surface water drainage network serving the development.
The interceptor will be located on the stormwater pipeline upstream of the attenuation system, prior to discharge to
the attenuation tank, as indicated on the accompanying site layout drawing. The purpose of the interceptor is to
remove hydrocarbons and associated contaminants from surface water runoff generated within the yard and
hardstanding areas of the development before the runoff enters the attenuation storage system and subsequently
discharges to the receiving watercourse.
The interceptor will be sized to ensure that it is capable of accommodating flows equal to or greater than the
maximum stormwater runoff generated by the development. The unit will comply with the requirements of BS EN 858
(Parts 1 and 2) for Class 1 oil separators, providing an effluent quality of less than 5 mg/l of oil under standard test
conditions.
The system will incorporate an automatic oil level alarm to provide early warning when oil storage capacity is
approaching its design limit. This will ensure that the unit can be serviced before its operational capacity is exceeded.
The final location and connection details are illustrated on the updated drainage layout drawing submitted with this
application.
Maintenance and Management:
A regular inspection and maintenance programme will be implemented to ensure the continued effective
operation of the oil interceptor. The maintenance regime will include:
Periodic inspection of the interceptor chamber and associated pipework; RECEIVED: 27/03/2026
Surface Water Drainage Report
6
Monitoring of the oil level alarm system;
Removal of accumulated oil, silt, grit and debris as required;
Routine desludging of the interceptor chamber.
All waste materials removed from the interceptor will be collected and disposed of off-site by an appropriately
licensed waste contractor in accordance with relevant environmental and waste management legislation.These
measures will ensure that the interceptor operates effectively throughout the lifetime of the development and
prevents hydrocarbon contamination of the downstream attenuation system and receiving watercourse.
The installation of the Class 1 oil interceptor will ensure that hydrocarbons and associated pollutants generated within
the development are effectively removed prior to discharge to the attenuation system and receiving watercourse.
This measure provides protection to the downstream drainage network and receiving waters and is consistent with
pollution prevention best practice and the surface water quality protection objectives of Monaghan County Council.
13.0 Compliance Statement
The proposed surface water drainage strategy:
Maintains post-development runoff at greenfield rates (2.6 l/s);
Provides attenuation storage for the 100-year event including 20% climate change;
Incorporates rainwater harvesting within the storage calculation;
Ensures controlled discharge to the receiving stream;
Applies SuDS principles through attenuation, controlled discharge and reuse.
The drainage design therefore represents an appropriate and sustainable surface water management solution and
14.0 Surface Water Drainage Design Schedule
The proposed surface water drainage network has been designed to convey runoff from the contributing
impermeable areas to the attenuation system in a controlled manner. Pipe gradients and diameters have been
selected to provide self-cleansing velocities while avoiding excessive flow velocities. The proposed surface water
drainage design has been developed such that flow velocities lie generally within the range of 0.75 m/s to 3.0 m/s, in
accordance with the requirements of the Planning Authority and Monaghan County Council Storm Water Technical
Guidance Document (2017).
Drain Run Pipe
Diameter Gradient Design Flow Full Bore
Capacity Velocity Spare
Capacity
SW1-SW2 225mm 1 in 150 12.0 l/s 31.0 l/s 0.86 m/s 19.0 l/s
SW2-SW3 225mm 1 in 120 18.0 l/s 34.0 l/s 0.96 m/s 16.0 l/s
SW3-SW4 300mm 1 in 200 28.0 l/s 78.0 l/s 1.10 m/s 50.0 l/s
SW4-SW5 300mm 1 in 150 36.0 l/s 90.0 l/s 1.27 m/s 54.0 l/s
SW5 Attenuation
Tank 300mm 1 in 100 45.0 l/s 110.0 l/s 1.55 m/s 65.0 l/s
Attenuation Tank-
Flow Control
Chamber
300mm 1 in 200 2.6 l/s (restricted) 78.0 l/s 0.78 m/s 75.4 l/s
Flow Control
Chamber - Outfall 300mm 1 in 150 2.6 l/s (restricted) 90.0 l/s 0.90 m/s 87.4 l/s
Commentary on Hydraulic Performance
The above schedule demonstrates that the proposed pipework has been sized to provide adequate hydraulic
capacity while maintaining flow velocities within acceptable design limits. All pipe runs provide capacity in excess of RECEIVED: 27/03/2026
Surface Water Drainage Report
7
the required design flow, thereby ensuring reserve hydraulic capacity within the network. The downstream discharge
from the attenuation system will be restricted to the greenfield runoff rate of 2.6 l/s by means of a suitable flow control
device.
RECEIVED: 27/03/2026
Surface Water Drainage Report
8
Appendix A
Hydraulic Calculations and Methodology
RECEIVED: 27/03/2026
Surface Water Drainage Report
9
A1. Greenfield Runoff Estimation IH124 Method
The greenfield runoff rate (QBar) has been estimated using the IH124 method in accordance with the Flood
Studies Report (FSR).
The IH124 equation is expressed as:
Where:
= Mean annual flood (l/s)
= Catchment area (ha)
= Standard Average Annual Rainfall (mm)
= Standard Percentage Runoff (dimensionless)
For this site:
Catchment area draining to attenuation: 0.4462 ha.
SAAR and SPR values adopted in accordance with regional FSR parameters.
SAAR: 1050 mm
SPR: 0.45
Soil Index: 0.45 (moderately impermeable soils)
Soil Index consistent with moderately impermeable soils
Using the above methodology, the calculated greenfield runoff rate is:
QBar = 2.6 litres/second
This value has been adopted as the maximum allowable discharge rate from the development.
A2. Post-Development Runoff Estimation
Post-development runoff from impermeable areas has been calculated using the Rational Method:
Where:
= Peak runoff (l/s)
= Runoff coefficient
= Rainfall intensity (mm/hr)
= Area (ha)
For impermeable surfaces:
Runoff coefficient
Area ha
Rainfall intensities were derived from FSR rainfall parameters (M5-60, Ratio R, CV) for storm durations ranging from
15 to 1440 minutes.
A3. Attenuation Storage Calculation
Attenuation storage has been determined using hydrograph routing principles, balancing inflow hydrographs
against a restricted outflow of 2.6 l/s.
Storage volume is calculated as:
Where:
= Inflow hydrograph
= Restricted discharge (2.6 l/s)
= Storm duration
The critical storm duration for storage typically occurs within longer duration storm events (commonly 360 480
minutes for catchments of this scale). RECEIVED: 27/03/2026
Surface Water Drainage Report
10
The total storage required to accommodate the 100-year return period event including 20% climate change is:
198 m³
A4. Rainwater Harvesting Adjustment
A rainwater harvesting tank of 5,000 imperial gallons (22.7 m³) is incorporated within the development.
This storage volume is deducted from the total required attenuation volume:
The rainwater harvesting tank primarily serves water reuse purposes but also provides temporary storage during
storm events prior to overflow to the attenuation system.
Accordingly, the additional attenuation storage required is:
Approximately 175 m³
A5. Modular Chamber Storage Calculation
The StormTech MC-4500 chamber system provides:
Chamber void storage.
Additional void storage within surrounding stone
Minimum installed storage per unit (including stone contribution):
4.60 m³ per chamber
Required number of chambers:
Total provided storage:
This provides compliance with the required attenuation volume.
A6. Discharge Control Verification
Discharge is restricted to:
2.6 l/s
The flow control device will be sized using the orifice equation:
Where:
= Discharge (m³/s)
= Coefficient of discharge
= Orifice area
= Gravitational acceleration
= Head above centre of orifice
The device will be selected to operate effectively under low head conditions consistent with site gradients.
A7. Climate Change Allowance
A 20% climate change allowance has been applied to rainfall intensities in accordance with standard practice.
This ensures that the system provides resilience against future rainfall intensity increases and long-term climate
variability.
RECEIVED: 27/03/2026
Surface Water Drainage Report
11
A8. Hydraulic Summary
Parameter Value
Contributing Area 0.4334 ha
QBar 2.6 l/s
100yr +20% Storage 198 m³
Rainwater Tank 22.7 m³
Additional Required Storage ~170 m³
Chambers Required 37 MC-4500
Discharge Rate 2.6 l/s
Tank Dimensions 26.5m x 6.9m x 2.3m
RECEIVED: 27/03/2026
College Proteins
1.17 1.36 1.45
1.18 1.38 1.48
1.19 1.39 1.49
1.20 1.39 1.49
1.20 1.39 1.49
1.19 1.38 1.47
1.18 1.37 1.45
1.18 1.36 1.44
1.17 1.35 1.43
1.16 1.30 1.37
* Z2 is a growth factor from M5 rainfalls
1.17 1.45 1.88
1.18 1.48 1.94
1.19 1.49 1.97
1.20 1.49 1.98
1.20 1.49 1.97
1.19 1.47 1.92
1.18 1.45 1.88
1.18 1.44 1.84
1.17 1.43 1.81
1.16 1.37 1.72
* Z2 is a growth factor from M5 rainfalls
Spreadsheet provided by: www.YourSpreadsheets.co.uk calculations are based on CIRIA C697 2007: The SUDS Manual
275.34
247.04 76.60 331.98 72.00 259.98
78.40 339.79 103.40 448.14 172.8014402.24 50.20 60.20 260.91
600 1.79 35.50 43.10 186.80
249.78
189.83 59.80 259.17 28.80 230.37
57.00
50.00 216.70 67.60 292.98 43.20360 1.60 30.70 37.50 162.53
240 1.45 26.60 32.60 141.29
194.93
121.35 39.10 169.46 7.20 162.26
43.80
35.00 151.69 48.30 209.33 14.40120 1.21 20.80 25.70 111.38
60 1.00 16.30 20.30 87.98
133.35
77.15 25.60 110.95 1.80 109.15
28.00
22.30 96.65 31.60 136.95 3.6030 0.80 12.70 16.00 69.34
15 0.63 10.00 12.60 54.61
92.85
47.24 15.60 67.61 0.60 67.01
17.80
15.20 65.88 21.70 94.05 1.20
10.90
10 0.52 8.50 10.70 46.37
5 0.37 6.10 7.70 33.37
REQUIRED STORAGE VOLUME PER RAINFALL DURATION FOR DISCHARGE RATE v2
1440 2.24 50.20 60.20 260.91
rainfalls
[mm]
rainfall
duration
[min]
rainfall
factor Z1
M5-D
rainfalls
[mm]
M10-D M30-D M100-D
inflow
[m 3 ]
outflow from
attenuation
tank [m 3 ]
required
storage
[m 3 ]Z2 rainfalls
[mm]
inflow
[m 3 ]Z2 rainfalls
[mm]
inflow
[m 3 ]Z2
247.04 72.00 175.04
195.46 50.00 216.70 43.20 173.50
71.30
51.50 223.20 57.00
309.01 78.40 339.79 172.80 166.99
600 1.79 35.50 43.10 186.80
360 1.60 30.70 37.50 162.53
161.03
135.65 35.00 151.69 14.40 137.29
45.10
39.40 170.76 43.80 189.83 28.80240 1.45 26.60 32.60 141.29
120 1.21 20.80 25.70 111.38
114.15
85.81 22.30 96.65 3.60 93.05
31.30
24.90 107.92 28.00 121.35 7.20
19.80
60 1.00 16.30 20.30 87.98
30 0.80 12.70 16.00 69.34
75.35
58.08 15.20 65.88 1.20 64.68
5 0.37 6.10 7.70 33.37
15.70 68.04 17.80 77.15 1.80
10 0.52 8.50 10.70 46.37 13.40
15 0.63 10.00 12.60 54.61
9.60 41.61 47.24 0.60
REQUIRED STORAGE VOLUME PER RAINFALL DURATION FOR DISCHARGE RATE v1
rainfall
duration
[min]
rainfall
factor Z1
M5-D
rainfalls
[mm]
M10-D M20-D M30-D outflow from
attenuation
tank [m 3 ]
required
storage
[m 3 ]Z2 rainfalls
[mm]
inflow
[m 3 ]Z2 rainfalls
[mm]
inflow
[m 3 ]Z2 rainfalls
[mm]
inflow
[m 3 ]
46.64
landscaping and/or green roof area 'A2' [m 2 ] =0 90.00 0
other partially permeable area 'A3' [m 2 ] =100.00 0
AREA DRAINED TO ATTENUATION TANK =4334 m2
10.90
allowance for climate change:20%
AREA DATA impermeability
[%]
effective area
[m 2 ]
impermeable area 'A1' [m 2 ] =4334 100.00 4334
M5-60 to M5-2d rainfall ratio 'r' =0.40 required storage volume for discharge rate 'v2' =275.34 m3
proposed discharge rate 'v1' [litre/s] =2.00
proposed discharge rate 'v2' [litre/s] =2.00
Section: Attenuation tank Prepared By:FMCM Date:24/02/2026
GENERAL DATA SUMMARY OF CALCULATIONS
site location:Ireland required storage volume for discharge rate 'v1' =175.04 m3
24 hour rainfall depth of 100year return period 'R' [mm] =100
Traynor Enviromental Ltd
Belturbet Business Park
Belturbet
Co. Cavan
Job Title
Revision A
Job No:TE Page:C/01RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
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RECEIVED: 27/03/2026
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RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
RECEIVED: 27/03/2026
105.46106.45106.09105.85103.44104.29104.65104.91104.77103.63103.74103.55103.00101.64102.26102.51102.87101.16101.17101.11101.07100.70100.60100.51100.15101.14100.0499.0599.56100.18100.28100.68100.58100.2199.8499.0999.1098.6598.48100.00100.52101.00100.3799.2799.08100.0098.6499.56100.27101.15101.32101.67101.46101.20100.85101.16100.94100.3598.88101.88101.92101.89101.94101.8792.0591.7291.5192.4199.22101.82101.8398.1193.6794.6195.3596.3697.3090.6391.1992.1792.99101.78101.70101.69101.76101.72101.70101.63101.12101.37101.19101.12101.46101.80102.17103.67PostTPTPTP101.74101.83101.75101.78101.75WMMkrBAACC6534[21'-5"]7964[26'-2"]Proposed Poultry Unit FFL; 10234397[112'-10"]9033[29'-8"]23298[76'-5"]700
0
[23']Location of Site Noticemarked XX25732[84'-5"]34034[111'-8"]Existing Poultry Unit FFL; 102TPTPLIGHTWELLCOURTYARDhidden door700065003000 LAWNACRECEIVED: 27/03/2026