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450-550MW COMBINED CYCLE POWER
PLANT AND 8 MIGD SWRO PLANT
MP75/CVL/020
TECHNICAL SPECIFICATION
CCIIVVIILL DDEESSIIGGNN CCRRIITTEERRIIAA
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TABLE OF CONTENTS
1. GENERAL ................................................................................................................... 4
1.1 Introduction ................................................................................................................. 41.2 Terminology and Definitions......................................................................................... 4
2. CODES AND STANDARDS ........................................................................................ 4
2.1 General ....................................................................................................................... 42.2 Local Codes and Standards ......................................................................................... 42.3 International Codes and Standards .............................................................................. 52.4 Other Reference Documents ....................................................................................... 5
3. EARTHWORKS .......................................................................................................... 73.1 General ....................................................................................................................... 73.2 Finished Grading ......................................................................................................... 73.3 Batters......................................................................................................................... 7
4. ROADS, CARPARKS & HARDSTANDS ..................................................................... 8
4.1 General ....................................................................................................................... 84.2 Roads.......................................................................................................................... 84.2.1. Road Classification..................................................................................................... 84.2.2. Carriageway Cross Section ........................................................................................ 84.2.3. Design Criteria ........................................................................................................... 94.2.3.1. Geometric Design....................................................................................................... 94.2.3.2. Pavement Design ....................................................................................................... 94.2.3.3. Road Marking and Signage ...................................................................................... 10
4.3 Carparks.................................................................................................................... 104.3.1. Design Criteria ......................................................................................................... 104.3.1.1. Geometric Design..................................................................................................... 104.3.1.2. Pavement Design ..................................................................................................... 104.3.1.3. Carpark Marking and Signage .................................................................................. 114.4 Hardstands ................................................................................................................ 114.4.1. General .................................................................................................................... 114.4.2. Design Criteria ......................................................................................................... 114.4.2.1. Geometric Design..................................................................................................... 114.4.2.2. Pavement Design ..................................................................................................... 124.4.2.3. Marking and Signage ............................................................................................... 124.5 Road Drainage .......................................................................................................... 124.6 Service Corridors ....................................................................................................... 12
5. PEDESTRIAN ACCESS ............................................................................................ 13
6. STORMWATER MANAGEMENT .............................................................................. 13
6.1 General ..................................................................................................................... 136.2 Drainage Network ...................................................................................................... 136.3 Hydrologic design criteria........................................................................................... 136.3.1. Design Average Recurrence Intervals ....................................................................... 136.3.2. Rainfall Runoff Methods ........................................................................................... 146.3.3. Peak Runoff Flow Rational Method Parameters ..................................................... 146.3.4. NRCS Curve Number Method .................................................................................. 156.3.5. Daily Rainfall Records .............................................................................................. 156.3.6. Rainfall Intensities .................................................................................................... 15
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6.4 Buildings and Condensate Water ............................................................................... 166.5 Hazardous Material Storage Areas ............................................................................ 16
7. DRAINAGE DESIGN ................................................................................................. 16
7.1 General ..................................................................................................................... 167.2 Open Drains .............................................................................................................. 167.3 Culvert and Stormwater Pipes.................................................................................... 177.4 Materials.................................................................................................................... 177.5 Other Drainage Structures ......................................................................................... 177.5.1. Oil Separators .......................................................................................................... 17
8. SEWERAGE SYSTEM .............................................................................................. 17
8.1 General ..................................................................................................................... 178.2 Design Flows ............................................................................................................. 188.3 Sewerage Network .................................................................................................... 188.3.1. Pipes........................................................................................................................ 18
8.3.2. Manholes ................................................................................................................. 198.3.3. Grease Traps ........................................................................................................... 198.3.4. Sewage Effluent Collection Tanks ............................................................................ 198.3.5. Pump Stations .......................................................................................................... 208.3.5.1. General: ................................................................................................................... 208.3.5.2. Emergency Operation:.............................................................................................. 218.4 Sewage Treatment .................................................................................................... 21
9. FENCING .................................................................................................................. 21
TABLES
Table 2-1 Design Guidelines ............................................................................................................. 4
Table 2-2 International Standards ..................................................................................................... 5Table 2-3 Project Design Criteria ....................................................................................................... 5
Table 2-4- Project General Technical Specification .......... ....................... ................................ ............. 5
Table 3-1- Finish Grading .................................................................................................................... 7
Table 3-2- Batter Slope Conditions ...................................................................................................... 7
Table 4-1- Road Types ........................................................................................................................ 8
Table 4-2 Carriageway Cross Section ................................................................................................ 8
Table 8-1 Expected Average Daily Flow (ADF) .......... ............................... ....................... ................ 18
APPENDIX A Daily Rainfall Data Records at Dubai Airport (Electronic attachments)
APPENDIX B Rainfall IDF Table
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1. GENERAL
1.1 Introduction
This document sets out the design criteria to be applied to the Civil infrastructuredesign for the Execution of Project No. D15002 (450-550 MW Combined Cycle PowerPlant and 8 MIGD SWRO Plant at the DUBAL Jebel Ali Site, Dubai, UAE).
The design criteria shall apply in conjunction with other engineering design criteria,design reports, local codes, standards and guidelines, and relevant internationalcodes.
1.2 Terminology and Definitions
The following abbreviations have been used in this document:
AASHTO American Association of State Highway and Transportation OfficialsADCD Abu Dhabi Civil Defence
ADSSC Abu Dhabi Sewerage Services Company
ASTM American Society for Testing and Materials
BS British Standards
BS EN British Standards European Norm
DoT Department of Transport
ARI Average Recurrence Interval
IDF Intensity-Duration-Frequency (curves for rainfall)
2. CODES AND STANDARDS
2.1 General
All Civil infrastructure design, materials, fabrication and construction shall comply withrelevant applicable requirements specified in the various standards, codes, regulations,drawings, guidelines and specifications listed in Section 2.2, and 2.3.
Unless specially noted otherwise, the year of the code and standards in effect at the timethis Criteria is first issued for use shall be the governing date. Where local codes andstandards are insufficient to provide guidance, other international codes and standards maybe utilised. The most stringent criteria shall apply unless otherwise approved.
2.2 Local Codes and StandardsApplicable local codes, standards, regulations and guides that apply include, although arenot limited to, the following:
Table 2-1 Design Guidelines
Resource Title
ADSSC Sewerage System Design Guidelines
DoT Road Geometric Design Manual
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DoT Pavement Design Manual
DoT Road Structures Design Manual
2.3 International Codes and Standards
Applicable international codes, standards and guides that apply include, although are notlimited to, the following:
Table 2-2 International Standards
Standard/DocNo.
Title
BS EN 1992-3 Design of Concrete Structures - Liquid Retaining and Containment
Structures
BS EN 124 Gully tops and manhole tops for vehicular and pedestrian areas.Design requirements, type testing, marking, quality control
BS1377 Methods of test for soils for civil engineering purposes
BS 1722 Fences - Specification for Chain Link Fences
BS 6717 Precast, Unreinforced Concrete Paving Blocks
BS EN 752 Drain and sewer systems outside buildings
BS EN 858-1 Separator Systems for Light Liquids (i.e. Oil, Petrol)
ASTM Standards
British Standards may be substituted with an equivalent ASTM standard if required.
2.4 Other Reference Documents
Other reference documents that apply include, although are not limited to, the following:
Table 2-3 Project Design Criteria
Doc. Number Title
MP75/CVL/019 Design Criteria - ArchitecturalMP75/GEN/001 Design Criteria - Plant Layout and Access
MP75/CVL/015 Design Criteria - Structural
Volume 2A Scope of Work
Table 2-4- Project General Technical Specifi cation
Doc. Number Title
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Volume 2A, Section 10 Technical Specification - Site Data
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3. EARTHWORKS
3.1 General
The design of all earthworks shall give consideration to geotechnical conditions andgeotechnical improvements required for foundations and stability. The design shall alsoconsider the drainage configuration to define grading and finished surface levels.
3.2 Finished Grading
The finished surface grade shall slope away from structures and be directed towards thestorm water drainage system. The minimum grade slopes are shown in Table 3-1.
Finished floor levels shall be a minimum 200mm above the finished grade level.
Table 3-1- Finish Grading
Type Condition
Graded Surface (+) Minimum 0.5%
Desirable 2%
+0.3% grade slope for localised areas only where grading criteria around buildings or other
infrastructure is difficult to meet and there is an overflow drainage path which will not causedisruption to operations or flooding.
3.3 Batters
Earthworks in general shall be designed with the following batter slopes, unless otherwisespecified by the Geotechnical Engineer, or detailed in the Project Geotechnical
Investigation Report.
Table 3-2- Batter Slope Condi tions
Type Condition (*)
Cut (in sandy soil) Temporary works 2.0H: 1.0V desirable
1.3H: 1.0V max
Cut (in sandy soil) Permanent works 2.0H: 1.0V max
Cut (in rock) Temporary works 1.0H: 1.5V max
Fill 2.0H: 1.0V max
(*) Stabilisation of slopes in sandy materials shall be considered.
Stabilisation methods for permanent and temporary slopes shall considerrecommendations outlined in the Project Geotechnical Investigation reports.
Cut batter slopes greater than 3 metres in height, shall be benched as recommended in theProject Geotechnical Investigation Report.
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4. ROADS, CARPARKS & HARDSTANDS
4.1 General
Inplant and access roads shall be designed to include criteria outlined in the followingsections. Local codes, standards and guidelines shall be used.
4.2 Roads
4.2.1. Road Classif icati on
Roads are defined as the following types:
Table 4-1- Road Types
Type Condition
Type 1Onsite Primary Road
Dedicated single carriageway, two-way trafficked lanes Mainaccess roads (subject to higher traffic volume)
Type 2
Onsite Secondary Road
Dedicated single carriageway, two-way trafficked lanes - Accessroads to secondary infrastructure (not subject to high traffic volume)
Type 3
Onsite Access Road
Single carriageway (two way trafficked) access/maintenance roads Access to minor infrastructure or equipment in congested areas
4.2.2. Carriageway Cross Section
The carriageway cross section details are outlined in Table 4.2.
Table 4-2 Carriageway Cross Section
Name Lane Width
(m)
Shoulder+
(m)
Desirable Min. Cross fall(**)(%)
Type 1
(Single carriageway, two waytraffic)
3.75 1.25 2.0
Type 2
(Single carriageway, two waytraffic)
3.0 1.0 2.0
Type 3
Single Lane Access Road(++)
4.0 (min) 1.0 2.0
** Values presented are for sealed roads. For unsealed roads desirable cross fall is 3.0%
+ Where space constraints exist and safety/drainage and access requirements permit, the use of kerbs may be considered
++ Consideration shall be given to minimum requirements for vehicle access for firefighting operations. Refer to applicablelocal design guidelines for details on vehicle sizes and access requirements.
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4.2.3. Design Criteria
4.2.3.1. Geometric Design
Design considerations for on-site roads (Type 1, 2, 3) include:
Design speed 50km/h however a posted speed limit of 30km/h shall apply for all onsite plant roads;
Road intersection shall be designed with minimum turningradius as specified in the DoT Road Geometric DesignGuideline;
Maximum and minimum road longitudinal grades shall complywith applicable requirements from DoT Road Geometric DesignGuideline;
Minimum rigid overhead vertical clearance is 6.0m. Refer toPlant Layout and Access Design Criteria;
Guardrail and guide posts shall meet applicable requirementsfrom DoT Road Side Design Guide. Vehicle protection shall beconsidered where the vertical drop is greater or equal to 1.5mand/or the front batter slope is steeper than 2H:1V. Shoulderwidth may be adjusted at these locations to allow adequatespace for installation of guardrails;
Guarding requirements shall be considered around hazardsdepending on hazard types and risk;
Design vehicles for road geometric design:
o (DoT) P Passenger car;
o (DoT) WB-15; and
o (DoT) SU-9 or Equivalent (Fire access requirements).
In addition, consideration shall be given to maintenance andoperation conditions during the design life of the plant. Geometricalconfiguration of on-site roads at specific locations shall consider anyanticipated use of large vehicles that may be required duringmaintenance works within the process areas.
4.2.3.2. Pavement Design
Pavement design shall be based on DoT Pavement Design manual.Typically the minimum design life for new pavement shall be 20years. Design considerations for on-site roads (Type 1, 2, 3) include:
Roads shall be sealed with asphalt concrete
Design vehicles for pavement design:
o (AASHTO) HS20-44; and
o (AASHTO) Passenger Car (P).
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Pavement design shall consider adequate loading conditions forareas subject to traffic of heavy vehicles associated with
maintenance operations.
4.2.3.3. Road Marking and Signage
Design considerations for on-site roads (Type 1, 2, 3) include:
Road marking and regulatory, directional and warning signagedesign and materials shall comply with DoT Manual for UniformTraffic Control Devices.
Detail design of road marking and signage shall consider expectedoperations and maintenance conditions within Dubal.
4.3 Carparks
4.3.1. Design Criteria
4.3.1.1. Geometric Design
The following functional requirements shall be considered for the designof the parking areas:
Design speed 30km/h;
Carparks shall have a minimum slope of 0.5% (2% desirable)away from structures and directed towards storm waterdrainage;
Wheel stops or kerbing to secure parked vehicles;
Adequate safe pedestrian access;
Design vehicles for geometric design:
o (DoT) P Passenger car;
o (DoT) WB-15.
Parking arrangements for heavy/large vehicles, such as drive-indrive-out, shall be considered for specific locations.
Car parks shall have a minimum dimension of 5.5mx 2.5m inaccordance with DoT Technical Circular;
Provision shall be made where required for a bus set down with
sufficient space to cater for two standard 50 seat buses (longrigid bus 14.5m);
Parking areas for private and visitor vehicles are to be securelyseparated from the plant area.
4.3.1.2. Pavement Design
All designated car parks within the plant area shall be sealed.Pavement design shall be based on DoT Pavement Design manual.Typically the minimum design life for new pavement shall be 20years.
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Design considerations for parking areas include:
The type of sealing for carparks (i.e. asphalt concrete, concretepavement) shall be selected based on the location,configuration, use and expected traffic conditions of eachparticular parking area;
Design vehicles for pavement design:
o (AASHTO) HS20-44; and
o (AASHTO) Passenger Car (P).
Pavement design shall consider adequate loading conditions forareas subject to traffic of heavy vehicles associated withmaintenance operations.
4.3.1.3. Carpark Marking and SignageDesign considerations for carparks include:
Carpark marking and regulatory, directional and warningsignage design and materials shall comply with DoT Manual forUniform Traffic Control Devices.
Details of marking and signage shall consider expected operationsand maintenance conditions.
4.4 Hardstands
4.4.1. General
Hardstands shall be designed for the intended function, subgrade conditions and
anticipated loading. Hardstands would include concrete pavement, pavers, sealedpavement, unsealed pavement, and engineered compacted earth, excludingearthworks. The design requirements shall be in accordance with the relevantstandards and design criteria depending on the nominated material type and use.
4.4.2. Design Criteria
4.4.2.1. Geometric Design
Design considerations include:
Design speed 30km/h;
Hardstands (sealed or unsealed) shall have a minimum slope of0.5% (2% Desirable) away from structures and directed towardsstorm water drainage;
Design vehicles for geometric design:
o (DoT) P Passenger car;
o (DoT) WB-15.
Provision for circulation of a WB-15 semi-trailer and generalmaterial handling equipment shall be provided. Infrequent oroversized equipment shall be a case-by-case design only.
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General geometric configuration of hardstands shall comply withapplicable sections from the DoT Road Geometric Design Guideline.
4.4.2.2. Pavement Design
Pavement design shall be based on DoT Pavement Design manual.Typically the minimum design life for new pavement shall be 20years.
Design considerations for parking areas include:
Sealing for hardstands shall be selected based on the location,configuration, use and expected traffic conditions;
Design vehicles for pavement design:
o (AASHTO) HS20-44; and
o (AASHTO) Passenger Car (P).
Pavement design shall consider adequate loading conditions forareas subject to traffic of heavy vehicles associated withmaintenance operations.
4.4.2.3. Marking and Signage
Design considerations include:
Marking and regulatory, directional and warning signage designand materials shall comply with DoT Manual for Uniform TrafficControl Devices.
Details of marking and signage shall consider expected operations
and maintenance conditions within Dubal.
4.5 Road Drainage
Open drains or kerb shall be provided down each side of the roads. Alternativeconfigurations, such as single cross-fall grading with one-side drains may be considered inareas with space constraints.
Culverts shall be provided at intersections and across access ways into facilities.Floodways may be considered where flow depth will be low; toward the top of thecatchment and minimal impact will occur to operations during a rain event. Wherefloodways are utilised, measure shall be provided to protect pavements and seals fromwater damage, including use of concrete pavements.
4.6 Service CorridorsServices corridors shall be allocated within the road corridor (between facilities) to cater forany services which are required to follow the road, and typically, consideration should begiven to routeing all plant services within these common corridors.
Onsite roads will typically have above or below ground services installed adjacent to theroad drainage. The width of the service corridor may vary and will depend on the type ofservices and the specified offsets to other services.
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5. PEDESTRIAN ACCESS
Pedestrian access shall be incorporated into the design and will be required in at least thefollowing locations:
Defined footpaths between car parks, buildings, equipment and facilities;
Defined footpaths within all office and administration areas.
Sealed footpaths are preferred (i.e. concrete pavers, concrete, asphalt concrete), althoughalternatives such as gravel could be considered as a minimum standard for infrequentlyused paths in remote locations.
Footpaths shall typically have a cross-fall of 2% to prevent ponding of stormwater. Refer toPlant Layout and Access Design Criteria for requirements on minimum widths forpedestrian pathways. Handrails, ramps, steps, barriers and signage shall be designed inaccordance with the defined standards. For frequently used paths consideration shall be
given to providing sun protection.
6. STORMWATER MANAGEMENT
6.1 General
The storm water management system shall be developed to minimise the projectsenvironmental impacts and to provide adequate stormwater flood immunity toinfrastructure.
The drainage configuration shall use gravity fed systems as much as practical and considera combination of evaporation and controlled off-site discharge or controlled off-sitedischarge as possible mechanisms for ultimate water disposal. All water disposals shallcomply with environmental and water quality requirements.
Note that this document generally describes the stormwater design criteria; however thedesign shall match with existing system and environment impact assessment studyrequirements in addition to the described in the below sections.
6.2 Drainage Network
The overall objective of the drainage network is to collect runoff and spills from the variousdrainage areas, and contain, store, treat and dispose of excess runoff water in anenvironmentally acceptable manner while mitigating industrial infrastructure facilities fromflooding. Drainage channels and drains could be either open or covered, depending onrequirements for access and safety.
6.3 Hydrologic design criteria
6.3.1. Design Average Recurrence Intervals
The stormwater management and flood protection facilities will be designedfor flow rates with a given average recurrence interval (ARI). For example, a10 year ARI flow is the flow value that will be equalled or exceeded onaverage once every 10 years. Design ARI values for different structures aregiven in Table 1.
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6.3.2. Rainfall Runoff Methods
Design flow rates shall be computed based on the rainfall data using one ofthe following methods:
Rational Method shall generally be applied to smaller sub-catchments,less than about 80 hectares. The Rational Method can be applied tocatchments up to 240 hectares, as long as the catchment is dividedinto smaller sub-catchments and flows are routed between catchments.
NRCS Curve Number and unit hydrograph methods shall generally beused to compute peak flows and runoff hydrographs for catchmentslarger than 80 hectares, and may be applied to smaller catchments.
Computer programs HEC-HMS (catchment runoff model) or SWMM(urban stormwater management model), or approved equivalent, shallbe used for performing runoff and flow routing calculations for thestormwater drainage network.
Table 1: Design ARI Values
Location &Stormwater Facility
Design Basis Design Flow
The overall stormwater system infrastructure and site grading shall be provided so process and non-process facilities (buildings and equipment) are without damage for a 100 year 24h rainfall event.
General Areas
(1)
Open channels,culverts,
overall stormwatersystem
Minimum grade 0.05% (open drains)
Desirable minimum 0.2%
0.15m freeboard(6)
for Q1.0m3/s
25 year ARI peak flow
Critical Areas(2)
Open channels, pipes,culverts
As above 50 year ARI peak flow
(1) General areas are those areas where f looding could cause inconvenience but would not disrupt production.(2) Critical areas within the plant are those areas where flooding could disrupt operation/production.
6.3.3. Peak Runoff Flow Rational Method Parameters
For peak runoff flow from on-site catchment areas derived using the RationalMethod, the runoff coefficients given in Table 2 shall be used for 10-year ARIrainfall.
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Table 2: Design Run-off Coeffic ients
Areas Run-of f Coeff icient(1)
Asphalt, concrete and roof areas 0.9
Packed earth hardstand areas 0.8
Gravel roads and yard areas 0.5
Landscaped areas 0.3
Undeveloped areas 0.1(1) Runoff coefficients shall be increased on steep slopes to account for increased runoff. Coefficient used shalldepend on the surface finish of the slope. Runoff coefficients for natural catchments shall be determined basedon catchment characteristics.
For ARIs greater than 10 years, the runoff coefficients shall be adjusted by multiplying bythe frequency factor given in Table 3. However, the resulting runoff coefficient should be nomore than 1.0.
Table 3: Frequency Factor
ARI (years)FrequencyFactor, Fy
10 1.0
25 1.1
50 1.2
100 1.25
500 1.3
Time of concentration used in the Rational Method shall be computed using an appropriatemethod based on drainage paths.
6.3.4. NRCS Curve Number Method
The NRCS Curve Number and unit hydrograph methods shall be used tocompute peak flows and runoff hydrographs for catchments larger than 80hectares, and may be applied to smaller catchments.
Rainfall distribution shall be developed using a balanced storm approach,based on the rainfall IDF curves in Appendix B.
6.3.5. Daily Rainfall Records
For purposes of long-term runoff simulations and water balance modelling,the daily rainfall records at Dubai airport have been included in Appendix A,
for the following periods of record:
Dubai Airport: 1968 to 2008
For the project execution phase, complementary rainfall records up to thecurrent date should be obtain for completeness.
6.3.6. Rainfal l Intensit ies
The project design rainfall intensity-duration-frequency (IDF) curves are givenin Appendix B. These rainfall intensities shall be used for design of the on-
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site stormwater management system. Time of concentration shall becomputed using an appropriate method based on drainage paths. The
minimum time of concentration used shall be 10 minutes.
During future design stages, the dates of published rainfall data should bechecked and compared with current rainfall record to see if any significantrainfall events have occurred since development of the rainfall design criteria.
6.4 Buildings and Condensate Water
Stormwater runoff from building roofs and condensate water from AC mounted units shallbe directed into the storm water system with provision of adequate erosion protection atdischarge points and minimise contact with operations personnel. Refer to ArchitecturalDesign Criteria for details on drainage considerations from buildings to the main stormwaterdrainage system.
6.5 Hazardous Material Storage AreasAll chemical and oil storage areas shall comply with any relevant codes and standards.Stormwater collected within these areas shall be inspected prior to release. If no leaks orspills are evident then the area can be drained to the first flush drainage system.
7. DRAINAGE DESIGN
7.1 General
Water management and storage structures shall conform to the requirements of localauthorities and applicable local and international design codes. Water management mayinclude the following structures:
Open drains;
Culverts and Stormwater Pipes;
7.2 Open Drains
The design of open drains shall be carried out following the requirements outlined in theabove sections and any applicable local regulation.
The lining of open drains shall be adopted to adequately meet applicable environmentalrequirements.
Protection against erosion shall be provided. Some methods include but are not limited to:
Appropriate drop structures for local energy dissipation control;
Rock rip rap where appropriately sized rock will provide the necessary erosionprotection;
Rock filled wire baskets (reno mattress or gabions);
Concrete revetment mattress; or
Concrete lined channels.
Energy dissipaters shall be considered where maximum flow velocities cannot be achieved.
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7.3 Culvert and Stormwater Pipes
The minimum stormwater reticulation and road culvert (box or pipe) internaldiameter/dimension is 450mm. Reference shall be made to applicable DoT DesignManuals for requirements on minimum cover for selection of bedding conditions and designloads for culverts and stormwater pipes located under trafficable areas.
Headwalls, energy dissipaters and transition structures shall be designed to achieve thedesired hydraulic performance, comply with applicable local regulations.
7.4 Materials
Materials selected for use in the stormwater infrastructure and process effluent system areto be robust, resistant to corrosion, erosion and chemicals present in the refinery process,traffic loads, and designed for long term performance. The following is a summary of typicalmaterials that may be considered applicable to this project.
Precast concrete pipes, box culverts and manholes. Special protecting measures(i.e. lining) shall be considered in coastal areas to account for aggressiveenvironmental conditions.
uPVC pipes and polyethylene pipes;
Cast-insitu reinforced concrete box culverts and pits;
HDPE pipes;
GRP pipes;
Lined/protected steel pipes;
Lining of drains using shotcrete, reinforced concrete and mortared cobbles;
Geotextiles underlying rip-rap, gabions, matresses, etc.
Refer to project Geotechnical Investigation report for details on ground properties,water table levels and earthworks.
7.5 Other Drainage Structures
7.5.1. Oil Separators
The design of Oil Separators shall take into account local regulations/ FMGlobal requirements and BS EN 858-1 Oil Separator Design.
8. SEWERAGE SYSTEM
8.1 General
The sewerage system may comprise of gravity mains, raising mains, pump stations (ifrequired), and treatment plant. The sewer system shall be sized to receive domestictype sewerage flows from operations and maintenance personnel only. Flows from theconstruction phase shall not be considered.
Wastewater directed to the sewerage system will originate from facilities such astoilets, showers, basins, laundries, kitchens, emergency rooms and lavatories. Otherwaste materials, including process water, wash down water, oils, chemicals, rainfall
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runoff including that collected from building roofs, and condensate water resultant fromAC units shall not be directed to the sewerage system.
Common collection systems with storage tanks could be considered for areas withinfrequent occupancy. Allowance shall be considered for possible effects of disposaland treatment on the main sewerage system from the common collection systems.
The quality of the treated sewerage shall be in compliance with the EnvironmentalDesign Criteria and applicable design codes and local regulations.
8.2 Design Flows
The peak design flow shall be calculated from the expected average flows below:
Table 8-1 Expected Average Daily Flow (ADF)
Location Use of Showers/Laundry NO use of Showers/Laundry
Project Areas 170 litres/person/shift/day 60 litres/person/shift/day
Consideration shall also be given to the design flows used for potable water consumption.
8.3 Sewerage Network
8.3.1. Pipes
Sewer lines shall be sized for a peak flow and minimum gravity pipe flowvelocity of 0.75 m/s at peak flow. For the design flow the ratio of flowdepth to internal pipe diameter (y/D) shall not exceed 0.70. Themaximum mean velocity shall not exceed 2.5m/s at the design flow
depth; A minimum pipe diameter of 150mm for gravity sewer pipelines. 100mm
diameter pipelines may be considered for building connections and minorsewer lines per ADSSC;
A minimum 50mm diameter for pressure pipelines;
The minimum gradient for gravity pipelines shall be:
150mm diameter or less 0.75%
200mm diameter (and greater) 0.30%
Material selection for the sewer pipes (gravity lines and raising mains)shall consider uPVC or HDPE in accordance with applicable Municipality
guidelines. Sewer joints shall be designed to minimise infiltration;
Clearances (Horizontal and Vertical) from other services shall be as perADSSC Design Guideline Section 7 Works Affecting Sewers. Theconfiguration of the sewerage system shall eliminate the possibility ofany sewage or polluted water entering the water supply system;
Minimum cover to sewer lines shall be:
Clearance from other services 0.3 metres
Areas external to roads and non-trafficable areas 1.0 metres
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Roads and hardstand areas 1.2 metres
Where minimum cover cannot be maintained, protection to sewer lineshall be provided. Protection of sewer lines may include concreteencasement, provision of relief concrete slabs, and sleeves. The methodshall be used and the design shall be carried out on a case by casebasis.Where practical additional earthworks (such as bunds) may be providedto achieve minimum cover requirements.
8.3.2. Manholes
The design of manholes shall be in accordance with ADSSC DesignGuideline Section 3 - Sewerage System Design. General designconsiderations include:
Benching in manholes shall be considered to prevent build-up of materialand provide smooth flow between inlet and outlet pipes;
Manholes shall be placed at junctions, change of direction and change ofgrade. Typically manholes shall be spaced up to 60m for diameters150mm or less, 100m for diameters 200mm to 500mm and 120m fordiameters 600m and above;
Manholes design shall include all reasonable features to allow adequatemaintenance and to minimise water infiltration including elevated sealedcovers, sealed joints and liners. The minimum manhole diameter shall be1.2m with a minimum access diameter of 0.6m.
A collection chamber, typically 1.0m diameter, shall be provided at theend of lines for connection to building plumbing installed under the
Uniform Plumbing Code.
8.3.3. Grease Traps
Grease traps shall be installed at the sewerage outlet of all cooking areassuch as kitchens and food preparation facilities and as required by therelevant standards, prior to entry the system to prevent excess greaseentering the system. Refer to Architectural Design Criteria for further details.
8.3.4. Sewage Effluent Collection Tanks
Sewage effluent collection tank sizes shall have a minimum storage capacityof 5 days with at least 25% additional reserve capacity. The collection tanksshall also include the following requirements:
Conform to the requirements of applicable project design criteria, localregulations and standards;
Allow adequate access for vehicle and maintenance operations;
Allow level indication and high water level indicator;
Gas vent pipe;
Sealed joints and access covers.
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8.3.5. Pump Stations
Pump stations shall be designed to optimised pump performance and pumpcycle time.
8.3.5.1. General:
Sewage pump stations shall typically incorporate the following:
Selection of wet type pump well unless local and technicalconditions dictate otherwise. The size of the well shall beappropriate to avoid heat build-up in the pump motor that mayresult from frequent starting as well as the reduction of septicconditions due to excessive detention time;
Two complete commercially available standard sewer pump setsand associated pipework with alternating duty and stand-by andcapable of operating simultaneously. The pumps shall also beable to be installed and removed from the pump well withoutneed to enter the pump well. Cutter impellers (macerator) maybe considered and may allow smaller pumped sewer lines to beconsidered. Adequate ventilation (i.e. vent pipes) shall beprovided for all pump stations;
Non macerator pumps shall be capable of handling sullage of atleast 50mm in size, with pump suction and discharge piping of atleast 100mm diameter. The minimum pipe diameter shall be50mm;
Local control panel, single flood light and junction box to provide
necessary switching of pumps, level alarms and remotesignalling and switching (if required). The pump station shallalso have allowance for future capability to connect to the centralcontrol room for operation and monitoring if necessary;
Necessary pipework to return pumped water to the pump well totest or maintain pumps. Necessary valves and pipework toisolate or drain pressure lines for maintenance or testing;
The finished surface of the pump well shall be above expectedsurface water level to mitigate infiltration into the system.Sewage pumping stations shall remain accessible and flood freeduring a 50 year ARI rainfall event;
Consideration shall be given to servicing and provision of space
around the pump station for maintenance and cleaning;
Safe access shall be provided to wet wells containing equipmentrequiring inspection or maintenance;
All fittings, pumps, pipes, valves, electrical control boxes, coversand accessories shall be non-corrosive and either stainlesssteel, aluminium, galvanised steel or epoxy coated suitable foran aggressive environment.
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8.3.5.2. Emergency Operation :
The sewerage system shall be provided to account for a possibleemergency operation that may result from power supplyinterruptions and pump mechanical failures. The following back-upsystems may be considered as alternatives to mitigate anyenvironmental and operational risks that may result during anemergency operation scenario:
Providion for pump out by vacuum tanker truck;
Socket for operation by emergency power generator; and
Reserve capacity at pump well/ sewer system.
The design and implementation of any of these systems shall be inaccordance with local regulations, other project design criteria, andindustry best practice methods.
8.4 Sewage Treatment
Sewage treatment plant (STP) shall be designed in accordance applicable projectdesign criterias, project specifications, codes, standards and regulations.
The following requirements shall be considered for the design of the STP:
Treated effluent produced by the STP shall meet the quality requirements outlinedin the Environmental Design Criteria;
The system would typically be designed to provide treatment capacity for theaverage expected flow. Peak flows shall be buffered through the STP via abalance storage tank with grit removal if required;
Treatment technology shall be selected based on local regulations, efficiency andperformance requirements. Consideration may be given to non-proprietarymembrane nutrient removal with biological nitrogen and phosphorous removal anddisinfection;
Consideration shall be given to the use of centrifugal or belt press sludgedewatering machines to thicken sludge for disposal in accordance with theEnvironmental Design Criteria;
Treated sewage effluent shall be in accordance with the Environmental DesignCriteria and may be used by project operations or removed off site.
9. FENCINGFencing and gates shall be provided around and within the project infrastructure to ensuresecurity and restrict unauthorised access. The extent and location of the fences and gatesshall be determined in accordance with operational and security requirements.
All fences and gates shall comply with applicable ISPS guidelines, relevant sections ofBS1722 and local guidelines.
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High security fencing includes installation of standard 2700mm high,galvanised PVC coated chain link fence with 3 strand razor wire and concrete
strip footing in accordance with ISPS requirements;
Low/medium security fencing includes installation of standard 2400mm high,galvanised PVC coated chain link fence in accordance with relevant standardsand local guidelines.
All fencing around electrical substations shall be earthed in accordance with Electricaltechnical specifications.
Adequate offset (typically 4m) shall be provided to allow vehicle access formaintenance activities. Offset for pedestrian access is typically 2m.
Drainage pipes, culverts and channels that discharge under or through the securityperimeter fence shall have a security grate fitted. The grating should prevent peopleand/or animals accessing the plant and be easily maintainable and removable toensure satisfactory operation. Consideration shall be given to bypass flow in theevent of blockage at grate to ensure there are no adverse impacts upstream.
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APPENDIX A Dai ly Rainfal l Data Reco rds at Dubai Ai rpor t
Dubai Airport daily rainfall data, 1968 to 2008
Dubai_Airport_Daily_Rainfall_1968-2008.x
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APPENDIX B Rainfall (Intensity Duration- Frequency) IDF Table
Intensity (MM/HR)Duration (hr)
0.25 0.5 1 2 3 4 5 6 7 8
ReturnPeriod(y
r)
2 26.5 23.8 18.5 12.2 9.2 7.4 6.2 5.4 4.7 4.1
5 41 36.9 28.7 19 14.2 11.4 9.6 8.4 7.3 6.4
10 55.5 50 38.9 25.7 19.2 15.4 13 11.3 9.8 8.7
20 73.7 66.3 51.6 34.1 25.5 20.5 17.3 15 13 11.5
50 104 93.6 72.8 48.1 36 28.9 24.4 21.2 18.4 16.3
100 133.6 120.2 93.5 61.8 46.2 37.2 31.4 27.3 23.6 20.9
200 168 151.2 117.6 77.7 58.1 46.7 39.5 34.3 29.7 26.3
500 224.8 202.3 157.4 104 77.7 62.5 52.8 45.9 39.7 35.1
Based on daily rainfall data from 1968 to 2008