ENGINEERING PROCEDURE
STORMWATER DRAINAGE SYSTEMS
NEOM-NEN-PRC-315 Rev 01.00, May 2023
©NEOM [2023]. All rights reserved.
4
Document History
Revision code
Description of changes
Purpose of issue
Date
First Issue
Issued for Implementation
08.05.2023
Rev 01.00
Document Approval
Name
Job Title
Prepared by
Reviewed by
Approved by
Fouad Youssif
All Sector
Dr. Mohamed Haj-Maharsi
Senior Mechanical
Specialist - ETSD
Executive Director, Technical
Consultancy- ETSD
Document Preface
Key Stakeholders:
Proponent, Proponent’s representative, ETSD, NEOM Water,
Mechanical/Infrastructural Engineers of Record, Independent
Mechanical/Infrastructural Engineering Consultant
Added Value:
Outlines the requirements for the stormwater drainage systems design following
NEOM Design Guidelines for wet utilities including runoff calculations: time of
concentration, design return period, runoff quantity.
Furthermore, it tackles the hydraulic design including open channels, gravitational
stormwater pipes, drainage elements, manholes, pipes design velocities, pipe
diameters and gradients in addition to the design criteria for sustainable drainage
systems to mimic natural drainage.
Impact:
Unification of stormwater drainage design systems
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PAGE 2 OF 37
Contents
1
PURPOSE ..................................................................................................................5
2
SCOPE .......................................................................................................................5
3
DEFINITIONS .............................................................................................................5
3.1
Terms......................................................................................................................... 5
3.2
Abbreviations ............................................................................................................. 5
4
REFERENCES ...........................................................................................................6
4.1
NEOM Documents ..................................................................................................... 6
4.2
Other Documents....................................................................................................... 6
5
DESIGN ......................................................................................................................7
5.1
Philosophy ................................................................................................................. 7
5.2
Procedure .................................................................................................................. 8
5.2.1
Description of Project Location .................................................................................. 8
5.2.2
Determination of Used Software, Available Data and Summary of Methodologies ... 8
5.2.3
Site Visit Requirements ............................................................................................. 8
5.2.4
Topography and Survey ............................................................................................ 8
5.2.5
Rainfall Data Analysis ................................................................................................ 8
5.2.6
Hydrological Analysis................................................................................................. 8
5.2.7
Runoff Calculations.................................................................................................... 8
5.2.8
Pavement Drainage ................................................................................................. 15
5.2.9
Hydraulic Design of Storm Drain Systems ............................................................... 20
5.2.10 Design Guidelines.................................................................................................... 23
5.2.11 Sustainable Stormwater Drainage ........................................................................... 31
6
DESIGN REQUIREMENTS ......................................................................................35
6.1
General .................................................................................................................... 35
6.2
Preliminary Design................................................................................................... 35
6.3
Detailed Design ....................................................................................................... 36
6.4
Issue for Construction .............................................................................................. 36
7
APPENDICES ..........................................................................................................37
Appendix A
Stormwater Drainage Systems Checklist
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List of Tables
Table 1: Runoff Coefficients Associated with the Rational Formula (ASCE/EWRI 45-05)...... 9
Table 2: Runoff Adjustment Factors (Riyadh Municipality (2012) Engineering Guidelines for
Flood Protection Criteria for Riyadh City, First Edition, in Arabic)......................................... 10
Table 3: Kerby Equation Retardance Coefficient Values ...................................................... 13
Table 4: Kirpich Formula Correction Factor for Specific Flow Conditions (Rossmiller)......... 14
Table 5: Storm Return Periods ............................................................................................. 15
Table 6: Minimum Design Return Period and Allowable Water Spread ............................... 17
Table 7: Manning’s Roughness Coefficients for Pipes ......................................................... 25
Table 8: Maximum Manhole Spacing .................................................................................... 27
Table 9: SuDS Design Criteria .............................................................................................. 32
Table 10: Table SuDS Selection Matrix for Site Conditions .................................................. 33
List of Figures
Figure 1: Gutter Parameters ................................................................................................. 15
Figure 2: Example of flanking inlets ...................................................................................... 17
Figure 3: Water bypasses the first inlet ................................................................................. 18
Figure 4: Grate inlet with longitudinal bars parallel to the direction of traffic ......................... 19
Figure 5: Bicycle-Safe Grate ................................................................................................. 19
Figure 6: Curb inlets.............................................................................................................. 20
Figure 7: Hydraulic and energy grade lines in pipe flow ....................................................... 22
DOCUMENT CODE: NEOM-NEN-PRC-315
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1
Purpose
The purpose of the Stormwater Drainage Systems Procedure is to provide well defined
steps to accomplish the design of the stormwater drainage systems based on the NEOMNWA-TGD-052 engineering practices, national and international codes and standards and in
compliance with NEOM-NEN-SCH-005.
2
Scope
This NEOM procedure covers the minimum requirements for developing appropriate
drainage design systems for NEOM facilities.
Stormwater runoff shall be properly managed to maintain and enhance existing conditions
and not cause adverse impact on groundwater, surface and coastal environment or
culturally valued spaces. As such, this procedure shall be read in conjunction with NEOM
Flood Risk & Stormwater Drainage (NEOM-NWA-TGD-052).
The Procedure for Hydrological Study (NEOM-NEN-PRC-012) shall also be referred to as a
basis for the assessment of the hydrologic conditions and associated flood risks from water
courses generated from contributing catchments.
3
Definitions
For a comprehensive list of definitions for the terms and abbreviations used at NEOM, see
the List of Definitions and Abbreviations (NEOM-NEN-SCH-006).
3.1
Terms
Term
Definition
none
3.2
Abbreviations
Abbreviation
Definition
ASCE
American Society of Civil Engineers
CN
Curve Number
FHWA
Federal Highway Administration
IDF
Intensity Duration Frequency
SCS
Soil Conservation Service
SuDS
Sustainable Drainage Systems
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4
References
4.1
NEOM Documents
4.2
Document no.
Document title
NEOM-NEN-PRC-005
Stage Deliverables Procedure
NEOM-NEN-PRC-006
Safety in Design Procedure
NEOM-NEN-PRC-008
NEOM Document Numbering and Revision Procedure
NEOM-NEN-PRC-010
Drawing and Drafting Procedure
NEOM-NEN-PRC-012
Procedure for Hydrological Study
NEOM-NEN-PRC-014
Management and Application of NEOM Standard
NEOM-NEN-PRC-020
Asset Naming Conventions Procedure
NEOM-NEN-PRC-021
Stage Review and Approval Procedure
NEOM-NEN-SCH-005
List of Technical Codes & Standards
NEOM-NWA-TGD-052
Flood Risk & Stormwater Drainage
Other Documents
Document no.
Document title
ASCE/EWRI 45-05
Standard Guidelines for the Design of Urban Stormwater Systems,
American Society of Civil Engineers, 2006.
−
CIRIA, Sustainable drainage systems (SuDS) Manual (C753), London,
2016.
−
Federal Highway Administration, Urban Drainage
Hydraulic Engineering Circular No. 22, USA, 1996.
−
Federal Highway Administration, Hydraulic Design of Energy Dissipators
for Culverts and Channels, Hydraulic Engineering Circular No. 14, USA,
2006.
−
Kirpich Z. P., “Time of concentration of small agricultural watersheds”, J.
Civ. Eng. 10(6):362, 1940.
−
Ministry of Communications, Highway Design Manual. Volume 2, Book 1 of
2, section 2.07: Hydrology, Riyadh, Kingdom of Saudi Arabia, 1992.
−
MoMRA. Scope of Work for Stormwater Masterplanning.
−
Riyadh Municipality, Engineering Guidelines for Flood Protection Criteria
for Riyadh City, First Edition, in Arabic, 2012.
−
Natural Resources Conservation Service (NRCS). (1986). Urban Hydrology
for Small Watersheds – Technical Release 55, Washington, D.C.
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Design Manual,
PAGE 6 OF 37
5
Design
5.1
Philosophy
The design of any stormwater drainage system involves the collection of data, familiarity
with the project site and an understanding of the hydrologic and hydraulic principles and
drainage policies associated with that design. The design of stormwater drainage system
should comply with NEOM Flood Risk & Stormwater Drainage procedures (NEOM-NWATGD-052).
The procedure follows the stormwater drainage philosophy mentioned under NEOM-NWATGD-052 Section 6.9. The storm water drainage main philosophy is to minimise the impact
of future construction, this shall be performed through sustainable approach:
•
Sustainable drainage systems (SuDS) that mimics the natural drainage processes
that efficiently and sustainably drain surface water while reducing the quantity of
surface water, minimising pollution and managing the impact on water quality of local
water bodies.
•
Where it is not possible to accommodate drainage using SuDS alone, conventional
solutions shall be introduced such as as gullies, interceptors, drainage collection pipe
networks, sumps and pumping stations.
Road pavement drainage, access roads and others are all areas /systems to be drained
either through Sustainable drainage systems or conventional systems. This procedure
considers urban drainage systems including:
•
Road pavement drainage
•
Roadside median channels
•
Storm drainage pipes
•
Drainage of access roads
•
Drainage of hard standings
•
Drainage of building roofs.
Effective drainage of surfaces is essential to the traffic safety. Water on the pavement can
interrupt traffic, reduce skid resistance, increase potential for hydroplaning, limit visibility due
to splash and spray, and cause difficulty in steering a vehicle when the front wheels
encounter puddles.
Pavement drainage requires consideration of surface drainage, gutter flow, and inlet
capacity. The design of these elements is dependent on storm frequency and the allowable
spread of storm water on the pavement surface.
Roadside channels and storm drainage pipes collect and convey stormwater from the
pavement surface, roadside, and median areas. These drains may dispose their flow to a
storm drain piping system via a drop inlet, to a detention or retention basin or other storage
component, or to an outfall channel.
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5.2
Procedure
5.2.1
Description of Project Location
The designer shall refer to NEOM-NEN-PRC-012 – Section 4.2.
5.2.2
Determination of Used Software, Available Data and Summary of
Methodologies
The designer shall refer to NEOM-NEN-PRC-012 – Section 4.3.
5.2.3
Site Visit Requirements
The designer shall refer to NEOM-NEN-PRC-012 – Section 4.4.
5.2.4
Topography and Survey
The designer shall refer to NEOM-NEN-PRC-012 – Section 4.5.
5.2.5
Rainfall Data Analysis
The designer shall refer to NEOM-NEN-PRC-012 – Section 4.6.
Regarding Impact of Climate Change in section NEOM-NEN-PRC-012 - Section 4.6, this will
be superseded and replaced with updated criteria represented in NEOM-NWA-TGD-052Section 6.3.2 for Temporary and Permanent structures.
5.2.6
Hydrological Analysis
The designer shall refer to NEOM-NEN-PRC-012 – Section 4.7.
5.2.7
Runoff Calculations
5.2.7.1
The Rational Method
The Rational Method is a method widely used for determining the peak discharge for a given
area for urban drainage design. The rational equation is expressed as follows from Eq (9).
Where:
𝑄𝑄 = 𝐹𝐹𝐹𝐹 𝐶𝐶𝐶𝐶𝐶𝐶
Eq. 1
•
Q is the peak flow (m3/s).
•
F is the runoff adjustment factor related to the return period of the event.
•
k is a conversion factor equal to 0.278.
•
C is a dimensionless runoff coefficient.
•
I is the rainfall intensity for a specific time of concentration (Tc) and storm return
period (mm/h), from IDF curves.
•
A is the catchment area contributing to the flow (km2).
The runoff coefficient (C) represents the ratio of runoff to rainfall. It is determined according
to Table 4 for urban areas.
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Where a drainage area is composed of subareas with different runoff coefficients, a
composite coefficient for the total drainage area is calculated using the following equation:
𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝐶𝐶 =
∑(𝐶𝐶 𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 )(𝐴𝐴 𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 )
Eq. 2
𝐴𝐴 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴
The runoff adjustment factor is used to account for the fact that less frequent, higher
intensity storms require adjusted runoff coefficients because infiltration and other losses
have a proportionally smaller effect on runoff. Adjustment factors (F) for storms of different
return periods are listed in Table 1.
Rainfall intensity (I) indicates the rate at which it is falling. Rainfall at a duration equal to the
time of concentration (Tc) is used to calculate the peak flow in the Rational Method. It is
selected from the IDF (intensity-duration-frequency) curves. These can be obtained as
described in the Procedure for Hydrological Study.
Table 1: Runoff Coefficients Associated with the Rational Formula (ASCE/EWRI 45-05)
Type of Drainage
Area
Runoff Coefficient, C*
Business
Downtown areas
0.70–0.95
Neighborhood areas
0.50–0.70
Residential
Single-family areas
0.30–0.50
Multi-units, detached
0.40–0.60
Multi-units, attached
0.60–0.75
Suburban
0.25–0.40
Apartment dwelling areas
0.50–0.70
Industrial
Light areas
0.50–0.80
Heavy areas
0.60–0.90
Parks, cemeteries
0.10–0.25
Playgrounds
0.20–0.40
Railroad yard areas
0.20–0.40
Unimproved areas
0.10–0.30
Lawns
Sandy soil, flat, 2%
0.05–0.10
Sandy soil, average, 2 - 7%
0.10–0.15
Sandy soil, steep, 7%
0.15–0.20
Heavy soil, flat, 2%
0.13–0.17
Heavy soil, average, 2 - 7%
0.18–0.22
Heavy soil, steep, 7%
0.25–0.35
Streets
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Type of Drainage
Area
Runoff Coefficient, C*
Asphaltic
0.70–0.95
Concrete
0.80–0.95
Brick
0.70–0.85
Drives and walks
0.75–0.85
Roofs
0.75–0.95
* Higher values are usually appropriate for steeply sloped areas and longer return periods because
infiltration and other losses have a proportionally smaller effect on runoff in these cases.
Table 2: Runoff Adjustment Factors (Riyadh Municipality (2012) Engineering Guidelines for Flood
Protection Criteria for Riyadh City, First Edition, in Arabic)
5.2.7.2
Return Period
Runoff Adjustment Factor
10 years or less
1.0
25 years
1.1
50 years
1.2
100 years
1.25
The SCS Unit Hydrograph Method
The United States National Resources Conservation Service (SCS) hydrograph method is
usually used to estimate flows from medium to large size catchment areas. This method
takes into consideration catchment characteristics such as the soil type, cover type, surface
treatment, hydrological condition and antecedent runoff condition. These are reflected by a
Curve Number (CN). This number typically ranges from 25 (for low runoff depressions) to 98
(for paved impervious areas).
The data and maps provided by the Saudi Geological Survey (SGS) shall be used to
determine the surface runoff coefficient, to be verified through field visits. Values of the
surface runoff coefficient shall be calculated based on the soil types and land uses within
each basin. The peak discharge values shall then be calculated using the average surface
runoff coefficient for each drainage basin and the rainfall intensity.
For information regarding hydrological analysis, the designer shall refer to NEOM-NENPRC-012.
5.2.7.3
Time of Concentration and Travel Time
The time of concentration (Tc) is defined as the time needed for a drop of water to travel
from the hydraulically most distant point in the watershed to the point of reference
downstream. Tc is computed by summing all the travel times for consecutive components of
the drainage conveyance system.
Its value depends on the nature of the surface and the length of the possible pathways to
reach the end of the basin. The flow path shall be separated into several reaches if there are
breaks in the slopes and changes in the topography.
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When applicable, the Kerby-Kirpich method (Roussel et al. 2005) can be used for estimating
Tc. The National Resources Conservation Service (1986) method is also commonly used
and acceptable. Both of these methods estimate Tc as the sum of travel times for discrete
flow regimes. One good practice is to run both methods concurrently and compare results.
Natural Resources Conservation Service (NRCS) Method for Estimating Tc
The NRCS method for estimating Tc is applicable for small watersheds, in which the
majority of flow is overland flow such that timing of the peak flow is not significantly affected
by the contribution flow routed through underground storm drain systems.
Water moves through a watershed as:
•
Sheet flow tsh
•
Shallow concentrated flow tsc
•
Open channel flow tch.
Time of concentration (Tc) is the sum of t values for the various consecutive flow segments
can be obtained from Eq (1).
Tc = tsh + tsc + tch
Eq. 3
Sheet flow
Sheet flow is flow over plane surfaces. It usually occurs in the headwater of streams. With
sheet flow, the friction value (Manning’s n) is an effective roughness coefficient that includes
the effect of raindrop impact; drag over the plane surface; obstacles such as litter, crop
ridges, and rocks; and erosion and transportation of sediment. Sheet flow have very shallow
flow depths of about 3cm (0.1 foot). For sheet flow of lengths less than 30m (100 feet), use
Manning’s kinematic solution to compute tsh from Eq (2). If a low slope condition or a
transitional slope condition exists, the designer should consider using an adjusted slope in
calculating the time of concentration.
Where:
𝑡𝑡𝑠𝑠ℎ =
( )0.8
0.007 𝑛𝑛𝑛𝑛
(𝑃𝑃2 )0.5 𝑠𝑠0.4
•
tsh = sheet flow travel time (hr)
•
n = Manning’s roughness coefficient
•
L = sheet flow length (ft) (100 ft. maximum)
•
P2 = 2-year, 24-hour rainfall (in)
•
s = sheet flow slope (land slope, ft/ft)
Eq. 4
Shallow concentrated flow
After a maximum length of 30m (100 feet), sheet flow usually becomes shallow
concentrated flow. Shallow concentrated flow travel time is computed from Eq. (3).
Where:
DOCUMENT CODE: NEOM-NEN-PRC-315
𝑡𝑡𝑠𝑠𝑠𝑠 =
𝐿𝐿
3600𝐾𝐾𝑆𝑆 0.5
Eq. 5
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•
tsc = shallow concentrated flow time (hr)
•
L = shallow concentrated flow length (ft)
•
K = 16.13 for unpaved surface, 20.32 for paved surface
•
s = shallow concentrated flow slope (ft/ft)
Channel Flow
Channels flows are assumed to begin where surveyed cross section information has been
obtained, where channels are visible on aerial photographs. Manning’s equation or water
surface profile information can be used to estimate average flow velocity, refer to Eq (4).
Manning’s equation is:
Where:
1
𝑉𝑉 =
𝑛𝑛
𝑅𝑅2⁄3 𝑆𝑆 1⁄2
Eq. 6
•
V = average velocity (m/s)
•
R = hydraulic radius (m) and is equal to A/P
•
A = cross sectional flow area (m2)
•
P = wetted perimeter (m)
•
s = slope of the hydraulic grade line (channel slope, m/m)
•
n = Manning’s roughness coefficient.
After average velocity is computed, tch for the channel segment can be estimated using the
travel time from Eq. (5).
Travel time (Tt) is the ratio of flow length to flow velocity:
Where:
𝑇𝑇𝑡𝑡 =
•
Tt = travel time (s)
•
L = flow length (m)
•
V = average velocity (m/s)
𝐿𝐿
𝑉𝑉
Eq. 7
Kerby-Kirpich Method
Kerby-Kirpich approach requires comparatively few input parameters, and considered as a
straightforward to apply, and produces readily interpretable results. The Kerby-Kirpich
approach produces time of concentration estimates consistent with watershed time values
independently derived from real-world storms and runoff hydrographs.
The total time of concentration is obtained by using adding the overland flow time (Kerby)
and the channel flow time (Kirpich), refer to Eq. (6).
𝑡𝑡𝑐𝑐 = 𝑡𝑡𝑜𝑜𝑜𝑜 + 𝑡𝑡𝑐𝑐ℎ
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Eq. 8
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Where:
•
tov = overland flow time
•
tch = channel flow time
•
The minimum value of tc shall not be less than 10min.
The Kerby-Kirpich method for estimating tc is applicable to watersheds ranging from 0.25
square miles (0.65 km2) to 150 square miles (388.5 km2), main channel lengths between 1
and 50 miles (80km), and main channel slopes between 0.002 and 0.02 (ft/ft) (Roussel et al.
2005).
The Kerby Method
For small watersheds where overland flow is an important component of overall travel time,
the Kerby method can be used. The Kerby equation is:
Where:
Eq. 9
𝑡𝑡𝑜𝑜𝑜𝑜 = 1.44 (𝐿𝐿. 𝑛𝑛)0.467 𝑆𝑆 −0.235
•
tov = overland flow time of concentration, in minutes
•
L = the overland-flow length, in meters
•
n = a dimensionless retardance coefficient
•
S = the dimensionless slope of terrain conveying the overland flow
In the development of the Kerby equation, the length of overland flow was as much as 1,200
feet (366 meters). Hence, this length is considered as the upper limit. The dimensionless
retardance coefficient used is similar in concept to the well-known Manning’s roughness
coefficient.
Table 3: Kerby Equation Retardance Coefficient Values
Dimensionless retardance
coefficient (N)
Generalized terrain description
Pavement
0.02
Smooth, bare, packed soil
0.10
Poor grass, cultivated row crops, or moderately rough
packed surfaces
0.20
Pasture, average grass
0.40
Deciduous forest
0.60
Dense grass, coniferous forest, or deciduous forest with
deep litter
0.80
The Kirpich Method
For channel-flow component of runoff, the Kirpich equation can be be obtained from Eq (8)
𝐿𝐿0.77
𝑡𝑡𝑐𝑐ℎ = 0.0195 𝑥𝑥 0.385
𝑆𝑆
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Eq. 10
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Where:
•
tch = the time of concentration, in minutes
•
L = the channel flow length, in meters
•
S = the dimensionless main-channel slope
The equation is valid for natural basins with well-defined channels, overland flow on bare
earth and mowed grass roadside channels. For other flow conditions, the result of the
equation must be multiplied by a correction factor as listed in Table 4. If a low slope
condition or a transitional slope condition exists, the designer should consider using an
adjusted slope in calculating the time of concentration.
Table 4: Kirpich Formula Correction Factor for Specific Flow Conditions (Rossmiller)
Flow Conditions
5.2.7.4
Correction Factor
Overland flow on grassed surface
2.0
Overland flow on concrete or asphalt surface
0.4
Flow in concrete channels
0.2
Runoff Quantities
For drainage areas up to 100 hectares (1 km2), the runoff shall be calculated using the
Rational Method. For larger drainage areas, the SCS Unit Hydrograph Method shall be
used.
5.2.7.5
Storm Return Period
The frequency of the storm event represents the number of occurrences of an event within a
specified period. The selection of return period is an economic question rather than a
meteorological decision. When selecting design return periods, it is important to consider the
potential damage that would result from a flood that exceeds the design event, especially in
urban areas. To do this, the designer shall consider the following:
1.
Potential for loss of life
2.
Effect of potential flooding of important installations
3.
Potential for isolation of hospitals and restriction of access for emergency vehicles.
The final design storm return period shall balance the risk of sociological and environmental
impacts against economic and physical constraints.
The design shall satisfy two different levels of protection. The first shall cause minimal
disturbance to the public and overland flow and this shall be achieved via the storm return
period. The second shall prevent significant structural flooding or potential loss of life or
major erosion and scouring and this shall be achieved via the flood check.
For information regarding classification of infrastructure flood risk vulnerability and flood
zones, the designer shall refer to NEOM-NWA-TGD-052.
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Table 5: Storm Return Periods
5.2.8
Drainage Elements
Design Storm Return Period
Pavement drainage, surface drainage (curbs, gutters, inlets,
gullies)
refer to Table 6
Minor stormwater network (pipes, swales, ditches, minor
open channels)
refer to Section 5.2.10.3
Major drains conveying and discharge (culverts and major
open channels)
refer to Section 5.2.10.3
Ponds (retention and detention ponds)
refer to Section 5.2.10.15
Pavement Drainage
Pavement drainage occurs in two different modes. One mode involves sheet flow across the
pavement surface, which is predominantly affected by pavement type, condition, cross slope
and texture. The other mode occurs where curbs contain and channelise runoff within the
roadway gutter and a portion of the pavement until the stormwater can be removed from the
surface, usually through inlets.
Conventional gutters begin at the intersection of the pavement surface and the inside base
of the curb and usually extend from the curb toward the roadway centreline at a width of 0.3
m to 1.8 m. They are usually constructed with cement concrete or asphaltic concrete but are
not necessarily the same material as the pavement. If the gutter cross slope varies from the
pavement cross slope, it is called a composite gutter. The gutter may also have the same
cross slope as the pavement as shown in Figure 1.
Figure 1: Gutter Parameters
The curb and gutter form a triangular channel that can be an efficient hydraulic conveyance
facility, often conveying low rainfall intensity events without interruption to traffic. However,
when the design storm flow occurs, the width of runoff may spread to include not only the
gutter width but also any parking lanes or shoulders and certain portions of the travelled
surface. This spread or ponded width is what the hydraulics designer is most concerned
about in curb and gutter flow.
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The main target of storm water management is to restrict the spread of flow of rainwater on
ground surface to a limit that will not obstruct or pose any hazard to vehicular traffic by
collecting and disposing of the runoff water. This should be accommodated through the
design of a storm water drainage network that collects the drainage water and drains it to a
proper drainage facility outside of the road.
The next sub-sections (Inlet Location and Sizing and Inlet Types) are guides on how to drain
water from roads, especially in low areas, so that no stagnation occurs for prolonged
periods.
5.2.8.1
Inlet Location and Sizing
Inlets are important features of curb-and-gutter-type pavement drainage that enable
stormwater to be removed from the roadway area.
1.
Inlets must be properly located and sized for the curb and gutter drainage to be
efficient.
2.
The minimum longitudinal fall at the bottom of the drainage curb face shall be 0.5%.
3.
Designers shall check the profile of the inner face of drainage curbs in areas of superelevation application where combinations of profile grade slopes and super-elevation
application can result in flat or nearly flat profiles.
The following information is necessary for the process of locating inlets:
1.
Plan and profile of the roadway
2.
Topographic maps of the adjacent area
3.
Allowable water spread
4.
Typical roadway cross section
5.
Superelevation information.
There are several locations where inlets may be necessary with little regard to contributing
drainage area. These locations shall be marked on the plans prior to any computations
regarding discharge, water spread, inlet capacity, or flow bypass. Examples of such
locations are:
1.
Sag point in the gutter grade
2.
Immediately upstream of median breaks and entrance/exit ramp gores
3.
Immediately upgrade of bridges (to prevent pavement drainage from flowing onto dge
decks)
4.
Immediately downstream of bridges (to intercept bridge deck drainage)
5.
Immediately upgrade of cross slope reversals (e.g. where the gradient of the road is
reversed in horizontal curves due to super elevation)
6.
Immediately upgrade from pedestrian crosswalks
7.
At the end of channels in cut sections
8.
Behind curbs, shoulders or sidewalks to drain low areas.
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In locations where significant roadway ponding may occur (e.g., underpasses, sag vertical
curves), a recommended practice is to place flanking inlets on each side of the inlet at the
low point in the sag. This is illustrated in Figure 2. The purpose of the flanking inlets is to act
as relief for the inlet at the low point in case it becomes clogged or if the design spread is
exceeded.
Figure 2: Example of flanking inlets
The limits of allowable water spread shall be set after considering the following: volume and
speed of the traffic; number of traffic lanes; absence or presence of gutters, shoulders
and/or parking lanes; extent of the roadway area that can be allocated for water spread
according to a certain design stormwater return period; and safety and travel convenience.
Generally, a water spread of 1.8 meter (≈ half a driving lane) is acceptable. Where a paved
shoulder exists and the traffic allowable speed is less than 70 km/hour, the spread can
equal the shoulder width + 1m. Suggested minimum design return periods and allowable
water spread are presented in Table 6.
Table 6: Minimum Design Return Period and Allowable Water Spread
Roadway
Classification
Criterion
Minimum Design
Return Period
Allowable Water
Spread
Hi-volume or divided
or bi-directional
< 70 km/hr
10 years
Shoulder + 1m
> 70 km/hr
10 years
Shoulder
Collector
< 70 km/hr
10 years
1/2 driving lane
> 70 km/hr
10 years
Shoulder
Low Average Daily
Traffic
5 years
1/2 driving lane
High Average Daily
Traffic
10 years
1/2 driving lane
Local streets
Source: FHWA, “Urban Drainage Design Manual”, Hydraulic Engineering Circular 22
The maximum spacing between inlets shall not exceed 100 m. The procedure for spacing
inlets can be summarised as follows:
1.
Calculate flow and spread in the gutter starting from the upstream side of the
catchment.
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2.
Place tributary area, which is from high point to location of the first inlet, where spread
approaches the spread limit.
3.
Calculate the amount of water intercepted by the inlet, check the inlet efficiency. The
efficiency shall be a minimum of 75%.
4.
Include the water that bypasses the first inlet in the flow and spread calculation for the
next inlet (refer to Figure 3).
5.
Place the next inlet where spread approaches the spread limit.
6.
Repeat this procedure to the end of system.
Figure 3: Water bypasses the first inlet
5.2.8.2
Inlet Types
Several types of inlets are available for intercepting the water flow along the curb and gutter,
such as grate inlets, curb-opening inlets, slotted drain inlets, and combination inlets.
Factors influencing inlet type selection include: hydraulic efficiency, pedestrian and bicycle
safety, debris handling characteristics, structural strength, and installation costs.
Grate inlets consist of an opening in the gutter or ditch covered by a grate. They are
commonly used inlet structures that are available in a wide variety of shapes and sizes.
They can be placed in the gutter on a continuous grade or at sag locations. Grate inlets, as
a class, perform satisfactorily over a wide range of gutter grades but they generally lose
capacity with increase in grade, but to a lesser degree than curb opening inlets.
In a sag location, the capacity of a grate inlet is dependent mainly on the open area of the
grate and the depth of allowable ponded water above the grate. At ponding depths that
completely submerge the grate, the concept of orifice flow is usually applied to the design of
sag location grates. Because grates at sag locations are particularly prone to clogging, it is
common practice to apply a safety factor (typically 50%) to the required inlet area.
Generally, if used in curb and gutter, it is recommended that they are supplemented with a
curb opening to provide a combination sag inlet.
Designers shall provide assumptions regarding the nature of clogging to compute the
capacity of a partially clogged grate. If the area of a grate is covered by debris so that the
debris-covered portion does not contribute to interception, the effective perimeter should be
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reduced accordingly. Generally, regular maintenance is essential for keeping the inlets free
of foreign material.
Important factors influencing the interception capacity of an on-grade grate inlet are: length
and width of grate, shape and size of bars in grate, gutter geometry, depth and velocity of
approaching flow, and orientation of bars (vertical and horizontal).
Grates-on-grade with longitudinal bars parallel to the direction of traffic (Figure 4) are
generally more efficient than those with transverse bars. However, in areas where bicycle
traffic is anticipated, parallel bars require special provisions such as narrowing the space
between bars or adding transverse bars to ensure the safety of bicyclists (Figure 5). These
provisions tend to reduce hydraulic efficiency. Grates with transverse bars are bicycle safe;
however, when used on steep slopes, they can be very inefficient because of the tendency
for the water to splash over the grate without entering the system. Transverse bar grates
and parallel grates with transverse bars are more susceptible to clogging with debris than
grates with longitudinal bars only.
Figure 4: Grate inlet with longitudinal bars parallel to the direction of traffic
Figure 5: Bicycle-Safe Grate
Inlets with the primary opening in the face of the curb are referred to as curb-opening inlets.
They offer little interference to traffic and are relatively free from clogging by debris. Curb
openings can be placed on a continuous grade or at sag locations. They are most effective
on flatter slopes, in sags, and with flows which typically carry significant amounts of floating
debris. The interception capacity of curb-opening inlets decreases as the gutter grade
steepens. Consequently, the use of curb-opening inlets is recommended in sags and on
grades less than 3%. Of course, they are bicycle safe as well.
The most hydraulically efficient type of curb-opening inlet has a cantilevered top slab and a
depression of the gutter flowline at the inlet of at least 50 mm (See Figure 6). Curb inlets
without this depression are significantly less hydraulically efficient. For safety precautions,
the vertical rise of the opening shall be limited to prevent children from entering the inlet.
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Figure 6: Curb inlets
The required length of a curb-opening is a function of the amount of water to be intercepted,
the depth of flow, the depression height and, for an on-grade curb, the allowable carryover.
Curb-opening inlets are usually more adaptable for use at sag points than grate inlets
because of their larger, more hydraulically efficient opening and their reduced tendency to
clog. The interception capacity of curb inlets on continuous grades and particularly on
steeper slopes can be increased by increasing gutter cross slope, increasing the gutter
depression and/or by lengthening the inlet.
Slotted drain inlets have been used successfully for many years to solve various drainage
problems. They have been used to intercept sheet flow, gutter flow with or without curbs,
modify existing drainage systems to accommodate roadway widening or increased runoff
and reduce ponding at flush grate inlets. Slotted drain inlets are susceptible to clogging from
sediments and debris and are not recommended for use in environments where significant
sedimentor debris loads may be present.
The following inlet dimensions are generally acceptable:
5.2.9
1.
0.6 m x 0.6 m for grate inlet clear opening (WxL)
2.
1 m for a curb inlet opening (L).
Hydraulic Design of Storm Drain Systems
Storm drains are primarily designed for the collection of rain generated over roads, car
parks, service roads, open spaces, landscaped areas and from overland flow. Generally, the
storm drain receives surface water through inlets and conveys the water through conduits to
an outfall. The storm drain utilises pipe, box, or other enclosed conduits to convey the
surface water and includes inlet structures (excluding the actual inlet opening), manholes,
laterals (or branches), main lines (or trunks), and miscellaneous structures.
5.2.9.1
Flow Type Assumptions
Two approaches may be used to size an enclosed conduit when steady uniform flow is
assumed. One is termed “open-channel” flow and the other is “pressure” or “surcharged”
flow.
1.
Open-channel flow design requires the conduit to be sized so that the surface of the
design flow in the conduit is open to atmospheric pressure.
2.
Pressure flow design requires the flow in the conduit to be at a pressure greater than
atmospheric, i.e. there is no flow surface within the conduit exposed to atmospheric
pressure.
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Open-channel flow design
Open-channel flow design is recommended because it provides a reserve capacity, which
can be considered a safety factor. A safety factor is needed because the methods of runoff
estimation are not exact and, once placed, storm drains are difficult and expensive to
replace.
Using open-channel flow, design efficiency can be realized by sizing the conduit to operate
as near to “full flow” as possible. For circular pipes, maximum capacity is achieved at a flow
depth equal to around 94% of the diameter of the pipe. However, it is advisable to design
pipes at a flow depth not exceeding 75% of the pipe diameter and keep the remaining spare
capacity as a freeboard to accommodate the following: Future increase in runoff volume due
to increase in impervious areas because of urban expansion and/or other developments,
and possible reduction in pipe capacity due to sedimentation and/or aging.
Pressure flow design
If the pressure flow approach is approved by concerned authorities for cost saving or other
constraints, the pipes will be sized using the same procedure discussed above. In addition,
all head loss coefficients in pipes and junctions shall be estimated. Then, a hydraulic grade
line is computed to account for the effect of the outfall tailwater, friction, and junction losses
on the system during a particular storm event. The grade line aids the designer in
determining the acceptability of the proposed system by establishing the elevations along
the system to which the water will rise. If any allowable highwater elevation is exceeded,
then adjustments to the trial design must be made to reduce the highwater elevation to an
acceptable level.
5.2.9.2
Hydraulic Capacity
The hydraulic capacity of a storm drain is controlled by its size, shape, slope, and friction
resistance. Several flow friction formulas have been advanced which define the relationship
between flow capacity and these parameters. The most widely used formula for gravity flow
in storm drains is Manning’s Equation.
The Manning equation is used for computing flow for open channel analysis where uniform
flow exists or can be reasonably assumed. This can be expressed as follows:
Where:
𝑄𝑄 =
1
𝑛𝑛
𝑅𝑅2⁄3 𝑆𝑆 1⁄2 𝐴𝐴
Eq. 11
•
Q = the discharge in m3/s
•
R = hydraulic radius (m) and is equal to A/P
•
A = cross sectional flow area (m2)
•
P = wetted perimeter (m)
•
s = slope of the hydraulic grade line (channel slope, m/m)
•
n = Manning’s roughness coefficient.
The Manning’s roughness coefficients related to pipes are given in Table 7.
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Another widely used equation for gravity and pressure flow in storm drains is the ColebrookWhite equation, used mainly in computer programs because of the complexity of the
equation that renders manual calculations difficult.
5.2.9.3
Energy Grade Line/Hydraulic Grade Line
The Energy Grade Line (EGL) is an imaginary line that represents the total energy along a
channel or conduit carrying water. Total energy includes elevation (potential) head, velocity
head and pressure head. The calculation of the EGL for the full length of the system is
critical to the evaluation of a storm drain. To develop the EGL, it is necessary to calculate all
losses through the system. The energy equation states that the energy head at any cross
section must equal that in any other downstream section plus losses. The losses are
typically classified as either friction losses or local losses. Knowledge of the location of the
EGL is critical to understanding and estimating the location of the hydraulic grade line
(HGL).
The hydraulic grade line (HGL) is a line coinciding with the level of flowing water at any point
along an open channel. In closed conduits flowing under pressure, the hydraulic grade line
is the level to which water would rise in a vertical tube at any point along the pipe. The
hydraulic grade line is used to aid the designer in determining the acceptability of a
proposed storm drainage system by establishing the elevation to which water will rise when
the system is operating under design conditions.
HGL, a measure of flow energy, is determined by subtracting the velocity head (V2/2g) from
the EGL. Figure 7 illustrates the energy and hydraulic grade lines for open channel and
pressure flow in pipes.
When water is flowing through the pipe and there is a space of air between the top of the
water and the inside of the pipe, the flow is considered as open channel flow and the HGL is
at the water surface. When the pipe is flowing full under pressure flow, the HGL will be
above the crown of the pipe. When the flow in the pipe just reaches the point where the pipe
is flowing full, this condition lies in between open channel flow and pressure flow. At this
condition the pipe is under gravity full flow and the flow is influenced by the resistance of the
total pipe circumference. Under gravity full flow, the HGL coincides with the crown of the
pipe.
Figure 7: Hydraulic and energy grade lines in pipe flow
Inlet surcharging and possible access hole lid displacement can occur if the hydraulic grade
line rises above the ground surface. A design based on open channel conditions must be
carefully planned as well, including evaluation of the potential for excessive and inadvertent
flooding created when a storm event larger than the design storm pressurises the system.
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As hydraulic calculations are performed, frequent verification of the existence of the desired
flow condition shall be made. Storm drainage systems can often alternate between pressure
and open channel flow conditions from one section to another.
5.2.9.4
Energy Losses
For information regarding energy losses, refer to the standard guidelines for the design of
urban stormwater systems developed by ASCE/EWRI 45-05.
5.2.9.5
Computer Hydraulic Analysis
Computer hydraulic analysis and simulation of the network shall be carried out to enable the
selection and recommendation of the most feasible alternative. This will allow the
optimisation of the pipe sizes and the relevant flow velocities regarding the various available
alternatives for the stormwater collection network.
Commercial software for the hydraulic design, analysis and simulation of a gravity network
shall be used. StormCAD, SewerGEMS and Infoworks CS are mainly used for the design
and analysis of gravity and pressure flows through pipe networks and pump stations.
5.2.10
Design Guidelines
The designer shall study the minimum requirements to manage stormwater quantity and
quality from proposed urban developments and target to maintain pre-development
discharge rates, volumes, velocities to comply with NEOM Flood Risk & Stormwater
Drainage procedures (NEOM-NWA-TGD-052).
Provision of hard infrastructure solutions is discouraged, on the other hand, natural methods
that encourage infiltrations should be prioritized. Where it is not possible to accommodate
drainage using SuDS alone, conventional solutions shall be introduced, these may be
permitted subject to approval from the Regulatory Approval Body.
This section focuses on design guidelines using conventional solutions.
5.2.10.1 General Procedure
The general procedure for the design of a typical storm drain is given in brief below:
1.
Define catchments and sub-areas and show the natural drainage flow directions.
2.
Locate suitable outlets to the sub-areas.
3.
Calculate rainfall runoff from each sub-area.
4.
Calculate the flow widths along roads and streets (proposed as well as existing).
5.
If flow widths are unacceptable, provide gully inlets and underground drainage to
reduce the widths.
6.
Provide gully inlet locations and drainage lines with particular attention to the need of
drainage sags and road intersections.
7.
Calculate preliminary pipe sizes.
8.
Place the pipes in the drainage line, with cover and grading requirements met and
junctions and access chambers at appropriate locations.
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9.
Compare alternative lines for cost and efficiency as different layouts provide different
advantages.
10.
Optimise the design so that all design parameters are met and the following are
considered:
a.
Conflict with existing utilities is avoided.
b.
Deep trenching is minimised.
c.
The design is cost effective.
d.
The selected outfall level is sufficiently low to allow for gravity flow.
e.
The number of outfalls is restricted where pollution control is required.
5.2.10.2 Storm Networks Considerations
The stormwater system for any plot shall utilise the open spaces and landscaped areas to
contain the stormwater runoff generated over building roofs and impervious surfaces, as
feasible. The road edge will normally be demarcated by upstand curbs with adjacent
sidewalks sloping towards the curb line especially in urban and semi-urban areas.
Consequently, most rainfall falling within the right-of-way will end up at the road edge
adjacent to the curb line. In addition, surface water reaching the road from external sources
such as roof drainage from adjacent properties can be intercepted by the installation of
drainage inlets at regular intervals which are linked to a pipe network discharging to a
convenient natural water course or open channel drainage system.
5.2.10.3 Drainage Concept
A major/minor system approach shall be considered for the planning and design of urban
stormwater systems.
1.
A minor system is intended to collect and convey runoff from frequent storm events
such that nuisance flooding is minimised. Street drainage systems are to be designed
for a 10-year storm event. The minor system consists of ditches, pipes and other
conduits, open channels, pumps, water quality control facilities, etc.
2.
The major system is intended to safely convey runoff that is in excess of the capacity
of the minor drainage system and thereby manage the risk of inundation to adjacent
land or buildings. This usually occurs during more infrequent storm events, such as
the 25-, 50-, and 100-year storms. The major system typically consists of a network of
overland flow paths including roads, natural channels and streams, engineered
waterways, culverts, community retention/detention basins, and other facilities that
are provided for the runoff to flow to natural or manmade receiving channels. The
designer shall determine (at least in a general sense) the flow pathways and related
depths and velocities of the major system under less frequent or check storm
conditions (typically a 100-year event with a 10% allowance for the impact of climate
change to be used as the main reference). Designer to refer also to NEOM Flood Risk
& Stormwater Drainage procedures (NEOM-NWA-TGD-052) for Climate Changes
Allowances.
The development of a conceptual storm drainage plan shall consist of the following
preliminary activities:
1.
Identify spacing between inlets
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2.
Locate main outfall
3.
Locate storm mains and other conveyance elements
4.
Define detention strategy and storage locations
5.
Define elements of major drainage system
5.2.10.4 Design Velocities
1.
Minimum flow velocity shall be self-cleansing and prevent solids sedimentation, not
less than 0.6 m/s.
2.
Maximum flow velocity in pipes shall be non-eroding, not more than 4.0 m/s.
3.
Maximum velocities in fully lined channels shall preferably be not more than 4.5 m/s
for grouted riprap and 6 m/s for reinforced concrete.
5.2.10.5 Pipe Diameters and Gradient
1.
For concrete pipes aligned adjacent to the curb or hardshoulder, minimum pipe
diameter shall be 400 mm in the collection network (mainlines and laterals). The
minimum pipe slope shall not be less than 0.1%.
2.
For PVC-U pipes aligned adjacent to the curb or hardshoulder, minimum pipe
diameter shall be 300 mm and laid at a minimum gradient of 1 in 150.
3.
For inlet pipes and gully connections, minimum pipe diameter shall be 150 mm.
4.
At changes in pipe diameter, the pipes are to be designed soffit to soffit.
5.2.10.6 Pipe Cover
1.
Minimum pipe cover under road pavements shall be 1200 mm (concrete encasement
is required for shallower cover).
2.
Minimum pipe cover under landscape area and deserted areas (not exposed to traffic)
shall be at least 800 mm.
5.2.10.7 Pipe Materials
The pipe materials and their corresponding Manning’s roughness coefficient are provided in
Table 7.
Table 7: Manning’s Roughness Coefficients for Pipes
Pipe Material
Manning’s n*
Concrete
0.012–0.014
Plastic (PVC-U, PE and GRP)
0.010–0.012
* Lower values are usually for well-constructed and maintained (smoother) pipes
5.2.10.8 Box Channels
For pipe diameters larger than 1200 mm, reinforced concrete box channels will be used and
junction boxes or manholes must be provided at every junction and every change in box
size, grade, or direction of flow, noting that the distance between manholes shall not exceed
150 m.
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5.2.10.9 Culverts
Culverts are relatively short conduits typically used for road crossings of small to moderatesized streams. Culverts are generally constructed in reinforced concrete material. Culverts
cause an abrupt change in streamflow characteristics. The acceleration of flow that occurs
causes head losses. Flow within the culvert can range from tranquil to rapid, and the
structure can flow either partially full or under pressure. Hydraulic analysis of culverts
requires consideration of tailwater conditions, friction losses related to the culvert material
and flow character, inlet and outlet losses, and minor losses within the culvert due to bends
or other streamflow perturbations. For more information regarding hydraulics of the flow of
water within culvert, refer to the standard guidelines for the design of urban stormwater
systems developed by ASCE/EWRI 45-05 and the Federal Highway Administration (FHWA)
including Hydraulic Engineering Circular 22.
5.2.10.10 Manholes
The purpose of manholes is to provide access to a storm drain for inspection and
maintenance. They are usually placed at changes in direction, grade and storm drain size
and at conduit intersections and intervals along long stretches of conduit. Manholes shall not
be placed under carriageways to avoid any interruption to the circulation during
maintenance. Conduits passing through manholes shall have good hydraulic properties to
minimise head loss. The surface topography shall also be given consideration when locating
a manhole.
1.
Manholes are usually constructed out of cast-in-place concrete or precast concrete.
2.
Manholes shall have a minimum clear cover opening of 600 mm in diameter and
covers shall be set at final paved level or 300 mm above final ground level in open
areas.
3.
Their chamber rings are usually circular with a minimum diameter of 1200 mm and
their chamber base is usually square.
Manholes shall be designed to withstand both the live and dead load forces that may be
imposed on them. The diameter is often a function of depth with deeper manholes having
larger diameters. The minimum internal diameter of manholes shall be:
1.
1200 mm for pipes with diameters of 600mm or less
2.
1800 mm for pipes with diameters larger than 600mm and for junction manholes
Access to manholes shall be allowed via removable ladders of corrosion resistant material.
For manholes deeper than 3.5 m, the designer shall provide additional facilities such as a
safety cage to ensure safe access to the manhole.
The manhole frame and cover are normally made from cast iron. They must be designed to
have adequate strength to support the expected load. A good fit between cover and frame is
essential, and it is preferable to place the manhole away from traffic. The cover shall be
removable or hinged. The principal defence against a cover being lifted by children is a
cover weight in excess of 45 kg. Covers that can be bolted down are required where there is
possibility of vandalism, pressure system and/or other conditions.
1.
Minimum depth of soil cover for pipes without concrete encasement is 1.20 m.
2.
Minimum depth of soil cover for pipes with concrete encasement is 0.60 m.
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3.
Where a utility crossing a storm water drainage pipe/culvert, the minimum vertical
clearance between two pipes will be ≥0.30 m.
4.
Maximum spacing between manholes will depend on pipe diameter, according to the
classification in Table 9.
Manhole covers shall be capable of bearing a traffic load based on HL-93 AASHTO Truck
Load, refer also to MOMRA specifcations in Urban Areas (MA-100-C-V1/1) covering several
sections for manhole frames and covers and, in particular, section 20.
Manhole covers shall be single sealed or doubled sealed.
•
A single seal cover can be airtight when the groove is filled with grease or other
suitable compounds. It will prevent sewage gases from escaping to the surface,
especially when installed within residential or commercial areas.
•
A double-seal manhole covers has double the arrangement of a single-seal cover.
This creates an airtight and a water-tight seal. This feature is guaranteed to prevent
gas escape, and the seepage of surface water through the cover, thus causing
damage to the underground utilities within the chamber. This is best-suited for internal
sewage manhole covers
Securing covers can be achieved in 2 different methods:
Bolting a sealed manhole cover can increase its sealing efficiency, but the bolting should not
disturb the sealing system. The locking feature achieves two very important goals: it
prevents theft and vandalism. It also secures a tight fit preventing rocking:
1.
Using stainless steel bolts: the manhole cover is directly bolted on the frame using
stainless steel bolts. This method is highly advisable for sealed manhole covers.
Hexagonal and socket head bolts can be used in this method.
2.
Cam lock: in this method, the manhole cover is secured to the frame using a ductile
iron cam mechanism attached to special stainless-steel bolts or hexagonal head
bolts. The cam lock provides improved security to the frame and cover assembly, also
eliminating loose and missing fasteners.
Table 8: Maximum Manhole Spacing
Pipe Diameter
(mm)
Maximum Manhole Spacing
(m)
≤400
50
500–900
100
1000–1200
150
Manholes can be divided according to their depths, i.e shallow manholes and deep
manholes
Shallow manholes: These types of manholes are about two to three feet or 75-90
centimeters of shallow depth. They are normally placed at the starting of a sewer or
drainage water conduit passage and in the areas that are not subjected to heavy traffic.
These types are known as inspection chambers with a light lid.
Deep manholes: Any manholes deeper than 150 centimeters and fitted not subjected to
heavy traffic are considered as deep manholes. These manholes are always incorporated
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with a heavy manhole cover and a built-in ladder to ease the personnel’s entry and exit if
required.
The loads acting on the manholes differ according the project’s conditions. In this respect,
the structural design of the manholes lies under the responsibility of the structural designer.
Designer shall refer to MOMRA standards for Bridges, Tunnels, Culverts, and Pedestrian
Bridges Specifications in Urban Areas (MA-100-C-V1/1) covering several sections for
manhole frames and covers and, in particular, Section 20 for Drainage Systems.
In addition to the use of manholes for inspection and maintenance, rodding eye systems can
be used for special cases, such as hard standings areas close to building and ramps
entering garages and hardscape areas.
Rodding eye systems provide an access opening in a drainage installation for the purposes
of gaining full-bore access to the interior of a drain for internal cleaning, and which remains
permanently accessible after completion of the installation but does not include an
inspection chamber or manhole.
5.2.10.11
Freeboard
Water level shall be allowed to rise in the stormwater drainage networks up to a maximum of
200 mm below the cover level of the manholes.
5.2.10.12
Outfalls
An outfall transfers collected stormwater from a storm drain to an acceptable point of
release in either a natural or constructed facility without adverse effects to roads, the
community, the environment, or any property owner. An outfall may be either an open
channel or a closed conduit but has no prescribed length. Generally, the outfall for the storm
drainage system shall discharge into a natural low, existing storm drainage system, or a
channel.
The design engineer shall determine the tail water for the downstream drain to find the
impact on the proposed outfall. If the outfall of the storm drain system is into a wadi, stream,
major drainage pipe or ponds, the design engineer shall consider the coincidental probability
of the peaks of both systems occurring at the same time. The tail water for the downstream
shall be checked with the peak of the storm drain system.
The designer should consider at least the following aspects of outfalls that may affect the
hydraulic design of the storm drain:
•
The flowline elevation of the proposed storm drain outlet should be equal to or higher
than the flowline of the outfall.
•
The highwater elevation at the outlet of the outfall must be estimated for the normal
operating conditions of the storm drain. In normal design, this elevation is the
elevation at which to begin the hydraulic grade line determination.
•
In situations where the highwater at the outfall outlet is expected to influence
significantly the flow in the outfall, a water surface profile for an open channel outfall
or hydraulic grade line for a closed conduit outfall should be computed, beginning with
the highwater elevation in the outfall outlet. The computation should continue up to
the outlet of the storm drain system. The resulting elevation can then be used as the
tailwater for the hydraulic grade line check in the storm drain system.
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•
There may be instances in which an excessive tailwater causes flow to back up the
storm drain system and out of inlets and access holes, creating unexpected and
perhaps hazardous flooding conditions. The potential for this should be considered.
•
Energy dissipation may be required to protect the outfall and the storm drain outlet.
Also, if the outlet discharge impinges on the opposite bank of the outfall, then
protection to that bank should be provided. Protection is usually required at the outlet
to prevent erosion of the outfall bed and banks. Riprap aprons or energy dissipators
should be provided if high velocities are expected.
•
Where practicable, the outlet of the storm drain should be positioned in the outfall
channel so that it is pointed in a downstream direction. This will reduce turbulence
and the potential for excessive erosion.
•
For assets having security requirements, every outfall structure shall incorporate a
safety grill to prevent unauthorized access into the outfall pipes. The grill shall be
fabricated with stainless steel bars. The size and the maximum spacing of bars shall
be designed in coordination with NEOM Security requirements.
5.2.10.13
Outlet Protection
Any network systems or culverts tend to accelerate flow velocity at outlet. The designer shall
provide stone riprap or other outlet protection that must be designed to handle a range of
velocities. The designer shall extend riprap sufficiently downstream until streamflow lines fill
channel and velocities become nonerosive.
For further information and design procedure, the designer shall refer to FHWA, 2006a,
“Hydraulic Design of Energy Dissipators for Culverts and Channels”, Hydraulic Engineering
Circular 14.
5.2.10.14
Oil Separator
Oil separators before discharge from facilities shall be considered to prevent oils and grease
entering the stormwater drainage system. Use of water quality inlets is best limited to
controlled runoff applications (e.g. maintenance yards, parking lots, certain industrialised
areas) where high concentrations of oils are expected.
1.
Oil and grit separators consist of a series of chambers designed to trap and retain
sediments and hold floatables (e.g. oil, debris).
2.
The oil water separators include coalescing plates, which allow the oils to combine
and collect at the top of the oil water separator.
3.
Oil water separators shall be located on the outlet of a drain from a facility that is
suspected to discharge significant quantities of oil such as vehicle maintenance
areas.
4.
Sizing of the storage chambers is generally based on contributing drainage area and,
therefore, cost and size limit their application to relatively small discharges.
5.
On a periodic basis, these oils are removed from the oil water separator by a disposal
company.
6.
Measures to control sediments and erosion shall be used before discharging into an
inlet (culvert, channel, catch basin, etc.) in cases where surface drainage flows over
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untreated soils. These measures can include riprap or gravel layers, sand/silt
separation basin, vegetation, and soil stabilization.
5.2.10.15
Storage Facilities
Stormwater drainage systems can discharge, after treatment, to natural watercourses (sea,
wadies, streams) subject to environmental agency approval. Two common classifications of
ponds are either Wet or Dry. Both types of ponds provide both stormwater attenuation and
treatment.
1.
Wet ponds, known as retention ponds, continually have a pool of water in them called
dead storage.
2.
Dry ponds, detention ponds, do not have dead storage and dry out between storms.
Detention Ponds
Stormwater detention ponds are used for the temporary storage of runoff to reduce the peak
rate of runoff from a given area. The stormwater runoff is then released at a lower controlled
rate. Because these ponds are normally dry and only contain water for relatively short
periods of time, they can be constructed as part of parking lots, athletic fields, and others.
1.
An emergency overflow shall be provided to convey excessive inflows or clogging of
the main outlet.
2.
Outlet flows shall be controlled by a structure with easy access for maintenance.
3.
The relationship between storage, discharge, and elevation shall be determined.
4.
The volume of the detention pond can be calculated using a storage routing model,
with inflow and outflow varying with time.
5.
Using the storage routing model,the design one-hundred-year ultimate inflow
hydrograph will be analyzed through the basin and outflow structure with appropriate
tail water condition.
6.
The detention volume and outflow structure shall be adjusted, if necessary, until the
allowable one-hundred-year ultimate is not exceeded, and the detention basin fills to
or near the design maximum allowable water surface elevation.
7.
Access shall be provided for maintenance.
8.
The pond bottom shall slope towards the outlet.
9.
Where a rapid raise in water level is expected or the design depth is greater than
1.2m, the facility shall be surrounded by a high fence with warning signs.
10.
It is highly recommended that side slopes to the pond shall be 3:1 (H:V) or flatter.
11.
It is recommended that the minimum length to width ratio for ponds be 1.5:1.
Retention Ponds
Retention ponds are pools designed with additional storage capacity to attenuate surface
runoff during rainfall events for a period of several days or more. They can be used for
recreation, water treatment, and water supply with landscaped banks and surroundings to
provide additional storage capacity during rainfall events. Retention ponds can also be used
for groundwater recharge. The design criteria for retention ponds are the same as those for
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detention ponds but with a zero discharge from the pond. Release is via evaporation and
infiltration only.
1.
Permeable bottom shall be provided for infiltration.
2.
An emergency overflow shall be provided to convey excessive inflows greater than
the one-hundred-year ultimate and for multiple storms over a short period of time.
3.
The pond shall be protected from pollutants so that they do not settle, prevent
infiltration and may contaminate the groundwater.
4.
The volume of the retention pond will be designed to store at a capacity of the 100year event and the 24-hour storm.
5.
Drains shall be provided to ensure emptying of the pond for cleaning purposes and
emergency operations.
5.2.10.16
Design Lifetime for the System Component
The expected service lifetime of a permanent network is 50 years while the expected service
lifetime of a temporary network is 10 years.
5.2.11
Sustainable Stormwater Drainage
Conventional drainage systems are now struggling to cope with rapid urbanisation and
extremes in rainfall due to climate change. As such, a different approach to urban water
management has resulted in the concept of Sustainable Drainage Systems (SuDS) which
mimic natural drainage processes to reduce the effect on the quality and quantity of runoff
from developments and provide amenity and biodiversity benefits.
SuDs are composed of a sequence of management practices and strategies with control
structures that are designed to drain surface water in an efficient and sustainable manner.
The treatment stages in the process of implementing SuDS include:
1.
Prevention – prevent runoff and pollution as close as possible to the source.
2.
Source control – control runoff at or close to its source (green roofs, permeable
pavements, filterstrips, rain gardens, living walls).
3.
Site control – manage water received from source control features (soakaways,
ponds, swales).
4.
Regional control – control and store the clean runoff received from the site (wetlands,
ponds).
5.
Conveyance features – move water between the different treatment stages. This shall
be done via aboveground features to maximise wildlife and people benefits.
There are some key principles that influence the planning, choice of SuDS measure to be
implemented and the choice of the design process, enabling SuDS to mimic natural
drainage by:
1.
Ensuring attenuation by creating storage location and releasing stormwater slowly.
2.
Harvesting rainfall when possible.
3.
Allowing infiltration (where appropriate) to reduce impact on groundwater recharge.
4.
Reducing water velocities on the land surface.
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5.
Filtering out pollutants.
6.
Creating areas where sediments are prone to settle out by controlling the flow of the
water.
The designer will provide flow modelling for the undeveloped condition based on a 10-year
return period. In addition, the designer will provide necessary SuDS for the developed
condition to ensure that the storm water runoff for the 10-year return period remains with
their same values prior to urbanisation.
5.2.11.1 Design Criteria
The design of SuDS will comply with NEOM Flood Risk & Stormwater Drainage procedures
(NEOM-NWA-TGD-052).
Water quantity, quality, amenity and biodiversity design criteria are presented in Table 9.
Table 9: SuDS Design Criteria
Pillar name
Design Criteria
Water Quantity
Runoff shall be harvested for reuse.
Peak runoff discharges shall be controlled for the 1:100 design event.
Discharges to surface water shall be prioritised.
Peak runoff discharges shall be released from ponds to natural watercourses
for the 1:2 year return period.
Natural hydrological systems shall be preserved and protected on the site.
Wadi running through the site shall be recreated as a green corridor for the
management of surface water.
SuDS shall drain sufficiently fast so as not to reduce the management of
runoff from subsequent rainfall.
Surface water shall be retained within the SuDS for events up to the critical
1:25 year event and contained within appropriate exceedance routes and
storage areas up to the critical 1:100 year event.
System shall be flexible to be suitably adapted during design life following
climate change or urban creep.
Water Quality
Critical areas shall have adequate pollution control measures to minimise the
risk of pollution to surface and ground waters.
Amenity
Water shall be used to support vegetation to enhance public space, civic
space and the road environment.
Multi-functionality uses for SuDS shall be maximised.
Side slopes for water features shall be kept accessible and swales and ponds
shall be kept shallow, easily accessible and easy to maintain.
Biodiversity
Natural local habitats shall be protected.
Natural wadis shall be recreated.
Trees shall be planted.
Habitat connectivity shall be enhanced through green corridors.
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5.2.11.2 Recommendations for designing SuDS to respond to common site conditions
Certain site conditions can influence the choice of SuDS suitable for any specific project.
Table 10: Table SuDS Selection Matrix for Site Conditions
Condition
SuD
Groundwater less
than 3 m below
ground surface
Green Roof
Notes
Rainwater Harvesting
Permeable Paving
With liner and underdrain
Filter Strip
Bioretention Area
With liner and underdrain
Swale
With liner
Hardscape Storage
If aboveground
Pond
With liner
Wetland
Impermeable soil
type
Green Roof
Rainwater Harvesting
Permeable Paving
With underdrain
Filter Strip
Bioretention Area
Swale
Hardscape Storage
Pond
Wetland
Underground Storage
Existing
infrastructure
Green Roof
Rainwater Harvesting
Permeable Paving
Relocate to marked corridor
Filter Strip
Bioretention Area
With structural grid in soil
Underground storage
Topography: site
on a flat site (<5%
slope)
Green Roof
Source control
Rainwater Harvesting
Source control
Soakaway
Source control
Permeable Paving
Source control
Filter Strip
Source control
Bioretention Area
With short kerb and rill length
Swale
Provide some gradient
Hardscape Storage
Pond
Try to keep flow above ground
Wetland
Try to keep flow above ground
Underground Storage
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Condition
SuD
Topography: site
on a steep site (515% slope)
Green Roof
Notes
Rainwater Harvesting
Permeable Paving
If terraced
Bioretention Area
If terraced
Swale
If installed along contour
Hardscape Storage
If terraced
Wetland
If terraced
Underground Storage
Topography: site
on a very steep site
(>15% slope)
Green Roof
Limited space
Green Roof
Rainwater Harvesting
Underground Storage
Rainwater Harvesting
Soakaway
Permeable Paving
Bioretention Area
Rill or Channel
Hardscape Storage
Micro-wetland
Underground Storage
High risk
contamination area
Proximity to
protected species
or habitat
Green Roof
Source control
Rainwater Harvesting
Source control
Permeable Paving
With liner and spill isolation
Bioretention Area
With liner and spill isolation
Swale
With liner and spill isolation
Hardscape Storage
With liner and spill isolation
Wetland
Treatment of predicted waste
Underground Storage
With liner and spill isolation
Green Roof
Rainwater Harvesting
Soakaway
Permeable Paving
Filter Strip
Bioretention Area
Swale
Hardscape Storage
Pond
Wetland
Underground Storage
Source: Water, People, Places: A guide for Master Planning sustainable drainage into developments
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For further information on Sustainable Drainage Systems, the designer shall refer to NEOM
Flood Risk & Stormwater Drainage procedures (NEOM-NWA-TGD-052)
6
Design Requirements
6.1
General
6.2
•
Stormwater drainage design shall be done by a qualified stormwater drainage
consultant to be approved by NEOM. Any design by contractors or non-qualified
stormwater consultants shall not be accepted.
•
The designer shall submit all drawings in PDF/CAD with readable scale showing key
plan and legend.
•
All submittals must be complete and self-explanatory and must not be based on a
submittal previously commented and/or rejected by reviewers.
•
Any changes to the approved designs must be approved by the reviewer.
•
List of design deliverables shall comply with the NEOM Plan of Work (PRC-029) and
NEOM Stage Deliverable Procedure (PRC-005).
Preliminary Design
The Preliminary Design Package shall include but is not limited to the following:
•
Preliminary Design Report including but not limited to:
−
An introduction for the project including the objectives and vision
−
Project site location plan showing the existing site boundary
−
Design criteria
−
Catchments/subcatchments area plan contributing or expected to contribute to
the proposed network
−
Hydraulic design calculations and technical calculation sheets that contains
(diameters, levels, slopes, catchment areas, catchments’ time of concentration,
intensities, pipe flows, pipe velocities
−
Sizing design calculations for any proposed structures
•
Hydraulic modelling using the Rational Method (Steady State) for the proposed
network
•
Site survey and site context including
•
−
Topographic survey of the natural terrain to be submitted in CAD digital format
“AutoCad” with (X, Y) coordinates and with an elevation (Z) relative to a
specified datum
−
Proposed finished grading to be submitted in CAD with the same format
indicated above
Drawings of the design elements as applicable and requested including but not limited
to
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6.3
−
Proposed site location plan
−
Proposed site grading plan
−
Layout and part plans of the proposed stormwater network
−
Preliminary profile of the main collector to assure that outfall’s location and level
are appropriate and feasible
−
Utility disposition with typical sections of the right of way (ROW) showing the
details of the service corridor to assure no clash between the stormwater
system and other utilities
Detailed Design
The Detailed Design Package shall include but is not limited to the following:
6.4
•
Detailed Design Report with full and detailed design updated calculations
•
Hydraulic modelling for the proposed network using an unsteady state method to
optimise the network sizes and estimate ponds volume if required
•
Detailed design drawings including the following:
−
List of drawings
−
Proposed site location plan
−
General site layout
−
Proposed site grading plan
−
Detailed layout plans showing all stormwater drainage system
−
Detailed profile drawings
−
Details of design elements such as catchbasins, gutters, manholes, trench and
pipe bedding, outlets, ponds, etc.
•
All applicable standard specifications
•
All particular specifications
•
Bill of Quantities for the system.
Issue for Construction
The Issued for Construction Package shall include but is not limited to the following:
•
IFC drawings including the following:
−
List of drawings
−
Proposed site location plan
−
General site layout
−
Proposed site grading plan
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7
−
Detailed layout plans showing all stormwater drainage system with catchbasins’
locations and corresponding calculations (e.g. with output calculations from
FlowMaster by Bentley)
−
Detailed profile drawings
−
Details of design elements such as catchbasins, gutters, manholes, trench and
pipe bedding, outlets, ponds, etc.
Appendices
Appendix A
Stormwater Drainage Systems Checklist
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Appendix A Stormwater Drainage Systems Checklist
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APPENDIX A
A.1
Stormwater Drainage Systems Checklist
The Designer/Contractor shall implement and ensure compliance with the following checklist:
Contract
Number:
Originator:
Project/
Asset Name:
Date:
Department/Sector
Work Inspection
Request (WIR)
reference number:
1. INTRODUCTION
Check all applicable
Insert your comments here
☐ 1. Include the study goals and
requirements
☐ 2. Include a history of floods in the area
☐ 3. Describe the study area and field visits
☐ 4. Include the collection of the existing
system
☐ 5. Include the collection of identified
floodplains
☐ 6. Include site photos
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APPENDIX A
2. TOPOGRAPHIC SURVEY
Check all applicable
Insert your comments here
☐ 1. Include a site map for the development
area superimposed on the most recent
topographic map
☐ 2. Include a map of the site map for the
development area with existing/natural
contour lines
☐ 3. Include a recent ground topographic
survey with WGS84-UTM system
☐ 4. Include the proposed site grading plan
☐ 5. Include a detailed survey of all the
existing drainage systems in the study area
(networks / pond / open channels), if present
3. HYDROLOGICAL STUDY
Check all applicable
Insert your comments here
☐ 1. Include the proposed land use map for
the study area
☐ 2. Calculate the Runoff Coefficient of
Rational Method based on the proposed land
use map
☐ 3. Calculate the Curve Number based on
the geological map / soil types / land cover
and the proposed land use map
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APPENDIX A
Check all applicable
Insert your comments here
☐ 4. Include the delineation of subcatchments for modelling
☐ 5. Calculate time of concentration
☐ 6. Include a comprehensive morphology
description of the study area
4. METEOROLOGICAL STUDY AND ANALYSIS OF RAIN DATA
Check all applicable
Insert your comments here
☐ 1. Include a map stating the locations of
existing meteorological stations near the study
area
☐ 2. Include a table containing the maximum
daily rainfall data (mm/day), preferably from
the General Authority of Meteorology and
Environment
☐ 3. Include statistical data analysis for rain
data (HYFran-Plus, SMADA, Hydro freq) or
similar
☐ 4. Include the program interface used in
the statistical analysis of rainfall data
☐ 5. Include a table of statistical analysis from
the program derived for the maximum depth
of daily rain for different return periods for 2,
5, 10, 25, 50, and 100 years
☐ 6. Include the creation of IDF Curves for
different return periods in the case of surface
drainage for the design of rainwater and flood
drainage networks.
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APPENDIX A
5. HYDRAULIC CALCULATIONS
Check all applicable
Insert your comments here
☐ 1. Apply the hydraulic design for urban
drainage works using different programs:
StormCad or SewerGems or any other similar
program
☐ 2. Ensure the use of SI units in hydraulic
calculations throughout the report
☐ 3. Prepare the calculations of drainage
pipes and provide the results in tables or
graphs
☐ 4. Define pavement drainage design return
period
☐ 5. Prepare hydraulic calculations for surface
drainage and pavement drainage including
water spread calculations, etc.
☐ 6. Define spacing between inlets
☐ 7. Choose inlet types
☐ 8. Locate main outfall
☐ 9. Align storm mains and other conveyance
elements
☐ 10. Define detention strategy and storage
locations
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APPENDIX A
Check all applicable
Insert your comments here
☐ 11. Identify type flow in storm drains
(Open-channel/pressure)
☐ 12. Choose drain material and Manning’s
coefficient
☐ 13. Design preliminary sizes
☐ 14. Check minimum and maximum
velocities
☐ 15. Check minimum and maximum pipe
diameters
☐ 16. Check minimum and maximum pipe
covers
☐ 17. Check distance between manholes
☐ 18. Check freeboard in manholes
☐ 19. Compare alternative solutions for cost
and efficiency as different layouts provide
different advantages
☐ 20. Optimize the design so that all design
parameters are met, taking into consideration
the following:
a. Conflict with existing utilities is avoided
b. Deep trenching is minimised
c. The design is cost effective
d. The selected outfall level is sufficiently
low to allow for gravity flow
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APPENDIX A
Check all applicable
Insert your comments here
e. The number of outfalls is restricted
where pollution control is required
☐ 21. Check needs for sustainable urban
drainage system
☐ 22. Check needs for oil separator
6. RESULTS
Check all applicable
Insert your comments here
☐ 1. Include a summary of the results of the
hydrological and morphometric studies,
hydraulic modelling, and calculations
7. PRELIMINARY DESIGN
Check all applicable
Insert your comments here
☐ 1. Include Preliminary Design Report with
an introduction to the project showing the
objectives and vision
☐ 2. Include Preliminary Design Report with
project site location plan showing the existing
site boundary
☐ 3. Include Preliminary Design Report with
design criteria
DOCUMENT CODE: NEOM-NEN-PRC-315
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APPENDIX A
Check all applicable
Insert your comments here
☐ 4. Include Preliminary Design Report with
catchments/subcatchments area plan
contributing or expected to contribute to the
proposed network
☐ 5. Include Preliminary Design Report with
hydraulic design calculations and technical
calculation sheets that contains diameters,
levels, slopes, catchment areas, catchments’
time of concentration, intensities, pipe flows,
pipe velocities
☐ 6. Include Preliminary Design Report with
sizing design calculations for any proposed
structures
☐ 7. Include a copy of the hydraulic model
using the Rational Method (Steady State) for
the proposed network
☐ 8. Include site survey and site context
☐ 9. Include topographic survey of the natural
terrain to be submitted in CAD digital format
“AutoCAD” with (X, Y) coordinates and with an
elevation (Z) relative to a specified datum
☐10. Include proposed finished grading to be
submitted in CAD digital format “AutoCAD”
with (X, Y) coordinates and with an elevation
(Z) relative to a specified datum
☐ 11. Include drawings of proposed site
location plan
☐ 12. Include drawings of proposed site
grading plan
☐ 13. Include drawings of layout and part
plans of the proposed stormwater network
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APPENDIX A
Check all applicable
Insert your comments here
☐ 14. Include drawings of preliminary profile
of the main collector to assure that outfall’s
location and level are appropriate and feasible
☐ 15. Include drawings of utility disposition
with typical sections of the right of way (ROW)
8. DETAILED DESIGN
Check all applicable
Insert your comments here
☐ 1. Include detailed design report with full
and detailed design with updated calculations
☐ 2. Include hydraulic modelling for the
proposed network using an Unsteady State
method
☐ 3. Include detailed design drawings showing
drawings list
☐ 4. Include detailed design drawings showing
proposed site location plan
☐ 5. Include detailed design drawings
showing general site layout
☐ 6. Include detailed design drawings showing
proposed site grading plan
☐ 7. Include detailed design drawings showing
detailed layout plans showing all stormwater
drainage system
DOCUMENT CODE: NEOM-NEN-PRC-315
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APPENDIX A
Check all applicable
Insert your comments here
☐ 8. Include detailed design drawings showing
detailed profile drawings
☐ 9. Include detailed design drawings showing
details of design elements such as catchbasins,
gutters, manholes, trench and pipe bedding,
outlets, ponds...etc.
☐ 10. Include all applicable standard
specifications
☐ 11. Include all particular specifications
☐ 12. Include Bill of Quantities for the system
9. ISSUED FOR CONSTRUCTION
Check all applicable
Insert your comments here
☐ 1. Include detailed design drawings showing
drawings list
☐ 2. Include detailed design drawings showing
proposed site location plan
☐ 3. Include detailed design drawings
showing general site layout
☐ 4. Include detailed design drawings showing
proposed site grading plan
DOCUMENT CODE: NEOM-NEN-PRC-315
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APPENDIX A
Check all applicable
Insert your comments here
☐ 5. Include detailed layout plans showing all
stormwater drainage system with catchbasins
locations and corresponding calculations (e.g.
with output calculations from Flowmeter by
Bentely)
☐ 6. Include detailed design drawings showing
detailed profile drawings
☐ 7. Include detailed design drawings showing
details of design elements such as catchbasins,
gutters, manholes, trench and pipe bedding,
outlets, ponds...etc.
10.Site Change Order & As Built drawings
Check all applicable
Insert your comments here
☐ 1. Include updated survey points of the
drainage system invert levels on as-built
drawings.
☐ 2. Include updated BIM Model including
the drainage system invert levels of the asbuilt drawings with reference to NEOM-NENPRC-009 Rev 04.00, September 2022
11.RECOMMENDATIONS
Check all applicable
Insert your comments here
☐ 1. Include recommendations with
objectives and results of the urban drainage
solutions
☐ 2. Include available alternatives to solve the
drainage issues along with the recommended
solutions
Filled by:
DOCUMENT CODE: NEOM-NEN-PRC-315
Submitted to:
REVISION: 01.00
©NEOM [2023]. All rights reserved.
APPENDIX A