WASA Wastewater and Potable Water Design Requirements

Water And Sewerage Authority (WASA)
Of Trinidad and Tobago
Water and Wastewater Design Guideline Manual
Revision 1 – October 2008

Water and Wastewater Design Guideline Manual Table of Contents
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Major elements of revision no 1 – October 2008 :
In section 3.1, a minimum flood level requirement has been added.
In section 5.2.5.3, the minimum duration criteria for fire has been changed to one hour.
In section 5.6.2, the required specification for PVC pipe was changed.
In section 5.7.2, a new polyurethane coating section was added.
In section 6.6; 7.11; 12.16; 14.10, the height of fences have been reviewed to 2.1 m.
In a new section 6.2, requirements for impoundment reservoirs were added
In section 5.1 and 10.1, requirements for trenchless technologies were added
In a new section XX, criteria for As build and drawing standards were added.

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Table of Contents
Table of Contents
List of Abbreviations
Section 1 General Information .......................................................................... 1-1
Section 2 Design Approach & Approvals......................................................... 2-1
2.1 Introduction ...................................................................................................................... 2-1
2.1.1 Multi barrier approach ........................................................................................................ 2-1
2.1.2 Sustainable development .................................................................................................... 2-1
2.2 Design Guidelines............................................................................................................. 2-2
2.3 Review process of the guidelines ..................................................................................... 2-2
2.4 Approvals.......................................................................................................................... 2-2
Section 3 Design Standards................................................................................ 3-1
3.1 Design requirements......................................................................................................... 3-1
3.2 Acts, Codes and Standards ............................................................................................... 3-1
3.3 Other Design & Construction Standards .......................................................................... 3-2
3.4 Industry Standards ............................................................................................................ 3-2
Section 4 Process and Equipment Redundancy............................................... 4-1
4.1 General.............................................................................................................................. 4-1
4.2 Minimum redundancy – Wastewater systems .................................................................. 4-1
4.3 Minimum redundancy – Drinking Water systems............................................................ 4-1
4.4 Standby Power.................................................................................................................. 4-2
4.5 Standardization of Equipment .......................................................................................... 4-2
Section 5 Design of Water Distribution System............................................... 5-2
5.2.1 Design Water Demand........................................................................................................ 5-2
5.2.2 Average Water Demand (light industrial and commercial)............................................... 5-3
5.2.3 Residential Per capita demand............................................................................................ 5-4
5.2.4 Equivalent Population......................................................................................................... 5-5
5.2.5 Fire Flow Requirements...................................................................................................... 5-5
5.3.1 Pipe Design Flow................................................................................................................ 5-6
5.3.2 Hazen Williams roughness coefficient............................................................................... 5-6
5.3.3 Standard Pipe Sizes............................................................................................................. 5-7
5.3.4 Minimum Pipe Sizes........................................................................................................... 5-7
5.3.5 Pressure ............................................................................................................................... 5-7
5.4.1 Velocity ............................................................................................................................... 5-7
5.4.2 Pipe redundancy.................................................................................................................. 5-7
5.4.3 Pumping capacity................................................................................................................ 5-8
5.5.1 Grid System......................................................................................................................... 5-8
5.5.2 Location............................................................................................................................... 5-8
5.5.3 Separation from Stormwater and Wastewater Mains......................................................... 5-8
5.5.4 Pipe Depth........................................................................................................................... 5-9
5.5.5 Valves.................................................................................................................................. 5-9
5.5.6 Hydrants .............................................................................................................................. 5-9

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5.5.7 Blow Off............................................................................................................................ 5-10
5.6.1 Pipe Material ..................................................................................................................... 5-10
5.6.2 Pipe specification.............................................................................................................. 5-10
5.6.3 Structural Requirements.................................................................................................... 5-11
5.6.4 Tracer Wire ....................................................................................................................... 5-12
5.6.5 Water Service Connections............................................................................................... 5-12
5.7.1 Polyethylene Encasement ................................................................................................. 5-13
5.7.2 Polyurethane coating......................................................................................................... 5-13
5.7.3 Cathodic Protection........................................................................................................... 5-13
Section 6 Drinking Water Reservoirs ............................................................... 6-1
6.1 General.............................................................................................................................. 6-1
6.2 Impoundment design ........................................................................................................ 6-1
6.3 Reservoir (tank) Design.................................................................................................... 6-1
6.4 Reservoir Capacity............................................................................................................ 6-2
6.5 Re-chlorination System Requirements ............................................................................. 6-2
6.6 Emergency Eye-wash ....................................................................................................... 6-2
6.7 Site Access Road and Security ......................................................................................... 6-2
6.8 Architectural ..................................................................................................................... 6-3
6.9 Structural .......................................................................................................................... 6-3
6.10 Mechanical........................................................................................................................ 6-4
6.11 Ventilation ........................................................................................................................ 6-4
6.12 Instrumentation and Control............................................................................................. 6-4
6.13 Alarms .............................................................................................................................. 6-5
6.14 Control System ................................................................................................................. 6-5
6.15 Equipment Redundancy.................................................................................................... 6-5
Section 7 Potable Water Pumping Stations...................................................... 7-1
7.1 General.............................................................................................................................. 7-1
7.2 Pump design ..................................................................................................................... 7-1
7.3 Layout of Pumping Station............................................................................................... 7-1
7.5 Pumping Station Requirements ........................................................................................ 7-2
7.6 Control System ................................................................................................................. 7-2
7.7 Instrumentation................................................................................................................. 7-3
7.8 Alarms .............................................................................................................................. 7-3
7.9 Ventilation ........................................................................................................................ 7-4
7.10 Architectural ..................................................................................................................... 7-4
7.11 Site Access Road and Security ......................................................................................... 7-4
Section 8 Well Pumping Station Design............................................................ 8-1
8.1 General.............................................................................................................................. 8-1
8.2 Well Construction............................................................................................................. 8-1
8.3 Well Instrumentation & Control....................................................................................... 8-2
8.4 Alarms .............................................................................................................................. 8-2
8.5 Preferred Layout............................................................................................................... 8-3
8.6 SCADA System................................................................................................................ 8-3

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Section 9 Water Treatment Plants .................................................................... 9-1
9.1 General.............................................................................................................................. 9-1
9.2 Drinking water standards.................................................................................................. 9-1
9.2.1 Microbiological................................................................................................................... 9-2
9.2.2 Naturally occurring chemicals............................................................................................ 9-2
9.2.3 Chemical contaminants....................................................................................................... 9-3
9.2.4 Aesthetic guidelines............................................................................................................ 9-6
9.3 Performance targets and treatment objectives .................................................................. 9-6
9.3.1 General ................................................................................................................................ 9-6
9.3.2 Minimum treatment objectives........................................................................................... 9-7
9.3.3 Additional treatment objectives for Class I water supplies................................................ 9-9
9.4 Calculations of the water treatment performance........................................................... 9-10
9.4.1 General .............................................................................................................................. 9-10
9.4.2 Evaluation of the water treatment efficiency ................................................................... 9-11
9.4.3 Treatment based on physical removal of parasites and virus .......................................... 9-12
9.4.4 Treatment based on chemical inactivation of parasites and virus ................................... 9-14
9.4.5 Treatment based on physical inactivation of parasites and virus..................................... 9-14
9.5 Treatment plant general design....................................................................................... 9-15
9.5.1 Water intake ...................................................................................................................... 9-15
9.5.2 Monitoring......................................................................................................................... 9-15
9.5.3 General design elements ................................................................................................... 9-15
9.6 Disinfection design guidelines........................................................................................ 9-16
9.6.1 Chlorination System.......................................................................................................... 9-16
9.6.2 Ultraviolet Radiation (UV)............................................................................................... 9-18
Section 10 Design of Wastewater Collection System....................................... 10-1
10.2.1 Design Wastewater Flow.................................................................................................. 10-1
10.2.2 Average Dry Weather Flow.............................................................................................. 10-1
10.2.3 Peak Wastewater Flow Factor .......................................................................................... 10-3
10.2.4 Infiltration Allowance....................................................................................................... 10-4
10.3.1 Manning’s Formula........................................................................................................... 10-4
10.3.2 Coefficient of Roughness.................................................................................................. 10-4
10.3.3 Minimum Pipe Size........................................................................................................... 10-4
10.7.1 Location of Wastewater Main .......................................................................................... 10-6
10.7.2 Pipe Depth......................................................................................................................... 10-6
10.7.3 Grid Design ....................................................................................................................... 10-6
10.8.1 Concrete Pipe .................................................................................................................... 10-6
10.8.2 Polyvinyl Chloride Pipe.................................................................................................... 10-6
10.8.3 Polyethylene Pipe.............................................................................................................. 10-7
10.8.4 Glass Reinforced Plastics (GRP) Pipes and Fittings........................................................ 10-7
10.8.5 Ductile iron........................................................................................................................ 10-7
10.9.1 Maintenance Chamber Design.......................................................................................... 10-7
10.9.2 Manhole Hydraulics.......................................................................................................... 10-8
10.10.1 Street Line Connection ..................................................................................................... 10-8
10.10.2 Connection Size and Grade For Multi Family Sites ........................................................ 10-8
10.10.3 Pipe Material ..................................................................................................................... 10-9
10.11.1 System Design................................................................................................................... 10-9
10.11.2 Pipe Size............................................................................................................................ 10-9
10.11.3 Pipe Depth....................................................................................................................... 10-10
10.11.4 Tracer Wire ..................................................................................................................... 10-10
10.11.5 Thrust restraint ................................................................................................................ 10-10

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Section 11 Wastewater Treatment Plants......................................................... 11-1
11.1 General............................................................................................................................ 11-1
11.2 Wastewater Effluent treatment objectives...................................................................... 11-2
11.3 Wastewater Loads........................................................................................................... 11-2
11.4 Plant Layout.................................................................................................................... 11-2
11.5 Plant Design Capacity..................................................................................................... 11-3
11.6 Equalization tank ............................................................................................................ 11-3
11.7 Pre treatment – Inlet Works............................................................................................ 11-3
11.8 Secondary and tertiary treatments .................................................................................. 11-4
11.9 Disinfection System........................................................................................................ 11-4
11.9.1 Chlorination System.......................................................................................................... 11-5
11.9.2 Ultra-Violet (UV )............................................................................................................. 11-6
11.9.3 Sulphur Dioxide System................................................................................................... 11-7
11.10 Sampling and monitoring ............................................................................................... 11-7
11.11 Odor Control................................................................................................................... 11-7
11.12 Structural consideration.................................................................................................. 11-8
11.13 Water reuse for irrigation................................................................................................ 11-8
11.14 Control System ............................................................................................................... 11-8
11.15 SCADA System.............................................................................................................. 11-9
11.16 Equipment Redundancy.................................................................................................. 11-9
11.17 Stormwater management ................................................................................................ 11-9
11.17.1 Combined Sewer System vs. Separate Sanitary Sewer.................................................... 11-9
11.17.2 Runoff impact.................................................................................................................... 11-9
11.17.3 Requirements................................................................................................................... 11-10
Section 12 Wastewater Pumping Stations........................................................ 12-1
12.1 General............................................................................................................................ 12-1
12.2 Wastewater Pumping Station General Design................................................................ 12-1
12.3 Wastewater Pumping Station Layout ............................................................................. 12-1
12.4 Configuration of Pumping System ................................................................................. 12-2
12.5 Wastewater Pumping Station Sizing Design .................................................................. 12-1
12.6 Wastewater Pumping Station (Inflow less than 20 l/s)................................................... 12-1
12.7 Wastewater Pumping Station (20 l/s<Inflow < 200 l/s) ................................................. 12-1
12.8 Wastewater Pumping Station (Inflow > 200 l/s) ............................................................ 12-1
12.9 Pump Design................................................................................................................... 12-2
12.10 Piping & Valve Design................................................................................................... 12-2
12.11 Corrosion resistance........................................................................................................ 12-3
12.12 Pump Controls ................................................................................................................ 12-3
12.13 Odour Control................................................................................................................. 12-4
12.14 Ventilation ...................................................................................................................... 12-4
12.15 Equipment and Material Specifications.......................................................................... 12-4
12.16 Site Access Road and Security ....................................................................................... 12-5
12.17 Instrumentation & Control Alarms................................................................................. 12-5
12.18 SCADA System.............................................................................................................. 12-6
12.19 Equipment Redundancy.................................................................................................. 12-6
Section 13 Septage & Biosolids Management .................................................. 13-1
13.1 Septage Management – General ..................................................................................... 13-1
13.1.1 Stabilisation pond.............................................................................................................. 13-1
13.1.2 Wastewater Treatment Plant............................................................................................. 13-1

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13.1.3 Alkali treatment................................................................................................................ 13-2
13.2 Biosolids Management - General ................................................................................... 13-2
13.3 Sludge stabilization......................................................................................................... 13-3
13.3.1 Aerobic digesters............................................................................................................... 13-3
13.3.2 Anaerobic digesters........................................................................................................... 13-3
13.4 Incineration and heat treatment ...................................................................................... 13-4
13.5 Dewatering...................................................................................................................... 13-4
13.5.1 Sludge drying beds............................................................................................................ 13-5
13.5.2 Vacuum filters, belt filters, belt filter presses, and other mechanical dewatering filters 13-5
Section 14 Architectural Standards .................................................................. 14-1
14.1 General............................................................................................................................ 14-1
14.2 Laboratory control .......................................................................................................... 14-1
14.3 Roofing Design............................................................................................................... 14-1
14.4 Windows......................................................................................................................... 14-2
14.5 Doors .............................................................................................................................. 14-2
14.6 Ceiling ............................................................................................................................ 14-2
14.7 Wall Finishes .................................................................................................................. 14-2
14.8 Floor Finishes ................................................................................................................. 14-2
14.9 Light Fixtures ................................................................................................................. 14-3
14.10 Landscaping.................................................................................................................... 14-3
Section 15 Structural Standards........................................................................ 15-1
15.1 General............................................................................................................................ 15-1
15.2 Design of Water Retaining Structure.............................................................................. 15-1
15.3 Construction Requirements ............................................................................................ 15-1
15.4 Structural requirements................................................................................................... 15-1
15.4.1 Concrete ............................................................................................................................ 15-1
15.4.2 Steel Reinforcement.......................................................................................................... 15-2
15.4.3 Precast Structural Concrete............................................................................................... 15-2
15.4.4 Structural Steel.................................................................................................................. 15-3
15.4.5 Steel protection.................................................................................................................. 15-4
15.4.6 Concrete Block Masonry (C.B.M.) .................................................................................. 15-4
Section 16 Electrical Standards......................................................................... 16-1
16.1 General............................................................................................................................ 16-1
16.2 Equipment Identification Nameplates Requirements ..................................................... 16-1
16.3 Wiring Identification ...................................................................................................... 16-2
16.4 Panel Boards................................................................................................................... 16-2
16.5 Seismic braces ................................................................................................................ 16-2
16.6 High Efficiency Electrical Motor ................................................................................... 16-2
16.7 Motor Control Centre ..................................................................................................... 16-2
16.8 Transformers................................................................................................................... 16-3
16.8.1 High Efficiency Transformers .......................................................................................... 16-3
16.8.2 Distribution Transformers................................................................................................. 16-3
16.9 Co-ordination Studies of Protective Devices.................................................................. 16-3
16.9.1 Co-ordination Studies of Protective Devices Report ....................................................... 16-3
16.9.2 Short Circuit and Protective Device Evaluation and Co-ordination Study ..................... 16-4
16.9.3 Protective Device Co-ordination Study............................................................................ 16-4
16.9.4 Power System Study Report ............................................................................................. 16-5
16.9.5 Insulation Resistance Tests............................................................................................... 16-5
16.9.6 Lamps................................................................................................................................ 16-5

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Section 17 Instrumentation & Control ............................................................. 17-1
17.4.1 Design Criteria .................................................................................................................. 17-2
17.4.2 Interlocks........................................................................................................................... 17-2
17.4.3 Field Instrument................................................................................................................ 17-3
17.4.4 Indicators........................................................................................................................... 17-4
17.4.5 Instrumentation Loops (Analogue)................................................................................... 17-4
17.4.6 Control Circuits................................................................................................................. 17-4
17.4.7 Automation of Treatment Process .................................................................................... 17-5
17.4.8 Variable Frequency Drive (VFD) Control ....................................................................... 17-6
17.4.9 Pump Control Systems for Wastewater Pumping Stations.............................................. 17-7
17.4.10 PLC/RPU Interface ........................................................................................................... 17-7
17.4.11 Services ............................................................................................................................. 17-7
17.4.12 Documentation.................................................................................................................. 17-7
17.4.13 Preventive Maintenance Program..................................................................................... 17-8
17.4.14 Testing and Commissioning ............................................................................................. 17-9
Section 18 SCADA System................................................................................. 18-1
18.2 SCADA Operating Characteristics................................................................................. 18-1
18.3 SCADA System Requirements....................................................................................... 18-2
18.4 SCADA System Control Levels ..................................................................................... 18-2
18.4.1 Field (Local)...................................................................................................................... 18-2
18.4.2 Level 1 – Programmable Logic Controller (PLC) ........................................................... 18-3
18.4.3 Level 2 – PLANT.............................................................................................................. 18-3
18.8.1 Screen................................................................................................................................ 18-7
18.8.2 Button Bars........................................................................................................................ 18-7
18.8.3 Overview Screens ............................................................................................................. 18-8
18.8.4 Pop-Up Screen .................................................................................................................. 18-8
18.8.5 Control Pop-Ups Screens.................................................................................................. 18-8
18.8.6 Information Pop-Ups Screens........................................................................................... 18-9
18.8.7 Setpoint Pop-Up Screens .................................................................................................. 18-9
18.10.1 Raw Water Monitoring Parameters (Water) .................................................................. 18-12
18.10.2 Treated Water Monitoring Program (Water).................................................................. 18-13
18.10.3 Distribution System Monitoring Program (Water) ........................................................ 18-14
18.10.4 Raw Water Monitoring Program (Wastewater) ............................................................. 18-15
18.10.5 Treated Water Monitoring Program (Wastewater) ........................................................ 18-15
18.10.6 Process Parameters Monitoring Program (Wastewater) ................................................ 18-15
18.11.1 Trend Display Requirements .......................................................................................... 18-16
18.11.2 Water Treatment Plant Operating Statistics ................................................................... 18-16
18.11.3 Wastewater Treatment Plant Operating Statistics.......................................................... 18-19
18.13.1 Process Control Display.................................................................................................. 18-20
18.13.2 Standard Colour Convention – Process Stream ............................................................. 18-20
18.13.3 Standard Colour Convention – Pump/Motor/Valve....................................................... 18-21
18.14 Symbols ........................................................................................................................ 18-21
18.17.1 General ............................................................................................................................ 18-22
18.17.2 SCADA System Operation Manual Requirements........................................................ 18-23
18.18 System Architecture...................................................................................................... 18-26
18.24.1 PLC Program Structure................................................................................................... 18-28
18.24.2 PLC Programming Protocol............................................................................................ 18-29
Section 19 Mechanical Standards...................................................................... 19-1
19.1 General............................................................................................................................ 19-1
19.2 Valves............................................................................................................................. 19-1
19.3 Fittings............................................................................................................................ 19-1

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19.4 Pumps ............................................................................................................................. 19-2
19.5 Piping & Equipment Identification................................................................................. 19-3
19.5.1 General .............................................................................................................................. 19-3
19.5.2 Security equipment ........................................................................................................... 19-3
19.5.3 Piping Identification Labels.............................................................................................. 19-4
19.5.4 Colour Legend................................................................................................................... 19-4
19.5.5 Method of Application...................................................................................................... 19-6
19.5.6 Sizes of Characters............................................................................................................ 19-7
19.5.7 Location of Labels ............................................................................................................ 19-7
19.5.8 Pumps & Valves Colour Schedule ................................................................................... 19-8
19.5.9 Nameplates........................................................................................................................ 19-9
19.5.10 Equipment Name Tags.................................................................................................... 19-10
19.6 Equipment..................................................................................................................... 19-10
19.6.1 Bearings........................................................................................................................... 19-10
19.6.2 Pump Shaft Seals ............................................................................................................ 19-10
19.6.3 Couplings ........................................................................................................................ 19-10
19.6.4 Equipment Guard ............................................................................................................ 19-10
19.6.5 Gauge Taps and Test Plugs............................................................................................. 19-10
19.6.6 Alignment........................................................................................................................ 19-11
19.7 Equipment Maintenance Requirements........................................................................ 19-11
Section 20 Ventilating & Air Conditioning Standards.................................... 20-1
20.1 General............................................................................................................................ 20-1
20.2 VAC System................................................................................................................... 20-1
20.3 Minimum Air standard ................................................................................................... 20-2
20.4 System Redundancy........................................................................................................ 20-2
20.5 VAC Control System...................................................................................................... 20-2
20.5.1 VAC Master Control......................................................................................................... 20-2
20.6 Verification of VAC System .......................................................................................... 20-2
20.7 Location of air intakes .................................................................................................... 20-2
Section 21 Diesel Generator Standard.............................................................. 21-1
21.1 General............................................................................................................................ 21-1
21.2 Power Supply.................................................................................................................. 21-1
21.3 Approvals........................................................................................................................ 21-1
21.4 Noise Attenuation........................................................................................................... 21-1
21.5 Diesel Generator Power Requirements........................................................................... 21-2
21.5.1 Water Supply System........................................................................................................ 21-2
21.5.2 Wastewater Pumping Station............................................................................................ 21-2
21.5.3 Ancillary Electrical and Mechanical Equipment ............................................................. 21-2
21.6 Diesel Generator System Operation ............................................................................... 21-2
21.7 Diesel Engine Requirements........................................................................................... 21-3
21.7.1 General .............................................................................................................................. 21-3
21.7.2 Flame Detection System................................................................................................... 21-3
21.7.3 Fuel System....................................................................................................................... 21-3
21.7.4 Speed Governor................................................................................................................. 21-3
21.7.5 Fuel Tank........................................................................................................................... 21-4
21.7.6 Oil Lubricating System..................................................................................................... 21-4
21.7.7 Intake and Exhaust System............................................................................................... 21-4
21.7.8 Cooling System................................................................................................................. 21-4
21.7.9 Ventilation System............................................................................................................ 21-4
21.7.10 Gauges............................................................................................................................... 21-5
21.7.11 Battery Start System ......................................................................................................... 21-5

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21.7.12 Failure Annunciator .......................................................................................................... 21-5
21.8 Generator Requirements ................................................................................................. 21-5
21.8.1 General .............................................................................................................................. 21-5
21.8.2 Voltage Regulator ............................................................................................................. 21-6
21.9 Control System ............................................................................................................... 21-6
Section 22 Treatment Plant Operation Manual............................................... 22-1
22.1 General............................................................................................................................ 22-1
22.2 Operation Manual Requirements.................................................................................... 22-1
22.3 Format of Operation Manual .......................................................................................... 22-1
22.4 Water Treatment Plant Operation Manual...................................................................... 22-2
22.5 Wastewater Treatment Plant Operation Manual............................................................. 22-4
22.6 Training on the Use of the Operation Manual................................................................ 22-8
22.7 Training of WASA Staff................................................................................................. 22-9
22.7.1 Training Provided by the Contractor................................................................................ 22-9

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List of Abbreviations
AI Analogue Input
AO Analogue Output
ANSI American National Standard Institute
ARI Air-Conditioning and Refrigeration Institute
ASHRAE American Society of Heating, Refrigerating and Air-conditioning
Engineers
AWWA American Waterworks Association
CAD Computer Aided Design
CIBS The Chartered Institution of Building Services
CPM Critical Path Method
CV Curriculum vitae
CVS Certified Value Specialist
DI Digital Input
DO Digital Output
DTC Direct Torque Control
EA Environnemental Analysis
EIA Environmental Impact Assessment
EPA Environmental Protection Act
FAT Factory Acceptance Test
FIDIC Federation Internationale Des Ingenieurs – Conseils
(International Federation of Consulting Engineers)
HAZOP Hazard and Operability Study
HFS Hydrofluosilicic Acid
HLPS High Lift Pumping Station
I&C Instrumentation and Control System (I&C)
I/O Input / Output
LOH Loss of Head
MCC Motor Control Centre
MoWT Ministry of Works and Transport
MoALMR Ministry of Agriculture, Land and Marine Resources
EMA Environmental Management Agency
MoH Ministry of Health
MoPD Ministry of Planning and Development

Project Design and Technical Specifications Manual List of Abbreviations
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MoPUE Ministry of Public Utilities and the Environment
NSF National Sanitation Foundation
NTU Nephelometric Turbidity Units
P&ID Proportional and Integral Derivative
PDR Pre-Design Report
PID Proportional Integral Derivative
PLC Programmable Logic Controller
QA Quality Assurance
QC Quality Control
RFP Request for Proposal
RIC Regulated Industries Commission
RPU Remote Processing Unit
SAT Site Acceptance Test
SCADA Supervisory, Control and Data Acquisition
SMACNA Sheet Metal and Air Conditioning Contractors' National Association
SPMDD Standard Proctor Maximum Dry Density
THD Total Harmonic Distortion
TKN Total Kjeldahl Nitrogen
TTBS Trinidad & Tobago bureau of Standards
UV Ultra Violet
VAC Ventilation and Air Conditioning
WASA Water And Sewerage Authority of Trinidad & Tobago
WTP Water Treatment Plant
WWTP Wastewater Treatment Plant
WHO World Health Organisation

Water and Wastewater Design Guideline Manual General Information
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Section 1 General Information
As Trinidad & Tobago moves toward a 2020 vision of a modern and developed country, new and
refurbished water and wastewater infrastructures are needed all around the islands. The Water
And Sewerage Authority (WASA) of Trinidad and Tobago has put together this document in
order to guide the engineering design and establish the recommended standards for all new water
and wastewater infrastructure.
WASA has the responsibility for the provision of water supply and sewerage services in Trinidad
and Tobago, under Water and Sewerage Act, chapter 54:40. Increasing the levels of service
provided to the population has been a continuous concern for WASA. The present guidelines are
adapted to Trinidad and Tobago’s context and are compatible with WASA’s long term
operational policies. They present a comprehensive document for the construction and
rehabilitation of new and existing water and wastewater infrastructures.
The 2020 vision requires capital works from the government of Trinidad & Tobago in order to
meet the goals set. The implementation of water, wastewater and linear services projects requires
the services of Consultants to provide the required engineering expertise in accordance with the
requirements as specified herein. Consultants should therefore familiarize themselves with these
guidelines and provide their services accordingly to meet WASA’s expectation.
These guidelines are primarily intended to outline acceptable levels of servicing and minimum
criteria for future infrastructure in Trinidad & Tobago. They will assist consulting engineers,
engineering staff and other designers in the preparation of water and wastewater system
infrastructure design. Some of the design standards, detailed herein this manual, are not currently
used by WASA in the implementation of water and wastewater projects. These include the
Supervisory, Control and Data Acquisition system. However the information contained herein
will serve as a preliminary basis for consideration by WASA and should be followed if no other
directives have been stated.
This Water and Wastewater Design Criteria Manual is the property the Water And Sewerage
Authority (WASA) of Trinidad and Tobago. The design guidelines as detailed herein are for the
implementation of water and wastewater projects, including linear services and treatment plants.
The stipulated design guidelines must be complied with unless dispensation has been obtained in
writing from WASA or specified in the Request for Proposal,
Other References
This manual shall be used in conjunction with:
1. All rules, laws and regulations of the Republic of Trinidad and Tobago
2. Project’s Tender documents
3. WASA requirements and standards
4. Policies and Guidelines from stakeholders

Water and Wastewater Design Guideline Manual Design Approach & Approvals
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Section 2 Design Approach & Approvals
2.1 Introduction
These guidelines do not supersede nor replace any legislation governing the design of such
treatment plants. Options and design optimisation are still to be conducted and investigated at the
prefeasibility level. The Consultants must be fully familiar with Trinidad & Tobago legislations
with respect to the design of water and wastewater infrastructure.
The guidelines and standards, as provided herein, were set by WASA in order to guide and frame
the engineering and consultancy works and assure a standardised and adequate design level in
the implementation of such systems. Approvals by WASA of infrastructures will require
compliance to these guidelines in conformity with WASA’s Water and Wastewater Policies.
Since standards, technology and priorities evolve, this manual is aimed to be reviewed frequently
and consultants are to assure that they are using the latest revision.
2.1.1 Multi barrier approach
In conformity with WASA’s policies, in order to ensure clean, safe and reliable drinking water, a
multi barrier approach is to be implemented from the source all the way to the consumer's tap.
This requires an understanding of the general characteristics of the water, the watershed or land
surrounding the water source, as well as mapping all the potential threats to the water quality.
The approach of the required design is to provide for barriers to either eliminate the threats or
minimize their impact. It includes protecting the available source from contamination, using
effective water treatment, and preventing water quality deterioration in the distribution system.
Together the barriers work to provide greater assurance that the water will be safe to drink.
2.1.2 Sustainable development
An integrated water resources perspective ensures that social, economic, environmental and
technical dimensions are taken into account in the management of water resources. WASA
wishes to promote practices that encourage sustainable development so there won’t be any
compromising of future generations’ ability to meet their needs.
As examples, protection of well’s head, installation of domestic water meters, and setting
wastewater effluent standards are part of the sustainable approach provided in this manual.
These are some of the good practices needed to assure long term sustainable and valuable water
for Trinidad & Tobago.
The water treatment standards and guidelines are established to ensure production of safe
drinking water. The amount and minimum scale of treatment processes are based on type and
quality of raw water, including their variability.

water, wastewater and linear services projects Design Approach & Approvals
2-2 October 2008
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2.2 Design Guidelines
This manual provides details on the design of water and wastewater related infrastructure so that
a standard of quality, reliability and uniformity will be achieved for WASA services to the
population of Trinidad & Tobago. It covers a wide range of applicable standards and
characteristics that need to be considered in order to assure the minimal quality requested. Items
covered by this manual include the following:
1. Equipment redundancy
2. Architectural standard
3. Structural standard
4. Underground pipelines
5. Electrical standard
6. Mechanical standard
7. Instrumentation & control standard
8. Emergency standby diesel generator standard
9. Equipment coding system standard
10. Operation & maintenance manual standard
11. Water quality and treatment standard
12. Wastewater effluent and treatment standards
13. SCADA
2.3 Review process of the guidelines
As technology, exigencies and standards evolve; these guidelines will have to be submitted for a
regular review by WASA in order to reflect the latest findings and comments. It is recommended
that this document be revised at minimum every five (5) years to comply with the best interest of
the population of Trinidad & Tobago.
2.4 Approvals
The Consultants shall comply with, and shall conduct all work with cognisance given to all
relevant statutory regulations and requirements, and where required, shall apply for all relevant
approvals or certificates.
In all cases, the Water and Sewerage Authority (WASA) should have granted approvals on the
outline and details of all projects prior to the installation of any facility. The WASA’s
administrative procedures are part of another document that must be consulted.

water, wastewater and linear services projects Design Approach & Approvals
2-3 October 2008
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In addition, all projects must meet Environmental Management Authority (EMA) approvals by
obtaining a Certificate of Environmental Clearance (CEC). Depending on the type of project, an
Environmental Impact assessment (EIA) may be required as established by EMA.
The Consultants shall comply with other stakeholders’ Policies and Rules, or tender documents.
They shall prepare all required documents for submission and review with WASA.
The Consultants must deliver to WASA a status report of all the applications for approvals
required for the project. Where there are outstanding approvals, the Consultants shall indicate the
time frame within which these approvals are expected to be in place.
Consultants are responsible for ensuring that plants designed by them comply with Acts, Codes,
Standards and Guidelines. The Standards and Guidelines provided in this manual are intended to
set the minimum acceptable standard and not to relieve them of their responsibilities to comply
with their legal and contractual requirements and obligations.
For detailed information about WASA’s administrative procedures for review, including costs,
type and number of copies of documents to submit for approval, consult WASA’s approval
process documentations.

Water and Wastewater Design Guideline Manual Design Standards
3-1 October 2008
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Section 3 Design Standards
3.1 Design requirements
It is the Consultant’s responsibility to ensure that they have fully understood the requirements of
the project as detailed in the Request for Proposal as they will be required to fulfil the specified
scope of work.
The infrastructure work includes both water and wastewater projects. WASA retains the services
of Consultants to provide the required engineering expertise to implement these projects in an
integrated manner with all building, safety and quality requirements. WASA requires and
expects that the Consultant will comply with the requirements as specified herein and therefore
provide their services accordingly to meet this expectation.
All materials and equipment supplied shall be suitable for being delivered, store and operated
under tropical conditions of high temperature, high humidity, heavy rainfall, mildew and fungus
conductive environment.
All WASA buildings or structures shall be flood proof. The site for the new facility shall be
appropriately selected or designed to be above the 20 years recurrence interval flood line.
When standards are provided, they are minimum requirements to be met by the system. When
specified, these standards are mandatory unless otherwise specified in writing by WASA.
Mandatory standards include drinking water quality standards and wastewater treatment plant
effluent standards.
3.2 Acts, Codes and Standards
The design of infrastructure shall comply with the following regulations, Acts, Codes, Standards,
Guidelines for all projects undertaken by Consultants on behalf of WASA:
1. Environmental Management Authority (EMA) of T&T
2. Water And Sewerage Authority (WASA) of Trinidad and Tobago
3. Ministry of Public Utilities and Environment (MoPUE)
4. National Building Code
5. National Fire Code
6. OSHA
The standards specifications for materials should be consistent with the requirements of the
following:
1. Trinidad and Tobago Standards (TTBS)
2. International Standards (ISO)
3. North American Standards (ANSI/AWWA)

3-2 October 2008
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4. British Standards (BS)
3.3 Other Design & Construction Standards
Consultants shall comply with all Trinidad & Tobago technical rules and regulations related to
the design and construction of treatment plants as well as linear services.
Stakeholders if applicable should be included in the design. The T&T water and wastewater
stakeholders include but are not limited to:
- Ministry of Public Utilities
- Town and Country Planning Division
- Environmental Management Authority (EMA)
- Ministry of Local Government
- Ministry of Works and Transport
- Ministry of Finance
- Ministry of Health
- Regulated Industries Commission
- Ministry of Agriculture, Land and Marine Resources
- Office of the Ombudsman (Ministry of Legal Affairs)
- Consumer Affairs Division (Ministry of Legal Affairs)
- Water Recourses Agency and Forestry Division
- Trinidad & Tobago Fire Services
3.4 Industry Standards
All materials for potable water and sewers shall meet the ASTM, AWWA or other approved
equivalent standards. The Standards also provide literature on Workmanship. The following
standards are listed for guidance and are not final or exclusive to other standards.

3-3 October 2008
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Storage Tanks
Welded Steel Tank
Painting for Welded Steel Tanks
Factory Coated Tanks
Disinfection
Concrete Structures for Retaining Liquids
ANSI/AWWA D100-84
ANSI/AWWA D102-78
ANSI/AWWA D103-80
ANSI/AWWA D652-86
AS 3735 1991
Pipelines
Polybutylene (PB)
Polyethylene (PET)
Poly Vinyl Chloride (PVC)
Fabricated Steel Pipe and Fittings
Steel Pipe Flanges Class D
Coal tar protection coatings and linings for steel water
pipelines
Flanged Ductile Iron Pipelines
Rubber Gasket
Disinfection
Pressure Test
Grey Iron Casting
GRP
Elastometrix Joint Rings for pipework and pipelines
Flanges and bolting for pipes valves and fittings metric
series
(copper alley and composite flanges)
Metal Washers for General Engineering Purposes
Metric Series
Specifications for Poly Vinyl Chloride (PVC) Solvent
Cement for use with unplasticized PVC Pipes and
fittings for cold water applications
Cast Iron Non-pressure pipes and pipe fittings metric
units
AWWA C-902-78
AWWA C-901-78
AWWA C-900-75
AWWA C-208-83
AWWA C-207-86
AWWA C-203-86
AWWA C-115/A21
AWWA C-111/A21
AWWA C-651-86
AWWA C-600-82
BS 1452:1977
AWWA C 950 - ASTM D 3754
BS 2494:1986
BS 4504: Part 2 1974
BS 4320:1968
TTS 413-1992
AS 1631-1974

3-4 October 2008
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Valves
Ball Valves
Rubber Sealed Butterfly Valves
Sluice Valves
Predominantly key Operated Cast Iron Valves for
Waterworks purposes
Butterfly Valves
Copper Alloy Gate Valve and Non-Return Valves for
use in water supply and hot water services
Float Operated Valves
Specifications for Piston Type Float Operated valves
(Copper Ally Body) (Excluding Floats)
Specifications for Diaphragm type float operated valve
(copper Alloy Body) (Excluding Floats)
Specifications for Diaphragm type operated valves
plastic bodies, for cold water services only excluding
floats
Draw off taps and stop valves for water services (screw
down pattern)
AWWA C-507-85
ANSI/AWWA C-50
AWWA C-501-86
BS1 5163:1986
BS 5155:1984
AS 1628:1977
BS 1212
PT 1 1990
PT 2 1990
PT 3 1990
BS 1010 PT 2 1973
Safety Valves
Safety Valves
Specification for safety valves for steam and hot water
BS 6759
PT 1 1984
Mixing Valves
Mixing Valves
Non-Thermostatic, Non-Compensating mixing valves
Specification for Thermostatic mixing valves
BS 1415
PT 1 1976
PT 2 1986

3-5 October 2008
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Various standards
Glass Filament reinforced thermosetting plastics (GRP)
Pipes Polyester Based-Water Supply. Sewerage and
Drainage Applications
Water Supply Metal Bodied Taps – Specified by
performance
Water Well Casing
Specification for steel tubes for casing
Specification for thermoplastics tubes for casing and
slotted casing
Stationary circulation pumps for heating and hot water
service system
Specification for Cold Water Storage and combined
feed and expansion cisterns (polyolefin or olefin
copolymer) up to 500L capacity used for domestic
purposes
Multi Standard
Measurement of flow of cold potable water in closed
conduits
Safety and control Devices for use in hot water systems
Code of Practice for test pumping of Water Well
Storage Cisterns up to 500L Actual Capacity for water
supply for domestic purposes
Bitumen – based coatings for cold application, suitable
for use in contact with potable water
Bitumen based hot applied coating materials for
protecting iron and steel including suitable primers were
required
Water Quality (Multi Standards) Physical, Chemical and
Biochemical methods
AS 3571 1989
AS 3718 – 1990
BS 879
PT 1 – 1985
PT Z – 1988
BS 1394
BS 4213 – 1991
BS 5728
BS 6283
BS 6316 – 1992
BS 7181 – 1989
BS 3416 – 1980
BS1 4147 – 1980
BS 6008
PT 2

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Water Meters
Cold – Water Meters – Multi – Jet Type ANSI/AWWA C 708-82
Cold – Water Meters – Displacement Type
Cold – Waters – Turbine type for customer service
Filtering material
Meters for cold potable water
ANSI/AWWA C 700-7
ANSI/AWWA C 701-78
ANSI/AWWA B 100
AS 3565 - 1988
Water Sampling
Water Quality – Sampling Pt 1 Guidance on
Design of Sampling Programmes 13 p
PT 2 Guidance on sampling technique
PT 3 Guidance on the Preservation and
handling of samples
PT 6 Guidance on sampling of rivers and
streams
PT 8 Guidance on sampling of Wet
depositions
PT 9 Guidance on sampling from marine
waters
PT 10 Guidance on sampling of waste waters
PT 11 Guidance on sampling of Ground waters
ISO 5667 – 1980
ISO 5667 – 1991
ISO 5667 – 1987
ISO 5667 – 1990
ISO 5667 – 1993
ISO 5667 – 1992
ISO 5667 – 1992
ISO 5667 – 1993
Water Testing of Pipes
Methods of test for unplasticized polyvinyl chloride
(PVC) Pipes. PT4 - Effects of Sulphuric Acid –
Requirements and Test method
Method of test for unplasticized PVC pipes and fittings
PT 3 - Determining the fracture toughness of UPVC
Pipes
Methods of test for unplasticized PVC pipes
PT8 - Method for Hydrostatic pressure testing of UPVC
short term test
Methods of test for unplasticized PVC Pipes PT 9 -
Methods of test for hydrostatic pressure testing of
UPVC pipes long term test
Methods of test for unplasticized polyvinyl chloride
TTS 16 80 30
PT 4 - 1991
TTS 16 80 30
PT3 - 1991
TTS 16 80 30
PT8 - 1991
TTS 16 80 30
PT9 - 1991
TTS 16 80 30
PT7 1991

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(PVC) Pipes PT 7 - resistance to external blows
Wastewater systems
Cement
Aggregate
Steel (Reinforcer)
Structural Steel
Manhole Bricks
Precast Sections
Manhole Frames Cones
Reinforced Concrete Pipes
Non reinforced Concrete Pipes
Welded Steel Pipe
Steel Fitting Couplings
Gate Valves
Sluice Valves
Drain Pipes and Fittings
Sewer
Grey iron
Ductile Iron
Thermoplastic Pipe for Sewers
Thermoplastics waste pipes and fittings
Polypropylene Waste pipe and fittings
(external Diameter 34.6 mm 41.0 mm 54.1mm)
Unplasticized PVC (UPVC) Pipes and Fittings for storm
and surface water applications
Unplasticized PVC (UPVC) Pipes and Fittings for soil
waste and vent (SWV) applications
Design charts for water supply and sewerage
Water supply – Mechanical backflow prevention devices
Plastics Waste Fittings
Specifications for compact type float operated valves for
WC Flushing Cisterns (including floats)
Specification for Galvanized low Carbon Steel, Cisterns,
lid tanks and Cylinders
Specification for unplasticized PVC Drain, Waste and
vent pipes
Technical Drawing Installation, Graphical symbols for
supply water and drainage systems
ASTM C-150 -60
ASTM C-33-59
ASTM A-15-58T
ASA-ASA A57 1-1952
ASTM C-32-58 Grade MA
ASTM C-478-61T usina
Type II cement
ASTM A48-60T
ASTM C76-60T
ASTM C14-59, l
AWWA C 202-59
AWWA (Same as Water)
ASA B16 10-1957
AWWA C 501-41T
BS 4660
BS 4660, BS 5481 or Class
B, BS 3505
BS 4622
BS 4772
ASTM D 2321, F-894
BS 5255 – 1989
BS 5254 – 1976
AS 1254
AS 1415 PT 1-4
AS 2200-1978
AS 2845-1986
AS 2887 – 1986
PT 4 -1991
BS 417
TTS 414-1992
TTS 31 85 006
PT 6 – 1998
Recommendations for the Design of buildings,
plumbing and drainage systems
TTS 16 90 400
PT 4 - 1985

Water and Wastewater Design Guideline Manual Process and Equipment Redundancy
4-1 October 2008
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Section 4 Process and Equipment Redundancy
4.1 General
The provision for process and equipment redundancy depends on the process and/or the
functionality of the associated process equipment. In the design of Water and Wastewater
facilities, Consultants must ensure that the level of redundancy for process and/or equipment is
provided such that the treated wastewater effluent or quality of the drinking water will be in
compliance with the Design guidelines & Environmental Management Authority (EMA)
Certificate of Environmental Clearance Rules or objectives at all times.
The current standard for provision of process and equipment redundancy level in water and
wastewater treatment plants is minimal. As existing plants are upgraded or expanded in the
future, key process equipments are to be provided with the redundancy level to safeguard the
supply of potable water or the discharge of treated wastewater to the environment.
4.2 Minimum redundancy – Wastewater systems
To ensure that the plant’s treated wastewater effluent will be in compliance with WASA’s
criteria or objectives at all times, the following minimum level of redundancy for equipment and
treatment processes shall be provided:
1. To ensure that the process train is available to meet the wastewater plant’s treatment capacity
requirements, the minimum redundancy of unit processes such as aeration tankages,
clarifiers, screens, etc. shall be equal to 50% of the total design capacity with the largest unit
processes out of service.
2. Similarly, to ensure that the wastewater flow will be handled to meet the required hydraulic
throughput, pumping stations shall be generally sized and installed with a 100% redundancy
with the largest equipment unit out of service. See section 12 for more details.
3. Pipe lines and forced mains do not require redundancy.
4.3 Minimum redundancy – Drinking Water systems
To ensure that the drinking water quality will be in compliance with WASA’s criteria or
objectives at all times, the following minimum level of redundancy for equipment and treatment
processes shall be provided:
1. To ensure that the process train is available to meet the drinking water treatment plant’s
capacity requirements, the minimum redundancy of unit processes such as clarifiers,
chemical dosers, filtration unit, etc. shall be equal to 100% of the total design capacity
with the largest unit processes out of service.
2. Similarly, to ensure that the water flow will be handled to meet the required hydraulic
throughput, pumping stations shall be sized and installed with a 100% redundancy with
the largest equipment unit out of service. Other distribution equipment such as piping,

4-2 October 2008
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valves, pressure reducing valves and water tanks do not require redundancy. See section
7 for more details.
3. Main water trunk systems should allow for some level of redundancy by aiming for
smaller double parallel pipe layout with adequate valving rather than one large pipe
diameter.
4.4 Standby Power
Whenever feasible, power supply to WASA’s plants shall be provided with dual feed from the
power supply grid network. Where this is not possible, standby power shall be provided in the
following key process system:
1. Wastewater treatment plant
.1 SCADA System
.2 Plant VAC System
.3 Plant disinfection system
.4 All equipment required to enable effective treatment for plants discharging in
environmentally sensitive areas.
2. Water intake pumps and equipment
3. Water Treatment Plant
.1 All equipment that is required to be operational to enable the water treatment plant to
meet average day demand is to be provided with standby power or an alternate source of
power.
3. Potable Water Pumping Station on main trunk systems. Other pumping stations shall be
assessed to establish criticality based on network configuration, gravity feed reservoirs, type
of supplied customers etc.
4. Wastewater Pumping Station
Power ratings for standby power are defined by ISO 8528-1 as the power available in the event
of a main power network failure up to a maximum of 500 hours per year of which up to 300
hours may be run continuously. Load factor may be up to 100% of standby power. No overload
is permitted.
4.5 Standardization of Equipment
Consultants shall ensure that the selection of equipment for use in the plants shall be
standardized as much as possible. In all cases, consultants must first refer to WASA’s available
list of approved suppliers and manufacturers for each application. For each process, the variety
of major equipment manufacturers should be limited to a maximum of three. The advantages of
keeping the selection of equipment to a maximum of three are:

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1. Reduction of time required to review design information
2. Minimize the inventory of spare parts
3. Reduction of time for staff to become fully familiarized with new equipment and facility
In general, consideration shall be given for new equipment to be from the same manufacturer as
those that are already installed in the same unit process train. This requirement will be reviewed
at the detailed design stage and alternate equipment or technology will be considered at that time.
Approved and alternate equipment shall be specified in the tender document such that WASA
has the right to accept or reject any equipment that the Contractor proposes to supply under the
contract.

Water and Wastewater Design Guideline Manual Design of Water Distribution System
5-2 October 2008
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Section 5 Design of Water Distribution System
5.1 General Requirement
This section outlines the requirements for the design of water supply systems. However, the
Consultants shall apply sound engineering judgement and approach to the design of such
systems. All designs shall comply with Trinidad & Tobago National Plumbing Code, AWWA
Standards of Practice and Specifications, relevant codes or design guidelines. The designs must
as much as it’s applicable, include mechanism for water conservation, including but not limited
to pressure control devices, low flush toilets, low volume faucets, etc.
Notwithstanding the above, the Consultants shall be familiar with the policy and standards
related to fire protection services requirements in Trinidad & Tobago.
In all projects, assessment of trenchless construction techniques and rehabilitation methods for
existing pipes shall be thoroughly prepared. The assessment shall as a minimum cover the
geotechnical conditions, traffic disruptions, survey the existing utilities and sub surface
structures, obtain right-of-way and property line information, take account of possible
improvements to street or utilities, risk and safety, and include technology aspects on
construction and costs etc.
For all new communities, the Consultants shall establish the geodetic invert elevations and ties of
all water service connections at the street line. All of this information shall be incorporated on
the “As-built” plans. To avoid proliferation of booster stations and reservoirs within each
development, each project should be assessed through modelling of regional network and
optimum development scheme. WASA’s Master Plan for Trinidad & Tobago should be reviewed
to grasp the bigger communities and regional planning priorities.
5.2 Water Demand
In the past years, many studies have been undertaken to assess the water demand for the different
types of consumers in Trinidad & Tobago. The available information is usually scarce and
significant variations exist between the different studies. The following design criteria for water
demands is based on different sources, notably the 1994 “Project Memoranda on Existing and
Future Demands” by William Halcrow & Partners Ltd., the 2006 “Analysis and Estimation of
Water Demand Forecasts” by Gordon Wyke, and various international figures including British
and North American standards.
5.2.1 Design Water Demand
The system shall be designed to meet the greater of either of the following demands:
1. Maximum Daily Demand Plus Fire Flow
2. Maximum Hourly Demand

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Where applicable, individual studies shall be conducted for the following:
1. Special commercial establishments and major commercial areas
2. Special industries and major industrial areas
3. Institutional development
4. High density residential areas
5.2.2 Average Water Demand (light industrial and commercial)
If individual data is not available, the following typical numbers should be used in order to
establish the daily average flow demand for light commercial and industrial facilities (sources :
WASA, Metcalf & Eddy) :
Facilities - Consummation per usage [L/(capita·d) or L/(unit·d)]
Airport (per passenger) 15
Shopping malls
Per parking spot 8
Per employee 40
Vacation center
Vacation colony ; central bathroom (per person) 160 – 200
Workers
Work camp with bath facilities (per worker) 140 – 200
Theatre
Per seat 10
Outdoor (per car) 15
School (per student)
With cafeteria 50 – 60
With cafeteria, shower and gymnasium 80 – 100
Boarding school or University Dormitory 285
Offices (per employee) 60
Health care facilities
General hospital (per bed) 1000
General hospital (per employee) 40
Other institution (per bed) 400
Hotels and hostels
Hotel room (per client) 200 - 300
Room and pension (per person) 200
Motel with kitchen 400 – 600
Laundry self service (per customer) 190

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Conference center (per person) 30
Stores
Per customer 8
Per employee 40
Restaurants
Medium size restaurant (per seat) 150
Medium size restaurant; open 24 h (per seat) 200
Bar (per place) 80
Gas station
Per car served 30
Per employee 50
Industrial facility (small to medium size)
Without cafeteria or shower (per employee) 70
With cafeteria and shower (per employee) 140
5.2.3 Residential Per capita demand
Residential Water demands have been historically high in Trinidad & Tobago. As water meters
are installed throughout the country, it is expected that residential water consumption will
linearly be lessened by 10% by 2020. When possible, per capita consumption and peaking
factors should be determined from historical data for the area. The following design factors,
based on the “Water Consumption & Demand Study” GENIVAR (2008), are to be used for the
design of residential water distribution systems in the absence of actual flow data:
Water demand 2007 2020
Residential per capita demand
Trinidad
330 litres/cap.d 280 litres/cap.d
Residential per capita demand
Tobago
315 litres/cap.d 280 litres/cap.d
Note : The demand per capita does not include any unaccounted for water (UFW) which is
historically very significant in Trinidad & Tobago. Depending on the region, the project and the
state of the distribution system, a case by case analysis is required for each project to include the
UFW and leakages of the system.
Maximum Daily and Maximum Hourly Demand Factors as noted in the table below:

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Peak Demands: Peak Day Peak Hour
Population 0 - 1,000 3 x Avg. Day 1.5 x Peak Day
Population 1,000 - 5,000 2.5 x Avg. Day 1.5 x Peak Day
Population 5,000 – 25 000 2.0 x Avg. Day 1.5 x Peak Day
Population > 25 000 1.5 x Avg. Day 1.5 x Peak Day
5.2.4 Equivalent Population
The design population is to be the ultimate for the area under consideration, the design life
threshold or local recommendation. The following equivalent population densities shall be used
to estimate the water service demand for the different types of developments in the design of
water distribution systems.
The average daily demand shall take into account water distribution system leakages, water
conservation as well as night time usage. The daily minimum flow is set as 35% of the average
daily flow.
3. Recommended flows to be used are (area is development area excluding major public streets,
freeways and railroad areas):
Single Family Residential 13 litres/min/ha
Multi-Family Residential 20 litres/min/ha
Walk-up Apartments 26 litres/min/ha
Community Services 10 litres/min/ha
Light Commercial 22 litres/min/ha
Light Industrial 40 litres/min/ha
5.2.5 Fire Flow Requirements
5.2.5.1 Policy and Standards related to Fire Protection
The 2020 vision aims to provide an adequate water supply for fire fighting for every building. In
general, fire flow requirements are established in close collaboration with insurance companies
and must involve capacity assessment of the Trinidad and Tobago Fire Services (TTFS). Since
insurance risk assessments or fire protection technical guidelines are yet to be established, the
following guidelines are to be used, derived from different sources including Fire Underwriters
Survey (FUS) and NFPA.
5.2.5.2 Reservoir Storage Capacity Requirements
Total reservoir storage capacity requirements shall be designed to be equal to the sum of the fire
storage requirements, 18 hours of average daily demand, plus emergency storage, which is 25%
of the sum of fire storage capacity and annual average daily demand. See section 6 for more
details.

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The required fire storage capacity may be equal to:
Vrc = Vfs + 0,75 Vad + 0.25(Vfs +Vad)
Where Vrc = Total reservoir water storage capacity requirement
Vfs = Fire storage capacity required
Vad = Annual average daily demand
Pressure zones with reservoirs should allow local pressure zone area of 40 to 80 psi (28 m to 56
m). In all cases, the pressure shall not be over 100 psi (70 m) and below 20 psi (14 m) for all
sectors supplied by the reservoir as recommended by the Regulated Industries Commission.
5.2.5.3 Fire Flow
For residential areas, the minimum acceptable fire flow shall be as stated in the following table
for a duration of minimum 1 hour with a residual pressure of 140 kPa (20 psi). For other types of
consumers, the fire flow shall be calculated on a case-by-case basis, but shall always exceed the
minimum residential fire flow requirements. Unless specified, major industrial sites are not to be
protected by the public water network. The required fire flow demand shall be supplied from at
least two fire hydrants.
Development Type Fire Demand (usgpm) Fire Demand (lpm)
Residential 1 000 3 800
5.3 Hydraulic Design
5.3.1 Pipe Design Flow
The Consultants may use the following Hazen Williams equation or the Darcy-Weisbach
equation in the design of watermains:
f = 0.2083 (100/c)1.852
q1.852
/ dh
4.8655
where
f = friction head loss in feet of water per 100 feet of pipe (fth20/100 ft pipe)
c = Hazen-Williams roughness constant
q = volume flow (gal/min)
dh = inside hydraulic diameter (inches)
5.3.2 Hazen Williams roughness coefficient
The Hazen-William’s coefficients for water pipelines equal to or less than 300 mm diameter
shall be set at 120 with no regard to pipe material. For pipe larger than 300 mm, use the
following table :

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Pipe Material Hazen William’s “c” Coefficients
Ductile Iron 130
HDPE 140
PVC or FRP 140
Steel 130
5.3.3 Standard Pipe Sizes
The Consultants shall use the following standard pipe sizes for the design of water distribution
systems:
150, 200, 300, 400, 450, 500, 600, 750, 900, 1050, 1200 mm diameter. No larger or other
diameter pipes shall be used prior to a written approval by WASA. In all cases, Consultants
must first refer to the WASA approved supplier and manufacturer list for approved supplier
and available diameters.
5.3.4 Minimum Pipe Sizes
The minimum pipe size for residential areas shall be 150 mm diameter. The velocity of water
flow should be between 0.9 and 1.55 m/s.
For dead end mains and mains exceeding minimum size, proper analysis shall be carried out to
ensure that the required pipe size is adequate to deliver the required water demand.
5.3.5 Pressure
The maximum working pressure at the point of connection shall not be more than 550 kPa (80
psi) and the minimum shall not be less than 140 kPa (20 psi) under fire flow conditions or not
less than 275 kPa (40psi) under normal operating conditions.
Any localized area which has a working pressure in excess of 550 kPa (80 psi), shall be provided
with a pressure-reducing valve on the distribution main or on individual services as required.
5.4 Trunk systems
Transmission pipelines are defined as larger diameter pipelines (typically 400 mm and higher)
which serves to transport large flows of water in the Trinidad & Tobago national grid system.
5.4.1 Velocity
The trunk system must be designed so the velocity shall not exceed 2.4 m/s in the peak hour flow
condition.
5.4.2 Pipe redundancy
Main water trunk systems should allow for some level of redundancy by aiming for smaller double
parallel pipe layouts with adequate valving rather than one hefty pipe diameter.

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5.4.3 Pumping capacity
Booster stations on the Trunk system must be designed in order to allow bidirectional (up flow or
down stream) pumping capacity so as to offer redundancy to the national grid system. The
valving configuration shall allow pumping in both directions and be controlled by the SCADA
systems to accommodate emergency situations.
5.5 System Layout
5.5.1 Grid System
Grid systems shall be designed to ensure flexibility of operation and to minimize the area of the
community required to be shutdown for the repair of the water distribution network. Wherever
possible, the Consultants shall consider the following in the design of the water distribution
system grid:
1. Dead ends shall be minimized by looping all watermains.
2. The use of easements to loop watermains shall be minimized.
3. At the dead end of all watermains, provide a fire hydrant or purge system for washout.
4. Maximum allowable pipe joint deflection shall be 70% of the manufacturer’s specifications.
Pipe barrel bending/deflection will not be permitted.
5. System should facilitate regular flushing of the network.
6. No flushing device is permitted to be directly connected to any stormwater, non potable
water or wastewater main.
5.5.2 Location
In general, the location of watermains shall be off-set 1.5 m from edge of the Right-of-Way
boundary.
5.5.3 Separation from Stormwater and Wastewater Mains
Lateral separation of watermains from stormwater and wastewater mains shall be a minimum of
2.5 m.
Under normal conditions, watermains shall cross above the stormwater and wastewater mains
with a minimum vertical separation of 450 mm to allow for proper bedding and structural
support of the watermain, stormwater and/or wastewater mains. As an alternative, the watermain
may be located under the stormwater and/or wastewater mains with the required minimum
vertical separation.
Where the watermain is located under the stormwater or wastewater main, the required vertical
clearance between the stormwater or wastewater main and the watermain shall be a minimum of
0.6 m. The watermain pipe shall be centred over the crossing so that the joints of the pipe are
equidistant from the stormwater or wastewater main.

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Where the specified vertical separation cannot be achieved, the stormwater and/or wastewater
main shall be constructed of material and with joints that will comply with watermain
construction standards and shall be pressure tested to assure water tightness.
5.5.4 Pipe Depth
Consultants shall allow a minimum of 0.9 m of cover for the watermain.
On open ditch or unimproved roads, a minimum cover shall be provided to allow for future road
improvements or lowering of the road profile. In areas where minimum cover cannot be
achieved, special provision shall be considered to protect pipe from live loading.
5.5.5 Valves
On distribution mains, gate valves shall be provided at every watermain junction but not greater
than 500 m apart and shall be arranged and placed so that no more than 75 units (residential or
commercial/institutional) and 2 hydrants are shut off at any time. On transmission mains over
250 mm diameter, location of the valves should be determined by the Consultants in conjunction
with WASA, but shall not be greater than 1000m. Under normal circumstances on distribution
mains, 3 valves shall be provided on a tee intersection and 4 valves shall be provided on a cross
intersection. Line valves shall be the same size as the watermain up to and including 600 mm
diameter. On 750 mm diameter and larger watermains, one size smaller valve is permissible.
Single line valves up to and including 300 mm shall be buried. Valves and washouts larger than
400 mm shall be installed in adequately designed shallow valve boxes..
Pressure reducing or pressure sustaining valves and chambers are permitted. However, special
designs shall be incorporated to meet the requirements of the water system and of pressure zones.
Resilient seat gate valves are to conform to AWWA C509, up to 300 mm (12 inch) size, with a non-
rising spindle, to be opened by turning in a counter-clockwise direction. All bolts and nuts shall be
304 or 316 stainless steel.
Butterfly valves could be provided on watermains larger than 300 mm diameter and valve
selection must be done in consultation with senior design engineer and utility owner.
5.5.6 Hydrants
Hydrants for fire fighting shall be of a type familiar to and approved by the Trinidad and Tobago
Fire Service (TTFS). The connections are to meet BS336 as 2 x 63.5 mm diameter nozzles and
be installed as per fire service recommendation on all distribution watermains with the following
maximum allowable spacing:
Maximum Allowable Hydrant Spacing
Development Area Maximum Spacing
Residential 250 m
Commercial, Industrial, & High Density Residential 100 m

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All hydrants shall be conform with TTS 622:20XX (in process by TTFS) and AWWA practices.
Laterals shall have a secondary valve, valve box and anchor tee. Spacing of hydrants on all
distribution watermains shall be adjusted to allow for the installation of hydrants at high points
along the watermains and at all dead ends. Hydrants shall be located outside of the ditch line.
Maximum horizontal distance between any point on the building perimeter facing the street and
the hydrant shall be 90 m.
An isolating valve shall be provided on each hydrant lead. This valve shall exist completely in the
sidewalk or entirely out of the sidewalk and conform to the grade of the surrounding area.
5.5.7 Blow Off
A blow-off is not permitted for permanent installations but may be used during the construction
stage for flushing of new watermains. Dead ends on mains 150 mm in diameter or larger shall be
provided with a standard fire hydrant or a two-inch blow-off at the terminal end.
5.6 Pipe Requirements
5.6.1 Pipe Material
All pipes shall have a minimum designed pressure rating of 10 bar and calculation of the strength
and thickness of the pipe shall be made in accordance with AWWA practice or procedures.
Pipes shall be one of the following unless otherwise approved in writing by the Local
Authorities:
Pipe material passing through structural walls should generally be steel.
5.6.2 Pipe specification
See table below for the preferred watermain design range, joint type, service connections and
specifications. The proper selection of water pipe material shall take into consideration the
following:
Working and Surge Pressure Rating;
Internal and External Corrosion Resistance;
Negative Pressure Capacity;
Ease of Installation & Repair;
Availability;
Material Composition e.g. pipes and shall be lead free;
Pipe Rigidity with regards to trench conditions; and
Preferred Design Range for Watermains
Material Main Size Joint Type Services Specification

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Material Main Size Joint Type Services Specification
Ductile Iron (cement
lined)
≤ 1600 mm Tyton > 50 mm
AWWA C151, EN 545 or ISO
2531
Polyvinyl Chloride
(PVC)
< 300 mm
Gasketed Bell &
Spigot
> 100 mm
AWWA C900, AWWA C905,
EN 1452 parts 1 to 5
ISO 4422
Steel Pipe
> 750 mm
Or when pipe
exposed above
surface.
Gasketed Bell &
Spigot or flanged
AWWA C200, EN 10244 or
BS 534
Glass reinforced plastic
(GRP)
450 mm to
3000 mm
Gasketed Bell &
Spigot
AWWA C 950 - ASTM D 3754
5.6.3 Structural Requirements
5.6.3.1 Thrust Restraints
All watermains and thrust restraints shall be designed to withstand the cycling operation of water
mains in T&T in addition to the maximum operating pressure plus the transient pressure to
which it will be subjected. The value of the transient pressure will not be less than the pressure
surge that would be created by immediate stoppage of a water column moving at 0.6 m/s. The
design pressure shall not be less than 10 bar in any case.
All plugs, caps, tees and bends will have approved mechanical thrust restraints based on
applicable AWWA standards. Concrete thrust blocks shall be used with WASA’s approval.
Mechanical thrust restraint devices shall have third party testing certification for water systems.
5.6.3.2 Bedding and Backfill
All buried pipes and conduits entering or exiting a structure shall be fully supported in backfilled
zones by means of a structural bridge or other suitable system to protect against settlement. Bedding
requirements shall be determined by the depth of bury of the pipe, soil type and trench
conditions. As a minimum requirement, watermain shall be laid on 100 mm of sand bedding
conforming with AASHTO M-43 requirement.
5.6.3.3 Above surface Pipe Support
Pipes shall always be supported adequately in accordance with applicable ANSI B31.1, ANSI
B31.9 or other building service pipe codes. If unsupported span is required (for a river crossing per
example), Consultants should address the requirements based on manufacturers recommendations,
considering bending stresses and deflection. Also, the design must address the presence of
concentrated loads (valves, strainers, etc) and changes in direction.

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5.6.4 Tracer Wire
Tracer wire shall be installed on all new installations of PVC and Polyethylene watermain pipes
for locating purposes. A solid 1.5 mm diameter TWU copper wire shall be installed along the top
of the pipe and strapped to the pipe at 6 m intervals. All wires shall be jacketed with a minimum
of 0.76 mm Polyethylene.
The wire shall be installed between each valve and/or at the end of the new PVC watermain.
Joints in the wire between valves are not permitted. At each valve, a loop of wire is to be brought
up inside the valve box to the top of the box.
5.6.5 Water Service Connections
In designing service connections, the Consultants shall comply with the following requirements:
1. All underground water service connections up to and including two-inch sizes shall be extra
Polyethlene PE pipe conforming to ANSI/AWWA C901-96. Connections shall be secure,
durable and watertight.
2. All water services shall be installed at right angles to the watermain.
3. All underground services larger than 50 mm in size shall be ductile iron pipe or PVC pipe.
4. No electrical grounding shall be connected to the water service.
5. Water service connections to any transmission main shall be provided only if no distribution
main is available. A pressure reducing valve shall be installed on the connection if required.
6. All water services shall be provided with a main stop, curb stop and service box at the
property line. Valve box stem extension rods are to be used on water services up to and
including 32 mm.
7. Double service connection is not permitted.
8. The size of water service connections shall be provided as follows:
Minimum Service Connection Size
Type of Development Service Connection Size
Single Family 19 mm diameter
Commercial and Industrial 25 mm diameter or higher
9. Every water service shall be metered in compliance with WASA policies. Design
calculations shall be done in accordance with AWWA M22. No soldered joints or fittings
shall be allowed before the meter or on the bypass valve. The volume of water delivered to
consumers must be measured by meters installed on all direct service connections. Meters
must conform to WASA’s specification and must be installed, operated, calibrated, and
maintained following generally accepted industry standards and information from the
manufacturer. The meter setting shall be as close as possible to the property line at the point
of entrance of the water service connection.

WASA Wastewater and Potable Water Design Requirements

WASA Wastewater and Potable Water Design Requirements

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