Preliminary Design Report Appendix K Drainage Design Basis Document

Appendix K
Drainage Design
Basis Document
NTA
BusConnects Core Bus Corridor
Drainage Design Basis
Final | 26 November 2021
This report takes into account the particular

instructions and requirements of our client.
It is not intended for and should not be relied
upon by any third party and no responsibility
is undertaken to any third party.
Job number 268401
Ove Arup & Partners Ireland Ltd
Arup
50 Ringsend Road
Dublin 4
D04 T6X0
Ireland
www.arup.com
NTA BusConnects Core Bus Corridor
Contents
Page
1 Introduction 1
1.1 Background and Overview of the Project 1
1.2 General principles of drainage design 1
1.3 Method of design 3
2 Proposed drainage strategy 5

2.1 Relevant Standards and Guidance 5
2.2 Storm Water Management 7
2.3 Sustainable Drainage Systems (SuDS) 7
2.4 Pipe Materials 7
2.5 Distance between manholes 8
2.6 Clash Checks 8
2.7 Bedding Haunching and Surround 9
2.8 CBC design criteria 9
2.9 Gullies 11
Appendices
Appendix A
SuDS Eligibility
Appendix B
Bus Connects – Road run-off collection gullies
BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 | Arup

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BASIS\BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002.DOCX
1 Introduction
1.1 Background and Overview of the Project

This document has been prepared by the BusConnects Infrastructure Works Team.
The aim of the BusConnects programme is to transform Dublin’s bus system, with
the Core Bus Corridor (CBC) project aiming to provide 230kms of dedicated bus
lanes and 200km of cycle lanes on sixteen of the busiest bus corridors in and out
of the city centre. This project is fundamental to addressing the congestion issues
in the Dublin region with the population due to grow by 25% by 2040, bringing it
to almost 1.55m.
The CBC project will aim to implement an optimum project cross-section to
include footpaths, cycle tracks and bus lanes on both sides of the road throughout
the CBC network where feasible (see Figure 1). In some instances, this will
necessitate a Compulsory Purchase Order (CPO) process to include portions of
private land to achieve the project objectives.
Figure 1: Optimum Typical CBC Cross-Section
1.2 General principles of drainage design

• The existing drainage network will be maintained and used as the main
discharge point for the new drainage system. The idea of the design will be
replicating the existing situation. Where new multiple gully connections
discharging to a combine sewer are required, a new surface water pipe will be
provided where possible and connected to the combine sewer as per Irish
Water requirements.
• All drainage structures should be designed with a minimum return period of
no flooding in 1:30 years. A climate change allowance of 20% will be added
to all rainfall depths.
• Sustainable Urban Drainage Systems (SuDS) requirements. A SuDS drainage
design will be developed as a first preference and in accordance with the
SuDS hierarchy. Please refer to Appendix A: Drainage Design Criteria - SuDS
Eligibility of the current document.
BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 1

• At planning stage the design will be developed on the basis of existing

drainage records, site visits, google earth and some specific targeted surveys if
required. If available, additional information from DCC or Irish Water will be
reviewed and considered where relevant.
• Physical drainage investigations might be required at detailed design stage to
precise details of existing drainage along the route, the size, number, depth,
and location etc. of each drainage infrastructure present along the route.
• At Planning Stage infiltration rates have not been considered within the
calculations. The use of measures such as bioswales or tree pits will be
promoted where appropriate. Permeability tests will be completed at detailed
design so that infiltration rates can be considered in the calculations during
detailed design stage.
• The design will be based on avoiding increasing the discharge flow to an
existing network. An assessment of the necessity of possible attenuation to
restrict the flow rates to the current conditions should be developed at
planning stage. This assessment is further explained in Section 2.8. The
attenuation facilities will be provided in the shape of SuDS. Where spatial or
other constraints make the use of SuDS not feasible or not possible or when
SuDS do not provide enough attenuation, oversized pipes will be required.
• While the scheme will involve an increased paved area it is envisaged that
with Bus Connects in operation and better connectivity, a better public
transport system will further reduce traffic on the existing routes thus reducing
risk of pollution for the current situation. Where reasonably possible for
additional catchment areas, SuDS elements, such as bio-swales or tree-pits
will be implemented. This way, runoff will flow through porous layers that
will provide a level of treatment (and attenuation) before discharging into the
existing network. Please refer to Appendix A for further details. Where SuDS
are not possible or feasible all run-off from paved areas are proposed to be
collected in a positive drainage system, and not be discharged over the edge of
embankments. Spillways are not therefore proposed.
• Narrow filter drains or fin drains are not expected for inner city roads. An
assessment of the provision of subgrade drainage will be developed where
necessary.
• Existing drainage gullies located in the bus lane or cycle track should be
removed when necessary and reused where possible. Side-entry kerb
drainage/side-entry gullies should be considered for all new kerblines that
must accommodate rainwater run-off. Existing gully connections will be used
where possible. The drainage design will ensure that not ponding occurs along
the routes.

Figure 2: Side gullies
Figure 3: Typical Cross section. Kerb between the Bus lane/carriageway and the cycle
track.
1.3 Method of design

The drainage calculation is carried out using MicroDrainage from Innovyze,
which is the most widely used drainage design software in the UK and Ireland.
The software uses the ‘Modified Rational Method’ to calculate run off from an
impermeable area for a storm of a particular return period.
The drainage design for each CBC route shall be developed by using one of the
following techniques.
The Irish Water models can be used to develop the

drainage design where it includes comprehensive and
1. Irish Water Model
known details of the existing surface and combined
sewer networks.
A MicroDrainage (WinDes) Model can also be used to

2. MicroDrainage (WinDes
develop the design. These models shall be developed,
Model)
as required, on a catchment-by-catchment basis

For very small catchments where hydraulic losses and

storage within the designed drainage network will be
3. Hand Calculations
negligible, hand calculations can be used to develop
the drainage design.
As appropriate, each method shall be used to:

• Determine the CBC runoff rates;
• Develop the drainage design including any SuDS to meet the requirements of
the Design Basis Document and applicable standards.
As noted elsewhere in this Design Basis Document, a SuDS drainage design shall
be developed as a first preference and in accordance with the SuDS hierarchy.
Direct discharge to an existing watercourse or drainage network shall only be
considered where an appropriate SuDS scheme cannot be developed due to
ground conditions or other local constraints, but in such a case online attenuation
will be included to control the discharge rate as appropriate. Please refer to
Appendix A containing SuDS Eligibility for further information.

2 Proposed drainage strategy
2.1 Relevant Standards and Guidance

It is noted that the purpose of this report is to complement, and not supersede,
existing guidance documents relating to the design of drainage in Greater Dublin.
A non-exhaustive list of these guidelines is outlined below:
• Greater Dublin Regional Code of Practice (GDRCoP)
• Greater Dublin Strategic Drainage Study (GDSDS).
• CIRIA The SuDS MANUAL (C753)
• DCC Drainage Planning Section for schemes running completely through
greenfield sites.
The following inputs sourced mainly from Met Éireann and GDSDS Volume 2
are used in the development of the drainage design. Table 1 below shows Rainfall
Design Criteria Variables.
Table 1: Rainfall Design Criteria Variables
Variable Value
Region Scotland/Ireland
Return Period Drainage Network: 1 in 1 no surcharge,
(GDSDS Volume 2, Section 6.2 and Drainage Drainage System: 1 in 100 no flooding in
Requirements for Planning Applications) greenfield areas only,
Drainage System: 1 in 30 years no flooding
for extending urban areas
M5-60 16.3
(Met Eireann. Return Period Rainfall Depths
for sliding Durations. Irish Grid: Easting
315887, Northing: 234669. Values derived
from a Depth Duration Frequency Model)
Ratio R 0.279
(Met Eireann. Return Period Rainfall Depths
for sliding Durations. Irish Grid: Easting
315887, Northing: 234669. Values derived
from a Depth Duration Frequency Model)
Minimum Global Time of Entry 4 minutes
(Recommendation for Site Development
Works for Housing Areas)
Max. Rainfall 50 mm/hr
(GDSDS Volume 2 Table 6.4 Surface Water
Design Criteria)
Max. Time of Concentration 30 minutes
(Wallingford Procedure States the Modified
Rational Method has only been tested for time
of concentration not greater than 30 minutes)
Climate Change 20%

Variable Value
(Dublin City Council Development Plan 2016-
2022 and Drainage Requirements for Planning
Applications)
Table 2 below summarises permeability factors to be used in the design.

Table 2: Runoff permeability factors
Runoff Permeability Factors

Location Value
Grassed Areas (Based on Dublin soil type 2) 0.3
Paved 1
Table 3 below summarises soil Standard Percentage Runoff (SPR) values.

Table 3: Soil SPR Values (GDSDS Volume 2, Table 6.7 SPR Values for Soil)
SOIL SPR Value

Soil type 1 0.1
Soil type 2 0.3
Soil type 3 0.37
Soil type 4 0.47
Soil type 5 0.53
Surface Water Design Criteria in accordance with GDSDS is summarized in Table

4 below:
Table 4: Surface Water Design Criteria (GDSDS Volume 2, Table 6.4 Surface Water
Design Criteria)
Table 4 above states minimum pipe sizes, minimum depth of cover, minimum
velocity and roughness coefficient.

Minimum slope requirement is set up a good practice as 1 in 500 or steeper. Self-

cleansing velocity will take preference.
Table 5 below provides typical values of QBAR per hectare for the typical SAAR
value for Dublin of 750mm for SOIL types 2, 3 and 4.
Table 5: QBAR values (GDSDS Volume 2, Table 6.5 Typical Values of QBAR for Dublin
based on 50ha)
2.2 Storm Water Management

It is important to check the effect (pollution, erosion and flooding) of the design
on the upstream and downstream infrastructure, especially where the natural run-
off is concentrated.
The storm water drainage within the CBC road reserve should thus be designed in
such a manner as to ensure that the run-off is conveyed in a controlled manner that
will not adversely affect upstream, adjacent or downstream properties.
Where the existing downstream system is clearly inadequate to accommodate the
excess storm water run-off from the drainage structures, the following storm water
management facilities must be investigated:
• The retarding of the run-off by means of detention facilities. The effect of
possible backwater must be checked and investigated (SuDS)
2.3 Sustainable Drainage Systems (SuDS)

Where possible, and in new areas of public realm gained as part of the design, a
sustainable drainage system should be considered in the form of rain gardens,
bioretention areas, filter drains, swales, tree pits, permeable paving etc. SuDS will
also be considered in existing areas where practicable and possible.
The Greater Dublin Strategic Drainage Study introduces SuDS and the available
techniques to control the quantity and quality of runoff. It provides guidance on
the selection of SuDS for particular sites and discusses issues such as operation
and maintenance, cost effectiveness, recreation and amenity, habitat potential and
safety.
A SuDS strategy will be extended further in Appendix A.
For operational purposes, it is recommended that the minimum throttle size for a
pipe should be 75mm and the minimum allowable flow rate should be 2l/s.
2.4 Pipe Materials

In accordance with GDRCoP Section 11.3, the following must be used in the
construction of main pipelines or connections from gullies or private drains.

The List below applies to all the Local Authorities apart from Dublin City Council
who do not approve the use of uPVC pipes in the public area.
• Concrete: Concrete sewer pipes with spigot and socket joints and rubber rings
fittings to comply with IS EN 1916 and IS 6 2004 or equivalent standard.
Class M or class H. 11.3.2.
• Clayware: Vitrified clay pipes and fittings must comply with the requirements
of I.S./EN 295-1/2/3:1992 or equivalent standard. Class 160 or 200. 11.3.3.
• uPVC: Unplasticised P.V.C. pipes must comply with the "Provisional
Specification for Soil Pipes, Drains, Sewers and Fittings made of unplasticised
P.V.C." issued by the Department of the Environment. B.S. 8005: Part 1
Sewerage or equivalent; B.S. 8010: Part 2 - Pipelines on land or equivalent:
design, construction and installation; B.S. 5955: Part 6 Code of Practice for
the Installation of unplasticised P.V.C. Pipework for Gravity Drains and
Sewers or equivalent EN1401 Unplasticised P.V.C. sewer pipe specification
B.S.4514 Unplasticised P.V.C. soil pipe specification Regulations 11.3.4.
• Other: The use of alternative pipe types requires the prior express written
approval of the relevant Local Authority.
• Pipe material should not change between manholes.
• The installation of sewers by pipejacking/drilling should have the prior written
approval of the relevant Local Authority.
• The Developer must obtain written permission from the relevant Local
Authority when pipes are to be laid in landfill, contaminated sites or on poor
ground.
2.5 Distance between manholes

In accordance with GDRCoP Section 11.6, the length of pipe-work from manhole
to manhole should not exceed 90metres.
2.6 Clash Checks

Existing services & utility drawings/models will be reviewed to support design
and proposed location of the various drainage elements within the bus connects
corridors. The vertical alignment of existing services and utilities will be
considered as far as reasonably practicable (i.e. from site investigations, as-built
files etc.). The potential risk from clash of service will be highlighted to the
Contractor within the preliminary safety and health plan, and the designer's risk
assessment. We are carrying out a utility survey before the planning application
that covers clashes with major, critical know utilities only. We are not carrying
out an extensive utility survey of all services before planning stage. This will be
carried out at a future date after the planning application is complete.

2.7 Bedding Haunching and Surround

In accordance with GDRCoP Section 11.8.1, all main pipelines shall be bedded,
haunched and surrounded to the requirements of the Local Sanitary Authority.
In accordance with GDRCoP Section 11.8, the recommended minimum depth of
cover over a main pipeline is 1.2m under carriageway and 0.9m elsewhere. If that
cannot be achieved, the pipes shall be fully surrounded in 150mm thick concrete
with an absolute minimum depth of cover of 750mm, see Figure 4. This applies to
both roadways and footpaths. Where concrete bedding is used it must be a
minimum of 150mm thick in-situ concrete, class 20N/20mm, and haunched half
way up the barrel of the pipe.
Figure 4: Trench bedding
2.8 CBC design criteria

According to GDSDS Volume 2 Section 6.2, the minimum level of service for the
existing network is a 1 in 5-years return period. Given that CBC takes place in a
fully urbanised area, it can be assumed that the existing network was designed
following these criteria.
The extra impermeable area associated with CBC interventions should be
attenuated before discharging to the existing drainage system, ensuring that both
the quantity and quality of runoff are appropriate. According to the available data,
not all networks can be characterised. Therefore, allowable discharge rates can be
assumed as a combination of a flow associated to a 1 in 5-years return period for
the existing paved areas plus 2l/s/ha for existing greenfield areas to be paved
(additional catchment areas). To achieve this, some SuDS and/or other attenuation
facilities such as oversized pipes can be implemented with an outflow control
equal to the allowable discharge rate. As a final step to the design process it
should be checked that no flooding occurs in the proposed infrastructure for a 1 in
30 year event plus a 20% of climate change allowance. A summary of these
design standards is provided in Table 6.

Table 6: Design Standards
Parameter & Feature Allowable Discharge Rate
Permitted Discharge Rates
Fully New Paved Catchment Discharge rates throttled to 2l/s/ha with minimum flow of 2l/s
Areas
Combined New/Existing Existing runoff rates maintained on the basis of:

Paved Catchment Areas
- the existing paved areas to 1 in 5-year flow, or as
informed by existing network/model information,
plus
- 2l/s/ha for the existing grassed areas catchments to be

paved (additional catchments).
Attenuation / SuDS Measures
Combined new/existing Attenuation/SuDS measures sized to contain the 1 in 30-year

paved areas storm with a 20% allowance for future climate change
Fully newly Paved (existing Attenuation/SuDS measures sized to contain the 1 in 100-year
greenfield) Areas storm with a 20% allowance for future climate change
Exceptions:
• Where attenuation measures are proposed in the floodplain, they shall be sized to contain
the 1 in 100-year storm plus climate change
• The design of attenuation/SuDS measures shall ensure no new flooding of properties.
• Above ground retention of water might be designed to the 1 in 100-year storm plus
climate change in situations where the flooding of existing properties might be
compromised.
The drainage system design must manage on site the quality of runoff to prevent
pollution in receiving surface waters and groundwaters. The type of SuDS is
chosen to achieve the water quality targets.
In areas where the catchment remains unchanged which implies that no additional
impermeable areas are proposed, the design will consist of relocating the gullies to
a suitable location. This location will be based on the water pathway that will
depend on highway alignment and tie-in requirements. A relevant number of
gullies will be located either at the kerb line between the cycle-track and the bus
lane, or at the kerb line between the footpath and the cycle track. Further, the
spacing of existing gullies will be reviewed to ensure that they are collecting the
appropriate run off area.

When schemes run completely through greenfield sites and thus they are not part
of an existing network, they will be considered a new development and GDSDS
Volume 2 and the Drainage Requirements for Planning Applications will be
adhered to.
2.9 Gullies
In accordance with Greater Dublin Regional Code of Practice for Drainage Works
Section 14, the following criteria will be adhered to:
• Gullies, gratings and frames shall conform to EN 124, Class D400 or
equivalent. Gullies shall be provided for every 200m2 of paved area at a
minimum, except for low points which may require additional gullies (SuDS
design may eliminate the need for gullies in various locations). (GDRCoP
Section 14.1)
• Connections from gullies discharging to a combined sewer shall be sealed and
from gullies discharging to surface water sewers can be unsealed.
• Interconnection between gullies shall not be permitted. Gully connections
shall need exceed 10m in length and shall connect to sewers in the direction of
the flow. An additional manhole shall be provided on gullies where the length
of the connection pipework is greater than 30m. If gullies are connected to
manholes, they shall connect at the benching level or a maximum of 500mm
above the invert of the main pipe (GDRCoP Sectioin 14.7

Appendix A
SuDS Eligibility
Technical Paper
CBC SuDS Eligibility
Project: BusConnects Job No:
Technical Paper SuDS Eligibility For Planning
Subject: Drainage Design Criteria - SuDS Date: 26th Nov 2021
Prepared by: Elena Calcerrada (GBM-TYPSA), Nick Stokes Version: Rev A

(JACOBS), Patricia Álvaro (TYPSA)
Drainage Design Criteria – SuDS Eligibility
The aim of this document is to provide a list of Sustainable Drainage Systems (SuDS) options,
as designing drainage solutions for the Core Bus Corridors (CBC) project. This document is
an appendix of the Drainage Design Criteria. This document has been developed by TYPSA,
Green Blue Management (GBM) and JACOBS.
1 LOCAL DRAINAGE GUIDANCE AND REFERENCES

The three main documents of the local drainage guidance are The Greater Dublin Strategic
Drainage Study (GDSDS), the Greater Dublin Regional Code of Practice for Drainage Works
(v6.0) and the DCC’s Drainage Requirements for Planning Applications.
The Greater Dublin Strategic Drainage Study (GDSDS) was completed in 2005 and
involved the seven Local Authorities of the Greater Dublin Area (GDA), which include Dublin
City, Fingal, South Dublin, Dun Laoghaire Rathdown, Meath, Wicklow and Kildare.
While the GDSDS policies remain the over riding documents, the Greater Dublin Regional
Code of Practice for Drainage Works (GDRCoP, v6.0) sets out the requirements of the
Local Authorities in a more concise format for day to day use. In this document, the drainage
Ref: 200408-SuDS-hierarchy For Planning – November 2021 Page 1 of 13

National Transport Authority BusConnects
ROD-Typsa JV CBC SuDS Eligibility
requirements are clearly summarised and, particularly, Sustainable Drainage Systems (SuDS)
are required in new developments.
Additional references that have been considered are:
• The Dublin City Development Plan 2016-2022. This Plan includes among its objectives
the promotion of more natural drainage solutions in line with the SuDS principles.
• Relevant Local Area Plans for all the Dublin Local Authorities
• The “Design Manual for Urban Roads and Streets” (https://www.dmurs.ie/).
Finally, it is important to remark that the use of SuDS techniques in urban environments is
also one of the key points of the EU policy on Natural Water Retention Measures (NWRM).
2 PRIORITY LEVEL
In addition to local design guidance including the Greater Dublin Strategic Drainage Study and
Greater Dublin Regional Code of Practice for Drainage Works, the CIRIA SuDS Manual
provides a useful reference for the design of SuDS. The CIRIA SuDS Manual notes that the
components of a SuDS scheme should not be thought of in isolation and but as an
interconnected system to intercept and manage runoff before it is discharged. The Manual
promotes the concept of the SuDS Management Train, as a sequence of components, to
collectively manage runoff. A schematic of the SuDS Management Train is provided in Table
1.
Scale SuDS Management Train
Rainwater Harvesting – capture and reuse within the local

environment
Source
Pervious Surfacing Systems – structural surfaces that allow
water to penetrate into the ground reducing discharge to a
drainage system e.g. pervious pavement
Less Preferred
Infiltration Systems – structures which encourage infiltration

into the ground e.g. Bioretention Basins
Site
Conveyance Systems – components that convey and control
the discharge of flows to downstream storage components
e.g. Swales
Regional Storage Systems – components that control the flows before

discharge e.g. attenuation ponds, tanks or basins
Ref: 19.117.100-FIN1 For Planning – November 2021 Page 2 of 13

Table 1 – The SuDS Management Train. Source: produced by Jacobs from CIRIA SuDS Manual 2015
The CIRIA SuDS Manual recommends that when considering SuDS solutions, the preferred
approach should be to manage runoff using Source scale solutions where reasonably
practicable. Where Source type solutions cannot fully address an increase in runoff from a
development, residual flows are discharged to be managed at the Site and then Regional
scales.
During Jacobs’s recent consultation on the MetroLink drainage design, a key point raised by
external Stakeholders was to demonstrate that a SuDS hierarchy had been fully considered
in developing the drainage design. This meant that Source and then Site scale solutions had
to be fully investigated and shown to be unsuitable before Regional solutions could be
considered. Similarly, where a Source or Site scale solution could partially mitigate an
increase in runoff this should be progressed to reduce the size of any Regional scale solutions.
Whilst it was recognised that many Source or Site scale solutions might not be suitable to
linear infrastructure projects in a constrained urban environment, full documentation of the
decision-making process was required to demonstrate compliance with best practice. At a
high level, this document is intended to provide a framework for this process, which can be
developed for each CBC.
During this process the limitations of the CBC will constrain the final solution for each individual
case. Two main constraints have already been identified: available space above and below
the ground and low ground infiltration capacity in certain areas. SuDS can not only be effective
solving surface runoff but also attenuating surface flows, while at the same time improving
water quality and possibly the environment. Throughout the design when selecting the best
solution this will be taken into consideration as well as maintenance aspects of each SuDS.
Well-designed SuDS are rarely used for a single function. For that, it is noted that SuDS can
be designed with different functions: water conservation and re-use (collection and re-use of
surface water), infiltration (encourage stormwater to soak into the ground),
detention/attenuation (temporary storage of runoff and slow down flow), retention (permanent
storage of runoff), filtration (runoff passes through a filter layer to remove pollutants) and
conveyance of runoff.
During the planning stage, ground permeability rate will be assumed to be negligible.
Therefore, SuDS will be designed to promote detention rather than infiltration to the ground.
This is likely to mean that we ‘over-design’ our SuDS measures by allowing for additional
storage that might actually be required. It is important to remark that some SuDS promote the
filtration through porous layers (filter media or permeable pavements) and, for this reason,

water quality can be improved where possible. Refer to the Drainage Design Basis main
document for further details.
3 SUDS PROPOSALS
3.1 Introduction
This chapter explains a catalogue of SuDS proposals which fit in our Routes. It is noted that
appropriate SuDS techniques must be applied depending on the available space and pollution
source. Where reasonably practicable for additional catchment areas, SuDS elements, such
as bio-swales or tree-pits will be implemented in order to improve the water quality. By running
through porous layers, a level of treatment (and attenuation) will be provided to the flow before
discharging into the existing network.
Additionally, physical constraints will be taken into account, such as the ground’s low
permeability. The following descriptions show a standard solution and, in the next design
steps, each intervention should be defined in detail.
3.2 Filter drains

According to GDSDS (2005) and CIRIA SuDS Manual 2015, filter drains are shallow trenches
filled with stone/gravel that create temporary subsurface storage for the attenuation,
conveyance and filtration of surface water runoff. A perforated pipe should be provided above
the base of the filter drain to collect and convey water to downstream drainage component.
Runoff flows slowly through the granular material, trapping sediments and providing
attenuation.
An example of a filter drain cross section is given in Figure 1 and examples, in Figure 2.
In Ireland, these features have been already used on the National Road Project serving a dual
purpose of groundwater control and runoff drainage.

Figure 1. Proposal type 1: Filter drain schematic. Source: CIRIA SuDS Manual 2015 (chapter 16, figure 16.2)
Figure 2. Examples of filter drains. Source: CIRIA SuDS Manual 2015.
3.3 Bioretention systems

According to GDSDS (2005) and CIRIA SuDS Manual 2015, bioretention systems (including
tree pits and rain gardens) are shallow landscaped depressions that can reduce runoff rates
and volumes and treat pollution through the use of engineered soils and vegetation. There are
many different approaches to the design of bioretention systems and rain gardens; however,
the main components that are usually provided in a bioretention systems are shown in Figure
.

Figure 3. Type 2: Bioretention system. Source: CIRIA SuDS Manual 2015 (chapter 18, figure 18.1)
Figure 4 Example of previously proposed public realm designs for Dublin using SuDS. Source: DCC

Figure 5 Example of previously proposed public realm designs for Dublin using SuDS. Source: DCC
3.4 Permeable pavements

According to GDSDS (2005) and CIRIA SuDS Manual 2015, permeable pavements are
designed to reduce imperviousness, minimizing surface runoff. There is a wide range of types
from porous asphalt and concrete to modular paving (large gaps between impervious areas
allows infiltration). Permeable pavements might be used in parking bays with a parallel
drainage system in place (and providing DCC - Road Maintenance approval) in order to allow
rainwater to infiltrate through the surface and into the underlying structural layer. The water is
temporarily stored beneath the overlying surface before use, infiltration to the ground, or
controlled discharged (Figure 6).
Pervious surfaces, together with their associated substructures, are an efficient mean of
managing surface water runoff close to its source – intercepting runoff, reducing the volume
and frequency of runoff, and providing a treatment medium.

Figure 6. Type 3: Permeable pavement systems types (partial infiltration). Source: CIRIA SuDS Manual 2015
(chapter 20, figure 20.13)
3.5 Opportunity spaces

Opportunity spaces are open spaces clear from utilities and valuable trees. These spaces can
be used as green infrastructure areas and might be located:
- Along the route of the project where the existing catchment remains unchanged.
- In the vicinity of the route and outside the project boundary.
For lengths of the scheme where additional impermeable areas are included but there is no
space available for SuDS and/or attenuation, opportunity spaces upstream of the said areas
might be used to offset the additional flows.

4 BUSCONNECTS SuDS SELECTION

4.1 SuDS Selection Hierarchy
We have applied a hierarchical approach to select SuDS drainage solutions for each of the
BusConnects routes. This drew upon the management train approach in the CIRIA SuDS
Manual Hierarchy (see Section 2) and “Guidance on SuDS Requirements in Fingal County
Council - DS 17-12-19” document.
Our approach to select appropriate SuDS drainage solutions on the BusConnects project
recognises wider scheme constraints, principally land availability, to ensure proposed
measures are proportionate and will not unduly impact on sensitive private lands. We have
followed a 5-stepped approach with Step 1 being the most preferable option and Step 5 being
the least and option of last resort.
The SuDS measures are selected to ensure no net increase in runoff and to maximise the
potential for runoff quality improvements. On this basis, ‘Source’ type measures (see Section
2) are preferred as they provide early interception and the greatest potential to slow runoff
flows, removing sediments and other pollutants. Oversized pipes or attenuation tanks are
used only as the option of last resort where all other measures have been found to be
impractical. Where oversized pipes or attenuation tanks are required they should, where
practicable, being implemented in combination with either Source or Site type attenuation
measures.
Our site selection process is shown in Table 2 below.

Step Question Action
Can a Raingarden, Filter Drain, Swale/Bioretention Yes – stop, preferred approach
1 area, Tree Pit or other Source Control type SuDS
solution be implemented within the redline boundary? No – move to Step 2
Can the redline boundary be extended into low impact Yes – stop, preferred approach,
lands e.g. public green space to accommodate a use in combination with Step 1 if
2 appropriate
Raingarden, Filter Drain, Swale/Bioretention area, Tree
Pit or other Source Control type SuDS solution? No – move to Step 3
Yes – stop, preferred approach,
Can a Site Control measure (e.g. Dry Detention Basin) seek to maximise source control
3 be implemented in addition to Source Control within the measures and minimise size of
redline boundary? Site Control Measures
No - move to step 4
Can the redline boundary be extended into low impact Yes – stop, preferred approach,
lands e.g. public green space to accommodate a Site seek to maximise source control
Control measure (e.g. Dry Detention Basin) measures and minimise size of
4
supplemented, where possible by a Raingarden, Filter Site Control Measures
Drain, Swale/Bioretention area, Tree Pit or other Source
Control type SuDS solution? No - move to step 5

Step Question Action

Yes – note option of last resort
and source/site measures
should be used in addition
Can oversized pipes and/or an attenuation tank be used where possible.
5
to ensure no increase in runoff?
Any extension of the redline
boundary is to be into low
impact lands only
Table 2 – SuDS Selection Hierarchy
4.2 Vegetation species selection

In 2011, Forest Research provided a simple rating of the soil salt tolerance of common species
in the UK. This list is non-exhaustive, and complementary advice should be sought from a tree
specialist as well as the supplying tree nursery.
Figure 7. Tolerance to soil salt of common tree species. Source: Forest Research (2011).

4.3 Examples of application

The proposed SuDS technique must be chosen to achieve both the water quantity and quality
targets. According to “SuDS for Roads” (2009): “Within new developments it is generally
accepted that two levels of SUDS treatment are required for surface water runoff from roads,
although a single level of treatment may be acceptable for smaller residential developments.
Some individual components provide two levels, such as permeable pavements and dry
swales. Where consideration of alternative SUDS is being given, two or more components
linked in series may be required, depending on the type of development on the site.”
The design criteria to allow runoff from the road into the SuDS is preferred to maximize both
quality and space requirements, being also a more cost-effective approach. This criterion
implies that salty water will be collected by the SuDS and; for this reason, the selection of
vegetation species shall be done attending to the salt tolerance.
Therefore, the following SuDS techniques can be applied:
• Bioretention areas located along the routes, updating the existing green stripes. If
runoff of the road is collected, the filter medium must satisfy the conditions below:
1. The permeability should be between 100 and 300 mm/h.
2. 1.00 m depth is compulsory.
It is noted that bioretention areas will contain ground cover plants; and trees are not
required in terms of quality requirements. Trees will be considered only due to
landscape purposes and avoiding in this case collecting runoff from the road.
• Permeable pavements in car parks.
Regarding the location of the SuDS element, some key aspects shall be also taken into
account:
1. Existing trees and streetlights shall be retained. For this reason, spaces clear from
utilities and veteran trees inside the existing green stripes are preferable.
2. If there is not enough available space there where additional impermeable areas are
located, the existing green stripes upstream of the location where additional runoff is
generated shall be used. Thus, it can be guaranteed that the drainage system will have
capacity to convey the resultant flow.
3. In order to optimize the construction, those green stripes which require some updating
(because of implementing the Bus Connects Corridors) shall be prioritized.
Some examples of application are shown in the figures below:

Figure 8. Example of implementation of SuDS elements at the side of roads. Source: CIRIA
SuDS Manual 2015 (chapter 9, figures 9.12 and 9.14).

Figure 9. Example of bioretention area collecting road runoff. Source: Artful Rainwater Design: Creative
Ways to Manage Stormwater (2015).

Appendix B
Bus Connects – Road run-off
collection gullies
Technical Paper
Subject BusConnects - Road run-off collection gullies
To National Transport Authority
From Mott MacDonald/AECOM
Our reference
Date November 2021
1 Overview
This technical note reviews the feasibility and efficiency of using other types of gully gratings/inlets to
accommodate surface water run-off along the new BusConnects Core Bus Corridors, while re-using the
existing drainage infrastructure.
Gullies are the primary collection system where kerbs are present to drain the carriageway and hard surfaces
around the city. The selection of the most suitable type of gully grating is being sought to increase safety on
cycleways and increase the ride quality along bus lanes.
1.1 General
Most routes along the Dublin BusConnects Core Bus Corridors are along National Roads. Therefore, this
document has been prepared with reference to the following NRA Documents and requirements:
 Volume 4 Section 2 Part 3 NRA HD 33/15 Drainage Systems for National Roads
 Volume 4 Section 2 Part 3 NRA HD 102/15 Spacing of Road Gullies
The design procedure used for the determination of the allowable spacing for the road gullies/ kerb inlets is
that as describe in Volume 4 Section 2 Part 3 NRA HD 102/15 Spacing of Road Gullies (referred herein as the
Standard). Four different stormwater collection systems are considered for comparison within this document:
1. Gully Collection System #1: Typical Gully (See Figure 1)

This option considers the use of a standard gully grating and in situ block work gully pot, laid adjacent to the
carriageway kerb, allowing for a total carriageway surcharge flow width of 0.5m from the kerb.
2. Gully Collection System #2: 0.5m Wide Kerb Inlet Gully (See Figure 2)
This option considers the use of a 0.5m wide kerb inlet gully, allowing for a total carriageway surcharge flow
width of 0.5m from the kerb. Depending on site specific conditions (kerb profile), the use of a standard or non-
standard unit will be required.
3. Gully Collection System #3: Proprietary Split Grating and Kerb Gully Unit (See Figure 3)
This option considers the use of a standard split grating and kerb gully unit which would fit the finished kerb
cross section. This option allows for a total carriageway surcharge flow width of 0.5m from the kerb.
4. Gully Collection System #4: Narrow Profile Gully (See Figure 4)

This option considers the use of a narrow profile gully, with standard DCC or TII gully pots and an allowable
surcharge flow width of 0.5m from the kerb.
Mott MacDonald/ AECOM 2
1.1.1 Gully Collection System #1

Figure 1 shows the TII Standard Construction Detail for in-situ concrete and blockwork gullies. Figure 2
shows blockwork gullies connections to the surface water system from the Greater Dublin Regional Code of
Practice for Drainage Works.
Figure 1: Gully Collection System #1: Typical In-Situ and Blockwork Gullies
Figure 2: Typical Blockwork Gullies


Depending on site specific conditions (kerb profile), a standard or non-standard kerb inlet unit would be
appropriate for the collection system. Figure 3 illustrates the location where a standard kerb inlet unit would
be suitable, due to the depth of the kerb between the cycleway and bus lane.
Figure 4 shows a typical section, and plan, of the gully pot and a non-standard kerb gully unit. The non-standard
unit would be required for this system as the proposed geometry of the kerb line between the bus lane and the
cycleway such that a side inlet gully would not fit into the proposed profile.
Figure 3: Site condition allowing for use of standard kerb inlet gully unit
Figure 4: Gully Collection System #2: Non-standard 0.5m Wide Kerb Inlet

The proposed Proprietary grating and kerb gully unit is as shown in Figure 5.
Figure 6 and Figure 7 provide a street view of the typical installation, and the hinged opening respectively, of
this type of unit.
Figure 5: Gully Collection System #3: Proprietary Split Grating and Kerb Gully Unit
The total collection area (grating and side inlet) of this unit is 650cm2.
The maximum spacing of this split grating and kerb collection system was determined from first principles
using the formulas within Sections 5.12, 5.13, 5.14, 5.15, and 5.17 of the Standard.
The maximum spacing has been determined by calculating the specific G Value for the combined unit based
on assumptions of the Ag and P values (it should be noted that relatively large variations in these values have
minimal impact on the overall maximum spacing). The collection efficiency of the side inlet and the gully grating
were calculated independently, and the value of the more efficient component was used as the design
efficiency to determine the maximum spacing.
Figure 6: Typical Installation of Split Grating and Kerb Figure 7: Typical Hinged Opening
Gully Unit of Split Grating and Kerb Gully Unit

The Proteus D400 Narrow Profile Hinged Gully Grating is a proprietary gully unit shown in Figure 8 and Figure
9. With a grating profile of less than 300mm wide, this innovative product design avoids excessive clipping by
traffic and is safer for cyclists who are sometimes put at risk when swerving to avoid typical gully ironwork in
the road.
Figure 8: Gully Collection System #4: Typical Narrow Profile Gully Unit
Figure 9: Typical Narrow Profile Gully Unit

1.2 Rainfall & Maintenance Factor

The design rainfall intensity was calculated using Equation (1) of the Standard using the following criteria:
Criteria Value Justification

Design Storm Return Period 1 Years In accordance with Section 6 of HD 33/15
Critical Storm Duration 5 Minutes In accordance with Section 5 of HD 102/15
2minM5 (rainfall depth occurring in 2 3.14 mm Derived from Flood Studies Report maps
minutes with a return period of 5 years)
Climate Change Allowance 20% In accordance with Dublin City Council Development Plan 2016 - 2022
Based on these criteria, the design rainfall is 52.08mm/hr.
The maintenance factor applied for the various options in considered to be 1.0 (well-maintained urban roads).
1.3 Design Methodology

The design tables within Appendix C of the HD 102/15 were used in combination with Equation (2) to determine
the maximum drainage unit spacings. The calculation assumes that the footpath and cycleway would drain
towards the bus lane, with the collection units located along the kerb between the bus lane and the cycle lane.
The design catchment width will ultimately be determined by the collective drainage design for the footpath,
cycleway, and carriageway. Depending on site specific conditions along the various corridors (e.g. longitudinal
gradient, crossfall etc.) it may be necessary to utilise a dual collection unit with one unit collecting drainage
from the cycleway/footpath and one unit collecting the carriageway drainage.
Therefore, the design catchment width may vary to include the footpath, cycleway, and carriageway in some
areas, and the carriageway only in other areas. As a result, this document considers the required spacing of
the drainage units, for the above-mentioned options, for a catchment width of 10.5m (footpath, cycleway &
carriageway) and 6.5m (carriageway only).
Gully tops shall meet the requirements of EN124 load classifications; the appropriate class of a manhole top
or a gully top to be used depends upon the place of installation. The minimum class recommended for use in
each group is shown in brackets.
— Group 3 (at least class C 250): Pedestrian areas and comparable areas, car parks or car parking decks.
For gully tops, installed in the area of kerbside channels of roads (Figure 10) which, when measured from the
kerb edge, extends a maximum of 0.5 m into the carriageway and a maximum of 0.2 m into the pedestrian
area.
— Group 4 (at least class D 400): Carriageways of roads (including pedestrian streets), hard shoulders (Figure
11) and parking areas, for all types of road vehicles
Figure 10: Typical highway cross- section showing the location of the groups
Figure 11: Typical detail of a hard shoulder showing the location of the groups
2 Comparison of Options
The maximum spacing of gullies, non-standard kerb inlets, split grating and kerb units for the various road
gradients and crossfalls is shown in Table 1. A comparison of the spacings for the carriageway, footpath and
cycleway catchment and the carriageway catchment only, is also shown.
Table 1: Comparison of various collection systems:
Drainage of Footpath, Cycleway & Carriageway 10.5m Catchment

Crossfall (SC) Gradient (SL) System #1: System #2: System #3: System #4:
Typical Gully Non-standard Split Grating and Narrow Gully
Max Spacing (m) Kerb Inlet Kerb Gully Unit Max Spacing (m)
Max Spacing (m) Max Spacing (m)
1/60 1/300 1.19 1.01 1.16 1.19

1/150 1.65 1.28 1.63 1.65
1/100 2.01 1.46 1.97 2.01
1/80 2.19 1.55 2.20 2.29
1/60 2.56 1.65 2.51 2.56
1/50 2.74 1.65 2.74 2.83
1/40 3.02 1.74 3.04 3.11
1/30 3.47 Not Efficient 3.47 3.66
1/20 4.21 Not Efficient 4.16 4.39
1/15 4.75 Not Efficient 4.72 5.03
1/50 1/300 1.55 1.37 1.56 1.55

1/150 2.19 1.74 2.17 2.19
1/100 2.65 1.92 2.63 2.74
1/80 2.93 2.01 2.91 3.02
1/60 3.38 2.19 3.33 3.47
1/50 3.66 2.19 3.62 3.84
1/40 4.11 2.29 4.00 4.21
1/30 4.66 Not Efficient 4.54 4.85
1/20 5.58 Not Efficient 5.41 5.85
1/15 6.31 Not Efficient 6.10 6.77
1/40 1/300 2.29 1.92 2.21 2.29

1/150 3.11 2.47 3.06 3.20
1/100 3.84 2.74 3.69 3.93
1/80 4.21 2.93 4.08 4.39
1/60 4.85 3.11 4.63 5.03
1/50 5.30 3.11 5.01 5.49
1/40 5.85 3.20 5.51 6.13
1/30 6.67 Not Efficient 6.21 6.95
1/20 7.95 Not Efficient 7.28 8.41
1/15 8.96 Not Efficient 8.09 9.60
1/30 1/300 3.57 3.02 3.44 3.66

1/150 5.03 3.84 4.69 5.12
1/100 6.03 4.30 5.58 6.22
Drainage of Footpath, Cycleway & Carriageway 10.5m Catchment

Typical Gully Non-standard Split Grating and Narrow Gully
Max Spacing (m) Kerb Inlet Kerb Gully Unit Max Spacing (m)
Max Spacing (m) Max Spacing (m)
1/80 6.77 4.57 6.12 6.95

1/60 7.68 4.75 6.87 7.95
1/50 8.32 4.94 7.37 8.69
1/40 9.23 Not Efficient 8.00 9.69
1/30 10.42 Not Efficient 8.83 11.06
1/20 12.43 Not Efficient 9.99 13.35
1/15 13.90 Not Efficient 10.73 15.18
1/25 1/300 4.85 4.02 4.50 4.94

1/150 6.67 5.12 6.05 6.95
1/100 8.14 5.76 7.11 8.41
1/80 8.96 6.03 7.73 9.33
1/60 10.24 6.31 8.56 10.70
1/50 11.06 6.40 9.09 11.70
1/40 12.25 Not Efficient 9.73 12.98
1/30 13.81 Not Efficient 10.50 14.81
1/20 16.37 Not Efficient Not Efficient 17.83
1/20 1/300 6.95 5.85 6.14 7.13

1/150 9.60 7.31 8.02 9.87
1/100 11.52 8.23 9.20 12.07
1/80 12.80 8.59 9.83 13.35
1/60 14.54 8.96 10.59 15.27
1/50 15.73 8.96 11.01 16.64
1/15 1/300 10.97 9.14 8.73 11.25

1/150 15.09 11.52 10.64 15.73
1/100 18.10 12.80 Not Efficient 19.02
1/80 19.93 13.35 Not Efficient 21.12
1/60 22.58 13.81 Not Efficient 24.14
Drainage of Carriageway 6.5m Catchment Only

Typical Gully Non-standard Split Grating and Narrow Profile
Max Spacing (m) Kerb Inlet Kerb Gully Unit Gully
Max Spacing (m) Max Spacing (m) Max Spacing (m)
1/60 1/300 1.92 1.62 1.88 1.92
1/150 2.66 2.07 2.63 2.66
1/100 3.25 2.36 3.19 3.25
1/80 3.54 2.51 3.55 3.69
1/60 4.14 2.66 4.06 4.14
1/50 4.43 2.66 4.42 4.58
1/40 4.87 2.81 4.91 5.02
1/30 5.61 Not Efficient 5.60 5.91
1/20 6.79 Not Efficient 6.72 7.09
1/15 7.68 Not Efficient 7.63 8.12
1/50 1/300 2.51 2.22 2.52 2.51

1/150 3.54 2.81 3.50 3.54
1/100 4.28 3.10 4.24 4.43
1/80 4.73 3.25 4.71 4.87
1/60 5.46 3.54 5.37 5.61
1/50 5.91 3.54 5.84 6.20
1/40 6.65 3.69 6.46 6.79
1/30 7.53 Not Efficient 7.34 7.83
1/20 9.01 Not Efficient 8.74 9.45
1/15 10.19 Not Efficient 9.85 10.93
1/40 1/300 3.69 3.10 3.58 3.69

1/150 5.02 3.99 4.95 5.17
1/100 6.20 4.43 5.96 6.35
1/80 6.79 4.73 6.59 7.09
1/60 7.83 5.02 7.48 8.12
1/50 8.57 5.02 8.09 8.86
1/40 9.45 5.17 8.90 9.90
1/30 10.78 Not Efficient 10.03 11.23
1/20 12.85 Not Efficient 11.76 13.59
1/15 14.47 Not Efficient 13.07 15.51
1/30 1/300 5.76 4.87 5.56 5.91

1/150 8.12 6.20 7.58 8.27
1/100 9.75 6.94 9.02 10.04
1/80 10.93 7.39 9.89 11.23
1/60 12.41 7.68 11.10 12.85
1/50 13.44 7.98 11.90 14.03
Drainage of Carriageway 6.5m Catchment Only

Typical Gully Non-standard Split Grating and Narrow Profile
Max Spacing (m) Kerb Inlet Kerb Gully Unit Gully
Max Spacing (m) Max Spacing (m) Max Spacing (m)
1/40 14.92 Not Efficient 12.92 15.66
1/30 16.84 Not Efficient 14.27 17.87
1/20 20.09 Not Efficient 16.14 21.56
1/15 22.45 Not Efficient 17.33 24.52
1/25 1/300 7.83 6.50 7.28 7.98

1/150 10.78 8.27 9.77 11.23
1/100 13.15 9.31 11.48 13.59
1/80 14.47 9.75 12.49 15.07
1/60 16.54 10.19 13.83 17.28
1/50 17.87 10.34 14.68 18.91
1/40 19.79 Not Efficient 15.72 20.97
1/30 22.30 Not Efficient 16.96 23.93
1/20 1/300 11.23 9.45 9.92 11.52

1/150 15.51 11.82 12.96 15.95
1/100 18.61 13.29 14.86 19.50
1/80 20.68 13.88 15.88 21.56
1/60 23.48 14.47 17.11 24.67
1/50 25.40 14.47 17.78 26.88
1/15 1/300 17.72 14.77 14.10 18.17

1/150 24.37 18.61 17.19 25.40
1/100 29.24 20.68 Not Efficient 30.72
1/80 32.20 21.56 Not Efficient 34.12
1/60 36.48 22.30 Not Efficient 38.99
For a typical road crossfall of 2.5% the efficiency of a narrow gully appears to be similar to a typical gully.
3 Conclusion & Recommendations

A review of the allowable spacing of the various gully collection systems shows that in an urban situation a
side inlet kerb is the least efficient. If this option (side inlet kerb) was utilised, the number of gullies required
would increase by a factor of approx. 75%, when compared with the proposed options. This can be seen in
Table 1 which outlines the maximum gully/ kerb inlet spacing for the corresponding road gradients and
crossfalls.
Typical gully units, the split grating and kerb units and narrow profile gullies have similar discharge capacities
across the various gradients and crossfalls, with the narrow profile gullies proving to be slightly more efficient.
The split grating and kerb unit does not meet Dublin City Council drainage maintenance requirements and is
therefore not recommended.
The narrow profile gullies reduce risks associated with gully gratings being laid within the carriageway outside
the wheel running track of buses and will improve ride quality.
Correct construction of the gully pot blockwork and foundation to the appropriate standard, should mitigate
against the risk of settlement of gully pots.
Based on review of the existing drainage system, discussion with local authorities about the following surface
water collection strategy is being proposed to complement the narrow profile gully.
 In the interest of Water Quality all proposed gullies shall contain a sump that will trap debris & prevent
siltation, to enter the drainage networks.
 Where existing gullies are present a narrow profile gully as shown in Appendix A should be retrofitted
wherever practicable.
 Where existing combined gullies are in the carriageway, single units shall be connected using
separation chambers and rodding facility as detailed in Appendix B.
Refer to Table 2 for pros and cons of the use of a typical gully, kerb inlet gully, split grating and kerb gully and
narrow profile gullies.
Table 2: Pros and Cons of Various Gully Units

Typical Gully Unit Kerb Inlet Gully Unit Split Grating and Kerb Gully Unit Narrow Profile Gully Unit
Pros Cons Pros Cons Pros Cons Pros Cons
Widely used Susceptible to Widely used Less efficient This split system Less commonly Gully design, with Less commonly
drainage solution blockage by leaves drainage solution solution reduces the risk of used drainage very high efficiency used drainage
and debris water ponding as solution solution
the kerb inlet
allows the capture
of runoff even if the
grating is blocked
Less expensive Location within the Simple hinged More expensive Easier Slightly more Simple hinged
capital costs carriageway. mechanism to capital cost due to maintenance expensive capital mechanism to
Leading to allow for routine requirements for requirement during costs allow for routine
potential maintenance non-standard units a storm event maintenance
maintenance issue
Maintenance Settlement around Maintenance Susceptible to Simple dual hinged Maintenance
requirements are gullies could lead requirements are blockage by leaves mechanism to requirements are
well understood by to poor ride quality well understood by and debris allow for routine well understood by
operators operators maintenance operators
Higher Settlement around Settlement around Settlement around
maintenance gullies is lesser as gullies is lesser as gullies is lesser as
requirement during the system is the system is the system is
a storm event outside the wheel outside the wheel outside the wheel
track, thus track, thus track, thus
improving ride improving ride improving ride
quality quality quality
A.1 Proposed Drainage Detail

Engineering Designer
Proposed D400 narrow profile

A
captive hinged grating
Footpath / Cycleway
Kerb
Bus Lane Carriageway Pavement

3.0m 3.5m
215mm 21N Concrete Blocks to

IS 20 with Designation 1 Mortar. 1 Proposed D400 narrow profile
No. Coat 10mm Plaster Internally captive hinged grating
Bus Lane/ Carriageway
346 Brickwork - Class A engineering brick
to IS 91 (min 2 courses, max 5)
320 Heavy duty load class

346
D400 cast iron cover
1280mmØ x 160mm deep Manhole

cover slab with 600mm square ope
600
1050mmØ precast concrete chamber
1050mmØ precast 150mm Ø concrete pipe
concrete chamber not less than 1 in 100 fall
215mm 21N Concrete Blocks to
Heavy duty load class IS 20 with Designation 1 Mortar. 1
D400 cast iron cover No. Coat 10mm Plaster Internally
Blockwork to be Bedded with Precast lintel

Connect to existing Designation 1 Mortar
Stormwater/ Sewer Network
In-Situ MX ST4 Concrete with

A393 Mesh Reinforcement 450
In-Situ MX ST4 Concrete with
1050 A393 Mesh Reinforcement
A
1050
1400
Connect to existing
Stormwater/ Sewer Network
100mm thk. concrete

Plan View Section C-C surround to surface water
pipe at saddle connections
Typical Narrow Profile Gully -

Layout & Connection Chamber of Surface Water Run-off to Combined Drainage Network
C:\users\oco30353\appdata\local\projectwise\workdir\mott-gb-pw-03\d0297521\BCIDA-MOT-DNG_RD-0000_XX_00-RP-CD-0001.dwg Nov 26, 2021 - 12:40PM OCO30353
A.2 Data Sheets – Proprietary Unit #4

10/2020 EDITION
2 3
Driving safety up and whole

life costs down
D400 Narrow Profile

Captive Hinged Grating
Excellence in everything we do
D400 Narrow Profile Captive Hinged Grating
Proteus has been deigned to offer an alternative solution in situations where regular replacement
of traditional gratings occurs due to the units being directly in the wheel line, Proteus works by
maintaining water absorbing capability at the kerb face whilst placing the portion of the unit usually
in the wheel line below the road surface thereby making less susceptible to premature failure.
Proteus is manufactured in our UK foundry in Leicestershire to the highest safety, quality and
manufacturing standards.
Safety Water Clearing Efficiency
We have developed a solution in Proteus that offers safe The ability of a grating to effectively remove surface
and predictable grating operation. The grating section water is most important along the kerb line where
is hinged and opens to 110° ensuring the opening 75% of water flows in typical rainfall conditions. Proteus
and closing sequence is safe, simple and predictable, has been designed to provide more than 2x the water
reducing risk of injury. At 300mm wide the grating is clearing area along the kerb line when compared to
designed to effectively remove storm water from the a standard 450 x 450 mm grating.
surface of the road whilst at the same time being out
Proteus has a Type R designation in accordance with
of the wheel track of all vehicles including bicycles.
Appendix A. Table A.2 Determination of grating type
of Highways England Design Manual for Roads and
Bridges CD 526 Spacing of road gullies.
Water Clearing Area cm2
CD534 Section 2 50 mm from kerbface 117.15

paragraphs 2.14.2
& 2.14.3* 90 mm from kerbface 231.14
Kerb line
50
90
450 x 450 mm grating
*Note: DMRB Volume 4 Section 2 Part 5 CD534

Section 2 Gully Tops paragraphs 2.14.2 & 2.14.3
state: Of the total waterway area, there should be
a minimum waterway area of 45 cm2 between the
kerb face of the frame and a parallel line 50 mm
distant, and there should be a minimum waterway
area of 65 cm2 between the kerb face
of the frame and a parallel line
90 mm distant.
2 Saint-Gobain PAM UK — Excellence in everything we do

Durability
Its narrow grating profile avoids excessive clipping by traffic, its patented1
angled bridge is designed to distribute stress and resist displacement
resulting in a solution that offers long term performance while
focusing on the reduction of whole life costs.
Multi-directional wedge seatings provide a large contact area

between the grating and frame sections. This aids stability
and resists lateral movement in the grating reducing
wear, increasing longevity even under
heavy traffic conditions.
1
UK IPO (Intellectual Property Office) Grant Number GB2580253
Tel: +44 (0)1664 814014 www.saint-gobain-pam.co.uk 3

Compatibility
The longevity of any ironwork asset is directly linked to its alignment and compatibility with the structure below.
It is vital that the dimensions of the frame match those of the opening of the chamber in ensuring the frame is
fully supported. Through its unique design Proteus has a large footprint specifically designed to be compatible
with any standard 450Ø gully pot making it an ideal replacement for any existing gully installation.
Watershed 450x450 mm
Performance & compliance Installation Guidance & Recommendations

Proteus is manufactured from highly durable 500/7 It has long been acknowledged that the long term
grade ductile iron, which offers the optimum strength performance of any installation in the carriageway is
to weight ratio. It is designed, manufactured, directly attributed to the interaction and performance
inspected and tested in accordance with the of all key components. Careful consideration should
stringent requirements of the European standard be given to:
BS EN124 2015 Pt 2.
• The design of the casting.
In addition, Proteus is fully compliant with the
• The road type.
relevant requirements of sector specifications
and design guidelines including • The location and chamber type and its material
whether concrete, brick, composite or plastic
• Highways England CD 534 Chamber tops
and gully tops for road drainage and services. • The method of installation and the quality of the
materials used
• Highways England Section 507 Chambers
and Section 508 Gullies & Pipe Connections To ensure optimum performance and durability
of Series 500 Drainage and Service Ducts we recommend installing Proteus using the Rhino
within Volume 1: Specification for Highway Asphalt Solutions Ltd; Ironmaster Installation and
Works Manual of Contract Documents for Reinstatement System.
Highway Works. For further information please visit
• BS7903: 2020 Selection and installation https://www.rhino-uk.com/what-we-do/ironwork-
of manhole tops and gully tops within rebuild-reinstate#proteus
the highway — Guide.
• Highways England CD 526 Spacing

of road gullies.

New Proteus Gully
280 mm from kerb face,
frame avoids wheel track
Grating design retains
minimum waterway
Ironmaster®
area for CD534
surface topping
Ironmaster®
Infill mortar
Ironmaster®
bedding mortar
Base plate size fits a

standard 450 mm support Ironmaster® reinforced
precast concrete shim
Where the Ironmaster system is not chosen we

recommend the following process is adopted
Stage 1 – Preparation
Excavate ironwork
All existing reinstatement materials should be removed

and the supporting structure/chamber cut back until
a sound base is achieved. Trim back the surrounding
surface in accordance with SROH which defines the
trim back area as ‘flange width of the frame +
compactor sole plate width + 50 mm.
The newly-exposed substrate must be clean and

structurally sound prior to commencing the installation.
Stage 2 – Positioning and adjusting the frame

Position the casting frame over the aperture of the gully
pot ensuring it is central to the opening and the frame
wall is supported on all sides. For optimum performance
units are designed to be supported under the entire
flange area, up to the edge of the clear opening. Failure
to provide support over this area will have a detrimental
effect to the long term performance of the unit.

To provide support and ease of adjustment in the early

stages of installation, Proteus has the option of having
the Install Plus Frame Levelling and Installation System
added. To adjust the frame height and to also allow
for changes in gradient, simply place a straight edge
across the excavation and rotate the nylon bolts
clockwise until the desired height is achieved. The
bolts are sacrificial and have a range of movement
between 15 mm and 50 mm.
Stage 4 – Material Selection

For optimum durability the system has been designed
to be used in conjunction with a high performance
bedding material.
Bedding materials should be selected in accordance

with the requirements of paragraphs 24,25 & 26 of
Section 507 Chambers of ‘Series 500 Drainage and
Service Ducts Volume 1 Specification for Highway
Works Manual of Contract Documents for Highway
Works’ and exhibit the following properties:
Stage 3 – Bedding the frame
• Is cementitious and contains recycled materials.
The depth of bedding materials needed to install
the frame and cover level to the road surface is • Have a minimum workable life of 15 minutes.
determined, taking into account the depth of the frame.
• The compressive strength of the material shall
It is recommended that a minimum depth
exceed 30N/mm2 in 3 hours.
of mortar below the flange is no less than 15 mm. Install
Plus provides a spacer below the frame • The tensile strength of the material shall exceed
which is set to the minimum depth of 15 mm. 5N/mm2 in 3 hours.

Stage 5 – Completing the installation Stage 6 – Backfilling
Voids below the flange must be completely filled with
the excavation
bedding material to ensure full support of the frame. Bedding material or rapid
Exposed surfaces of the bedding mortar around the set concrete of the correct
frame are float finished and textured to create a key, specification can be used to
ensuring any voids or loose material are removed and fill the excavation. All bedding
the inside surface pointed to a smooth finish. materials shall be allowed to
cure to a compressive strength
The frame should be enveloped to a minimum thickness
exceeding >30N/mm2 and
of 10 mm, however a minimum of 20 mm is
tensile strength exceeding
recommended as this is viewed as industry best
>5N/mm2 before trafficking.
practice. The top cap of the Install Plus system gives a
visual indication of when 20 mm has been achieved.
Stage 7 – Final reinstatement

Complete the reinstatement in
accordance with client specification. If a
material requiring compaction is used care
must be taken to avoid contact between
any compaction device and the frame
to avoid damage.
The bedding material must also extend beyond the

flange to a minimum distance of 50 mm in accordance
with SROH.
For further information please refer

to product datasheet Ref SGPUK041, available
to download from PAMSearch via our website or
contact our Technical Support Team on 01664 814014

We are proud of our UK
manufacturing heritage
Saint-Gobain PAM UK, at its
Please visit our website: foundry near Melton Mowbray
www.pamline.co.uk
to download electronic versions
in Leicestershire, remains at
or to request hard copies of any the forefront of the design and
of our brochures.
manufacturing of high-performance
Technical Enquiries
Tel: +44 (0)1664 814014 ductile iron access cover and grating
Fax: +44 (0)1664 814025
Email: technical.covers.uk.pam@saint-
solutions for the Infrastructure,
gobain.com Civil Engineering, Water & Utilities Sectors.
Sales Enquiries
We ensure that our products are manufactured to the highest health & safety,
Tel: +44 (0)115 989 8903
Email: pamsales@saint-gobain.com quality and environmental standards. Below are details of our System,
Product and Sustainability accreditation.
Head Office
Lows Lane
Stanton-by-Dale
Ilkeston
Derbyshire SYSTEM, PRODUCT AND SUSTAINABILITY ACCREDITATION
DE7 4QU
Product BS EN124 2015 Pt 2 Access Covers and gratings
Tel: +44 (0)115 930 5000
Fax: +44 (0)115 932 9513 Certification kitemark licence number KM30794
BS 5834 Pt 2 Specification for small surface
boxes kitemark licence number KM07199
BS 5843 Pt 3 Specification for large surface boxes
kitemark licence number KM14164
BS EN ISO 9001 Quality management systems
kitemark licence number FM12908
BS EN ISO 14001 Environmental management systems
kitemark licence number EMS83973
FM12908 ISO 45001 Health & Safety Management Systems
kitemark licence number OHS 570684
CEMARS Certified Emissions Measurement
And Reduction Scheme
EMS83973 Certificate number 2016053J
CEMARS certification demonstrates the
Company’s commitment to measuring,
managing and reducing greenhouse gas
emissions in a robust and credible way.
BES 6001 Responsible sourcing of construction
materials kitemark licence number BES613621
visit: www.pamline.co.uk
The information given in this literature is,
to the best of our knowledge, correct at
the time of going to print. However, Saint-
Gobain PAM UK is constantly looking at
ways of improving its products and
services and therefore reserves the right
to change, without prior notice, any of
the data contained in this publication.
Any orders placed will be subject to our
Standard Conditions of Sale, available
on request.
© 2020Saint-Gobain PAM UK.

CASE D400 Narrow Profile
STUDY Captive Hinged Grating
SAFE, SECURE, VERSATILE
Improving cyclist safety

and reducing whole
life costs through the
adoption of innovation
and best practice.
In collaboration with Wirral Council
and Rhino Asphalt Solutions Ltd
The issues faced
The A41 New Chester Road is a busy route in Birkenhead

where increasing traffic intensity is leading to more
frequent failure of ironwork, higher than budgeted costs
and disruption to road users. In congested areas it is also
common for cyclists to swerve and avoid the surface water
drainage system bringing them into close proximity with
traffic leading to an increased risk of accidents.
Findings
In areas where the road narrows this brings heavy vehicles

into contact with the leading edge of a grating. This
localises the stress transmitted into the ironwork which
leads to a breakdown of the installation material and if left,
the eventual failure of the ironwork and reinstatement.
Excellence in everything we do
The Solution:
PROTEUS D400 NARROW PROFILE

HINGED GULLY GRATING
CASE Initially developed in conjunction with Highways England
STUDY and Rhino Asphalt Solutions Ltd for use in the strategic
road network, Wirral Council recognised the
advantages of Proteus when selecting
it as their preferred solution.
Proteus represents an innovative approach

to product design. Its narrow grating profile
avoids excessive clipping by traffic, its
patented angled bridge is designed to
distribute stress and resist displacement
enhancing its stability, increasing its
durability. At less than 300 mm wide its
grating profile is safer for cyclists who are
sometimes put at risk when swerving to
avoid ironwork in the road.
Proteus can be used in a wide variety of applications such

as roads that have continuous heavy traffic. It has an
independently verified BS EN124 2015 load classification
of D400 to withstand vehicle loads of up to 40 tonnes.
“ Over the years we have experienced a

number of gully failures. We have noticed that
this is largely due to HGV traffic running over
the front edge of each piece of ironwork. With
Rhino’s and Saint-Gobain PAM’s new Proteus
Gully protruding significantly less into the
The Value
carriageway than a standard gully (but also
When combined with the Rhino Asphalt Solutions Ltd collecting the same amount of surface water),
”
Ironmaster Installation System and its compatibility with we are confident in less future failures, and
the existing drainage network, Proteus provides a solution have the reassurance of a 5 year guarantee.
that improves cyclist safety and offers long term
performance reducing whole life costs for Wirral Council. Phil Miner Wirral Council
Proteus is just one of several innovative solutions offered by Saint-Gobain PAM UK.
For further information and advice on Proteus or any other product or service
offered by Saint-Gobain PAM UK please contact our team on
CASE STUDY REF: SGPUK004
0115 989 8903 or visit www.pamline.co.uk
National Transport Authority
Dún Scéine
Harcourt Lane
Dublin 2
D02 WT20

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Preliminary Design Report Appendix K Drainage Design Basis Document

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Appendix K

Final | 26 November 2021

This report takes into account the particular

Job number 268401

Ove Arup & Partners Ireland Ltd

2 Proposed drainage strategy 5

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 | Arup

1.1 Background and Overview of the Project

Figure 1: Optimum Typical CBC Cross-Section

1.2 General principles of drainage design

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 1

• At planning stage the design will be developed on the basis of existing

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 2

Figure 2: Side gullies

1.3 Method of design

The Irish Water models can be used to develop the

A MicroDrainage (WinDes) Model can also be used to

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 3

For very small catchments where hydraulic losses and

As appropriate, each method shall be used to:

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 4

2 Proposed drainage strategy

2.1 Relevant Standards and Guidance

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 5

Table 2 below summarises permeability factors to be used in the design.

Runoff Permeability Factors

Table 3 below summarises soil Standard Percentage Runoff (SPR) values.

SOIL SPR Value

Surface Water Design Criteria in accordance with GDSDS is summarized in Table

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 6

Minimum slope requirement is set up a good practice as 1 in 500 or steeper. Self-

2.2 Storm Water Management

2.3 Sustainable Drainage Systems (SuDS)

2.4 Pipe Materials

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 7

2.5 Distance between manholes

2.6 Clash Checks

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 8

2.7 Bedding Haunching and Surround

Figure 4: Trench bedding

2.8 CBC design criteria

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 9

Table 6: Design Standards

Parameter & Feature Allowable Discharge Rate

Permitted Discharge Rates

Combined New/Existing Existing runoff rates maintained on the basis of:

- 2l/s/ha for the existing grassed areas catchments to be

Attenuation / SuDS Measures

Combined new/existing Attenuation/SuDS measures sized to contain the 1 in 30-year

• The design of attenuation/SuDS measures shall ensure no new flooding of properties.

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 10

BCIDX_ARP-PMG_PS-0000_XX_00-SD-ZZ-0002 | Final | 26 November 2021 Page 11

Project: BusConnects Job No:

Technical Paper SuDS Eligibility For Planning

Subject: Drainage Design Criteria - SuDS Date: 26th Nov 2021

Prepared by: Elena Calcerrada (GBM-TYPSA), Nick Stokes Version: Rev A

Drainage Design Criteria – SuDS Eligibility

1 LOCAL DRAINAGE GUIDANCE AND REFERENCES